Ohio Department of Transportation Central Office 1980 West Broad Street Columbus, OH John Kasich, Governor Jerry Wray, Director

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1 Ohio Department of Transportation Central Office 1980 West Broad Street Columbus, OH John Kasich, Governor Jerry Wray, Director Date: January 19, 2018 To: All Current Holders of the Location and Design Manual, Volume 2 Re: Location and Design Manual, Volume Two Revisions Transmitted herewith are revisions to the Location and Design Manual, Volume 2. The following revisions have been made: Revisions / Additions in Red Glossary of Terms Added definition for Body of Water Added new section Highway Use Permits Design Considerations Added link and reference to the Culvert Management Manual Removed the last paragraph, Updated Durability Design spreadsheet Added guidance for need of a Culvert File Number Added requirement for field paving CMP 60 or greater under submerged conditions Added guidance for use of conduit at MSE walls Added guidance for use of reinforcing steel when field paving and link to the Field Paving of Pipe spreadsheet Added guidance when utilizing a TAF and a link to Form LD Added link to Form LD-50, LD-51, LD A Updated guidance and table , , , , , , , , , Added link to Hydraulic Standard Construction Drawings Updated guidance on approval B Added link to Hydraulic Standard Construction Drawings Added More BMP requirements guidance and examples Replaced second paragraph Updated guidance in last paragraph , H, Added link to Hydraulic Standard Construction Drawings L Updated guidance when using Item 671 Sample Plan Notes W101 Updated guidance when using Item 671 Sample Plan Notes W103 Updated Designer Note Sample Plan Notes Added new notes W104, W105 and W106 The online revisions of the Location and Design Manual, Volume 2 can be found at in PDF format. Technical questions or recommended changes should be directed to Jeff Syar (614) or Matt Cozzoli (614) Respectfully, Jeff Syar, P.E. Office Administrator, Office of Hydraulic Engineering An Equal Opportunity Employer

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3 Notice To ensure proper receipt of future revisions to the manual, please visit the online Design Reference Resource at: This manual is produced by the Office of Hydraulic Engineering. Technical questions, recommended changes, or suggestions should be sent to: Ohio Department of Transportation Attn: Jeffrey Syar, P.E. Administrator, Office of Hydraulic Engineering 1980 West Broad Street Columbus, Ohio (614)

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5 LOCATION AND DESIGN MANUAL VOLUME TWO DRAINAGE DESIGN The OHIO DEPARTMENT of TRANSPORTATION

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7 Table of Contents (Revised January 2018 Preface...i Ohio Counties...iii Glossary of Terms...iv Design Reference Documents...ix 1000 Drainage Design Criteria 1001 Hydraulic Design Criteria Responsibilities Natural Streams Feasibility Study Activities Highway Use Permits Design Considerations Pipe Criteria Introduction General Requirements Conduit Types Hydrology Estimation of Magnitude and Frequency of Floods on Ohio Streams Flood Clearance General Design Year Frequency Highway Encroachments on Flood Plains General Type of Studies Allowable Headwater Design Storm Culvert Headwater Controls Bridge Headwater Control Controls Specific to Flood Insurance Studies (FIS) Pipe Removal Criteria General Asbestos pipe Conduit Design Criteria Corrugated and Spiral Rib Steel and Aluminum Pipes, and Corrugated Steel and Aluminum Pipe Arches Rigid Pipe Thermoplastic Pipe Corrugated Steel and Aluminum Box Culverts and Corrugated Steel Long Span Culverts Precast Reinforced Concrete Box Culverts Precast Reinforced Concrete Three-Sided Flat-Topped Culverts Precast Reinforced Concrete Arch Sections Precast Reinforced Concrete Round Sections Arch or Flat Slab Top Culvert Foundations Bridge Foundations Waterproofing Membrane Precast Reinforced Concrete Flat Slab Tops, Catch Basin Tops, and Inlet Tops Wingwall Design Subsurface Pavement Drainage General Maintenance of Traffic Drainage General Temporary Structures

8 1100 Drainage Design Procedures 1101 Estimating Design Discharge General Procedures Open Water Carriers General Types of Carriers Ditch Design Criteria - Design Traffic Exceeding 2000 ADT Ditch Design Criteria - Design Traffic of 2000 ADT or Less Design Aids for Ditch Flow Analysis Pavement Drainage General Design Frequency Estimating Design Discharge Capacity of Pavement Gutters Pavement Flow Charts Bypass Charts for Continuous Pavement Grades Grate Catch Basins and Curb Opening Inlets in Pavement Sags Bridge Deck Drainage Slotted Drains and Trench Drains Storm Sewers General Design Considerations Layout Procedure Storm Sewer Design Criteria Hydraulic Design Procedure Combined Sanitary Sewer Separation Roadway Culverts General Stream Protection Types of Culvert Flow Design Procedure Use of Nomographs Design Criteria Special Considerations End Treatments General Headwall Types Concrete Apron Rock Channel Protection (RCP) General Culvert RCP Types Bridge RCP Agricultural Drainage Farm Drain Crossings Farm Drain Outlets Longitudinal Sewer Location Under Pavement Under Paved Shoulder Approval Reinforced Concrete Radius Pipe and Box Sections General Sanitary Sewers General Manholes Notice of Intent (NOI) General Routine Maintenance Project

9 Watershed Specific NOI Requirements Erosion Control at Bridge Ends General Corner Cone Temporary Sediment and Erosion Control General Cost Estimate for Temporary Sediment and Erosion Control Post Construction Storm Water Structural Best Management Practices General Project Thresholds for Post-Construction BMP Water Quality and Water Quantity Treatment Water Quality Volume Water Quality Flow Project Type - Redevelopment and New Construction BMP Selection and Submittals BMP Selection BMP Submittals BMP Toolbox Manufactured Systems Vegetation Based BMP Extended Detention Retention Basin Bioretention Cell Infiltration Constructed Wetlands Stream Grade Control Bridge Hydraulics General Hydrology and Hydraulics (H&H) Report APPENDIX A Reproducible Forms APPENDIX B Sample Plan Notes APPENDIX C Drainage Design Aids Appendix C has been removed from the printed manual. Drainage Aids can be found at the OHE webpage.

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11 Preface Purpose This Drainage Design Manual has been prepared as a guide for the hydraulic design of highway drainage facilities. Drainage is one of the essential components of roadway design. Drainage criteria and design outlined in this manual reflects the maximum standard achievable that is based on new project development for traditional design, bid, and build projects. Existing conditions represent the minimum standard, which should always be evaluated against the cost of achieving the maximum standard and the purpose and need of the project. The goal is to make an improvement commensurate with the purpose and need of the project at minimized project costs without negative impacts to safety. Coordinate any proposed deviations from the maximum standard with the Department prior to incorporation into the design. Drainage facilities for most roadway projects account for approximately 25% of the total construction cost of the project. This cost justifies a careful and scientific hydraulic analysis. Application Design drainage facilities following the recommended design procedures noted in this manual to minimize the following: Damage of private property due to flooding Inconvenience to the motorist during moderate to heavy rainfall Disturbance to the environment Numerous charts have been prepared and are included in the Drainage Design Aids Section of this manual to assist the Drainage Design Engineer with the hydraulic analysis. Other design charts are available in Hydraulic Engineering Circulars and Hydraulic Design Series prepared by the Federal Highway Administration. Reference is made to those charts as required. This manual is neither a textbook nor a substitute for engineering knowledge, experience, or judgment. It is intended to provide uniform procedures for implementing drainage design decisions and assure quality and continuity in drainage of highways in Ohio. Although the manual is considered a primary source of reference by personnel involved in drainage design in Ohio, it must be recognized that the practices suggested may be inappropriate for some projects because of fiscal limitations or other justifiable reasons. Consideration must also be given to justifiable hydraulic design standards adopted by city, county, or other local governments when designing facilities under their jurisdiction. Preparation The Drainage Design Manual has been developed by the Office of Hydraulic Engineering (OHE). Errors or omissions should be reported to the Administrator, Office of Hydraulic Engineering, Ohio Department of Transportation, 1980 W. Broad Street, Columbus, Ohio Format and Revisions Updating the manual is intended to be a continuous process. Revisions will be issued periodically by OHE and will be available on the Design Reference Resource Center (DRRC) webpage: All revisions are shown in red text, and each page has the latest date shown in the bottom corner. January 2018 i

12 Ohio Department of Transportation Williams Defiance Paulding Van Wert Mercer 7 Darke Preble Butler 8 Hamilton 1 Allen Auglaize Sidney Miami Montgomery Fulton Shelby Henry Putnam Warren Lebanon Clermont Lima Lucas Clinton 2 Bowling Green Wood Hancock Hardin Logan Champaign Clark Greene Brown Highland 6 Districts Ottawa Wyandot Union Madison Fayette Adams Sandusky Seneca Marion 3 Ashland Crawford Richland Delaware Pickaway Ross Delaware Franklin Columbus Athens 9 Vinton 10 Chillicothe Pike Scioto Erie Morrow Huron Fairfield Knox Licking Hocking Jackson Jacksontown Lorain Ashland Perry Gallia Medina Garfield Hts. Cuyahoga Wayne Holmes Coshocton Tuscarawas Geauga 12 4 Guernsey 5 11 Muskingum Meigs Morgan Akron Summit Noble Lake Portage Stark New Phil. Washington Marietta Carroll Harrison Ashtabula Trumbull Mahoning Columbiana Belmont Monroe Jefferson District N. McCullough St. Lima, OH fax: District East Poe Rd. Bowling Green, OH fax: District Clark Ave. Ashland, OH or fax: District S. Arlington Rd. Akron, OH fax: District Jacksontown Rd. Jacksontown, OH fax: District East William St. Delaware, OH fax: Lawrence Central Office 1980 W. Broad Street Columbus, OH fax: ODOT Web Site: District St. Marys Ave. Sidney, OH or fax: District S. State Route 741 Lebanon, OH or fax: District Eastern Ave. PO Box 467 Chillicothe, OH or fax: District Muskingum Dr. PO Box 658 Marietta, OH or fax: District Reiser Ave. New Philadelphia, OH fax: District Transportation Blvd. Garfield Heights, OH or fax:

13 Ohio Counties County Code District Adams ADA 9 Allen ALL 1 Ashland ASD 3 Ashtabula ATB 4 Athens ATH 10 Auglaize AUG 7 Belmont BEL 11 Brown BRO 9 Butler BUT 8 Carroll CAR 11 Champaign CHP 7 Clark CLA 7 Clermont CLE 8 Clinton CLI 8 Columbiana COL 11 Coshocton COS 5 Crawford CRA 3 Cuyahoga CUY 12 Darke DAR 7 Defiance DEF 1 Delaware DEL 6 Erie ERI 3 Fairfield FAI 5 Fayette FAY 6 Franklin FRA 6 Fulton FUL 2 Gallia GAL 10 Geauga GEA 12 Greene GRE 8 Guernsey GUE 5 Hamilton HAM 8 Hancock HAN 1 Hardin HAR 1 Harrison HAS 11 Henry HEN 2 Highland HIG 9 Hocking HOC 10 Holmes HOL 11 Huron HUR 3 Jackson JAC 9 Jefferson JEF 11 Knox KNO 5 Lake LAK 12 Lawrence LAW 9 County Code District Licking LIC 5 Logan LOG 7 Lorain LOR 3 Lucas LUC 2 Madison MAD 6 Mahoning MAH 4 Marion MAR 6 Medina MED 3 Meigs MEG 10 Mercer MER 7 Miami MIA 7 Monroe MOE 10 Montgomery MOT 7 Morgan MRG 10 Morrow MRW 6 Muskingum MUS 5 Noble NOB 10 Ottawa OTT 2 Paulding PAU 1 Perry PER 5 Pickaway PIC 6 Pike PIK 9 Portage POR 4 Preble PRE 8 Putnam PUT\ 1 Richland RIC 3 Ross ROS 9 Sandusky SAN 2 Scioto SCI 9 Seneca SEN 2 Shelby SHE 7 Stark STA 4 Summit SUM 4 Trumbull TRU 4 Tuscarawas TUS 11 Union UNI 6 Van Wert VAN 1 Vinton VIN 10 Warren WAR 8 Washington WAS 10 Wayne WAY 3 Williams WIL 2 Wood WOO 2 Wyandot WAY 1 January 2018 iii

14 Glossary of Terms Aggregate Drain A trench filled with granular material extending laterally from the pavement base or subbase layer to an outlet on the roadway foreslope with the intent of draining surface and/or ground water away from the pavement base and/or subbase. Anti-seep Collar Device that prevents the flow of water through the surrounding soil around a conduit that is used as an outlet for an infiltration, retention, or detention basin. Apron Paving at a pipe inlet or outlet, or upstream of a catch basin, constructed along the channel bottom to prevent scour. Backwater Analysis The determination of water surface profiles measured at specific locations upstream from a constriction causing an increased flow depth upstream. Bankfull Discharge The flow or stage of a stream corresponding to the highest level of active deposition. It is the discharge that, on the average, fills a main channel to the point of overflowing. For simplicity, it is generally considered to be approximately the 2 year discharge. Body of Water A body of water is any significant accumulation of water, generally on a planet's surface. The term most often refers to large rivers, and lakes, but it includes smaller pools of water such as ponds, or wetlands. Bridge Structure that has a span greater than or equal to 10 feet as measured in a parallel direction to the roadway centerline. Camber A slight convex curve constructed into the bottom of a pipe to overcome anticipated settlement problems. Cast-in-place Structure A concrete drainage structure which is placed in forms and cured at its final location. Precast beams on cast-in-place foundations are considered cast-in-place structures. Catch Basin A structure for intercepting flow from a gutter or ditch and discharging the water through a conduit. Coefficient of Runoff (C) A value, varying with the ground and ground cover, which is used in the Rational formula to determine the amount of a rainfall which is directed to streams and not absorbed into the ground. Conduit A closed structure such as a pipe that has a span less than 10 feet as measured in a parallel direction to the roadway centerline. Corner Bearing Pressure The pressure generated at the corners of pipe arch structures. Culvert A structure which is typically designed hydraulically to take advantage of submergence at the inlet to increase hydraulic capacity. A structure used to convey surface runoff through embankments. A structure, as distinguished from a bridge, which is usually covered with embankment and is composed of structural material around the entire perimeter, although some are supported on spread footings with the stream bed serving as the bottom of the culvert. Cutoff Wall A wall that extends downward from the end of a structure to below the expected scour depth, or to a scour-resistant material. Design Discharge (Q) The peak rate of flow for which a drainage facility is designed. Usually given in cubic feet per second (cfs). Design Service Life The average usable life of a pipe or structure. Certain drainage situations require a 50-year life, more stringent situations require a 75-year design life. iv January 2018

15 Design Storm A given rainfall amount, areal distribution, and a time distribution, used to estimate runoff. The rainfall amount is either a given frequency (25-year, 50-year, etc.) or a specific large value. Detention Basin A structure that holds water for a short period of time before releasing it to the natural water course. Diversion Dike An embankment to control or to deflect water away from a soil bank. Drainage Area The area contributing discharge to a stream at a given point. Drop-down Entrance (Drop inlet) A type of inlet which conveys the water from a higher elevation to a lower elevation smoothly without a free fall at the inlet. Elliptical Pipe Pipe which is manufactured with a span greater than rise to be utilized in shallow cover situations. Ephemeral Stream A stream or reach of stream that does not flow for parts of the year. As used here, the term includes intermittent streams with flow less than perennial. It is located above the water table year-round. Ground water is not a source of water supply. Feasible Term used to define BMP practicability. BMP shall be: technically feasible, implemented within the procured highway right-of-way, safe for the traveling public and ODOT maintenance personnel, cost effective as compared to the benefit, and will be legal at the State, Federal, and Local levels. FEMA Federal Emergency Management Agency. Flood Fringe The portion of the floodplain outside of the floodway. Flood Hazard Evaluation The act of determining if flood levels within a watercourse for a 100-year flood, or other recurrence interval floods have a significantly increased detrimental impact on upstream property. Flood Insurance Rate Map (FIRM) The official map of a community on which FEMA has delineated both the special hazard areas and the risk premium zones applicable to the community. Flood Insurance Study A book with information regarding flooding in a community that is developed in conjunction with the FIRM. It discusses the engineering methods used to develop the FIRMs. Flood Plain Culverts Relief culverts that are placed in addition to a bankfull culvert at a higher elevation across the flood plain to allow multiple outlets for floodwaters. Flood Plain Study A more extensive analysis of the effects of flood levels on upstream property than the Flood Hazard Evaluation. This analysis is to be used when upstream properties appear to have been subjected to a significantly increased detrimental effect from the flood flows. Floodway The portion of the floodplain which is effective in carrying flow, within which this carrying capacity must be preserved and where the flood hazard is generally highest. Flowline see Thalweg Forebay Depressed area that offers pretreatment of sediment laden storm water prior to a retention, detention, or infiltration basin. Friction Slope The slope of the energy grade line. Granular Material A term relating to the uniform size of grains or crystals in rock, larger than sand or pea gravel. January 2018 v

16 Grate A type of screen made from sets of bars used to allow the interception of flow, and also to cover an area for pedestrian or vehicular traffic. Headwall The structural appurtenance placed at the open end of a pipe to control an adjacent highway embankment and protect the pipe end from undercutting. Headwater That depth of water impounded upstream of a culvert due to the influence of the culvert constriction, friction, and configuration. Highest Known Water Elevation The highest known flood water in record. Hydraulic Grade Line A line coinciding with the level of flowing water in an open channel. In a closed conduit operating under pressure, a line representing the distance water would rise in a pitot tube at any point along a pipe. The hydraulic grade line is equal to the pressure head (P/γ) along the pipe. Hydraulic Gradient The slope of the hydraulic grade line for a storm sewer or culvert. Idealized Channel Geometry Physical, geometric, and hydraulic characteristics of a channel determined from empirical relationships. Impervious Surface Hardened pavement surface. Infiltration Rate The rate at which water penetrates the surface of the soil at any given instant. The rate can be limited by the infiltration capacity of the soil or the rate at which water is applied. Inlet A structure for capturing concentrated surface flow. May be located along the roadway, in a gutter, in the highway median, or in the field. Inlet Control The situation where the culvert hydraulic performance is controlled by the entrance geometry only. Intermittent Stream A stream that is dry for part of the year, ordinarily more than 3 months. Manhole A structure by which one may access a closed drainage system. MS4 Phase II Regulated Area Area that has been designated by the Ohio EPA that requires a storm water management plan to discharge storm water. Multiple Cell Culvert A culvert with more than one barrel. New Development Project Projects that change the land use of a site from undeveloped to developed characteristics. Normal Water Elevation The water elevation in a stream which has not been affected by a recent heavy rain runoff. The water level which could be found in the stream most of the year. This elevation will be lower than the ordinary high water. Ordinary High Water The line on the shore established by the fluctuation of water and indicated by physical characteristics such as: a clear natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, or other appropriate means that consider the characteristics of the surrounding areas. This elevation is lower than the highest known water. Outlet Control The situation where the culvert hydraulic performance is determined by the controlling water surface elevation at the outlet, the slope, length and roughness of the culvert barrel, as well as the entrance geometry. Overland Flow Water which travels over a surface and reaches a stream. vi January 2018

17 Perennial Stream A stream that flows continuously for all or most of the year. The water table is located above the stream bed for most of the year. Permeability The quality of the soil that enables water to move downward through the soil profile. It is measured in units of inches per hour. ph The reciprocal of the negative logarithm of the Hydrogen ion concentration. Neutral water has a ph value of 7. A measure of the acidity of a substance, if less than 7; alkalinity if greater than 7. Pipe Arch Pipe which is manufactured with a span greater than rise (semicircular crown, small-radius corners, and large radius invert) to be utilized in shallow cover situations. Pipe Underdrain A longitudinal subsurface drainage system composed of a perforated pipe at the bottom of a narrow trench filled with permeable material and lined with a geotextile in erodible soils, with the intent of draining surface and/or ground waters away from the pavement base and/or subbase. Porosity The volume of voids divided by the total volume and multiplied by 100. Prefabricated Edge Drain A longitudinal underdrain system utilizing a narrow trench and a vertically elongated, perforated water carrier with the intent of draining surface and/or ground water away from the pavement base and/or subbase. Prefabricated Structure Any drainage structure which is manufactured off site and transported to the location of intended use. It may be of various materials, including concrete, clay, metal, thermoplastics, etc. It may be of various shapes including circular, elliptical, rectangular, arched, etc. Premium Joints Watertight joints. Pretreatment Preliminary filtering of sediment laden storm water prior to secondary treatment through a structural best management practice. Rainfall Intensity (i) The amount of rainfall occurring in a unit of time, normally given in inches per hour. Reference Reach A length of channel with stable geometric, physical, and hydraulic characteristics. A representation of the desired outcome of a restored channel. Retention Basin A structure that holds water on a permanent basis. Roughness Coefficient (n) The measure of texture on the surface of channels and conduits. Usually represented by the n-value coefficient used in Manning s open channel flow equation. Runoff That part of the precipitation which runs off the surface of a drainage area after all abstractions are accounted for. Sanitary Sewer A conduit or pipe system which carries household and/or industrial wastes. Sanitary sewers do not convey storm water. Sediment Basin A basin or tank in which stormwater containing settleable solids is retained, to remove by gravity or filtration a part of the suspended matter. Sediment Dam A dam that is designed to allow suspended sediment to settle out of flowing water in a controlled area. Short-circuiting The act of storm water bypassing the intended route. Soil Bioengineering The use of live and dead plant materials, in combination with natural and synthetic support materials, for slope stabilization, erosion reduction, and vegetative establishment. January 2018 vii

18 Spring Line The locus of the horizontal extremities of a transverse section of a conduit. Step Backwater or Standard Step Method An iterative use of the energy equation for determining the water surface profile of an open channel. Storm Sewer A conduit or pipe drainage system that conveys storm water, subsurface water, condensate, or similar discharge, but not household or industrial wastes. Thalweg The lowest bed elevation in a natural channel cross section. Also used in reference to the profile line extending down a channel along the lowest bed elevation. Tailwater The depth of flow in the stream directly downstream of a drainage facility, measured from the invert at the culvert outlet. Often calculated for the discharge flowing in the natural stream without the highway constriction. Term is usually used in culvert design and is the depth measured from the downstream flow line of the culvert to the water surface. Time of Concentration (t c ) Time required for water to flow from the most distant point on a drainage area to the measurement or collection point. TMDL (total maximum daily load) Regulated Stream An Impaired water body as defined by the Ohio EPA that can still meet water quality standards if the daily maximum pollutant load is regulated. Two Stage Channel A channel that contains a cross sectional area for low and high discharges. Water of The United States Water bodies subject to Army Corps of Engineers jurisdiction through Section 404 of the Clean Water Act. They include all interstate waters such as lakes, rivers, streams (including intermittent streams) and wetlands. Ephemeral streams are included if they have a clearly defined channel. viii January 2018

19 Design Reference Documents Highway Hydrology (FHWA Hydraulic Design Series No. 2) Design Charts for Open Channel Flow (FHWA Hydraulic Design Series No. 3) Hydraulic Design of Highway Culverts (FHWA Hydraulic Design Series No. 5) River Engineering For Highway Encroachments (FHWA Hydraulic Series No. 6) Design of Stable Channels with Flexible Linings (Federal Highway Engineering Circular No. 15) Evaluating Scour at Bridges (FHWA Hydraulic Engineering Circular No. 18) Stream Stability at Highway Structures (FHWA Hydraulic Engineering Circular No. 20) Urban Drainage Design Manual Second Edition (FHWA Hydraulic Engineering Circular No. 22) Bridge Scour and Stream Instability Countermeasures Experience, Selection, and Design Guidance (FHWA Hydraulic Engineering Circular No. 23) Estimation of Peak-Frequency Relations, Flood Hydrographs, and Volume - Duration - Frequency Relations of Ungaged Small Urban Streams in Ohio (USGS Open-File Report ) Estimation of Flood Volumes and Simulation of Flood Hydrographs for Ungaged Small Rural Streams in Ohio (USGS Water Resources Investigations Report ) Culvert Durability Study (ODOT/L&D/82-1) Assessment of ODOT s Conduit Service Life Prediction Methodology (FHWA/OH-2016/16) Internal Energy Dissipators for Culverts (FHWA/OH-84/007) Standard Construction Drawings (ODOT) Construction and Material Specifications Handbook (ODOT) Rainwater and Land Development, Ohio s Standards for Stormwater Management Land Development and Urban Stream Protection (Third Edition, 2006). Stream Corridor Restoration: Principles, Practices and Processes (United States Department of Agriculture), October 1998 Additional design resources can be found at the FHWA website at: Bankfull Characteristics of Ohio Streams and Their Relation to Peak Streamflows (Scientific Investigations Report ) A Streamflow Statistics (StreamStats) Web Application for Ohio (Scientific Investigations Report FHWA Ultra Urban BMP webpage. USEPA National Pollutant Discharge webpage Urban Runoff Quality Management, WEF Manual of Practice No. 23, 1998, published jointly by the WEF and ASCE. Ohio Environmental Protection Agency January 2018 ix

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21 Table of Contents (Revised January 2018) 1000 Drainage Design Criteria 1001 Hydraulic Design Criteria Responsibilities Natural Streams Feasibility Study Activities Highway Use Permits Design Considerations Pipe Criteria Introduction Deviation by ODOT Districts Deviation by Local General Requirements Pipe Materials Conduit Durability and Service Life Outlet Velocity Control Special Shapes Structure File Number/Culvert File Number Conduit Types Type A Conduits Type B Conduits Type C Conduits Type D Conduits Type E Conduits Type F Conduits Culvert Rehabilitation Hydrology Estimation of Magnitude and Frequency of Floods on Ohio Streams General Alternate Discharge Sources for Bridges Limitations Flood Clearance General Design Year Frequency Highway Encroachments on Flood Plains General Flood Data and Flood Insurance Studies (FIS) Proposed Construction in FEMA Zones Exceptions ODOT Self-Permit Process Type of Studies Hazard Evaluation for Watercourses without a Defined FEMA SFHA Detailed Study Allowable Headwater Design Storm Culvert Headwater Controls Design Storm Controls Check Storm Controls Limitations Controls Specific to Flood Plain Insurance Studies Bridge Headwater Control Controls Specific to Flood Insurance Studies (FIS) Pipe Removal Criteria General Asbestos pipe Conduit Design Criteria

22 Corrugated and Spiral Rib Steel and Aluminum Pipes, and Corrugated Steel and Aluminum Pipe Arches Material Durability Designation and Thickness Cambered Flow Line Height of Cover Foundation Reports Rigid Pipe General Height of Cover Thermoplastic Pipe Height of Cover Corrugated Steel and Aluminum Box Culverts and Corrugated Steel Long Span Culverts Designation and Thickness Height of Cover Foundation Reports Precast Reinforced Concrete Box Culverts Designation Height of Cover Precast Reinforced Concrete Three-Sided Flat-Topped Culverts Designation Height of Cover Foundation Reports Precast Reinforced Concrete Arch Sections Designation Height of Cover Foundation Reports Precast Reinforced Concrete Round Sections Designation Height of Cover Foundation Reports Arch or Flat Slab Top Culvert Foundations Bridge Foundations Waterproofing Membrane Precast Reinforced Concrete Flat Slab Tops, Catch Basin Tops, and Inlet Tops Wingwall Design Subsurface Pavement Drainage General Maintenance of Traffic Drainage General Temporary Structures

23 1000 Drainage Design Criteria 1001 Hydraulic Design Criteria Responsibilities The Office of Hydraulic Engineering (OHE) is responsible for the hydraulic design standards for all surface drainage systems and bridge structures owned and maintained by the Department. Further responsibility includes: conduit durability, culvert inspection and inventory, post construction storm water best management practices, and the Department s Municipal Separate Storm Sewer System (MS4) program Natural Streams Channel designs and channel relocations of all natural streams passing through a proposed highway facility will be the responsibility of the owner. All other channel designs and channel relocations of natural streams are the responsibility of OHE Feasibility Study Activities Encroachments on floodplains for transportation projects are governed in part by the Code of Federal Regulations (CFR), Part 650, Subpart A. The Project Development Process (PDP) and hydraulic design criteria function to satisfy the requirements of this regulation Highway Use Permits Design Considerations When any owner or developer of land adjacent to highway R/W proposes to route site drainage into the highway drainage system, the following shall apply and be the responsibility of the owner/developer: 1. No diversion of flow to the highway is permitted. 2. Maintain flow peaks from areas contributing to the highway drainage system at pre-development levels. Provide onsite detention when required to meet this condition. 3. Prior to the start of construction, submit drainage plans and calculations for review to the Department of Transportation Pipe Criteria Introduction The Departments Pipe Criteria governs the determination of the size and type of pipe specified or permitted for the various items of highway drainage financed totally or in part with state or federal funds. Deviations from this Pipe Criteria concerning type of pipe or pipe placement must be based on sound engineering judgment and/or life cycle cost analysis. Deviations involving the specification of only one type of pipe material where special conditions prevail must include sound engineering judgment such as: Excessive cover for a rigid pipe. Where a larger corrugated pipe would require a higher pavement grade to satisfy minimum cover requirements or require more cells than a rigid alternate. Where a metal pipe arch would be required as an alternate to a round rigid pipe. The outfall velocity would require an energy dissipater. Site conditions prevented the existing conduit material to meet design service life. Verification that the existing conduit material had been correctly designed to ODOT durability design needs to be documented. If a structure type study is performed and the cost analysis indicates a lower cost. The use of a single material type is subject to the approval of OHE. January

24 Drainage Design Criteria Deviation by ODOT Districts ODOT Districts may submit a written request for deviation from this Pipe Criteria. Include documentation that justifies the deviation and the completed Drainage Criteria form (see Appendix A). Submit the documentation to the Administrator of OHE Deviation by Local Proposed deviations from this Pipe Standard and/or construction specifications by local political subdivisions or agencies will be considered for all portions of the project that are maintained by the political subdivision or agency. ODOT Districts may permit a deviation from this Pipe Standard provided the local political subdivision or agency agrees to fund any additional costs inferred due to the conduit material selection. The deviation requires alternate bid items, per Section of L&D Volume 3, to determine the additional costs. The alternatives include ODOT s Pipe Standard/construction methods and the local s material selection/construction methods. Add additional notes or details as required by the local General Requirements Pipe Materials The type of pipe materials listed under the various conduit types in Section of the Construction and Material Specifications are considered equal within their size, structural and material durability limitations. Refer to the Culvert Management Manual (CMM) for pictures of the various pipe materials. The Culvert Management Manual can be found at: Management.aspx Conduit Durability and Service Life The ph of the normal stream flow and the presence of abrasive flow conditions are factors that determine the material durability and service life for culverts and storm sewers. Measure the ph of the normal stream flow in the field using a calibrated ph meter capable of measuring to a tenth. Field measurement of ph is required. Use Figures and if flow is not present in the conduit. Determine if the streambed material is abrasive by observation. An abrasive condition is defined as the presence of granular material with a stream gradient or flow sufficient to cause movement of the material. Granular material is defined as material the size of pea gravel or larger. Assign an abrasion level to the stream on a scale of 1-6 according to the below descriptions. Use Level 1 if non-abrasive. Level 1: Bedloads of silts and clays or clean water with virtually no abrasive bed load. Non- Abrasive Material Level 2: Moderate bed loads of sand or gravel. Level 3: Moderate bed load volumes of sand, gravels, and small cobbles. Level 4: Moderate bed load volumes of angular sands, gravels, and cobbles/rocks Level 5: Moderate bed load volumes of angular sands and gravel or rock. Level 6: Moderate bed load volumes of angular sands and gravel or rock OR Heavy bed load volumes of angular sands and gravel or rock. Perform durability design using the OHE Durability Design spreadsheet. The spreadsheet can be obtained from the OHE website at the following location: January 2018

25 Drainage Design Criteria The tabulations in the Durability Design spreadsheet are based on the Assessment of ODOT s Conduit Service Life Prediction Methodology research report (FHWA/OH-2016/16). Additional abrasion level information and abrasion level site photos are available in the reference data tab of the Durability Design spreadsheet. Ensure the ph and abrasiveness determination is included in the plans in accordance to L&D, Volume Outlet Velocity Control When permissible pipe alternates have different velocity characteristics, the design specified for erosion control will satisfy the most severe velocity condition of the permissible alternates. In this case, erosion control refers to controls placed in the stream channel at the outlet end of the pipe such as rock channel protection, and does not refer to energy dissipaters. Where the calculated culvert outlet velocity exceeds 20 feet per second or 15 feet per second in areas of poor soil such as fine sand or sandy silt, roughness elements (protruding concrete rings inside the pipe) may be specified at the outlet end of the alternates to reduce the velocity below the maximum allowable. The design of internal energy dissipator ring chambers is provided in report FHWA/OH-84/007 Internal Energy Dissipators for Culverts. This report and ring chamber details can be obtained from OHE. Where the outlet velocity for a corrugated pipe is less than 20 feet per second while the outlet velocity for a smooth pipe requires a ring chamber, the corrugated pipe may be specified exclusively Special Shapes Special shaped conduits (elliptical concrete, corrugated metal arch or pipe arch, or prefabricated box or three-sided structures) are generally limited for use under shallow cover installations or extremely low or restrictive headwater control otherwise requiring multiple circular conduits to satisfy allowable headwater conditions. Generally elliptical concrete and corrugated metal pipe arch of the required size to satisfy hydraulic conditions are to be shown on the plan. Special shaped conduits may be provided to conform to the cross-sectional geometry of sensitive streams identified in the environmental documentation. Where corrugated metal and structural plate pipe arches are specified or permitted, a foundation investigation shall be submitted as required by Section Structure File Number/Culvert File Number Structures having an opening measured along the centerline of roadways of 10 or greater require a Structure File Number (SFN). Multiple openings where the extreme ends of the openings are 10 or greater also require a SFN, where the clear distance between opening is less than half of the smaller contiguous opening. Culverts (Type A) and Storm Sewers (Type B) having an opening measured along the centerline of roadway 12 inches or greater but less than 120 inches require a Culvert File Number (CFN). A new CFN is generated by the Culvert Collector application or the Culvert Web application. Reference the latest Culvert Management Manual (CMM) on how to obtain a CFN. Ensure the CFN is included in the plans in accordance to L&D, Volume 3. The Culvert Management Manual can be found at: Management.aspx January

26 Drainage Design Criteria Conduit Types Type A Conduits Type A conduits shall be designated for soil-tight, sealed-joint, open-ended cross drains under pavements and paved shoulders. The minimum size culvert (or cross drain) to be specified shall be based on the roadway type and depth of fill from the flowline to roadway surface. The minimum required round (or equivalent deformed) pipe sizes are listed in Figure For culverts under freeways or high fills (16 feet), the size shall be increased one pipe size over the required size to allow for future repair. Ensure the pipe is only upsized once. All hydraulically adequate pipe alternates which provide the required service life shall be shown on the plans and listed in the pertinent pay item. In the applicable size ranges, alternates should include, vitrified clay, concrete, plastic, corrugated steel, and corrugated aluminum. For corrugated metal pipe, the corrugation profile which requires the thinnest metal shall be listed. Where durability requires increased thicknesses of the corrugated steel alternate, the 1-inch corrugation profile should be specified for pipe diameters over 48 inches. For the steel corrugation profile specified, all combinations of thickness and protection providing the required service life shall be specified. If the alternates listed in the plan are different sizes, show the pipe length associated with the smallest pipe size. Provide concrete field paving on corrugated metal conduits 60 or larger where the invert is always submerged due to tail water conditions from a body of water. When extending existing Type A conduits, ensure the extensions match the existing material in kind. Furnish all Type A conduits under State and Federal routes with a minimum service life of 50 years. Use a service life of 75 years at sites that have one of the following characteristics: 1. Fill Height 16 feet (measured from flowline to finished grade) 2. Freeways 3. Structures defined as a Bridge Type B Conduits Type B conduits shall be designated for soil-tight, sealed joint sewers under pavements, paved shoulders, and commercial or industrial drives. In areas with highly erodible soils (e.g., fine sands or silts), premium joints shall be provided. Additional protection (epoxy coating as per for concrete pipe and polymer coating per for asphalt paved corrugated steel pipe) shall be provided for storm sewers carrying corrosive flow. For conduit placed through MSE walls or in the fill of MSE walls refer to the Bridge Design Manual (BDM) Section The design service life for all Type B conduit is 75 years. Use a minimum abrasion level equal to 2 when performing durability design Type C Conduits Type C conduits shall be designated for soil-tight, sealed joint sewers not under pavements, paved shoulders, or commercial or industrial drives. In areas with highly erodible soils (e.g., fine sands or silts), premium joints shall be provided January 2018

27 Drainage Design Criteria Additional protection (epoxy coating as per for concrete pipe and polymer coating per for asphalt paved corrugated steel pipe) shall be provided for storm sewers carrying corrosive flow. The design service life for all Type C conduit is 75 years Type D Conduits Type D conduits shall be designated for pipes under driveways and bikeways. The minimum size required is 12 inches. For sizes 24 inches and larger, it will be necessary to submit calculations and specify pipe sizing required to satisfy the hydraulic controls. Such analyses shall be submitted with the Drainage Review plans. The design frequency used to analyze the hydraulic performance of the Type D conduit is the same as that used for the flow capacity of the connected ditch or channel and the headwater for that frequency shall not exceed a point 1 foot below the edge of the pavement. If potential exists for the drive pipe headwater to encroach on the adjacent roadway, the drive pipe shall be sized utilizing a design frequency as per Generally, the pipe alternates listed in of the Construction and Material Specifications are applicable, except that equal size corrugated pipe will provide satisfactory alternates for sizes smaller than 24 inches. If the control is critical, a hydraulic analysis will be required to determine the proper size of pipe alternates. Ensure drive pipes under commercial or industrial drives are designed for material durability as per Additional protection for residential and field drives may be specified if conditions warrant Type E Conduits Type E conduits shall be designated for farm drain headers inside or outside of the right-of-way lines. Headers are ordinarily provided to intercept small, closely spaced lines in a tiled field thereby precluding the need for numerous field tile outlets through the backslope of the highway ditch Type F Conduits Type F conduits shall be designated where a butt joint or a short length jointed pipe would be undesirable as noted below: A. For the steep portion of a median outlet under an embankment slope 4:1 or steeper, including any necessary pipe bends. B. For the outlets of underdrains or farm drains through the slope or connecting to a drainage structure. When used for underdrain outlets, the following pay item description shall be used: Item 611 " Conduit, Type F for Underdrain Outlets. Provide 10 feet of conduit at each outlet into a drainage structure. C. For farm drains larger than 12 inches that outlet through slopes flatter than 4:1, provide a 20 foot length of Type F Conduit with an animal guard at the outlet. D. For pipe underdrains that span the trench of a lower conduit, unless the crossing is more than 12 inches above the granular backfill of the lower conduit, provide a minimum length of 10 feet of Type F Conduit. Type F conduits may be used beyond the paved shoulder to eliminate a ditch in front of a yard where such ditch elimination can be justified. When required by hydraulic analysis, all proper sized alternates shall be specified Culvert Rehabilitation A range of material applications and solutions are available for culvert rehabilitation. These solutions are used to extend the service life of existing conduits by adding durability or in some cases structural strength. The following specifications or methods are available: CMS Field Paving of Existing Pipe January

28 Drainage Design Criteria Supplemental Specification 833 Conduit Renewal Using Spray Applied Structural Liner Supplemental Specification 834 Conduit Renewal Using Resin Based Liner Supplemental Specification 837 Liner Pipe (various material) Supplemental Specification 841 Conduit Renewal Using Spiral Wound Liner Plan Note Cured In Place Pipe (CIPP) Field paving of existing conduits has been a solution to add durability to conduits for many years. This solution is a cost effective way to add many years of service life to an existing conduit provided the culvert has good structural shape and is structurally sound (i.e.: not moving). This solution should always be evaluated first. The amount of material loss in the invert will determine if the addition of reinforcing will be necessary. Perform a structural analysis of the existing conduit to determine if the addition of rebar to the field paving will be necessary. Perform the analysis using the OHE Field Paving of Pipe spreadsheet. The Field Paving of Pipe spreadsheet can be found at: aspx The Field Paving of Pipe spreadsheet is based on the Structural Benefits of Concrete Field Paving of Steel Culvert Inverts research report (FHWA/OH-2017/21). Supplemental Specification 833 Conduit Renewal Using Spray Applied Structural Liner is a solution that provides structural rehabilitation to existing conduits via a spray application. The interior of the conduit is spray lined with a factory blended cementitious geopolymer or resin based material. Supplemental Specification 834 Conduit Renewal Using Resin Based Liner is a solution that adds durability by placing a resin based material on the interior of the existing conduit via a spray application. This solution will add service life to an existing conduit. Supplemental Specification 837- Liner Pipe offers a solution that lines an existing conduit with another conduit. This specification requires the slip-lined conduit to be grouted in-place and in some cases would be considered a structural solution if the slip-lining material is designed accordingly. Supplemental Specification 938 is an additional material option utilized by Supplemental Specification 837. Ensure all available Liner Pipe materials in Supplemental Specification 837 are shown in the plans if they satisfy the hydraulic conditions. Ensure the hydraulic calculations are evaluated for the alternative slip-line materials. Submit all Liner Pipe projects to OHE for review and approval if one material alternative is specified in the plans. Furnish a cost analysis verifying the use of a single material option. Supplemental Specification 841 Conduit Renewal Using Spiral Wound Liner is a unique solution that may be used to line various shaped conduits such as: Round, Elliptical, Box, or Pipe Arch. This solution custom manufactures the conduit on site from polyvinyl chloride material with either a special machine or by manual labor. The manufactured conduit is placed into the existing conduit and the void is filled with grout. This solution adds durability to the existing host conduit. Use of this solution requires approval from OHE. The culvert rehabilitation method shall be designed to match existing headwater conditions. Appropriate erosion control measures shall be designed for increased outlet velocities. If the proposed design does not meet the existing headwater conditions or the outside diameter constraint described above, contact OHE for approval. Plan Note Cured in Place Pipe (CIPP) offers a structural rehabilitation solution that lines an existing conduit with a form fitting liner. The resin saturated liner is inserted into the conduit. Once in place the liner is expanded and cured to mold itself to the host conduit. Ensure adequate hydraulic capacity is maintained January 2018

29 Drainage Design Criteria While CIPP can be used for culvert rehabilitation other techniques in this section should be explored first. CIPP is best suited for closed systems such as storm sewers. Additional information and guidance for culvert rehabilitation can be found at: Hydrology Estimation of Magnitude and Frequency of Floods on Ohio Streams General USGS Water Resources Investigations Report Techniques for Estimating Flood-Peak Discharges of Rural Unregulated Stream in Ohio was developed cooperatively by the United States Geological Survey and the State of Ohio. This bulletin is an update of Bulletin 32 (1959), Bulletin 43 (1969), and Bulletin 45 (1977). This report provides the latest hydrologic information for determining the magnitude and frequency of floods for rural streams in Ohio. USGS Report StreamStats is a USGS web based application for estimating stream flow statistics and basin characteristics on unregulated streams. Use StreamStats or the techniques presented in Report to determine the design peak discharge for hydraulic structures designated by or for ODOT. When applying this technique, the tributary with the largest contributing drainage area, not the longest reach, should be considered. USGS Water Resources Investigation Report Estimation of Flood Volumes and Simulation of Flood Hydrographs for Ungaged Small Rural Streams in Ohio shall be used to determine flood volumes and hydrographs for rural areas within the limits prescribed in the report Alternate Discharge Sources for Bridges Discharge estimates may be calculated by other methods for comparisons against verified flood elevations and other known river data to ensure that the most realistic discharge for the area is used for the design of the waterway opening. Submit calculations and comparisons to the Office of Hydraulic Engineering for review. Flood Insurance Studies (FIS); U.S. Corps of Engineer Flood Studies; U.S. Soils Conservation Studies; U.S. Water Resources Data and other reliable sources may be used as reference information in estimating discharges and flood elevations. However, for waterway crossings located in a FIS area, the base discharge (Q100) from the FIS takes precedence over all other calculated discharges. Where a U.S. Geological Survey estimate is in conflict with that of another agency, contact the agency in order to resolve the discrepancy. In general, the U.S. Geological Survey estimate is given preference. Design proposed structures upstream or downstream from a flood control facility for discharges as supplied by the U.S. Corps of Engineers, Ohio Department of Natural Resources or the agency responsible for the flood control facility Limitations Specific limitations on the use of the USGS regression equations can be found in each report. The USGS Report and USGS were developed for flood-peak discharge estimates for unregulated streams draining rural basins. USGS Open File Report 2432 "Estimation of Peak-Frequency Relations, Flood Hydrographs, and Volume - Duration - Frequency Relations of Ungauged Small Urban Streams in Ohio may be used in the design of culverts, detention basins, large storm sewers, and large open channels with urban drainage areas within the limits prescribed in the report. January

30 Drainage Design Criteria Use the rational method (Section ) in the design of pavement inlets, roadway ditches, culverts, and small storm sewers. Use this method for drainage areas up to a maximum of 200 acres where no well defined natural channel exists and sheet flow prevails. For additional guidance on the proper use of USGS regression equations see Transportation Research Record 1319 Report Information Needs for the Proper Application of Hydrologic Regional Regression Equations Flood Clearance General Where a new highway crosses or is located in a flood plain, the highway grade shall normally be set such that the low edge of the pavement will clear the design water surface profile for existing conditions by 3 feet, and bridges (low chord) will generally clear the water surface profile of the design year frequency flood. These clearances may be reduced where an economic comparison of alternatives shows that a reduction in clearance will result in significant savings, giving full consideration to future flood-related costs relative to: highway operation, maintenance, and repair; highway-aggravated flood damage to other property; and for additional or interrupted highway travel. Flood clearances may also be reduced to protect important ecological resources as identified in the environmental documentation. An economic comparison of alternatives shall be performed to determine the future flood-related costs relative to: highway operation, maintenance, and repair; highway-aggravated flood damage to other property; and for additional or interrupted highway travel Design Year Frequency Freeways or other multi-lane facilities with limited access Year Other Highways (2000 ADT and over) and Freeway Ramps..25 Year Other Highways (under 2000 ADT) Year *Bicycle pathway.. 5 Year * Unless otherwise approved by OHE Highway Encroachments on Flood Plains General All highways that encroach on floodplains, bodies of water or streams, shall be designed to permit conveyance of the 100-year flood without causing significant damage to the highway, the watercourse, body of water or other property. Hydraulically design structures and/or channels to convey the design-year discharge. Ensure the structure and/or channel will convey the 100-year discharge without causing property damage. Inundation of the highway is acceptable for the 100-year discharge, but it is not permitted for the design-year discharge. Water surface elevations caused by existing structures do not have to be lowered to meet the 100-year discharge. Longitudinal highway encroachments require alternative location studies to be summarized in the Feasibility Study (L&D Section ) Flood Data and Flood Insurance Studies (FIS) Flood hazard areas are delineated on Flood Insurance Rate Maps (FIRM) and Flood Insurance Studies (FIS) as Special Flood Hazard Areas (SFHA). SFHAs are defined as the areas that will be inundated by a flood having a 1-percent chance of occurring in any given year (also known as the 100-year flood). The 10-8 January 2018

31 Drainage Design Criteria water surface elevation of the 1-percent annual chance flood is referred to as the Base Flood Elevation (BFE). The SFHA is typically comprised of two components, the floodway and fringe. The floodway is the channel of a watercourse and the adjacent land areas that must be reserved in order to discharge the 1-percent annual chance flood (or base flood) without cumulatively increasing the water surface elevation more than a designated height. The flood fringe is the portion of the floodplain, outside of the floodway, that contains slow-moving or standing water (see figure ). The limits of the floodway are created by a computer model (HEC-RAS) that conveys the base flood discharge within artificial encroachments placed within the floodplain until an allowable water surface surcharge is established. The allowable surcharge for the National Flood Insurance Program (NFIP) is set at one (1) foot, however local authorities may reduce the allowable surcharge below the one foot criteria. Special consideration must be given when designing a structure located within a reach of channel that is part of an FIS. Perform a step backwater analysis of the floodplain to the extent required by FEMA. SFHAs are labeled as different Zones. Flood Insurance Zone designations may be accessed at the following web site: The more common FIS Risk zones are as follows: ZONE A AE, A1-A30 DESCRIPTION Areas subject to inundation by the 1-percent-annual-chance flood. Detailed hydraulic analyses have not been performed, no BFE or flood depth is shown. Use hydrology methods outlined in Areas subject to inundation by the 1-percent-annual-chance flood determined by detailed study methods. BFEs are shown within these zones. (Zone AE is used on new and revised maps in place of Zones A1- A30). An existing hydraulic model should be available from FEMA. Use the 100 year discharge found in the FEMA model for the analysis. AE (BFEs WITH Floodway): BFEs and floodways have been determined and depicted on the FIRM. AE (BFEs WITHOUT Floodway): BFEs have been determined, but no floodway has been generated (and is not delineated on the FIRM). In SFHAs with BFEs, but no floodway, a hydrologic and hydraulic (H&H) analysis is required demonstrating that the cumulative effect of proposed development, when combined with all other existing and anticipated development will not increase the water surface elevation of the base flood by more than the allowable surcharge Proposed Construction in FEMA Zones Construction within FEMA Zone A requires documentation through the ODOT self-permit process and coordination with the Local Floodplain Coordinator. A BFE has not been established. Limit the allowable water surface surcharge to the requirements from the Local Floodplain Coordinator or one (1) foot, whichever is less. Contact OHE if the allowable surcharge required by the Local Floodplain Coordinator is not feasible. Construction within FEMA Zones AE or A1-A30 requires documentation through the ODOT self-permit process, coordination with FEMA, ODNR, and the Local Floodplain Coordinator. Where a floodway is established, ensure the proposed construction spans the floodway if feasible. A No-Rise condition is preferred if construction is performed within the floodway. If proposed construction within the floodway creates any increase in the water surface elevation above the BFE, a variance is required and approval through the appropriate FEMA map revision processes will be necessary. Where no floodway is established and the proposed construction creates any increase in the water surface elevation above the January

32 Drainage Design Criteria BFE + Allowable Surcharge, a variance is required and approval through the appropriate FEMA map revision processes will be necessary. The Ohio Department of Natural Resources Floodplain Management Program (FMP) coordinates the National Flood Insurance Program (NFIP) throughout the State of Ohio as specified in Section 1521 of the Ohio Revised Code. The FMP works as a liaison between communities that participate in the NFIP and the Federal Emergency Management Agency (FEMA), who administers the program nationally. Additional information can be found at: Locally administered projects are required to obtain a permit from the Local Floodplain Coordinator for proposed work within a FEMA SFHA. A current list of Floodplain Coordinators can be found at: 0Contact%20List_10_14.pdf Exceptions ODOT has determined that the following types of projects will have no impact upon the BFE and a hydraulic analysis is not required: a. Bridge Painting b. Bridge maintenance (i.e.: bridge deck or superstructure replacement) that is performed where the existing low chord of the bridge has freeboard over the BFE including the allowable surcharge. c. Any bridge or culvert maintenance that does not change the alignment, grade, or hydraulic capacity of the existing structure as determined by the District Hydraulic Engineer. When utilizing Temporary Access Fill (TAF) refer to the special provisions for waterway permits. For exempt projects located within a Special Flood Hazard Area Zone A or AE, provide a Letter of Notification of SFHA Exemption (LD-53) to the Local Floodplain coordinator and copy to the project file. Form LD-53 can be found at: 2/Pages/LandD-Vol-2.aspx ODOT Self-Permit Process Compliance with federal, state and local floodplain standards is required; however, obtaining a permit from the Local Floodplain Coordinator is not required for work administered by or for the Department (ORC D). The Department will self-permit under this process. In order to maintain and verify compliance, thorough documentation is necessary. The Local floodplain coordinator must be contacted early in the process to obtain any local standards that may be more restrictive than FEMA requirements (i.e.: allowable surcharge, compensatory storage, etc.). Ensure all documentation requesting Local requirements is kept in the project file. For construction within the following FEMA Zones, provide a copy of the following documentation to the Local Floodplain Coordinator and the project file. Zone A: a. Letter of Notification (Form LD-52) b. Letter of Compliance (Form LD-51), note if a variance requesting relief from local standards is required. c. Calculations demonstrating the carrying capacity of the stream is maintained. d. If a variance is requested for relief from local standards, further coordination is required between ODOT, the Local Floodplain Coordinator, ODNR and FEMA. Contact OHE if a variance is required January 2018

33 Drainage Design Criteria Zone AE, without Floodway: a. Letter of Notification (Form LD-52) b. Letter of Compliance (Form LD-51), note if a variance requesting relief from local standards is required. c. Hydrologic and Hydraulic calculations. d. If a variance is requested for relief from local standards, further coordination is required between ODOT, the Local Floodplain Coordinator, ODNR and FEMA. Contact OHE if a variance is required. Zone AE, with Floodway: a. Letter of Notification (Form LD-52) b. Letter of Compliance (Form LD-51), note if a variance requesting relief from local standards is required. c. Hydrologic and Hydraulic calculations. d. No-Rise Certification (Form LD-50), if applicable. e. If a variance is requested for relief from local standards, further coordination is required between ODOT, the Local Floodplain Coordinator, ODNR and FEMA. Contact OHE if a variance is required. Forms LD-50, LD-51 and LD-52 can be found at: 2/Pages/LandD-Vol-2.aspx Type of Studies Hazard Evaluation for Watercourses without a Defined FEMA SFHA A flood hazard evaluation is required for all watercourse involvements except for FEMA Zone A, AE, or A1- A30 zones or where roadway culverts are provided to satisfy minimum size requirements.. A Flood Hazard Evaluation is a condition statement regarding the nature of the upstream area, the extent of upstream flooding, and whether buildings are in the 100 year frequency flood plain. Perform the following for a flood hazard evaluation: A. Determine the water surface elevation of the design year and 100-year flood. B. Delineate the inundation area for the peak water surface elevation for the design year and 100-year flood on a topographic map or a digital map. C. Evaluate the impacts of any increase in the flooding limits Detailed Study If the Hazard Evaluation indicates a significant increase in the flooding of upstream property, a Detailed Study is required. Furnish a Detailed Study in highly urbanized areas where the potential for flooding cannot be accurately assessed without an analysis of the entire floodplain. For pre-fabricated structures, the Detailed Study, including a step-backwater analysis, will be authorized after review of the Hazard Evaluation, by OHE Allowable Headwater Design Storm The frequency of the design storm shall be as stated in Section January

34 Drainage Design Criteria Culvert Headwater Controls Design Storm Controls Headwater depth for all culverts (Type A Conduits) shall not exceed any of the following controls for the design storm: A. 2 feet below the near, low edge of the pavement for drainage areas 1000 acres or greater and 1 foot below for culverts draining less than 1000 acres. B. 2 feet above the inlet crown of the culvert or above a tailwater elevation that submerges the inlet crown in flat to rolling terrain. C. 4 feet above the inlet crown of a culvert in a deep ravine. D. 1 foot below the near edge of pavement for bicycle pathways Check Storm Controls Headwater depth for all culverts (Type A Conduits) shall not exceed any of the following controls for the applicable check frequency storm. A. 2 feet below the lowest ground elevation adjacent to an occupied building for a 50-year storm (it is not intended, however, to lower existing high water elevations around buildings). B. The designer should generally limit the maximum 100-year headwater depth to twice the diameter or rise of the culvert. C. A replacement structure should be sized to prevent overtopping by the 100-year flood where such overtopping would not occur with the existing structure. D. A replacement structure should be sized such that flooding of upstream productive land is not increased for the 100-year flood when compared to the existing structure. Judgment shall be used in implementing this criteria, considering the type of upstream property and sensitivity to the accuracy of the computed flood stages. E. No increase in 100-year headwater elevation shall occur in a FEMA designated floodway Limitations B and C; and B, are arbitrary headwater controls. When B is applicable, use smooth pipe to establish the allowable headwater in feet. When C controls, use corrugated pipe to establish the headwater and thereby permit the same headwater elevation regardless of type of pipe. More heading will be considered if pipe sizes can be reduced and not cause flooding damage upstream or excessive outlet velocity B and C are arbitrary controls and generally apply to small culverts. Where large structures (greater than or equal to 10 feet in span) are involved, the structure should be sized to pass the design storm while maintaining a free water surface through the structure, unless tail water controls. The near low edge of pavement is the location where roadway overtopping will occur. This may or may not be located directly over the culvert. Where the overtopping point on the roadway is outside the watershed break, the ditch break overflow elevation should be utilized as a headwater control in lieu of A January 2018

35 Drainage Design Criteria Controls Specific to Flood Plain Insurance Studies When making an encroachment on a NFIP designated floodplain in the floodway fringe, the rise in the water surface above the natural 100 year flood elevation is limited by the community. Contact the community to determine the allowable rise. No increase in the 100 year water surface is allowed when encroaching on a NFIP designated floodway Bridge Headwater Control Evaluate the headwater generated by a bridge in accordance to a flood hazard evaluation. Ensure the headwater meets the following: A. Match the existing headwater for a bridge replacement for the design storm and the check flood to the maximum extent practicable. Any increase in headwaters verify the upstream impacts. B. Design flood does not contact the low chord for new structures on new alignment. C. Regulations from Conservancy Districts if they are more restrictive than the Departments. D. Controls specific to a FIS Controls Specific to Flood Insurance Studies (FIS) Contact the Local Floodplain Coordinator early in the design process to determine the allowable headwater increase and or the permitting requirements. A current list of Floodplain Coordinators may be found at: 0Contact%20List_10_14.pdf When making an encroachment on a FIS designated floodplain in the floodway fringe, the rise in the water surface above the natural 100 year flood elevation is limited by the community. See Figure for a graphical definition of the floodway, floodway fringe, and flood plain. No increase in the 100 year water surface is allowed when encroaching on a FIS designated floodway Pipe Removal Criteria General Use the following guidelines to determine whether an existing pipe, regardless of type, being taken out of service should be abandoned or removed. A. Pipes 8 inches in diameter or rise, or less, regardless of depth or height of fill, may be abandoned in place. B. Pipes 10 inches through 24 inches in diameter or rise with less than 3 feet of final cover should be removed or filled; with more than 3 feet of final cover they may be abandoned in place. (The designer should use discretion in removing small pipes based on roadway importance, pipe material longevity and if the pipe is under existing rigid pavement or base which is to remain in place.) C. Pipes over 24 inches in diameter or rise should generally be removed. (The designer should use discretion in removing any pipe with more than 10 feet of cover.) January

36 Drainage Design Criteria Asbestos pipe Asbestos pipe is a regulated material. Designers should make reasonable efforts to identify existing asbestos pipes in the plans and, when necessary, provide appropriate removal quantities. In the past, pipe containing asbestos was allowed on ODOT, LPA and utility projects under the following specifications: ASTM C663 Asbestos-Cement Storm Drain Pipe AASHTO M217 AWWA C400 AWWA C603 ASTM C296 Asbestos-Cement Pressure Pipe ODOT CMS Asbestos Bonded Bituminous Corrugated Steel Pipe and Pipe Arches (Circa 1983) ODOT CMS Asbestos Cement Perforated Underdrain Pipe (Circa. 1973) Transite is a common brand name for a type of asbestos pipe. Asbestos can also be found in insulation wrapped around water pipes. Reasonable efforts to identify asbestos pipes would include the following: A. Examination of original construction plans and specifications. B. Contact with the owner of the pipe (e.g., utility company or LPA). C. Inspection of the pipe for markings when the pipe is exposed during routine maintenance operations. Removal of asbestos pipe is specified in the most current CMS as Item 202 Asbestos Pipe Removed. For projects to be constructed under the 1997 CMS, use Item 202 Pipe Removed, As Per Plan and indicate that the pipe must be removed by a certified asbestos contractor. Asbestos is a hazard only when it becomes airborne. Pipes that are otherwise unaffected by ODOT work do not need to be removed simply because they contain asbestos. Not all asbestos pipes will be identified by a records search. Construction inspectors are being advised to test suspicious pipe for asbestos. If asbestos pipe is identified, the contractor will be compensated by change order Conduit Design Criteria Corrugated and Spiral Rib Steel and Aluminum Pipes, and Corrugated Steel and Aluminum Pipe Arches Material Durability The Criteria outlined in Section specifying types of protective coatings and/or extra metal thickness shall be followed Designation and Thickness The corrugation profile and required metal thickness for structural strength is furnished by the Manufacturer in accordance to Construction and Material Specifications Handbook (CMS) Item January 2018

37 Drainage Design Criteria Cambered Flow Line Where soil conditions at the site indicate that appreciable settlement is expected, provide a cambered flow line. Show the cambered flow line as a vertical curve following the Manufacturer recommendation Height of Cover See General Notes for Figures through and through for minimum height of cover Foundation Reports Conduct an investigation of the supporting foundation material to estimate the bearing capacity of the material and determine that no settlement will occur. A foundation investigation is required for all proposed metal pipe installations with 100 feet of fill or more and all pipe arch installations. Submit the foundation report with the Stage 1 review. Refer to section for information on foundation types Rigid Pipe General Where soil conditions at the site indicate that appreciable settlement is expected, provide a cambered flow line. Show the cambered flow line as a vertical curve following the Manufacturer recommendation Height of Cover The maximum allowable height of cover is measured from the top of the pipe to the pavement surface. The minimum cover, from the top of the pipe to the top of the subgrade, or finish grade for pipe not under pavements, is 9 inches; however, in no installation shall the distance from the top of the pipe to the pavement surface be less than 15 inches Thermoplastic Pipe Height of Cover The maximum allowable height of cover is measured from the top of the conduit to the pavement surface or to finished grade for pipes not under pavement. The minimum cover, from the top of the pipe to the top of the subgrade, is 12 inches; however, in no installation shall the distance from the top of the pipe to the pavement surface, or finish grade for pipes not under pavement, be less than 18 inches Corrugated Steel and Aluminum Box Culverts and Corrugated Steel Long Span Culverts Designation and Thickness The corrugation profile and metal thickness required shall be in accordance with the AASHTO LRFD Bridge Design Specifications design methodologies. Structural strength design is furnished by the Manufacturer in accordance to Construction and Material Specifications Handbook (CMS) Item 611. The skew of the structure relative to the roadway shall be given in 1 increments and typically should not exceed 15. January

38 Drainage Design Criteria Height of Cover In no case shall the minimum cover, measured from the trough of the corrugation profile to the pavement surface, be less than 18 inches. In addition to the above requirements, corrugated steel and aluminum box culverts shall be provided with adequate cover to ensure that the culvert rib stiffeners are located completely within the subgrade Foundation Reports Conduct an investigation of the supporting foundation material and estimate the bearing capacity of the foundation material. Submit the foundation report for all proposed metal box and long span culvert installations with the Stage 1 review Precast Reinforced Concrete Box Culverts Designation The allowable sizes of precast reinforced concrete box culverts shall be as given in Figure The pay item description shall include the height of cover (design earth cover), rounded to the highest 1 foot. Structures with a span of 12 feet or less shall be designed as per ASTM C Structures with spans 14 feet or greater require a special design. CMS Item refers to SS 940 which lists the special designs for each span and fill height (design cover) Height of Cover The maximum allowable height of cover is measured from the top of the culvert to the pavement surface. The maximum height of cover will be limited to 10 feet. Greater covers may be provided contingent upon the approval of the Manufacturer. A special design is required Precast Reinforced Concrete Three-Sided Flat-Topped Culverts Designation Precast reinforced concrete three-sided, flat-topped culverts shall have a minimum clear span of 14 feet and minimum opening rise of 4 feet; and a maximum clear span of 34 feet and maximum opening rise of 10 feet. The individual culvert units may be skewed in 5 increments with a maximum skew of 30. Designate the skew of the structure relative to the roadway in 1 increments with a maximum skew of 30. The minimum deck thickness for the culvert units is 12 inches and the minimum leg thickness for the culvert units is 10 inches. The design should be based on these dimensions Height of Cover The maximum allowable height of cover is measured from the top of the culvert to the pavement surface. The maximum height of cover should be limited to 5 feet. Greater covers may be provided contingent upon the approval of the Manufacturer Foundation Reports Conduct an investigation of the supporting foundation material and estimate the bearing capacity of the foundation material. Submit the foundation report for all proposed flat-topped, three-sided culvert installations with the Stage 1 review January 2018

39 Drainage Design Criteria Show the footing and/or pedestal wall vertical and horizontal unfactored reaction forces in the plans. Refer to section for information on foundation types Precast Reinforced Concrete Arch Sections Designation Precast reinforced concrete arch sections have a clear span of 12 to 34, 36, 42, 48, 54, 60 feet and an opening rise of 4 feet through 13 feet (maximum). Use of other sizes requires that a Proprietary Waiver Request (Proprietary Product Approval Request) be completed and signed by the contracting agency. This form may be found at the following web site: Designate the skew of the structure relative to the roadway in 1 increments with a maximum skew of 30. Individual culvert sections may only be skewed with written permission from OSE. Obtain the deck thickness and leg thickness for the culvert units from the manufacturer. Show the maximum and minimum cover on the plans. Design the footing keyway based on the leg thickness plus 6 inches. Design the guardrail post length based on the deck thickness and cover. Precast reinforced concrete arch sections may only be used for roadway grade separation structures with written approval from the OSE. Standard design modifications, including but not limited to increased concrete thickness, concrete admixtures, epoxy coating of concrete surfaces and epoxy coating of reinforcing steel may be required for approval for use as roadway grade separation structures Height of Cover The maximum allowable height of cover is measured from the top of the culvert to the finished surface. The maximum height of cover is limited to 12 feet. Cover greater than 12 feet may be provided contingent upon the approval of the Manufacturer. The minimum cover, from the top of the arch sections to the top of the pavement is 12 inches. However, in no case shall the top of the arch sections be located above the top of subgrade Foundation Reports Conduct an investigation of the supporting foundation material and estimate the bearing capacity of the foundation material. Submit the foundation report for all precast reinforced concrete arch section culvert installations with the Stage 1 review. Show the footing and/or pedestal wall vertical and horizontal unfactored reaction forces in the plans. Refer to section for information on foundation types Precast Reinforced Concrete Round Sections Designation Precast reinforced concrete round sections are one or two piece structures with a clear span of 12, 16, 20, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78 and 84 feet available in various rises and shapes. Use of other sizes requires that a Proprietary Waiver Request (Proprietary Product Approval Request) be completed and signed by the contracting agency. This form may be found at the following web site: Designate the skew of the structure relative to the roadway in 1 increments with a maximum skew of 30. Individual culvert sections may only be skewed with written permission from OSE. January

40 Drainage Design Criteria Obtain the section thickness for the sections from the manufacturer. Show the maximum and minimum cover on the plans. Design the footing keyway based on the section thickness plus 8 inches. Design the guardrail post length based on the section thickness and cover. Precast reinforced concrete round sections may only be used for roadway grade separation structures with written approval from OHE. Standard design modifications, including but not limited to increased concrete thickness, concrete admixtures, epoxy coating of concrete surfaces and epoxy coating of reinforcing steel may be required for approval for use as roadway grade separation structures Height of Cover The maximum allowable height of cover is measured from the top of the round sections to the finished surface. The maximum height of cover is limited to 12 feet. Cover greater than 12 feet may be provided contingent upon the approval of the Manufacturer. The minimum cover, from the top of the round sections to the top of the pavement is 12 inches. However, in no case should the top of the arch sections be located above the top of subgrade Foundation Reports Conduct an investigation of the supporting foundation material and estimate the bearing capacity of the foundation material. Submit the foundation report for all precast reinforced concrete round section installations with the Stage 1 review. Include with the foundation report a letter from the manufacturer stating the reactions for foundation design. Show the footing and/or pedestal wall vertical and horizontal unfactored reaction forces in the plans. Refer to section for information on foundation types Arch or Flat Slab Top Culvert Foundations Arch or flat slab topped culverts are supported on either spread footings or deep foundations such as piles or drilled shafts. When a series of precast, three-sided structures are used to produce a multiple span structure over a waterway, spread footings are not permitted. Provide deep foundations according to the Bridge Design Manual (BDM). Refer to the Office of Geotechnical Engineering (OGE) for the design of foundations on spread footings. Reasonable and prudent hydraulic analysis of a bridge design requires that an assessment be made of the proposed bridge s vulnerability to undermining due to potential scour. Because of the extreme hazard and economic hardships posed by a rapid bridge collapse, special considerations must be given to selecting appropriate flood magnitudes for use in the analysis. The hydraulics engineer must always be aware of and use the most current scour forecasting technology. Reference HEC-23, Volume 2, Section 6, Design Guideline 18, to estimate scour depths for three sided structures, for all flow conditions. Use K r of 0.38, for the riprap sizing equation (18.1). Use Type C Rock Channel Protection as a minimum. Access and/or download the HEC-23 publication from the publications section of the FHWA Hydraulics Library web site: Provide a cost comparison justification study between alternative structure types, including bridges, when utilizing a deep foundation. Submit the cost comparison justification study during the preliminary engineering phase. Provide a keyway in the foundation to set the arch or flat slab topped culverts into. The width of the keyway is a minimum of 6 inches wider than the precast leg (3 inches on both sides of the leg). The depth of the keyway is a minimum of 3 inches January 2018

41 Drainage Design Criteria Bridge Foundations Perform a scour evaluation for all bridges not founded on scour resistant bedrock. When evaluating scour for a replacement structure, review all inspection reports for evidence of stream degradation (lowering of stream bed), scour or previous scour countermeasures. Compute scour depths with the equations in HEC- 18 (Hydraulic Engineering Circular No. 18, Pub. No. FHWA NHI ), Evaluating Scour at Bridges. Consider scour depth in the design of the substructures and the location of the bottom of footings and minimum tip elevations for piles and drilled shafts. All major rehabilitation work requires a scour evaluation. The scour evaluation may consist of determining what the bridge is founded on. For example, for a bridge rehabilitation, noting that the bridge is founded on scour resistant bedrock or deep foundations to bedrock, would constitute the scour evaluation. As a minimum, piles shall be embedded 15 ft. below the streambed elevation. Provide a narrative of findings and recommended scour counter-measures in the Structure Type Study. Include a statement regarding the susceptibility of the stream banks and flow line to scour, and also the susceptibility of the piers and abutments to scour Scour Design Flood Frequencies Bridge foundations are designed to withstand the effects of scour caused by hydraulic conditions from floods larger than the design flood. The frequencies for the scour design flood and the scour check flood are determined by the hydraulic design flood frequency used to hydraulically size the bridge. Use the following table to determine the flood frequency for scour: Hydraulic Design Flood Frequency Waterproofing Membrane Scour Design Flood Frequency Scour Check Flood Frequency Q10 Q25 Q50 Q25 Q50 Q100 Q50 Q100 Q500 Apply an external waterproofing membrane to all precast reinforced concrete box culverts, three-sided flattopped culverts, arch culverts and round sections. Use Item 512 Waterproofing, Type 2 along the vertical sides and Type 2 or 3 across the top of the structure. Type 3 waterproofing shall be used if pavement is to be used directly on top of the structure. Provide an overlap of a minimum of 12 inches of the top membrane to the vertical membrane Precast Reinforced Concrete Flat Slab Tops, Catch Basin Tops, and Inlet Tops Precast Reinforced Concrete Flat Slab Tops, Catch Basin Tops, and Inlet Tops shall be designed in accordance with ASTM C478. When the structure is under pavement and the span is greater than 10 feet, the design loading for the structural design shall be HL Wingwall Design When not using the standard construction drawings or design data sheets, design wingwalls in accordance to the current AASHTO LRFD Bridge Design Specifications. Assume no passive forces are acting on the toe of the wall. January

42 Drainage Design Criteria 1009 Subsurface Pavement Drainage General Subsurface pavement drainage is required on all projects except when located in an area having a granular subgrade. See the Pavement Design Manual, Section 205 Subsurface Pavement Drainage for guidance Maintenance of Traffic Drainage General Positive drainage during Maintenance of Traffic (MOT) operations is furnished under items 614 and 615 of the CMS for most projects. Evaluate MOT drainage for projects on Interstates and Expressways that have one or more of the following or as directed by the District: A. Multi-phased MOT operations B. Profile changes in the roadway that temporarily create a sag point different than the final design C. Traffic maintained adjacent to concrete barrier with less than 2 feet clear distance from the edge of lane to the edge of barrier Furnish a minimum dry lane width of 10 feet for each travelled lane. Determine the spread of water on the pavement using a 2 year design frequency unless a different frequency is specified by the District. Provide MOT drainage by utilizing permanent drainage items for final design and temporary drainage items. Temporary drainage items may include items such as inlets, storm sewers, culverts, ditches, perforated conduits, catch basins, conduits jacked and bored, opening cuts in concrete barrier, French drains, pavement saw cut openings, etcetera. These drainage items may conflict with future MOT phases and may require removal quantities in subsequent MOT phases. Use permanent drainage items for final design where feasible. Furnish a minimum diameter of 12 inches for temporary storm sewer and 18 inches for temporary culverts. Provide temporary drainage items on the MOT plan per plan note D Temporary Structures The design year and other hydraulic requirements for temporary structures are defined in CMS Ensure scour depth is accounted for in the in the design of a temporary bridge and foundation. Show the water surface elevation ( high water ) and velocity of the design year discharge on the temporary structure plans. Ensure the design year discharge does not contact the lowest portion of the superstructure of a temporary bridge. Culvert pipes may be used in lieu of a bridge structure provided controls specified in Section 1006 are not exceeded for the design year discharge. Refer to Section 500 of the Bridge Design Manual for other details regarding temporary structures January 2018

43 1000 Drainage Design Criteria List of Figures Figure Subject Minimum Culvert Sizes Water ph Contours - Average for Counties Water ph Contours - Values of Individual Culverts Table Deleted July (50) Table Deleted July (75) Table Deleted July (50) Table Deleted July (75) Table Deleted July Floodway Schematic General Notes for Figures through Minimum Height of Cover - Corrugated Steel Pipe Minimum Height of Cover - Corrugated Steel Pipe Arches Minimum Height of Cover - Structural Plate Corrugated Steel Pipe Minimum Height of Cover - Structural Plate Corrugated Steel Pipe Arches (18-inch Corner Radius) Minimum Height of Cover - Structural Plate Corrugated Steel Pipe-Arches (31-inch Corner Radius) Minimum Height of Cover - Corrugated Steel Spiral Rib Pipe General Notes for Figures through Reinforced Concrete Circular Pipe Reinforced Concrete Elliptical Pipe Maximum Allowable Height of Cover - Reinforced Concrete Box Culverts General Notes for Figures through Minimum Height of Cover - Corrugated Aluminum Pipe Minimum Height of Cover - Corrugated Aluminum Pipe Arches Minimum Height of Cover - Structural Plate Corrugated Aluminum Pipe Minimum Height of Cover - Structural Plate Corrugated Aluminum Pipe Arches Minimum Height of Cover - Corrugated Aluminum Spiral Rib Pipe January 2018

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49 General Notes - Figures through Thickness The following table shows the available commercial thicknesses for metallic coated steel and the corresponding gage number: Metal Thickness (Inches) Gage Number The maximum available sheet thickness for aluminum coated corrugated steel pipe (707.01, , , ; all with aluminum coating) or polymer coated corrugated steel pipe (707.04) is Minimum Cover The minimum cover is measured from the top of the pipe or pipe-arch to the top of subgrade; however, in no installation shall the distance from the top of the pipe or pipe-arch to the top of the wearing surface or finished grade be less than the figure values plus 6 inches. Maximum Cover The maximum height of cover is measured from the top of the pipe or pipe-arch, to the top of the wearing surface.

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51 MINIMUM HEIGHT OF COVER TABLE 1 CORRUGATED STEEL PIPE Revised July Reference Section Pipe Designation , , , and (2 2/3" x 1/2" Corrugations) , , , and (5" x 1" Corrugations) Pipe Diameter (inches) HEIGHT OF COVER TABLE 1 Corrugated Steel Pipe Minimum Cover (inches)

52 Revised July 2014 MINIMUM HEIGHT OF COVER TABLE 2 CORRUGATED STEEL PIPE ARCHES Reference Section HEIGHT OF COVER TABLE 2 Pipe Designation Pipe Dimentions Span X Rise Corrugated Steel Pipe Arches Minimum Cover , , , and (2 2/3" x 1/2" Corrugations) , , , and (5" x 1" Corrugations) (inches) 17 x x x x x x x x x x x x x x x x x x x x x x x x x x x 91 (inches)

53 MINIMUM HEIGHT OF COVER TABLE STRUCTURAL PLATE CORRUGATED STEEL PIPE Revised July Reference Section Pipe Diameter HEIGHT OF COVER TABLE Structural Plate Corrugated Steel Pipe Pipe Diameter Minimum Cover (inches) (feet-inches) 60 5'0" 66 5'6" 72 6'0" 78 6'6" 84 7'0" 90 7'6" 96 8'0" 102 8'6" 108 9'0" 114 9'6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" '6" '0" (inches)

54 MINIMUM HEIGHT OF COVER TABLE STRUCTURAL PLATE CORRUGATED STEEL PIPE ARCHES Revised January Reference Section HEIGHT OF COVER TABLE Structural Plate Corrugated Steel Pipe (18-inch Corner Radius) Pipe Dimentions Span X Rise (feet-inches) 6'1" x 4'7" 6'4" x 4'9" 6'9 x 4'11" 7'0" x 5'1" 7'3" x 5'3" 7'8" x 5'5" 7'11" x 5'7" 8'2" x 5'9" 8'7" x 5'11" 8'10" x 6'1" 9'4" x 6'3" 9'6" x 6'5" 9'9" x 6'7" 10'3" x 6'9" 10'8" x 6'11" 10'11" x 7'1" 11'5" x 7'3" 11'7" x 7'5" 11'10" x 7'7" 12'4" x 7'9" 12'6" x 7'11" 12'8" x 8'1" 12'10" x 8'4" 13'5" x 8'5" 13'11" x 8'7" 14'1" x 8'9" 14'3" x 8'11" 14'10" x 9'1" 15'4" x 9'3" 15'6" x 9'5" 15'8" x 9'7" 15'10" x 9'10" 16'5" x 9'11" 16'7" x 10'1" Minimum Cover (inches)

55 MINIMUM HEIGHT OF COVER TABLE STRUCTURAL PLATE CORRUGATED STEEL PIPE ARCHES Revised January Reference Section HEIGHT OF COVER TABLE Structural Plate Corrugated Steel Pipe (31-inch Corner Radius) Pipe Dimentions Span X Rise (feet-inches) 13'3" x 9'4" 13'6" x 9'6" 14'0" x 9'8" 14'2" x 9'10" 14'5" x 10'0" 14'11" x 10'2" 15'4" x 10'4" 15'7" x 10'6" 15'10" x 10'8" 16'3" x 10'10" 16'6" x 11'0" 17'0" x 11'2" 17'2" x 11'4" 17'5" x 11'6" 17'11" x 11'8" 18'1" x 11'10" 18'7" x 12'0" 18'9" x 12'2" 19'3" x 12'4" 19'6" x 12'6" 19'8" x 12'8" 19'11" x 12'10" 20'5" x 13'0" 20'7" x 13'2" Minimum Cover (inches)

56 MINIMUM HEIGHT OF COVER TABLE 6 FOR CORRUGATED STEEL SPIRAL RIB PIPE Revised January Reference Section HEIGHT OF COVER TABLE 6 Pipe Designation Pipe Diameter Corrugated Steel Spiral Rib Pipe Minimum Cover (inches) (inches) (3/4" x 7 1/2" Corrugations)

57 General Notes - Figures through Minimum Cover See Section Maximum Cover The maximum height of cover is measured from the top of the pipe or elliptical pipe to the top of the wearing surface.

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59 REINFORCED CONCRETE CIRCULAR PIPE Revised January Reference Section Reinforced Concrete Circular Pipe Pipe Diameter Wall Thickness (inches) (inches)

60 REINFORCED CONCRETE ELLIPTICAL PIPE Revised January Reference Section Reinforced Concrete Elliptical Pipe Equivalent Pipe Wall Equivalent Pipe Round Rise X Span Thickness Round Rise X Span Wall Thickness Diameter Diameter (inches) (inches) (inches) (inches) (inches) (inches) 18 14x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x180 13

61 MAXIMUM ALLOWABLE HEIGHT OF COVER - REINFORCED CONCRETE BOX CULVERTS Revised January Reference Section Precast Reinforced Concrete Box Culverts Box Span Box Rise (ft) (ft) *Height of Fill (Maximum) Approval of OHE is required for sizes other than those listed above. Spans 14' or greater shall be designed for HL93 live load with an additonal 60psf for a future wearing surface.

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63 General Notes - Figures through Thickness The following table shows the available commercial metal thicknesses for aluminum pipe: Metal Thickness (Inches) , & Metal Thickness (Inches) Minimum Cover The minimum cover is measured from the top of the pipe or pipe arch to the top of subgrade; however, in no installation shall the distance from the top of the pipe or pipe arch to the top of the wearing surface or finished grade be less than the figure values plus 6 inches. Maximum Cover The maximum height of cover is measured from the top of the pipe or pipe arch to the top of the wearing surface.

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71 Table of Contents (Revised January 2018) 1100 Drainage Design Procedures 1101 Estimating Design Discharge General Procedures Statistical Methods Rational Method Coefficient of Runoff Rainfall Intensity Open Water Carriers General Types of Carriers Standard Roadway (Roadside) Ditches Special Ditches Median Ditches Channel Relocations Channel Linings and Bank Stabilization Ditch Design Criteria - Design Traffic Exceeding 2000 ADT Design Frequency Ditch Protection Roughness Catch Basin Types Calculated Catch Basin Spacing Arbitrary Maximum Catch Basin Spacing Ditch Design Criteria - Design Traffic of 2000 ADT or Less Design Frequency Shear Stress Protection Roughness Catch Basin Types Design Aids for Ditch Flow Analysis Earth Channel Charts Rectangular Channel Charts Pavement Drainage General Design Frequency Estimating Design Discharge Capacity of Pavement Gutters Pavement Flow Charts Bypass Charts for Continuous Pavement Grades Curb Opening Inlets Grate or Combination Grate and Curb Opening Inlet Grate Catch Basins and Curb Opening Inlets in Pavement Sags Bridge Deck Drainage Slotted Drains and Trench Drains Storm Sewers General Design Considerations Storm Sewer Depth Storm Sewer Access Rock Excavation for Storm Sewer Layout Procedure Plan Profile Storm Sewer Design Criteria

72 Design Frequency Hydraulic Grade Line Coefficient of Runoff Time of Concentration Pipe Roughness Coefficient Minimum Storm Sewer Pipe Size Maximum Storm Sewer Slope Hydraulic Design Procedure Combined Sanitary Sewer Separation Roadway Culverts General Stream Protection Bankfull Discharge Design Depressed Culvert Inverts Paved Depressed Approach Aprons Flood Plain Culverts Energy Control Structures Types of Culvert Flow Design Procedure General Hydraulic Analysis Use of Nomographs Outlet Control Inlet Control Design Criteria Design Frequency Maximum Allowable Headwater Method Used to Estimate Storm Discharge Scale of Topographic Mapping Used to Delineate Contributing Drainage Areas Manning s Roughness Coefficient n Entrance Loss Coefficient k e Minimum Cover Maximum Cover Maximum Allowable Outlet Velocity Headwall Type Contacts With County Engineer Minimum Pipe Size Ordinary High Water Mark Special Considerations Tailwater Multiple Cell Culverts Improved Inlets End Treatments General Usage End Treatment Grading Headwall Types Half-Height Headwalls Full-Height Headwalls Concrete Apron Rock Channel Protection (RCP) General Culvert RCP Types Bridge RCP Agricultural Drainage Farm Drain Crossings Farm Drain Outlets

73 1109 Longitudinal Sewer Location Under Pavement Under Paved Shoulder Approval Reinforced Concrete Radius Pipe and Box Sections General Sanitary Sewers General Manholes Notice of Intent (NOI) General Routine Maintenance Project Watershed Specific NOI Requirements Erosion Control at Bridge Ends General Corner Cone Temporary Sediment and Erosion Control General Cost Estimate for Temporary Sediment and Erosion Control Post Construction Storm Water Structural Best Management Practices General Project Thresholds for Post-Construction BMP Water Quality and Water Quantity Treatment Water Quality Volume Water Quality Flow Project Type - Redevelopment and New Construction Redevelopment Projects New Construction Projects Pedestrian Facilities and Shared Use Paths Treatment Requirements for Projects BMP Selection and Submittals BMP Selection BMP Submittals BMP Toolbox Manufactured Systems Vegetation Based BMP Vegetated Filter Strip Vegetated Biofilter Extended Detention Detention Basin Underground Detention Design Check Discharge Retention Basin Water Quality Basin and Weir Bioretention Cell Level bioretention cell in an open area with grassed side slopes Sloped bioretention cell within a grassed ditch Bioretention Cell Design Procedure Infiltration Infiltration Trench Infiltration Basin Constructed Wetlands Stream Grade Control Bridge Hydraulics General Hydrology and Hydraulics (H&H) Report Analysis Narrative

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75 1100 Drainage Design Procedures 1101 Estimating Design Discharge General In order to properly design highway drainage facilities, it is essential that a reasonable estimate be made of the design and check discharges. Some of the more important factors affecting runoff are duration, intensity and frequency of rainfall; and the size, imperviousness, slope, and shape of the drainage area. Use suitable topographic mapping to determine the contributing drainage area. For drainage areas over 100 acres, a 7.5 minute U.S. Geological Survey Quadrangle will ordinarily suffice. For smaller areas, or where discharges are calculated using the rational method, smaller scale maps (1 =50 to 1 =800 ) may be more appropriate. Other methods that use Geographic Information Systems (GIS) such as USGS Stream Stats are acceptable. The use of contours generated from LiDAR data collected through the Ohio Statewide Imagery Program (OSIP) is also acceptable. A proper evaluation should be made of the land use throughout the drainage area. Changes in land use within the drainage area which will occur in the immediate future shall be taken into account when determining design discharges. However, probable land use changes beyond this should not be assumed when determining design discharges. It is the responsibility of the local permitting/zoning agency to ensure proper land and water management techniques are utilized. These techniques will minimize the adverse effects of a change in land use. Post Construction Storm Water Best Management Practices are used on roadway projects in an effort to minimize quality and quantity impacts as well (see section 1115) Procedures Statistical Methods See Section Rational Method The rational method is considered to be more reliable for estimating runoff from small drainage areas, less than the acreage for the USGS Regions; and for areas that contribute overland flow and shallow concentrated flow to the roadway ditch or pavement. The design discharge Q is obtained from the equation: Q = CiA Where: Q = Discharge in cubic feet per second C = Coefficient of runoff I = Average rainfall intensity in inches per hour, for a given storm frequency and for a duration equal to the time of concentration. A = Drainage area in acres The time of concentration is the time required for runoff to flow from the most remote point of the drainage area to the point of concentration. The point of concentration could be a culvert, catch basin or the checkpoint in a roadway ditch used to determine the need for velocity protection. Time of concentration is designated by t c and is the summation of the time of overland flow t o, the time of shallow concentrated flow "t s " and the time of pipe or open channel flow t d. January

76 Drainage Design Procedures Overland flow is that flow which is not carried in a discernible channel and maintains a uniform depth across the sloping surface. It is often referred to as sheet flow. The time of overland flow may be obtained from Figure , a similar overland flow chart, or from the equation: Where: t o = Time of overland flow in minutes C = Coefficient of runoff L = Distance to most remote location in drainage area in feet (300 ft. max) s = Overland slope (percent) t o 1.8(1.1- C) L 1/2 s 1/3 These methods should not be used to determine the time of travel for gutter, swale, or ditch flow. This equation and Figure assume a homogeneous drainage area. Where the overland flow area is composed of segments with varying cover and/or slopes, the summation of the time of concentration for each segment will tend to over-estimate the overland flow time, t o. In this case it may be more appropriate to use an average runoff coefficient "C" and an average ground slope in the Overland Flow Chart. Sheet flow is assumed to occur for no more than 300 feet after which water tends to concentrate in rills and then gullies of increasing proportion. This type of flow is classified as shallow concentrated flow. The velocity of shallow concentrated flow can be estimated using the following relationship: Where: V = Velocity in fps k = Intercept coefficient (see Table ) s = Overland slope (percent) V = 3.281ks 0.5 Table Intercept Types of Surface Coefficient k Forest with heavy ground litter Min. tillage cultivated; woodland Short grass pasture Cultivated straight row Poor grass; untilled Grassed waterways Unpaved area; bare soil Paved area Shallow concentrated flow generally empties into pipe systems, drainage ditches, or natural channels. The velocity of flow in an open channel or pipe can be estimated using the Manning's equation January 2018

77 Drainage Design Procedures The travel time for both shallow concentrated flow and open channel or pipe flow is calculated as follows: t s or t d = L 60V Where: t s = Travel time for shallow concentrated flow in minutes t d = Travel time for open channel or pipe flow in minutes L = Flow length in feet V = Velocity in fps Where a contributing drainage area has its steepest slope and/or highest "C" value in the sub-area nearest the point of concentration, the rational method discharge for this sub-area may be greater than if the entire contributing drainage area is considered. The maximum runoff rate for a sub-area should be considered only if greater than that for the entire area Coefficient of Runoff The coefficient of runoff is a dimensionless decimal value that estimates the percentage of rainfall that becomes runoff. The recommended values for the coefficient of runoff for various contributing surfaces are shown in Table Where two values are shown, the higher value ordinarily applies to the steeper slopes. For Residential areas, lot size should also be considered in choosing the appropriate value for the coefficient of runoff. Generally, a higher value should be associated with smaller lots and a lower value should be associated with larger lot sizes. The selected coefficient should be based upon an estimation of the typical slope, lot size, and lot development. The total width contributing flow to a given point usually consists of surfaces having a variable land cover and thereby requires a weighted coefficient of runoff C. The weighted coefficient is obtained by averaging the coefficients for the different types of contributing surfaces, as noted in the following example: Table Types of Surface Coefficient of Runoff C Pavement & paved shoulders 0.9 Berms and slopes 4:1 or flatter 0.5 Berms and slopes steeper than 4:1 0.7 Contributing areas Residential (single family) Residential (multi-family) Woods 0.3 Cultivated Contributing Width W Land Use C CW 20 feet Paved Area feet Earth Berms & Slopes feet Residential Area feet Summations 130 Weighted C = 130/200 = 0.65 January

78 Drainage Design Procedures Rainfall Intensity The average rainfall intensity i in inches per hour may be obtained from the Intensity-Duration-Frequency curves shown on Figure Each set of curves applies to a specific geographic area, A, B, C, or D as shown on the Rainfall Intensity Zone Map, Figure The geographic areas were established from an analysis of rainfall records obtained from Weather Bureau stations in Ohio. Some political subdivisions may have developed curves for their specific area similar to Figure Such curves may be based on a much longer period of record and provide more reliable information. Any local curves proposed by the designer should be cleared with the Office of Hydraulic Engineering (OHE) prior to incorporating that information in the drainage calculations Open Water Carriers General Open water carriers generally provide the most economical means for collecting and conveying surface water contributing to the roadway. The required capacity of a water carrier involves a determination of the velocity and depth of flow for a given discharge. These characteristics can best be obtained from charts that are based on Manning s equation. Channel flow charts have been prepared for all the common water carrier shapes and are included in the Drainage Design Aids. A ditch computation sheet similar to that provided in the Appendix shall be used to perform or summarize ditch calculations. As a guideline, the relative minimum roadway ditch grades should be 0.50% with a recommended absolute minimum of 0.25%. Lower grades may be used on large channels as necessary. Open water carriers should maintain a constant slope wherever possible. The proper location of a ditch outfall is quite important. Existing drainage patterns should be perpetuated insofar as practicable. Care should be taken to not capture an existing stream with the roadside ditch. If this is necessary, the designed ditch shall be in accordance to Section Types of Carriers Standard Roadway (Roadside) Ditches The various roadside ditches shown in Volume I, Roadway Design, have proven to be safe and to provide adequate flow capacity. A ditch is considered to be standard when the centerline is parallel to the edge of the pavement and the flowline is a uniform distance below the edge of pavement. A modification of the above is required when the grade of the pavement is too flat to provide acceptable ditch flow, thereby creating the need for a special ditch. Channel charts, Drainage Design Aid Figures through , are included for use in determining velocity and depth of flow for standard ditches having variable side slopes Special Ditches Special ditches other than the modified standard roadway ditch described in Section above, include the following: A. The steep ditch beyond the toe of the embankment used to carry the flow from a cut section to the valley floor. B. Toe of fill ditch which is separated from the toe of fill by a minimum 10 foot wide bench, having a minimum transverse slope of ½ inch per foot toward the ditch. C. Deep parallel side ditches separated from the pavement by a wide bench or earth barrier. The special ditches described in A, B and C above are ordinarily trapezoidal in shape and appropriate charts for the hydraulic analysis are included in this section of the manual or in the FHWA publication Design Charts for Open Channel Flow Hydraulic Design Series No. 3. It is required that the calculated flowline elevation be shown on each special ditch cross section January 2018

79 Drainage Design Procedures Median Ditches The median ditches that are an integral part of all earth medians have the same shape and capacity features as the standard roadside radius ditch and the appropriate ditch chart is applicable for the hydraulic analysis. The fully depressed earth median provides adequate hydraulic capacity and the appropriate flow charts in the Drainage Design Aid Figures , and have been developed for that shape. The rounding shown on the charts varies from 8 feet to 4 feet, depending on the width of the median. The slight discrepancy in the rounding from that shown in Volume I, Roadway Design, is not considered to affect the accuracy of the charts Channel Relocations Major channel relocations should be avoided. However, if it becomes necessary to relocate a channel adhere to the following: The design year frequency used for channel relocations shall be that given in Section All channel relocations shall carefully be designed to preclude erosion or unreasonable changes in the environment. Whenever possible, channel relocations shall be restricted to the downstream end of proposed culverts. The relocated channel shall be of a similar cross-section. Where the existing channel exhibits a two-stage cross section morphology, it shall be replaced with like kind. The two-stage channel is comprised of two distinct areas. The first of these is a meandering bankfull width that carries the channel-forming discharge. The second area is the flood plain width. See Figure for a graphical representation of the major channel features. The proposed channel should be designed such that it matches the existing channel as closely as possible in regards to existing geomorphic conditions (e.g., channel slope and length, velocity, depth of flow, crosssectional geometry, channel sinuosity, energy dissipation, etc.). The existing channel geometry and physical characteristics should be established from reference reaches and idealized geometry. The reference reaches should be selected from stable channel reaches close to the relocated section or in locations with similar watershed and valley conditions. The relocated channel should be designed to duplicate the existing hydraulic properties for the bankfull design frequency. The flood clearance criteria given in Section 1005 should also be met. Additional information on the design of relocated channels can be found in the United States Department of Agriculture publication, Stream Corridor Restoration: Principles, Practices and Processes. The principals given in this publication utilize idealized channel geometry. The actual design should be refined using the channel geometry and physical characteristics of reference reaches Channel Linings and Bank Stabilization The use of soil bioengineering should be used to stabilize banks for relocated or impacted channels when practicable. Native plant species should be used when feasible. Bank stabilization using bioengineering is covered in the previously referenced USDA publication as well as the AASHTO Model Drainage Manual and the USDA Engineering Field Handbook, chapter 16, part 650. The design procedures and methods for determining the effectiveness of the traditional channel linings are covered in the Federal Highway Administration Hydraulic Engineering Circular No. 15 Design of Stable Channels with Flexible Linings. January

80 Drainage Design Procedures Ditch Design Criteria - Design Traffic Exceeding 2000 ADT Design Frequency Determine the depth of flow using a 10-year frequency storm, and determine the shear stress and width of the ditch lining (if required) using a 5-year frequency storm. Where a flexible ditch lining is required for calculated stresses exceeding the allowable for seed, the minimum width of the lining shall be 7.5 feet. Additional required width is in increments of 3.5 feet. The installed width of all ditch linings is centered on the flow line of the ditch. The depth of flow shall be limited to an elevation 1 foot below the edge of pavement for the design discharge. The depth of flow in toe of slope ditches shall be further limited such that the design year discharge does not overtop the ditch bank Ditch Protection The shear stress for the five-year frequency storm shall not exceed the values shown in Table for the various flexible linings. Table Permanent Protection Protective Lining Allowable Shear Stress (lbs/ft 2 ) Seed (659) 0.40 Sodding, Ditch Protection (660) Temporary Protection Ditch Erosion Protection Mat Type (670) 1.0 A 1.25 B 1.50 C 2.0 E 2.25 F 0.45 G 1.75 The temporary linings will reach a value of 1.0 psf upon vegetation establishment. Use the temporary lining shear stress values in Table on a temporary basis only (6 months or less). Calculate the actual shear stress by the following equation: ac = 62.4 D S Where: D = Water surface depth ft S = Channel slope ft/ft ac = Actual shear stress lbs/ft 2 If the calculated shear stress exceeds that shown in table then use the following permanent shear stress values within the stated limitations: 11-6 January 2018

81 Drainage Design Procedures A. Seeding and Erosion Control with Turf Reinforcing Mat (Supplemental Specification 836) where the ditch slope is 10% or less. Allowable shear stress for each type is as follows: Turf Reinforcing Mat Shear Stress Type Allowable Shear Stress (lbs/ft 2 ) B. Type B, C or D Rock Channel Protection may be used to line the ditch if the nearest point of the lining is outside the design clear zone or located behind guardrail or barrier. The actual shear stress is based upon the parameters of the channel slope and depth of flow for the 5-year discharge. The shear equation is valid for discharges less than 50 cfs with slopes less than 10%. Allowable shear stress for each type is as follows: RCP Shear Stress Type Allowable Shear Stress (lbs/ft 2 ) B 6 C 4 D 2 C. Type B or C RCP may be utilized for lining ditches on steep grades (slopes from 10%- 25%) that carry flow from the end of a cut section down to the valley floor. Use HEC-15 procedures with a safety factor of 1.5 for steep gradient channels (refer to HEC-15). Contact OHE for further guidance of RCP usage for 5-year discharges greater than or equal to 50 cfs. D. Tied concrete block mat protection (601) may be used for slopes and swales with 2:1 or flatter side slopes with profile grades at 25% or less. The matting may be used within the clear zone provided that the top of the blocks are flush with the finished grade. Install per the manufacturers recommendations. The allowable shear stress for each type is as follows: Tied Concrete Block Mat Shear Stress Type Allowable Shear Stress (lbs/ft 2 ) E. Articulating concrete block revetment system (601) may be used for slopes and channels with 2:1 or flatter side slopes. The revetment may be used within the clear zone provided that the top of the blocks are flush with the finished grade. Install per the manufacturers recommendations. The allowable shear stress for each type is as follows: Articulating Concrete Block Revetment System Shear Stress Type Allowable Shear Stress (lbs/ft 2 ) January

82 Drainage Design Procedures F. A concrete lining should be considered only as a last resort. Contact OHE, before using a concrete lining Roughness Suggested values for Manning s Roughness Coefficient n for the various types of open water carriers are listed in Table Catch Basin Types Table Manning s Roughness Coefficient Type of Lining n Bare Earth 0.02 Seeded 0.03 Sod 0.04 Item Concrete Bituminous Grouted Riprap 0.02 Tied Concrete Block Mat 0.03 Rock Channel Protection 0.06 for ditches 0.04 for large channels The Standard No. 4, 5, and 8 Catch Basins are suitable for the standard roadside designs covered in Volume I, Roadway Design. The tilt built into the basin top provides a self-cleaning feature when the basins are used on continuous grades and the wide bar spacing minimizes clogging possibilities, thereby resulting in an efficient design. The bases of the 4, 5 and 8 Catch Basins can be expanded to accommodate larger diameter conduits by specifying Standard Construction Drawing CB-3.4. The bar spacing can be decreased, when desirable for safety reasons, by specifying Grate E for the No. 4 and Grate B for the No. 5. Provide 150 feet of ditch erosion protection upstream of all No. 4, 5 and 8 Catch Basins, regardless of velocity. The following catch basin types are generally recommended based on the size and shape of the ditch. A. Standard No. 4 for depressed medians wider than 40 feet. B. Standard No. 5 for 40 foot radius roadside or median ditches. (Use Grate B where pedestrian traffic may be expected.) C. Standard No. 8 for 20 foot radius roadside or depressed medians 40 feet or less in width. D. Standard No. 2-2-A may be used in trapezoidal toe ditches where the basin is located in a rural area. The basin should also be located outside the design clear zone or behind guardrail where the protruding feature of the basin is not objectionable. The capacity of the side inlet catch basin window, for unsubmerged conditions, may be determined by the standard weir equation: Q = C L H 3/2 Where C is a weir coefficient, generally 3.0, L is the length of opening in feet, H is the distance from the bottom of the window to the surface of the design flow in feet. The catch basin grate is considered as an access point for the storm sewer and its capacity to admit flow is ignored for continuous grades. E. Standard No. 2-2-B should be used where minor, non-clogging flows are involved such as yard sections and the small triangular area created by the guardrail treatment for a depressed median at bridge terminals. Standard No. 2-3 through No. 2-6 catch basins should be provided where a larger base is 11-8 January 2018

83 Drainage Design Procedures required to accommodate pipes larger than 21 inches in span or sewer junctions, or where a No B catch basin will not provide adequate access to the sewer. F. In urban areas, Standard Side Ditch Inlets should be used to drain small areas of trapped water behind curbs and/or between driveways. For catch basin details refer to the Hydraulic Standard Construction Drawings at: px Calculated Catch Basin Spacing Catch basins must be provided to intercept flow from open water carriers when the depth of flow or velocity exceeds the maximum allowable for the design storm for all highway classifications. The standard ditch catch basins, designated Catch Basin No. 4, Catch Basin No. 5, and Catch Basin No. 8, include an earth dike. The dike is approximately 12 inches above the flowline of the grate, immediately downstream from the catch basin and serves to block the flow on continuous grades and create a sump condition. When the calculated depth of flow or velocity exceeds the maximum allowable at the checkpoint in the ditch, a catch basin or ditch lining will be required. However, the capacity of the catch basin may be less than the capacity of the ditch and thereby control the catch basin spacing. Figure may be used to check the capacity of a catch basin grate in a sump. To use Figure , the calculated discharge at the ditch checkpoint shall be doubled to compensate for possible partial clogging of the grate. In cut sections, the accumulated ditch flow shall be carried as far as the capacity, allowable depth, or velocity of flow will permit. The first catch basin in the roadside or median ditch will determine the need for a storm sewer system required for the remainder of the cut. Velocity control should be extended as far as inexpensive flexible ditch linings will permit. Consideration should also be given to providing positive outlets for underdrains and providing access to longitudinal sewer systems when locating ditch catch basins Arbitrary Maximum Catch Basin Spacing Catch basins are required at the low point of all sags and the earth dike noted in Section shall be omitted. The maximum distance between catch basins in depressed medians in fill sections shall be as follows: Depressed Median Catch Basin Spacing (Fill Sections) Median Width (ft) Desirable Spacing (ft) Maximum Spacing (ft) Where underdrains are utilized, catch basins shall be provided at a maximum spacing of 1000 feet (500 feet with free draining base) to provide a positive outlet for underdrains Ditch Design Criteria - Design Traffic of 2000 ADT or Less Design Frequency A 5-year frequency storm shall be used to determine the depth of flow, and a 2-year frequency to determine the shear stress of flow and width of ditch lining, where needed. The depth of flow shall be limited to an elevation 9 inches below the edge of pavement for the design discharge. The depth of flow in toe of slope ditches shall be further limited such that the design year discharge does not overtop the ditch bank. The minimum width of lining shall be in accordance with Section January

84 Drainage Design Procedures Shear Stress Protection Shear stress protection shall be in accordance with except that a 2-year frequency event shall be used Roughness The roughness used for the hydraulic analysis shall be based on the Manning's Roughness Coefficient values shown in Table Catch Basin Types Standard No. 5 Catch Basins, No. 2-2-A Catch Basin (within their safety limitations as discussed in Section (D)) and No. 2-2-B Catch Basins should be considered for the lower ADT highways. Standard No. 4 Catch Basins should be used where additional capacity is required. For catch basin details refer to the Hydraulic Standard Construction Drawings at: px Design Aids for Ditch Flow Analysis Earth Channel Charts Standard radius roadside ditch charts have been prepared, based on the Manning s equation, to facilitate the hydraulic analysis of ditch flow and are included in the Drainage Design Aids. Some of the more commonly used trapezoidal channel charts are also included. Other trapezoidal channel charts (with 2:1-2:1 side slopes and bottom widths varying from 2 feet to 20 feet are available in the Federal Highway Administration publication referenced in section All earth channel charts have been prepared using a Manning's Coefficient of Roughness of 0.03, which is recommended for a seed lining (Construction and Material Specifications Item 659). Q n and V n scales have been included on all channel charts so that the channel flow may be analyzed for any value of n depending on the roughness of the channel or lining Rectangular Channel Charts Vertical side channel charts that can be used to analyze the open channel flow in box culverts are included in the Federal Highway Administration publication Design Charts for Open Channel flow, previously referred to Pavement Drainage General When curbs are provided at the edge of pavement or paved shoulder, (primarily in urban areas), it is necessary to determine the proper type of pavement inlet (or catch basin) to control the spread of water and depth of flow on the pavement. Present day geometric design has resulted in relatively flat transverse and longitudinal pavement slopes. These slopes require more pavement inlets (or catch basins) and consequently result in an appreciable increase in the drainage cost. To alleviate the above, where curb is permissible, standard curb and gutter should be used adjacent to the pavement. On normal section multi-lane highways where three (3) or more lanes are sloped in the same direction, it is desirable to counter the resulting increase in flow depth by increasing the cross slope of the outermost lanes. The two (2) lanes adjacent to the crown line should be pitched at the normal slope of 1.6 percent, January 2018

85 Drainage Design Procedures and successive lane pairs or portions thereof outward, should be increased by 0.4 percent. Location and Design - Volume 1, Roadway design for additional geometric design criteria. Refer to If paved shoulders are provided, the drainage cost will be decreased appreciably due to the large volume of flow that can be carried on the pavement shoulder without exceeding the allowable depth of 1 inch below the top of curb or a maximum of 5 inches; a maximum depth of 6 inches is permissible where a barrier shape is provided adjacent to the pavement. Furnish a drainage design that will reduce the need for bridge scuppers by intercepting the flow prior to the bridge. A pavement drainage computation sheet similar to that provided in the Appendix shall be used to perform or summarize necessary computations. Additional information concerning pavement drainage can be obtained from the Federal Highway Administration Hydraulic Engineering Circular No. 22, "Urban Drainage Design Manual." Design Frequency Pavement inlets (or catch basins) shall be spaced to limit the spread of flow on the traveled lane (considered to be 12 feet wide) as shown in Table The allowable spread may be increased slightly for streets carrying predominantly local traffic and with design speeds less than 45 mph. Design shall be based upon the following frequencies: Facility Design (years) Freeways 10 High volume highways (Over 6000 ADT Rural or 9000 ADT Urban) All other Highways 2 For underpasses or other depressed roadways where ponded water can be removed only through the storm sewer system, the spread shall be checked for a 50-year storm for Freeways and high volume highways as defined above, and for a 25-year storm for other multiple lane highways. Typically, this criteria does not apply to 2-lane facilities. Contact OHE if encountered. The ponding will be permitted to cover all but one through lane of a multiple lane pavement. The depth of flow at the curb shall not exceed 1 inch below the top of the curb for the design discharge regardless of the type of highway. A maximum depth of 6 inches is permissible where a barrier shape is provided adjacent to the pavement. Facility Table Allowable Pavement Spread* (ft) Freeways 0 High Volume Highways (Over 6000 ADT Rural or 9000 ADT Urban) 45 mph 4 < 45mph 2 lanes 6 4 lanes 8 All other Highways 2 lanes 6 4 lanes 8 *Pavement spread applies to the through lane only January

86 Drainage Design Procedures Estimating Design Discharge Runoff contributing to curbed pavements shall be estimated by the rational method, as explained in Sections , and The time of concentration t c shall be the actual time of concentration calculated according to Section with an absolute minimum time of 10 minutes. In urban areas, where justifiable (e.g. contributing drainage area would be difficult to determine), the strip method may be used to determine contributing drainage areas. The strip method assumes a contributing drainage area of 150 feet taken on each side of the roadway centerline Capacity of Pavement Gutters A pavement gutter has a right triangular shape, with the curb forming the vertical leg and the straight pavement slope, the gutter plate of a curb and gutter, or a paved shoulder forming the hypotenuse. A standard curb and gutter adjacent to a straight pavement slope, or paved shoulder, forms a composite gutter section which complicates the flow analysis. In most cases, the top width of the water surface in a pavement gutter far exceeds the height of the curb. The hydraulic radius does not accurately describe the gutter cross section in this situation, thereby requiring a modification to the Manning s equation to analyze the gutter flow. The accepted modification results in the following equation: Where: Q = Discharge in cubic feet per second Z = Reciprocal of the pavement cross n = slope Manning s Coefficient of Roughness (Table ) s = Longitudinal pavement slope d = Depth of flow in gutter section at curb in feet Q = 0.56ZS1/2 d 8/3 n Figure provides a graphical solution for the above equation and its use is comparatively simple for straight transverse pavement slopes. However, the use of the Nomograph to determine depth of flow at the curb and resulting spread on the pavement for composite sections is much more involved Pavement Flow Charts Charts have been prepared for the more commonly used curbed pavement typical sections, and they are included in the Drainage Design Aids. The charts are particularly helpful for determining the flow for composite pavement sections where the spread can be read directly from the appropriate Pavement Flow Chart. To use the charts, enter with a predetermined design discharge (total flow) Q t in the gutter in cubic feet per second and proceed vertically to intersect the longitudinal gutter slope line. At that intersection, read the spread in feet shown on the diagonal spread lines. The spread of flow will generally control the pavement inlet or catch basin spacing, where the transverse and longitudinal slope of the pavement is relatively flat. The above is prevalent in long flat sag vertical curves, where a flanking inlet (or catch basin) should arbitrarily be provided on both sides of the low point in a pavement sag. This is particularly so for Freeways. Three inlets or catch basins in a sag can be justified only on the basis of need for other highway classifications. Usually a Standard 6 foot pavement inlet or No. 3A catch basin will be adequate, and they should be placed where the grade elevation is approximately 0.20 feet higher than at the low point. Furnish a CB-No. 3 at the sump January 2018

87 Drainage Design Procedures Inlets or catch basins should arbitrarily be placed upstream of all intersections, bridges and pedestrian ramps. When justified, inlets (or catch basins) should be located a minimum of 10 feet off drive aprons, intersection return radii, pedestrian ramps or curb termini Bypass Charts for Continuous Pavement Grades Bypass charts are included for the standard pavement inlets and catch basins in the Drainage Design Aids. Bypass for a given structure can be read directly from the chart (At the intersection of the spread, determined in Section , and the longitudinal gutter slope, read the bypass flow Q b on the abscissa). Experience has proven that, for greater efficiency, inlets should be sized to bypass a minimum of 10% to 15% of the design discharge. This criterion should be used to determine the type or length of inlet to be used in a given location. It is not intended to establish the required spacing. The most efficient design maintains the allowable spread on continuous grades and at the sag. The bypass for a catch basin or inlet should be added to the total flow in the adjacent downstream gutter section Curb Opening Inlets The flow bypassing a standard curb opening inlet, for pavement transverse slopes or combination of slopes differing from the charts included in the Drainage Design Aids, may be obtained from Figure The use of curb opening inlets should be avoided where bicycle traffic is expected Grate or Combination Grate and Curb Opening Inlet The standard pavement catch basin in this category is considered to intercept all the flow over the grate when used on continuous grades. A portion of the flow outside of the edge of the grate will also be intercepted, the amount varying with the depth of flow y along the edge of the grate. The depth y can be determined from Figure , and the resulting flow spilling over the edge of the grate from Figure , using a ½ inch local depression for straight transverse pavement slopes, or no local depression for a composite gutter section. The local depression mentioned above is at the front face of the grate closest to the centerline of the roadway. This depression is not the same depression identified in the in the standard construction drawings. The curb opening of a combination catch basin on a continuous grade will admit some flow, particularly if there is a partial clogging of the grate; however, the additional capacity should be considered as a factor of safety only. For inlet and catch basin details refer to the Hydraulic Standard Construction Drawings at: px Grate Catch Basins and Curb Opening Inlets in Pavement Sags The spread determined from the pavement flow charts need not be checked any closer than 25 to 50 feet on either side of the sag, well beyond the limits of the local depression. The spread in the sag should be determined from the depth of flow at the edge of grate using Figure and should include the total flow (contributions from each side of the sag vertical curve) reaching the inlet or catch basin. Standard No. 3 catch basins should be used in pavement sags. The capacity of the grates to admit flow is based on the depth of ponding around the grates. The capacity of the grates shown in Figure is based on weir flow over the edge of the grate, up to a depth of 0.4 feet. For greater depths, the total area of grate opening is considered, with no deduction made for possible clogging. When evaluating the spread in a depressed sag for a 25-year or 50-year event, the capacity of the window shall be considered. This capacity may be obtained from Figure The curb opening capacity should be added to the grate capacity for submerged conditions. Where the low point of a sag vertical curve occurs in a drive, a No. 6 catch basin should be provided at the low point with flanking No. 3A catch basins as per Section January

88 Drainage Design Procedures No. 6 catch basins may be used along curbed roadways and medians provided that the grate capacity is not exceeded. For inlet and catch basin details refer to the Hydraulic Standard Construction Drawings at: px Bridge Deck Drainage Furnish a minimum longitudinal grade of 0.3% for the bridge deck surface when using concrete parapets. Minimize or eliminate the number of scuppers. Calculate the allowable spread of flow using procedures described in Section On flatter longitudinal slopes, scuppers will intercept a portion of flow slightly wider than the width of the scupper (side flow), while on steeper longitudinal slopes, a portion of the flow in the gutter section occupied by the scupper (frontal flow) may splash over the grate. Assuming side capture and splash over are negligible, the frontal flow ratio is considered equal to the inlet efficiency. The fraction of flow captured by the scupper can be determined by the following equation: E = 1 ( 1 W T ) 2.67 Where: E = Scupper efficiency W = Width of scupper in feet T = Total width of spread in feet The scupper bypass flow can be determined by the following equation: Q b = Q(1 E) Where: Q b = Bypass discharge in cubic feet per second Q = Total discharge in gutter in cubic feet per second E = Scupper efficiency A spreadsheet to determine scupper bypass flow has been created and can be found on the Office of Hydraulic Engineering website at the following location: Use a computation sheet, similar to that provided in the link above to perform scupper calculations. Information concerning bridge deck drainage can be obtained from the Federal Highway Administration Hydraulic Engineering Circular No. 21, Design of Bridge Deck Drainage. Software utilizing methods outlined in HEC-21 are also acceptable for scupper analysis. Locate scuppers inside the fascia beam unless the parapet and beam spacing make this impractical. Furnish scuppers with vertical drops or nearly vertical drops when feasible. If a scupper pan is required, angle the pan as steeply as possible. Furnish an uncollected / free fall as per SCD GSD Substitute heavy duty cast iron deck drains as currently manufactured by Neenah or equal, when SCD GSD-1-96 will not physically fit due to parapet, beam line and the deck overhang. If a drainage collection system is required ensure that it meets the following: A. System is sloped greater than or equal to 15 degrees B. Bends have a minimum radius of 18 inches January 2018

89 Drainage Design Procedures C. Bends have angles greater than 90 degrees D. Cleanout plugs are easily and safely accessible E. Furnish drainage collection when using finger joints or sliding plates. Provide a neoprene drainage trough under finger joints. Show the necessary deck drainage outlet locations on the preliminary structure site plan. Include this information in the Structure Type Study (BDM 201). Place scuppers with drainage collection systems as close as feasible to the substructure unit which drains them. Place uncollected / free fall scupper downspouts as far away from any part of the structure as possible. See Section 1113 for bridge bypass flow Slotted Drains and Trench Drains Slotted and Trench drains are used to capture sheet flow in areas where curb is not present to collect and direct flow to a catch basin such as a gore area. Trench drains and slotted drain systems are susceptible to clogging and are not recommended where significant sediment or debris load is present. Locate trench drains and slotted drains longitudinally with the edge of pavement. Ensure the drain and any surrounding concrete is outside of the travelled way. Locate trench drains at the end of commercial drives to intercept large flows before entering into the travelled way. Outlet the slotted and trench drains to a Catch Basin No.6 to aid in cleanout. Furnish a Catch Basin No. 6 at minimum 100 ft. intervals for slotted drains and 200 ft. intervals for trench drains to facilitate cleanout. Refer to SCD DM-1.3 for slotted drain details. Furnish Plan Note D120 when utilizing slotted drain. Specify supplemental specification 839 and 939 when using trench drain. For slotted drain and catch basin details refer to the Hydraulic Standard Construction Drawings at: px 1104 Storm Sewers General Storm sewer systems are designed to collect and carry storm water runoff from the first pavement or ditch inlet, or catch basin to the predetermined outlet. (Further reference to inlets infers either inlets or catch basins). Long cut sections often result in the need for longitudinal trunk sewers to accept the flow from a series of inlets. The proper location of a sewer outlet is important. Existing drainage patterns should be perpetuated insofar as practicable. Careful consideration should be given to the possibility of actionable damage for the diversion of substantial volumes of flow. Long fill sections requiring median or pavement drains may best be served by transverse sewers that outlet independently at the toe of fill ditch. Storm sewer systems shall be sized to convey the current flow from areas naturally contributing to the highway or from intercepting existing storm sewers. Adherence to Local drainage criteria and standards is not applicable for ODOT owned and maintained drainage assets. Storm sewer systems may be oversized at the request of a local government entity to convey flow from areas beyond those considered highway responsibility or increased flows from anticipated development with the approval of the OHE. The additional cost to construct the increased sized storm sewer system will be the responsibility of the local government. January

90 Drainage Design Procedures The proration of project funds and local government funds will be determined from estimated construction costs. The project funding participation will be determined as a percentage of the total cost of the affected plan items. The percentage will be computed by dividing the estimated cost to construct a highway responsibility system only by the estimated cost to construct the oversized system. The affected plan items and participation percentage will be noted in the plan general summary. Type B conduit shall be specified for storm sewers under pavement, paved shoulders and commercial or industrial drives and Type C conduits for storm sewers beyond those limits. However, the type of conduit shall not be changed for a short run of conduit which would ordinarily require a change in conduit type. As an example of the above, Type B should be used for a transverse conduit that is required to drain an earth median catch basin in an embankment section under the pavement to a point approximately 10 feet from the embankment slope. A concrete collar, as per Standard Construction Drawing DM-1.1, should be provided to connect the Type B and a Type F Conduit, located back of, and parallel to, the embankment slope. Type F conduit, Type C or shall be provided for the pipe specials required to negotiate the bend at the top and bottom of the embankment. A detail is provided in Figure The Construction and Material Specifications stipulate the permissible pipe shapes and materials. Storm sewer designs will be based on round pipe, and the choice of the permissible material types for the conduit specified will be the contractor s option. When extending existing Type B & C conduits, the extensions will match the existing material in kind. The length of conduit to be paid for will be the actual number of linear feet, measured from center-to-center of appurtenant small structures. No deduction will be made for catch basins, inlets or manholes that are 6 feet or less across, measured in the direction of flow. Conduits placed on slopes steeper than 3:1 or with beveled or skewed ends are measured along the invert. Changes to grade may occur at existing manholes due to proposed work. With a decrease in grade of not more than 6 inches or an increase in grade of not more than 12 inches the existing structure may be Adjusted to Grade. Where grade elevation changes are greater, the existing structure should be Reconstructed to Grade. For examples of storm sewer detail sheets, reference Sample Plan Sheets and , maintained by the Office of CADD and Mapping. These provide a useful resource for preparation of hydraulic plans in terms of layout and content. For inlet and catch basin details refer to the Hydraulic Standard Construction Drawings at: px Design Considerations Storm Sewer Depth Keep a storm sewer system as shallow as possible, consistent with the following controls: A. Provide a minimum cover of 9 inches from the top of a rigid pipe to the bottom of the pavement subbase; however, in no installation shall the distance from the top of the rigid pipe to the pavement surface be less than 15 inches. Provide a minimum cover of at least 18 inches for pipe not under pavement. B. Provide a minimum cover of 12 from the top of flexible pipe to the bottom of the pavement subbase; however, in no installation shall the distance from the top of the flexible pipe to the pavement or ground surface be less than 24. C. Provide a minimum cover of 4 from the top of extra strength pipe to the bottom of the pavement subbase; however, in no installation shall the distance from the top of the extra strength pipe to the pavement surface be less than 10 inches. Provide a minimum cover of at least 4 if not under the pavement. If the minimum cover cannot be provided, check with OHE to determine the required extra strength January 2018

91 Drainage Design Procedures D. Provide a sufficient depth to permit the use of precast inlets, catch basins and manholes. Refer to the Standard Construction Drawings for this information. In no installation shall the top of pipe be in the precast top section of the inlet, catch basin or manhole. See Table for maximum storm sewer pipe thicknesses. E. Provide a sufficient depth to avoid interference with existing utilities such as sanitary sewers, the grade of which cannot be changed. F. Provide a sufficient depth to create a positive outlet for underdrains. It is desirable to maintain the underdrain outlet 12 inches above the flow line of the outlet structure with 6 inches as a minimum. G. Provide sufficient slope to maintain a minimum velocity of 3 feet per second, for self-cleansing. This velocity is calculated using the just full Manning s Equation. H. Match the crown of a smaller upstream pipe in a longitudinal trunk sewer to the crown of the adjacent downstream pipe. I. Minimum invert elevation = finished grade minimum cover wall thickness (per Table ) inside diameter Table Dimensions of Wall Thickness for Storm Sewer Outside Inside Diameter Wall Thickness Diameter (inch) (inch) (inch) /4 19-1/ / /4 26-1/ /4 33-1/ / / / / Where proposed highway storm sewers or ditches will interfere with existing private drains carrying treated or untreated sanitary flow, submit the names and addresses of the affected property owners to the District Deputy Director. Obtain the above information well in advance of the Field Drainage Review so the appropriate provisions of Directive No. 22-A can be followed (found in the Appendix A) Storm Sewer Access Most standard catch basins and pavement inlets will provide sufficient access to small shallow sewers. Catch basin or pavement inlets can be used to negotiate changes in sewer sizes or minor horizontal or vertical direction changes within the size limitation of the structure, but more pronounced changes may require manholes. January

92 Drainage Design Procedures It may be necessary, or desirable to locate longitudinal trunk sewers away from the curb to provide for a utility strip between the curb and the sidewalk and to avoid a conflict with the underdrain system. This will require properly spaced manholes in the sewer line. Small sewers (under 36 inches in diameter) located under or near the edge of pavement, should be accessible at intervals not to exceed 300 feet. For sewers sized 36 to 60 inches manholes should be spaced every 500 feet maximum. Manholes should be provided every 750 to 1000 feet maximum for larger sewers. For manhole, inlet and catch basin details refer to the Hydraulic Standard Construction Drawings at: px Rock Excavation for Storm Sewer If it is known that bedrock will be encountered in the excavation for storm sewer installation, relocate the storm sewer. If bedrock cannot be avoided, separate the quantities of the storm sewer in rock and include 611, As Per Plan in the plans Layout Procedure Plan A print of the plan sheets involved should be used to spot catch basins and inlets that are required to drain the project and satisfy maximum allowable depth and/or spread of flow. A strip map showing the delineated drainage area and topography is required. The map will provide the designer with a means of determining the drainage area and the weighted coefficient of runoff for the individual areas contributing flow to the required storm sewer system Profile A profile of the existing and proposed pavement or ground line over the proposed sewer location should be plotted. On the same profile, plot the locations of catch basins, inlets and manholes, along with a tentative storm sewer system Storm Sewer Design Criteria Design Frequency All storm sewers shall be sized to flow just full (i.e. depth of flow for maximum discharge) for a 10-year frequency storm. The size is determined by working downstream from the first sewer run. It will be acceptable to use a discharge of a more frequent occurrence if consistent with local criteria (depending upon the design ADT of the roadway) or to avoid extensive replacement of an existing downstream drainage system Hydraulic Grade Line Starting at the storm sewer system outlet and working upstream, the elevation of the hydraulic grade line at the upper end of each sewer run should be determined using a 25-year frequency. It will be acceptable to use a discharge of a more frequent occurrence if consistent with local criteria (depending upon the design ADT of the roadway) or to avoid extensive replacement of an existing downstream drainage system. Ordinarily, the hydraulic grade line will be above the top of the pipe, causing the system to operate under pressure. If, however, any run in the system does not flow full, (pipe slope steeper than the friction slope) the hydraulic grade line will follow the friction slope until it reaches the normal depth of flow in the steep run. From that point, the hydraulic grade line will coincide with the normal depth of flow until it reaches a run flatter than the friction slope for that run. The starting elevation for the hydraulic grade line determination should be the higher of either: the downstream tail water channel water surface elevation or (dc+d)/2 at the system outlet. Section January 2018

93 Drainage Design Procedures The intensity i in the rational equation Q=CiA [Q=CiA/360] used to determine the check discharge (25- year frequency) shall be the same for all sewer runs as that calculated for the last, or downstream run, in a continuous sewer system. The hydraulic grade line shall not exceed the following for any roadway with greater than 2000 ADT: A. 12 inches below the edge of pavement for sections without curb. B. The elevation of a curb opening inlet or grate elevation of a pavement catch basin. Consideration shall be given to a reduction in the design frequency and to more liberal hydraulic grade line controls for less important highways than those noted above. The check discharge, to determine the elevation of the hydraulic grade line for highways having depressed sags that must be drained by storm sewers, shall be based on a 50-year frequency. One directional lane of a multiple lane highway or one-half of a lane on a 2-lane highway should be passable when the sewer system is discharging the 50-year storm. Storm sewers for all highways shall satisfy a 50-year check to preclude flooding of buildings or extensive flooding of private property. If the hydraulic grade line exceeds the limits noted above, the controlling sewer size shall be increased. (These criteria are not intended to lower existing high water elevations) Coefficient of Runoff The weighted coefficient of runoff shall be determined as explained in Section Time of Concentration The time shall be determined as explained in Section A minimum time of concentration of 15 minutes to the first ditch catch basin and 10 minutes to the first pavement inlet shall be used. The actual calculated time of concentration shall be used when values greater than these minimums occur Pipe Roughness Coefficient A Manning s n of shall be used for sewers 60 inches in diameter and under, and for larger sewers. The basic n value for smooth pipe, concrete, vitrified clay, bituminous lined corrugated steel or thermoplastic is The increased values are recommended for sewers to compensate for minor head losses incurred at catch basins, inlets and manholes located in a storm sewer system Minimum Storm Sewer Pipe Size A minimum pipe diameter of 15 inches shall be used for Freeways and Freeway ramps (Where an existing storm sewer is to remain in service, it is not necessary to replace, hydraulically adequate pipes to meet this criterion) and 12 inches for other highways Maximum Storm Sewer Slope For storm sewers designated as Type B or Type C, the maximum slope is 25%. For storm sewers with slopes that exceed 25%, designate as Type F Hydraulic Design Procedure With the layout suggested in Section , start with the upper catch basin or inlet and determine the value of CA for the contributing flow (CA is the product of the weighted coefficient of runoff and the drainage area). Next, determine the time of concentration for the first area and the corresponding rainfall intensity i from the proper curve shown on Figure The design discharge Q to use to determine the January

94 Drainage Design Procedures required size of the first sewer from MH No. 1 to MH No. 2 is the product of Ca x i [0.0028CA x i]. At manhole No. 2, determine the value of CA for the additional area contributing at that point and add to the CA for MH No. 1. Compute the time of flow in the storm sewer from MH No.1 to MH No. 2 in minutes and add to the time of concentration at MH No. 1. Check the time of concentration for the area contributing to MH No. 2, and use the larger of the two as the duration for the new value of rainfall intensity for computing the design flow from MH No. 2 to MH No. 3. It is obvious that the process is quite involved, and a storm sewer computation sheet similar to that provided in the Appendix shall be used to tabulate the required information. The calculations for lateral connections to the longitudinal trunk sewer should be tabulated separately from the trunk sewer calculations. Software developed by ODOT (CDSS) is available online and can be used for these calculations. StormCAD may also be used for these calculations. Other software packages may be utilized with approval from OHE Combined Sanitary Sewer Separation When the Combined Sanitary Authority is under court order to address frequent overflow of the sanitary system due to storm sewer impacts, every effort should be made to furnish an exclusive outfall for the storm sewer when feasible. Coordination with the Local is required. While adherence to Local drainage standards is not applicable for ODOT owned and maintained drainage assets it may be possible for the Department to incorporate the needs of the local entity subject to review and approval of OHE. The Department will fund storm sewer conduit and drainage structures to ensure positive drainage of the roadway when a separation is feasible. Conduit and structures required for sanitary sewer will be funded by the Local. All conduit located outside of the Department owned right-of-way will be funded by the Local. Conduit will be furnished for the most feasible and direct route of storm or sanitary sewer as determined by the Department Roadway Culverts General A culvert generally carries a natural stream under the highway embankment. The culvert horizontal and vertical alignment should approximate that of the natural channel and thereby minimize stream impacts and the need for channel relocations. Ensure the upstream invert is not below the natural channel unless the culvert has depressed inverts, a paved depressed approach apron, or an improved inlet. Optimum culvert design (i.e., best hydraulic performance and least environmental impacts) occurs when the roadway alignment is normal to the flow in the channel and is located on a relatively straight and stable section of the channel. Roadway alignment needs to be considered early in the design process to provide optimum culvert design. The proposed roadway should avoid stream confluences. Culverts should not be placed on skews in excess of 45º or as further limited in Section Check the design with a single-cell round pipe as a first choice. In cases where required cover or discharge precludes a round pipe, select a shape that reduces the vertical requirements while maintaining the hydraulic capacity. Check the design with the following shapes in order of minimum cost to increasing cost: single-cell elliptical concrete, metal pipe-arch, prefabricated box culvert or three-sided structure. For justification of multiple cell culverts, see Section In general, maintain the existing upstream and downstream hydraulics when replacing an existing culvert. In cases where these parameters must be modified, evaluate any upstream and downstream impacts. Culvert location should perpetuate existing drainage patterns (depth of flow, direction of flow, overbank flow) to the maximum extent practicable. Diversion of substantial volumes of flow requires regulatory consideration and possible actionable damage January 2018

95 Drainage Design Procedures Label the depth or elevation of the Ordinary High Water Mark (OHWM) for jurisdictional waterways on the Culvert Detail Sheet for all culverts. The depth is measured from the centerline of the waterway. The OHWM is calculated per Section or determined by the Office of Environmental Services. For examples of culvert detail sheets, reference Sample Plan Sheets Section 1312 Drainage Details, maintained by the Office of CADD and Mapping. These provide a useful resource for preparation of hydraulic plans in terms of layout and content Stream Protection Stream protection practices are provided to improve stream channel stability. Erosion of the stream channel can migrate upstream and downstream without proper protection at the structure. Provide stream protection practices (water quantity treatment) for all culvert projects when the project earth disturbing acreage exceeds the thresholds for post-construction Best Management Practices (BMP) outlined in Section Exceptions for providing stream protection to meet post-construction BMP requirements are noted in Section In addition to post-construction BMP requirements, waterway permit conditions and site specific features may require the use of practices described throughout this Section. Stream protection for culvert projects is provided through the use of the following practices and is only applicable to grade control within Waters of the United States: Bankfull discharge design Depressed culvert inverts Paved depressed approach aprons Flood plain culverts Only the project areas that drain to a grade control structure will receive treatment credit. If the treatment provided by a grade control structure does not meet the required percentage of treatment, provide treatment in the areas not draining to the grade control structure for the remaining amount required. For existing culvert replacements, inspect the channel for erosion that has caused undercutting or downcutting at the inlet of the culvert. At locations with evidence of undercutting or downcutting, provide a concrete apron according to Section at the inlet and outlet of the culvert to restore previous stream elevations and provide stream protection. The use of each stream protection practice is limited based on project specific conditions. If the stream protection practices listed above are not applicable or available based on project type, site constraints or limitations, the project is not exempt from providing stream protection BMP. Other methods of stream protection must be used. In addition to the stream protection practices described within this Section, the following post-construction storm water BMP may be utilized within available right-of-way or right-of-way being obtained for roadway purposes to provide stream protection and treat storm water runoff when the project earth disturbed area is equal to or exceeds one acre: Extended Detention (See Section ) Retention Basin (See Section ) Bioretention Cell (See Section ) Infiltration Methods (See Section ) Constructed Wetlands (See Section ) See Sections 1115 through 1117 for further information concerning post-construction storm water BMPs. January

96 Drainage Design Procedures Bankfull Discharge Design Culverts utilizing Bankfull Discharge Design are required to convey the bankfull discharge with minimum change in the stream energy for the adjoining channel sections when compared to the existing conditions. The proposed culvert will minimize the impact to the stream channel by closely matching the existing depth of flow with the proposed depth of flow for the bankfull discharge in order to facilitate passage of aquatic organisms. Provide Bankfull Discharge Design for all culverts conveying intermittent and perennial streams with the following exception: The culvert is a replacement structure. In some cases when an individual waterway permit is required, this exemption may not apply because of minimization or mitigation requirements from the regulatory agencies. OES will coordinate this need with the District Environmental Coordinator or designer on a case by case basis. Information on stream flow regime can be found by contacting the District Environmental Coordinator or consulting the Ecological Survey Report located on EnviroNet: If multiple cell culverts are provided, ensure only one culvert conveys the bankfull discharge. Place the invert of additional culverts at the water surface elevation generated by the bankfull discharge. Use the following design steps when performing a bankfull discharge design: 1. Determine the bankfull discharge using USGS report , Bankfull Characteristics of Ohio Streams and Their Relation to Peak Streamflows. Use the regression equation that utilizes USGS map-based explanatory variables. The report can be obtained from USGS at: 2. Determine the culvert size from traditional culvert hydraulic design. 3. Depress the culvert invert according to Section Determine the depth of flow for the pre-developed channel using the bankfull discharge at locations 25 feet before the culvert inlet, at the culvert, and 25 feet beyond the culvert outlet. Determine the depth of flow for the bankfull discharge based on field-obtained stream cross-sections and the use of a standard step-backwater water-surface profile model such as HEC-RAS or the use of other software capable of calculating depth of flow based on Manning s equation. 5. Determine the depth of flow for the post-developed channel using the bankfull discharge at the same locations identified in Step 4 through use of a standard step-backwater water-surface profile model such as HEC-RAS or the use of other software capable of calculating depth of flow based on Manning s equation. The cross section at the culvert will reflect the geometry of the culvert. 6. Compare the depth of flow from step 4 to step 5. Adjust the culvert dimensions until the postdeveloped condition flow depth (Step 5) is approximately equal to the pre-developed flow depth (Step 4). 7. Add flood plain culverts if required (see section ). 8. Determine if the culvert meets the required hydraulic design controls. Upsize the culvert as required January 2018

97 Drainage Design Procedures Depressed Culvert Inverts Provide depressed inverts for all culverts designed to convey the Bankfull Discharge Design with the following exceptions: The culvert is located on bedrock The culvert slope exceeds 1% Depressed culvert inverts will produce a natural channel bottom within the culvert. The natural channel bottom provides a substrate for passage of migratory species. The depressed culvert will fill naturally, such that the channel bed in the culvert will be continuous with the adjacent channel sections. When practicable, install culverts at the existing streambed slope to allow for the natural movement of bedload and aquatic organisms. Verify that the culvert meets the required hydraulic design controls realizing that the portion of the culvert depressed will eventually fill with natural substrates. Upsize the culvert as required. End treatments for culverts with depressed inverts consist of Item 601 Riprap, 6 Reinforced Concrete Slab with a cutoff wall on both inlet and outlet ends. For details see Hydraulic Standard Construction Drawing DM-1.1 at: px Depress the culvert invert according to Table : Table Type A Conduit Invert Pipe Diameter or Rise (inch) Depression (inch) < 36 None > Modifications to the standard headwalls are not necessary for the depression depths noted above. Depressed inverts are not required for precast reinforced concrete three-sided flat-topped culverts with a natural channel bottom Paved Depressed Approach Aprons In many cases, the hydraulic operation of a culvert can be improved by depressing the flowline at the entrance below the channel flowline. The drop-down will alleviate a minimum cover condition, provide for additional headwater depth, and decrease the culvert outlet velocity by reducing the culvert slope. The abrupt change in natural channel slope is effected with a short length of concrete paving to prevent downcutting of the stream. The dimensions of the slab are site specific. However, for ease of construction, a 2:1 downslope should be used as the maximum descending slope. A 3-foot length of paving should be provided along the natural channel slope prior to the drop-down. A cut-off wall must be provided at the upstream end. In general, limit drop-down entrances to 4 feet, or one pipe diameter or rise, whichever is greater. January

98 Drainage Design Procedures The Federal Highway Administration has conducted extensive research and studies of paved depressed approach aprons, and recommended design procedures are included in Hydraulic Design Series No. 5, "Hydraulic Design of Highway Culverts." Flood Plain Culverts For all new bankfull culvert installations, consider the use of flood plain culverts. In wide flood plains, the installation of a new single culvert constricts the flow of water at the entrance section. The concentrated outflow from the culvert can initiate downstream channel degradation. Flood plain culverts can be used to minimize the effects of this new concentrated discharge by spreading the discharge throughout the flood plain or flood prone area on the outlet side of the culvert. Provide flood plain culverts when the flood plain width is greater than two (2) times the width produced by the bankfull discharge design. Flood plain culverts are installed adjacent to the single culvert. Place flood plain culvert inverts at the water surface elevation that is generated by the bankfull discharge design. Locate the flood plain culverts within the flood plain at a location well beyond the single culvert. Furnish a minimum of two flood plain culverts. Figure illustrates the location of flood plain culverts with respect to the bankfull channel and flood plain. Flood plain culverts are not hydraulically designed or accounted for in the hydraulic design of the single culvert. Use Figure ( other column) to determine the required diameter. The line and grade of the culvert should approximate that of the natural flood plain Energy Control Structures Provide energy control structures for all culverts with an outlet velocity greater than five feet per second. The use of energy control structures does not constitute water quantity treatment for post-construction BMP purposes. An energy control structure reduces the amount of erosive energy generated by a culvert. Use the following for an energy control structure: Broken-Back Culvert Rock Channel Protection Energy dissipator (Riprap Basin) Drop Structure Provide an energy dissipator when the outlet velocity exceeds the values shown in Figure Energy dissipaters create a forced hydraulic jump within the structure or immediately downstream of the structure, thus reducing the flow velocity. FHWA Hydraulic Engineering Circular No. 14 provides design guidance and procedures for various energy dissipators. A riprap basin is the most cost effective energy dissipator. Contact OHE prior to using an energy dissipator Types of Culvert Flow Laboratory tests sponsored by the FHWA have established two general types of culvert flow: (1) flow with inlet control, or (2) flow with outlet control. Nomographs have been prepared for use in the determination of culvert headwater for the appropriate control. Under inlet control, the headwater HWI is directly related to the cross-sectional area of the culvert barrel and the inlet geometry. Under outlet control, the headwater HWO is further influenced by tailwater depth in the outlet channel and the slope, length and roughness of the culvert barrel. As shown in Figure , culverts operate with a free water surface if the headwater is equal to or less than 1.2D, and with a submerged entrance if the headwater is greater than 1.2D, where D is the diameter or rise of the pipe January 2018

99 Drainage Design Procedures Design Procedure General The design of a culvert involves a determination of the appropriate design and check discharges. The process begins with a delineation of the drainage area, in acres [hectares], on a suitable topographic map. The design discharge Q for most culvert drainage areas will be obtained by procedures described in Section of this manual. The Rational method should be used to obtain the discharge from small and other unusual drainage areas as noted in Section A representative cross-section of the embankment at the proposed culvert site, along with a profile of the natural stream or ground line, will be required to determine the approximate length and slope of the culvert Hydraulic Analysis The hydraulic analysis of a culvert, including a determination of the headwater depth and outlet velocity for the design discharge, is simplified by the use of Pipe Flow Charts and the headwater and head nomographs noted in Section The charts are included with the Drainage Design Aids, beginning with Figure To preclude the need for a determination of the probable type of flow under which a culvert will operate for a given set of conditions, the headwater depths may be computed using the nomographs for both inlet and outlet control. The size of pipe is then selected by using the control giving the higher headwater limitation. The relationship of the headwater to the diameter or height of the culvert HW/D is read directly from the inlet control nomograph and the HWI equals that value multiplied by D. HWO is computed by the equation HWO=H+ho - SoL.;/ The loss of head H is read from the flowing-full nomograph and the tailwater depth ho, is the greater of either the normal depth of flow in the outlet channel or the depth as flow passes through the outlet of the pipe, calculated as (dc+d)/2. D is the diameter or rise of the culvert and dc is the critical depth of flow which may be read from the critical depth curve shown on each Pipe Flow Chart. The above procedure is reasonably accurate for the majority of culvert flow conditions. For culverts operating with outlet control (see Figure , Class 1-A and 1-B), where the calculated headwater (using the appropriate nomograph) is less than 0.75D, a backwater analysis can be justified and is recommended. A culvert analysis sheet similar to that provided in the Appendix shall be used to tabulate all the pertinent factors required to determine the controlling headwater for each culvert type being considered for a given location. The analysis sheet includes other information valuable to the reviewer and it is to be included with other supporting data for required review submissions. Hydraulic analysis of culverts may also be performed utilizing the Federal Highway Administration Hydraulic Design Series No. 5, Hydraulic Design of Highway Culverts. Computer programs such as FHWA HY-8 or ODOT s CDSS software package may be used. CDSS may be downloaded from the Hydraulics website. For replacement projects, an analysis of the existing structure shall be performed. Use the same analysis method when comparing the existing and proposed structures. For bridge replacements, the acceptable method of hydraulic analysis is HEC-RAS Use of Nomographs Outlet Control To determine the loss of head H for a given concrete pipe culvert with a grove-end entrance and discharge Q, proceed as follows: By straight line, connect culvert size with k e =0.2 (length scale) and obtain a point on the turning line. Connect the turning line point with the computed discharge Q and read the head loss H. Follow the same procedure for a corrugated metal pipe except using k e =0.9 (length scale). The k e January

100 Drainage Design Procedures value for additional shapes can be found in the Federal Highway Administration publication referenced in Section Should the roughness coefficient n of the proposed pipe differ from that shown on the chart, adjust the measured culvert length by the length factor given on Design Aid Figure For an example, see Drainage Design Aid Figure The Federal Highway Administration publication referenced in Section offers nomographs for culvert shapes not available in the Drainage Design Aids. Their use is recommended for special culvert shapes Inlet Control To determine the headwater HW for a given discharge Q, size and type of culvert, proceed as follows using appropriate Figures , (Drainage Design Aids). Use Figure for a round corrugated metal pipe culvert and Figure for a round smooth-lined pipe culvert. By a straight line, connect the culvert size with the discharge Q, extend a diagonal line to Scale (1) and thence by horizontal line to Scale (3). Based on a groove-end entrance and a Standard HW-2.1 headwall recommended for concrete pipe culverts, the HW/D relationship is obtained by an average of the (2) and (3) Scale values. Follow the same procedure for a corrugated metal pipe with a Standard HW-2.2 headwall, where HW/D is the average values read from Scales (1) and (3). Use Scale (2) for the HW/D relationship for concrete box culverts Design Criteria Design Frequency The design frequency shall be as stated in Section It should be noted that a Flood Hazard Evaluation using a check discharge based on the 100-year flood frequency shall be made for all culverts as noted in Section Maximum Allowable Headwater See Section Method Used to Estimate Storm Discharge See Sections 1003 and Scale of Topographic Mapping Used to Delineate Contributing Drainage Areas See Section Manning s Roughness Coefficient n The n values for corrugated metal pipe are given in Figure The n value for all smooth flow pipe is Use a weighted Manning s n for bankfull designed culverts or analyzing older culverts with sediment deposition Entrance Loss Coefficient k e See Table or Appendix D of Federal Highway Hydraulic Design Series No. 5, "Hydraulic Design of Roadway Culverts January 2018

101 Drainage Design Procedures Table Type A Conduit Entrance Loss Coefficient k e Type of Pipe Full Headwall Type One-Half None Concrete, Vitrified (thick wall) * Corrugated Metal (thin wall) 0.25** * groove end entrance ** beveled entrance Plastic conduits without a welded bell inlet will be designed as a corrugated metal conduit. Plastic conduits with a welded bell inlet will be designed as a concrete conduit. In both cases, the Manning s n value for plastic is Minimum Cover See Section Maximum Cover See Section Maximum Allowable Outlet Velocity See Figure Headwall Type See Section Contacts With County Engineer Contact the County Engineer at the beginning of the design process to review the proposed location, both horizontal and vertical, in order to ascertain ditch cleanout grades. Use Form LD-33 (available in the Appendix) to document approval Minimum Pipe Size As specified in Section Ordinary High Water Mark Determine the elevation and lateral extents of the OHWM following the USACE RGL No Special Considerations The following are special conditions that will be encountered in the hydraulic design of culverts that warrant clarification. Apply appropriate stream protection practices as described in Section when using special design considerations. January

102 Drainage Design Procedures Tailwater Tailwater at a culvert outlet can greatly affect the size of culvert required at a specific site. For this reason a proper evaluation shall be made of the outlet channel so that a reasonable estimate of the tailwater can be calculated. A determination of the normal depth of flow in the outlet channel, when the culvert is discharging the design flow, normally establishes the culvert tailwater. A close examination of the downstream channel may however, reveal a temporary or permanent obstruction that will control the operation of the culvert. In some cases, the culvert will outlet near a river or other fluctuating water surface stream that could control its operation. Where that drainage area of the culvert is very much less than the receiving watercourse (i.e. 100 times) the effect of the receiving watercourse generally may be disregarded. Where the drainage areas of the culvert and receiving watercourse are nearly equal, concurrent flood peaks may be assumed. Where there is a significant, but not excessive, difference in the drainage area of the culvert and receiving stream, the following design procedure should be used and the culvert sized using the combination that results in the highest headwater. A. Compute the culvert headwater using the proper design frequency for the culvert and a lesser frequency for the receiving stream water surface elevation (i.e. culvert tailwater elevation) depending upon the difference in drainage areas; say a 25-year culvert and a 10-year stream. B. Use 10-year frequency for the culvert and 25-year for the stream. In some locations, a high tailwater will control the operation of a culvert to such an extent that a substantial increase in pipe size will be required for a negligible decrease in the headwater elevation. For this case, the culvert size should be based on a practical tailwater elevation (e.g. [dc+d]/2) Multiple Cell Culverts A single-cell culvert should be the designer s first choice within practical limitations. Occasionally, low headwater requirements, high fills, or bankfull design will create the need for multiple cells. For these cases, it is desirable to limit the number of cells to two. Experience has proven that multiple cells well aligned with a relatively straight channel, will operate satisfactory. However, a bend in the immediate upstream channel may cause the inside cell to collect debris during normal periods of runoff and thereby substantially reduce the capacity of the culvert Improved Inlets Consider improved inlets attached to the entrance end of the culvert to reduce headwater or culvert size. The improved inlet will alleviate a minimum cover condition and provide for additional headwater depth. Culverts on relatively steep slopes and controlled by inlet control can see a reduction in the culvert size by furnishing an improved inlet. Consider the following two general types of inlets in the following order: A. Side-taper - A tapered end section from a round to an oval shape for a pipe, or a square to a rectangular shape for a prefabricated box. The length of the taper section is usually made 1.5 times the diameter or rise of the culvert January 2018

103 Drainage Design Procedures B. Slope-taper - A combination of side-taper preceded by a drop in the culvert flow line. The drop can be similar to a paved drop-down entrance or a more sophisticated reinforced concrete drop provided by a formed cast-in-place section with vertical sides. The improved inlet has the advantage of admitting more flow and thereby tending to fill the culvert barrel and reduce the culvert outlet velocity. The savings in culvert cost must justify the additional cost of the improved inlet. The Federal Highway Administration has conducted extensive research and studies of improved inlets, and recommended design procedures are included in Hydraulic Engineering Circular No. 13, "Hydraulic Design of Improved Inlets for Culverts." 1106 End Treatments General Headwalls, or other approved end finishes, shall be provided at the open ends of all Type A, B and C conduits. Headwalls should also be provided for Type D conduits greater than 24 inches in diameter or rise. Generally, headwalls are not recommended for Type E and F conduits. In order to reduce the entrance loss in culverts, the bell end should be located upstream and the spigot end should be located downstream. Details shown in the plan should convey this to the Contractor when necessary. Figures and show typical end details for a concrete box culvert Usage The selection of the headwall type is based on safety and economics. Standard HW-2.1 and 2.2 half-height headwalls are recommended for round, elliptical, or pipe arch culverts where a clear zone is provided. Full height headwalls should be provided where a significant reduction in culvert length can be realized with foreslopes flatter than 2:1 or where right-of-way limits the culvert length. Provide full-height headwalls for prefabricated box culverts and three-sided structures. The use of special end treatments may be required by Section of Volume 1, Roadway Design. Details are available from the Office of Hydraulic Engineering. Justification for the use of this type of end treatment shall accompany the request for details. Miter-cut (step-bevel) end sections, when required, shall be shown on the Culvert Detail Sheet. When half-height headwalls are provided, they should be built perpendicular to the end of the conduit to eliminate the need for a skew cut. In addition to the required headwall, the upper, or exposed, half of conduits having a diameter or rise greater than or equal to 126 inches shall be miter-cut (step-bevel) to fit the embankment slope End Treatment Grading The prevailing embankment slope shall be projected to the back edge of the top of the headwall to establish the required culvert length as shown in Figure When the roadway foreslopes are flatter than 2:1, a 2:1 slope shall be provided from the back edge of the top of the headwall to a minimum of 1 foot, with 2 feet, above the top of the culvert. The change in embankment slope shall be warped on each side of the conduit to fit the prevailing slope. In no case shall the distance from the pavement edge to the point where the embankment slope changes to 2:1 be less than the design clear zone width (see Section 601, Volume 1, Roadway Design) unless guardrail is provided. Clear zone grading should only be provided at culverts when the requirements of Section of Volume 1, Roadway Design are met. January

104 Drainage Design Procedures The prevailing embankment slope shall be warped on either side of a skewed culvert to assure equivalent soil loading and proper side support of the pipe. This is especially true for flexible pipes with large skews and/or large diameters Headwall Types Half-Height Headwalls If the size of the conduit exceeds that shown in the Standard Construction Drawing HW-2.1 and HW-2.2 tables, the dimensions shown in the tables may be expanded to accommodate the larger size conduits. Payment for half-height headwalls shall be on a cubic yard basis for Item 602, Concrete Masonry. Masonry quantities for standard half-height headwalls may be obtained from the appropriate standard construction drawing. The quantity of concrete masonry provided in the plans shall be based on the pipe alternate requiring the largest quantity of concrete masonry. Refer to the Bridge Standard Construction Drawings at: ings.aspx Full-Height Headwalls The appropriate full-height headwall for round pipes shown on Standard Construction Drawing HW-1.1 may be considered at the entrance end, when the savings in the reduced size and length of the conduit will offset the additional cost of the headwall. This will most likely apply where corrugated steel pipe is specified, due to cover or size requirements, and the bevel provided for the full-height headwall will substantially reduce the entrance loss. Dimensions of full-height headwalls may be expanded to accommodate pipe sizes larger than 84 inches. Refer to the Bridge Standard Construction Drawings at: ings.aspx Design full-height headwalls for box, 3-sided and arch culverts per Section 300 of the Bridge Design Manual and the latest AASHTO LRFD Bridge Design Specifications. Payment for non-standard full-height headwalls is on a cubic yard basis for Item 511 and pounds of Item 509. Subdivide the quantities for nonstandard full-height headwalls in to quantities for headwalls, wingwalls and footers and add plan note D118 to the plans. Include appropriate plan notes from Section 600 of the Bridge Design Manual in the project plans. An investigation of the supporting foundation material shall be conducted and the bearing resistance of the foundation material estimated. The level of detail required for the foundation investigation shall be commensurate with the importance of the structure. Such information shall be submitted for all proposed full-height headwall installations and submitted with the Stage 1 review. The inlet wingwall footings of full-height headwalls shall be armored with Type B rock channel protection, with filter, to preclude scour. Refer to the Bridge Plan Insert Sheets at: px Concrete Apron Provide a reinforced concrete riprap cutoff wall, as shown on Standard Construction Drawings DM-1.1 when the depth of the rock channel protection (if necessary), including the 6 inch granular filter, exceeds the depth of the headwall January 2018

105 Drainage Design Procedures For details see Hydraulic Standard Construction Drawing DM-1.1 at: px Provide concrete riprap at the inlet end of the culvert where the existing culvert has been undercut. Concrete riprap shall be in accordance with Section Concrete riprap is not necessary at the inlet of culverts with full height headwalls that have a footing toe extending 3.5 feet or more below proposed channel grade Rock Channel Protection (RCP) General RCP is used to control erosion and as a scour countermeasure. It is used at the outlet of culverts and storm sewers, or for lining ditches on steep grades. It is used as a scour countermeasure at wingwalls of fullheight headwalls, along footings of 3-sided structures, corner cones, and under bridges Culvert RCP Types There are four types of RCP that are used in various situations. The use of the proper type at culvert and storm sewer outlets can be determined from Figure Type A is generally used beyond the outlet of the larger conduits having outlet velocities in excess of 12 feet per second and Type B and C for conduits having an aggregate filter where the protected slope is steeper than 3:1. A filter should always be specified to prevent soil piping through the rock. A geotextile fabric is appropriate in most cases. An aggregate filter should be used when the RCP is under water. The cost of the filter is included in the unit bid price for Item 601 Rock Channel Protection with Filter Bridge RCP Furnish RCP armor for bridges over waterways at the following locations: A. The entire spill-through slope B. Front side of abutments and wingwalls C. Corner cones Use the following table to determine the Type of RCP to use: Channel Mean Velocity (ft/s) RCP Type Thickness (inch) 0-8 C B 2-6 above 10 A 3-0 Special circumstances such as protection on the outside of curves or in northern regions of the state on pooled water where ice flow is a concern may require greater rock thickness. Show on the Site Plan the locations, length, and the top of slope elevations for the RCP. Show the RCP in greater detail in the roadway section in conjunction with the channel plans. It is more economical to provide bank protection during the initial construction in order to provide sufficient embankment protection to minimize future maintenance. Limit stream channel excavation to that portion of the channel one foot above normal water elevation in order to minimize intrusion and to preserve the natural low water channel. January

106 Drainage Design Procedures 1108 Agricultural Drainage Farm Drain Crossings Where it is necessary to continue an existing farm drain crossing under the highway, the pipe shall be Type B Conduit, one commercial size larger than the existing farm drain within the right-of-way limits. Occasionally, it will be desirable to provide a farm drain crossing under a highway on new location to satisfy the future need for adequate farm drainage. It is recognized that the required length of a Type B Conduit will provide a betterment for the property owner, but it does preclude the need for a much more expensive crossing after the highway is built. Such a crossing is considered a blind and the cost of the installation, including suitable terminal markings at the right-of-way lines, will generally not be eligible for federal participation Farm Drain Outlets Existing farm drains that outlet through the backslope of the roadway ditch shall terminate with a minimum length of 10 feet of equivalent size Type F conduit. When outletting existing plastic farm drains, one size larger Type F conduit shall be used. An Animal Guard and Erosion Control Pad as shown on Standard Construction Drawing DM-1.1 shall be provided. For details see Hydraulic Standard Construction Drawing DM-1.1 at: px To provide for possible sedimentation, the invert of the Type F conduit shall be a minimum of 6 inches, with 12 inches being desirable, above the ditch flow line Longitudinal Sewer Location Under Pavement Longitudinal sewers will not be permitted under the pavement of a limited or controlled access facility. Also, the length of transverse sewers under pavements shall be held to a minimum, with the objective of having no manholes in the pavement. Contact OHE if this cannot be accommodated to discuss a possible resolution. For other facilities, storm sewers should be located outside the limits of the pavement. However, in locations where this would create conflicts with existing utilities (e.g. waterlines, sanitary sewers, gas lines, etc.) the storm sewer may be located under the pavement. Care should be taken to avoid placing manholes in vehicle wheel-paths or within an intersection. Place the center of the manhole in the lane when feasible. Where an out-to-out clearance of 5 feet cannot be provided between parallel storm and sanitary sewers, premium joints shall be provided on the storm sewer Under Paved Shoulder The above shall also apply to paved shoulder areas, unless it is determined that the cost of any other possible location is prohibitive Approval Exceptions to the above shall be submitted in the early stages of the design to the Office of Hydraulic Engineering for review and approval January 2018

107 Drainage Design Procedures 1110 Reinforced Concrete Radius Pipe and Box Sections General To comply with the capabilities of manufacturers to provide satisfactory and economical radius pipe or box sections, a minimum radius of 100 feet shall be specified. The method of manufacturing the radius pipe or box sections will be an option of the producer, subject to inspection and approval by the Ohio Department of Transportation, Office of Materials Management. As an alternate to radius pipe, pipe specials may be specified to negotiate the specified radius, provided they do not reduce the hydraulic performance established by the initial design. The bends shall be located so that they shall closely follow the alignment of the radius pipe Sanitary Sewers General Any sanitary sewer, whether new or relocated, shall be constructed using resilient and flexible gasket joints, in accordance with Construction and Material Specification for circular concrete pipe or for clay pipe. Permissible thermoplastic pipes shall also be specified. Discharges of treated sanitary flow from abutting property into highway drainage systems are only permitted if the discharge is authorized by the Local Health Department Manholes All new manholes for sanitary sewer lines shall be built in accordance with the Standard Construction Drawings. Precast manholes shall have joints in accordance with of the Construction and Material Specifications Notice of Intent (NOI) General A NOI is a one-page application form for requesting coverage under a National Pollutant Discharge Elimination System (NPDES) general permit for storm water discharges from Ohio EPA. The applicant(s) must certify their intention to comply with the NPDES general permit by submitting a NOI. Submit a NOI for all projects where combined Contractor and Project Earth Disturbing Activity (EDA) are one acre or more. In addition, when the combined Project and estimated Contractor EDA are just less than one acre, the project designer may choose to increase the estimated Contractor EDA to avoid the possibility of work on the project being initiated without a NOI. Earth disturbing activity is defined as any activity that exposes bare ground or an erodible material to storm water and anywhere Item 659 Seeding, or Item 660 Sodding is being furnished. An area where pavement is being removed to the sub-grade is considered earth disturbing activity, except for isolated repairs. Routine Maintenance Projects, as defined by Section , do not require a NOI. The Total Earth Disturbing Activity acreage, which includes the Project Earth Disturbing Activity acreage (earth disturbed area within the project construction limits) and the Contractor Earth Disturbing Activity acreage such as: field offices, batch plants, and borrow/waste pits, shall be estimated. The location and size of the Contractor Activities can be estimated using the NOI Acreage Calculation Form (Figure ). Non-contiguous portions of projects sold under one contract, such as multiple culvert replacements, may be treated as separate projects for the purposes of obtaining an NOI. If the project sites are located ¼ mile January

108 Drainage Design Procedures or more apart and the areas between the activities are not being disturbed, the sites can be considered separate. If each site is below the project earth disturbed area threshold of one acre of EDA, no postconstruction BMP or NOI will be required. If one or more individual sites meet the project earth disturbed area thresholds, an NOI is required for the project sites that exceed the EDA threshold. The NOI application should reflect the Project and Contractor EDA for all project sites that exceed the threshold. Postconstruction BMPs will be required only at the individual project sites that exceed the Project EDA threshold. Non-contiguous multiple part projects (i.e. Part 1/Part 2) sold as one project should be evaluated with respect to each Part. Parts that meet the definition in Section for Routine Maintenance Projects or have a project EDA under one acre do not need to be included in the disturbed acreage calculations for determining the need for a NOI or post-construction BMP. Post-construction BMPs will be required only for individual parts that exceed the Project EDA threshold. Follow standard NOI procedures for a Project Part with routine maintenance activities exceeding five acres or a Project Part that includes construction (nonroutine maintenance) activities. For projects where all runoff is collected in a combined sewer, a NOI is not required. However, coordination with the agency responsible for the receiving treatment plant is required. Prepare a Project Site Plan as required by Location and Design, Volume 3, Section 1308 for all projects that require a NOI or post construction BMPs Routine Maintenance Project For the purposes of submitting for coverage under a NPDES permit, a Routine Maintenance Project is one in which all of the Project Earth Disturbing Activities are routine operations that do not change the line, grade, or the hydraulic capacity of the facility and involve total earth disturbing activities of less than 5 acres. Permanent erosion control items shall be included in the plans, if required. Routine maintenance projects do not require a NOI. Projects with five or more acres of total earth disturbed area cannot be classified as Routine Maintenance Projects. The following activities are considered routine maintenance activities: Abutment Repairs - repairs to bridge abutments Bridge Deck Overlays - replacing the wearing surface on bridges Bridge Deck Replacement - replacing the entire deck on bridge Chip Sealing - placing asphalt or polymer binder and stone on existing paved roadways Fence Repair / Replacement - repairing or replacing existing fencing and/or posts Lighting Maintenance Loop Detector Repairs - repairing loop detectors in existing pavement Pothole Filling Tree/brush Removal Signal Installation / Maintenance - installing / repairing / replacing traffic signals and poles where previous ones existed Signing Maintenance - repairing / replacing traffic signs and posts Noise Wall Repair Full Depth Pavement Repairs - isolated repairs of pavement build-up down to subgrade (potholes, utilities) Partial Depth Pavement Repairs - isolated repairs of surface courses of pavement Linear Grading - reshaping of graded shoulders to establish proper drainage away from pavement Berm Repair or Topsoil placement along shoulders - placing berm material or topsoil on shoulders adjacent to pavement to eliminate drop-offs. Ditch Cleanout - maintaining or restoring original flow line and cross-section only January 2018

109 Drainage Design Procedures Guardrail Installation / Replacement - installing / repairing with minor grading work to create proper grade for end assemblies where previous guardrail existed. Culvert Replacement - replacing a culvert with same line, grade and hydraulic capacity; must be within parameters of the USAC Nationwide Permit #3. Culvert Repair / Lining - repairing or lining existing culvert maintaining same line, grade and hydraulic capacity, must be within parameters of the USAC Nationwide Permit #3 Resurfacing - replacing several inches of asphalt wearing course by milling existing asphalt and replacing with new. Curb Repairs - repairing existing curbing along a roadway. Sidewalk replacement of sidewalk without other drainage or roadway improvements. Isolated slide repairs. Post construction storm water best management practices are not required for routine maintenance projects Watershed Specific NOI Requirements Additional requirements for projects located in certain designated watersheds are required by Ohio EPA. These projects require coverage under an Ohio EPA watershed specific NPDES permit. Coordinate projects in the following watersheds with Central Office Office of Hydraulic Engineering: Big Darby Creek (entire watershed) Olentangy River (portion of watershed as regulated under permit number OHC200002) In addition to post-construction BMP requirements, watershed specific NPDES permits include the following requirements: Groundwater Recharge Mitigation, if applicable Riparian Setback Mitigation Temporary Sediment Basin Locations Ohio EPA review and approval of the Storm Water Pollution Prevention Plan (SWPPP) Provide groundwater recharge calculations, riparian setback calculations, and temporary sediment basin locations to Central Office Office of Hydraulic Engineering with the BMP submittals as outlined in Section Groundwater recharge calculations and riparian setback calculations shall be based on impacts outside the existing roadway right-of-way. Determine the riparian setback limits according to the Permit and identify the setback limits on the Project Site Plan. Mitigation for groundwater and riparian setback will be determined through coordination between the District, Central Office Office of Hydraulic Engineering and Ohio EPA prior to submittal of the NOI application. Determine soil types required for groundwater recharge calculations using the NRCS Web Soil Survey website. While sediment basin locations are typically provided by the Contractor, designers of projects being developed under watershed specific NPDES permits shall identify locations with capacity to store sediment volumes required by these permits. The location and calculations for the sediment basins shall be shown on the Project Site Plan. Additional temporary sediment and erosion control features will be added to the SWPPP by the Contractor. Submit the NOI, Project Site Plan, proposed mitigation and supplemental calculations to the Ohio EPA at least two months prior to plan package submittal to ensure that there are no delays. January

110 Drainage Design Procedures 1113 Erosion Control at Bridge Ends General Collect and carry bridge deck drainage that flows off the ends of the bridge in accordance to the following: A. Flow less than 0.75 ft3/s or for bridges without MSE walls Furnish a flume, as shown on Standard Construction Drawing DM-4.1, B. Flows greater than 0.75 ft3/s or bridges without MSE walls - Furnish an integral curb provided on the approach slab with a standard catch basin located off the approach. Include a bridge terminal assembly at the trailing end of bridge barrier. Use a Catch Basin No. 3A, as shown on Standard Construction Drawing CB-2.2. Provide Type F conduit ( Type C) for an outlet down the embankment slope and armor the outlet to prevent erosion. For catch basin details refer to the Hydraulic Standard Construction Drawings at: s.aspx C. Bridges with MSE Walls Furnish a barrier on the approach slab with a standard inlet basin. Locate the inlet a minimum of 25 feet beyond the limits of MSE wall soil reinforcement. Continue the barrier a minimum of 10 feet past the inlet Corner Cone Place Item 670 Slope Erosion on all bridge approach embankment corner cones, beginning at the edge of the crushed aggregate or concrete slope protection Temporary Sediment and Erosion Control General Temporary sediment and erosion control is required on all projects that have Earth Disturbing Activities as outlined in Supplemental Specification 832. A Storm Water Pollution Prevention Plan (SWPPP) is required as outlined in SS 832. Projects that may have environmental impacts to habitat or species may also be required to prepare a SWPPP as determined by the District Environmental Coordinator. The SWPPP requirements are outlined in Supplemental Specification Cost Estimate for Temporary Sediment and Erosion Control For all projects that require temporary sediment and erosion control furnish a dollar amount to be encumbered in the final plan package. Use the temporary sediment and erosion control estimator located in the Design Reference Resource Center to develop this amount Post Construction Storm Water Structural Best Management Practices General Post Construction Storm Water Best Management Practices (BMP) are provided for perpetual management of storm water runoff quality and quantity so that a receiving stream s physical, chemical and biological characteristics are protected and stream functions are maintained January 2018

111 Drainage Design Procedures BMPs are required per the Ohio EPA s NPDES permit(s), which include the Construction General permits and the Municipal Separate Storm Sewer System (MS4) permits. Two variants of the MS4 permit are possible depending on the population size of the entity seeking coverage as follows: Small MS4 Entities that have populations less than 100,000 within urbanized areas. Individual MS4 Entities that have population in excess of 100,000. Several categories exist under the individual MS4 permit. Local entities that administer a small or individual MS4 permit may have more restrictive language regarding selection and use of BMPs as compared to the Department. Storm water discharge from ODOT right-ofway is permitted under the OEPA Small MS4 permit that is obtained by the Department. While the local entity cannot force the Department to use their standards, it may be possible for the Department to incorporate the needs of the local entity subject to review and approval of OHE. BMP, as described in Section 1117, shall meet permit compliance for Ohio EPA s NPDES General Permits. For ODOT projects, any proposed alternative BMPs that are not found in Section 1117 require submittal to ODOT Central Office Office of Hydraulic Engineering. A review and approval of the alternative BMP by ODOT Central Office Office of Hydraulic Engineering and Ohio EPA is required. Local-Let Local Public Agency projects may use an alternative post-construction BMP criteria with Ohio EPA approval. Post-construction BMP remove pollutants from runoff (water quality treatment) and protect streams by attempting to maintain existing stream conditions or by reducing runoff volumes through structural BMP (water quantity treatment). Locate BMPs so that they are protected in accordance with Location and Design Manual, Volume Project Thresholds for Post-Construction BMP Post-construction BMP are required through Ohio EPA s NPDES Construction General Permit for construction storm water discharges. The requirements to provide post-construction BMP established in the NPDES General Permit are based on Project Earth Disturbing Activities. If a NOI is not required (Section 1112), then post construction BMPs are not needed. Project Earth Disturbing Activity (EDA) is defined as any activity that exposes bare ground or an erodible material to storm water or anywhere Item 659 Seeding, Item 660 Sodding is being furnished. An area where pavement is being removed to the sub-grade is considered earth disturbing activity, except for isolated repairs. Requirements based on project EDA for non-routine maintenance projects are listed below: Table Project Earth Disturbed Area Thresholds EDA < 1 acre - BMP not required. EDA 1 - BMP are required. Routine Maintenance Projects as defined in Section do not require post-construction BMP. Provide post-construction BMP for all projects exceeding the project EDA thresholds in Table For projects requiring post-construction BMP, the following items require evaluation: Need for Water Quantity and Quality Treatment vs. just Water Quality Treatment(Section ) What is the Project Type Redevelopment or New Construction (Section ) If New Construction, calculate the Treatment Percent (Section ) January

112 Drainage Design Procedures Project-wide or site specific implementation of BMPs to reach the required treatment (Section ) Applicable BMP to be implemented (Section 1117) All projects, including Local Public Agency projects (ODOT-let and Local-Let) are required to provide postconstruction BMP as indicated in Table Projects with post-construction BMP require coordination with LPAs when BMPs are required outside ODOT right-of-way. Inform the LPA of maintenance responsibilities associated with post-construction BMP. Non-contiguous portions of projects sold under one contract that do not require an NOI, as described in Section , do not require post-construction BMP Water Quality and Water Quantity Treatment Projects exceeding the minimum thresholds in Section must address water quality (pollutant removal) and potentially water quantity (stream protection/volume control) post-construction BMP. BMPs to address water quantity are not required for projects that meet any of the following criteria: Redevelopment projects as defined in Section New Construction Projects as defined in Section where one or less acre of new impervious area is created in new permanent right-of-way area being acquired for the project. Portions of New Construction Projects (as defined in Section ) which discharge directly to a large river (>100 square mile drainage area or fourth order or greater) or to a lake and where the development area is less than 5 percent of the watershed area upstream of the development site, unless known water quality problems exist in the receiving waters. Only the project areas that drain to a large river or lake will be excluded from the requirement to provide quantity treatment. If portions of a project discharge to smaller waterbodies, quantity treatment may still be required for those portions. If there is a question regarding the stream classification, contact Central Office - Office of Hydraulic Engineering. Projects may not be subdivided into multiple NOIs for the sole purpose of attempting to reduce post construction treatment requirements. A map of stream classifications can be found at ODOT s TIMS website: Click HUC - Stream Order to view stream layers. BMPs that treat water quality and water quantity include: Extended Detention Retention Basin Bioretention Cell Infiltration Trench Infiltration Basin Constructed Wetlands BMPs that treat only water quality include: Manufactured Systems Vegetated Biofilter Vegetated Filter Strip January 2018

113 Drainage Design Procedures BMPs that treat only water quantity and must be paired with a water quality BMP include: Stream grade control structures (within Waters of the U.S.) Underground Extended Detention Water Quality Volume Water quality volume is directly used to determine sizing for the following BMP: Extended Detention Retention Basin Infiltration Trench Infiltration Basin Constructed Wetlands The water quality volume (WQ v ) is used to define the amount of storm water runoff from any given storm that should be captured and treated in order to remove a majority of storm water pollutants on an average annual basis. The following equation shall be used to calculate the water quality volume: Where: WQ v = Water Quality Volume (Acre-feet) P = Precipitation (0.75 inches) A = Contributing Drainage Area (acres) Cq = 0.858i i i (see figure ) i = impervious area divided by the total area Cq = 0.9 when all drainage area is impervious Water Quality Flow WQ v = (P*A*Cq)/12 Use water quality flow to determine sizing for manufactured systems and vegetated biofilters. The water quality flow (WQ f ) is the discharge that is produced by using an intensity of 0.65 in/hr in the rational equation (section ). Use the entire contributing drainage for the WQ f calculation Project Type - Redevelopment and New Construction Redevelopment Projects Redevelopment projects include: Projects constrained entirely within existing right-of-way, or Projects that do not add new impervious area in new permanent right-of-way While all areas within existing ODOT right-of-way may not be covered by impervious surfaces, the area within existing ODOT right-of-way is considered impervious area for the purpose of post-construction BMP design considerations. Therefore, consider all area within existing right-of-way to be impervious with a runoff coefficient of 0.90 when performing post-construction BMP calculations. January

114 Drainage Design Procedures New Construction Projects Projects that add new impervious area inside new permanent right-of-way are considered new construction projects. New construction projects allow for the reduction of treatment requirements based on the amount of new impervious area relative to the existing impervious area within the project EDA (See Section ). Consider all area within existing ODOT right-of-way to be impervious for post construction BMP calculations Pedestrian Facilities and Shared Use Paths For Redevelopment Projects or New Construction Projects that include EDA only associated with pedestrian facilities and shared use paths, with no EDA from planned roadway improvements, narrow Vegetated Filter Strips are an acceptable post-construction BMP (as discussed in Section ). For these projects, quantity treatment (as discussed in Section ) is not required Treatment Requirements for Projects The amount of treatment required for a project to meet the NPDS Permit requirements is based on the project earth disturbed area and the weighted average for new and existing impervious area. Use a Treatment Percentage (T%) of 20% for redevelopment projects. Determine the Treatment Percent for New Construction projects using the following equation: T% = [(Aix * 20)+(Ain * 100)] / (Aix+Ain) Where: T% = Treatment percent (Percentage) Aix = Project EDA that is inside the existing right of way Ain = Inside new permanent right of way, Ain is the new impervious area minus any impervious area that is removed Consider all area within existing ODOT right-of-way to be impervious for post-construction BMP calculations. Area draining to a post-construction BMP will earn treatment credit equal to the amount of ODOT right-ofway area treated by the BMP. Projects utilizing BMPs designed based on WQ v or WQ f require treatment according to one of the following: Provide T% treatment of the WQ v or WQ f for 100% of the project earth disturbed area Provide 100% treatment of the WQ v or WQ f for T% of the project earth disturbed area Projects utilizing Vegetated Biofilters, Vegetated Filter Strips and Bioretention Cells require treatment as follows: Provide 100% treatment of the contributing drainage area for T% of the project earth disturbed area in a specified portion of the project. For example, a redevelopment project with 10 acres of project EDA may provide treatment through the use of a vegetated biofilter with 2 acres of contributing drainage area. The vegetated biofilter design would be based on the contributing drainage area to the ditch of 2 acres January 2018

115 Drainage Design Procedures For all scenarios, size the BMP based on the entire contributing drainage area, offsite and on-site, to the BMP. When providing treatment based on a percentage of the project earth disturbed area, consider the following: Credit for water quality and water quantity treatment is only applied to the portion of the contributing drainage area within ODOT right-of-way (on-site). Any offsite contributing drainage area must be included in the BMP calculations for sizing purposes (i.e. width of ditch, etc.). However, the offsite area will not be included in the reduction of the required amount of project EDA that requires treatment. Example: A vegetated biofilter that has offsite contributing drainage area of one acre and on-site contributing drainage area of two acres (total drainage area of three acres) would result in a treatment credit of two acres. The vegetated biofilter must be sized for the total contributing drainage area of three acres. Multiple areas of a project may provide treatment to meet the total area required for compliance with the NPDES Permit. If the total area requiring treatment in this example was four acres, another vegetated biofilter with a minimum of two acres of on-site tributary area would be needed to meet the treatment requirements. For projects with multiple distinct stream crossings that do not immediately share a common confluence downstream, provide post-construction BMP treatment proportional to the amount of Project EDA tributary to each stream. If there is an existing post-construction BMP that treats runoff from the project site, and the BMP is sized appropriately to manage runoff from T% of the Project EDA, then additional BMPs are not required to meet post-construction treatment requirements. Include the existing post-construction BMP in the Project Site Plan. Include calculations demonstrating the BMP s capacity to manage runoff from the project site as well as any other existing sources of runoff into the BMP in the BMP submittal described in Section Example: A large new roadway project is constructed and 100% of the project EDA drains to a post-construction BMP. If a future portion of this roadway is redeveloped, and that area already drains to an existing BMP, no new BMPs would be required to meet post-construction treatment requirements. Example: A large highway redevelopment project (100 acres) is constructed and 20% of the project EDA (20 acres) drains to various post-construction BMPs. A future redevelopment project has a project EDA of 10 acres within the original 100-acre project. The treatment requirement for the future project is 2 acres. If at least 2 acres of the future project drains to existing post-construction BMPs, then no new BMPs would be required to meet post-construction treatment requirements. If the future project is planned for a section of the roadway where BMPs were not implemented in the original project, then new BMPs are required that ensure a minimum of 2 acres of the future project drain to a BMP BMP Selection and Submittals BMP Selection Selection of BMP shall be based on providing maximum runoff treatment while minimizing impacts to the remaining project design features, including utilities and right-of-way. In addition, each BMP option comes with unique maintenance requirements. Contact the Office of Maintenance Administration for detailed BMP maintenance information. January

116 Drainage Design Procedures Approval from Ohio EPA is required to use alternative BMPs not listed in Section Alternative methods will be approved or denied on a case-by-case basis if the alternative methods are demonstrated to sufficiently protect the overall integrity of the receiving streams and the watershed. For curbed roadways, total contributing drainage areas to sumps or intersections that are less than or equal to 0.25 acres as shown in figure do not require a BMP. Note that these exceptions are unique circumstances. Provide BMP as necessary for all other project features. For projects where the drainage sheet flows off the roadway and continues outside existing or proposed right-of-way, do not channelize flow for the sole purpose of providing a post-construction BMP. Treatment is not required for areas where sheet flow off the roadway continues to sheet flow outside ODOT right-ofway. Areas where this occurs should be documented in the post-construction BMP calculations and identified on the Project Site Plan. Design criteria for all BMP are available in Section A flow chart to determine BMP treatment requirements is provided in Figure BMP Submittals Consider BMPs early in the design process to allow for right-of-way and utility coordination as well as evaluation with respect to waterway permitting issues. For PDP projects characterized as Paths 4 and 5, provide a description of the planned BMPs to be used for the project in the Preliminary Engineering Phase (PE). Final BMP design is required during Stage 1 plan development as identified in later tasks of the Preliminary Engineering Phase. Further refinement may be needed within the Environmental Engineering Phase. For projects categorized as Paths 1-3, it is unlikely a conceptual BMP task will be needed. Include BMPs in the Environmental Engineering Phase and potentially the Final Engineering Phase of the PDP. Submit the BMP final design during Stage 1 to ODOT Central Office Office of Hydraulics. Include the following information: Estimated Project Earth Disturbed Area Treatment Percent Calculation or justification that project is a Redevelopment Project. BMP selected for use Drainage area mapping for post-construction BMP s that show the total contributing drainage area and the amount of contributing drainage area within ODOT right-of-way. Plan sheets showing locations of post-construction BMP Calculations for each BMP (Sec. 1117) Explanation for any area that is not treated (i.e. environmental commitment, total parcel take, environmental resource impact, sheet flow runoff, etc.) The following design resources are available on the ODOT, Office of Hydraulic Engineering s website: x Post-Construction BMP Design Review Checklist BMP Calculation Spreadsheet Post-Construction BMP Design Examples Post-Construction BMP Training Workshop Slides Identify the final locations and EDA treatment credit of each individual post-construction BMP in the Project Site Plan as described in Section 1308 of Location and Design Manual, Volume 3. If applicable, provide cross-references to sheets showing post-construction BMP details on the Project Site Plan January 2018

117 Drainage Design Procedures 1117 BMP Toolbox Manufactured Systems Manufactured systems consist of underground structures that treat the water quality flow (WQ f ) by removing particulate matter through settlement or filtration. Supplemental Specifications 895 and 995 cover the material and performance criteria for these devices. They are placed in an off-line configuration with manholes to allow for routine maintenance procedures (see figure ). Use the following procedure for design of manufactured systems: A. Determine the total contributing drainage area. B. Calculate the WQ f according to Section C. If appropriate, reduce the WQ f according to Section D. Provide a No. 3 Manhole, With Base ID and Weir where flow is to be diverted to the off-line manufactured system according to Table and and the calculated WQ f. Type WQ f (cfs) Table Manufactured Systems No. 3 Manhole Base ID (inches) 611 Type B Conduit Diameter (inches) Reserve an area (as measured from the centerline of the No. 3 Manhole) according to Table : Table Reserved Area for Manufactured System Type 611 Type B Weir Width Length Total Height (ft) (ft) Conduit (inches) Length (ft) E. Furnish two lengths of 611, Type B Conduit placed perpendicular to the inflowing sewer (see Table for the total length required). F. Reserve an area (as measured from the centerline of the No. 3 Manhole) according to Table If this area is not attainable, contact Central Office Office of Hydraulic Engineering for further guidance. Ensure the area is void of all utilities and is accessible for routine cleanout and maintenance. For manufactured systems located along a roadway with a posted speed limit over 45 mph, locate the area for the manufactured system outside all paved areas. January

118 Drainage Design Procedures For manufactured systems located along a roadway with a posted speed limit of 45 mph and less, it is preferred to locate the area for the manufactured system outside paved areas. If it is not feasible to locate the area outside of the paved area, select another BMP or contact Central Office Office of Hydraulic Engineering for further coordination. When a manufactured system is connected to a storm sewer with a depth exceeding 10 feet, contact Central Office Office of Hydraulic Engineering. Manufactured systems are typically not suited for treatment of flows in large trunk sewers. As indicated in Table , manufactured systems should not typically be provided on sewers that are carrying a water quality flow greater than 6 cfs. The water quality flow calculation is based on the entire contributing drainage area to the storm sewer. Add Item 895, Manufactured Water Quality Structure, Type to the plans when using a manufactured system. Label the location and EDA treatment credit on the Project Site Plan for each manufactured system on the project Vegetation Based BMP Vegetated Filter Strip A Vegetated Filter Strip is a BMP that filters storm water through vegetation. The Vegetated Filter Strip consists of the grassed portion of the graded shoulder and the grassed foreslope. The Vegetated Filter Strip must be void of gullies or concentrated flow. The water flow is characterized as overland flow throughout the grass. The minimum Vegetated Filter Strip required is defined in Table below. The Vegetated Filter Strip can start at the end of the graded shoulder or at any point on the slope. Areas (pavement, graded shoulder, or any grass slope) that drain to a Vegetated Filter Strip receive treatment credit including the Vegetated Filter Strip area. Maximum Pavement Width (ft) Table Slope (H:V) Filter Strip Width (ft minimum) 22 3:1 and flatter :1 and flatter :1 and flatter :1 and flatter :1 and flatter :1 and flatter :1 and flatter :1 and flatter 25 The Vegetated Filter Strip width is measured down the grass slope starting at the grass and ending at the inside edge of the ditch bottom. Any area associated with concentrated flows that outlet to a Vegetated Filter Strip should not be included in the treatment credit January 2018

119 Drainage Design Procedures For projects that include EDA only associated with pedestrian facilities and shared use paths, with no EDA from planned roadway improvements, widths of Vegetated Filter Strips are allowed to be narrower than those in Table Vegetated Filter Strips are an acceptable post-construction BMP for these projects provided the following criteria are met: The minimum Vegetated Filter Strip width is equal to the width of the contributing impervious area. The maximum slope of the Vegetated Filter Strip is 3:1. All runoff must be sheet flow, with no concentrated flows to the Vegetated Filter Strip. Example 1: A project includes the addition of 4-foot wide sidewalk along a road to the extent that the project EDA is greater than 1 acre, but no roadway improvements are included. That project may incorporate 4-foot wide Vegetated Filter Strip collecting runoff from the sidewalk in order to meet its post-construction treatment requirements. Example 2: A project includes the addition of a 10-foot wide bike path, but no roadway improvements are included in the project. The project may incorporate 10-foot wide Vegetated Filter Strip collecting runoff from the bike path in order to meet its post-construction treatment requirements. Similarly to standard Vegetated Filter Strip, treatment credit for narrow Vegetated Filter Strip will be given to the impervious area draining to the filter strip as well as the area of the filter strip itself. Projects that have EDA from a combination of pedestrian facilities or shared use path as well as roadway improvements may not utilize Vegetated Filter Strip narrower than those shown in Table without project-specific permission from Ohio EPA. Label the station range and location, and the EDA treatment credit on the Project Site Plan for each Vegetated Filter Strip provided on the project. Add 4 of Item 659, Topsoil, to the grass portion of the shoulder and foreslope of the Vegetated Filter Strip. Add Item 670, Slope Erosion Protection, to the plans when using Vegetated Filter Strip Vegetated Biofilter If the Vegetated Filter Strips will not provide the required treatment, consider using a Vegetated Biofilter. A Vegetated Biofilter (VBF) is a BMP that filters storm water through vegetation and potential infiltration. The Vegetated Biofilter consists of the grassed portion of the graded shoulder, grassed foreslope, and flat grassed ditch. The purpose of the Vegetated Biofilter is to allow runoff to spread out and move slowly through a shallow, flat, and grassed conveyance. Vegetated Biofilter must be void of rills, gullies, or visible erosion on the grassed foreslope of the ditch as well as in the bottom of the ditch. When widening existing ditches, consider the following before purchasing new right-of-way: Provide a steeper ditch foreslope. Provide a steeper ditch backslope. Reducing the bench width to a minimum of 4 feet. Consider soil conditions and safety issues prior to making any of the above changes to the existing slopes or benches. Changes to existing ditches may be regulated through waterway permits since ditches may be considered streams or wetlands. All impacts to existing streams and wetlands should be avoided or minimized to the maximum extent practicable. To determine if the proposed ditch will impact an existing stream or wetland, contact the District Environmental Coordinator. January

120 Drainage Design Procedures For projects utilizing the vegetated biofilter, provide a ditch width using the Enhanced Bankfull Width (EBW) or Standard ditch width to provide water quality treatment. Use the following steps to determine the ditch width: A. Determine Enhanced Bankfull Width (EBW): The EBW is the width in a trapezoidal ditch for which the following criteria are met: The minimum EBW is 4 feet. The depth of flow for the water quality flow rate (WQ f ) is less than or equal to 4 inches. The velocity of flow for the water quality flow rate (WQ f ) is less than or equal to 1 ft/sec. Use the water quality flow rate (WQ f ) per section Use Manning s Equation to determine the depth and velocity of flow: Manning s Equation: Q = n AR 3 2 S Where: Q = flow rate (cfs) n = Manning s Roughness Coefficient (0.15) A = Cross section area of flow (ft 2 ) R = Hydraulic Radius (ft) (Area / Wetted Perimeter) S = Longitudinal Slope of ditch (ft/ft) There is not a direct calculation to determine EBW. Use a trial and error method to determine a width for which the depth and velocity criteria are met for the WQ f, assuming open channel flow. The EBW should be whole numbers only, no half-foot increments. The enhanced bankfull width corresponds to the dimension of the bottom width of the trapezoidal ditch. B. Determine Standard Ditch Width: Determine the size of the trapezoidal ditch that would typically be specified for the project without accounting for water quality treatment (use typical roadway design practices). Use the bottom width dimension of the trapezoidal ditch. Ignore any rounding lengths associated with the trapezoidal ditch. C. Determine the vegetated biofilter ditch width required for water quality treatment as described below: 1. If the EBW is less than or equal to the Standard ditch width, furnish the Standard ditch. 2. If the EBW is greater than the Standard width, furnish the EBW. The EBW can be calculated at multiple locations along its length. This would allow the width to be reduced where there is less tributary area (i.e. the upstream area of the ditch). However, use the entire contributing drainage area to the location in the ditch being evaluated to determine the EBW. At points where concentrated offsite runoff is accepted, the EBW should be recalculated. Treatment credit for Vegetated Biofilter is given to: 1. Areas within the project limits that sheet flow off of the roadway into a grassed shoulder, grassed foreslope, and then into a grassed trapezoidal ditch sized as described above. (Tributary areas to a Vegetated Biofilter that do not meet this criteria, i.e. drainage from concentrated flow or outside project limits, must be included in the determination of the EBW, but do not receive treatment credit.) January 2018

121 Drainage Design Procedures 2. The area of the defined Vegetated Biofilter (the shoulder, foreslope, ditch bottom, and backslope) within the permanent right-of-way. Ensure that rock or other impervious soil layers will not prevent grass from being established at the invert of the flowline. If the velocity is such that rock channel protection, reinforced concrete mats, or SS836 are required, that section of the ditch cannot be used as a Vegetated Biofilter. Use of Vegetated Biofilter with grassed foreslopes steeper than 3:1 must be coordinated with the District Maintenance department to ensure that maintenance of is feasible. Constriction points in the enhanced bankfull width at drive pipes or other drainage related features are acceptable. A transition back to the calculated width shall be made immediately following the constriction point. Label the station range and location, and EDA treatment credit on the Project Site Plan for each Vegetated Biofilter provided on the project. Add 4 of Item 659, Topsoil, to the grass portion of the shoulder and foreslope of the Vegetated Biofilter. Add Item 670, Ditch Erosion Protection, to the plans when using Vegetated Biofilter. Size the width of ditch erosion protection consistent with Section , using the width for the 5-year frequency storm. The minimum width of lining shall be 7.5 feet. Additional required width is in increments of 3.5 feet Extended Detention Extended detention is a method that captures storm water during rain events and slowly releases the captured volume over a period of time. The WQv is used to determine the storage volume of the detention basin. The WQv is discharged over a 48 hour time frame. Increase the WQv by 20% when sizing the BMP to allow for sedimentation to occur. Detention can be either above or below ground. Detention basins that are above ground should be used when feasible. However, when project site parameters dictate, an underground system may be considered. Due to the safety considerations and potential impacts to the drainage system, the use of extended detention BMPs requires approval from the Office of Hydraulic Engineering. Provide submittals according to Section Extended Detention BMPs with more than one foot of ponding water are not to be located in the clear zone without prior approval from the Office of Roadway Engineering Detention Basin A detention basin is a dry pond that detains storm water for quality and quantity. Use the following procedure for design of the detention basin: A. Calculate the WQv per Section B. Calculate the Design Check Peak Discharge per Section C. Increase the calculated WQv by 20% to determine the required size of the detention basin. D. Provide a forebay (settling pool located at the inlet to the basin) that is 10% of the WQ V (located according to Figure ), if feasible. The forebay volume is part of the required volume, and is not an additional volume requirement. E. Provide a micropool (settling pool located at the outlet of the basin) that is 10% of the WQ V, if feasible. The micropool volume is part of the required volume, and is not an additional volume requirement. January

122 Drainage Design Procedures F. Size the water quality basin (outlet structure) for proper discharge of the WQv and the weir for proper discharge of events up to the design check discharge according to Section Ensure that the water surface elevations created by the basin are considered in the design of the upstream drainage system. G. Provide anti-seep collars for the outlet pipe according to Section The following criteria apply when designing a detention basin: A. Use side slopes of 4:1 (max) B. Consider vehicle access to the basin for periodic maintenance. C. Do not locate on uncompacted fill or steep slopes (2:1 or more) or where infiltrating ground water could adversely impact slope stability. D. Vegetate the sides of the basin with Item 670 Slope Erosion Protection. E. Embankment work to create the impoundment will be constructed and paid for as Item 203 Embankment, Using Natural Soils, A. F. Furnish gravel pack protection at the outlet structure (see SCD WQ1.1). G. Place channel protection (RCP or Tied Concrete Block Mat) at the entrance of the basin to minimize erosion and sediment resuspension. H. Furnish a Water Quality Basin, Detention per section I. Label the location and EDA treatment credit on the Project Site Plan for each extended detention basin on the project Water Quality Basin and Weir Furnish an outlet structure that fully drains the WQ v in 48 hours or more. No more than 50% of the WQ v should be released from the detention basin in less than one-third the drain time (i.e. 16 hours). The outlet structure consists of a catch basin with a perforated riser pipe on the inlet side and a conduit on the outlet side. The perforated riser pipe is used for flow control to achieve the required discharge time. A gravel envelope surrounds the perforated riser pipe along the inlet side of the catch basin to prevent blockage of the orifice holes in the pipe. The catch basin and riser pipe are paid for as Item 611, Water Quality Basin, Detention. Details of a perforated riser pipe outlet structure can be found on Standard Construction Drawing WQ-1.1 found at: px The equation for a single orifice is: Q A C 64.4H Where: A = Area of orifice (ft 2 ) H = Head on orifice as measured to the centerline of the orifice (ft) C = Orifice coefficient January 2018

123 Drainage Design Procedures C Table Orifice Coefficient Guidance Description Use for thin materials where the thickness is equal to or less than the orifice diameter. Use when the material is thicker than the orifice diameter. From CALTRANS, Storm Water Quality Handbooks, Project Planning and Design Guide, September Furnish a weir to allow the design check discharge to bypass the structure without damage to the detention basin or embankment of the basin. The design check discharge shall be determined per Ensure that the weir is protected from erosion. A hydrograph curve for the outlet will be required to calculate the discharge time of the WQv and the design check discharge (see ). The discharge time should correspond to the minimum drain time of 48 hours with no more than 50% of the WQ v being released from the detention basin in less than one-third of that 48 hour drain time. Generally, it is easier to model the outlet structure and discharge time using software such as Pond Pak or HydroCad to develop the hydrograph Anti-Seep Collar Design Furnish anti-seep collars on conduits through earth fills where water is being detained. The following criteria apply to anti-seep collars: A. Furnish a minimum of 2 collars per outlet conduit. Increase the seepage length along the conduit by a minimum of 15%. This percentage is based on the length of the pipe in the saturation zone. B. Anti-seep collars should be placed equally within the saturation zone. Place one collar at the end of the saturation zone. In cases where the spacing limit will not allow this, place at least one collar within the saturation zone. C. Maximum collar spacing should be 14 times the minimum projection above the pipe, but not more than 25 feet. The minimum collar spacing should be 5 times the minimum projection, but not less than 10 feet. D. Extend the collar dimensions a minimum of 2 feet in all directions around the outside of the conduit, measured perpendicular to the conduit. Center the anti-seep collars around the conduit. E. The top of collar shall not be less than 6 inches below, measured normal to, the finished ground line. F. All anti-seep collars and their connections shall be watertight. G. Minimum thickness shall be 6 inches. H. Payment for the collar shall be Item 602 Concrete Masonry, refer to Standard Construction Drawing WQ-1.2 at: s.aspx The design procedure for anti-seep collars is as follows: January

124 Drainage Design Procedures 1. Determine the length of the conduit within the saturated zone. The assumed normal saturation zone can be determined by projecting a line through the embankment, with a 4:1 (H:V) slope, from the point where the normal water elevation (10-year) meets the upstream slope to a point where it intersects the invert of the conduit. This line, referred to as the phreatic line, represents the upper surface of the zone of saturation within the embankment (See Figure ). The 10-year storm pool elevation is the phreatic line starting elevation. L s = Y(Z+4)[1+S/(0.25-S)] Where: L s = Length of the conduit in the saturated zone (feet) Y = Depth of the water at the spillway crest, 10-year frequency storm water surface elevation (feet) Z = Slope of the upstream face of the embankment (Z feet horizontal to 1 foot vertical) S = Slope of the conduit (feet per foot) 2. Determine the required seepage length increase. L s = 0.15L s 3. Choose a collar height and width that is at least 4 feet larger than the outside diameter of the conduit (minimum projection of 2 feet from all sides of the conduit). Give collar sizes in one foot increments. P = W D Where: P = Projection of collar (feet) W = Height or width of collar (feet) D = Inside diameter of conduit 4. Determine the total number of collars required. The collar size can be increased to reduce the number of collars. Alternatively, the collar size can be decreased by providing more collars. In any case, increase the seepage length by a minimum of 15% Underground Detention No. of collars required = L s /P Underground detention areas are made up of a series of conduits. They range from an oversized storm sewer to a series of conduits that are specifically used for storm water detention. Underground detention is only to be used for stream protection (water quantity treatment). Underground detention cannot be used for pollutant removal (water quality treatment) without approval from Ohio EPA. The following criteria apply when designing underground detention: A. Ensure the Hydraulic Grade Line design of the storm sewer will pass through the structure and meet the requirements of B. Furnish an outlet structure that fully drains the WQ v in 48 hours or more. No more than 50% of the WQ v should be released from the detention basin in less than one-third the drain time (i.e. 16 hours). C. Locate access to the conduits for periodic maintenance so that traffic impacts are minimized. D. If practical, provide pretreatment of the storm water with vegetation. E. Payment for the conduit shall be: Item 611 Conduit, Type, for underground detention. F. Label the location and EDA treatment credit on the Project Site Plan for each underground detention on the project January 2018

125 Drainage Design Procedures Design Check Discharge A design check discharge with the frequency of a 10-year event shall be used. Use the entire drainage area that contributes to the BMP to calculate the design check discharge Retention Basin A retention basin is a wet pond that has a minimum water surface elevation between storms that is defined as the permanent pool. Above the permanent pool is a detention pool that provides storage for 75% of the WQv and drains in 24 hours or more. The detention volume above the permanent pool is called the Extended Detention Volume (EDv). The full storage water depth is typically between 3-6 feet and the volume is less than 15 Ac-ft. The permanent pool is sized to provide storage for 75% of the WQv. A retention basin may be considered for large tributaries, but it may require a large amount of space. Use the following procedure for design of the retention basin: A. Calculate the WQv per Section B. Calculate the Design Check Peak Discharge per Section C. If feasible, provide a forebay (settling pool located at the inlet to the basin) that is 10% of the total storage volume. The forebay volume is part of the required volume and is not an additional volume requirement. D. Size the water quality basin for proper discharge of the WQv and the weir for proper discharge of events up to the design check discharge according to Section Ensure that the water surface elevations created by the basin are considered in the design of the upstream drainage system. E. Provide anti-seep collars for the outlet pipe according to Section The following criteria apply when designing a retention basin: A. Place channel protection (RCP or Tied Concrete Block Mat) at the entrance of the basin to minimize erosion and sediment resuspension. B. Use side slopes of 4:1 (max). C. Use a length to width ratio of at least 3:1 to prevent short-circuiting. D. Furnish a trash rack at the outlet structure. E. The underlying soils should be compacted to prevent infiltration of the permanent pool or an impervious liner should be used. F. Consider vehicle access to the basin for periodic maintenance. G. Retention basin must be greater than 10,000 feet from a municipal airport runway. H. Vegetate the sides of the basin with Item 670 Slope Erosion Protection. I. Embankment work to create the impoundment will be constructed and paid for as Item 203 Embankment, Using Natural Soils, A. J. Furnish a Water Quality Basin, Retention per K. Label the location and EDA treatment credit on the Project Site Plan for each retention basin on the project. January

126 Drainage Design Procedures Water Quality Basin and Weir A retention basin outlet structure is designed similar to the outlet structure for a detention basin. The difference is that the EDv (75% of the WQv) should be discharged out of the basin in 24 hours or more. No more than 50% of the EDv should be released from the detention basin in less than one-third of that 24 hour drain time. The outlet structures are of a similar type, except the openings will be set at a high enough elevation to maintain at least 75% of the WQv in the permanent pool. The catch basin and riser pipe is paid for as Item 611, Water Quality Basin, Retention. Details of the outlet structure can be found on Standard Construction Drawing WQ-1.1 at: px Bioretention Cell A Bioretention Cell consists of a depressed area that allows shallow ponding and treatment of storm water runoff by evapotranspiration and filtration through an engineered soil (bioretention planting soil). As storm water runoff percolates through the bioretention planting soil, sediment and other pollutants are filtered. An underlying perforated underdrain captures the treated storm water runoff and carries it to an outlet. Vegetation assists in maintaining ongoing performance of bioretention cells. Furnish Item 659 Seeding and Mulching for the vegetation of the Bioretention Cell. Cover this area with Item 671, Erosion Control Mat. Do not furnish any 659 Commercial Fertilizer or 659 lime in the Bioretention Cell. Other shrubs or plantings may be furnished in the Bioretention Cell with permission of OHE. The water table or bedrock must be at least 1 foot below the invert (excavated depth) of the bioretention cell. A bioretention cell is sized to treat the WQ V by allowing that volume of runoff to percolate through the bioretention planting soil. Storm water runoff greater than the WQ V is allowed to bypass treatment through an overflow structure. Treatment credit is given to the total area within the right-of-way draining to the most downstream part of the bioretention cell. There are two configurations of bioretention cells: Level bioretention cell in an open area with grassed side slopes (Figure ) Sloped bioretention cell within a grassed ditch (Figure ) Level bioretention cell in an open area with grassed side slopes Furnish pretreatment of the storm water prior to entering the bioretention cell by one of the following methods: A. For sheet flows from impervious areas, the runoff shall flow through a minimum of 5 feet (preferably 15 feet) of grassed filter strip with side slopes no steeper than 3:1. B. For concentrated flows (from a pipe, open channel, or curb cut), the runoff must flow through either a grassed swale at least 20 feet in length or a forebay sized to capture 10% of the WQ V. Furnish a raised catch basin per Figure to allow the design check discharge to bypass the bioretention cell. The design check discharge shall be determined per Section Ensure the elevation of the overflow outlet in the raised catch basin is 12 inches above the surface elevation of the bioretention cell. Ensure that the raised catch basin is located outside of the clear zone January 2018

127 Drainage Design Procedures Sloped bioretention cell within a grassed ditch Furnish pretreatment of the storm water prior to entering the bioretention cell by one of the following methods: A. For sheet flows from impervious areas, the runoff shall flow through a minimum of 5 feet (preferably 15 feet) of grassed filter strip with side slopes no steeper than 3:1. B. For concentrated flows (from a pipe, open channel, or curb cut), the runoff must flow through either a grassed swale at least 20 feet in length or a forebay sized to capture 10% of the WQ V. Furnish an earth dike covered with item 601 Tied Concrete Block Mat Type 1 per Figure to allow the design check discharge to bypass the bioretention cell. The design check discharge shall be determined per Section 1102 for the appropriate design storm of the ditch. The dike shall be 1V:6H or flatter and pond water to a maximum depth of 12 inches. A dike shall be installed at every 1 foot of elevation drop along the longitudinal slope of a linear bioretention cell. For example, if a ditch line is at a 1% slope, a dike would be installed every 100 feet along its length to promote temporary ponding and filtration through the bioretention planting soil Bioretention Cell Design Procedure Use the following procedure for the design of a bioretention cell or follow the bioretention design found in the Ohio Department of Natural Resources Rainwater and Land Development Manual: A. Determine the total impervious tributary area to the bioretention cell: A TRIB,IMP. Include impervious area within and outside of the right-of-way; however treatment credit is only given to the area within the rightof-way. Consider all area within existing right-of-way to be impervious, even if the area is grassed. B. The minimum bioretention cell surface area is 5% of the total impervious tributary area. A BIO = A TRIB,IMP x 5% C. Choose one of the two configurations of bioretention cells and follow the appropriate pretreatment and overflow requirements described in Section and D. Ensure a maximum depth of 12 inches measured from the Final Grade of the bioretention cell to the outlet structure (riser pipe, raised catch basin, weir, or check dam). E. In addition to the pretreatment required where concentrated flow enters the bioretention cell, limit the incoming velocity to 1 fps or less for the Water Quality Flow (WQ F) to protect the bioretention cell from erosion. Calculate the WQ F per Section at the point of concentrated flow. Increase the pipe size, widen the open channel, increase the curb opening to the bioretention cell, or provide energy dissipation to limit the velocity to 1 fps or less. For Curb Cuts, assume all the WQv is captured by the curb opening and use the height of the curb and the opening width to calculate the area. F. Do not place a bioretention cell where the required hydraulic design flows (i.e. 2 year event, 5 year event,10 year event, or higher) have an Allowable Shear Stress higher than 1 psf or velocity higher than 5 fps G. Furnish the bioretention cell layers as shown in Figure Bioretention Planting Soil Layer: Furnish 30 inches of bioretention planting soil (plan note WQ101). When planting shrubs or trees, ensure the bioretention planting soil layer extends at least 4 inches below the lowest root ball. 2. Filter Layer: Furnish 3 inches of Fine Aggregate per CMS directly below the bioretention planting soil layer. Furnish 3 inches of Coarse Aggregate size No. 78 per CMS directly below the Fine Aggregate layer. January

128 Drainage Design Procedures 3. Gravel Layer for Underdrain: Furnish 12 inches of Coarse Aggregate size No. 57 per CMS directly below the No. 78 aggregate layer. A minimum of 3 inches of No. 57 aggregate shall be provided above and below any underdrain pipes. H. For the bioretention planting soil, specify 10% excess planting mix volume to account for expected settling of the uncompacted soil. Show final expected soil elevations on the plans, but allow contractor to place bioretention planting soil 3 inches above elevations shown on plans, as described in Plan Note W101 Bioretention Cell(s). I. Furnish one 4 inch diameter perforated PVC pipe underdrain per CMS 605 along the length of the bioretention cell. Furnish one underdrain at the center for widths 20 feet or smaller. For all other widths calculate the number of underdrains required by dividing the width by 20 and rounding up to the next whole number. Space these underdrains equally around the center with a minimum distance of 5 feet from the outside edge. J. Furnish a 4 inch diameter PVC observation well/cleanout port in accordance to Figure for every run of underdrain at an interval of 100 feet. K. Outlet the underdrain by combining all underdrains into a single 6 inch type C Item 611 pipe. Furnish this pipe with a positive outlet either into a drainage structure that is part of the drainage design or on a slope with Item 611 precast concrete outlet. Show underdrain connection to outlet in the plans. L. For bioretention cells planted with grass, include temporary erosion control mat Type A, B, C, or E per CMS 671 with either straw mulch or compost as per plan over the surface of all bioretention planting soil. Specify the mat type on the plan sheets. M. For non-grass bioretention cells that include shrubs or trees, furnish a 3 inch layer of wood fiber mulch per CMS above the bioretention planting soil. N. Label the location and EDA treatment credit on the Project Site Plan for each bioretention cell on the project. O. PAY ITEMS: 203 Excavation As Per Plan cu yd 601 Bioretention Cell cu yd 601 Tied Concrete Block Mat sq yd 605 Underdrain As Per Plan, (includes observation wells, fittings, and couplers as specified) 611 Outlet Pipe 659 Seeding and Mulching sq yd 671 Erosion Control Mats As Per Plan sq yd Infiltration Infiltration techniques treat storm water through the interaction of a filtering substrate that consists of soil, sand, or gravel. This technique discharges the treated storm water into the ground water rather than into surface waters. Typically, infiltration practices are only suitable when Hydrologic Soil Group (HSG) Type A soils or, in some cases, HSG Type B soils exist. Infiltration methods require an extensive investigation of the existing soils and geology to ensure success. The investigation should begin with a preliminary soil evaluation of the project site early in the design process (PDP Preliminary Engineering Phase). In-situ testing is not anticipated during the preliminary evaluation process. Use available soil and geology data found in the Soil and Water Conservation maps, United States Geological Survey (USGS), adjacent projects, or estimations from a geotechnical engineer January 2018

129 Drainage Design Procedures National Resources Conservation Service s Web Soil Survey website may also provide soil and geology information. Material property tables for infiltration, permeability, and porosity have been provided for the preliminary evaluation (Tables & ). If the preliminary evaluation yields favorable results, perform a more detailed evaluation. The detailed evaluation will require a geotechnical investigation of the underlying soils and geology. Soil borings should be performed to a maximum depth of 20 feet (or refusal) with samples taken every 5 feet for laboratory testing. The number and location of soil borings should correspond with the approximate size (as determined in the preliminary evaluation) of the infiltration BMP and should be recommended by the geotechnical engineer. If the detailed evaluation yields favorable results, the ground water depth must be verified. The geotechnical engineer shall provide the seasonal high ground water depth. In some cases, observation wells may be installed and static water levels may be observed over a dry and wet season for verification. The infiltration and permeability rate of the soil shall be tested in the detailed soil evaluation at the discretion of the geotechnical engineer. In some cases, insitu testing at the proposed location of the infiltration BMP may be required. The following criteria apply to infiltration methods and must be met to be considered a feasible alternative: A. Design using the WQv as per Section B. Do not place infiltration BMP where snow may be stored. C. The appropriate soil type must be present: 1. Infiltration (the rate at which water enters into the soil from the surface) must be greater than 0.50 in/hr and no greater than 2.4 in/hr. 2. Soils must have less than 30% clay or 40% of clay and silt combined. D. The invert of the structure must be at least 4 feet above the seasonal high water table and any impervious layer. E. Infiltration techniques are not suitable on fill soil, compacted soil, or steep slopes (greater than 4:1). Consideration should be given to the long term impacts upon hillside stability if applicable. F. Pretreatment shall be provided to remove large debris, trash and suspended sediment to extend the service life. An example of pretreatment includes providing vegetated ditches prior to flow entering the infiltration facility Infiltration Trench An infiltration trench is an excavated trench that has been lined with a geotextile fabric and backfilled with aggregate. The storm water is filtered through the aggregate and is stored within the pore volume of the backfill material. It is allowed to percolate through the sides and bottom of the trench. The drawdown time of the WQv is 24 hours or more. Design of an infiltration trench must follow the criteria in the Ohio Department of Natural Resources Rainwater and Land Development Manual: The following criteria apply when designing an infiltration trench: A. Furnish a 6 inch layer of Coarse Aggregate No. 57 or 67 conforming to CMS per CMS on the top of the trench. B. Furnish Coarse Aggregate No. 1 or 2 conforming to CMS within the infiltration trench. January

130 Drainage Design Procedures C. Pretreatment using vegetation shall be provided to ensure longevity of the infiltration trench. D. An observation well shall be provided to facilitate ground water level inspection. E. Locate the infiltration trench at least 1,000 feet from any municipal water supply well and at least 100 feet from any private well, septic tank, or field tile drains. F. Ensure the bottom of the trench is below the frost line (2.5 feet) G. Furnish an infiltration trench as Item 601 Infiltration Trench. H. Label the location and EDA treatment credit on the Project Site Plan for each infiltration trench on the project Infiltration Basin An infiltration basin is an open surface pond that uses infiltration into the ground as the release mechanism. It is designed to store the WQv. Depending on the soil permeability, it may be used to treat from 5 to 50 acres. Lower permeable soils may require an underdrain system as an additional outlet. The drawdown time of the WQv should be between hours. Use the following procedure for the design of an infiltration basin: A. Calculate the WQv per Section B. Determine the invert area of the infiltration basin using the following equation: A = (WQv * S.F. * 12)/(k * t) Where: A = area of invert of the basin (Acres) WQv = Water Quality Volume (see section 1115) (Acre-feet) S.F. = Safety Factor of 1.5 k = Infiltration Rate (in/hr) (table ) t = Drawdown time of 48 hours Table NRCS Soil Type (from soil maps) C. Use a length to width ratio of 3:1. HSG Classification Rate (k) (in/hr) Sand A 8.0 Loamy Sand A 2.0 Sandy Loam B 1.0 Loam B 0.5 Silt Loam C 0.25 Sandy Clay Loam C 0.15 Clay Loam & Silty Clay Loam D < 0.09 Clays D < 0.05 Infiltration Rate (k) From Urban Runoff Quality Management WEF Manual of Practice No. 23, 1998, published jointly by the WEF and ASCE, chapter five January 2018

131 Drainage Design Procedures D. Determine the required depth of the infiltration basin using following equation: Where: A = area of invert of the basin (Acres) WQv = Water Quality Volume (Ac-ft) D = Required depth of the basin (ft) E. Allow for 1 foot (min) freeboard above the WQv. D = WQv/A F. Calculate the Design Check Peak Discharge per Section G. Furnish bypass or overflow for the design check discharge. The following criteria apply when designing an infiltration basin: A. Use an energy dissipater at the inlet. B. Vegetate the sides of the basin with Item 670 Slope Erosion Protection. C. Furnish a 6 inch layer of Coarse Aggregate No. 57 or 67 conforming to CMS per CMS on the bottom of the basin. D. Use side slopes of 4:1 (max). E. Consider vehicle access to the basin for periodic maintenance. F. Locate basin at least 1,000 feet from any municipal water supply well and at least 100 feet from any private well, septic tank, or drain field. G. Furnish 10 feet or less width between 4 inch underdrain laterals (if used in the design). H. Do not locate the basin where infiltrating ground water may adversely impact slope stability. I. Ensure the invert of any underdrain in the basin is below the frost line (2.5 feet). J. Embankment work to create the impoundment will be constructed and paid for as Item 203 Embankment, Using Natural Soils, A. K. Label the location and EDA treatment credit on the Project Site Plan for each infiltration basin on the project Constructed Wetlands Constructed Wetlands treat storm water through bio-retention. They are depressed, heavily planted areas that are designed to maintain a dry weather flow depth ranging between 0.5 to 2 feet. The surface area required for a wetland is usually quite large due to the limited allowable depth. The area is usually on the magnitude of 1% of the entire drainage area. They are designed in a similar manner as a retention basin. The wetland is sized to provide storage for the WQ v for a time frame of at least 24 hours (above the permanent pool) while providing a bypass or overflow for larger design check discharge (see section ). The water depth should be maintained by an outlet structure capable of providing the required water depth with the provision of a one foot freeboard. The following criteria apply when designing a Constructed Wetland: A. Do not place on a steep or unstable slope or at a location, which could induce short-term or long-term instability. January

132 Drainage Design Procedures B. Constructed Wetlands must be greater than 10,000 feet from a municipal airport runway. C. Base flow must be present to maintain the constant water depth (such as ground water). D. Furnish a forebay that is 7% of the total required volume at a depth between 3-6 feet to settle out sediments. E. Furnish side slopes of 4:1 (max). F. Consider access for maintenance to the forebay and the outlet structure. G. Vegetate the sides and bottom with grass H. Furnish an impervious liner. Use a compacted clay bottom or a geotextile fabric to prevent infiltration of the storm water. I. Furnish a length to width ratio of 3:1 (min) to prevent short-circuiting. J. Label the location and EDA treatment credit on the Project Site Plan for each constructed wetland on the project Stream Grade Control Stream grade control structures are structures installed on the upstream and downstream end of a culvert at a stream crossing to promote stream protection. They provide a grade control in a stream to prevent downcutting of the stream bed. The following are Stream Grade Control structures: Concrete aprons shown in Section Three sided culverts with paved Inverts Three sided culverts with bed rock inverts Stream grade control structures provide quantity treatment, but not quality treatment. Therefore, stream grade control structures must be paired with a post-construction BMP that provides quality treatment. Only those portions of a project within existing and/or new permanent right-of-way that drain to a stream grade control structure receive quantity treatment credit. Stream grade control structures are only an appropriate post-construction BMP when installed within a Waters of the United States, and associated with sites that acquire a permit from the Army Corps of Engineers for stream impacts. Label the location and EDA treatment credit on the Project Site Plan for each stream grade control structure on the project Bridge Hydraulics General Bridge structural design requirements are found in the Bridge Design Manual while hydraulic design criteria are governed by this manual. When submitting hydraulic design calculations, flood hazard evaluations, hydrology and hydraulic reports, and scour evaluations submit to the Office of Hydraulic Engineering January 2018

133 Drainage Design Procedures Hydrology and Hydraulics (H&H) Report The H&H report is required as part of the Structure Type Study. A. A small scale area plan showing: approximate location of all stream cross sections used for the hydraulic analysis; an accurate waterway alignment at least 500 feet each way from the structure; and the alignment of the proposed and present highways, taken from actual surveys. B. Provide a profile along the centerline of highway so that the overflow section may be computed. This profile should extend along the approach fill to an elevation well above high water. If there are bridges or large culverts located within 1000 feet upstream or downstream from the proposed bridge, show stream cross sections including the structure and roadway profiles of the overflow sections of the structures. These may be used as a guide in establishing the waterway requirements of the proposed structure Analysis The H&H analysis is performed using the design year as discussed in section of this manual along with the 100 year and 500 year frequencies. A step backwater calculation is computed for each frequency. A one-dimensional step backwater software (example: HEC-RAS) is acceptable. In some cases a twodimensional step backwater method may be necessary at the direction of the Department. Include the following items in the H&H analysis: A. Hydrology calculations or origin of discharge frequencies used in the analysis. Include the drainage area in square miles. B. Input and output data including electronic program files. If using the HEC-RAS computer program, refer to the HEC-RAS Help Applications Guide for the Multiple Plans file structure. C. Plan view of stream with cross sections identified. Include enough cross sections to properly model the existing and proposed stream as required. D. Color photographs of the upstream channel, downstream channel, and the bridge opening location. E. Computations for existing and proposed conditions Narrative The Narrative is a written discussion the hydraulic adequacy for both the design year and 100 year frequency discharges. The narrative includes the rationale used to determine the proposed structure size and it is supported by an analysis of design alternatives. Include the following in the narrative: A. Capital costs and risk as part of the discussion. Risk is defined as the consequences attributable to a flood plain encroachment. B. A statement as to whether or not the structure is located in a flood insurance study. Identify the Flood Insurance map showing the project location, with any designated floodway information or elevations. C. High water data from local residents and observed high water marks including their locations. D. Approximate Flood Peak Discharge Frequency of roadway overtopping. E. A Flood Hazard Evaluation (see ) F. Description of the bridge deck drainage. Indicate how the surface water will be collected and discharged. Include any scupper catch basin locations. January

134 Drainage Design Procedures January 2018

135 1100 Drainage Design Procedures List of Figures Figure Subject Overland Flow Chart General Notes for Figures and Rainfall Intensity-Frequency-Duration Curves Rainfall Intensity Zone Map Capacity of Grate Catch Basin in a Sump Channel Features Nomograph for Flow in Triangular Channels Capacity of Curb Opening Inlets on Continuous Grade Capacity of Standard Catch Basin Grates in Pavement Sags - Flow Through Grate Opening Capacity of Inlets and Standard Catch Basins in Pavement Sags - Flow Through Curb Opening Type F, Broken Back Detail Classification of Flow in Culverts Corrugated Metal Pipe Sizes and "n" Values for Type A Conduits Example Bankfull Discharge Culvert Design End Treatment Grading Detail Box Culvert Outlet Detail Box Culvert Inlet Detail Rock Channel Protection at Culvert Storm Sewer Outlets Notice of Intent (NOI) Acreage Calculation Form Water Quality Cq Post-Construction BMP Treatment Exempt Outfalls Manufactured System Detail Vegetated Biofilter Detail Figure Deleted January Figure Deleted July 2015 January 2018

136 1100 Drainage Design Procedures List of Figures Extended Detention Basin Example Retention Basin Example Bioretention Cell Example Figure Deleted January Infiltration Basin Example Anti-Seep Collars January 2018

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139 General Notes Figures through The Rainfall Intensity-Duration-Frequency (IDF) curves are based upon precipitation data obtained from the National Oceanic and Atmospheric Administration (NOAA) Atlas 14. The precipitation data was collected between 4/1863 to12/2000. Rainfall depth varies across the State with more rainfall depth present in the Southwest portion of the state and gradually decreasing towards the Northeast. IDF curves were developed for 4 regions across the State to simplify hydraulic design. The regions were determined by normalizing contours created from NOAA precipitation GIS data from the 10 year, 60 minute duration. Federal Highway Administration Hydraulic Engineering Circular No. 12 Appendix A offers a methodology for converting I-D-F data points to an equation of the general form: i= a/(t+b)^c Where: i = rainfall intensity (inches/hour) t = time of concentration (minutes) a = constant b = constant c = constant Figure can be expressed using the above general equation utilizing the constants shown below. Intensity Zone (Figure ) Frequency (Years) Constant "a" Constant "b" Constant "c" A B C D For any projects that have begun using the previous Rainfall Intensity-Duration-Frequency (IDF) curves, continue with their use through the completion of the project. The current Rainfall Intensity-Duration- Frequency (IDF) curves should be used at the start for all new projects.

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141 Rainfall Intensity-Frequency-Duration Curves Revised July Reference Section AREA A 8 AREA B INTENSITY (IN/HOUR) Year INTENSITY (IN/HOUR) Year DURATION IN MINUTES DURATION IN MINUTES 8 AREA C 8 AREA D INTENSITY (IN/HOUR) Year INTENSITY (IN/HOUR) Year DURATION IN MINUTES DURATION IN MINUTES Refer to General Notes Figures through

142 Rainfall Intensity-Frequency-Duration Curves Revised July Reference Section Refer to General Notes Figures through

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156 12" ROCK CHANNEL PROTECTION AT CULVERT AND STORM REFERENCE SECTION SEWER OUTLETS Over 20 f.p.s. use Energy Dissipator 48" Thickness of Type A Rock or Energy Dissipator ROCK LEGEND TYPE A 48" of 18" rock A 36" of 18" rock B 30" of 12" rock C 18" of 6" rock " " 96" 2 84" 3 No Protection 20 Pipe Diameter or Rise 72" 6 0 " 48" 3 6 " 10 24" VELOCITY AT PIPE OUTLET - f.p.s. NOTES Rock size (6", 12", 18") indicates the square opening on which 85% 1 of the material, by weight, will be retained The width of protection shall be the width of the headwall, with 4' being the minimum. (Where a stream bed will withstand the calculated velocity without erosion, no rock channel protection will be required.) LENGTH OF PROTECTION

157 January 2008 NOTICE OF INTENT (NOI) ACREAGE CALCULATION FORM Reference Section 1112 Project Earth Disturbing Activities If the project is a Routine Maintenance Project, an NOI is not required. (See Section 1112) Contractor Earth Disturbing Activities Field Office: Enter for Type A; 0.25 for Type B; or 1.00 for Type C Batch Plant: Yes = 2.0; No = 0 Off-Project Waste / Borrow Pit: Add 1.0 acre per 15,000 CY of waste or borrow Miscellaneous Other Off-Project Areas: Off-Project staging areas, stock yards, etc. Contractor Earth Disturbing Activities Total Earth Disturbing Activities (add Project EDA and Contractor EDA) Subtotal TOTAL Area (acres) NOI Earth Disturbing Activities (see below to determine value) TOTAL Project Earth Disturbing Activities - Enter the area of permanent earth disturbing activities directly related to project activities. Earth disturbing activity is defined as any activity that exposes bare ground or an erodible material to storm water and anywhere Item 659 Seeding, SS 870 Seeding, Item 660 Sodding, or SS 870 Sodding is being furnished. Contractor Earth Disturbing Activities: Field Office - These sizes were determined with regard to size of the trailer, parking, and some stock area for equipment and materials. Batch Plant - It is assumed that a typical batch plant would occupy 2 acres of ground. The designer should investigate the location of the project relative to existing plants, facilities, etc. to estimate whether a batch plant might be used by the Contractor. This is not needed for existing plants, it is only for plants set up for the specific project. Off-Project Waste / Borrow - The specified estimation is based on approximately 10 feet of depth or fill over 1 acre. The designer may choose a different value based on knowledge of the project area, bedrock elevations, previous projects, etc. Consideration should be given for grindings, as well. (10ft. x s.f. / 27 = 16,133 c.y. ~ 15,000 c.y.) NOI Earth Disturbing Activities - This is the combined Project and Contractor Earth Disturbed Area. Based on project conditions and activities, some flexibility in the area calculation should be provided to avoid the possibility of the estimated work being less than the actual work. This scenario would require submittal of an NOI for projects originally calculated to be less than one acre during construction. For projects with an estimated NOI EDA less than one acre: No NOI is required. For projects with an estimated NOI EDA of one or more acre, but less than 4.9 acres, use 4.9 acres. For projects with an estimated NOI EDA greater than 4.9 acres, use the sum of the Project and Contractor Earth Disturbed Areas. A Routine Maintenance Project consists of activities that do not change the line, grade, or hydraulic capacity of the existing condition and has less than 5 acres of earth disturbing activities (see section ).

158 January 2008 WATER QUALITY Cq REFERENCE SECTION Cq Impervious ratio

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161 JULY 2011 MANUFACTURED SYSTEM DETAIL REFERENCE SECTION 1117 RESERVED AREA FOR OFFLINE MANUFACTURED SYSTEM SIZED PER DIVERSION WEIR RESERVED WIDTH PER 1117 INFLOW TRUNK SEWER OUTFLOW TRUNK SEWER MANHOLE NO. 3 W/BASE DIAMETER PER SECTION SOME SYSTEMS REQUIRE TWO SMALLER MANHOLES RATHER THAN ONE LARGE MANHOLE. 8" OUTFLOW TRUNK SEWER CAN BE LOCATED UP TO A 45 DEGREE ANGLE. PLAN VIEW NOT TO SCALE

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163 EXTENDED DETENTION BASIN EXAMPLE July 2015 REFERENCE SECTION 1117 Given: Total Tributary Area = 7.5 ac o Tributary Area within Existing R/W = 7.2 ac o Tributary Area, Impervious, Outside of R/W = 0.3 ac o Tributary Area, Pervious, Outside of R/W = 0.0 ac o Tributary Area, Pavement and Paved Shoulders = 1.5 ac o Tributary Area, Berms and Slopes 4:1 or Flatter = 6.0 ac Rainfall Area B Time of Concentration, t C = 25 min (calculation shown in this example) Calculate the water quality volume WQ V : WQ V = (P*A*Cq)/12 P = 0.75 in A = 7.5 ac Cq = 0.858i i i o i = fraction impervious o The area within existing ODOT right-of-way is considered impervious area for the purpose of post-construction BMP design considerations. (L&D Vol 2, Sec ) o i =... = 1.0 Cq = 0.858* * * = Per L&D Vol. 2, Section , consider all area within existing right-of-way to be impervious with a runoff coefficient of Therefore, Cq = 0.9 WQ V = (0.75 in * 7.5 ac * 0.9) / 12 WQ V = ac-ft Calculate the minimum detention basin volume, forebay volume, and micropool volume: Minimum basin volume = WQ V * 1.20 (due to 20% increase) = WQ V *1.2 = ac-ft *1.2 = ac-ft 10% WQ V for forebay volume, 10% * ac-ft = ac-ft 10% WQ V for micropool volume, 10% * 0.422ac-ft = ac-ft Layout a detention basin configuration that meets the following requirements: Forebay volume below the lowest outlet elevation at upstream end of the basin Micropool volume below the lowest water quality outlet invert elevation at the downstream end of the basin Maximum 4:1 side slopes Include provisions for vehicle access 1 of 13

164 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Detention Basin Plan View: Detention Basin Profile View: Forebay: The forebay volume is the volume stored upstream of the low flow channel. The volume in the forebay is held in a permanent pool, and is unable to flow downstream towards the outlet. The purpose of the forebay is to allow runoff to slow enough for coarse sediment to settle out. This improves performance and reduces the maintenance burden by concentrating sediment buildup in one location designed for maintenance access. Forebay volume must be greater than or equal to ac-ft. Forebay depth = = 2 ft Forebay bottom area = 25 ft * 18 ft = 450 ft 2 Forebay top area = 41 ft * 34 ft = 1,394 ft 2 Forebay volume = (450 ft 2 + 1,394 ft 2 ) / 2 * 2ft / 43,560 = ac-ft ac-ft is equal to the ac-ft requirement: Acceptable 2 of 13

165 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Micropool: The micropool volume is the volume that is stored below the lowest invert elevation of the lowest water quality outlet. The purpose of the micropool is to slow runoff draining towards the outlet structure, promote sediment settling below the outlet structure, and allow use of a nonclogging outlet. This improves performance and reduces clogging and maintenance. Micropool volume must be greater than or equal to ac-ft. Micropool depth = = 2 ft Micropool bottom area = 25 ft * 20 ft = 500 ft 2 Micropool top area = 41 ft * 36 ft = 1,476 ft 2 Micropool volume = (500 ft 2 + 1,476 ft 2 ) / 2 * 2ft / 43,560 = ac-ft ac-ft is greater than ac-ft requirement: Acceptable Water Quality Volume (WQ V ) Storage: The WQ V must be fully stored above the lowest water quality outlet elevation. The lowest water quality outlet is at an elevation of ft. The WQ V (0.422 ac-ft) must be stored between ft and catch basin overflow. 3 of 13

166 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Stage (Elevation) vs. Volume Curve: The graph shows that the full WQ V is stored between and ft in the detention basin. The forebay and micropool have been excluded from this stage vs. volume graph since the volume associated with the forebay and micropool is constantly standing water. 4 of 13

167 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Design the Detention Basin Water Quality Outlet: The minimum discharge time of the WQ V is 48 hours with no more than 50% of the WQ V being released from the detention basin in the first one-third of the 48 hour drain time. WQ V = ac-ft; must take 48 hours or longer to drain 50% or less of the WQ V (i.e ac-ft) must be drained in 16 hours. Choose eight 0.5 inch diameter circular orifices at ft and eight 0.5 inch diameter circular orifices at ft. Calculate the drawdown curve. o This calculation can be done by hand by creating a stage vs. discharge table and interpolating between values, but it is generally easier to use a model to simulate runoff through a detention basin such as PondPack or HydroCAD. Do not route a design storm hydrograph through a detention basin to determine the drawdown curve. Start the simulation with the water surface at a level equivalent to the WQ V storage (for this example, at an elevation of ). Then allow the pooled water filling the WQ V to drain by gravity out of the water quality outlet structure. Include all detention basin outlets that would affect this drawdown curve. Include any downstream constraints such as tailwater or limiting conveyance downstream. For this example, there is no tailwater and there is a free discharge from the detention basin. 5 of 13

168 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Modeled Drawdown Curve using Pond Pack: The graph shows that it takes longer than 48 hours to drain the WQ V (0.422 ac-ft); therefore, it is acceptable. The graph shows that it takes 16 hours to drain one half of the WQV (0.211 ac-ft); therefore, it is acceptable. Size the Primary Detention Basin Outlet: There are three main parts of a typical extended detention basin discharge structure: o Water quality outlet(s) o Primary outlet o Overflow weir 6 of 13

169 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 The primary detention basin outlet normally consists of a catch basin grate and the conduit that conveys discharges from the detention basin during all but the least frequent precipitation events. The primary outlet should be sized to convey the 10-year design storm. ODOT Water Quality Catch Basin Detail (WQ-1.1): Determine the 10-year peak flow rate: For the purposes of post-construction BMP calculations, all existing right-of-way is to be considered impervious. For the purpose of general conveyance sizing, runoff coefficients should be calculated using Table in ODOT s L&D Vol. 2. Q = CiA 7 of 13

170 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Calculate the weighted C value: 1.5 acres of tributary area are pavement and paved shoulders: C = acres of tributary area are berms and slopes 4:1 or flatter: C = 0.5 C weighted =..... = 0.58 Determine the precipitation intensity: Rainfall Area B t C = 25 min (The time of concentration is given in this example as 25 minutes because there is significant overland flow over grassed area. The time of concentration should be calculated for each site based on the site-specific flow path. 25 minutes would likely be too high of a value if the detention basin were receiving flow from a piped system. See the time of concentration calculations below.) L&D Vol. 2, Figure : Area B, 10-year frequency, 25 min t C : i = 3.4 in/hr Q = 0.58 * 3.4 in/hr * 7.5 ac = cfs Time of Concentration (t C ) Calculations: o t C = Time of overland flow (t O ) + Time of shallow concentrated flow (t S ) + Time of channel flow (t C ) o Overland Flow (t O ) t O =,./ / C = Runoff Coefficient (0.58 for this example) L = Distance to most remote location in drainage in feet (max. 300 ft.) (200 ft. in this example) s = Overland slope (percent) (0.33% in this example) t O =,../. / = minutes o Shallow Concentrated Flow (t S ) V S = Velocity of shallow concentrated flow (ft/sec) = 3.281ks 0.5 k = Intercept Coefficient (L&D Table ) = (0.457 in this example) s = Overland slope (percent) (0.33% in this example) V S = * * = 0.86 ft/sec Length of shallow concentrated flow = 200 ft. t S = 200 ft. / 0.86 ft/sec = 233 sec = 3.88 minutes 8 of 13

171 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 o Channel Flow (t C ) Manning s Equation: V =./ / V = velocity in the channel (ft/sec) r = hydraulic radius (0.69 ft. in this example) s = channel slope (0.01 ft/ft in this example) n = Manning s Roughness Coefficient (L&D Vol. 2, Table ) (0.03 in this example) V =../. / = 3.88 ft/sec. Channel length = 500 ft. (for this example) tc = 500 ft. / 3.88 ft/sec = 129 sec. = 2.15 minutes o t C = t O + t S + t C = = minutes. Use t C = 25 minutes Size the primary detention basin discharge conduit: The discharge conduit must be large enough to convey the 10-year design storm, keeping the maximum hydraulic grade line within the crown of the pipe. This example has the following conduit characteristics: o Conduit slope = ft/ft o No Tailwater; free discharge o Pipe Roughness Coefficient = (L&D Vol. 2, Section ) The minimum conduit size that conveys the 10-year peak flow (14.79 cfs) with the given characteristics is a 24-inch diameter pipe. Set the catch basin grate elevation: The WQ V fills the detention basin to an elevation of ft. At water surface elevations of ft and below, all discharge should pass through the water quality outlet. (In this example, the water quality outlet is the two rings of 0.5 inch orifices at ft and ft.) The ODOT standard water quality catch basin detail (SCD WQ-1.1) calls for either Catch Basin No. 2-3 or 2-4 depending on the outlet pipe size. Both catch basins have a 6-inch high side inlet that is either 3 or 4 feet wide depending on the catch basin. See the detail: 9 of 13

172 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 ODOT Catch Basin No. 2-3 and No. 2-4: However, SCD WQ-1.1 calls for a catch basin used for a detention basin to not have the side inlet windows. Therefore, side inlets should not be included in a detention basin outlet structure. The elevation of the top of the grate should be set at the WQ V elevation. Therefore, any volume above the WQ V may discharge into the catch basin through the grate. o Catch basin grate elevation = ft Set the Overflow Weir Invert Elevation: The 10-year peak flow rate (14.79 cfs) should pass fully through the primary discharge. Therefore, no flow should discharge from the overflow weir until the 10-year flow rate has been exceeded. Set the overflow weir invert elevation just high enough above the catch basin grate such that the full 10-year peak flow rate is conveyed through the primary discharge. 10 of 13

173 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 For this example, the primary discharge pipe is sized at 24 inches in diameter; therefore, Catch Basin No. 2-3 is appropriate. Catch Basin No. 2-3 has the same grate as Catch Basin No. 2-2B. The water quality catch basin has one openings to allow runoff inside; Grate No. 2-2-B. Use L&D Vol. 2, Figure to determine the necessary head above a No. 2-2-B grate to pass the 10-year peak flow rate (14.79 cfs). According to Figure , 1.25 ft of head is required to pass a flow rate of cfs. Add the necessary head to the grate elevation (799.0 ft) o ft ft = ft Set the overflow weir elevation at ft. Size the Emergency Overflow Weir and Set the Top of Basin Elevation: L&D Vol. 2, Section states that the hydraulic grade line should be checked for the 25- year storm. The 25-year peak flow rate should pass fully through the overflow weir. Calculate the peak flow rate: o 25-year t C = 25 min and Rainfall Area B: 3.8 in/hr o 25-year storm peak flow rate: Q = CiA = 0.58 * 3.8 in/hr * 7.5 ac = cfs Calculate the required weir length for each design storm flow: o Overflow weir elevation = ft o Assume a top of detention basin elevation of ft. o Maximum height at overflow weir = ft ft = 0.5 ft o Weir equation: Q = C*L*H 1.5 C = 3 H = 0.5 L =? o Length of a weir: L = o 25-year: L =.... = 15.6 ft Provide a 16 ft wide overflow weir. The top of basin elevation is ft. The overflow weir length could be reduced by increasing the top of basin elevation. Or the top of basin elevation can be lowered by increasing the overflow weir length. The 25-year peak flow rate must fully pass through the overflow weir without overtopping the detention basin. Flow rates greater than the 25-year peak flow rate may overtop the detention basin uncontrolled. Provide erosion protection at the overflow weir, to the bottom of the berm, and continuing downstream if there is erosion potential. 11 of 13

174 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Design Anti-Seep Collars: Anti-seep collars reduce the conveyance of flow along pipe bedding, outside of a conduit and increase the flow path for the seepage of water. This helps protect the berm above the discharge conduit from a detention basin from internal erosion. ODOT Standard Drawing WQ-1.2 Calculate the saturated zone length along the conduit (Ls) o Ls = Y(Z+4)[1+S/(0.25-S)] o Y = depth of water during the 10-year storm o Z = slope of embankment o S = slope of conduit Maximum elevation at 10-year storm = ft Conduit elevation = ft Y = ft ft = 5.25 ft Z = 4 S = Ls = 5.25(4+4)[ /( )] = ft ΔLs = 0.15*Ls = 0.15 * ft = 6.4 ft 12 of 13

175 EXTENDED DETENTION BASIN EXAMPLE (C0NTINUED) July 2015 REFERENCE SECTION 1117 Total Projection: P = W D o W = 2ft + 2 ft diameter + 2 ft = 6 ft o P = 6 ft 2 ft = 4 ft Number of collars = ΔLs / P = 6.4 ft / 4 ft = 1.6 o Minimum of 2 collars per outlet conduit o Use 2 anti-seep collars Place both anti-seep collars in the saturation zone (within ft of front edge of berm). Spacing between collars: between 10 and 25 feet Additional Considerations: Vegetate the sides of the detention basin with Item 670 Slope Erosion Protection per L&D Vol. 2, Section For all open water carriers at each inlet and discharge from the detention basin, check the shear stress and ensure appropriate lining per L&D Vol. 2, Section For all culverts that discharge into or out of a detention basin, ensure that appropriate rock channel protection is included per L&D Vol. 2, Section Include calculated detention basin ponding elevations in the calculation of the hydraulic grade line for the upstream conveyance system per L&D Vol. 2, Section Attempt to locate structures outside of designated flood plains. If a detention basin encroaches on a flood plain, follow the flood assessment requirements in L&D Vol. 2 Section Ensure that safety criteria are met in the clear zone per L&D Vol. 1, Section Ensure that no more than one foot of permanent standing water is located within the clear zone without barrier protection, per L&D Vol. 1, Section Engage local project stakeholders in potential public safety considerations associated with detention basins. Develop a plan for how regular maintenance will be performed. o Vehicle access o Mowing o Removal of woody vegetation o Regular unclogging of the water quality outlet 13 of 13

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177 RETENTION BASIN EXAMPLE July 2015 REFERENCE SECTION 1117 Given: Total Tributary Area = 7.5 ac o Tributary Area within Existing R/W = 7.2 ac o Tributary Area, Impervious, Outside of R/W = 0.3 ac o Tributary Area, Pervious, Outside of R/W = 0.0 ac o Tributary Area, Pavement and Paved Shoulders = 1.5 ac o Tributary Area, Berms and Slopes 4:1 or Flatter = 6.0 ac Rainfall Area B Time of Concentration, t C = 25 min (calculation shown in this example) Calculate the water quality volume WQ V : WQ V = (P*A*Cq)/12 P = 0.75 in A = 7.5 ac Cq = 0.858i i i o i = fraction impervious o The area within existing ODOT right-of-way is considered impervious area for the purpose of post-construction BMP design considerations. (L&D Vol 2, Sec ) o i =... = 1.0 Cq = 0.858* * * = Per L&D Vol. 2, Section , consider all area within existing right-of-way to be impervious with a runoff coefficient of Therefore, Cq = 0.9 WQ V = (0.75 in * 7.5 ac * 0.9) / 12 WQ V = ac-ft Calculate the extended detention volume (ED V ): ED V = WQ V * 75% = ac-ft * 0.75 = ac-ft Calculate the minimum permanent pool storage volume: Minimum permanent pool volume = WQ V * 75% = ac-ft * 0.75 = ac-ft Layout a retention basin configuration that meets the following requirements: Maximum 4:1 side slopes Include provisions for vehicle access Length to width ration of at least 3:1 At least 75% of WQ V stored in a permanent pool 1 of 12

178 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 Elevation vs. Volume Table: Elevation (feet) Storage (acre-feet) Elevation (feet) Storage (acre-feet) Elevation (feet) Storage (acre-feet) Elevation vs. Volume Elevation (ft) ED V = (0.660 ac-ft ac-ft) = ac-ft Permanent Pool (0.327 ac-ft) Volume (ac-ft) 2 of 12

179 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 The permanent pool elevation is set at ft. o ac-ft of storage is permanently ponded. o ac-ft is greater than ac-ft; therefore, it is acceptable. The ED V volume is between ft and ft. o ac-ft ac-ft = ac-ft o ac-ft is greater than ac-ft; therefore, it is acceptable. Design the Retention Basin Water Quality Outlet: The minimum discharge time of the ED V is 24 hours with no more than 50% of the ED V being released from the retention basin in the first one-third of the 24 hour drain time. ED V = ac-ft; must take 24 hours or longer to drain 50% or less of the ED V (i.e ac-ft) must be drained in 8 hours. Choose one 2.5 inch diameter circular orifice at an elevation of ft. Calculate the drawdown curve. o This calculation can be done by hand by creating a stage vs. discharge table and interpolating between values, but it is generally easier to use a model to simulate runoff through a retention basin such as PondPack or HydroCAD. Do not route a design storm hydrograph through a retention basin to determine the drawdown curve. Start the simulation with the water surface at a level equivalent to the ED V storage (for this example, at an elevation of ). Then allow the pooled water filling the ED V to drain by gravity out of the water quality outlet structure. Include all retention basin outlets that would affect this drawdown curve. Include any downstream constraints such as tailwater or limiting conveyance downstream. For this example, there is no tailwater and there is a free discharge from the retention basin. 3 of 12

180 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 Retention Basin Drawdown Hydrograph: Time (hours) Storage (acre-feet) Elevation (feet) Discharge (cfs) Time (hours) Storage (acre-feet) Elevation (feet) Discharge (cfs) 4 of 12

181 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION Drain Time Volume vs. Time (0.660 ac-ft ac-ft) = 0.129ac-ft < 50% ED V Volume (ac-ft) (0.660ac-ft ac-ft) = ac-ft < ED V Time (hours) Permanent Pool In 24 hours, the volume goes from ac-ft to ac-ft. o ac-ft ac-ft = ac-ft ED V = 0.317ac-ft o 0.317ac-ft > ac-ft. It takes longer than 24 hours to drain the ED V ; therefore, it is acceptable. In 8 hours, the volume goes from ac-ft to ac-ft. o ac-ft ac-ft = ac-ft 50% ED V = ac-ft o ac-ft > ac-ft. It takes longer than 8 hours to drain 50% of the ED V ; therefore, it is acceptable. 5 of 12

182 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 Size the Primary Retention Basin Outlet: There are three main parts of a typical retention basin discharge structure: o Water quality outlet(s) o Primary outlet o Overflow weir The primary retention basin outlet normally consists of a catch basin grate and the conduit that conveys discharges from the retention basin during all but the least frequent precipitation events. The primary outlet should be sized to convey the 10-year design storm. ODOT Water Quality Catch Basin Detail (WQ-1.1): 6 of 12

183 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 Determine the 10-year peak flow rate: For the purposes of post-construction BMP calculations, all existing right-of-way is to be considered impervious. For the purpose of general conveyance sizing, runoff coefficients should be calculated using Table in ODOT s L&D Vol. 2. Q = CiA Calculate the weighted C value: 1.5 acres of tributary area are pavement and paved shoulders: C = acres of tributary area are berms and slopes 4:1 or flatter: C = 0.5 C weighted =..... = 0.58 Determine the precipitation intensity: Rainfall Area B t C = 25 min (The time of concentration is given in this example as 25 minutes because there is significant overland flow over grassed area. The time of concentration should be calculated for each site based on the site-specific flow path. 25 minutes would likely be too high of a value if the detention basin were receiving flow from a piped system. See the time of concentration calculations below.) L&D Vol. 2, Figure : Area B, 10-year frequency, 25 min t C : i = 3.4 in/hr Q = 0.58 * 3.4 in/hr * 7.5 ac = cfs Time of Concentration (t C ) Calculations: o t C = Time of overland flow (t O ) + Time of shallow concentrated flow (t S ) + Time of channel flow (t C ) o Overland Flow (t O ) t O =,./ / C = Runoff Coefficient (0.58 for this example) L = Distance to most remote location in drainage in feet (max. 300 ft.) (200 ft. in this example) s = Overland slope (percent) (0.33% in this example) t O =,../. / = minutes o Shallow Concentrated Flow (t S ) V S = Velocity of shallow concentrated flow (ft/sec) = 3.281ks 0.5 k = Intercept Coefficient (L&D Table ) = (0.457 in this example) s = Overland slope (percent) (0.33% in this example) V S = * * = 0.86 ft/sec Length of shallow concentrated flow = 200 ft. t S = 200 ft. / 0.86 ft/sec = 233 sec = 3.88 minutes 7 of 12

184 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 o Channel Flow (t C ) Manning s Equation: V =./ / V = velocity in the channel (ft/sec) r = hydraulic radius (0.69 ft. in this example) s = channel slope (0.01 ft/ft in this example) n = Manning s Roughness Coefficient (L&D Vol. 2, Table ) (0.03 in this example) V =../. / = 3.88 ft/sec. Channel length = 500 ft. (for this example) tc = 500 ft. / 3.88 ft/sec = 129 sec. = 2.15 minutes o t C = t O + t S + t C = = minutes. Use t C = 25 minutes Size the primary retention basin discharge conduit: The discharge conduit must be large enough to convey the 10-year design storm, keeping the maximum hydraulic grade line within the crown of the pipe. This example has the following conduit characteristics: o Conduit slope = ft/ft o No Tailwater; free discharge o Pipe Roughness Coefficient = (L&D Vol. 2, Section ) The minimum conduit size that conveys the 10-year peak flow (14.79 cfs) with the given characteristics is a 24-inch diameter pipe. Set the catch basin grate elevation: The ED V fills the retention basin to an elevation of ft. At water surface elevations of ft and below, all discharge should pass through the water quality outlet. (In this example, the water quality outlet is one 2.5 inch diameter orifice at ft.) The ODOT standard water quality catch basin detail (SCD WQ-1.1) calls for either Catch Basin No. 2-3 or 2-4 depending on the outlet pipe size. Both catch basins have a 6-inch high side inlet that is either 3 or 4 feet wide depending on the catch basin. See the detail: 8 of 12

185 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 ODOT Catch Basin No. 2-3 and No. 2-4: However, SCD WQ-1.1 calls for a catch basin used for a detention basin to not have the side inlet windows. Therefore, side inlets should not be included in a detention basin outlet structure. The elevation of the top of the grate should be set at the ED V elevation. Therefore, any volume above the ED V may discharge into the catch basin through the grate. o Catch basin grate elevation = ft Set the Overflow Weir Invert Elevation: The 10-year peak flow rate (14.79 cfs) should pass fully through the primary discharge. Therefore, no flow should discharge from the overflow weir until the 10-year flow rate has been exceeded. Set the overflow weir invert elevation just high enough above the catch basin grate such that the full 10-year peak flow rate is conveyed through the primary discharge. 9 of 12 July 2015

186 RETENTION BASIN EXAMPLE (CONTINUED) REFERENCE SECTION 1117 For this example, the primary discharge pipe is sized at 24 inches in diameter; therefore, Catch Basin No. 2-3 is appropriate. Catch Basin No. 2-3 has the same grate as Catch Basin No. 2-2B. The water quality catch basin has one openings to allow runoff inside; Grate No. 2-2-B. Use L&D Vol. 2, Figure to determine the necessary head above a No. 2-2-B grate to pass the 10-year peak flow rate (14.79 cfs). According to Figure , 1.25 ft of head is required to pass a flow rate of cfs. Add the necessary head to the grate elevation (797.8 ft) o ft ft = ft Set the overflow weir elevation at ft. Size the Emergency Overflow Weir and Set the Top of Basin Elevation: L&D Vol. 2, Section states that the hydraulic grade line should be checked for the 25- year storm. Calculate the peak flow rate for each design storm: o 25-year t C = 25 min and Rainfall Area B: 3.8 in/hr o 25-year storm peak flow rate: Q = CiA = 0.58 * 3.8 in/hr * 7.5 ac = cfs Calculate the required weir length for each design storm flow: o Emergency overflow weir elevation = ft o Assume a top of retention basin elevation = ft o Maximum height overflow weir = ft ft = 0.5 ft o Weir equation: Q = C*L*H 1.5 C = 3 H = 0.5 L =? o Length of a weir: L = o 25-year: L =.... = 15.6 ft Provide a 16 ft wide overflow weir. The top of basin elevation is ft. The overflow weir length could be reduced by increasing the top of basin elevation. Or the top of basin elevation can be lowered by increasing the overflow weir length. The 25-year peak flow rate must fully pass through the overflow weir without overtopping the detention basin. Flow rates greater than the 25-year peak flow rate may overtop the detention basin uncontrolled. Provide erosion protection at the overflow weir, to the bottom of the berm, and continuing downstream if there is erosion potential. 10 of 12

187 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 Design Anti-Seep Collars: Anti-seep collars reduce the conveyance of flow along pipe bedding, outside of a conduit and increase the flow path for the seepage of water. This helps protect the berm above the discharge conduit from a retention basin from internal erosion. ODOT Standard Drawing WQ-1.2 Calculate the saturated zone length along the conduit (Ls) o Ls = Y(Z+4)[1+S/(0.25-S)] o Y = depth of water during the 10-year storm o Z = slope of embankment o S = slope of conduit Maximum elevation at 10-year storm = ft Conduit elevation = ft Y = ft ft = 4.05 Z = 4 S = Ls = 4.05(4+4)[ /( )] = ft ΔLs = 0.15*Ls = 0.15 * ft = 5.0 ft Total Projection: P = W D o W = 2ft + 2 ft diameter + 2 ft = 6 ft o P = 6 ft 2 ft = 4 ft Number of collars = ΔLs / P = 5.0 ft / 4 ft = 1.25 o Minimum of 2 collars per outlet conduit o Use 2 anti-seep collars Place both anti-seep collars in the saturation zone (within ft of front edge of berm). Spacing between collars: between 10 and 25 feet 11 of 12

188 RETENTION BASIN EXAMPLE (CONTINUED) July 2015 REFERENCE SECTION 1117 Additional Considerations: Vegetate the sides of the retention basin that are above the permanent pool with Item 670 Slope Erosion Protection per L&D Vol. 2, Section For all open water carriers at each inlet and discharge from a retention basin, check the shear stress and ensure appropriate lining per L&D Vol. 2, Section For all culverts that discharge into or out of a retention basin, ensure that appropriate rock channel protection is included per L&D Vol. 2, Section Include calculated retention basin ponding elevations in the calculation of the hydraulic grade line for the upstream conveyance system per L&D Vol. 2, Section Attempt to locate structures outside of designated flood plains. If a retention basin encroaches on a flood plain, follow the flood assessment requirements in L&D Vol. 2 Section Ensure that safety criteria are met in the clear zone per L&D Vol. 1, Section Ensure that no more than one foot of permanent standing water is located within the clear zone without barrier protection, per L&D Vol. 1, Section Engage local project stakeholders in potential public safety considerations associated with retention basins. Develop a plan for how regular maintenance will be performed. o Vehicle access o Mowing o Removal of woody vegetation o Regular unclogging of the water quality outlet 12 of 12

189 January 2016 BIORETENTION CELL REFERENCE SECTION Perforated PVC Underdrain, Maximum 20' Spacing Bioretention Cell Area Provide Pretreatment per L&D Vol. 2, Sec A A Catch Basin Observation Well / Cleanout PLAN VIEW BIORETENTION CELL IN OPEN AREA WITH LEVEL SURFACE NOT TO SCALE

190 January 2016 BIORETENTION CELL (CONT.) REFERENCE SECTION Observation Well / Cleanout Excess 3" for Settling Fine Aggregate per CMS Coarse Aggregate, Size no. 78 per CMS Coarse Aggregate, Size no. 57 per CMS " 3"3" 12" 3" Maximum 12" Ponding Allowed Final Grade Bioretention Planting Soil (See Standard Note W101for Soil Mix) Minimum 3" of no. 57 Aggregate under Perforated Underdrain Peforated PVC Underdrain Subsoil SECTION A-A (BIORETENTION CELL) NOT TO SCALE Catch Basin 12" Item 611 Conduit, (See Plans for Size and Length)

191 January 2016 BIORETENTION CELL (CONT.) REFERENCE SECTION Bioretention Cell Area See Detail this page Observation Well / Cleanout Flowline of Ditch Subsoil Provide Pretreatment Per L&D Vol. 2, Sec Perforated PVC Underdrain Rounded Centerline of ditch Item 601, Tied Concrete Block Mat, Type 1Covering Earth Dike Earth Dike PLAN VIEW LINEAR BIORETENTION CELL IN GRASS DITCH NOT TO SCALE Maximum 12" Ponding Allowed Approx. 2" Thick Item 611, Tied Concrete Block Mat, Type 1 Rounded 10" Earth Dike 6:1Slope or Flatter Perforated PVC Underdrain and Non-perforated Conduit Coupler between Perforated Non-perforated PVC Underdrain Item 611Type C Conduit Outlet as Shown on the Plans PROFILE OF BIORETENTION CELL IN GRASS DITCH NOT TO SCALE

192 January 2016 BIORETENTION CELL (CONT.) REFERENCE SECTION Ditch Centerline Excess 3" for Settling Final Grade 30" Bioretention Planting Soil (See Standard Note W101 for Soil Mix) Minimum 3" of no. 57 Aggregate under Perforated Underdrain 3" 12" 3"3" Fine Aggregate per CMS Coarse Aggreage, Size no. 78 per CMS Coarse Aggregate, Size no. 57 per CMS See Plans for Bioretention Cell Width Subsoil SECTION OF BIORETENTION CELL IN GRASS DITCH NOT TO SCALE Observation Well / Cleanout 4" Type F Conduit, PVC per CMS 611, Threaded Cap 4" Subsoil Perforated PVC Underdrain OBSERVATION WELL / CLEANOUT NOT TO SCALE

193 January 2016 BIORETENTION CELL (CONT.) REFERENCE SECTION NOTES BASIN MATERIALS: Provide basin dimensions, materials, and grate as specified. Do not use side inlet windows. EROSION CONTROL: For grassed bioretention, include temporary erosion control mat Type A, B, C, or E per CMS 671 over the surface of all bioretention planting soil. BIORETENTION PLANTING SOIL: See Plan Note W101 (Bioretention Cells) for approved bioretention planting soil characteristics. PLANTINGS: If not specified on the plans, seed the bioretention cell area per CMS 659. Do not apply fertilizer or lime to the bioretention cell area. SUBSOIL: Scarify the subsoil 3" minimum before installation of aggregate into bioretention cell. BIORETENTION SIDES Construct bioretention cells with vertical sides unless otherwise specified. PAYMENT: Bioretention cell will be paid for as Iem 601, Bioretention Cell cu yd and Item 601 Tied Concrete Mat sq yd. Excavation will be paid for as Item 203, Excavation as per plan cu yd. Perforated underdrains, observation wells, and associated fittings and couplers will be paid for as Item 605, Underdrain as per plan. Non perforated underdrains will be paid for as Item 611, Outlet Pipe. Seeding and mulching for the bioretention cell will be paid for as Item 659, Seeding and Mulching sq yd. Erosion control mats will be paid for as item 671, Erosion Control Mats sq yd.

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197 Appendix A Reproducible Forms Form LD-33 LD-34 LD-35 LD-40 LD-41 LD-42 LD-50 LD-51 LD-52 LD-53 Subject County Engineer Approval Form Storm Sewer Computation Sheet Ohio Drainage Design Criteria Form Gutter Spread and Inlet Capacity Computation Sheet Ditch Computation Sheet Culvert Computation Sheet No-Rise Certification Floodplain Letter of Compliance Template Floodplain Letter of Notification Template Letter of Notification of SFHA Exemption January 2018

198 Appendix A Reproducible Forms January 2018

199 Form LD-33 Revised July 2011 Ohio Department of Transportation County Engineer Approval Form Date Submitted to District: Date Submitted to County Engineer: County - Route - Section: PID: Station Size & Type Culvert Invert Elevation Existing Channel Elevation Inlet Outlet Inlet Outlet Skew I have reviewed and hereby approve the drainage proposed for the highway designated hereon in accordance with the provisions of the Ohio Revised Code, Section County County Engineer's Signature Date Comments: LD-33.xls