City of Golden Stormwater Standards Manual

City of Golden Stormwater Standards Manual October 2012 Revised April 2014 Public Works Department Engineering Division Environmental Services Division

City of Golden Stormwater Standards Manual Summary of Revisions April 2014 revision includes the following minor updates: Add sediment barrier in sed basin detail, Appendix A Update active stormwater inspection form, Appendix C Update periodic stormwater inspection form, Appendix C Revise Stormwater Inspections, Compliance and Enforcement Fact Sheet, Appendix C October 2012 revision of the City of Golden Stormwater Standards Manual reflects the integration of the City of Golden Stormwater Quality Control Design Guidance Manual and the City s drainage standards, previously included in the Streets, Sidewalks and Drainage Specifications. October 2012 Revised April 2014 Public Works Department Engineering Division Environmental Services Division http://www.cityofgolden.net/

Table of Contents Introduction... 1 Stormwater Management... 1 Use of Manual... 1 References... 1 Stormwater Management: Drainage... 2 General Requirements... 2 Submittals... 3 Stormwater Management: Pollutants... 12 General Requirements... 12 Submittals... 13 Best Management Practices for Permanent Stormwater Control... 13 Best Management Practices for Construction... 13 Appendix A Standard Details... Appendix B Stormwater Infrastructure Certification form... Appendix C Stormwater Permit Application Packet... Appendix D Revegetation Requirements...

Section I. Introduction A. Stormwater Management Urbanization and development affect both the quantity and the quality of stormwater discharged to receiving waters. Land disturbing activities such as construction expose soil and allow increased erosion and sediment transport. After construction is completed, the increase in impervious areas such as rooftops, parking lots and paved areas decreases the opportunity for stormwater to infiltrate into the ground, increasing flow velocity and potential pollutant transport. B. Use of Manual The intent of the Stormwater Standards Manual (Manual) is to present design standards for the implementation and use of Best Management Practices (BMPs) to manage stormwater for the purposes of water quality and flood control. It will be used by city staff when reviewing stormwater management practices. Individual methods shall be selected and implemented to best fit the conditions and requirements of each site. The Public Works Director, or designee, shall be authorized to make periodic updates and technical amendments from time to time. Major revisions will be presented to City Council. C. References This Manual outlines methods for the control of stormwater for development and redevelopment. The reader is referred to specific design criteria presented in the Urban Storm Drainage Criteria Manual (USDCM), volume 3, as amended. 1

Section II. Stormwater Management A. Stormwater Management: Drainage The impervious areas associated with urbanization have been shown to increase the volume of runoff which has led to flooding in increased severity and degradation of water quality. A coordinated approach to managing the increased runoff volumes associated with development and redevelopment is critical to ensuring the safety of citizens and health of our receiving waterways. The intent of this manual is to provide standards for responsible management of runoff. 1. General Requirements a. Flood Control All development that results in a net increase of 10,000 square feet of impervious area shall provide flood control for the increased impervious area runoff. Runoff rates in the developed condition shall be attenuated and released at historic rates. b. WQCV Both the Water Quality Capture Volume (WQCV) and Excess Urban Runoff Volume (EURV) are permissible options for water quality. In the event that the WQCV is provided it shall be 120% of the calculated WQCV and shall be in addition to the 100 year volume. EURV shall be included within the 100 year volume. c. Riparian Setbacks No new development shall be permitted to construct structures or impervious surfaces within 50 of a channel designated as a major drainageway as measured from the top of bank. City of Golden Engineering Division staff will determine top of bank location when not readily apparent. d. Floodplain The City of Golden has adopted the International Building Code (IBC) 2009 Appendix G for floodplain regulations. In addition to the requirements set forth in IBC 2009 Appendix G the City shall require the following additional requirements of all development within any FEMA designated Floodplain or any flood study or FHAD adopted by the City: i. The design flood elevation for all new development shall be the Base flood elevation plus one (1) additional foot of freeboard. ii. iii. Physical map revisions in the City of Golden in which a floodway is delineated shall adhere to a half (1/2) foot rise criteria. Stream alteration activities shall not be constructed unless the project proponent demonstrates through a floodway analysis and report, sealed by a Colorado Registered Professional Engineer, that there are no adverse floodway impacts resulting from the project. This requirement only applies on stream reaches with Base Flood Elevations established. e. Standard Details With the exception of the details provided in Appendix A, the City has adopted the standard details applicable to drainage found in the latest version of the Colorado Department of Transportation 2

M & S standards and the details provided in the latest version of the USDCM. In the event that a detail for a type of facility is provided in both documents, the City of Golden Engineering Division will decide which standard detail is applicable. f. Steep Slopes Grading disturbance shall not occur on slopes over 25%. Properties with areas of greater than 25% slope should place development requiring grading disturbance on the site areas of less than 25% slope. Incidental slopes, including banks along waterways or small abnormalities of less than 100 square feet within a lot shall not be counted toward this requirement. 2. Submittals a. Drainage Report Drainage reports must be formatted in accordance with the following outline and must contain all the applicable information listed below: I. GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map: A map showing the project location within the City. The project area shall be shaded; major arterial streets labeled; and major water courses and water bodies shall be labeled 2. Township, range, section, ¼ section 3. Local streets within and adjacent to the subdivision with ROW width shown 4. Major drainageways, facilities, and easements within or adjacent to the site B. Description of Property 1. Area in acres 2. Existing ground cover (type of trees, shrubs, vegetation, general soil conditions, topography, and slope) 3. Major drainageways 4. General project description 5. Irrigation facilities 6. Proposed land use II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description 1. Reference to major drainageway planning studies such as flood hazard delineation reports, major drainageway planning reports, and flood insurance rate maps 2. Major basin drainage characteristics, existing and planned land uses 3. Identification of all irrigation facilities within the basin, which will influence or be influenced by the local drainage design B. Sub-Basin Description 1. Discussion of historic and proposed drainage patterns of the property 2. Discussion of offsite drainage flow patterns and impact on development under existing and fully developed basin conditions 3

III. DRAINAGE DESIGN CRITERIA A. Regulations: Discussion of the optional provisions selected or the deviation from the criteria, if any, and its justification B. Discussion on implementation of the "Four Step Process" including Runoff Reduction Practices, Water Quality Capture Volume, Stabilizing Drainageways and Source Control BMPs C. Development Criteria Reference and Constraints 1. Discussion of previous drainage studies (i.e., project master plans) for the site that influence or are influenced by the drainage design and how the plan will affect drainage design for the site 2. Discussion of the effects of adjacent drainage studies 3. Discussion of the drainage impact of site constraints such as streets, utilities, rapid transit, existing structures, and development or site plan D. Hydrological Criteria 1. Identify design rainfall 2. Identify runoff calculation method 3. Identify detention discharge and storage calculation method 4. Identify design storm recurrence intervals 5. Discussion and justification of other assumptions or calculation methods used that are not referenced by the criteria E. Hydraulic Criteria 1. Identify various capacity references 2. Discussion of other drainage facility design criteria used that are not referenced in the criteria 3. If there are proposed modifications to areas within the 100-year floodplain or floodway, a "Floodplain Modeling Report" must be submitted 4. If there are proposed modifications to a natural drainageway where a 100-year floodplain has not been designated, a "Floodplain Modeling Study" must be submitted F. Modifications of Criteria 1. Identify provisions by section number for which a modification is requested 2. Provide justification for each modification requested IV. DRAINAGE FACILITY DESIGN A. General Concept 1. Discussion of concept and typical drainage patterns 2. Discussion of compliance with off-site runoff considerations 3. Discussion of the content of tables, charts, figures, plates, or drawings presented in the report 4. Discussion of anticipated and proposed drainage patterns B. Specific Details 1. Discussion of drainage problems encountered and solutions at specific design points 2. Discussion of detention storage and outlet design 3. A summary table for each detention storage pond on the site to include: Stage-Storage Curve Stage-Discharge Curve Detention Pond Volume Required Detention Pond Volume Provided 4

Water Quality Capture Volume (WQCV) Water Quality Elevation Spillway Elevation Pond Freeboard Outlet(s) size(s) 4. Discussion of maintenance access 5. Discussion of easements and tracts for drainage purposes, including the conditions and limitations for use 6. Discussion of the facilities needed offsite for the conveyance of minor and major flows to the major drainageway V. CONCLUSIONS A. Compliance with Standards 1. Compliance with City of Golden Stormwater Standards Manual 2. Compliance with any existing Master Drainage Plans 3. Compliance with the City's floodplain regulations 4. Compliance with applicable State and Federal regulations B. Drainage Concept 1. Effectiveness of drainage design to control damage from storm runoff 2. Influence of proposed development on the Master Drainage Plan recommendation(s) VI. REFERENCES Reference all criteria and technical information used VII. APPENDICES A. Hydrologic Computations 1. Land use assumptions regarding adjacent properties 2. Initial and major storm runoff at specific design points 3. Historic and fully developed runoff computations at specific design points 4. Hydrographs at critical design points 5. Time of concentration and runoff coefficients for each basin B. Hydraulic Computations 1. Culvert capacities 2. Storm sewer capacity. Allowable models include StormCAD, UDSewer, FlowMaster, and Extran. Other models will be accepted on a case by case basis upon prior approval from the City 3. Street flow calculations for the 2-year and 100-year events regarding street encroachment, theoretical capacity, and allowable gutter flow 4. Storm inlet capacity including inlet control rating at connection(s) to storm sewer system 5. Open channel design 6. Check dam and/or channel drop design 7. Detention facility design including area/volume capacity, outlet capacity, soil analysis, and ground water table elevations 8. Downstream/outfall system capacity to the major drainageway system 9. Design of erosion protection measures for culverts, and storm sewer outlets C. Letters of intent to acquire all necessary off-site easements D. Water quality design calculations 5

E. Printed copies of input and output files for all computer models used in the analysis and design F. Digital copies of input and output files for all computer models used in the analysis and design b. Drainage Plan The drawings must contain all the applicable information listed below. All drawings shall be prepared by a Colorado Registered Civil Engineer and must be on a reproducible medium of one or more sheets with an outer dimension of twenty-four by thirty-four (24 x 36) inches The plan set should include the following sheets: a) Vicinity Map b) Drainage Plan c) Floodplain Plan d) Grading Plan e) Erosion Control Plan The Drainage Report and associated drawings must include the following information in aggregate: a) The name of the subdivision or project b) The date of preparation, the scale, and symbol designating true north c) The boundary lines of the subdivision or project, right-of-way lines of streets, easements and other rights of way, irrigation ditches, detention ponds, watercourses, and lot lines, with accurate bearings and distances d) Designations of all streets and other rights of way, including dimensions and names of such streets e) The location and dimensions of any easements f) Existing and proposed contours at two foot intervals. Spot elevations or one foot contours where two foot contours do not show on the property or where needed to depict the grading. Spot elevations may be needed in critical areas, especially adjacent to existing developed property g) The location, size, and type of all storm sewers h) The location, size, and type of all inlets, cross pans, manholes, and other storm sewer appurtenances i) Profile views for all subsurface drainage facilities showing their size, slope, lengths, design storm hydraulic grade lines (2-year and 100-year), cover, details of structures or City Standard details, and relationship with existing utilities j) The location, size, and type of all culverts, including box culverts k) The location, size, and type of all open channels, including irrigation ditches with profile views where applicable l) The location, size, and type of all existing utilities m) Cross-sectional views of all open channels, including irrigation ditches, trickle channels, spillway structures, etc. These views must include applicable easement/right-of-way boundaries and water surface elevations such as the 100-year storm depth, 2-year storm depth, major storm freeboard, and operating irrigation level n) Capacity, discharge, outlet structure, spillways, permanent pool water level (if any), and 100-year high water level for all detention ponds, including both the water quality and water quantity elevations. Cross-hatching of the area inundated by the 100-year water surface elevation is recommended o) Water surface profiles for all major open channels, or as required p) Show the lowest floor elevation (the basement floor elevation or the bottom of the crawl space) and grade at foundation elevations of all buildings 6

q) Spot elevations critical to describe drainage features and their function (e.g., inlets, cross pans, spillways, inlets/outlets of manholes, culverts, and storm sewers) r) Drainage sub-basin boundaries and concentration points for the developed site clearly delineated and labeled s) A summary table of site hydrology, including offsite flows entering the site for the 10-year and 100-year design storms, basin numbers, basin areas, runoff coefficients, and onsite flows for the 10-year and 100-year design storms at the concentration points t) A summary table for each detention pond on the site to include: Stage-Storage Curve Stage-Discharge Curve Detention pond volume required Detention pond volume provided Water Quality Capture Volume (WQCV) Water Quality Elevation Spillway Elevation Pond Freeboard Outlet(s) size(s) u) A vicinity map showing the project location within the city. The project area shall be shaded, and major arterial streets labeled. The map shall be a minimum size of 6" x 6", with a scale ranging from 1"=1000' to 1"=3000' v) Letters of intent to acquire all necessary offsite easements shall be included with the submittal w) If SWMM modeling is used, a sub-basin map and a SWMM schematic diagram are required to depict the sub-basins and conveyance elements represented in the model x) General notes relating to the design of the drainage features of the development are required on the utility plan cover sheet. (Additional notes are required by other departments, such as Engineering and Water/Wastewater.) The required drainage notes are as follows: 1) All street, sanitary sewer, storm sewer and water construction shall conform to City Standards and Specifications current at date of execution of the Development Agreement pertaining to this development. Any construction occurring three years after the execution of the development agreement shall require re-examination of the plans by the Director who may require that they be made to conform to standards and specifications current at that time. 2) The type, size, location, and number of all known underground utilities are approximate as shown on the drawings. It shall be the responsibility of the contractor to verify the existence and location of all underground utilities along the route of the work. Before commencing new construction, the contractor shall be responsible for locating unknown underground utilities. 3) These plans have been reviewed by the City for concept only. The review does not imply responsibility by the reviewing department, the City Engineer, or the City for accuracy or correctness of the calculations. Furthermore, the review does not imply that the quantities of the items on the plans are the final quantities required. The review shall not be construed in any reason as acceptance of financial responsibility by the City for additional quantities of items shown that may be required during the construction phase. 4) Maintenance of onsite drainage facilities shall be the responsibility of the property owners. 7

5) If fill or dredged material is discharged into waters of the United States, a USACE 404 permit is required. 6) If construction affects any Colorado Highway, a Colorado Department of Transportation Right of Way permit is required. c. Drainage Certification After construction is complete and prior to final inspection by the City the design engineer (or a Professional Engineer registered in the state of Colorado) shall submit, to the City of Golden Public Works Department, Engineering Division, a signed and sealed certification of the constructed storm facilities. The certification shall include a statement that the constructed facilities are in conformance with the approved drainage plan(s). The certification shall also include the as designed and as constructed : WQCV or EURV 10 year orifice elevation Top of pond outlet elevation 100 year restriction plate orientation Total Pond Volume Overflow elevation width and depth Trickle channel longitudinal slope Trickle channel cross section d. Stormwater Infrastructure Certification After drainage facility construction is complete and prior to final inspection by the City, the contractor shall submit to the City of Golden Public Works Department, Engineering Division a set of red line plans or as builts showing any deviations from the approved plans, a video inspection of all installed pipes and a completed Stormwater Infrastructure Certification. The Certification form can be found in Appendix B. e. Runoff Calculation Both the Colorado Urban Hydrograph Procedure (CUHP) and the Rational Method are allowable methods for runoff calculation within the watershed size limitations in the following table. Applicability of Hydrologic Methods Watershed Size (acres) Is the Rational Method Applicable? Is CUHP Applicable? 0 to 5 Yes Yes (1) 6 to 90 Yes Yes (1) 91 to 160 Yes Yes 161 to 3,000 No Yes (2) Greater than 3,000 No Yes if subdivided into smaller catchments(2) (1) If one minute unit hydrograph is used. 2) Subdividing into smaller sub catchments and routing the resultant hydrographs using SWMM may be needed to accurately model a catchment with areas of different soil types or percentages of imperviousness. 8

Detailed information on both the Rational Method and the Colorado Urban Hydrograph Procedure can be found in the Urban Storm Drainage Criteria Manual (USDCM) Volume 1. f. Conveyance Streets are an integral part of the urban drainage system and may be used for transporting storm runoff up to design limits. The design engineer should recognize that the primary purpose of streets is for traffic, and therefore the use of streets for storm runoff must be restricted. The policy of the City is to allow the use of streets for drainage within the limitations described in the following tables, subject to City approval. Allowable Use of Streets for MINOR Storm Runoff Street Functional Classification Local street Maximum Theoretical Depth No curb overtopping. Flow may spread to crown of street. Flow may spread to back of sidewalk for a 4-inch combo curb/sidewalk. Collector street No curb overtopping. Flow spread must leave at least one 10- foot lane free of water, 5 feet either side of street crown. Arterial street No curb overtopping. Flow spread must leave at least two 10- foot lanes free of water, 10 feet either side of street crown or median. Allowable Use of Streets for MAJOR Storm Runoff Street Functional Classification Maximum Theoretical Depth Residential dwellings, public, commercial and industrial Local street and collector street buildings shall not be inundated at the ground line. The depth of water at the gutter flow line shall not exceed 12 inches. Residential dwellings, public, commercial and industrial Arterial street buildings shall not be inundated at the ground line. To allow for emergency vehicles, the depth of water shall not exceed 6-inches at the street crown and 12 inches at the gutter flow line, whichever is more restrictive. g. Storm sewers Storm sewers are a part of the drainage system and are required when the other parts of the system no longer have capacity for additional runoff. Except as modified herein, the design of storm sewers shall be in accordance with the Storm Sewer section of the STREETS/INLETS/STORM SEWERS chapter of the USDCM. All new or reconstructed storm sewers shall be sized to convey the major event (100 year) flows in excess of the allowable street conveyance capacity. All direction changes, both horizontal and vertical, shall be achieved through a manhole. Bends, longitudinal bending and joint deflection are prohibited. Contractor shall submit to the City, for approval, shop drawings for all pipe and fittings. 9

Polyvinyl Chloride (PVC), High Density Polyethylene (HDPE) and Reinforced Concrete Pipe (RCP) are the only permissible pipe materials for stormwater sewer installations in the City of Golden. All pipes shall meet the material and handling specifications set forth by the Urban Drainage and Flood Control District. UDFCD specifications can be found at the websites listed below: PVC http://udfcd.org/wp-content/uploads/uploads/resources/specifications/division%2033%20-% 20Utilities/33_41_03_Polyvinyl_Chloride_Pipe.pdf HDPE http://udfcd.org/wp-content/uploads/uploads/resources/specifications/division%2033%20-% 20Utilities/33_41_01_High-Density_Polyethylene_Pipe.pdf RCP http://udfcd.org/wp-content/uploads/uploads/resources/specifications/division%2033%20-% 20Utilities/33_41_00_Reinforced_Concrete_Pipe.pdf h. Best Management Practices (BMPs) The following BMPs should be evaluated for development and redevelopment with consideration of pollutant removal, flood attenuation and long-term maintenance given site conditions and land use. For specific design criteria for the accepted BMPs listed below, refer to the most current version of the USDCM Vol. 3, Chapter 4, "Treatment BMPs" found at http://udfcd.org/wp-content/uploads/uploads/vol3%20criteria% 20manual/04_Chapter_4_Treatment_BMPs.pdf. Where more specific criteria are warranted, it is noted below: Grass Swale Grass Buffer Bioretention/Rain Garden/Porous Landscape Detention Green Roof Extended Detention Basin: Both the WQCV and full spectrum EURV are permissible options for water quality. In the event that the WQCV is provided it shall be 120% of the calculated WQCV and shall be in addition to the 100 year volume. EURV shall be included within the 100 year volume. Sand Filter Retention Pond Constructed Wetland Pond Constructed Wetland Channel Permeable Pavements Underground BMPs o Detention Vaults are prohibited in areas not within a designated Urban Renewal District. Vaults allowed to be installed within an Urban Renewal Area must meet the following: single chamber constructed of concrete have a sloped bottom be constructed with adequate access to facilitate safe maintenance o must have separate upstream water quality BMPs Underground Water Quality BMPs may be allowed for water quality purposes only, provided that they meet the USDCM removal rates and test data is available for semi arid climates. Further, the maintenance procedures of any permitted proprietary BMPs must meet the requirements of City of Golden Engineering Division. 10

The City of Golden encourages the innovative use and application of measures to control stormwater. As with any field of technology, methods and applications of BMPs designed to control stormwater are expected to grow, improve and change. Owners of land undergoing development or significant redevelopment are encouraged to utilize the best available technology. Updates to this Manual will be used periodically to reflect major changes in methodology or application of BMPs or other control measures. i. Operation and Maintenance An important part of all storm drainage facilities is the continued maintenance of the facilities to ensure they will function as designed. Inspection access and maintenance access must be provided to all storm drainage facilities to ensure water quality and continuous operational capability of the system. Said access shall be granted via easement, on the plat, or by other instrument to the City. The property owner shall be responsible for the maintenance of all drainage facilities including, but not limited to, inlets, pipes, channels, ditches, hydraulic structures, and detention basins located on their lands unless modified by the subdivision improvements agreement. j. Right to Enter To ensure the public health, safety and welfare, the City shall have the right to enter said property for the purposes of inspection, operation and/or maintenance of the storm drainage facilities. Should a property owner fail to adequately maintain and/or operate storm drainage facilities, and after sufficient notice is provided by the City, the City may perform maintenance. All such maintenance costs incurred by the City will be assessed to the property owner. k. Easements The easements required to provide adequate inspection, operation and/or maintenance access are as follows: Facility Type Minimum Easement Width Single pipe 20 minimum width. Pipe centered in easement. An additional 2 width for every 1 of depth over 5 as measured from invert. Multiple pipes 10 minimum on either side from outside edge of pipe(s). Additional 1 of width on either side of pipe(s) for every 1 of depth over 5 as measured from invert. Q100 < 20 cfs: 20 feet Open channels & swales Q100 <100cfs: 25 feet Q100 >101cfs: see USDCM vol.1 Sufficient to contain storage, freeboard, release structures, and Detention basins associated facilities, plus no less than 10 feet for inspection and maintenance access around the entire perimeter. For multiple lots, a dedicated tract of land is required. 11

Section II. Stormwater Management cont. B. Stormwater Management: Pollutants - Sources and Controls Commonly recognized pollutants in urban stormwater runoff include sediment, nutrients, pathogens, road salts, hydrocarbons, metals, temperature, and volume. Structural and Non-structural BMPs are used to prevent, reduce and/or remove pollutants in stormwater flows and/or maintain/restore hydrologic conditions. This Manual provides design criteria to minimize pollutants and reduce impacts to stormwater quality that occur during construction, and provide long-term stormwater management. l. General Requirements a. Water Quality Permanent water quality control to minimize pollutants is required for any activity resulting in, or contributing to, a total disturbed area greater than one half (½) acre and areas less than one half (½) acre which are part of a Common Plan of Development or Sale. This requirement may not apply when: i. land disturbance to undeveloped land that will remain undeveloped following disturbance and will be reclaimed in accordance with the City of Golden Revegetation Requirements. ii. disturbance is associated with road rehabilitation that does not increase the impervious footprint. b. Design Standards Stormwater quality measures shall be integrated into the design. Where open space areas are required the design must allow, at a minimum, the first inch of stormwater runoff to travel through swales, rain gardens, or other permeable surfaces. All measures shall be designed to promote water quality of stormwater run-off through the use of BMPs. c. Stormwater Quality Permit A Stormwater Quality Permit is required for any activity resulting in, or contributing to, a total disturbed area greater than one half (½) acre and areas less than one half (½) acre which are a part of a Common Plan of Development or Sale. A State Permit for Stormwater Discharges Associated with Construction Activities is required only if more than five acres will be disturbed. The City is a designated Qualifying Local Program by the Colorado Department of Public Health and Environment Water Quality Control Division. Construction sites less than five (5) acres are automatically covered under the State s Stormwater Permit for Construction Activities with a City permit. Sites greater than five (5) acres require a State Stormwater Construction Permit in addition to the City permit. Contact CDPHE at https://www.colorado.gov/pacific/cdphe/wq-construction-permits or 303-692-3500 for more information. 12

2. Submittals a. Stormwater Quality Permit Application A Permittee must be designated on the permit. The Permittee must be an individual person who will be the responsible party for the project. Authorized agent(s) are typically site personnel who can ensure quick response to BMP repairs and/or failures. b. Stormwater Management Plan Please refer to the SWMP Fact Sheet in Appendix A for plan requirements. c. Performance Security The Performance Security must be a check or an irrevocable letter of credit. The amount is based on the cost of material and installation of all BMPs identified on the SWMP, plus the amount to stabilize the entire proposed disturbed area (seed and mulch). The Performance Security will only be used in the event that the City has to take corrective action. Such action will follow a written request to the Permittee. When the City must utilize the Performance Security, a 15% administrative fee will be assessed and drawn from the Performance Security. If the City does not draw from the Performance Security it will be returned upon final stabilization, plus interest at the rate currently earned by the City. It is the responsibility of the Permittee to request the release of the Performance Security. 3. Best Management Practices (BMPs) for Permanent Stormwater Control The BMPs in Part II.A.2.h. should be evaluated for development and redevelopment with consideration of pollutant removal, flood attenuation and long-term maintenance given site conditions and land use. For specific design criteria for the accepted BMPs, refer to the most current version of the USDCM Vol. 3, Chapter 4, "Treatment BMPs" found at http://udfcd.org/wp-content/uploads/uploads/vol3 criteria manual/04_chapter_4_treatment_bmps.pdf. Where more specific criteria are warranted, it is noted in Part II.A.2.h. The City of Golden encourages the innovative use and application of measures to control stormwater. As with any field of technology, methods and applications of BMPs designed to control stormwater are expected to grow, improve and change. Owners of land undergoing development or significant redevelopment are encouraged to utilize the best available technology. Updates to this Manual will be used periodically to reflect major changes in methodology or application of BMPs or other control measures. 4. Best Management Practices (BMPs) for Construction The following BMPs should be evaluated for appropriateness with consideration of site conditions and the type of construction, to control erosion and sediment and waste. For specific design criteria and construction details for the accepted BMPs listed below, refer to the most current version of the USDCM Vol. 3, Chapter 7, "Construction BMPs" found at http://udfcd.org/wp-content/uploads/uploads/vol3 criteria manual/chapter 7 Construction BMPs.pdf. Where more specific criteria are warranted, it is noted below: 13

Erosion Controls Sediment Controls Site Management Materials Management Surface Roughening Silt Fence Construction Concrete Washout Sequencing/Phasing Temporary and Sediment Control Log Protection of Existing Stockpile Management Permanent Seeding (1) Vegetation Soil Binders Straw Bale Barrier Construction Fence Good Housekeeping Practices Mulching (1) Rock Sock Vehicle Tracking Control Materials Management Compost Blanket/Berm Rolled Erosion Control Products (1) Temporary Slope Drain Temporary Outlet Protection Rough Cut Street Control Earth Dikes/Drainage Swales Terracing Inlet Protection Sediment Basin Sediment Trap Vegetative Buffers Chemical Treatment Stabilized Construction Roadway Stabilized Staging Area Street Sweeping/Vacuuming Temporary Diversion Channel Dewatering Operations Temporary Stream Crossing Temporary Batch Plant Check Dams Paving and Grinding Operations Streambank Stabilization Wind Erosion/Dust Control (1) Refer to the City of Golden Revegetation Requirements, Appendix D Concrete Washout The City of Golden encourages the innovative use and application of measures to control stormwater. As with any field of technology, methods and applications of BMPs designed to control stormwater are expected to grow, improve and change. Owners of land undergoing development or significant redevelopment are encouraged to utilize the best available technology. Updates to this Manual will be used periodically to reflect major changes in methodology or application of BMPs or other control measures. 14

Appendix A Standard Details Storm Inlet Tie in City Storm Manhole Lids Sediment Barrier in Sediment Basin Cut Back Curb 15

P'TTERtl,.' llltlllluii JF EIGIFF ( ) lflciies i "l'ci i' lll"fl 11!1 fllli' 11)1 IHAM! Iii' t\l 1111 I\IEW PIPE!i'i"ERI f\e i'lfl6/ PIPE c9111 I PF 1 Ml JIMUM OF TOJ (1 O) l JCI IES ABOVE Tl IE EXISTl IC FLOOR OF TFIE l ILET. CUT MUST BE HWH l ISILJE TO Po:EVE IT SPALU IG OF IMLE I WAI I A DR( Iii ARC ORE E!f;Hi 11,H HES STEP 2: AFTER PLACING NEW PIPE, CUT PIPE FLUSH WITH INSIDE OF INLET WALL AND POUR PATCH AND EXTERNAL COLLAR MONOLITHICALLY AGAINST A FORM PLACED ON INSIDE WALL USE #5 REBAR AT FOUR CORNERS OF PATCHED AREA TO COLLAR AND #4 AROUND COLLAR. COLLAR SHALL BE A MINIMUM OF TWELVE (12) INCHES LARGER THAN THE OUTSIDE DIAMETER OF THE NEW STORM PIPE AND A MINIMUM OF SIX (6) INCHES THICK. +" I,-------7 I #5 + I..._ I MINI I...,, I I I \.--,-,. -.,. J L.':' J COLLAR I I 6" I MIN 1 o" MIN 6" MIN STEP 3: REPAIR ANY IRREGULARITIES ON INSIDE OF INLET WALL WITH NON-SHRINK GROUT. DIRECTOR OF PUBLIC WORKS APPR U? A _. CITY EN DEPARTMENT OF PUBLIC WORKS TIE INTO EXISTING INLET WITH NEW STORM PIPE SCALE: NTS DA TE: FEB 2007 DETAIL NO. X

L 2" _r [51mm] 3" [76mm] TOP OF COVER r---- 23[ 6¼ m] IA 1" (25mm) LETTERING (RECESSED FLUSH) -------- LETTERING 1 /2" [13mm] LETTERING RECESSED 1" (25mm) LETTERING RECESSED FLUSH I I I [25mm] 1 " _1 L 7 1/4" I [184mm1 20 11/16" DIA. [526mm] --------i SECTION OF COVER r! 7/8" [22mm] BOTTOM OF COVER PICKSLOT DETAIL...J MACHINED SURFACE EAST JORDAN IRON WORKS, INC. P.O. BOX 439 EAST JORDAN, Ml. 49727 1-800-874-4100 FAX 231-536-4458 DRAWN SMH APPROVED DATE 12/03/01 DATE 2405ACOVER PRODUCT NO. 00240574 CATALOG NO. 2405A REF. PRODUCT DRAWING 00240573 EST. WT. COVER: 135 LBS 61kg OPEN AREA N/A MAT'L SPEC. COVER - GRAY IRON ASTM A48 CL35 LOAD RATING HEAVY DUTY

GRAVEL CYLINDER ABUTS AGAINST SIDE OF STRUCTURE 2x2 STAKES WASHED ¾" GRAVEL IN WIRE CYLINDER OR SEDIMENT CONTROL LOG (TYP) 36" BARRIER TO BE IMBEDDED TWO INCHES INTO SOIL SEDIMENT BARRIER FOR OUTLET STRUCTURE CITY OF GOLDEN SEDIMENT BARRIER DEPARTMENT OF PUBLIC WORKS SCALE: NTS DA TE: JUNE 2 006 DETAIL NO. IP

Appendix B Stormwater Infrastructure Certification 16

CITY OF GOLDEN Stormwater Infrastructure Certification 1465 10 TH STREET GOLDEN, CO 80401 JOE PUHR CIVIL ENGINEER 303-384-8115 (FAX) 303-384-8161 TO BE COMPLETED BY DESIGN ENGINEER AND RETURNED PRIOR TO ISSUANCE OF CERTIFICATE OF OCCUPANCY Property Location Address: Location Description: Permit Number: Parcel Size (acre): Permanent BMP Type: Check all that apply. Extended Detention Basin Retention Pond Bioretention (PLD, Rain Garden) Grass Swale Grass Buffer Sand Filter Constructed Wetland Pond Green Roof Constructed Wetland Channel Permeable Pavement Stormwater Collection System: If additional space is needed complete on additional form and attach. Pipe System: Size: Length: Material: Size: Length: Material: Surface System: (gutters, pans, channels, etc...) Width(ft): Depth(ft): Max. Longitudinal Slope(%): Surface Material: Width(ft): Depth(ft): Max. Longitudinal Slope(%): Surface Material: Flood Control: Design 100 Year Volume(CF): Constructed 100 Year Volume(CF): Design 100 Year WSEL: Constructed 100 Year WSEL: Design 10 Year Volume(CF): Constructed 10 Year Volume(CF): Design 10 Year WSEL: Constructed 10 Year WSEL: Water Quality: Design WQCV(CF): Constructed WQCV(CF): Design WQCV WSEL: Constructed WQCV WSEL: Affix Professional Engineer Seal I hereby certify that the stormwater and drainage facilities for the above referenced project have been constructed in conformance with the approved design. Further I certify that any deviation from the design has been documented and approved, in writing, by the City of Golden and that said documentation has been provided to the City of Golden. Signature: Date: Page 1 of 1

Appendix C Stormwater Permit Application Packet Permit Fact Sheet Fee Schedule Permit Application SWMP Fact Sheet Inspections, Compliance and Enforcement Fact Sheet Inspection Report active Inspection Report periodic 17

CITY OF GOLDEN Stormwater Quality Permit Fact Sheet 1445 TENTH STREET GOLDEN, CO 80401 303-384-8188 (FAX) 303-384-8161 Rev Sept 2012 Why is a Stormwater Quality Permit Required? The stormwater program is mandated under the National Pollutant Discharge Elimination System (NPDES), a component of the Clean Water Act. The requirement is intended to reduce the amount of pollutants entering streams, rivers, lakes, and wetlands as a result of runoff from residential, commercial and industrial areas. Large construction sites have been under a requirement to obtain permit coverage since 1992 (Phase I of the program). Small construction sites have been under a requirement to obtain permit coverage since July 1, 2002. When is a Stormwater Quality Permit Required from the City? A Stormwater Quality Permit is required if you will disturb one half acre or more ( 1/2) OR if you will disturb less than one half acre that is part of a larger common plan of development or sale. A common plan of development or sale includes sites where multiple, separate and distinct construction activities may be taking place at different times, on different schedules, or under separate ownership, but under a single plan. This includes, but is not limited to, phased projects with multiple filings or lots, and projects in a contiguous area that may be unrelated but still under the same contract. This also includes development of all lots and parcels within an approved subdivision or Planned Unit Development, regardless of the size of the individual lots or parcels that occurs within the first five years following recordation of the final subdivision plat or Planned Unit Development document. When is a Stormwater Permit Required from the State? The City is a designated Qualifying Local Program by the Colorado Department of Public Health and Environment Water Quality Control Division. Construction sites less than five acres are automatically covered under the State s Stormwater General Permit for Construction Activities with a City permit. Sites greater than five acres require a State Stormwater Construction Permit in addition to the City permit. Contact CDPHE at https://www.colorado.gov/pacific/cdphe/wq-construction-permits or 303-692-3500 for more information. What is Necessary to Obtain a Stormwater Quality Permit? Permit application A Permittee must be designated on the permit. The Permittee must be an individual person who will be the responsible party for the project. Authorized agent(s) are typically site personnel who can ensure quick response to BMP repairs and/or failures. Stormwater Management Plan (SWMP) Please refer to the SWMP Fact Sheet for plan requirements. Performance Security Must be a check or an irrevocable letter of credit. The Performance Security is based on the cost of material and installation of all BMPs called for on the SWMP. The Performance Security will only be used in the event that the City has to take corrective action. Such action will follow a written request to the Permittee. When the City must utilize the Performance Security a 15% administrative cost will be assessed and drawn from the Performance Security. If the City does not draw from the Performance Security it will be returned upon final stabilization, plus interest at the rate currently earned by the City. It is the responsibility of the Permittee to request the release of the Performance Security.

CITY OF GOLDEN Stormwater Quality Permit Fee Schedule 1445 TENTH STREET GOLDEN, CO 80401 303-384-8188 (FAX) 303-384-8161 Effective January 1, 2010, per City of Golden Resolution 1997, the following fees will be assessed: Stormwater Quality Permit $350 for initial permit and SWMP review Stormwater Quality Permit renewal - $125 for annual renewal Stormwater Quality Permit reinspection fee - $40 The Performance Security is a separate requirement. Please see the Permit Application.

CITY OF GOLDEN Stormwater Quality Permit Application 1445 TENTH STREET GOLDEN, CO 80401 303-384-8188 (FAX) 303-384-8161 Permit required for all land disturbances equal to or greater than ½ acre OR if you will disturb less than one half acre that is part of a larger common plan of development or sale. Project Information Project Name: Address/Location: Contact Information Owner Name: Contact Person: Address: Phone: Mobile: Fax: Email: Contractor Name: Contact Person: Address: Phone: Mobile: Fax: Email: Other Name: Contact Person: Address: Phone: Mobile Fax: Email: Designate a permittee from the above list: List, in addition to the permittee, site personnel who will have authority to make modifications:

Project Information: Project Size (acres): Brief Description of Project: Project Schedule: (provide further detail with the Stormwater Quality Management Plan) Expected work start date: Expected work completion date: Performance Security: Stormwater Quality Control Features: (for security escrow calculation) Item description Quantity Unit $/Unit Total Total Performance Security $ As a condition for the issuance of a stormwater quality permit, applicants shall be required to provide security in the form of cash escrow or an irrevocable letter of credit. The amount of the security shall be based upon the cost of the work required to ensure compliance with the permit s terms and conditions. The security, with interest at the rate currently earned by the city, less any deductions, shall be released upon the city s determination that the Permittee has successfully completed all work required by the permit. If the Permittee does not successfully complete all required work or violates any requirement of the permit, the city may take corrective measures and charge the cost of such to the Permittee. Such costs shall include the actual cost of any work deemed necessary by the city plus administrative and inspection costs and penalties pursuant to the city s stormwater quality enforcement policy. In determining the cost of work, a 15% administrative fee shall be assessed. If the total of such costs exceeds the security, the Permittee shall be responsible for payment of the remaining balance within thirty calendar days of receipt of an accounting of such from the city. It is the Permittee s responsibility to request a release of the Performance Security. Please note that eligibility for a full release is determined by adequate permanent stormwater quality control features, including established vegetation. In most cases, a minimum of one year from the date of seeding is necessary to determine vegetation establishment. NOTE: This permit is separate from any permits required by the Colorado Department of Public Health and Environment, Water Quality Control Division under the Colorado Discharge Permit System. FOR OFFICE USE Application received: Stormwater Quality Control Plan received: Total Performance Security collected: $ Date paid: Method of Payment:

CITY OF GOLDEN Stormwater Management Plan Fact Sheet 1445 TENTH STREET GOLDEN, CO 80401 303-384-8188 (FAX) 303-384-8161 Rev Sept 2012 A Stormwater Management Plan (SWMP) is required for a City of Golden Stormwater Quality Permit. A SWMP must include a description of all stormwater management controls that will be implemented as part of the construction activity to control pollutants in stormwater discharges. Consult the City of Golden Stormwater Standards Manual for approved practices and details. The Manual can be found at http://www.cityofgolden.net/media/stormwaterstandardsmanual.pdf. Refer to the CDPHE Water Quality Control Division for CDPS requirements and a more thorough discussion on preparing a SWMP at https://www.colorado.gov/pacific/sites/default/files/stormwater MANAGEMENT PLAN PREPARATION GUIDANCE.pdf. The SWMP shall be prepared in accordance with good engineering, hydrologic and pollution control practices. The SWMP does not need to be prepared by a registered engineer. The Plan must describe the implementation of Best Management Practices (BMPs) that will be used to reduce the pollutants in stormwater discharges associated with construction activity and post-construction runoff. The SWMP must be regularly updated and reflect site conditions at all times. Possible modifications may include replacing BMPs, adding BMPs, and identifying additional potential sources of pollution. Hand-written notations, initialed and dated, are adequate for most plan updates. An efficient record-keeping system is a helpful tool in managing inspection and maintenance reports. It is strongly recommended that a logbook be maintained for inspection reports, maintenance records, spill response, weather conditions, training, correspondence, etc. The documents must be kept on site when construction activities are occurring (site office, trailer, box or truck) and be made available to EPA, State and local inspectors. SWMP Contents The following should be used as a guide in preparing the SWMP. Each item must be addressed in the SWMP, or referenced in the SWMP if another plan or document containing the information will be used. 1. Stormwater Quality Statement Include the following statement on the Plan: Stormwater quality best management practices shall be implemented to minimize soil erosion, sedimentation, increased pollutant loads and changed water flow characteristics resulting from land disturbing activity, to the maximum extent practicable, so as to minimize pollution of receiving waters. 2. Site Description a) A description of the construction activity b) A proposed construction schedule c) Total area of the site, and total disturbed area, including offsite staging/storage areas d) A description of the soil and soil erosion potential e) A description of the existing vegetation at the site, including coverage

2. Site Description cont. f) The location and description of potential pollution sources. At a minimum, each of the following must be evaluated and identified in the SWMP if determined to be a potential pollution source: i) Disturbed and stockpiled soil, including dust and contaminated soil ii) Vehicle tracking iii) Materials handling and material storage iv) Equipment maintenance and fueling v) Waste management including concrete washout vi) Asphalt or concrete batch plants g) The location and description of any anticipated non-stormwater discharges such as uncontaminated springs and landscape irrigation return flows. Note that construction dewatering cannot be discharged to surface waters or to storm sewer systems without separate CDPS permit coverage. Uncontaminated dewatering water can be discharged to the ground if it is identified in the SWMP with BMPs adequate to control pollutants, and if the discharge does not leave the site as surface runoff. h) The name of the receiving water(s) and the size, type and location of any outfall or, if the discharge is to a municipal separate storm sewer, the name of the system, the location of the storm sewer discharge, and the ultimate receiving water(s) 3. Location and description of appropriate control measures (BMPs) The Plan must indicate locations for and descriptions of existing control measures and additional control measures that will be used. Approved details must be included for each BMP indicated. The plan should clearly describe the implementation of BMPs relevant to each phase of site development: a) before clearing and grading begins, b) during all phases of construction (temporary construction BMPs) c) post-construction/final stabilization (permanent BMPs) d) identify staging areas, materials handling and material storage, and spill prevention measures appropriate to the site 4. Inspection and Maintenance Procedures The plan must include inspection and maintenance procedures to ensure BMPs are effective and in good operating condition. The following are required minimum procedures: a) Inspections 1) Perform every 14 days, and within 24 hours of a stormwater event that causes surface erosion. Perform every month on sites where construction is complete, but final stabilization is pending 2) During each inspection, observe disturbed areas, the site perimeter, material storage areas, and BMPs 3) Complete an inspection report for each inspection performed 4) Keep inspection reports on site b) Maintenance 1) Perform maintenance and repairs as soon as possible on items or areas identified in the inspection report. Most repairs should be completed within 24 to 48 hours. 2) Perform maintenance as indicated in the City of Golden Stormwater Standards Manual, per manufacturer s specifications, or other sources determined to be acceptable