Chapter 23. Stormwater Management and Soil, Erosion and Sedimentation Control

Transcription

1 Chapter 23 Stormwater Management and Soil, Erosion and Sedimentation Control Part 1 General Provisions Statement of Findings Purpose Statutory Authority Applicability Compatibility with Other Ordinance Requirements Landowner Responsibility Definitions Part 2 Definitions Part 3 Soil, Erosion and Sedimentation Control A. Soil Erosion and Sedimentation Control Measures Required for Land Development Earth Disturbance Submission of Soil Erosion and Sedimentation Control Plan Soil Erosion and Sedimentation Control Requirements Control Requirements for Well Drilling B. Soil Erosion and Sedimentation Control Plan Requirements Preliminary Plan Requirements Final Plan Requirements Part 4 Stormwater Management Exemptions General Requirements General Stormwater Management Requirements Runoff Capture Volume Requirements (RCv) Water Quality Requirements Stormwater Peak Discharge Rate Control Requirements Design Criteria for Stormwater Management Facilities Calculation Methodology Erosion and Sedimentation Requirements for Infiltration BMPs 23-1 Final Draft

2 Part 5 Drainage Plan Requirements General Requirements Drainage Plan Contents Plan Submission Drainage Plan Review Modification of Plans Resubmission of Disapproved Drainage Plans Schedule of Inspections Part 6 Inspections Part 7 General General Municipality Drainage Plan Review Fee Expenses Covered by Fees Part 8 Maintenance Responsibilities Performance Guarantee Maintenance Responsibilities Maintenance Agreement for Privately Owned Stormwater Facilities Municipal Stormwater Maintenance Fund Post-Construction Maintenance Inspections Right-of-Entry Notification Enforcement Public Nuisance Penalties Appeals Part 9 Enforcement and Penalties Final Draft 23-2

3 Stormwater Management Part 1 General Provisions Statement of Findings. The Borough Council of the Borough of Carroll Valley finds that: A. Inadequate management of accelerated stormwater runoff resulting from development throughout a watershed increases flood flows, volume and velocities, thereby contributes to erosion and sedimentation, overtaxes the carrying capacity of existing streams and storm sewers, greatly increases the cost of public facilities to convey and manage stormwater, undermines floodplain management and flood reduction efforts in upstream and downstream communities, reduces groundwater recharge, and threatens public health and safety. B. A comprehensive program of stormwater management, including reasonable regulation of development and activities causing increased stormwater runoff volume and velocity as well as accelerated erosion, is fundamental to the public health, safety, welfare, and the protection of the people of the Borough and all the people of the Commonwealth, their resources, and the environment. (Ord. 6-03, 7/15/2003, 101) Purpose. The purpose of this Chapter is to promote health, safety, and welfare within the Borough by minimizing the damages described in A of this Chapter through provisions designed to: A. Manage runoff and erosion and sedimentation problems at their source by regulating activities that cause these problems. B. Utilize and preserve the existing natural surface and subsurface drainage systems. C. Encourage recharge of groundwater where appropriate and prevent degradation of groundwater quality. D. Maintain existing flows and quality of streams and watercourses in the Borough and the Commonwealth. E. Preserve and restore the flood-carrying capacity of streams and floodplains. F. Provide proper maintenance of all permanent stormwater management facilities that are constructed in the Borough. G. Provide performance standards and design criteria for watershed-wide stormwater management and planning. (Ord. 6-03, 7/15/2003, 102) Statutory Authority. The Borough is empowered to regulate land use activities that affect runoff by the Authority of the Act of July 31, 1968, P.L. 805, No. 247, the Pennsylvania Municipali Final Draft

4 Borough of Carroll Valley ties Planning Code, as amended by Act 170 of December 21, 1988 and Act 131 of December 14, 1992, 53 P.S et seq., and the Borough Code, 53 P.S et seq. (Ord. 6-03, 7/15/2003, 103) Applicability. This Chapter shall only apply to permanent stormwater management facilities constructed as part of any of the regulated activities listed in this Section. Local stormwater management design criteria (e.g., inlet spacing, inlet type, collection system design and details, outlet structure design, etc.) shall continue to be regulated by the applicable Borough ordinances or at the Borough Engineer s discretion. The following activities are defined as regulated activities and shall be regulated by this Chapter: A. Land development. B. Subdivision. C. Construction of new or additional impervious or semi-pervious surfaces (driveways, parking lots, etc.). D. Construction of new buildings or additions to existing buildings. E. Diversion or piping of any natural or man-made stream channel. F. Installation of stormwater management facilities or appurtenances thereto. (Ord. 6-03, 7/15/2003, 104) Compatibility with Other Ordinance Requirements. Approvals issued pursuant to this Chapter do not relieve the applicant of the responsibility to comply with or to secure required permits or approvals for activities regulated by any other applicable code, rule, statute, or ordinance. (Ord. 6-03, 7/15/2003, 107) Landowner Responsibility. The granting of an exemption, permit, or approval by the Borough, does not relieve the applicant from assuring that stormwater runoff from the development site will not cause injury to other persons or property or the waters of the Commonwealth. (Ord. 6-03, 7/15/2003, 108) Final Draft 23-4

5 Stormwater Management Part 2 Definitions Definitions. For the purposes of this Chapter, certain terms and words used herein shall be interpreted as follows: A. Words used in the present tense include the future tense; the singular number includes the plural, and the plural number includes the singular; words of masculine gender include feminine gender; and words of feminine gender include masculine gender. B. The word includes or including shall not limit the term to the specific example but is intended to extend its meaning to all other instances of like kind and character. C. The word person includes an individual, firm, association, organization, partnership, trust, company, corporation, or any other similar entity. D. The words shall and must are mandatory; the words may and should are permissive. E. The words used or occupied include the words intended, designed, maintained, or arranged to be used, occupied or maintained. Accelerated erosion - the removal of the surface of the land through the combined action of human activity and the natural processes of a rate greater than would occur because of the natural process alone. Agricultural activities - the work of producing crops and raising livestock including tillage, plowing, disking, harrowing, pasturing and installation of conservation measures. Construction of new buildings or impervious area is not considered an agricultural activity. Alteration - as applied to land, a change in topography as a result of the moving of soil and rock from one location or position to another; also the changing of surface conditions by causing the surface to be more or less impervious; land disturbance. Applicant - a landowner or developer who has filed an application for approval to engage in any regulated activities as defined in of this Chapter. BMP (Best Management Practice) - stormwater management practice structures, facilities, systems and techniques to maintain or improve the water quality, runoff capture volume and/or peak discharge rate of surface runoff. Buffer area - (1) Pervious Buffer Area. Area surrounding impervious cover area that, because of its natural infiltration and retention characteristics can be used to manage stormwater runoff. Percent ratio of pervious area to impervious area must be a minimum of 30 percent to 70 percent for pervious area to be considered as a buffer. (2) Riparian Buffer. Land corridor along stream channels that is 23-5 Final Draft

6 Borough of Carroll Valley sufficiently vegetated and wide so as to treat water quality and retain stormwater runoff. (3) Channel Erosion. The widening, deepening, and headward cutting of small channels and waterways, due to erosion caused by moderate to large floods. (4) Channel Protection Runoff Volume. Volume of stormwater that must be managed to protect a stream channel from erosion. The volume of runoff that creates a bankfull flow in a stream, usually associated with the 1.5-year design storm. (5) Cistern. A reservoir or tank for storing rainwater, commonly underground. (6) Conservation BMPs. Stormwater management practices that preserve the natural drainage, retention, and infiltration capacity of the land. Example: excluding riparian areas, woodlands and steep slopes from potential development area. (7) Conservation District. The Adams County Conservation District. Culvert - A structure with appurtenant works, which carries a stream under or through an embankment or fill. (8) Cover Number (CN). Dimensionless number indicating pervious nature of a land cover as defined in TR-55, SCS, (9) Culvert. A structure with appurtenant works, which carries a stream under or through an embankment or fill. (10) Dam. An artificial barrier, together with its appurtenant works, constructed for the purpose of impounding or storing water or another fluid or semi-fluid, or a refuse bank, fill or structure for highway, railroad or other purposes which does or may impound water or another fluid or semifluid. (11) Design Storm. The magnitude and temporal distribution of precipitation from a storm event measured in probability of occurrence (e.g., a 5-year storm) and duration (e.g., 24-hours), used in the design and evaluation of stormwater management systems. (12) Designee. The agent of the Borough involved with the administration, review or enforcement of any provisions of this Chapter by contract or memorandum of understanding. (13) Detention Basin. An impoundment structure designed to manage stormwater runoff by temporarily storing the runoff and releasing it at a predetermined rate. Design BMPs - stormwater management practices incorporated into a low impact development design that mimic natural drainage, retention, and infiltration capacity of the land. Example: disconnection of storm gutters, green roofs, minimal grading, and grubbing. (1) Mitigation BMPs. Engineered bio-retention and structural stormwater management practices. Example: detention and retention ponds, infiltration trenches, swales. Developer - a person, partnership, association, corporation, or other entity, or Final Draft 23-6

7 Stormwater Management any responsible person therein or agent thereof, that undertakes any regulated activity of this Chapter. Development site - the specific tract of land for which a regulated activity is proposed. Down-slope property line - that portion of the property line of the lot, tract, or parcels of land being developed located such that all overland or pipe flow from the site would be directed towards it. Drainage conveyance facility - a stormwater management facility designed to transmit stormwater runoff and shall include streams, channels, swales, pipes, conduits, culverts, storm sewers, etc. Drainage easement - a right granted by a landowner to a grantee, allowing the use of private land for stormwater management purposes. Drainage permit - a permit issued by the Borough after the drainage plan has been approved. Said permit is issued prior to or with the final Borough approval. Drainage Plan - the documentation of the stormwater management system, if any, to be used for a given development site, the contents of which are established in Part 5. Earth disturbance - any activity including, but not limited to, construction, mining, timber harvesting and grubbing which alters, disturbs, and exposes the existing land surface. Erosion - the movement of soil particles by the action of water, wind, ice, or other natural forces. Erosion and sediment pollution control plan - a plan, which is designed to minimize, accelerated erosion and sedimentation pursuant to 25 Pa.Code, Chapter 102. Evapotranspiration - uptake (transpiration) by vegetation of moisture and evaporation from vegetation surfaces. Existing conditions - the initial condition of a project site prior to the proposed construction. If the initial condition of the site is undeveloped land, the land use shall be considered as meadow unless the natural land cover is proven to generate lower curve numbers (CN) or Rational C value, such as forested lands. Flood - a general but temporary condition of partial or complete inundation of normally dry land areas from the overflow of streams, rivers, and other waters of this Commonwealth. Floodplain - any land area susceptible to inundation by water from any natural source or delineated by applicable Department of Housing and Urban Development, Federal Insurance Administration Flood Hazard Boundary - Mapped as being a special flood hazard area. Also included are areas that comprise Group 13 Soils, as listed in Appendix 23-A of the Pennsylvania Department of Environmental Protection (DEP) Technical Manual for Sewage Enforcement Officers (as amended or replaced from time to time by DEP). Floodway - the channel of the watercourse and those portions of the adjoining floodplains that are reasonably required to carry and discharge the 100-year frequency flood. Unless otherwise specified, the boundary of the floodway is as 23-7 Final Draft

8 Borough of Carroll Valley indicated on maps and flood insurance studies provided by FEMA. In an area where no FEMA maps or studies have defined the boundary of the 100-year frequency floodway, it is assumed, absent evidence to the contrary, that the floodway extends from the stream to 50 feet from the top of the bank of the stream. Forest management/timber operations - planning and activities necessary for the management of forestland. These include timber inventory and preparation of forest management plans, silviculture treatment, cutting budgets, logging road design and construction, timber harvesting, site preparation and reforestation. Freeboard - a vertical distance between the elevation of the design high water and the top of a dam, levee, tank, basin, or diversion ridge. The space is required as a safety margin in a pond or basin. Grade - a slope, usually of a road, channel or natural ground specified in percent and shown on plans as specified herein. (To) Grade - to finish the surface of a roadbed, top of embankment or bottom of excavation. Grassed waterway - a natural or constructed waterway, usually broad and shallow, covered with erosion-resistant grasses, used to conduct surface water from cropland. Groundwater recharge - replenishment of existing natural underground water supplies. Impervious surface - a surface that prevents the percolation of water into the ground. (1) Connected impervious surface. Impervious cover area with insufficient surrounding buffer area to naturally manage stormwater runoff - percent ratio of impervious to pervious area greater than 30 percent to 70 percent. (2) Unconnected Impervious Surface. Impervious cover area with adequate surrounding buffer area to naturally manage stormwater runoff percent ratio of impervious to pervious area less than or equal to 30 percent to 70 percent. (3) Impoundment. A retention or detention basin designed to retain stormwater runoff and release it at a controlled rate. Infiltration structures - a structure designed to direct runoff into the ground (e.g., french drains, seepage pits, seepage trench). Inlet - a surface connection to a closed drain. A structure at the diversion end of a conduit. The upstream end of any structure through which water may flow. Land development - (1) the improvement of one lot or two or more contiguous lots, tracts, or parcels of land for any purpose involving (a) a group of two or more buildings, or (b) the division or allocation of land or space between or among two or more existing or prospective occupants by means of, or for the purpose of streets, common areas, leaseholds, condominiums, building groups, or other features; (2) any subdivision of land; (3) development in accordance with 503(1.1) of the Pennsylvania Borough Planning Code, 53 P.S (1.1).. Land/earth disturbance - any activity involving removing, grading, tilling, digging, or filling of ground or stripping of vegetation or any other activity that causes an alteration to the natural condition of the land. Final Draft 23-8

9 Stormwater Management Main stem (main channel) - any stream segment or other runoff conveyance facility used as a reach in the stream. Manning equation (Manning formula) - a method for calculation of velocity of flow (e.g., feet per second) and flow rate (e.g., cubic feet per second) in open channels based upon channel shape, roughness, depth of flow and slope. Open channels may include closed conduits so long as the flow is not under pressure. Municipality - Borough of Carroll Valley, Adams County, Pennsylvania. Nonpoint source pollution - pollution that enters a water body from diffuse origins in the watershed and does not result from discernible, confined, or discrete conveyances or origin. NRCS - Natural Resource Conservation Service (previously SCS). Open channel - a drainage element in which stormwater flows with an open surface. Open - channels include, but shall not be limited to, natural and man-made drainage ways, swales, streams, ditches, canals, and pipes flowing partly full (for computational purposes). Outfall - point where water flows from a conduit, stream, or drain. Outlet - points of water disposal from a stream, river, lake, tidewater or artificial drain. Overland flow - stormwater runoff that flows as sheet or diffused flow and is not concentrated in a channel. Parking lot storage - the use of impervious parking areas for temporary impoundment of stormwater with controlled release rates during rainstorms. Peak discharge - the maximum rate of stormwater runoff from a specific storm event. Penn State Runoff Model - a computer-based hydrologic modeling technique. Pipe - a culvert, closed conduit, or similar structure (including appurtenances) that conveys stormwater. Planning Commission - the Planning Commission of the Borough of Carroll Valley. PMF - Probable Maximum Flood - the flood that may be expected from the most severe combination of critical meteorological and hydrologic conditions that are reasonably possible in any area. The PMF is derived from the probable maximum precipitation (PMP) as determined on the basis of data obtained from the National Oceanographic and Atmospheric Administration (NOAA). Rational formula - a rainfall-runoff relation used to estimate peak flow. Regulated activities - actions or proposed actions that have an impact on stormwater runoff and that are specified in of this Chapter. Retention basin - an impoundment in which stormwater is stored and not released during the storm event. Stored water may be released from the basin at some time after the end of the storm. Return period - the average interval, in years, within which a storm event of a given magnitude can be expected to recur. For example, the 25-year return period 23-9 Final Draft

10 Borough of Carroll Valley rainfall would be expected to recur on the average once every 25 years. Riser - a vertical pipe extending from the bottom of a pond that is used to control the discharge rate from the pond for a specified design storm. Rooftop detention - temporary ponding and gradual release of stormwater falling directly onto flat roof surfaces by incorporating controlled-flow roof drains into building designs. Runoff - any part of precipitation that flows over the land surface. Sediment basin - a barrier, dam, retention or detention basin designed to retain rock, sand, gravel, silt, or other material transported by water. Sediment pollution - the placement, discharge or introduction of sediment into the waters of the Commonwealth. Sedimentation - the process by which mineral or organic matter is accumulated or deposited by the movement of water. Seepage pit/seepage trench - an area of excavated earth filled with loose stone or similar coarse material, into which surface water is directed for infiltration into the ground. Sheet/diffused flow - runoff that flows over the ground surface as a thin, even layer, not concentrated in a channel. Soil-cover complex method - a method of runoff computation developed by the NRCS that is based on relating soil type and land use/cover to a runoff parameter called curve number (CN). Soil group, hydrologic - a classification of soils by the Soil Conservation Service into four runoff categories. The groups range from A soils, which are very permeable and produce little runoff, to D soils, which are not very permeable and produce much more runoff. Spillway - a depression in the embankment of a pond or basin that is used to pass peak discharge greater than the maximum design storm controlled by the pond. Storage indication method - a reservoir routing procedure based on solution of the continuity equation (inflow minus outflow equals the change in storage) with outflow defined as a function of storage volume and depth. Storm frequency - the number of times that a given storm event occurs or is exceeded on the average in a stated period of years. See return period. Storm sewer - a system of pipes and/or open channels that convey intercepted runoff and stormwater from other sources, but excludes domestic sewage and industrial wastes. Stormwater - the total amount of precipitation reaching the ground surface. Stormwater management facility - any structure, natural or man-made, that, due to its condition, design, or construction, conveys, stores, or otherwise affects stormwater runoff. Typical stormwater management facilities include, but are not limited to, detention and retention basins, open channels, storm sewers, pipes, and infiltration structures. Stormwater management site plan - the plan prepared by the developer or his representative indicating how stormwater runoff will be managed at the particular Final Draft 23-10

11 Stormwater Management site of interest in accordance with this Chapter. Stream enclosure - a bridge, culvert, or other structure that encloses a regulated water of this Commonwealth. Subdivision - the division or re-division of a lot, tract, or parcel of land by any means into two or more lots, tracts, parcels or other divisions of land including changes in existing lot lines for the purpose, whether immediate or future, of lease, transfer of ownership, or building or lot development: Provided, however, that the subdivision by lease of land for agricultural purposes into parcels of more than 10 acres, not involving any new street or easement of access or any residential dwellings, shall be exempt. Swale - a low-lying stretch of land that gathers or carries surface water runoff. Timber operations - see forest management. Time of concentration (Tc) - the time for surface runoff to travel from the hydraulically most distant point of the watershed to a point of interest within the watershed. This time is the combined total of overland flow time and flow time in pipes or channels, if any. Watercourse - a channel or conveyance of surface water having defined bed and banks, whether natural or artificial, with perennial or intermittent flow. Waters of the Commonwealth - any and all rivers, streams, creeks, rivulets, ditches, watercourses, storm sewers, lakes, dammed water, wetlands, ponds, springs, and all other bodies or channels of conveyance of surface and underground water, or parts thereof, whether natural or artificial, within or on the boundaries of this Commonwealth. Wetland - those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions, including swamps, marshes, bogs, fens, and similar areas. (Ord. 6-03, 7/15/2003, 201) Final Draft

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13 Stormwater Management Part 3 Soli Erosion and Sedimentation Control A. Soil Erosion and Sedimentation Control Measures Required for Land Development Earth Disturbance. Any person conducting or proposing to conduct an earth disturbance activity in the Borough of Carroll Valley shall design implement and maintain BMPs to minimize the potential for accelerated erosion and sedimentation in order to protect, maintain, reclaim and restore water quality and existing and designated uses. The implementation of erosion and sediment control BMP s shall be the first step in any land disturbance and those BMPs shall be maintained in place until permanent stabilization is completed. (Ord. 6-03, 7/15/2003, 300) Submission of Soil Erosion and Sedimentation Control Plan. Prior to any earth disturbance greater than 5,000 square feet or any excavation in conjunction with land development, two copies of the soil erosion and sedimentation control plan approved by the Adams County Conservation District shall be submitted to the Borough of Carroll Valley. Note: An approved Erosion and Sedimentation Control Plan is a requisite part of the drainage plan requirement for stormwater management. (Ord. 6-03, 7/15/2003, 301) Soil Erosion and Sedimentation Control Requirements. 1. All soil erosion and sedimentation control and grading activities shall be performed in accordance with approved plans and in such a manner as not to cause physical damage or personal injury to existing property and/or adjoining property and owners. 2. Measures used to control soil erosion and reduce sedimentation shall as a minimum meet the latest revised standards, specifications and/or regulations of one or more of the following: A. U.S. Department of Agriculture, National Resource Conservation Service Engineering Field Manual. B. Commonwealth of Pennsylvania, Department of Environmental Protection, Soil Erosion and Sedimentation Control Manual. C. Standards and Specifications for Soil Erosion and Sediment Control in Developing Areas, U.S. Department of Agriculture, Soil Conservation Service, College Park, Maryland. 3. Land disturbance activities for all land developments shall be conducted only in compliance with the following principles: A. There shall be no increase in discharge of sediment or other solid materials Final Draft

14 Borough of Carroll Valley from the site as a result of stormwater runoff; and, any increase shall be deemed a violation of this Chapter. B. Erosion and sedimentation control devices, as set forth in the DEP Erosion and Sediment Pollution Control Program Manual, appropriate to the scale of operations, shall be installed in accordance with the approved E&S plan. All perimeter controls shall be installed prior to earth moving operations of any type. The owner/developer shall contact Adams County Conservation District upon installation of control measures. C. Earth moving operations shall be minimized where possible to preserve desirable natural features and topography of the site. D. Stripping of vegetation, re-grading or other pre-development practices shall be done in such a way as to minimize soil erosion. E. All tree removal shall comply with the Carroll Valley Borough Tree Ordinance [Chapter 25, Part 1]. Prior to removal of any trees, owner/developer shall obtain an approved permit and tree removal plan from the Borough's designated representative. F. Land disturbance shall be limited to the actual construction site and an access strip that has been lined with gravel. The amount of disturbed area and the duration of exposure shall be kept to a minimum. Disturbed areas shall be stabilized with vegetation, mulch, erosion control fabric, and the like, as soon as possible after earthmoving procedures have commenced. G. Temporary vegetation and/or mulching shall be used to protect critical areas during development. (Critical areas shall be construed to mean those portions of a site that are extremely vulnerable to soil erosion.) H. The final, permanent, vegetation and structural soil erosion control and drainage measures shall be installed as soon as practical at the development site in accordance with the approved plans. I. Soils and rock or geologic formations with water supply potential shall be protected from contamination by surface water or other sources of water distribution caused by construction activity. (Ord. 6-03, 7/15/2003, 302) Control Requirements for Well Drilling. For well drilling prior to lot development or receipt of a clearing and grading permit, it is imperative that site disturbance be kept to the minimum necessary. Prior to approval of the well permit the Code Enforcement Officer will meet with the owner or his agent at the proposed site to discuss site restraints and develop the most appropriate E&S plan for the well drilling site. In cases where due to terrain and well location greater that 5,000 square feet disturbance Is required to get in to drill the well a formal E&S plan shall be required. In no case shall the E&S requirements be less than measures below: A. Well Drilling Construction Sequence. If the well is to be drilled within the area tributary to the proposed erosion controls and the controls are installed, no additional erosion controls will be required to drill the well. (1) If the well is located outside the area tributary to the proposed erosion Final Draft 23-14

15 Stormwater Management controls or the erosion controls have not yet been installed the following sequence shall apply to all well drilling activities. (2) The contractor shall install super silt fence parallel to the contour, down-slope from the well drilling activities. (3) The contractor shall keep earth disturbances to the minimum required for the drilling equipment. (4) The contractor shall drill the well. (5) The contractor shall remove the super silt fence upon complete stabilization of the well drilling site. The super silt fence may be moved to another location of the site if possible. (6) In situations where the actual well yields exceed anticipated flows by a considerable amount and the E&S measures are inadequate to handle the sediment pollution operations shall be suspended until appropriate controls are put in place. (Ord. 6-03, 7/15/2003, 303) Final Draft

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17 Stormwater Management Preliminary Plan Requirements. If a subdivision or land development plan is being prepared, preliminary plan requirements as set forth in through of Carroll Valley Borough's current Subdivision and Land Development Ordinance [Chapter 22] must be addressed. A. Drafting Standards: (1) The plan shall be drawn at a scale of 1 inch = 20 feet. (2) Plans shall be legible; half tone or screening shall be used as necessary. (3) Bearings shall be in degrees, minutes and seconds and distances shall be in feet and decimal parts thereof. (4) The boundary line of the lot shall be shown as a solid heavy line. B. Additional Information. The plan shall depict, note, or be accompanied by the following information: (1) Name of the subdivision or land development. (2) Name and address of the owner of record and applicant. (3) Name address and seal of the engineer or surveyor who prepared the plan. (4) Zoning requirements, including: (a) Applicable districts, including overlay districts. (b) Allowable and proposed lot area and yard requirements. (c) Allowable and proposed percentage of the lot(s) allowed to be covered by impervious surfaces and buildings. (5) A location map highlighting the location of the parcel in the Borough and identifying abutting properties and adjoining roads within 1,000 feet. The location map shall be drawn at a scale not smaller than 1 inch = 800 feet. (6) North arrow. (7) Date of original drawing and any revisions. (8) Written and graphic scales. Gross and net acreage of lots. (9) Property lines. (10) Contiguous boundaries of all adjoining properties, and names of owners of such properties. (11) Existing streets on or adjacent to the site with existing and future rights-of-way, names and cart way widths. (12) Locations of existing man-made features such as: buildings and their use, driveways, wells, storm drains, sewer lines, septic tanks, and other on-lot sewage disposal features, culverts, bridges, utility easements, utility poles, water lines and mains, fire hydrants and other significant man-made features within 100 feet of the lot (this includes properties across the street). (13) Existing and proposed contours at 5-foot intervals for the lot and within 100 feet of the lot if the slope exceeds 10 percent. For grades of less than 10 percent, 2-foot contour intervals will be used. If the property contains land within the Flood Hazard District (in which case an actual field surveyed Final Draft

18 Borough of Carroll Valley topographical depiction would be required), then the requirements for a major subdivision and/or land development application shall apply and the application shall not be entitled to a review under this Part. (14) Existing natural features including: (a) Streams, ponds and springs. (b) Soil types and descriptions. (c) Tree masses and notable trees, indicating which are to be removed and which are to remain. (d) Wetlands, including the name of the individual or firm who delineated the wetlands. (15) Lot boundaries, lot layout and building setback lines. (16) Lot area. (17) Proposed driveway location(s). (18) Any areas within the Flood Hazard District as depicted on the FEMA map for Carroll Valley Borough. (19) Copies of the title report for the tract. (20) Certification as to the accuracy and details of the plan shall be sealed by a professional engineer or registered surveyor. (Ord. 6-03, 7/15/2003, 304) Final Plan Requirements. If a subdivision or land development plan is being prepared, preliminary plan requirements as set forth in of Carroll Valley Borough's current Subdivision and Land Development Ordinance [Chapter 22] must also be addressed. A. All drafting standards and plan requirements, as set forth in the preliminary plan shall apply to the final plan as well as the following: (1) A grading plan indicating proposed contour and final grades at 5 foot intervals and all proposed improvements to include all channels, swales, berms and other stormwater conveyances and storage facilities. (2) Locations, of proposed buildings, well, septic and all utilities. (3) Location of existing and proposed benchmark, permanent reference monuments and corner markers. (4) When connection to public water and/or public sewer facilities is proposed, assurance of the availability of such services. This assurance shall be in the form of a letter signed by an officer of the company or authority concerned indicating their ability and willingness to make such service available. (5) When the proposed lot involves a gas pipe line, petroleum products transmission line, electric power transmission line, or any other pipe line or cable located thereon, a letter from the owner or authorized agent of such a facility indicating minimum setback distance requirements or a true and correct copy of the easement or grant of record shall be filed. Final Draft 23-18

19 Stormwater Management (6) Location of wells and septic systems on adjoining lots. (7) A planning module for land development shall be prepared and submitted to the Sewage Enforcement Officer as required by, 25 Pa.Code, Chapter 71, of the Pennsylvania Sewage Facilities Act (8) A graphic depiction and list of all easements shall be shown on the plan and, if appearing on record, the book and page numbers. (9) A development narrative that contains at a minimum the following information: (a) Construction requirements. (b) Construction sequence. (c) General construction notes. (d) Erosion control maintenance notes. (e) Seeding and restoration table. (Ord. 6-03, 7/15/2003, 305) Final Draft

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21 Stormwater Management Part 4 Stormwater Management Exemptions. 1. Any regulated activity that meets the following exemption criteria is exempt from the provisions of , Stormwater Peak Discharge Control Requirements, of this Chapter. These criteria shall apply to the total development even if development is to take place in phases. The date of adoption of this Chapter shall be the starting point from which to consider tracts as parent tracts in which future subdivisions and respective impervious area computations shall be cumulatively considered. Exemption shall not relieve the applicant from implementing such measures as are necessary to protect health, safety, and property. This exemption shall not relieve the applicant from meeting the requirements for water quality and groundwater recharge, special requirements for high quality (HQ) and exceptional value (EV) watersheds, and of E, and , respectively. Designated high quality and exceptional value stream zones are listed in Appendix 23-E to this Chapter. STORMWATER MANAGEMENT PLANNING EXEMPTION CRITERIA Impervious Area Exemption Total Parcel Size Exemption (sq. ft.) <0.25 acre 1, to 0.5 acre 1,500 >0.5 to 1.25 acre 4,000 > 1.25 to 2 acres 10,000 > 2 to 5 acres 15,000 > 5 acres 20,000 (Ord. 6-03, 7/15/2003, 401) General Requirements. 1. All regulated activities in the Borough that do not fall under the exemption criteria shown in shall submit a drainage plan consistent with this Chapter to the Borough for review. These criteria shall apply to the total proposed development even if development is to take place in stages. Impervious cover shall include, but not be limited to, any roof, parking or driveway areas and any new streets and sidewalks. Any areas designed to be gravel or crushed stone shall be assumed to be impervious for the purposes of comparison to the waiver criteria. 2. Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with this Chapter. 3. The existing points of concentrated drainage that discharge onto adjacent property shall not be altered without permission of the adjacent property owner(s) and Final Draft

22 Borough of Carroll Valley shall be subject to any applicable discharge criteria specified in this Chapter. 4. Areas of existing diffused drainage discharge shall be subject to any applicable discharge criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas, except as otherwise provided by this Chapter. If diffused flow is proposed to be concentrated and discharged onto adjacent property, the developer must document that adequate downstream conveyance facilities exist to safely transport the concentrated discharge, or otherwise prove that no erosion, sedimentation, flooding or other harm will result from the concentrated discharge. New points of concentrated or diffused drainage onto adjacent property shall not be created without written permission of the adjacent property owner(s) and shall be subject to any applicable discharge criteria specified in this Chapter. Changes (increase or decrease) of diffuse discharge volume onto adjacent property is permitted only with the written permission of the adjacent property owner. 5. Where a development site is traversed by watercourses, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easement shall prohibit excavation, the placing of fill or structures, and any alterations that may adversely affect the flow of stormwater within any portion of the easement. Also, maintenance, including mowing of vegetation within the easement shall be required, except as approved by the appropriate governing authority. 6. When it can be shown that, due to topographic conditions, natural drainage ways on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainage ways. Work within natural drainage ways shall be subject to approval by DEP through the joint permit application process, or, where deemed appropriate by DEP, through the general permit process. 7. Any stormwater management facilities regulated by this Chapter that would be located in or adjacent to waters of the Commonwealth or wetlands shall be subject to approval by DEP, through the joint permit application process, or, where deemed appropriate by DEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the developer or his agent to show that the land in question cannot be classified as wetlands; otherwise approval to work in the area must be obtained from DEP. 8. Any stormwater management facilities regulated by this Chapter that would be located on State highway rights-of-way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT). 9. Roof drains must not be connected to streets, sanitary or storm sewers or roadside ditches to promote overload flow and infiltration/percolation of stormwater where advantages to do so. When it is more advantageous to connect directly to streets or storm sewers, then it shall be permitted on a case-by-case basis by the Borough. 10. Any stormwater management facilities used to meet the standards of this Chapter must have all construction and/or maintenance requirements recorded so as to be discovered in a title search. (Ord. 6-03, 7/15/2003, 402) General Stormwater Management Requirements. The following general standards shall be applied to all development within the Final Draft 23-22

23 Stormwater Management Borough of Carroll Valley to control stormwater runoff: A. All site development in the Borough shall submit a drainage plan consistent with the provisions of this Chapter to the Borough for review and approval. This requirement shall apply to the total proposed development even if the developments are to take place in stages. Impervious cover shall include, but not be limited to, any roof, parking or driveway area and any new street or sidewalk. any area initially designated to be gravel or crushed stone shall be assumed to be impervious. B. To the maximum extent practical accepted best management practices as outlined in the adopted Act 167 Watershed Stormwater Management Plan(s) for the minimization of generating stormwater runoff, avoiding detrimental effects of stormwater runoff and the protection of environment (low impact development techniques) should be used. C. Runoff from the site shall not be concentrated, or increased runoff discharged onto adjacent property without the written consent of the adjacent landowners in the form of a drainage easement. D. All developments that create impervious surface or change the existing topography shall provide capacity for and treatment of the Water Quality Volume and Groundwater Recharge Volume, as described under and E. Special requirements for areas falling within defined exceptional value and high quality sub-watersheds: the temperature and quality of water and streams that have been declared as exceptional value and high quality is to be maintained as defined in 25 Pa.Code, Chapter 93, Water Quality Standards. Temperature sensitive BMP's and stormwater conveyance systems are to be used and designed with storage pool areas and supply outflow channels and should be shaded with trees. This will require modification of berm for permanent ponds and the relaxation of restrictions on planting vegetation within the facilities, provided that capacity for volumes and rate control is maintained at a minimum, the southern half on pond shorelines shall be planted with shade or canopy trees within 10 feet of the pond shoreline. In conjunction with this requirement, the maximum slope allowed on the berm area to be planted is 10 to 1. This will lessen the destabilization of berm soils due to root growth. a long term maintenance schedule and management plan for the thermal control BMP's is to be established and recorded for all development sites. (Ord. 6-03, 7/15/2003, 403) Runoff Capture Volume Requirements (RCv). 1. The post-development runoff capture volume for a site shall equal or exceed the pre-development runoff capture volume for the site. 2. Compliance with the runoff capture volume requirement shall be demonstrated using the following procedure: A. Calculate the pre-development runoff capture volume using the following equation Final Draft

24 Borough of Carroll Valley P = Runoff Capture Volume = Equation 1 CN Where: Q runoff (inches) P = volume of rainfall captured (inches) S = potential maximum retention after runoff begins (inches) CN = predevelopment runoff curve number An example of this calculation is provided in Example 1, located in Appendix 23-A of this Chapter. B. Calculate the post-development runoff volume using the following procedure. Step 1: Determine the Percentage of Each Land Use/Cover Type. In conventional site development, the designer would refer to. Table 2.2a in TR-55 (SCS, 1986) to select the CN that represents the proposed land use of the overall development (i.e., residential, commercial) without checking the overall percentages of impervious area, grass areas, semi-pervious areas, etc. Because the BMPs emphasize minimal site disturbance, reduce impervious surfaces below conventional amounts, and employ semi-pervious pavements, the CNs for these types of land uses/land covers are less than those for the conventional developments reflected in the CNs contained in Table 2.2a in TR-55. Therefore, it is appropriate to analyze the BMP site as discrete units to determine the CN that most accurately reflects actual conditions. Step 2: Calculate the Composite BMP CN. The initial composite CN is calculated using a weighted approach based on individual land covers without considering the disconnectivity of the site impervious surfaces. This is done using the following Equation 2: CN = c CN1A1 + CN2A2 K + CN A A1 + A2 K + A j j j Equation 2 Where: CN c = composite curve number A j = area of each land cover CN j = curve number for each land cover Overlays of SCS hydrologic soil group boundaries onto homogeneous land cover areas are used to develop the BMP CN. What is unique about this BMP custom-made CN technique is the way that this overlaid information is analyzed as small discrete units that represent the true hydrologic conditions, rather than the conventional TR-55 approach, that is based upon representative national averages that do not incorporate BMP techniques. Step 3: Calculate the BMP CN Based on the Connectivity of Site Impervious Area Disconnected impervious areas are impervious areas without any direct connection to a drainage system or other impervious surface. For example, roof drains from houses that are directed onto lawn areas where sheet flow occurs; instead of flowing onto a driveway that is drained into a curb, gutter, and storm sewer system that are Final Draft 23-24

25 Stormwater Management considered to be disconnected. Such direction of runoff from impervious to pervious surfaces increases the opportunity for infiltration. By increasing the ratio of disconnected impervious areas to pervious areas on the site, the CN and calculated resultant runoff can be reduced. When the total impervious area is less than 30 percent of the total area, the percentage of the unconnected impervious areas within the area influences the calculation of the CN. If the total impervious area is equal to or greater than 30 percent, no adjustment to the CN is warranted because the absorptive capacity of the remaining pervious surfaces will not significantly affect runoff (TR-55, SCS, 1986). The following Equation 3 is used to calculate the CN for areas with less than 30 percent impervious area. CN = CN + P imp c p x (98 - CN p ) X (1 = 0.5R) Equation Where: R = ratio of unconnected impervious area to total impervious area CN c = composite CN (adjusted for disconnected impervious areas) CN p = composite pervious CN P imp = percent of impervious site area Example 1 in Appendix 23-A illustrates the use of steps 1 through 3 to calculate the runoff curve number using the BMP development technique outlined above for a hypothetical 1-acre residential lot designed to incorporate BMP techniques. Step 3: Calculate the BMP Cn Based on the Connectivity of Site Impervious Area Once the runoff CN has been calculated, the NRCS (formerly SCS) Runoff Curve Number Method (TR-55, SCS, 1989) can be used to estimate the runoff volume that will occur during the runoff capture design storm using Equation IV-3 and Equation IV-4. The design storm volume is the volume calculated for the site using Equation 1, presented previously). S = 1000 CN - 10 Equation 4 Where: CN = post-development composite runoff curve number calculated as described above Q = (P 0.2S) (P + 0.8S) Equation 5 Where: Q = runoff (inches) P = runoff capture rainfall volume (as calculated in Equation 1, presented previously) S = potential maximum retention after runoff begins (inches) If the runoff volume calculated in this manner is negligible, the runoff capture standard has been met. Otherwise, appropriate additional structural retention storage facilities must be used to provide the additional retention volume required to retain the excess Final Draft