Source: https://ecode360.com/30524591
Timestamp: 2019-04-24 18:31:48+00:00

Document:
§ 445.01 Statement of findings.
§ 445.07 Compatibility with other requirements.
§ 445.09 Design calculations and reports.
§ 445.10 Exemptions for small developments.
§ 445.12 Stormwater plan content.
§ 445.13 Stormwater management performance standards.
§ 445.14 General watershed management standards.
§ 445.16 Construction criteria for stormwater control facilities.
§ 445.17 Maintenance criteria for stormwater control facilities.
§ 445.18 Inspections of stormwater management controls during construction.
§ 445.19 Requirement for erosion and sediment controls.
§ 445.20 Postconstruction stormwater runoff controls for new development and redevelopment, including operations and maintenance of stormwater BMPs.
Stormwater runoff from lands modified by human activities threatens public health and safety by causing decreased infiltration of rainwater and increased runoff flows and velocities, which overtax the carrying capacity of existing streams and storm sewers, and greatly increases the cost to the public to manage stormwater.
Nonstormwater discharges to municipal separate storm sewer systems can contribute to pollution of waters of the commonwealth.
Federal and state regulations require certain municipalities to obtain a permit for stormwater discharges from their separate storm sewer systems under the National Pollutant Discharge Elimination System (NPDES). Permittees are required to enact, implement, and enforce a prohibition of nonstormwater discharges to the permittee's regulated small municipal separate storm sewer systems (MS4s).
To provide for adequate maintenance of all permanent stormwater management facilities in the Township.
Infiltration BMPs should be spread out and shallow as much as practicable.
Stormwater management facilities shall be provided for subdivisions, land developments, and all activities which change the slope of the land or the land cover and shall be designed to ensure that the maximum rate of stormwater runoff from the site shall be no greater after development than is the rate of runoff from the site prior to development, and be subject to release rates within the Flaugherty Run watershed.
This chapter shall repeal all other code provisions or parts thereof, which are contrary to or conflict with the provisions of this chapter to the extent necessary to give this chapter full force and effect.
Should any part of this chapter be declared invalid, such decision shall not affect the validity of any other part, nor the article as a whole.
For the purposes of this chapter, the terms used herein shall have the following definitions. The words "shall" and "must" shall be mandatory, single and plural, and feminine and masculine are equivalent.
A landowner or developer, as defined by this chapter who has filed an application for development, including his/her heirs, successors and assigns.
Best management practice activities, facilities, designs, measures, or procedures used to manage stormwater impacts from regulated activities, to meet state water quality requirements, to promote groundwater recharge, and to otherwise meet the purposes of this chapter. Stormwater BMPs are commonly grouped into one of two broad categories or measures: structural or nonstructural. In this chapter, nonstructural BMPs or measures refer to operational and/or behavior-related practices that attempt to minimize the contact of pollutants with stormwater runoff whereas structural BMPs or measures are those that consist of a physical device or practice that is installed to capture and treat stormwater runoff. Structural BMPs include, but are not limited to, a wide variety of practices and devices, from large-scale retention ponds and constructed wetlands, to small-scale underground treatment systems, infiltration facilities, filter strips, low-impact design, bioretention, wet ponds, permeable paving, grassed swales, riparian or forested buffers, sand filters, detention basins, and manufactured devices. Structural stormwater BMPs are permanent appurtenances to the project site.
A natural stream that conveys water; a man-made ditch or open channel excavated for the flow of water.
The Allegheny County Conservation District (ACCD).
The County of Allegheny, Pennsylvania.
A closed conduit for the free passage of surface drainage under a highway, railroad, canal, or other embankment.
Engineering guidelines specifying construction details and materials, or objectives, results, or limits which must be met by a facility, structure or process in performance of its intended functions.
The magnitude of precipitation from a storm event, measured in probability of occurrence, such as the one-hundred-year storm, and duration, such as twenty-four-hour, and used in designing stormwater management control systems.
The slowing, dampening, or attenuating of runoff entering the natural drainage pattern or storm drainage system by temporarily holding water in areas such as detention basins, reservoirs, rooftops, streets, parking lots, or within the drainage system itself.
A basin designed to retard stormwater runoff by temporarily storing the runoff and releasing it at a predetermined rate. A detention basin is designed to drain completely after a storm; also called a dry basin.
Any landowner, agent of such landowner or tenant with the permission of such landowner who makes or causes to be made a subdivision or land development.
Any activity, construction, alteration, changes in land use or similar action that affects stormwater runoff characteristics.
The rate of flow, specifically fluid flow. A volume of fluid (in this case water) per unit of time flowing in or from a conduit or channel, usually expressed in cubic feet per second.
The interception and conveyance of excess surface water or groundwater from land by artificial or natural means.
The area which contributes runoff to a designated point of a drainage system usually expressed in acres or square miles; also called a catchment area, watershed, or river basin.
A construction or other human activity which disturbs the surface of the land, including, but not limited to: clearing and grubbing; grading; excavations; embankments; road maintenance; building construction; and the moving, depositing, stockpiling, or storing of soil, rock, or earth materials.
A mound of earth or stone constructed above the natural ground surface, and in stormwater management, with the specific purpose of detaining or diverting stormwater runoff.
The professional engineer duly appointed as the engineer for the Township.
The wearing away of the land surface by running water, wind, ice, or other geologic agents, including such process as gravitational creep.
The entire area drained by Flaugherty Run as delineated by the Pennsylvania Department of Environmental Protection in the Flaugherty Run Watershed stormwater management plan.
The plan for managing stormwater runoff throughout the Flaugherty Run Watershed adopted by Allegheny County as required by the Pennsylvania Stormwater Management Act.
A normally dry land area adjacent to stream channels that is susceptible to being inundated by overbank stream flows. For regulatory purposes, the Pennsylvania Flood Plain Management Act (Act of October 4, 1978, P.L. 851, No. 166) and regulations pursuant to the Act define the floodplain as the area inundated by the one-hundred-year flood and delineated on a map by FEMA (Federal Emergency Management Agency) or by the applicant in accordance with Township Code requirements.
Replenishment of groundwater by infiltration, naturally by precipitation or runoff or artificially by spreading or injection.
The branch of science concerned with the mechanics of fluids, especially liquids. As applied in stormwater management, the study of the characteristics of water flowing in conveyance channels, and from control facilities.
The science dealing with waters of the earth and their distribution and circulation through the atmosphere.
Material which resists the entrance or passing through of water or other liquids.
A surface that prevents the infiltration of water into the ground. Impervious surface includes, but is not limited to, any roof, parking or driveway areas, and any new streets and sidewalks. Any surface areas designed to initially be gravel or crushed stone shall be assumed to be impervious surfaces.
The flow or movement of water through the interstices or pores of a soil or other porous medium, or the absorption of liquid by the soil.
The improvement of one lot or two or more contiguous lots, tracts or parcels of land for any purpose involving a group of two or more residential or nonresidential buildings, whether proposed initially or cumulatively, or a single nonresidential building on a lot or lots regardless of the number of occupants or tenure, or 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, or a subdivision of land.
Any activity involving grading, tilling, digging, or filling or stripping of vegetation; or any other activity which causes land to be exposed to erosion. This includes the disturbance of site stone base below pavement materials.
The upkeep necessary for efficient operation of physical properties.
The National Resources Conservation Service (formerly the Soil Conservation Service), U.S. Department of Agriculture.
The point or location at which stormwater leaves a site, which may include streams, storm sewers, swales or other well-defined natural or artificial drainage features, as well as areas of dispersed overland flow.
A structure designed to control the rate of stormwater runoff released from a detention system.
The maximum rate of flow of water at a given point and time resulting from a specified storm event.
A standard which establishes an end result or outcome which is to be achieved, but does not prescribe specific means for achieving it.
A surface which permits the passage or entrance of water or other liquid.
A point of hydraulic concern such as a bridge, culvert, or channel section, for which the rate of runoff is computed or measured.
The specific area of land where any regulated activities in the municipality are planned, conducted, or maintained.
Any person licensed by the Pennsylvania Department of State or otherwise qualified by law to perform the work required by this chapter.
The instantaneous rate of water flow is usually expressed in cubic feet per second.
Any earth disturbance activities or any activities that involve the alteration or development of land in a manner that may affect stormwater runoff.
Earth disturbance activity of one acre or more. This includes earth disturbance on any portion of, part, or during any stage of, a larger common plan of development. This only includes road maintenance activities where pavement stone base is disturbed.
The percentage of predevelopment peak rate of runoff from a watershed subbasin (as delineated in the watershed plan), which defines the allowable postdevelopment peak discharge from any development site in that subbasin.
A basin, usually enclosed by artificial dikes, that is used to retard stormwater runoff by temporarily storing the runoff for an extended period of time and releasing it at a predetermined rate. These are "wet ponds."
The part of precipitation which flows over the land.
The hydrologic, geologic, and land cover characteristics of any watershed which affect the rate, amount, and direction of stormwater runoff. These may include but are not limited to: vegetation, soils, slopes, and man-made landscape alterations.
The Soil Conservation Service, U.S. Department of Agriculture.
Solid material, both mineral and organic, that is in suspension, is being transported, or has been moved from its site or origin by air, water, gravity, or ice and has come to rest on the earth's surface.
Any subdivision or land development which results (or will result when fully constructed) in the creation of 5,000 or fewer square feet of impervious surface area.
A method of runoff computation developed by the SCS and utilized in its publication, "Urban Hydrology for Small Watersheds," Technical Release No. 55, SCS, June 1986 (or the most current edition).
A sewer that carries intercepted surface runoff, street water and other drainage, but excluding domestic sewage and domestic wastes.
Natural or engineered structures which collect and transport stormwater through or from a drainage area to the point of final outlet, including but not limited to, any of the following: conduits and appurtenant features, canals, channels, ditches, streams, culverts, streets, and pumping stations.
The plan for managing stormwater runoff from a specific development site within the watershed.
The plan prepared by the developer or his representative indicating how stormwater runoff will be managed at the development site in accordance with this chapter. "Stormwater management site plan" will be designated as "SWM site plan" throughout this chapter.
Water generated in a drainage basin resulting from snow melt or precipitation events.
The quantity of water resulting from a storm event, usually expressed in cubic feet, acre feet, or inches over acreage of the watershed.
A watercourse, whether relatively permanent or nonrelatively permanent.
A portion of the watershed that has similar hydrologic characteristics and drains to a common point.
A low-lying trench which gathers or carries surface water runoff.
The time period necessary from surface runoff to reach the outlet of a subarea from, hydraulically, the most remote point in the tributary drainage area.
Any channel for conveyance of surface water having a defined bed and banks, whether natural or artificial, with perennial or intermittent flow.
The entire area drained by a river stream, or other body of water whether natural or man-made.
Any and all rivers, streams, creeks, rivulets, impoundments, ditches, watercourses, storm sewers, lakes, dammed water, wetlands, ponds, springs, and all other bodies or channels of conveyance of surface and undergroundwater, or parts thereof, whether natural or artificial, within or on the boundaries of this Commonwealth.
Stormwater runoff and design calculations shall be submitted to the Township Engineer for review and to the Board of Commissioners for approval with the application for preliminary and/or final approval of a subdivision, land development, or any other activity that requires stormwater management. Plans, profiles, cross sections, reports and/or specifications showing complete construction details shall be submitted with the application for final approval.
The stormwater runoff and design calculations, plans and reports shall be prepared, signed, and sealed by a Pennsylvania-registered engineer with qualifications and experience in preparing stormwater management plans.
Additional analysis, calculations and design criteria may be required for both on-site and off-site stormwater systems where it has been determined by the Township Engineer that further study is necessary.
Upon request by the Township Engineer, stormwater runoff calculations shall be provided for: the outlet and inlet sides of all stormwater drainage and storage facilities and structures; at points in a public street with a change of grade; or where water from a proposed structure, facility or vehicular way is to enter an existing public street, existing storm sewer, existing drainage ditch or existing stormwater storage facility.
Any development which results (or will result when fully constructed) in the creation of 5,000 square feet or less of impervious surface area.
Any agricultural or silviculture activities conducted according to the requirements of 25 Pa. Code 102.
A small development shall be exempt from the preparation of a stormwater management plan as required by Section 445 of this chapter. However, such developments shall provide safe management of stormwater in accordance with the performance standards of this chapter and as approved by the Township.
Applications for small developments shall include a plan which describes, narratively and graphically, the type and location of proposed on-site stormwater management techniques or the proposed connection to an existing storm sewer system. Depending upon actual site conditions, the number of lots proposed and similar considerations, the Township shall determine if the plan must be prepared by a registered professional engineer.
The Township Engineer shall review and the Township shall approve the proposed provisions for stormwater management for small developments. Where the applicant is proposing to connect to an existing storm sewer, the applicant's engineer shall determine that sufficient capacity exists in the storm sewer from the point of connection to the point of outlet in the natural drainage system. The Township shall also determine if the proposed development site is part of a larger parcel or tract which was subject to any specific stormwater management controls contained in a prior plan.
For a parcel or tract of land held in single ownership, only one application for a small development, as defined above, shall be permitted before requiring a stormwater management plan for the entire parcel. A project cannot be phased to circumvent the stormwater requirements by using the exemption for small developments.
In conjunction with meeting the requirements of this chapter, the applicant shall refer to and meet all conditions and requirements set forth in the Township of Crescent's Municipal Separate Storm Sewer System (MS4) Prohibited Discharge Ordinance.
Editor's Note: See Ch. 447, Storm Sewers Operation and Maintenance.
In conjunction with meeting the requirements of the ordinance, the applicant shall refer to and meet all conditions and requirements set forth in the Township of Crescent's Total Maximum Daily Load (TMDL) Plan as adopted and revised.
General description of accelerated runoff control plan.
General description of erosion and sedimentation control plan.
Expected project time schedule, including anticipated start and completion dates.
Hydraulic and hydrologic calculations, methodology and bases of design. Computation of hydraulic and energy grade lines shall be included.
A key map showing the development site's location within the designated watershed and watershed subsheds (consult watershed stormwater plans for boundaries). On all site drawings, show the boundaries of the watershed(s) and subarea(s) as they are located on the development site and identify the watershed names and/or subshed numbers.
Location of the one-hundred-year floodplain on the development site based on the Crescent Township Flood Insurance Study Maps or a determination by the applicant's engineer.
An overlay showing soil types and boundaries within the development site.
The streets, storm sewers and other storm drains to be built, the basis of their design, the outfall and outlet locations and elevations, the receiving stream or channel and its high water elevation and the functioning of the drains during high water conditions.
The parts of the proposed parking area pavements, if any, which are planned to be depressed to provide stormwater storage or conveyance. A maximum of six inches depth of water may be ponded in a proposed parking area, provided it is documented that such ponding does not affect the health, safety, or welfare of those persons using the property.
Existing streams and watercourses to be maintained and new channels to be constructed, their locations, cross sections and profiles.
Proposed culverts and bridges to be built, if any, their materials, elevations, waterway openings and basis of design.
Existing detention ponds and basins to be maintained, enlarged or otherwise altered and new ponds or basins to be built and the basis of their design.
The approximate location and percentage of the total land area in the development which will be covered by impervious surfaces after construction is completed.
The slope, type and size of all proposed and existing storm sewers and other waterways.
Existing contours at intervals of two feet must be provided, including elevations, watercourses, trees and other significant natural features.
All existing buildings, sewers, waterlines and other significant man-made features.
All natural features, including bodies of water (natural and artificial), watercourses (permanent and intermittent), swales, wetlands and other natural drainagecourses on the development site and those off site which will be affected by runoff from the development.
Approximate depth, shape, size and storage of any proposed retention facility.
One or more typical cross sections of all existing and proposed channels or other open drainage facilities, showing the elevation of the existing land and the proposed changes thereto, together with the high water elevations expected from the one-hundred-year storm under the controlled conditions called for by this chapter and the relationship of structures, streets and other utilities.
A site plan showing the property lines, dimensions of the site, and location of existing and proposed structures, sewers, waterlines, easements and rights-of-way.
Certification of the registered professional engineer responsible for preparation of the plan.
A list of the permits and approvals relative to stormwater management that will be required from other governmental agencies and anticipated dates of submission and receipt. Copies of the applications must be submitted to the Township.
Techniques described in Appendix C (Low-Impact Development) of this chapter are encouraged, because they reduce the costs of complying with the requirements of this chapter and the state water quality requirements.
All calculations, assumptions and criteria used in the design of the storm sewer system, detention facilities and sediment and erosion control operations. Hydraulic and energy grade lines shall be provided for both the existing and proposed storm sewers to evaluate the storm system.
All plans and profiles of proposed storm sewers and open channels, including horizontal and vertical controls, elevations, sizes, slopes and materials. All drainage facilities shall be designed to contain the energy grade line for the peak flow rate for the design storm within the structures and pipes. Swales and channels shall provide at least one foot of freeboard above the energy grade line.
Locations, dimensions and design details required for the construction of all facilities.
For all detention basins, a plot or tabulation of storage volumes with corresponding water surface elevations and basin outflow rates for those water surface elevations.
For all detention basins, design hydrographs of inflow and outflow for the peak design flows from the site under natural and developed conditions.
A description of operation for all detention basins.
Contours of the finished project site at intervals of two feet.
The staging of earthmoving activities and program of operation, including a schedule for the installation of all temporary and permanent stormwater control measures and devices.
All information relative to the design and operation of emergency spillways.
Emergency routing of outfall for stormwater runoff in the event of failure of off-site drainage structures.
When major control facilities, such as retention basins, requiring a PA DEP permit, are planned, soil structures and characteristics shall be investigated. Plans and data prepared by a licensed professional engineer with experience and education in soil mechanics shall be submitted. These submissions should consider and offer design solutions for frost heave potential, shrink/swell potential, soil bearing strength, water infiltration, soil settling characteristics, fill and backfilling procedures and soil treatment techniques as required to protect the improvements or structures.
All erosion and sedimentation control measures, temporary, as well as permanent, in sufficient detail to clearly indicate the effectiveness of the plan.
Project specifications relative to stormwater control, erosion and sedimentation.
Evidence that all on-site and off-site easements required to convey runoff flow to an existing public drainage facility or a permanent stream have been granted to the operating entity.
Provide the information to conform with the requirements noted in §§ 445.11, 445.12, 445.13 and 445.14.
Provide a list of adjacent property owners within 200 feet of the subject property and documentation that the adjacent property owners have been notified of the proposed project.
Maintenance plan. A maintenance plan establishing ownership and maintenance responsibilities for all stormwater control facilities (identifying the specific person or entity responsible) and detailing financial requirements and sources of funding shall be submitted with the final plan. Any legal agreements or covenants required to implement the maintenance program shall be submitted. A maintenance schedule shall be submitted in accordance with the Standardized Maintenance Schedule in Appendix B.
One or more of these districts may be further divided into subareas which have similar hydrological characteristics and drain to a common point.
The location and boundaries of the stormwater management districts and subareas are adopted as overlay districts to the Township Zoning Map and are shown on the Zoning Map and the watershed maps which are available in the Township office.
To manage the quantity, velocity and direction of resulting stormwater runoff in a manner which otherwise adequately protects health and property from possible injury.
The stormwater management plan for the development site must consider all the stormwater runoff flowing over the site.
No discharge of toxic materials into any stormwater management system will be permitted.
Watershed standards for the Flaugherty Run Watershed District. The stormwater performance standards contained in this section are intended to implement the standards and criteria contained in the Flaugherty Run Watershed Stormwater Management Plan, adopted and approved as required by the Pennsylvania Storm Water Management Act. If there is any discrepancy between the provisions of this chapter and the standards and criteria of the plan, or if the watershed plan is subsequently amended, then the standard criteria of the current watershed plan shall govern.
In the case of a development in which the total of the building and paved surfaces on the site exceed 5,000 square feet, the developer shall provide as part of the design a stormwater management narrative signed and sealed by an engineer licensed in the Commonwealth of Pennsylvania. The stormwater management narrative shall include an analysis of both pre- and postdeveloped runoff conditions.
For the analysis of redevelopment projects, 20% of the existing impervious surface shall be considered meadow in good condition.
Postdevelopment runoff rates after development shall not exceed the predeveloped runoff rates including the reduction in impervious surface required for redevelopment projects.
The stormwater management plan for any development site with the municipality shall consider all the stormwater runoff flowing over the site, including runoff from upland and off-site areas.
Where the existing storm sewers are reasonably accessible, proposed developments may be required to connect with the storm sewer system unless insufficient capacity or other reasons can be demonstrated to prevent the connection.
Stormwater management detention/retention facilities within a development shall be designed to handle the peak rate of runoff from one-year, two-year, five-year, ten-year, twenty-five-year, fifty-year, and one-hundred-year frequency storm events. Whenever the provisions of federal or state law impose a greater design storm frequency, as for example, where drainage systems cross highways, the stricter standards shall prevail.
All stormwater retention/detention facilities shall be designed with emergency overflow facilities for the one-hundred-year, twenty-four-hour duration storm. Stormwater detention facilities shall drain within 24 to 72 hours from the end of the storm event.
The stormwater volume required for all stormwater retention/detention facilities shall be that volume necessary to handle runoff of a one-hundred-year storm in any development, less that volume discharged during the same storm period used to calculate the volume of rainfall, at the approved release rate.
The stormwater management plan shall consider all of the stormwater runoff flowing over the project site. Runoff calculations shall be made to ensure that runoff from the fully developed upstream watershed area (based on the Township's Comprehensive Land Use Plan) can be accommodated by the pipes, drainage easements and watercourses, etc., on the site.
Joint development of control systems. Stormwater control systems may be planned and constructed in coordination with two or more developments, provided they are in compliance with the applicable provisions of this chapter.
TR-55 Soil Conservation Service Technical Release No. 55.
TR-20 Soil Conservation Service Technical Release No. 20.
Virginia Tech/Penn State Runoff Model.
Perform calculations in the design of any detention/retention facilities used in controlling runoff.
These methods of runoff computation developed and used by the Soil Conservation Service and other authorities are hereby adopted by the Township.
The use of the Basic Rational Method in estimating runoff may be employed in the design of the storm sewer system within the development. The storm sewer system shall be interpreted as the conduits, culverts, inlets and appurtenant features for the conveying of stormwater to, through or from a development site to the point of final discharge or control facility. The Rational Method shall not be used in the analysis of stormwater runoff from the development in its entirety or in conjunction with the design of any retention/detention facilities or other runoff control measures.
Release of detained stormwater. The approved peak release rate of stormwater from all retention/detention facilities for any storm event shall be that which is experienced prior to development for the same storm event up to and including the one-hundred-year storm. Therefore, all retention/detention facilities shall provide staged release of the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year storms.
Design of stormwater management facilities outlined in the plan requires that runoff calculations be made for the site and areas which contribute drainage to the site. These calculations should be based on land use, time of concentration and other standard aspects of hydraulic analysis.
Temporary control measures/facilities. Runoff calculations of the site's condition during development will be used to size temporary control measures.
Permanent control measures/facilities. Permanent control measures/facilities shall be designed to assure that the maximum rate of stormwater runoff is no greater after development than prior to development activities, utilizing the one-hundred-year storm as a basis for calculations. Storm sewer systems may be designed for the twenty-five-year storm provided that the runoff will naturally drain to the detention facility, otherwise the storm sewer system must be designed for the one-hundred-year storm event. Runoff calculations must be made to ensure that runoff from the upstream watershed area can be accommodated by the pipes, drainage easements, watercourses, etc., on the site as well as those downstream of the site to a point of permanent stream discharge. Where downstream facilities are not adequate to convey flow, reduced release rates shall be considered to ensure no detrimental impact to the downstream facilities shall occur as a result of the development.
Computation of hydraulic and energy grade lines. Velocities of flow, slopes, capacity and roughness coefficient of conduits and grassed waterways.
Capacity of sediment basins and permanent holding ponds.
All drainage facilities shall be designed to contain the energy grade line for the peak flow rate for the design storm within the structures a minimum of two feet below surface elevation. The hydraulic grade must be within the pipe. Swales and channels shall provide at least one foot of freeboard. Backwater effects of pipes discharging under surcharge conditions shall be included.
Application. All subdivisions and land development activities which result in an increase in the postdevelopment peak rate of stormwater runoff from any outfall on the development site shall be subject to release-rate percentage for the watershed subarea in which the site (or outfall) is located. A listing of the release-rate percentage for each subarea in the Flaugherty Run Watershed appears in Appendix A of this chapter, and the subareas are delineated on the watershed subarea map in the watershed plan.
Definition. The release-rate percentage defines the percentage of the predevelopment peak rate of runoff that can be discharged from an outfall on the site after development. It applies uniformly to all land developments or alterations within a subarea, and the postdevelopment rate of runoff discharging from each outfall of the development site cannot exceed the release-rate percentage for the subarea in which it is located.
Identify from the watershed subarea map the specific subarea in which the development site is located and obtain the subarea release-rate percentage from Appendix A.
Compute the pre- and postdevelopment runoff hydrographs for each stormwater outfall for the site, using the soil cover complex method (SCS TR-55), for the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year design storms, applying no on-site detention for stormwater management, but including any techniques to minimize impervious surfaces and/or increase the time of concentration for stormwater runoff flowing over the development site. If the postdevelopment peak runoff rate is less than or equal to the predevelopment peak runoff rate, then additional stormwater control shall not be required at that outfall. If the postdevelopment peak runoff rate is greater than the predevelopment value, then stormwater detention will be required and proceed to Subsection H1c(3) below.
Multiply the subarea release-rate percentage by the predevelopment rate of runoff from the development site to determine the maximum allowable release rate from any detention facility for the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year design storm events.
An applicant may seek to extend the otherwise applicable subarea release-rate percentage by performing the no-harm evaluation, which requires an independent engineering analysis to demonstrate that other reasonable options exist to protect downstream areas from harmful storm runoff impacts.
The no-harm evaluation shall be prepared by a registered engineer who is experienced in hydrology and hydraulics, in accordance with the procedure contained in Appendix B of this chapter.
The analysis for the no-harm evaluation shall be submitted to the Township for review by the Township Engineer and approval of the Township.
Retention facilities shall be constructed for all single-family lot developments or single-family lots located in land developments which for certain reasons cannot utilize the development's retention systems. Retention facilities shall consist of gravel-filled sumps, ponds, tanks or other approved facilities, sized in accordance with standard details in the Township Construction Standards. Storage volumes for roof areas greater than 5,000 square feet shall be calculated using the methods outlined in § 445.14D.
All stormwater retention facilities shall be located at least 10 feet from foundation walls in a location approved by the Township. All pipe from roof drains to a point 10 feet from the structure shall be a minimum Schedule 40 PVC pipe or approved equal.
Easements for stormwater management facilities shall be required to have a minimum width of 20 feet. Where a subdivision or land development is, or will be, traversed by a watercourse, there shall be provided a stormwater or drainage easement of a width sufficient for the purpose, but not less than 20 feet. The stormwater detention facilities must be provided within a drainage easement. An access easement must be provided from the public right-of-way to the stormwater detention facility with a minimum width of 20 feet.
All existing and proposed easements and rights-of-way for drainage and/or access to stormwater control facilities shall be shown and the proposed owner identified. Show any areas subject to special deed restrictions relative to or affecting stormwater management on the development site.
Stormwater management easements are required for all areas used for off-site stormwater control, unless a waiver is granted by the municipality.
Stormwater management easements shall be provided by the property owner if necessary for: 1) access for inspections and maintenance; or 2) preservation of stormwater runoff conveyance, infiltration, and detention areas and other BMPs, by persons other than the property owner. The purpose of the easement shall be specified in any agreement under Section 405.
Operation and management plans for stormwater management approved pursuant to 25 Pa. Code 102 after the date of this chapter shall be recorded as a restrictive deed covenant that runs with the land.
If a conservation easement is provided, the long-term ownership, access, maintenance, and use restrictions must be identified on the recording plan.
Flood-prone areas. Land identified as flood-prone on maps issued by the Federal Insurance Administration shall be subject to the regulations of the National Flood Insurance Program and shall comply with the provisions of the Township Zoning Ordinance governing floodplains.
If detention facilities are utilized for the development site, the facility shall be designed such that the postdevelopment peak runoff rates from the development site are controlled to those rates defined by the subarea release-rate percentage or no-harm evaluation for the two-, five-, ten-, twenty-five-, and one-hundred-year design storms; except, however, where downstream flooding problems exist, the Township may impose additional reduced release rate criteria.
All detention facilities shall be equipped with multistage outlet structures to provide discharge control for the two-, five-, ten-, twenty-five-, and one-hundred-year storm frequencies. Provisions shall also be made for safely passing the postdevelopment one-hundred-year storm runoff flows without damaging (i.e., impairing the continued function of) the facilities.
Shared-storage facilities, which provide detention of runoff for more than one development site, may be considered within a single subarea. Such facilities shall meet the design criteria contained in this section. In addition, runoff from the development sites involved shall be conveyed to the facility in a manner so as to avoid adverse impacts, such as flooding or erosion, to channels and properties located between the development site and the shared-storage facility.
Where detention facilities will be utilized, multiple-use facilities, such as lakes, ball fields or similar recreation uses, are encouraged wherever feasible.
Inflow and outflow structures shall be designed and installed to prevent erosion, and bottoms of impoundment-type structures should be protected from soil erosion.
Control and removal of debris, both in the storage structure and in all inlet or outlet devices, shall be a design consideration.
Inflow and outflow structures, pumping stations and other structures shall be protected and designed to minimize safety hazards.
The water depth of a storage pond shall be limited to that which is safe for children. Otherwise, appropriately landscaped fencing at least four feet in height shall be required.
Side slopes of storage ponds shall not exceed a ratio of 3:1 horizontal to vertical dimension.
Landscaping shall be provided for the facility which harmonizes with the surrounding area.
All stormwater detention facilities shall be screened from view of existing roads or streets located within the Township, which is a minimum of six feet in height with sufficient access for maintenance vehicles. The screening material must be approved by the Township. Landscaping of the pond embankment shall not be permitted at any time.
The facility shall be located to facilitate maintenance, considering the frequency and type of equipment that will be required.
The facility shall be equipped with an access road at least eight feet wide and with a maximum of grade of 15%.
All pond outlet structures shall have suitable gaskets to prevent leakage and piping of water through the pond embankment. All storm pipe installed through the pond embankment must be constructed of reinforced concrete pipe.
A geotechnical investigation report for the construction of the stormwater detention/retention and infiltration facilities must be provided including design recommendation for embankment construction, interior and exterior slopes, drainage swales and infiltration areas.
Stormwater culverts, bridges and similar structures serving public streets, access driveways or other vehicular rights-of-way shall be designed to support HS-20 loading and any other imposed loadings necessary without structurally damaging the drainage system. Stormwater culverts, bridges or other structures which do not serve vehicular traffic shall be designed to support the necessary loading without structurally damaging the pipe or affecting its capacity for drainage. Said design shall be approved by the Township Engineer and shall comply with the following requirements.
Conduit size of culverts and other enclosed components of a stormwater drainage system shall be based on computed hydrologic and hydraulic data and computations shall be approved by the Township. The minimum size of any enclosed structure to be maintained by the Township shall be 15 inches in diameter. The minimum size of any enclosed structure to be privately maintained shall be 15 inches in diameter, unless the design calculations, approved by the Township, justify a lesser size. In no case shall larger pipes/culverts be connected to smaller pipes/culverts.
The design of any enclosed drainagecourse shall provide a minimum cleaning velocity of three feet per second. When the design provides for a maximum velocity greater than 10 feet per second, the enclosed components shall be lined or protected to prevent scour.
The design of headwall and endwall structures for enclosed stormwater facilities shall be approved by the Township and shall be in accordance with the Township construction standards.
Energy dissipaters shall be required at the outlet side of all enclosed culverts or similar components and shall be designed in accordance with the Township construction standards.
The type of materials used for enclosed culverts and similar components shall comply with the Township construction standards. No stormwater facility shall be enclosed or covered over until the Township has field reviewed the construction.
All workmanship and materials shall conform to the Township construction standards. In addition, all workmanship and materials shall conform to the latest edition of Penn DOT Form 408 and be supplied by manufacturers or suppliers listed in Penn DOT's Bulletin 15.
All connections to existing storm sewer pipes shall be made by construction of a suitable junction box (inlet or manhole) to provide access for cleanout. No blind connections shall be permitted.
All pond outlet structure pipes shall have suitable gaskets to prevent leakage and piping of water through the pond embankment.
All pipe outlets shall discharge onto a stone rip-rap blanket to prevent erosion of soil. Rip-rap will be sized considering pipe exit velocities.
Controls shall be installed at initial stages of earthmoving and otherwise as outlined in the staging of earthmoving activities section of the erosion and sedimentation control plan.
The discharge of stormwater runoff shall be to a well-defined drainagecourse which has a defined bed and bank. If stormwater runoff cannot be discharged to a defined drainagecourse, documentation of written permission from each downstream property owner shall be provided for all properties between the source of discharge and the defined drainagecourse.
All stormwater detention facilities shall be screened from view of existing roads or streets located within the Township which is a minimum of six feet in height with sufficient access for maintenance vehicles. The screening materials must be approved by the Township. Landscaping of the pond embankment shall not be permitted.
Provide a geotechnical report for the construction of all stormwater facilities including the following: stormwater detention basins and the embankment; drainage swales; and infiltration areas.
Removal of silt from all debris basins, traps or other structures or measures when 40% of capacity is filled with silt.
Disposal of collected silt in a manner which will not adversely affect the environment.
Periodic maintenance of temporary control facilities such as replacement of straw bale dikes, straw filters or similar measures.
Establishment or re-establishment of vegetation by seeding and mulching or sodding of scoured areas where vegetation has not been successfully established. A developer or landowner retains this obligation as to property he or she has developed or improved even if the proper season for "seeding" occurs initially sometime after the project is otherwise completed in whole or as to a particular phase.
Installation of necessary controls sufficient to protect against problems caused by storm events within design frequencies.
Removal of all temporary measures upon completion of the project.
Mowing to maintain adequate stands of grass and to control weeds. Chemical weed control may be used if state and Township regulations are met. Selection of seed mixtures shall reflect the type of maintenance desired by the Township.
Removal of silt from all permanent structures which trap silt or sediment to keep this material from building up in grassed waterways and other permanent structures, thereby reducing their capacity.
Removal of trees and shrubs from pond embankments.
Repair of animal burrows and removal of animals causing same.
It shall be the responsibility of the developer to inspect all permanent facilities to see that corrective action is taken where necessary.
Stormwater facilities located on private property shall be maintained by the landowner or his agent; however, this does not relieve the landowner or his agent of the obligation to inspect his/her own facilities. The Township reserves the right to enter upon private property to make periodic reasonable inspections and to require the landowner to take necessary corrective actions. An easement shall be recorded granting access over private property to the stormwater facilities.
The owner shall convey to the Township easements and/or rights-of-way to assure access for periodic inspections by the Township and maintenance if required.
The owner shall keep on file with the Township the name, address and telephone number of the person or company responsible for maintenance activities; in the event of a change, new information will be submitted to the Township within 10 days of the change.
The owner shall establish any special maintenance funds or other financing sources, in accordance with the approved maintenance plan.
The owner shall pay the amount due to the Special Stormwater Facility Maintenance Fund.
If the storage facility is to be privately owned and maintained, the deposit shall cover the cost of periodic inspections performed by the Township for a period of 10 years, as estimated by the Township. After that period of time, inspections will be performed by the Township and billed directly to the owner.
If the storage facility is to be owned and maintained by the Township, the deposit shall cover the estimated annual costs for maintenance and inspections for 10 years, as estimated by the Township.
The amount of the deposit to the maintenance fund covering annual inspection and maintenance costs shall be converted to present worth of the annual series values. The Township Manager shall determine the present-worth equivalents, which shall be subject to the final approval of the Township Supervisors.
If the storage facility is proposed, which also serves as a recreation facility, such as a lake or ball field, the Township may reduce or waive the amount of the maintenance fund based on the value of the land for public recreation purposes.
If at some future time any storage facility (whether publicly or privately owned) is eliminated due to the installation of storm sewers or another storage facility (i.e., a distributed storage facility), the unused portion of the maintenance fund will be applied to the cost of abandoning the facility and connecting to the storm sewer system or other facility. Any amount of the deposit remaining after the costs of abandonment are paid will be returned to the depositor.
If the owner fails to maintain the stormwater control facilities, following due notice by the Township to correct the problems, the Township shall perform the necessary maintenance or corrective work. The owner shall reimburse the Township for all costs.
Additional items may be included in the maintenance agreement where determined necessary to guarantee the satisfactory maintenance of all facilities. The maintenance agreement shall be subject to the review and approval of the Township's Solicitor.
Prior to issuance of an occupancy permit or utilization of the proposed improvements the applicant must provide the Township a copy of a recorded postconstructed stormwater management plan and the proof of recording for any project containing stormwater management facilities including storm sewers and BMPs.
The owner shall provide a plan in digital format, on state plain coordinates, identifying the location of all stormwater management BMPs.
At the completion of the preliminary site preparation, including stripping of vegetation, stockpiling of topsoil and construction of temporary stormwater management and erosion control facilities.
At the completion of rough grading, but prior to placing topsoil, permanent drainage or other site development improvement and ground covers.
During construction of the permanent stormwater facilities at such times as specified by the Township.
Completion of permanent stormwater management facilities, including established ground covers and plantings.
Completion of any final grading, vegetative control measures or other site restoration work done in accordance with the approved plan and permit.
No work shall commence on any subsequent phase until the preceding one has been field reviewed by the Township Engineer and approved by the Township in writing. If there are deficiencies in any phase, the Township shall issue a written description of the required corrections and stipulate the time by which the corrections must be made.
If during construction the contractor or permittee identifies any site conditions, such as subsurface soil conditions or alterations in surface or subsurface drainage, which could affect the feasibility of the approved stormwater facilities, said person must notify the Township within 24 hours of the discovery of such condition and request a field review by the Township. The Township shall determine if the condition requires a stormwater plan modification.
In cases where stormwater facilities are to be installed in areas of landslide-prone soils or where other special site conditions exist, the Township may require special precautions, such as soil tests and core borings, full-time resident project representative services and/or similar measures. All costs of any such measures shall be borne by the permittee.
No regulated earth disturbance activities within the Township shall commence until approval by the Township of an erosion and sediment control plan for construction activities.
The Pennsylvania Department of Environmental Protection (DEP) has regulations that require an erosion and sediment control plan for any earth disturbance activity of 5,000 square feet or more, under 25 Pa. Code § 102.4(b).
In addition, under 25 Pa. Code Chapter 92,a DEP "NPDES Construction Activities" permit is required for any earth disturbance one acre of more with a point source discharge to surface waters or the Township's storm sewer system, or five acres or more regardless of the planned runoff (hereinafter collectively referred to as "regulated earth disturbance activities"). This includes earth disturbance on any portion of, part of, or during any stage of, a larger common plan of development.
Editor's Note: Chapter 92 of Title 25 of the Pennsylvania Code was reserved 10-8-2010, effective 10-9-2010. It was replaced by Chapter 92a, National Pollutant Discharge Elimination System (NPDES) Permitting, Monitoring and Compliance.
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or Allegheny County Conservation District must be provided to the Township. The issuance of an NPDES construction, permit [or permit coverage under the statewide General Permit (PAG-2)] satisfies the requirements Subsection A.
No regulated earth disturbance activities within the Township shall commence until approval by the Township of a plan which demonstrates compliance with state water quality requirements after construction is complete.
The BMPs must be designed to protect and maintain existing uses (e.g., drinking water use; cold water fishery use) and maintain the level of water quality necessary to protect those uses in all streams, and to protect and maintain water quality in "special protection" streams, as required by statewide regulations at 25 Pa. Code Chapter 93 (collectively referred to herein as "state water quality requirements").
Stream bank and streambed protection: management of volume and rate of postconstruction stormwater discharges to prevent physical degradation of receiving waters (e.g., from scouring and erosion).
DEP has regulations that require municipalities to ensure design, implementation and maintenance of best management practices ("BMPs") that control runoff from new development and redevelopment (hereinafter "development") after regulated earth disturbance activities are complete. These requirements include the need to implement postconstruction stormwater BMPs with assurance of long-term operations and maintenance of those BMPs.
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or Allegheny County Conservation District must be provided to the Township. The issuance of an NPDES construction permit [or permit coverage under the statewide General Permit (PAG-2)] satisfies the requirements Subsection A.
Failure to comply within the time specified shall also subject such person to the penalty provisions of this chapter. All such penalties shall be deemed cumulative and shall not prevent the Township from pursuing any and all other remedies available in law or equity.
DEP or its designees (e.g., County Conservation Districts) normally ensure compliance with any permits issued, including those for stormwater management. In addition to DEP compliance programs, the municipality or its designee may inspect all phases of the construction, operations, maintenance and any other implementation of stormwater BMPs.
During any stage of the regulated earth disturbance activities, if the municipality or its designee determines that any BMPs are not being implemented in accordance with this chapter, the municipality may suspend or revoke any existing permits or other approvals until the deficiencies are corrected.
BMP owners and operators shall allow persons working on behalf of the municipality ready access to all parts of the premises for the purposes of determining compliance with this chapter.
Persons working on behalf of the municipality shall have the right to temporarily locate on any BMP in the municipality such devices as are necessary to conduct monitoring and/or sampling of the discharges from such BMP.
Unreasonable delays in allowing the municipality access to a BMP is a violation of this chapter.
Any person violating the provisions of this chapter shall be guilty of a misdemeanor, and upon conviction shall be subject to a fine of not more than $1,000 for each violation, recoverable with costs, or imprisonment of not more than 30 days, or both. Each day that the violation continues shall be a separate offense.
In addition, the Township, through its Solicitor, may institute injunctive, mandamus or any other appropriate action or proceeding at law or in equity for the enforcement of this chapter. Any court of competent jurisdiction shall have the right to issue restraining orders, temporary or permanent injunctions, mandamus or other appropriate forms of remedy or relief.
Upon notice provided by the municipality under Subsection C, the discharger will have a reasonable time, as determined by the municipality, to cease the discharge consistent with the degree of pollution caused by the discharge.
If a development consists of structures or lots which are to be separately owned and in which streets, sewers and other public improvements are to be dedicated to the Township, stormwater control facilities should also be dedicated to and maintained by the Township.
If a development site is to be maintained in single ownership or if sewers and other public improvements are to be privately owned and maintained, then the ownership and maintenance of stormwater control facilities should be the responsibility of the owner or private management entity.
The Township Council shall make the final determination on the continuing maintenance responsibilities as part of the final application review based on the recommendation of the Planning Commission. The Council reserves the right to accept or reject the ownership and operating responsibility of any or all of the stormwater management controls.
No person shall modify, remove, fill, landscape or alter any existing stormwater BMP, unless it is part of an approved maintenance program, without the written approval of the municipality.
No person shall place any structure, fill, landscaping or vegetation into a stormwater BMP or within a drainage easement, which would limit or alter the functioning of the BMP, without the written approval of the municipality.

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