Township of North Coventry, PA Article III Stormwater Management (SWM) Standards and Site Plan Requirements

§ 194-301 Goals and purpose.

A. Goals. The goals for stormwater management in North Coventry Township are:

(1) To protect the health, safety, and general welfare of the Township residents by protecting the surface water and groundwaters of the Township through effective stormwater management and control of sedimentation and erosion, as provided in this chapter.

(2) To limit the negative impacts of development that occur with inadequately managed stormwater. These negative impacts include but are not limited to altered hydrology, lowering of the groundwater table, physical stream impacts, and biological impacts to nonpoint source pollutants.

B. Purpose. The purpose of stormwater management in North Coventry Township is:

(1) To maintain the predevelopment water balance in watershed and subwatersheds containing first-order and other especially sensitive streams in the Township, and to work to restore natural hydrologic regimes wherever possible throughout the stream system;

(2) To maintain the predevelopment volume of groundwater recharge;

(3) To prevent increase in surface runoff volumes, predevelopment to post-development, thereby mitigating flooding downstream in the watershed, enlarging floodplains, eroding stream banks, and creating other flood-related health, welfare, property losses, and to work to reduce runoff volumes to natural levels;

(4) To maintain predevelopment peak rates of discharge, site-by-site, so as not to worsen flooding adjacent to downstream sites, and to work to restore peak runoff rates to natural levels;

(5) To minimize nonpoint source pollutant loading to groundwaters and surface waters generally throughout North Coventry Township;

(6) To minimize impacts on stream temperatures;

(7) To minimize aesthetic impacts; and

(8) To manage stormwater through approaches and practices that rely on natural process to the greatest extent possible and require a minimum of structures.

§ 194-302 General requirements.

A. Applicants proposing regulated activity in the municipality which are not exempt under § 194-106 shall submit a stormwater management site plan (SWM site plan) to the municipality for review and approval in accordance with Articles III and IV. SWM site plans approved by the municipality shall be on site throughout the duration of the regulated activity.

B. The stormwater management and runoff control criteria and standards in this chapter shall apply to the total proposed regulated activity, even if it is to take place in stages. The measurement of impervious surfaces shall include all of the impervious surfaces in the total proposed regulated activity even if the development is to take place in stages.

C. No regulated activity within the municipality shall commence until:

(1) The municipality issues approval of a SWM site plan, which demonstrates compliance with the requirements of this chapter; and

(2) The applicant has received a letter of adequacy or approval for the erosion and sediment control plan review by the municipality and the Conservation District (if required), and has received all other local, state and federal permit approvals required for the project involving the regulated activity.

D. Neither submission of a SWM site plan under the provisions herein nor compliance with the provisions of this chapter shall relieve any person from responsibility for damage to any person or property otherwise imposed by law.

E. The applicant shall design the site to minimize disturbances to land, site hydrology, and natural resources, and to maintain the natural hydrologic regime, drainage patterns and flow conditions. The applicant shall apply the procedures set forth in § 194-304C and Appendix B[1] for the overall site design and for selection, location and design of features and BMPs to be used to comply with the requirements of this chapter.

[1] Editor's Note: Appendix B is included as an attachment to this chapter.

F. To the maximum extent practicable, post-construction stormwater shall be discharged within the drainage area of the same stream or water body receiving the runoff prior to construction of the proposed regulated activity.

G. Existing drainage peak rate discharges up to and including the 100-year storm and the volume of runoff up to and including the two-year storm onto or through adjacent property(ies) or downgradient property(ies), including diffuse drainage discharge, shall not be altered in any manner by regulated activity under this chapter without written permission from, and, where applicable as determined by the municipality, an easement and agreement with, the affected landowner(s) for conveyance of discharges onto or through their property(ies). Altered stormwater discharges shall be subject to any applicable discharge criteria specified in this chapter.

H. Areas located outside of the site (i.e., areas outside of the regulated activity) that drain through a proposed site are not subject to water quality and volume control, infiltration, stream channel protection, or peak flow rate control requirements as presented in this article. Drainage facilities located on the site shall be designed to safely convey flows from outside of the site through the site.

I. If site conditions preclude capture of runoff from limited portions of the disturbed area for achieving water quality volume control standards, stream channel protection standards, and the two-year storm event peak runoff rate reduction standards for new development required by this chapter, the applicant shall propose alternate methods to mitigate the bypass of the BMPs, subject to the approval of the Municipal Engineer. In no case shall resulting peak rate be greater than the predevelopment peak rate for the equivalent design storm.

J. For all regulated activity, erosion and sediment control BMPs shall be designed, implemented, operated, and maintained during the regulated activity (i.e., during construction) as required to meet the purposes and requirements of this chapter, to meet the erosion and sediment control requirements of the municipality, if applicable, and to meet all requirements under Title 25 of the Pennsylvania Code and the Clean Streams Law.[2]

[2] Editor's Note: See 35 P.S. § 691.1 et seq.

K. For all regulated activity, permanent BMPs and conveyances shall be designed, implemented, operated, and maintained to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code, the Clean Streams Law, and the Storm Water Management Act.[3]

[3] Editor's Note: See 32 P.S. § 680.1 et seq.

L. The design of all BMPs and conveyances shall incorporate sound engineering principles and practices in a manner that does not aggravate existing stormwater problems as identified by the municipality. The municipality reserves the right to disapprove any design that would result in construction in an area affected by existing stormwater problem(s) or continuation of an existing stormwater problem(s).

M. Existing wetlands, either on the site or on an adjacent property, shall not be used to meet the minimum design requirements for stormwater management or stormwater runoff quality treatment. Stormwater discharges to existing wetlands shall not degrade the quality or hydrologic integrity of the wetland.

N. Hotspots runoff controls. Specific structural or pollution prevention practices may be required, as determined to be necessary by the Municipal Engineer, to pretreat runoff from hotspots prior to infiltration. Following is a list of examples of hotspots:

(1) Vehicle salvage yards and recycling facilities;

(2) Vehicle fueling stations;

(3) Vehicle service and maintenance facilities;

(4) Vehicle and equipment cleaning facilities;

(5) Fleet storage areas (bus, truck, etc.);

(6) Industrial sites based on Standard Industrial Classification Codes;

(7) Marine/boat service and maintenance areas;

(8) Outdoor liquid container storage;

(9) Outdoor loading/unloading facilities;

(10) Public works storage areas;

(11) Facilities that generate or store hazardous materials;

(12) Commercial container nursery;

(13) Contaminated sites/brownfields;

(14) Other land uses and activities as designated by the municipality.

O. Contaminated and brownfield sites. Where BMPs may contribute to the migration of contaminants in groundwater, the water quality and runoff volume, stream channel protection, and peak rate control standards shall be met; however, at the Municipal Engineer's discretion, the minimum infiltration requirement may be reduced or eliminated commensurate with the contaminated area and the required water quality and runoff control measures may be increased to mitigate the reduced infiltration requirement for the contaminated area.

P. Additional water quality requirements. The municipality may require additional stormwater control measures for stormwater discharges to special management areas, including, but not limited to:

(1) Water bodies listed as "impaired" by PADEP.

(2) Any water body or watershed with an approved total maximum daily load (TMDL).

(3) Areas of known existing flooding problems.

(4) Critical areas with sensitive resources (e.g., state-designated special protection waters, cold water fisheries, carbonate geology or other groundwater recharge areas that may be highly vulnerable to contamination, drainage areas to water supply reservoirs, etc.).

Q. Applicants shall utilize the Pennsylvania Stormwater Best Management Practices Manual (PA BMP Manual), as amended, or other sources acceptable to the Municipal Engineer, for testing and design standards for BMPs, and where there is a conflict with the provisions of this chapter, the most restrictive applies.

R. When a regulated activity is not part of a subdivision or land development proposal and is less than one acre of earth disturbance, at the discretion of the Township Engineer, reduced provisions may be established from those listed above in order to achieve compliance with the requirements of this chapter.

S. The choice and design of stormwater management systems are to be developed through a procedure that selects and locates best management practices, viewing components in the following priority:

(1) Seeking to control runoff at its source through infiltration;

(2) Improving the quality of the stormwater during conveyance;

(3) Providing for detention.

T. The selection of a competent and creative design engineer by the applicant clearly is critical to the success of an approach that emphasizes the use of best management practices. In order to achieve the standards and construction and maintenance cost reductions which are intended in this chapter, additional time and money is required in the process in preliminary engineering and design. Review and approval of the stormwater management plan will be heavily dependent on the technical review by the Township Engineer and compliance with this chapter.

U. The applicant or applicant's agent shall design, construct and/or install drainage facilities to prevent soil erosion, damage and siltation, and to manage stormwater in order to prevent the impairment of public safety or physical damage due to concentration of the stormwater runoff onto adjacent properties in accordance with this chapter and applicable rules and regulations of the Pennsylvania Department of Environmental Protection, and the Chester County Conservation District. All land areas shall be graded to secure proper drainage away from buildings, on-site sewage disposal systems, and to prevent the uncontrolled collection of stormwater in pools. The system shall be designed to collect and recharge water to the greatest extent possible.

V. The rate of stormwater runoff from any proposed subdivision, land development or regulated activity that is not exempt per § 194-106 shall not exceed the rate of runoff prior to development. Requirements for design of stormwater management systems that incorporate groundwater recharge as an essential element in order to control quantity of discharge is outlined in this chapter. The distribution of drainage discharge from the developed properties shall replicate that of before development conditions to the maximum extent possible. The methodology and facilities used shall be based on the anticipated flows and conditions of each particular site.

W. The stormwater management site plan for each subdivision, land development or regulated activity that is not exempt per § 194-106 shall take into account and provide for the peak rate and volume flows of other areas in the watershed to ensure that cumulative problems are not increased as a result of flows from the proposed project. This analysis shall also explore possibilities to share stormwater management facilities with other areas in the watershed, in which case consultation with the Township shall be required prior to design.

X. Recharge facilities, detention facilities, storm sewers, culverts, bridges and related drainage installation shall be designed and constructed to meet the following purposes:

(1) To permit unimpeded flow of natural watercourses. Such flow may be redirected as required, subject to the approval of the Pennsylvania Department of Environmental Protection;

(2) To ensure adequate drainage of all low points as may be related to streets;

(3) To intercept stormwater runoff along streets at intervals reasonably related to the extent and grade of the area drained to prevent flow of stormwater across intersections during the design storm;

(4) To insure adequate and unimpeded flow of stormwater under driveways in, near, or across natural watercourses or drainage swales. Properly sized pipes or other conduits shall be provided as necessary;

(5) To prevent excessive flow on or across streets, sidewalks, drives, parking areas, and any other paved surface or accessway;

(6) To lead stormwater away from springs.

Y. To this end, the storm drainage system serving the street shall be designed to collect water at any point where three to five cubic feet per second is accumulated, and the bottom of all vertical grades, and immediately upgrade of all street intersections. The system shall discharge any collected water which is not recharged into the nearest practical natural drainage channel or stormwater system.

Z. All natural streams, channels, swales, drainage systems, and/or areas of concentration of surface water shall be maintained in their existing condition, unless alteration is approved by the Township. In any event, all encroachment activities shall comply with Chapter 105 of the Commonwealth of Pennsylvania's Department of Environmental Protection Dam Safety and Waterway Management Rules and Regulations.

AA. Man-made structures shall be kept to a minimum and bridges, culverts, or rip-rap shall be constructed to maintain natural characteristics of the stream and shall meet the approval of the Township.

BB. Streams and intermittent streams are those watercourses depicted on the USGS quadrangle maps of the area, and/or determined as such pursuant to an on-site survey by the Township or their representatives.

CC. Retention/detention basins shall be designed to utilize the natural contours of the land. When such design is impracticable, the construction of the basin design shall utilize slopes as shallow as possible to blend the structures into the existing terrain. The use of multiple retention/detention facilities, which are smaller and less intrusive on the site, is encouraged to meet the requirements of this section.

DD. All areas containing lakes, ponds, wetlands and watercourses shall be considered to be reserved for permanent open space. Any alteration, development, filling, piping, or diverting of such water resources shall be in strict compliance with the provisions of Chapter 370, Zoning, especially those pertaining to the Flood Hazard District, and all prevailing rules and regulations of federal and state agencies. The Township recognizes the use of wetlands as potential components of stormwater management facilities and encourages such innovative use if assurances are met that conservation measures are adequate and that all federal and state requirements are satisfied.

EE. The Township may require that a landowner or development provide reasonable corrective measures to alleviate any existing off-site drainage problem which may be affected by the proposed subdivision, land development or earth disturbance. It shall be the responsibility of the landowner or developer to obtain all drainage easements on, over, or through other properties, and the Township, its agents, workmen, and employees shall be indemnified and held harmless from any liability.

FF. Any water originating from nonnatural sources, such as swimming pools, air-conditioning units, sump pumps, roof drains, or other similar flow, shall be properly discharged into a recharge facility or natural watercourses on the property or connected to an existing or proposed storm drainage system as approved by the Township. Polluting matter from such sources may not be deposited into natural watercourses or storm drains. See also Article IX.

GG. Any water originating from nonnatural sources, as referenced above, shall not be discharged onto any street or other public right-of-way used for pedestrian or vehicular access. See also Article IX.

HH. To mitigate the potential polluting of surface waters and groundwaters by pollutants such as salt, petroleum products, and antifreeze flowing from paved parking lots, pretreatment of the runoff shall be required. The extent of the treatment shall be set by the Township Engineer and will be determined by such factors as the area of the parking lot and the course of the runoff as it is recharged or flows into natural waterways.

§ 194-303 Permit requirements by other governmental entities.

The following activities may require permits or other regulatory approvals. Any necessary permit or approval shall be met prior to final approval by the municipality of the SWM site plan and prior to commencement of any regulated activity, as applicable:

A. All regulated activity subject to permit or regulatory requirements by PADEP under regulations at 25 Pa. Code Chapter 102, or erosion and sediment control requirements of the municipality;

B. Work within a watercourse subject to a permit by PADEP under 25 Pa. Code Chapter 105;

C. Any BMP or conveyance located in or adjacent to surface waters of the commonwealth, including wetlands (PADEP under Title 25 Pa. Code Chapter 105);

D. Any BMP or conveyance located on, or discharging to, or requiring access to or from, a state highway right-of-way (PennDOT under Title 67 highway occupancy permit); and

E. Culverts, bridges, storm sewers, or any other facilities which must pass or convey flows from the tributary area and any facility which may constitute a dam (PADEP under 25 Pa. Code Chapter 105).

§ 194-304 Site design process.

The applicant shall design the site to minimize the disturbances to land, site hydrology, and natural resources, and to maintain the natural hydrologic regime, drainage patterns and flow conditions. The applicant shall demonstrate in its SWM site plan (as required in § 194-313) that the design sequence, objectives and techniques described below were applied to the maximum extent practicable in the site design of the regulated activity while complying with all other requirements of this chapter. The site design shall:

A. First, identify and delineate all existing natural resources and natural and man-made hydrologic features listed in § 194-313C that are located within the site, or receive discharge from, or may be impacted by, the proposed regulated activity.

B. Second, provide a prioritized listing of these resources and features to identify:

(1) Those to be incorporated into the site design in a manner that provides protection from any disturbance or impact from the proposed regulated activity;

(2) Those to be protected from further disturbance or impact but for which the proposed regulated activity will provide improvement to existing conditions;

(3) Those that can be incorporated into and utilized as components of the overall site design in a manner that protects or improves their existing conditions while utilizing their hydrologic function within the limits of their available capacity (e.g., for infiltration, evapotranspiration, or reducing pollutant loads, runoff volume or peak discharge rates, etc.) to reduce the need for or size of constructed BMPs; and

(4) Those that may be considered for alteration, disturbance or removal.

C. Third, develop the site design to achieve the following:

(1) Recognize and incorporate the priorities identified in § 194-304B as the basis for the proposed site layout, grading, construction, and permanent ground cover design;

(2) Minimize earth disturbance (both surface and subsurface);

(3) Maximize protection of or improvement to natural resources and special management areas;

(4) Minimize the disturbance of natural site hydrology, in particular natural drainage features and patterns, discharge points and flow characteristics, natural infiltration patterns and characteristics, and natural channel and floodplain conveyance capacity;

(5) Incorporate natural hydrologic features and functions identified in § 194-304B into the site design to protect and utilize those features and their hydrologic functions to reduce the need for or size of constructed BMPs;

(6) Maximize infiltration and the use of natural site infiltration features, patterns and conditions, and evapotranspiration features;

(7) Apply selective grading design methods to provide final grading patterns or preserve existing topography in order to evenly distribute runoff and minimize concentrated flows;

(8) Minimize the cumulative area to be covered by impervious surfaces and:

(a) Minimize the size of individual impervious surfaces;

(b) Separate large impervious surfaces into smaller components;

(c) Disconnect runoff from one impervious surface to another; and

(d) Utilize porous materials in place of impervious wherever practicable;

(9) Minimize the volume and peak discharge rates of stormwater generated;

(10) Avoid or minimize stormwater runoff pollutant loads and receiving stream channel erosion;

(11) Locate infiltration and other BMPs:

(a) At or as near to the source of generation as possible; and

(b) At depths that are as shallow as possible;

(12) Prioritize the selection and design of BMPs as follows:

(a) Nonstructural and vegetation BMPs; then

(b) Structural (surface and subsurface) BMPs;

(13) For flow volumes requiring conveyance from the source of generation to a BMP for management, give preference to open channel conveyance techniques that provide infiltration and water quality benefits, and landscaped-based management in common open space areas, where practicable; and

(14) Consider additional guidance for incorporating natural hydrology into the site and BMP designs, methods and techniques that support the objectives of § 194-304B and C. Appendix B[1] presents additional discussion of conservation design and low-impact development.

[1] Editor's Note: Appendix B is included as an attachment to this chapter.

D. The procedures set forth above shall be utilized to the maximum extent practicable for the overall site design and selection, location and design of features and BMPs to be used to comply with the requirements of §§ 194-305, 194-306 and 194-308.

§ 194-305 Peak rate controls, water quality and runoff volume requirements.

A. To control post-construction stormwater impacts from regulated activity and meet state water quality requirements, BMPs shall be provided in the site design that replicate predevelopment stormwater infiltration and runoff conditions, such that post-construction stormwater discharges do not degrade the physical, chemical, or biological characteristics of the receiving waters. The green infrastructure and low-impact development (LID) practices provided in the PA BMP Manual, as well as the guidance on green infrastructure, LID and conservation design (CD) provided in Appendix B,[1] shall be utilized for all regulated activities wherever possible. The applicant shall comply with the following peak rate, water quality and runoff volume requirements for all regulated activity, including all new development and redevelopment activities:

(1) Standard 1:

(a) The post-construction total runoff volume shall not exceed the predevelopment total runoff volume for all storms equal to or less than the two-year, twenty-four-hour duration precipitation (design storm). The water quality and runoff volume to be managed shall consist of any runoff volume generated by the proposed regulated activity over and above the predevelopment total runoff volume and shall be captured and permanently retained or infiltrated on the site. This infiltration volume shall not be used as part of the storage volume necessary to calculate peak rates of runoff reductions as required in Standard 2 below.

(b) If the Township Engineer determines that such a standard is not achievable on the site (all or in part) based on existing soil, bedrock, water table, or other conditions on the parcel, Standard 3 provisions apply. For preliminary design purposes, this volume can be initially estimated at a depth of 2 1/2 inches per unit area of new impervious surface.

(2) Standard 2: After installation of impervious cover and assuming full compliance with Standard 1, with two exceptions, the peak rate of stormwater discharges from the site for all design storms up to and including a 100-year-frequency rainfall shall not exceed the peak discharges from the site of the same storm before disturbance. Both the five-year and ten-year post-construction design storms shall be reduced to the predevelopment two-year storm rate. Rainfall depths shall be based on NOAA Atlas 14 values, as amended, and are estimated below. Design storms include:

(a) One-year, twenty-four-hour storm, 2.67 inches.

(b) Two-year, twenty-four-hour storm, 3.21 inches.

(c) Five-year, twenty-four-hour storm, 4.03 inches.

(d) Ten-year, twenty-four-hour storm, 4.70 inches.

(e) Twenty-five-year, twenty-four-hour storm, 5.67 inches.

(f) Fifty-year, twenty-four-hour storm, 6.49 inches.

(g) One-hundred-year, twenty-four-hour storm, 7.36 inches.

(3) Standard 3: If the volume standard set forth in Standard 1 cannot be achieved, then the peak rate standards are modified so that post-development peak rate discharges from the site for all storms up to the ten-year storm must be equal to or less than 75% of the respective peak rates for these storms predevelopment.

(4) Standard 4: Under certain conditions, the Township, upon recommendation of the Township Engineer, may impose the following additional restrictions on stormwater discharges:

(a) Peak discharge may be further restricted when it can be shown that a probable risk to downstream structures or unique natural areas exists or that existing severe flooding problems could be further aggravated.

(b) Measures shall be imposed to protect against groundwater or surface water pollution where the type of business activity may result in significant nonpoint source pollution ("hotspots") or the nature of the soils or bedrock underlying a stormwater management structure constitutes substantial risk of contamination, such as might be the case in limestone formations. Special provisions to be followed in these cases will be provided by the Township Engineer.

(c) Where groundwater yields are very low or where a groundwater supply already is heavily used, the Township may require that the entire volume of the two-year-frequency rainfall (3.2 inches in 24 hours) be retained and infiltrated.

(5) Standard 5: Significant loadings of nonpoint source pollutants shall not be discharged into either surface water or groundwater. "Significant" is defined as resulting in an increase greater than 10% of existing background concentrations of all water quality parameters of consequence identified in federal and state criteria for the watershed. In particular, nutrients (nitrate and total phosphorus), metals (cadmium and lead), total petroleum hydrocarbons (PH) and synthetic organic compounds identified by the US Environmental Protection Agency (EPA) as toxic or hazardous substances must be controlled. If the volume and peak rate standards above (Standards 1 and 2) are met, then water quality impacts are assumed to be adequately controlled. If the volume standard (Standard 1) above cannot be achieved, then a water quality impact analysis must be performed, at the direction of the Township Engineer, confirming prevention of any significant increase in nonpoint source pollution, with particular focus on the pollutants discussed above. Both structural and nonstructural (preventive) measures are to be considered for reduction and prevention of nonpoint source pollution.

[1] Editor's Note: Appendix B is included as an attachment to this chapter.

B. Standards during land disturbance. Peak discharges from the site shall comply with the following. For purposes of calculating required detention storage during land disturbance, peak discharges and discharge volumes shall be calculated based upon the runoff coefficients for bare soils during the maximum period and extent of disturbance. Controls shall insure that the difference in volumes and rates of peak discharge before disturbance and during shall not exceed those peak discharges and discharge volumes that existed before development. It should be understood that detention storage during the period of land disturbance and prior to establishment of permanent cover may require additional facilities on a temporary basis. Such measures shall be located so as to preserve the natural soil infiltration capacities of the planned infiltration bed areas.

C. For modeling purposes, the predevelopment ground cover conditions shall be determined using the corresponding ground cover assumptions presented in § 194-307D of this chapter.

D. The design of the stormwater management facility outlet shall provide for protection from clogging and unwanted sedimentation.

E. BMPs that moderate the temperature of stormwater shall be used to protect the temperature of receiving waters.

F. Runoff from the disturbed area shall be treated for water quality prior to entering existing waterways or water bodies. If a stormwater management practice does not provide water quality treatment, then water quality BMPs shall be utilized to provide pretreatment prior to the runoff entering the stormwater management practice.

G. The municipality may require additional water quality and runoff control measures for stormwater discharging to special management areas such as those listed in § 194-302P.

H. When the regulated activity contains or is divided by multiple drainage areas, the water quality and runoff volume shall be separately addressed for each drainage area.

I. Weighted averaging of runoff coefficients shall not be used for manual computations or input data for water quality and runoff volume calculations.

J. Areas located outside of the site (i.e., areas outside of the regulated activity) that drain through a site are not subject to peak rate control requirements water quality controls and runoff volume requirements. Drainage facilities located on the site shall be designed to safety convey flows from outside of the site through the site.

K. Water quality and volume control practices shall be selected and designed to meet the criteria of § 194-304C that apply to water quality and volume control.

L. When designing detention or retention facilities to control peak rates of runoff, storage volume that is required to meet water quality or infiltration volume requirements shall not be included as part of the storage volume designed to control peak rates of runoff. Failure of an infiltration facility, at any point in time, shall not adversely affect necessary peak flow rate alternation.

M. Evapotranspiration may be quantified and credited towards meeting volume requirements according to the PADEP Post Construction Stormwater Management (PCSM) Spreadsheet and Instructions (December 2020) or the most recent guidance from PADEP.

N. Water quality improvement shall be achieved in conjunction with achieving the infiltration requirements of § 194-305. The infiltration volume required under § 194-305 may be included as a component of the water quality volume. If the calculated water quality and runoff volume is greater than the volume infiltrated, then the difference between the two volumes shall be managed for water quality and runoff volume control through other techniques or practices but shall not be discharged from the site.

§ 194-306 Stream channel protection requirements.

For regulated activity involving new development with one or more acres of earth disturbance, the applicant shall comply with the following stream channel protection requirements to minimize stream channel erosion and associated water quality impacts to the receiving waters:

A. The peak flow rate of the post-construction two-year, twenty-four-hour design storm shall be reduced to the predevelopment peak flow rate of the one-year, twenty-four-hour-duration precipitation, using the NRCS Type II distribution.

B. To the maximum extent practicable, and unless otherwise approved by the Municipal Engineer, the post-construction one-year, twenty-four-hour storm flow shall be detained for a minimum of 24 hours and a maximum not to exceed 72 hours from a point in time when the maximum volume of water from the one-year, twenty-four-hour storm is stored in a proposed BMP (i.e., when the maximum water surface elevation is achieved in the facility). Release of water can begin at the start of the storm (i.e., the invert of the orifice is at the invert of the proposed BMP).

C. For modeling purposes, the predevelopment ground cover conditions shall be determined using the corresponding ground cover assumptions presented in § 194-307D of this chapter.

D. The minimum orifice size in the outlet structure to the BMP shall be three inches in diameter unless otherwise approved by the Municipal Engineer, and a trash rack shall be installed to prevent clogging. For sites with small drainage areas contributing to the BMP that do not provide enough runoff volume to allow a twenty-four-hour attenuation with the three-inch orifice, the calculations shall be submitted showing this condition.

E. When the calculated orifice size is below three inches, gravel filters (or other methods) are recommended to discharge low-flow rates subject to the Municipal Engineer's satisfaction. When filters are utilized, maintenance provisions shall be provided to ensure filters meet the design function.

F. All proposed stormwater management facilities shall make use of measures to extend the flow path and increase the travel time of flows in the facility.

G. When a regulated activity contains or is divided by multiple drainage areas, the peak flow rate control shall be separately addressed for each drainage area.

§ 194-307 Calculation methodology.

A. Stormwater runoff from all regulated activity sites with a drainage area of greater than one acre shall be calculated using a generally accepted calculation technique(s) that is based on the NRCS Soil Cover Complex Method. Table 307.1 summarizes acceptable computation methods. The method selected for use shall be based on the individual limitations and suitability of each method for a particular site. The use of the Rational Method to estimate peak discharges for drainage areas greater than one acre shall be permitted only upon approval by the Municipal Engineer. The runoff volume requirements of this chapter shall always be based on the NRCS Soil Cover Complex Method.

Table 307.1 Acceptable Computation Methodologies for SWM Site Plan
Method	Developed By	Applicability
TR-20 (or commercial computer package based on TR-20)	USDA NRCS	Applicable where use of full hydrology computer model is desirable or necessary
TR-55 (or commercial computer package based on TR-55)	USDA NRCS	Applicable for land development plans where limitations described in TR-55 are met
HEC-1/HEC-HMS	US Army Corps of Engineers	Applicable where use of a full hydrologic computer model is desirable or necessary
Rational Method (or commercial computer package based on Rational Method)	Emil Kuichling (1889)	For sites up to one acre or as approved by the municipality
Other methods	Varies	Other computation methodologies approved by the municipality

B. All calculations using the Soil Cover Complex Method shall use the appropriate design rainfall depths for the various return period storms consistent with this chapter. Rainfall depths used shall be obtained from the latest version of the Precipitation-Frequency Atlas of the United States, National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Hydrometeorological Design Studies Center, Silver Spring, Maryland (NOAA Atlas 14) Atlas 14 values consistent with a partial duration series. When stormwater calculations are performed for routing procedures or infiltration, water quality and runoff volume functions, the duration of rainfall shall be 24 hours.

C. All calculations using the Rational Method shall use rainfall intensities consistent with appropriate times-of-concentration (duration) and storm events with rainfall intensities obtained from NOAA Atlas 14 partial duration series estimates, or the latest version of the PennDOT Drainage Manual (PDM Publication 584). Times-of-concentration shall be calculated based on the methodology recommended in the respective model used. Times of concentration for channel and pipe flow shall be computed using Manning's equation.

D. The applicant shall utilize the following ground cover assumptions for all predevelopment water quality and runoff volume, infiltration volume and peak flow rate calculations:

(1) For regulated activity involving new development or redevelopment, the following ground cover assumptions shall be used:

(a) For areas that are woods (as defined in Article II of this chapter), predevelopment calculations shall assume ground cover of "woods in good condition."

(b) For all other areas (including all impervious surfaces), predevelopment calculations shall assume ground cover of "meadow."

E. Runoff curve numbers (CN) for both predevelopment and proposed (post-construction) conditions to be used in the Soil Cover Complex Method shall be obtained from Table C-1 in Appendix C of this chapter.[1] All those areas to be disturbed during construction shall be assumed to be reduced one hydrologic soil group category level during post-development runoff calculations (i.e., HSG B is reduced to HSG C and so forth).

[1] Editor's Note: Appendix C is included as an attachment to this chapter.

F. Runoff coefficients (C) for both predevelopment and proposed (post-construction) conditions for use in the Rational Method shall be obtained from Table C-2 in Appendix C of this chapter. All those areas to be disturbed during construction shall be assumed to be reduced one hydrologic soil group category level during post-development runoff calculations (i.e., HSG B is reduced to HSG C and so forth).

G. Weighted averaging of runoff coefficients shall not be used for manual computations or input data for water quality and runoff volume calculations.

H. Hydraulic computations to determine the capacity of pipes, culverts, and storm sewers shall be consistent with methods and computations contained in the Federal Highway Administration Hydraulic Design Series Number 5 (Publication No. FHWA-NHI-01-020 HDS No. 5, as amended). Hydraulic computations to determine the capacity of open channels shall be consistent with methods and computations contained in the Federal Highway Administration Hydraulic Engineering Circular Number 15 (Publication No. FHWA-NHI-05-114 HEC 15, as amended). Values for Manning's roughness coefficient (n) shall be consistent with Table C-3 in Appendix C of this chapter.

I. Runoff calculations shall include the following assumptions:

(1) Average antecedent moisture conditions (for the Soil Cover Complex Method only, for example, TR-55, TR-20).

(2) A type II distribution storm (for the Soil Cover Complex Method only, for example, TR-55, TR-20).

§ 194-308 Infiltration requirements.

Providing for infiltration consistent with the natural hydrologic regime is required to compensate for the reduction in the recharge that occurs when the ground surface is disturbed or impervious surface is created or expanded. The applicant shall achieve the following infiltration requirements:

A. Infiltration devices shall be selected based on suitability of soils and site conditions. Measures may include porous pavement with underground infiltration beds, vegetated infiltration beds, swales and trenches, or other seepage structures as proposed in the Pennsylvania Stormwater Best Management Practices Manual, as amended, or other sources acceptable to the Municipal Engineer.

B. For regulated activity involving both new development and redevelopment, infiltration shall be designed to accommodate the entire water quality and runoff volume required in § 194-305A(1). Infiltration BMPs should be consistent with the design and infiltration period guidelines included in the PA BMP Manual or other PA DEP design guidance. If the runoff volume required by § 194-305 cannot be infiltrated, then alternative methods consistent with the PA BMP Manual (as amended) or other PA DEP guidance, such as the Managed Release Concept, may be used to manage this volume with approval from the Municipal Engineer.

C. If site conditions preclude capture of runoff from portions of the impervious surfaces, the infiltration volume for the remaining area shall be increased an equivalent amount to offset the loss.

D. When a project contains or is divided by multiple watersheds, the infiltration volume shall be separately addressed for each watershed.

E. Existing impervious surfaces located in areas outside of the site (i.e., outside of the regulated activity) may be excluded from the calculation of the required infiltration volume.

F. A detailed soils evaluation of the site shall be conducted by a qualified professional and at a minimum shall address soil permeability, depth to bedrock, and subgrade stability. The general process for designing the infiltration BMP shall be conducted by a qualified licensed professional and shall be consistent with the PA BMP Manual (as amended) (or other guidance acceptable to the Municipal Engineer) and in general shall:

(1) Analyze hydrologic soil groups as well as natural and man-made features within the site to determine general areas of suitability for infiltration practices. In areas where development on fill material is under consideration, conduct geotechnical investigations of subgrade stability; infiltration may not be ruled out without conducting these tests.

(2) Provide field tests such as double ring infiltrometer or other hydraulic conductivity tests (at the elevation of the proposed infiltration surface) to determine the appropriate hydraulic conductivity rate. Standard septic/sewage percolation tests are not acceptable for design purposes.

(3) Design the infiltration facility for the required retention (infiltration) volume based on field-determined infiltration capacity (and apply safety factor as per applicable design guidelines) at the elevation of the proposed infiltration surface.

(4) On-lot infiltration features are encouraged; however, it shall be demonstrated to the Municipal Engineer that the soils are conducive to infiltration on the identified lots.

G. Infiltration BMPs shall be selected based on suitability of soils and site conditions and shall be constructed on soils that have the following characteristics:

(1) A minimum depth of 24 inches between the bottom of the BMP and the top of the limiting zone.

(2) An infiltration rate sufficient to accept the additional stormwater volume and drain completely as determined by field tests conducted by the applicant.

(3) The infiltration facility shall completely drain the retention (infiltration) volume within three days (72 hours) from the end of the design storm.

H. All infiltration practices shall:

(1) Be selected and designed to meet the criteria of § 194-304C that are applicable to infiltration;

(2) Be set back at least 25 feet from all buildings and features with subgrade elements (e.g., basements, foundation walls, etc.), unless otherwise approved by the Municipal Engineer;

(3) For any infiltration practice that collects runoff from shared or multiple features and that is located within 50 feet of a building or feature with subgrade elements (e.g., basements, foundation walls, etc.), the bottom elevation shall be set below the elevation of the subgrade element.

I. Infiltration facilities shall, to the maximum extent practicable, be located to avoid introducing contaminants to groundwater:

(1) When a hotspot is located in the area draining to a proposed infiltration facility, an evaluation of the potential of groundwater contamination from the proposed infiltration facility shall be performed, including a hydrogeologic investigation (if necessary) by a qualified licensed professional to determine what, if any, pretreatment or additional design considerations are needed to protect groundwater quality.

(2) When located within a wellhead protection area of a public water supply well, infiltration practices shall be in conformance with the applicable approved source water protection assessment or source water protection plan.

(3) The applicant shall provide appropriate safeguards against groundwater contamination for land uses that may cause groundwater contamination should there be a mishap or spill.

J. During site construction, all infiltration practice components shall be protected from compaction due to heavy equipment operation or storage of fill or construction material. Infiltration areas shall also be protected from sedimentation. Areas that are accidentally compacted or graded shall be remediated to restore soil composition and porosity. Adequate documentation to this effect shall be submitted to the Municipal Engineer for review. All areas designated for infiltration shall not receive runoff until the contributory drainage area has achieved final stabilization.

K. Where sediment or debris transport in the stormwater runoff is anticipated to reach the infiltration system, appropriate permanent measures, as determined by the Municipal Engineer, to prevent or collect sediment shall be installed prior to discharge to the infiltration system. Measures may include settlement or filtration devices.

L. Where roof drains are designed to discharge to infiltration practices, they shall have appropriate measures to prevent clogging by unwanted debris (for example, silt, leaves and vegetation). Such measures shall include but are not limited to leaf traps, gutter guards and cleanouts. Whenever possible, roof drains shall discharge to vegetated areas that drain overland to infiltration practices.

M. All underground infiltration practices shall have appropriate positive overflow controls to prevent storage within one foot of the finish surface or grade.

N. No sand, salt or other particulate matter may be applied to a porous surface material for winter ice conditions.

O. The following procedures and materials shall be required during the construction of all subsurface facilities.

(1) Excavation for the infiltration facility shall be performed with equipment which will not compact the bottom of the seepage bed/trench, or like facility.

(2) The bottom of the bed and/or trench shall be scarified prior to the placement of aggregate.

(3) Only clean aggregate, free of fines, shall be allowed.

(4) The top, bottom and sides of all seepage beds, trenches, or like facilities shall be covered with drainage filtration fabric. Fabric shall meet the specifications of PennDOT Publication 408, Section 735, Construction Class 1.

(5) Perforated distribution pipes connected to centralized catch basins and/or manholes with provision for the collection of debris shall be provided in all facilities. The perforated pipes shall distribute stormwater throughout the entire seepage bed/trench, or like facility. All distribution pipes shall be a material which meets the 100-year life expectancy criteria of PennDOT as referenced in § 194-310.

P. All infiltration facilities which service more than one lot and are considered a common facility shall have an easement provided to the Township for future access if necessary.

§ 194-309 Detention/retention facility design requirements.

A. The following setbacks are required for stormwater management facilities:

(1) Stormwater retention or detention basins shall be located at least 50 feet from any structure, whether existing or proposed.

(2) Stormwater retention or detention basins shall be located at least 50 feet from any property boundary or right-of-way.

(3) Stormwater retention or detention basins shall be located at least 50 feet from existing wetlands, or the banks of existing streams.

(4) Recharge systems shall be located at least 25 feet from any basement wall and 25 feet from wastewater treatment areas.

(5) Any recharge system designed to handle runoff from any commercial or industrial impervious parking or outside storage area shall be a minimum of 50 feet from any water supply well or any wastewater treatment area.

B. Riser. A riser or other acceptable outfall shall be provided at the outlet of all detention basins. The riser shall be constructed of precast or poured in place concrete with controlled orifices. A trash rack or similar appurtenance shall be provided to prevent debris from entering the riser. All risers shall have a concrete base attached with a watertight connection. The base shall be of sufficient weight to prevent flotation of the riser.

C. Landscaping. All stormwater control systems, whether existing or proposed, shall be planted to effectively naturalize areas so as to become an integral and harmonious element in the local landscape. No trees shall be planted in the earthfill of berms or dams.

D. Emergency spillway. Whenever possible, the emergency spillway for detention basins shall be constructed on undisturbed ground. Emergency spillways shall be designed according to the NRCS Engineering Field Manual. All emergency spillways shall be constructed so that the detention basin berm is protected against erosion with a permanent erosion control blanket. The minimum capacity of all emergency spillways shall be such that the capacity of the emergency spillway equals the peak flow rate from the 100-year design storm. Emergency spillway linings shall extend along the upstream and downstream berm embankment slopes. The upstream edge of the emergency spillway lining shall extend to a minimum of two feet below the spillway crest elevation. The downstream edge of the spillway lining shall, at minimum, extend to a distance of 10 feet beyond the toe of the berm embankment. The emergency spillway shall not discharge over earthen fill and/or easily erodible material.

E. Anti-seep collars. Anti-seep collars shall be installed around the principal pipe barrel within the normal saturation zone of the detention basin berms. The anti-seep collars and their connections to the pipe barrel shall be watertight. The anti-seep collars shall extend a minimum of two feet beyond the outside of the principal pipe barrel. The maximum spacing between collars shall be 14 times the minimum projection of the collar measured perpendicular to the pipe.

F. Freeboard. Any stormwater basin required or regulated by this chapter designed to store runoff and requiring a berm or earthen embankment shall be designed to provide an emergency spillway to safely convey flow up to and including the 100-year proposed conditions. The height of embankment shall provide a minimum one foot of freeboard above the design flow depth of the emergency spillway. Should any BMP require a dam safety permit under PA Chapter 105 regulations, the facility shall be designed in accordance with and meet the regulations of PA Chapter 105 concerning dam safety. PA Chapter 105 may require the safe conveyance of storms larger than the 100-year event.

G. Slope of detention basin embankment. The maximum slope of earthen detention basin embankments shall meet the requirements contained in this subsection. Whenever possible, the side slopes and basin shape shall be amenable to the natural topography. Straight side slopes and rectangular basins shall be avoided.

H. Width of berm. The minimum top width of detention basin berms shall be 10 feet.

I. Slope of basin bottom. In order to ensure proper drainage of the detention basin, a minimum grade of 2% shall be maintained for all sheet flow. A minimum grade of 1% shall be maintained for all channel flow. The Township Engineer may approve the use of a flat (0%) bottom accompanied with appropriate landscape plantings to promote water quality and groundwater recharge.

J. Energy dissipaters. Energy dissipating devices (rip-rap, end sills, etc.) shall be placed at all basin outlets. Any pipe or other component which discharges directly into the basin shall be equipped with energy dissipating devices and shall outlet into the bottom of the basin.

K. Landscaping and grading of detention basin. All landscaping and grading standards shall be as follows:

(1) Cuts. No excavation shall be made with a cut face steeper than three horizontal to one vertical, except under the condition that the material in which the excavation is made is sufficiently stable to sustain a slope of steeper than three horizontal to one vertical. A written statement to that effect is required from an engineer and must be submitted and approved by the Township Engineer. The statement shall affirm that the site has been inspected and that the deviation from the slope should not result in injury to persons or damage to property. Retaining walls shall be required if a stable slope cannot be maintained. Any retaining wall design must be approved by the Township Engineer. The toe of the slope or headwall of any cut must be located a minimum of five feet from property lines.

(2) Fills. No fills shall be made which create any exposed surfaces steeper in slope than three horizontal to one vertical, except where the fill is located so that settlement, sliding, or erosion will not result in property damage or be a hazard to adjoining property, streets, or buildings. A written statement is required from an engineer certifying that he/she has inspected the site and that any proposed deviation from the slope specified above should not endanger any property or result in property damage, and must be submitted to and approved by the Township Engineer.

(a) A concrete or stone masonry wall designed and constructed in accordance with these specifications and standards may be required to support the face of the fill where the above-specified slopes are exceeded.

(b) The top of any fill or toe of the slope of any fill shall be located 25 feet from any property line with the exception of a downstream property line where the toe of the embankment shall be placed a sufficient distance to allow for energy dissipating devices, but in no case less than 40 feet unless approved otherwise by the Township.

(3) Planting requirements. All areas proposed for recreational use, whether active or passive, shall be planted to effectively naturalize the areas to become an integral and harmonious element in the natural landscape.

(4) Drainage channels and retention areas. All storm drainage channels and retention areas, whether existing or proposed, shall be graded and planted to effectively naturalize areas so as to become an integral and harmonious part of the landscape by contour and type of plant material employed.

(5) Fence or screening. A fence or suitable vegetation screen shall be provided around all detention basins as required by the Township Engineer. All vegetative screening shall be at least 3 1/2 feet in height and shall be composed of the following shrubs: barberry (Barberis species); Eleagnus (Eleagnus species); firethorn (Pyracantha species); or rose (Rose species). All vegetative screening shall provide a barrier to prevent entrance to the detention basin area. The fencing or vegetative screening requirement shall be waived only upon approval by the Township.

L. Easements for all basins and storm pipes not located within the public street right-of-way shall be provided in accordance with § 194-804.

M. Any BMP intended to hold standing water for four days or longer shall be designed to incorporate biologic controls consistent with the West Nile Guidance found in PADEP document 363-0300-001, "Design Criteria - Wetlands Replacement/Monitoring," as amended (or contact the Pennsylvania State Cooperative Wetland Center or the Penn State Cooperative Extension Officer for design information).

N. Conveyance facilities to or existing from stormwater management facilities (i.e., detention basins) shall be designed to convey the design flow to or from the facility.

§ 194-310 Drainage and conveyance system design requirements.

A. Design flow rate. The storm drain system shall be designed to carry a twenty-five-year peak flow rate, and a fifty-year peak flow rate at the sump area. The design twenty-five-year peak flow rate into each inlet shall be indicated on the stormwater management plan. The twenty-five-year flow rate shall be determined by the rational formula, Q = CIA.

Where:
Q	=	Peak runoff rate, cubic feet per second (CFS);
C	=	Runoff coefficient equal to the ratio of the runoff rate to the average rate of rainfall over a time period equal to the time of concentration;
I	=	Average rainfall intensity to inches per hour for a time equivalent to the time of concentration;
A	=	Drainage area in acres.
Approximate values for the runoff coefficient and runoff intensity are found in the Commonwealth of Pennsylvania, Department of Transportation, PennDOT Drainage Manual Publication 584, as amended.

B. Overflow system. An overflow system shall be provided to carry flow to the detention basin when the capacity of the storm drain pipe system is exceeded. The overflow system shall be of sufficient capacity to carry the difference between the 100-year and the twenty-five-year peak flow rates without creating additional damage to any drainage facilities, structures or roadways.

C. Inlet capacity. All inlets must be designed to accommodate the twenty-five-year peak flow rate. The designer must submit capture/bypass calculations for each inlet and include these calculations in the stormwater report. The capacity of each inlet shall be indicated on the stormwater plan. The capacity of all C, M, or S type inlets shall be determined from the following source:

Commonwealth of Pennsylvania

Department of Transportation

Design Manual, Part 2

Highway Design, Chapter 10

D. Summary table. A table shall be provided on the plan summarizing storm sewer information, including inlet numbers, inlet pipes, elevation of all grates and pipe inverts, pipe diameters and lengths, pipe material, etc. A similar table shall be provided summarizing the design information for all temporary and permanent drainage channels.

E. Roadway crossings or structures located within designated floodplain areas shall be able to convey runoff from a 100-year design storm consistent with Federal Emergency Management Agency National Flood Insurance Program - Floodplain Management Requirements.

F. Any facility located within a PennDOT right-of-way shall comply with PennDOT minimum design standards and permit submission and approval requirements.

G. Adequate erosion protection and energy dissipation shall be provided along all open channels and at all points of discharge. Design methods shall be consistent with the Federal Highway Administration Hydraulic Engineering Circular Number 11 (Publication No. FHWA-IP-89-016, as amended) and the PADEP Erosion and Sediment Pollution Control Program Manual (Publication No. 363-2134-008, as amended), or other design guidance acceptable to the Municipal Engineer.

H. Straight pipe selections. Wherever possible, all storm drain pipes shall be designed to follow straight courses. No angular deflections of storm sewer pipe sections in excess of 5° shall be permitted. No vertical curves shall be permitted in the storm drain pipe system.

I. Minimum grade and size. All storm drain pipes shall be designed to maintain a minimum grade of 1/2%. All storm pipes shall have a minimum inside diameter of 15 inches, except that pipes under a twenty-five-foot-deep or greater fill shall not be less than 24 inches, or a cross-sectional area of 453 square inches.

J. Pipe material and thickness. All storm sewers shall be a material which meets the 100-year life expectancy criteria contained in PADOT Design Manual Part 2, Pub. 13M, Chapter 10, August 2009, Change No. 1, as amended.

K. Pipe capacity. The capacity of all pipe culverts shall, at a minimum, provide the required carrying capacity as determined by the following source:

United States Department of Transportation

Federal Highway Administration

Hydraulic Design Series Number 5

Hydraulic Design of Highway Culverts, 3rd Edition

L. Pipe arches. Where headroom is restricted, equivalent pipe arches may be used in lieu of circular pipes.

M. Allowable headwater depth. At all inlets or manholes, the maximum allowable headwater depth shall be one foot below the top of the inlet grate of the manhole cover.

N. Horizontal pipe deflections. A manhole or inlet shall be provided at all horizontal deflections in the storm pipe system exceeding five degrees.

O. Inlet boxes shall conform to PennDOT Standard Drawings and Publication 408, latest edition. Inlets shall be permanently marked with the phrase "No Dumping - Drains to Creek" with medallion or other method approved by the Township Engineer.

P. Minimum and maximum cover. A minimum of 18 inches of cover shall be maintained over all storm drain pipes. The top of storm drain pipes shall be at least 1/2 foot below subgrade elevation.

Q. Diversion or runoff. All storm drain pipes shall be designed to carry the runoff into a detention basin or similar facility utilized to control the rate of runoff. No discharge at the top or side of basin embankments shall be permitted.

R. Culverts and drainage channels.

(1) Design flow standards. All culverts and drainage channels shall be designed to carry a flow rate equal to a fifty-year, twenty-four-hour storm (NRCS, Technical Release No. 55).

(2) Erosion prevention. All drainage channels shall be designed to prevent the erosion of the bed and bank areas. The flow velocity in all vegetated drainage channels shall not exceed three feet per second to prevent erosion unless special provisions are made to protect banks and channel bottoms against erosion. Suitable bank stabilization shall be provided where required to prevent erosion of the drainage channels. Where storm sewers discharge into existing drainage channels at an angle greater than 30° from parallel with the downstream channel flow, the far side bank shall be stabilized by the use of rip-rap or masonry, and/or concrete walls. The stabilization shall be designed to prevent erosion and frost heave under and behind the stabilizing media.

(3) Maximum side slope. Any vegetated drainage channel requiring mowing of the vegetation shall have a maximum grade of three horizontal to one vertical of those areas to be mowed.

(4) Design standard. Because of the critical nature of the vegetated drainage channels, the design of all vegetated channels shall, as a minimum, conform to the design procedures outlines in the PADEP manuals. Several acceptable sources outline procedures for nonvegetated drainage channels, including the following:

Bureau of Public Roads

Hydraulic Engineering Circular No. 5

Hydraulic Charts for the Selection of Highway Culverts

Federal Highway Administration

Hydraulic Engineering Circular No. 13

Hydraulic Design of Improved Inlets for Culverts

(5) Reference to publications and source documents in this section shall be deemed to include any amendments and revisions thereof.

S. Residential subdivisions or development. Drainage channels shall be provided to intercept stormwater along property lines at locations where runoff from a lot would drain onto an adjacent lot. These channels shall be designed to convey stormwater to a suitable discharge point or the storm sewer system.

T. Easements for all drainages and conveyance systems, existing or proposed, not located within the public street right-of-way shall be provided per § 194-804.

§ 194-311 SWM site plan.

For any regulated activity, unless exempt per the provisions of § 194-106:

A. Preparation and implementation of an approved SWM site plan is required.

B. No regulated activity shall commence until the municipality issues written approval of a SWM site plan which demonstrates compliance with the requirements of this chapter and, if required, a letter of adequacy has been issued by the Conservation District for an erosion and sediment control plan.

C. The preliminary or final approval of subdivision and/or land development plans, and the issuance of any building or occupancy permit, shall not proceed until the applicant has received written approval of a SWM site plan from the municipality.

D. The SWM site plan approved by the municipality shall be on site throughout the duration of the regulated activity.

E. The SWM site plan shall consist of a general description of the project including calculations, maps, and plans.

F. A note on the maps shall refer to the associated computations and erosion and sediment control plan by title and date.

G. The cover sheet of the computations and erosion and sediment control plan shall refer to the associated maps by title and date.

H. All SWM site plan materials shall be submitted to the municipality in a format that is clear, concise, legible, neat, and well organized; otherwise, the SWM site plan shall not be accepted for review and shall be returned to the applicant.

I. When a regulated activity is not part of a subdivision or land development proposal and is less than one acre of earth disturbance, at the discretion of the Township Engineer, reduced provisions may be established from those listed below in order to show compliance with the requirements of this chapter.

§ 194-312 Relationship of stormwater management site plan to soil erosion and sediment control plan.

A. The stormwater management site plan should be developed for a site before soil erosion and sediment control measures are considered to ensure that the standards for control of discharge can be established for each point or line of interest.

B. In designing sediment control facilities, consideration should be given to maintaining the distribution and rates of discharge developed for the stormwater management plan at all times during the construction period. Where necessary to maintain this standard, sediment control facilities must be developed upstream of stormwater management facilities.

C. When preparing the sequences of construction, attention shall be given to protecting subsurface stormwater management facilities from sediments. Provisions for clearing sediments from permanent surface stormwater management facilities upon completion of construction shall be included in the construction sequences.

§ 194-313 SWM site plan content.

The stormwater management site plan shall consist of a narrative report, design drawings, calculations, supporting text and documentation. The report shall describe the project and its compliance with the applicable sections of this chapter, and a map or maps describing the topography of the area, proposed alterations, and the location and description of permanent stormwater management measures and facilities. The following elements shall be included in the stormwater management site plan:

A. The written narrative report summary of the project shall include:

(1) General description of the project, including:

(a) Description of how the proposed project complies with all requirements of federal, state, county and Township agencies with regard to stormwater management.

(b) Description of existing and proposed man-made features, including planned temporary and permanent stormwater management and soil erosion control measures on site.

(c) Plans and specifications of the stormwater management and soil erosion measures and facilities.

(2) The overall stormwater management design concept for the project, both during and after construction, and how the site design achieves the requirements of §§ 194-301 through 194-317 of Article III;

(3) Date the project is to begin and expected date final stabilization will be completed;

(4) A suitable map of the total watershed (a USGS quadrangle map is sufficient);

(5) General description of on-site stormwater flows and their effect on neighboring properties;

(6) A table of contents for the stormwater management report and complete design calculations. All report pages shall be numbered and referenced in the table of contents;

(7) Seal and signature of the registered professional responsible for preparation of the plan and report;

(8) Existing features, conditions, natural resources, hydrologic features, and special management areas (as listed in § 194-313C);

(9) How the site design achieves the requirements of § 194-304, and, if applicable, where they could not be achieved and why;

(10) Proposed features and conditions, proposed erosion and sediment control features, proposed BMPs, conveyances, and any other stormwater facilities;

(11) A description of the effect of the project (in terms of flow alteration and runoff volumes, water quality and peak flows, etc.) on existing natural resources, hydrologic features and special management areas, adjacent and downgradient properties, and any existing municipal or other stormwater conveyance system(s), that may be affected by or receive runoff from the regulated activity (whether located within or outside of the area of the regulated activity), and specifics of how erosion, water quality and flow impacts will be avoided or otherwise mitigated;

(12) Proposed nonpoint source pollution controls and justification and confirmation that the proposed project will not result in any increased pollutant loadings to any existing stream or stream impairment identified by PADEP, or to any receiving water body;

(13) Description of construction stages or project phases, if so proposed.

B. Design information. As part of the stormwater management site plan and stormwater design report, complete design calculations and analysis, as well as supplemental information, shall be submitted. The information shall show compliance with applicable federal, state, county and Township standards and regulations. The information shall include, but is not limited to, the following:

(1) Analysis of the percentage of all predevelopment and post-development stormwater that is recharged to groundwater, and all supporting material.

(2) A design drawing of the berm embankment and outlet structure indicating the embankment top elevation, embankment side slopes, top width embankment emergency spillway elevation, perforated riser dimensions, pipe barrel dimensions, and dimensions and spacing of anti-seep collars.

(3) Design computations for the pipe barrel and riser.

(4) A plot of the stage-storage (acre-feet vs. elevations) and all supporting computations.

(5) Flood routing computations for before, during, and after development.

(6) A detailed plan of the trash rack.

(7) Design computations for energy dissipater devices located at pipe outfalls.

(8) Storm sewer and storm inlet design, capacity, efficient and other related calculations.

(9) Design computations for all swales, waterways, channels or diversions.

C. Mapping or plan sheet information. Maps or plan sheets showing the locations of all stormwater management system components shall be submitted. Details must be shown to define each and every proposed component of the stormwater management design. Details shall show dimensions, locations, specifications and other information as required by the Township Engineer to facilitate proper construction. Map(s) or plan sheets of the site shall be submitted on minimum twenty-four-inch-by-thirty-six-inch sheets and shall be prepared in a form that meets the requirements for recording at the Chester County Office of the Recorder of Deeds and the requirements of the operation and maintenance (O&M) plan and O&M agreement (Article VII). If the SALDO has additional or more stringent criteria than this chapter, then the SALDO criteria shall also apply. Unless otherwise approved by the Municipal Engineer, the contents of the maps or plan sheets shall include, but not be limited to:

(1) A listing of all regulatory approvals required for the proposed project and the status of the review and approval process for each. Final approval or adequacy letters must be submitted to the municipality prior to (or as a condition of) the municipality's issuing final approval of the SWM site plan. Proof of application or documentation of required permit(s) or approvals for the programs listed below shall be part of the SWM site plan, if applicable:

(a) NPDES permit for stormwater discharges associated with construction activities;

(b) PADEP permits as needed:

[1] PADEP joint permit application;

[2] Chapter 105 (Dam Safety and Waterway Management);

[3] Chapter 106 (Floodplain Management);

(c) PennDOT highway occupancy permit;

(d) Erosion and sediment control plan letter of adequacy; and

(e) Any other permit under applicable state or federal regulations.

(2) A statement on the plan, signed by the applicant, acknowledging that any revision to the approved SWM site plan shall be submitted to and approved by the municipality, and that a revised erosion and sediment control plan shall be submitted to, and approved by, the Conservation District or municipality (as applicable) for a determination of adequacy prior to construction of the revised features.

(3) The following signature block, on the plan, signed and sealed by the qualified licensed professional responsible for the preparation of the SWM site plan:

"I (name), on this date (date of signature), hereby certify to the best of my knowledge that the SWM site plan meets all design standards and criteria of the North Coventry Township Code of Ordinances, Chapter 194, Grading, Erosion and Sediment Control; Stormwater Management. [Note: Include signature, name, discipline of professional license, and license stamp or seal here.]

(4) The following signature block for the municipality:

"On behalf of the North Coventry Township, (municipal official or designee), on this date [signature date], has reviewed and hereby certifies to the best of my knowledge that the SWM site plan meets all design standards and criteria of the North Coventry Township Code of Ordinances, Chapter 194, Grading, Erosion and Sediment Control; Stormwater Management."

(5) A location map, with a scale of one inch equals 2,000 feet or greater, showing the site location relative to highways, municipal boundaries, or other identifiable landmarks.

(6) The name of the project, tax parcel number(s), and the names, addresses and phone numbers of the owner of the property, the applicant, and firm preparing the plan.

(7) The date of SWM site plan submission and revision dates, as applicable. The signature and seal of the qualified licensed professional(s) responsible for preparation of the maps and plan sheets.

(8) A graphic and written scale of one inch equals no more than 50 feet. The signature and seal of the qualified licensed professional(s) responsible for preparation of the maps and plan sheets.

(9) A North arrow.

(10) Legal property boundaries, including:

(a) The total project property boundary and size with distances marked to the nearest foot and bearings to the nearest degree.

(b) Boundaries, size and description of purpose of all existing easements and deed-restricted areas of the project property, with distances marked to the nearest foot and bearings to the nearest degree.

(11) Existing natural resources and natural or man-made hydrologic features that are located within the site or receiving discharge from, or that may otherwise be impacted by, the proposed regulated activity, including but not limited to:

(a) All existing natural resources, hydrologic features and drainage patterns including natural waterways, water bodies, wetlands, streams (intermittent and perennial), ponds, lakes, vernal pools, etc., natural infiltration areas and patterns, areas of significant natural evapotranspiration, and other water features and aquatic resources.

(b) Any existing man-made drainage features, BMPs, conveyances, facilities, open channels, swales, drainage patterns, or other flood, stormwater or drainage control features.

(c) For the site, discharge points and locations of concentrated flows and their drainage areas.

(d) For named waters, show names and their watershed boundaries within the site.

(e) Special management areas (as per § 194-302P).

(f) For the water bodies, streams and wetlands identified in § 194-313C(11), label or otherwise show the following attributes, if applicable:

[1] The designated use as determined by PADEP (25 Pa. Code Chapter 93);

[2] Impairments listed on the PADEP "Integrated List" (as updated) and the listed source and cause of impairment;

[3] Name, date, and target pollutant(s) for any approved total maximum daily load (TMDL); and

[4] Drainages to water supply reservoirs.

(g) Areas that are part of the Pennsylvania Natural Diversity Inventory (PNDI) and a list of potential impacts and clearances received (for regulated activity involving one acre or more of proposed earth disturbance).

(h) Woods, vegetated riparian buffers and other areas of natural vegetation.

(i) Topography using contours (with elevations based on established bench marks) at intervals of two feet. The datum used and the location and elevation of any bench marks used shall be shown.

(j) Areas classified by the municipality as steep slopes.

(k) Soil names and boundaries, general type of soils with hydrologic soil group noted, and in particular note areas most conducive to infiltration BMPs, such as groups A and B, etc., estimated permeabilities in inches per hour, and location and other results of all soil tests and borings.

(l) If present, areas with underlying carbonate geologic units, existing sinkholes, subsidence or other karst features, and any associated groundwater recharge areas with increased vulnerability to contamination.

(m) Any contaminated surface or subsurface areas of the site.

(n) Water supply wells.

[1] Location of existing well(s) on the project property and delineation of the recharge area(s) (if known), or a fifty-foot-diameter assumed recharge area;

[2] Location of existing well(s) within 50 feet beyond the boundary of the project property boundary (if public water supply is proposed for the regulated activity).

(o) Current FEMA 100-year floodplain boundaries, elevations, and floodway boundaries for any special flood hazard areas on or within 100 feet of the property, as required by the Township Zoning Ordinance.[1]

[1] Editor's Note: See Ch. 370, Zoning.

(p) Boundaries of riparian buffer(s) as required by the Township Zoning Ordinance.

(12) Boundaries of all-natural resources as defined by § 370-29, Natural Resource Conservation Overlay District, of the Township Zoning Ordinance, including but not limited to steep slopes, watercourses/riparian buffers, wetlands, wetland margins, woodlands and specimen trees.

(13) Location of the proposed regulated activity, limits of earth disturbance (disturbed area), and BMPs and conveyances relative to the location of existing natural resources and hydrologic features and special management areas resulting from the site design process of § 194-304.

(14) Description of existing and proposed ground cover and land use including the type and total area.

(15) Existing and proposed man-made features, including roads, paved areas, buildings, and other impervious and pervious surfaces on the project property (or an appropriate portion of the property as determined in consultation with the Municipal Engineer) and within the proposed disturbed area, and including the type and total area of the following:

(a) Existing impervious surfaces (must differentiate existing impervious surfaces installed after April 12, 2014);

(b) Existing impervious surfaces proposed to be replaced;

(c) Existing impervious surfaces to be permanently removed and replaced with pervious ground cover;

(d) New or additional impervious surfaces; and

(e) Percent of the site covered by impervious surfaces for both the existing and proposed post-construction conditions.

(16) The total extent of the upstream area draining through the site.

(17) All BMPs, conveyances and other stormwater management facilities shall be located on the plan sheets, including design drawings, profile drawings, construction details, materials to be used, description of function, etc.

(18) Complete delineation of the flow paths used for calculating the time of concentration for the predevelopment and post-construction conditions shall be included.

(19) The locations of all existing and proposed utilities, sanitary sewers, on-lot wastewater facilities (including subsurface tanks and leach fields), and water supply lines within the site and within 50 feet beyond the proposed limits of earth disturbance.

(20) A grading plan, including all areas of proposed earth disturbance and the proposed regulated activity and delineating the boundary or limits of earth disturbance of the site. The total disturbed area of the site shall be noted in square feet and acres.

(21) Proposed final grade elevations and contours at intervals of two feet.

(22) For each proposed BMP and conveyance included in the SWM site plan (including any to be located on any property other than the property being developed by the applicant), the following shall be included on the SWM site plan map or plan sheets:

(a) Identification of the person responsible for ongoing inspections, operation, repair, and maintenance of the BMP or conveyance after completion of construction.

(b) Delineation of the land area, structures, impervious surfaces, and conveyances draining to and from the BMP or conveyance.

(c) Easements, as per the requirements of Article VIII, that shall include:

[1] Boundaries labeled with distances shown in feet and bearings to the nearest degree;

[2] Notes or other documentation, as needed, to grant the municipality the right of access to all BMPs and conveyances for the purposes of inspection and enforcement of the requirements of this chapter, and any applicable O&M plans and O&M agreements;

[3] Notes or other documentation, as needed, to grant the municipality the right of access to all roadways necessary to access all BMPs and conveyances, where roadways are not to be dedicated to the municipality;

[4] Notes or other documentation as needed to grant the owner of any BMP or conveyance the right of access for the purpose of inspection, operation, maintenance, and repair of the BMP or conveyance that is to be owned, operated and maintained by a person other than the municipality, and other than the owner of the property on which the BMP or conveyance is located;

[5] A minimum twenty-foot perimeter (or other width as determined in consultation with the Municipal Engineer) around all BMPs and conveyances;

[6] Sufficient vehicular ingress to and egress from a public right-of-way or roadway, as determined in consultation with the Municipal Engineer; and

[7] Accompanying notes or other documentation as needed, and in accordance with Article VIII, describing the type, purpose and total area of easements, who the easement is granted to, and the rights, duties and obligations of the parties with respect to every BMP or conveyance.

(d) Boundaries of land areas (if any) for which deed restrictions are required for the purpose of protecting and prohibiting disturbance to a BMP or conveyance, indicating the area to which the restriction applies with distances shown in feet and bearings to the nearest degree, and a written description of the type, purpose and nature of the restriction.

(e) Other items that may be needed to comply with all other requirements of Article VIII.

D. A detailed site evaluation conducted by a qualified licensed professional for projects proposed environmentally sensitive areas, such as contaminated sites and brownfields, as described in § 194-302O of this chapter.

E. Inspections, operation and maintenance requirements. The following documents shall be prepared and submitted to the municipality for review and approval as part of the SWM site plan, in accordance with the requirements of Article VIII, for each BMP and conveyance included in the SWM site plan (including any to be located on any property other than the property being developed by the applicant):

(1) An O&M plan;

(2) An O&M agreement;

(3) Any easement agreements that are needed to ensure access, inspection, maintenance, operation, repair and permanent protection of any permanent BMP(s) and conveyances associated with the regulated activity;

(4) Any written deed, deed amendment or equivalent document (if needed) to be recorded against a subject property, as shown on the SWM site plan maps or plan sheets, or recorded plan sheets for the purpose of protecting and prohibiting disturbance to a BMP or conveyance; and

(5) Written approval, easement agreements, or other documentation for discharges to adjacent or downgradient properties when required to comply with § 194-302G and Article VIII of this chapter.

F. Stormwater runoff design computations and documentation, such as hydrologic, hydraulic, and structural computations, assumptions, BMP loading ratios, etc., consistent with the guidelines and criteria presented in the PA BMP Manual (as amended) or other guidance acceptable to the Municipal Engineer, and used in the design of the BMPs, conveyances and other features proposed to be utilized for stormwater management, or as otherwise necessary to demonstrate that the requirements of this chapter have been met.

G. A highway occupancy permit from the Pennsylvania Department of Transportation (PennDOT) District Office must be submitted to the municipality prior to (or as a condition of) the municipality's final approval of the SWM site plan when utilization of a PennDOT storm drainage system is proposed.

H. An erosion and sediment control plan, where applicable, as prepared for and submitted to the Chester County Conservation District and/or municipality. A letter of adequacy from the Conservation District, if applicable, must be submitted to the municipality prior to (or as a condition of) the municipality's final approval of the SWM site plan.

§ 194-314 SWM site plan submission.

A complete SWM site plan that complies with all applicable provisions of § 194-313 shall be submitted to the municipality for review and approval, as follows:

A. The SWM site plan shall be coordinated with the applicable state and federal permit process and the municipal SALDO review process. All permit approvals or letters of adequacy not yet received by the applicant at the time of submittal of the SWM site plan to the municipality must be submitted to the municipality prior to (or as a condition of) the municipality's final approval of the SWM site plan.

B. For projects that require SALDO approval, the SWM site plan shall be submitted by the applicant as part of the preliminary plan submission where applicable for the regulated activity.

C. For regulated activities that do not require SALDO approval, the SWM site plan shall be submitted by the applicant for review in accordance with instructions from the municipality.

D. The number of copies of the SWM site plan to be submitted by the applicant for review shall be in accordance with instructions from the municipality.

E. The corresponding review fee shall be submitted to the municipality simultaneously with the SWM site plan, per the municipality's fee schedule.

F. Any submissions to the municipality that are found to be incomplete shall not be accepted for review and shall be returned to the applicant within 10 business days of the application date with a notification, in writing, of the specific manner in which the submission is incomplete.

G. Financial security, per the requirements of § 194-112, shall be submitted to the municipality prior to approval of the SWM site plan.

§ 194-315 SWM site plan review.

A. The SWM site plan shall be submitted to the municipality for review by the Municipal Engineer for consistency with this chapter and the respective PA Act 167 stormwater management plan(s). The Municipal Engineer will review the SWM site plan for any subdivision or land development for compliance with this chapter and the municipal SALDO provisions not otherwise superseded by this chapter.

B. If applicable, the applicant shall have received a letter of adequacy from the Conservation District or other PADEP approval for the proposed regulated activity prior to (or as a condition of) final approval by the municipality.

C. The Municipal Engineer will notify the applicant and the municipality, in writing, within 45 calendar days, whether the SWM site plan is consistent with the requirements of this chapter. If the SWM site plan involves a subdivision and land development plan, the notification shall occur within the time period allowed by the MPC (as amended). If a longer notification period is provided by other statute, regulation, or ordinance, the applicant will be so notified by the municipality.

(1) If the Municipal Engineer determines that the SWM site plan is consistent with this chapter, the Municipal Engineer shall forward a letter of consistency to the municipality, who shall then forward a copy to the applicant.

(2) The municipality may approve the SWM site plan with conditions reasonably defined to make the SWM site plan compliant with the terms of this chapter, and, if so, shall provide the conditions for approval in writing.

(3) If the Municipal Engineer determines that the SWM site plan is inconsistent or noncompliant with this chapter, the Municipal Engineer will forward a letter to the municipality, with a copy to the applicant citing the reason(s) and specific chapter sections for the inconsistency or noncompliance. Inconsistency or noncompliance may be due to inadequate information to make a reasonable judgment as to compliance with this chapter. Any SWM site plans that are inconsistent or noncompliant may be revised by the applicant and resubmitted in accordance with § 194-317 when consistent with this chapter. Resubmission will commence a new municipal review and notification time period.

D. The municipality will not grant final approval to any proposed subdivision, land development, or regulated activity specified in this chapter if the SWM site plan has been found to be inconsistent with this chapter.

E. All required permits from PADEP shall be obtained and submitted to the municipality prior to (or as a condition of) final approval of any proposed subdivision, land development, or other regulated activity by the municipality.

F. No building permits for any regulated activity will be approved by the municipality if the SWM site plan has been found to be inconsistent with this chapter, as determined by the Municipal Engineer. All required permits from PADEP shall be obtained prior to issuance of a building permit.

G. The municipality's approval of a SWM site plan shall be valid for a period not to exceed one year commencing on the date that the municipality approved the SWM site plan. If stormwater management facilities included in the approved SWM site plan have not been constructed, or if constructed, as-built plans of these facilities have not been approved within this one-year time period, then the applicant may seek reinstatement of approval of the expired SWM site plan. If the municipality determines that the expired SWM site plan is consistent and compliant with current regulations and requirements, then the expired SWM site plan will be reinstated; otherwise, it will be rejected. The applicant will be prohibited from conducting any regulated activity until a reinstated or newly approved SWM site plan is obtained in accordance with § 194-317 of this chapter.

H. All or portions of the final approved SWM site plan shall be recorded (as "record plans") per the instructions of the municipality.

I. Upon completion of construction, the applicant shall be responsible for completing final as-built plans of all BMPs, conveyances, or other stormwater management facilities included in the approved SWM site plan as per the requirements of § 194-602 of this chapter.

§ 194-316 Revision of SWM site plans.

A. A submitted SWM site plan under review by the municipality shall be revised and resubmitted for any of the following reasons:

(1) A change in stormwater management BMPs, conveyances, facilities or techniques;

(2) Relocation or redesign of stormwater management BMPs, conveyances, or facilities; or

(3) Soil or other site conditions are not as stated on the SWM site plan as determined by the Municipal Engineer, and the new conditions necessitate design changes.

B. The revised SWM site plan shall be resubmitted in accordance with § 194-314 and subject to review as specified in § 194-315 of this chapter.

C. A revision to an approved SWM site plan shall be submitted to the municipality, accompanied by the applicable municipal review fee.

§ 194-317 Resubmission of inconsistent or noncompliant SWM site plans.

Any SWM site plan deemed inconsistent or noncompliant may be revised and resubmitted with the revisions addressing the Municipal Engineer's concerns documented in writing. The submission shall be addressed to the municipality in accordance with § 194-314 of this chapter, distributed accordingly, and be subject to review as specified in § 194-315 of this chapter. The applicable municipal review fee shall accompany a resubmission of a SWM site plan previously determined to be inconsistent or noncompliant.