A. 
Applicants proposing Regulated Activities described in § 123-5E which do not fall under the exemption criteria shown in § 123-5F shall submit a Stormwater Management Plan consistent with § 123-17 to the Township for review.
B. 
The applicant is required to perform an evaluation to find practicable alternatives to the surface discharge of stormwater, the creation of impervious surfaces and the degradation of waters of the Commonwealth, and must maintain as much as possible the natural hydrologic regime.
C. 
Stormwater management shall be conducted in such a way as to minimize accelerated erosion and resulting sediment pollution. Measures to control erosion and resulting sediment pollution shall, at a minimum, meet the standards of Chapter 102 (Erosion and Sediment Pollution Control) of Title 25, Rules and Regulations of the PADEP.
D. 
Stormwater management shall be conducted in such a way as to minimize and mitigate impact upon regulated wetlands. Such areas shall not be altered in any way without obtaining design approval, required certifications and permits from Paradise Township, the United States Army Corps of Engineers and the PADEP. Constructed wetlands shall be designed in accordance with guidelines found in Appendix G of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update.
E. 
Stormwater Management Plans shall be designed so that the construction of basins within the one-hundred-year floodplain shall be avoided, where possible, but where unavoidable, shall be consistent with Chapter 65 (Floodplain Management) of the Paradise Township Code of Ordinances and Rules and regulations of the PADEP.
F. 
Stormwater management shall permit unimpeded flow of natural watercourses except as modified by stormwater detention facilities or open channels consistent with this chapter.
G. 
Stormwater Management Plans shall include financial guaranties for all Stormwater Management Plan controls as specified in § 123-27 through 123-29.
H. 
Stormwater Management Plans shall be prepared by a Design Professional.
I. 
The Stormwater Management Plan must be designed through an evaluation consistent with the sequencing provisions of § 123-9 to ensure maintenance of the natural hydrologic regime, to promote groundwater recharge, and protect groundwater and surface water quality and quantity. The Stormwater Management plan designer must proceed sequentially in accordance with this article.
J. 
The Stormwater Management Plan must be prepared in compliance with the water quality provisions in § 123-10.
K. 
The Stormwater Management Plan must be prepared in compliance with the riparian buffer provisions in Chapter 160 (Zoning).
L. 
The Stormwater Management Plan must be prepared in compliance with the groundwater recharge requirements in § 123-11.
M. 
The Stormwater Management Plan must be prepared in compliance with the standards for managing runoff in § 123-12 for the Brodhead Watershed.
N. 
The Stormwater Management Plan must be prepared using the calculation methodology required by § 123-13.
O. 
The Stormwater Management Plan must be prepared to comply with other requirements in § 123-14.
P. 
The Stormwater Management Plan shall document compliance with the erosion and sedimentation control requirements of § 123-15.
Q. 
All Stormwater Management Plans shall include a consumptive use tracking report as required in § 123-16.
R. 
Any stormwater management facilities regulated by this chapter that would be located on state highway rights-of-way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).
The applicant is required to investigate alternatives to the surface discharge of stormwater and the creation of impervious surfaces and must maintain as much as possible the natural hydrologic regime of the site. All practicable alternatives to the discharge of stormwater are presumed to have less adverse impact on quantity and quality of waters of the Commonwealth unless otherwise demonstrated. The design of all regulated activities shall include the following steps, in sequence, to minimize stormwater impacts:
A. 
Prepare an Existing Resources and Site Analysis Plan as described in § 131-38 of the Paradise Township Subdivision and Land Development Ordinance.
B. 
Clearly indicate buffers in compliance with § 160-21C(7) of the Paradise Township Zoning Code.
C. 
Prepare a draft project layout avoiding earth disturbance in sensitive areas and minimizing total site earth disturbance. The ratio of the disturbed area to the entire site area must be indicated on the plan.
D. 
Identify site specific predevelopment drainage areas, discharge points, recharge areas to be preserved and hydrologic soil groups A and B to be utilized for recharge.
(1) 
Evaluate nonstructural stormwater management alternatives, including strategies to minimize earth disturbance, break large impervious surfaces into smaller, separated areas and minimize total impervious areas.
(2) 
Satisfy water quality requirements in § 123-10 of this chapter.
(3) 
Satisfy groundwater recharge (infiltration) objectives in § 123-11 of this chapter, providing stormwater treatment prior to infiltration.
(4) 
Determine what stormwater management district the site falls into and conduct a predevelopment runoff analysis.
(5) 
Prepare final project design to maintain predevelopment drainage areas and discharge points, minimize earth disturbance and impervious surfaces, and reduce runoff.
(6) 
Conduct a post development runoff analysis based on the final design and document that the release rate(s) for the site stormwater management district(s) has/have been met.
(7) 
Document runoff from the site is managed through treatment prior to discharge, as part of detention, bioretention, direct discharge or other structural control.
E. 
A pre-application meeting with the Township Engineer is an optional but strongly encouraged step to speed the review process. The applicant will be responsible for any/all engineering review fees and charges associated with such pre-application meeting.
A. 
Water quality BMPs shall be designed to detain the proposed conditions two-year, twenty-four-hour design storm to the existing conditions one-year flow using the SCS Type II distribution. Additionally, provisions shall be made (such as adding a small orifice at the bottom of the outlet structure) so that the proposed conditions one-year storm takes a minimum of 24 hours to drain from the facility from a point where the maximum volume of water from the one-year storm is captured (i.e., the maximum water surface elevation is achieved in the facility). Wet basins that meet the requirements in the Pennsylvania Stormwater BMP manual are encouraged. Release of water can begin at the start of the storm (i.e., the invert of the water quality orifice is at the invert of the facility). Orifices smaller than three inches in diameter are discouraged unless it can be demonstrated that orifices with smaller diameters are necessary to meet the release rate criteria above. All orifices shall be protected from clogging and sedimentation.
B. 
In selecting appropriate BMPs the applicant shall consider the following:
(1) 
Total contributing area.
(2) 
Permeability and infiltration rate of the site soils.
(3) 
Slope and depth to bedrock.
(4) 
Seasonal high water table.
(5) 
Proximity to building foundations and well heads.
(6) 
Erodibility of soils.
(7) 
Land availability and configuration of the topography.
(8) 
Peak discharge and required volume control.
(9) 
Stream bank erosion protection.
(10) 
Efficiency of the BMPs to mitigate potential water quality problems.
(11) 
The volume of runoff that will be effectively treated.
(12) 
The nature of the pollutant being removed.
(13) 
Maintenance requirements.
(14) 
Creation/protection of aquatic and wildlife habitat.
(15) 
Recreational value.
C. 
For areas within defined Special Protection subwatersheds, which includes Exceptional Value (EV) and High Quality (HQ) waters, the temperature and quality of water and streams shall be maintained in accordance with applicable DEP anti-degradation criteria.
D. 
Roof drains shall not be connected to street, sanitary or municipal storm sewers or roadside ditches.
E. 
All stormwater runoff shall be treated for water quality in accordance with current DEP guidelines prior to discharge to surface or groundwater.
F. 
Control facilities which receive stormwater from areas which are a potential source of oil and grease contamination shall include a baffle, skimmer, grease trap or other mechanism suitable for preventing oil and grease from leaving the facility in concentrations that would cause or contribute to a violation of applicable water quality standards in the receiving waters.
G. 
Vector control strategies (such as the selection of hydrophytic plant species) shall be used to minimize mosquito populations in all proposed wet basins.
Applicants are required to maximize groundwater recharge of stormwater generated by proposed development. Infiltration/recharge stormwater management facilities should compensate for the reduction in natural percolation that occurs when the ground surface is disturbed or impervious surfaces are created and should be used in conjunction with other innovative or traditional BMPs, stormwater control facilities and nonstructural stormwater management alternatives. The volume of runoff to be recharged is dependent on site characteristics, as follows:
A. 
A minimum depth of 24 inches is required between the bottom of the BMP and the limiting zone.
B. 
An infiltration and/or percolation rate sufficient to accept the additional stormwater load and drain completely must be determined by field tests conducted by the applicant's design professional.
C. 
The recharge facility shall be capable of completely infiltrating the recharge volume within four days.
D. 
Pretreatment shall be provided prior to infiltration unless the applicant can demonstrate groundwater quality will not be degraded.
E. 
The size of the recharge facility shall be based upon the following volume criteria:
(1) 
The Natural Resources Conservation Service (NRCS) Curve Number (CN) for the property in its existing conditions shall be utilized to calculate infiltration requirements (I) using the following equation:
Equation 1
I(inches) = (200/CN) - 2
(a) 
The required recharge volume shall be calculated by multiplying the infiltration requirement (I) by the proposed impervious area:
Equation 2
Required recharge volume = (I) x (Impervious Area)
(b) 
Applicants must note that the infiltration requirement (I) is in inches. The NRCS Curve Number conversion to infiltration requirement is shown graphically below.
123 NRCS Curve.tif
Figure 1. Infiltration requirement based upon NRCS Curve Number.
(2) 
If the site does not include a suitable area for recharge with a minimum depth of 24 inches between the bottom of the BMP and the limiting zone required in § 123-11A above, then 0.6 inch of rainfall shall be infiltrated from all impervious areas, up to an existing site condition curve number of 77. Above an existing condition curve number of 77, Equation 1 or the CN from Figure 1 should be used to determine the Infiltration requirement.
(3) 
A detailed soils evaluation is required to determine the suitability of recharge facilities. The evaluation shall be performed by a Design Professional, and at a minimum, address soil permeability, depth to bedrock and subgrade stability. The general process for designing the infiltration BMP shall be:
(a) 
Analyze hydrologic soil groups as well as natural and man-made features within the watershed to determine general areas of suitability for infiltration practices.
(b) 
Provide site-specific infiltration test results (at the level of the proposed infiltration surface) in accord with applicable ASTM guidelines to determine the appropriate hydraulic conductivity rate.
(c) 
Design the infiltration structure for the required storm volume based on field-determined capacity at the level of the proposed infiltration surface.
(d) 
In residential developments where individual on-lot recharge areas are proposed, along with providing infiltration test results on each proposed lot in accordance with (b), above, the applicant must show the infiltration areas on the development plans as boxes depicting 110% of the required area, and be located on the plan by a minimum of two bearings and distances from known, fixed points. Easements are required on each lot to provide the Township with access for inspection. Agreements formalizing maintenance requirements and responsibilities must be approved by the Board of Supervisors.
F. 
Additional recharge requirement exemptions and exceptions.
(1) 
Land uses that generate higher concentrations of hydrocarbons, trace metals or toxicants than are found in typical stormwater runoff such as vehicle salvage yards and recycling facilities, fleet storage areas (bus, truck, etc.), public works storage areas and facilities that generate or store hazardous materials, shall not recharge stormwater from those areas where pollutants could be released due to facility operations or accidental spills without DEP approved pretreatment of all such runoff.
(2) 
Infiltration area(s) shall not be located in any Wellhead Protection Zone 1.
(3) 
A detailed hydrogeologic investigation may be required by the Township if stormwater runoff could contain hazardous materials or hazardous waste.
G. 
Recharge/infiltration facilities shall be used in conjunction with other innovative or traditional BMPs, stormwater control facilities, and nonstructural stormwater management alternatives.
A. 
The Brodhead/McMichaels Watershed has been divided into stormwater management districts as shown on the Watershed Map in Appendix D of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update. Standards for managing runoff from design storms for each of the districts located in Paradise Township are shown in Figure 2. Development sites located in each of the districts must control proposed conditions runoff rates to existing conditions runoff rates for the design storms in accord with Figure 2.
District
Proposed Conditions
(reduce to)
Existing Conditions
A
2-year
1-year
5-year
5-year
10-year
10-year
25-year
25-year
50-year
50-year
100-year
100-year
B-1
2-year
1-year
5-year
2-year
10-year
5-year
25-year
10-year
50-year
25-year
100-year
100-year
B-2
2-year
1-year
5-year
2-year
25-year
5-year
50-year
10-year
100-year
50-year
B-3
50-year
10-year
100-year
50-year
Figure 2. Standards for managing runoff.
B. 
The boundaries of the stormwater management districts are shown on an Official Map that is available for inspection at the Township office. A copy of the Official Map at a reduced scale is included in Appendix D of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update. The exact location of the Stormwater Management District boundaries as they apply to a given development site shall be determined by mapping the boundaries using the topographic contours provided as part of the Stormwater Management Plan.
C. 
For a proposed development site located within two or more subareas of a stormwater management district, the peak discharge rate from each subarea shall be the existing conditions peak discharge for that subarea. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area. If discharges from multiple subareas recombine prior to discharge from the site, peak discharge in any direction may be a 100% release rate provided that the overall site discharge meets the release rate criteria for the site.
D. 
Off-site areas that drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates. However, on-site drainage facilities shall be designed to safely convey off-site flows through the development site.
E. 
Areas of a site that will remain undeveloped and that bypass the stormwater management facilities are not subject to the management district criteria.
F. 
A less restrictive runoff control (including no detention) shall be allowed if the applicant can demonstrate that proposed hydrographs match existing hydrographs, or that proposed conditions will not increase peak flows at all points downstream and that the hydrologic regime of the site will be maintained. Hydrologic and hydraulic calculations must show any/all impacts of proposed development and indicate any/all hydrograph timing modifications that will result on a dam, highway, structure, natural point of restricted streamflow or any stream channel section, established with the concurrence of the Township Engineer. The evaluation to demonstrate no impact must continue downstream until the increase in flow diminishes due to additional flow from tributaries and/or stream attenuation. The peak flow values to be used for downstream areas for the design return period storms (two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year) shall be the values from the calibrated model for the Brodhead/McMichaels Watershed. These flow values can be obtained from the original Act 167 watershed stormwater management plan. Less restrictive runoff controls shall not be allowed if peak flows would be increased at storm drainage problem areas unless the applicant includes downstream capacity improvements to mitigate the existing drainage problems.
G. 
Any downstream hydraulic capacity analysis conducted in order to accomplish (F), above, must demonstrate the following:
(1) 
Existing natural or man-made channels or swales must be able to convey the increased runoff associated with a two-year design storm within their banks at velocities consistent with protection of the channels from erosion. Acceptable velocities shall be based upon criteria included in the DEP Erosion and Sediment Pollution Control Program Manual.
(2) 
Existing natural or man-made channels or swales must be able to convey increased twenty-five-year design storm without creating any hazard to persons or property.
(3) 
Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area must be designed in accordance with PADEP Chapter 105 regulations (if applicable) and, at minimum, pass the increased twenty-five-year design storm runoff.
A. 
Stormwater runoff from all development sites with a drainage area of greater than 200 acres shall be calculated using a generally accepted calculation technique that is based on the NRCS soil cover complex method. Table 1 summarizes acceptable computation methods and the method selected by the design professional shall be based on the individual limitations and suitability of each method for a particular site. The Rational Method may be used to estimate peak discharges from drainage areas that contain less than 200 acres. The Soil Cover Complex Method shall be used for drainage areas greater than 200 acres.
Method
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 within limitations described in TR-55
HEC-1/HEC-HMS
US Army Corps of Engineers
Applicable where use of full hydrologic computer model is desirable or necessary
PSRM
Penn State University
Applicable where use of a hydrologic computer model is desirable or necessary simpler than TR-20 or HEC-1
Rational Method
(or commercial computer package based on Rational Method)
Emil Kuichling (1889)
For sites less than 200 acres, or as approved by the Township and/or the Township Engineer
Other Methods
Varies
Other computation methodologies approved by the Township and/or the Township Engineer
Figure 3. Calculation methodologies.
B. 
All calculations using the Soil Cover Complex Method shall use the appropriate design rainfall depths for the various return period storms according to the region in which they are located as presented in Table B-1 in Appendix B of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update. If a hydrologic computer model such as PSRM or HEC-1 is used for stormwater runoff calculations, then the duration of rainfall shall be 24 hours. The SCS 'S' curve shown in Figure B-1, Appendix B of this Ordinance shall be used for the rainfall distribution.
C. 
For the purposes of existing conditions flow rate determination, undeveloped land shall be considered as "meadow" in good condition, unless the natural ground cover generates a lower curve number or Rational 'C' value, as listed in Table B-2 or B-3 in Appendix B of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update.
D. 
All calculations using the Rational Method shall use rainfall intensities consistent with appropriate times-of-concentration for overland flow and return periods from the Design Storm Curves from PennDOT Design Rainfall Curves (1986) (Figures B-2 to B-4 of Appendix B of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update). Times-of-concentration for overland flow shall be calculated using the methodology presented in Chapter 3 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as amended or replaced from time to time by NRCS). Times-of concentration for channel and pipe flow shall be computed using Manning's equation.
E. 
Runoff Curve Numbers (CN) for both existing and proposed conditions to be used in the soil cover complex method shall be obtained from Table B-2 in Appendix B of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update.
F. 
Runoff coefficients (c) for both existing and proposed conditions for use in the Rational Method shall be obtained from Table B-3 in Appendix B of this Ordinance.
G. 
The designer shall consider that the runoff from proposed sites graded to the subsoil will not have the same runoff conditions as the site under existing conditions, even after topsoiling or seeding. The designer may increase his proposed condition "CN" or "c" to better reflect proposed soil conditions.
H. 
Where uniform flow is anticipated, the Manning Equation shall be used for hydraulic computations, and to determine the capacity of open channels, pipes, and storm sewers. Values for Manning's roughness coefficient (n) shall be consistent with Table B-4 in Appendix B of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update.
I. 
Outlet structures for stormwater management facilities shall be designed to meet the performance standards of this Ordinance using any generally accepted hydraulic analysis technique or method.
J. 
The design of any stormwater detention facilities intended to meet the performance standards of this Ordinance shall be verified by routing the design storm hydrograph through these facilities using the Storage-Indication Method. For drainage areas greater than 200 acres in size, the design storm hydrograph shall be computed using a calculation method that produces a full hydrograph.
A. 
Any stormwater management facility designed to store runoff and requiring a berm or earthen embankment shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year design storm proposed conditions. The height of embankment must provide a minimum one foot of freeboard above the maximum pool elevation computed when the facility functions for the one-hundred-year event maximum pool elevation assuming all design orifices are blocked.
B. 
Conveyance facilities leading to or exiting from stormwater management facilities shall be designed to convey the design flow to or from that structure. The total drainage conveyance system must be able to convey, without damage to any drainage structure or roadway, runoff from the one-hundred-year design storm. Any open conveyance facilities designed to handle the entire one-hundred-year design storm shall maintain a minimum one foot of freeboard measured between the water level and top of bank. All conveyance facilities shall be contained within the lines of a drainage easement.
C. 
In no event shall individual storm sewers, roadside swales, and inlet systems be designed to convey less than proposed conditions runoff from a twenty-five-year design storm without surcharging inlets. Storm sewer pipes shall be constructed of concrete or approved plastic pipe. A minimum slope of 1% shall be provided for corrugated storm sewer and 0.5% for smooth lined storm sewers.
D. 
Stormwater gutter flows shall not exceed 1/2 of a through travel lane or one inch less than the depth of curb for curbed sections of roadway, or 2/3 of the design shoulder during a ten-year design storm of a five minute duration.
E. 
Storm Sewers shall meet the following standards:
(1) 
All storm sewer structures shall be constructed of reinforced concrete in accordance with current PennDOT 408 or RC-34 standards.
(2) 
All storm sewer structures shall provide for a minimum 1/10 foot drop from the lowest inlet pipe invert elevation and the outlet pipe invert elevation.
(3) 
When there is a change in pipe size throughout a storm sewer pipe system, the elevation of the crowns of the pipe shall be matched, or the crown of the smaller pipe shall be higher.
(4) 
All inlets proposed in curblines shall be "Type C" inlets.
F. 
Stormwater management shall not alter the existing points of concentrated drainage discharge onto adjacent property or existing road rights-of-way.
(1) 
Areas of existing drainage onto adjacent property or existing road right-of-way shall be managed such that, at minimum, the peak flow does not increase in the general direction of discharge, except as otherwise provided in this chapter. If the flow is proposed to be concentrated and discharged onto the adjacent property, the developer must document that there are adequate downstream conveyance facilities to safely transport the concentrated discharge or otherwise prove that no harm will result from the concentrated discharge. Areas of existing drainage discharge shall be subject to any applicable release rate criteria in the general direction of existing discharge whether they are proposed to be concentrated or maintained as diffused drainage areas. Written permission must be obtained from the adjacent downstream landowner to discharge onto their property.
(2) 
Where existing drainage patterns or watercourses traverse a subdivision or area of earth disturbance a drainage easement is required. Said drainage easement should conform with the line of the existing drainage pattern. The width of the easement shall be adequate to provide for unimpeded flow of storm runoff based on calculations made for the one-hundred-year design storm runoff.
The terms of the easement shall prohibit excavation, the placing of fill or controls and any alterations which may adversely affect the flow of stormwater within any portion of the easement. Also, periodic cutting of vegetation in all portions of the easement may be required as specified by § 123-27 through § 123-29.
G. 
Where stormwater drainage is to cross a roadway, culverts with headwalls shall be provided.
(1) 
Road culverts shall be designed to a capacity to accommodate the twenty-five-year frequency storm event.
(2) 
Culverts shall be constructed of concrete pipe or approved plastic pipe with a minimum diameter of 15 inches.
(3) 
Driveway culverts shall be sized for each lot to provide the required capacity in the roadside swale. These sizes shall be listed on the final plans.
H. 
Where detention basins are proposed the following standards shall apply:
(1) 
Detention basin setbacks. All setbacks shall be measured from the pool location of the basin at the elevation of the emergency spillway or the toe of the embankment, whichever is the more restrictive.
(a) 
Property lines: 15 feet.
(b) 
Road rights-of-way: 15 feet.
(c) 
Streams: 50 feet from top of bank.
(2) 
No basin, dissipaters or waterways may be located closer than 250 feet from any downslope existing or proposed dwellings, septic system or well in such a manner that failure of the structure could cause damage to these items.
(3) 
The basin is to be sodded or topsoiled and seeded, including the bottom, side slopes and all earthen dams and embankments.
(4) 
Suitable lining shall be required to all points of inflow to the basin where erosion and scour may occur.
(5) 
An easement to allow maintenance crews access to the basin and outlet areas shall be established around all basins to be maintained. The limits of such easements shall be 15 feet from the outside toe of all dams and embankments and top of all pond side slopes and shall be connected to a public right-of-way.
(6) 
The design dimensions of the detention basins shall be maintained throughout construction unless it is to be used as a sedimentation basin during construction in the watershed. If so, it shall be immediately returned to design requirements following the completion of such construction. If used as a temporary sedimentation basin, it shall be designed based upon PADEP standards for sedimentation basins.
(7) 
The inlet shall enter at the opposite end of the basin from the discharge, if possible. If not used for approved infiltration, the basins shall have a minimum bottom slope of 1% towards the primary drainage and prevent saturated conditions, swampy conditions and maintenance problems. Low flow channels may be required to convey small inflows to the basin outlet.
(8) 
Side slopes shall be a maximum of three feet horizontal to one foot vertical, unless the design slopes are less than three feet deep, whereas a four to one slope is required. The design engineer may propose steeper side slopes if justifiable evidence is submitted.
(9) 
Basins greater than three feet deep shall be fenced the entire perimeter to keep out children. A basin less than three feet deep may have three to one side slopes if fencing is provided. A gate shall be installed to allow access to the basin for maintenance.
(10) 
In many instances, the provision of separate detention facilities for a number of single sites may be more expensive and more difficult to maintain than provision of joint facilities for a number of sites. In such cases, the Township will be willing to consider provision of joint detention facilities which will fulfill the requirements of this regulation. In such cases, a properly planned, staged program of detention facilities may be approved by the Township in which compliance with some requirements may be postponed at early stages, while construction of preliminary phases are being undertaken. This shall pertain to stormwater management only and not erosion and sediment pollution control.
(11) 
Safety ledges shall be constructed on the side slopes of all detention basins having a permanent pool of water. The ledges shall be four feet to six feet in width and located approximately 2 1/2 to three feet below and one foot to 1 1/2 feet above the permanent water surface.
(12) 
Where the project consists of more than one phase, the stormwater controls shall be designed so that the rate of runoff for the ultimate build-out condition is consistent with the release rate specified in the plan. The outlet structure may have to be modified for the first phase. The stormwater detention basin shall be constructed prior to the construction of the first phase.
(13) 
An erosion and sediment pollution control plan and narrative shall be developed for the detention basin. This plan shall be included in the erosion and sediment pollution control plan for the site.
(14) 
Outlet structures and outlet pipes larger than 15 inches shall be constructed of reinforced concrete. All outlet structures shall include properly sized anti-seep collars.
(15) 
All basins shall have, at a minimum, a primary outlet used to control the design storm and an emergency spillway to safely convey the one-hundred-year design storm with one foot of freeboard. The emergency spillway shall be constructed in undisturbed virgin soil and stabilized accordingly. Spillways shall be suitably lined. The maximum permissible velocity for the outlet shall be based upon current PADEP standards. All outlets must exit to an existing swale, stream or watercourse of adequate size to convey the design release rate in addition to existing flow, and the quantity, velocity and direction of flow shall be managed to protect health and property from possible injury. Outlets shall be designed to function without manual, electric or mechanical controls where possible.
(a) 
Applicant must demonstrate that adequate conveyance system capacity exists between the project site and discharge to the first natural watercourse, and that no damage to properties existing between the project site and said natural watercourse will occur or be exacerbated by the proposed conditions additional flow.
(b) 
Maximum velocities in emergency spillways shall be determined based on the velocity of the peak flow in the spillway resulting from the routed emergency spillway hydrograph. Where maximum velocities exceed those contained in Appendix 67, page 36, of the PADEP Sedimentation and Erosion Control Manual or its successor, suitable lining shall be provided.
I. 
Where dams and embankments are proposed the following standards shall apply:
(1) 
The minimum top widths of all dams and embankments are listed below.
Minimum Top Widths
Heights
(feet)
Top Width
(feet)
0 to 3
4
3 to 5
6
5 to 15
8
15 to 20
10
20 to 25
14
(2) 
The design top elevation of all dams and embankments, after all settlement has taken place, shall be equal to the maximum water surface elevation in the basin resulting from the routed one-hundred-year storm, plus 12 inches. Therefore, the design height of the dam or embankment, defined as the vertical distance from the top down to the bottom of the deepest cut, shall be increased by the amount needed to ensure that the design top elevation will be maintained following all settlement. This increase shall not be less than 5%.
(3) 
All earth fill shall be free from brush, roots and other organic material subject to decomposition.
(4) 
The fill material in all earth dams and embankments shall be compacted to at least 95% of the maximum density obtained from compaction tests performed by the appropriate ASTM method.
A. 
Any earth disturbance must be conducted in conformance with PA Title 25, Chapter 102, "Erosion and Sediment Control."
B. 
Additional erosion and sediment control design standards and criteria that must be or are recommended to be applied where infiltration BMPs are proposed shall include the following:
(1) 
Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase to maintain maximum infiltration capacity.
(2) 
Infiltration BMPs shall not be constructed nor receive runoff until the entire contributory drainage area to the infiltration BMP has achieved final stabilization.
All Regulated Activities shall submit a "Consumptive Use Tracking Report" (CUTR), which shall be developed in accordance with Appendix F of the Brodhead and McMichaels Creek Watershed Act 167 Stormwater Management Plan Update, to the Monroe County Conservation District.