A. 
Applicants proposing regulated activities in Brodhead/McMichaels Creek Watershed which do not fall under the exemption criteria shown in § 92-18 shall submit a drainage plan consistent with the Brodhead/McMichaels Creek Watershed Stormwater Management Plan to the municipality for review. These criteria shall apply to the total proposed development even if development is to take place in stages.
B. 
The applicant is required to perform an alternatives analysis 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. 
The drainage plan must be designed through an alternatives analysis consistent with the sequencing provisions of § 92-9 to ensure maintenance of the natural hydrologic regime and to promote groundwater recharge and protect groundwater and surface water quality and quantity. The drainage plan designer must proceed sequentially in accordance with Article III of this chapter.
D. 
Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with this chapter.
E. 
The existing points of concentrated drainage that discharge onto adjacent property shall not be altered in any manner which could cause property damage without permission of the affected property owner(s) and shall be subject to any applicable discharge criteria specified in this chapter.
F. 
Areas of existing diffused drainage discharge shall be subject to any applicable discharge criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas, except as otherwise provided by this chapter. If diffused drainage discharge is proposed to be concentrated and discharged onto adjacent property, the applicant must document that adequate downstream conveyance facilities exist to safely transport the concentrated discharge, or otherwise prove that no erosion, sedimentation, flooding or other impacts will result from the concentrated discharge.
G. 
Where a development site is traversed by existing watercourses, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easement shall conform to the stream buffer requirements contained in § 92-10I of this chapter.
H. 
All drainage plans shall include a consumptive use tracking report as required in § 92-16.
I. 
Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the Commonwealth or wetlands shall be subject to approval by PaDEP through the joint permit application process, or, where deemed appropriate by PaDEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the applicant or his agent to show that the land in question cannot be classified as wetlands; otherwise, approval to work in the area must be obtained from PaDEP.
J. 
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).
K. 
Infiltration of runoff through seepage beds, infiltration trenches, etc., where soil conditions permit, and minimization of impervious surfaces to the extent permitted by the municipality's Zoning Ordinance are encouraged to reduce the size or eliminate the need for, detention facilities or other structural BMPs.
L. 
Roof drains shall not be connected to streets, sanitary or storm sewers or roadside ditches in order to promote overland flow and infiltration/percolation of stormwater where advantageous to do so. Considering potential pollutant loading, roof drain runoff in most cases will not require pretreatment.
M. 
All stormwater runoff, other than rooftop runoff discussed in Subsection L above, shall be treated for water quality prior to discharge to surface or groundwater.
A. 
The design of all regulated activities shall include the following steps in sequence to minimize stormwater impacts.
(1) 
The applicant is required 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 of the site.
(2) 
An alternative is practicable if it is available and capable of being done after taking into consideration cost, existing technology and logistics in light of overall project purposes.
(3) 
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.
B. 
The applicant shall demonstrate that he or she designed the regulated activities in the following sequence to minimize the increases in stormwater runoff and impacts to water quality:
(1) 
Prepare an Existing Resource and Site Analysis Map (ERSAM), showing environmentally sensitive areas including, but not limited to, steep slopes, ponds, lakes, streams, wetlands, hydric soils, vernal ponds, floodplains, buffer areas, hydrologic soil groups A and B (areas conducive to infiltration), any existing recharge areas and any other requirements outlined in the municipal Subdivision and Land Development Ordinance.[1]
[1]
Editor's Note: See Ch. 98, Subdivision and Land Development.
(2) 
Establish buffers according to § 92-10.
(3) 
Prepare a draft project layout avoiding earth disturbance in sensitive areas identified in Subsection B(1) and minimizing total site earth disturbance as much as possible. The ratio of the disturbed area to the entire site area and measures taken to minimize earth disturbance shall be included on the ERSAM.
(4) 
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.
(5) 
Evaluate nonstructural stormwater management alternatives.
(a) 
Minimize earth disturbance.
(b) 
Minimize impervious surfaces.
(c) 
Break up large impervious surfaces.
(6) 
Satisfy water quality and streambank erosion protection objective (§ 92-10).
(7) 
Satisfy groundwater recharge (infiltration) objective (§ 92-11) and provide for stormwater treatment prior to infiltration.
(8) 
Determine what management district the site falls into (Appendix D[2]) and conduct a predevelopment runoff analysis.
[2]
Editor's Note: Appendix D is included at the end of this chapter.
(9) 
Prepare final project design to maintain predevelopment drainage areas and discharge points, to minimize earth disturbance and impervious surfaces, and to reduce runoff to the maximum extent possible.
(10) 
Conduct a postdevelopment runoff analysis based on the final design and to meet the release rate and in turn the overbank flow and extreme event requirements (§ 92-12).
(11) 
Manage any remaining runoff through treatment prior to discharge, as part of detention, bioretention, direct discharge or other structural control.
In addition to the performance standards and design criteria requirements of this chapter, the applicant shall comply with the following water quality requirements of this article.
A. 
Requirements.
(1) 
For water quality and streambank erosion, the objective is to design a water quality BMP 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). At the same time, the objective is not to attenuate the larger storms in "no detention" areas (District C) only. This can be accomplished by configuration of the outlet structure not to control the larger storms, or by a bypass or channel to divert only the two-year flood into the basin or divert flows in excess of the two-year storm away from the basin.
(2) 
Where practicable, wet basins shall be utilized for water quality control and shall meet the requirements found in the PA Stormwater BMP manual as revised.
(3) 
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). The design of the facility shall consider and minimize the chances of clogging and sedimentation. Orifices smaller than three inches diameter are not recommended. However, if the design professional can provide proof that the smaller orifices are protected from clogging by use of trash racks, etc., smaller orifices may be permitted.
B. 
In selecting the appropriate BMPs or combinations thereof, 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) 
Streambank erosion.
(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 include exceptional value (EV) and high-quality (HQ) waters, the temperature and quality of water and streams shall be maintained through the use of temperature sensitive BMPs and stormwater conveyance systems.
D. 
The applicant shall consider the guidelines found in the references specified in Appendix G[1] for constructed wetlands, where proposed.
[1]
Editor's Note: Appendix G is on file in the Township offices.
E. 
Pretreatment in accordance with § 92-8L and M shall be provided prior to infiltration.
[Amended 7-16-2019 by Ord. No. 2019-01]
F. 
Streambank restoration projects shall include the following:
(1) 
No restoration or stabilization projects may be undertaken without examining the fluvial geomorphology of stable reaches above and below the unstable reach.
(2) 
Restoration project design must then consider maintenance of stability in the adjacent stable reaches of the stream channel.
(3) 
An erosion and sediment control plan approved by the Conservation District must be provided by the applicant.
(4) 
All applicable state and federal permits must be obtained.
G. 
Biology shall be incorporated into the design of all wet basins in accordance with the West Nile Virus Guidance found in Appendix E.[2]
[2]
Editor's Note: Appendix E is included at the end of this chapter.
H. 
To accomplish the above, the applicant shall submit original and innovative designs to the Municipal Engineer for review and approval. Such designs may achieve the water quality objectives through a combination of BMPs (best management practices).
I. 
Buffers.
(1) 
A project designer shall provide a standard buffer for streams, wetlands, vernal ponds and lakes in § 92-10I(2).
(a) 
Where resource buffers overlap, the more restrictive requirements shall apply.
(b) 
Preexisting lots or parcels/land development plan in outer buffers. In the case of legally preexisting lots or parcels or land development plans (approved prior to the effective date of this chapter) where the usable area of a lot or parcel lies within an outer buffer area, rendering the lot or parcel unable to be developed in accordance with the allowable use per municipal zoning, the development may only be permitted by modification as provided in § 98-38 of the municipality's SALDO.
(c) 
Improvements to existing structures in outer buffers. The provisions of this section do not require any changes or improvements to be made to lawfully existing structures in buffers. However, when any substantial improvement to a structure is proposed which results in a horizontal expansion of that structure, the improvement may only be permitted by modification as provided in § 98-38 of the municipality's SALDO.
(2) 
Standard buffers for water quality.
(a) 
Wetlands and vernal ponds.
[1] 
Wetland identification. Wetlands shall be identified in accord with the 1987 U.S. Army Corps of Engineers Manual for Identifying and Delineating Wetlands, as amended, and properly flagged and surveyed on site.
[a] 
Wetlands in an artificial watercourse. Wetlands contained within the banks of an artificial watercourse shall not to be considered for buffer delineation purposes.
[b] 
Wetlands in a natural watercourse. Where wetlands are contained within the banks of a natural watercourse, only the stream buffer shall apply.
[2] 
Wetland and vernal pond buffer delineation. A fifty-foot inner buffer and one-hundred-foot outer buffer, measured perpendicular to and horizontally from the edge of the delineated wetland or vernal pond for a total distance of 150 feet, shall be maintained for all wetlands and vernal ponds.
[a] 
Inner buffer: measured perpendicular to and horizontally from the edge of the delineated wetland or vernal pond, for a distance of 50 feet.
[i] 
Stormwater conveyance required by the Township, buffer maintenance and restoration, the correction of hazardous conditions, wetland crossings permitted by DEP and passive unpaved stable trails shall be permitted. No other earth disturbance, grading, filling, buildings, structures, new construction, or development shall be permitted.
[ii] 
The area of the inner buffer altered by activities permitted in accord with § 92-10I(2)(a)[2][a][i] shall be minimized to the greatest extent practicable.
[b] 
Outer buffer: measured perpendicular to and horizontally from the outer edge of the inner buffer for a distance of 100 feet.
[i] 
Provided no buildings are constructed, stormwater conveyance required by the Township, buffer maintenance and restoration, the correction of hazardous conditions, wetland crossings permitted by DEP, parking lots constructed to existing grade, roads constructed to existing grade, stable trails, and limited forestry activities that do not clear cut the buffer (e.g., selective regeneration harvest) in accord with a forestry management plan shall be permitted.
[ii] 
No more than 20% of the cumulative outer buffer on the subject parcel shall be altered by the activities permitted in accord with § 92-10I(2)(a)[2][b][i] above.
(b) 
Lakes and ponds.
[1] 
There is no outer buffer around lakes and ponds.
[2] 
Lake and pond buffer delineation. A fifty-foot buffer measured perpendicular to and horizontally from the edge of any lake or pond shall be maintained.
[3] 
Permitted activities/development. Stormwater conveyance required by the Township, buffer maintenance and restoration, the correction of hazardous conditions, lake front views, boat docks and passive unpaved stable trails shall be permitted provided no buildings are involved.
[4] 
No more than 35% of the cumulative pond or lake buffer on the subject parcel shall be altered by the activities permitted in accord with § 92-10I(2)(b)[3] above.
(c) 
Streams.
[1] 
Stream buffer delineation. A fifty-foot inner buffer and one-hundred-foot outer buffer, measured perpendicular to and horizontally from the top-of-bank on both sides of any stream, for a total distance of 150 feet, shall be maintained. See Figure 1 below.
092 Fig. 303.1.tif
Figure 1. Stream Buffer
[a] 
Inner buffer: measured perpendicular to and horizontally from the top-of-bank of the stream for a distance of 50 feet.
[i] 
Stormwater conveyance required by the Township, buffer maintenance and restoration, the correction of hazardous conditions, stream crossings permitted by DEP, fish hatcheries, wildlife sanctuaries and boat launch sites constructed so as not to alter the floodplain cross-section, and passive unpaved stable trails shall be permitted provided no buildings are constructed. No other earth disturbance, grading, filling, buildings, structures, new construction, or development shall be permitted.
[ii] 
The area of the inner buffer altered by activities permitted in accord with § 92-10I(2)(c)[1][a][i] shall be minimized to the greatest extent practicable.
[b] 
Outer buffer: measured perpendicular to and horizontally from the outer edge of the inner buffer for a distance of 100 feet.
[i] 
Provided no buildings are constructed, stormwater conveyance required by the Township, buffer maintenance and restoration, the correction of hazardous conditions, agricultural activities, plant nurseries, parking lots constructed to existing grade, temporary fairs and carnivals, accessory uses for residential purposes, private sportsmen's club activities, athletic facilities, orchards, wildlife sanctuaries, boat launch sites that do not alter the floodplain cross-section, fish hatcheries, stream crossings permitted by DEP and passive unpaved stable trails, and limited forestry activities that do not clear-cut the buffer (e.g. selective regeneration harvest) in accord with a forestry management plan shall be permitted.
[ii] 
In areas of the outer buffer which are not wetlands, vernal ponds or slopes of more than 15%, stormwater management facilities which improve water quality of stormwater discharge shall be permitted unless prohibited by other Township or state requirements. No other earth disturbance, grading, filling, buildings, structures, new construction, or development shall be permitted.
[iii] 
No more than 20% of the cumulative outer buffer on the subject parcel shall be altered by the activities permitted in accord with § 92-10I(2)(c)[1][b][i] above.
Maximizing the groundwater recharge capacity of the area being developed is required. Design of the infiltration/recharge stormwater management facilities shall give consideration to providing groundwater recharge to compensate for the reduction in the percolation that occurs when the ground surface is disturbed or impervious surface is created. It is recommended that roof runoff be directed to infiltration BMPs which may be designed to compensate for the runoff from parking areas. These measures are required to be consistent with § 92-2, and take advantage of utilizing any existing recharge areas.
A. 
Infiltration BMPs shall meet the following minimum requirements:
(1) 
Maximum infiltration requirements:
(a) 
Regulated activities will be required to recharge (infiltrate), where practicable, a portion of the runoff created by the development as part of an overall stormwater management plan designed for the site. The volume of runoff to be recharged shall be determined from Subsection A(3)(a) or (b), depending upon demonstrated site conditions.
(2) 
Infiltration BMPs intended to receive runoff from developed areas shall be selected based on suitability of soils and site conditions and shall be constructed on soils that have the following characteristics:
(a) 
A minimum depth of 24 inches 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 as 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 in accordance with § 92-8L and M shall be provided prior to infiltration.
(3) 
The size of the recharge facility shall be based upon the following volume criteria:
(a) 
NRCS Curve Number equation.
[1] 
The NRCS runoff shall be utilized to calculate infiltration requirements (P) in inches. This equation is displayed graphically in, and the infiltration requirement can be determined from Figure 2 below.
For zero runoff: P = I (Infiltration) (inches) = (200 / CN) – 2
Eqn: 304.1
Where: CN = SCS (NRCS) curve number of existing conditions contributing to the recharge facility.
[2] 
The recharge volume required would therefore be computed as:
Rev (cubic feet) = I * impervious area (square feet) / 12
Eqn: 304.2
Where: I = infiltration requirements (inches)
092 Fig. 304.1.tif
Figure 2. Infiltration requirement based upon NRCS Curve Number
(b) 
Annual recharge: water budget approach. It has been determined that infiltrating 0.6 inches of runoff from the impervious areas will aid in maintaining the hydrologic regime of the watershed. Areas in the Township that fall outside of the Broadhead/McMichaels watershed will need to meet a two-year, twenty-four-hour net infiltration rate. If the goals of Subsection A(2)(a) cannot be achieved, then 0.6 inch of rainfall shall be infiltrated from all impervious areas, up to an existing site condition curve number of 77. Above a curve number of 77, Equation 304.1 or the curve in Figure 2 should be used to determine the Infiltration requirement. The recharge volume (Rev) required would therefore be computed as:
Rev = 0.6 or I, whichever is less * % impervious area.
B. 
Soils. A detailed soils evaluation of the project site shall be required where practicable to determine the suitability of recharge facilities. The evaluation shall be performed by a qualified 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:
(1) 
Analyze hydrologic soil groups as well as natural and man-made features within the watershed to determine general areas of suitability for infiltration practices.
(2) 
Provide site-specific infiltration test results (at the level of the proposed infiltration surface) in accord with ASTM Guide No. D 5126 to determine the appropriate hydraulic conductivity rate.
(3) 
Design the infiltration structure for the required storm volume based on field determined capacity at the level of the proposed infiltration surface.
(4) 
If on-lot infiltration structures are proposed by the applicant's design professional, it must be demonstrated to the municipality that the soils are conducive to infiltrate on the lots identified.
C. 
Stormwater hotspots.
(1) 
A "stormwater hotspot" is defined as a land use activity that generates higher concentrations of hydrocarbons, trace metals or toxic materials than are found in typical stormwater runoff, based on monitoring studies. The list below provides samples of designated hotspots. If a site is designated as a hotspot, it has important implications for how stormwater is managed. First and foremost, untreated stormwater runoff from hotspots cannot be allowed to infiltrate into groundwater where it may contaminate water supplies. Therefore, the Rev requirement is not applied to development sites that fit into the hotspot category (the entire WQv must still be treated). Second, a greater level of stormwater treatment may be needed at hotspot sites to prevent pollutant washoff after construction. EPA's NPDES stormwater program requires some industrial sites to prepare and implement a stormwater pollution prevention plan.
(a) 
Classification of stormwater hotspots. The following land uses and activities are samples of stormwater hotspots:
[1] 
Vehicle salvage yards and recycling facilities.
[2] 
Fleet storage areas (bus, truck, etc.).
[3] 
Public works storage areas.
[4] 
Facilities that generate or store hazardous materials.
(2) 
Extreme caution shall be exercised where salt or chloride would be a pollutant since soils do little to filter this pollutant and it may contaminate the groundwater. The qualified design professional shall evaluate the possibility of groundwater contamination from the proposed infiltration/recharge facility and perform a hydrogeologic justification study if necessary. The infiltration requirement in high quality/exceptional value waters shall be subject to the Department's Chapter 93 Antidegradation Regulations. The municipality may require the installation of an impermeable liner in detention basins where the possibility of groundwater contamination exists. A detailed hydrogeologic investigation may be required by the municipality.
(3) 
The municipality shall require the applicant to provide safeguards against groundwater contamination for uses which may cause groundwater contamination, should there be a mishap or spill. (See Appendix E of the complete Act 167 Study.)
D. 
Extreme caution shall be exercised where infiltration is proposed in source water protection areas or that may affect a wellhead or surface water intake.
E. 
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.[1] Standards for managing runoff from each subarea in the Brodhead/McMichaels Watershed for design storms are shown in the table below. Development sites located in each of the A, B, or C Districts must control proposed conditions runoff rates to existing conditions runoff rates for the design storms in accord with the table. In addition to the requirements specified in the table below, the water quality and streambank erosion (§ 92-10), groundwater recharge (§ 92-11), and erosion control (§ 92-15) requirements shall be implemented.
Water Quantity Requirements
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
C
Provisional Direct Discharge District. Development sites which can discharge directly to the main channel or major tributaries or indirectly to the main channel through an existing stormwater drainage system (i.e., storm sewer or tributary) which meets the "Downstream Hydraulic Capacity Analysis" in § 92-12H and is shown by the design professional to not cause a downstream problem may allow an increase in flow as long as no downstream harm is demonstrated. However, sites in District C shall comply with the criteria for water quality and streambank erosion (§ 92-10); and groundwater recharge (§ 92-11). If the proposed conditions runoff is intended to be conveyed by an existing stormwater drainage system to the main channel, assurance must be provided that such system has adequate capacity to convey the increased peak flows or will be provided with improvements to furnish the required capacity. When adequate capacity of the downstream system does not exist and will not be provided through improvements, the proposed conditions peak rate of runoff must be controlled to the existing conditions peak rate as required in District A provisions (i.e., ten-year proposed conditions flows to ten-year existing conditions flows) for the specified design storms.
[1]
Editor's Note: Appendix D is included at the end of this chapter.
B. 
General. Proposed conditions rates of runoff from any regulated activity shall not exceed the peak release rates of runoff prior to development for the design storms specified on the Stormwater Management District Watershed Map (Appendix D[2]) and § 92-9, of this chapter.
[2]
Editor's Note: Appendix D is included at the end of this chapter.
C. 
District boundaries. The boundaries of the Stormwater Management Districts are shown on an official map that is available for inspection at the municipal office. A copy of the official map at a reduced scale is included in Appendix D. 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 two-foot topographic contours (or most accurate data required) provided as part of the drainage plan.
D. 
Sites located in more than one district. For a proposed development site located within two or more stormwater management district category subareas, the peak discharge rate from any subarea shall be the existing conditions peak discharge for that subarea as indicated in § 92-9. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea. An exception to the above may be granted by the municipalities if discharges from multiple subareas recombine in proximity to the site. In this case, peak discharge in any direction may be a one-hundred-percent release rate provided that the overall site discharge meets the weighted average release rate.
E. 
Off-site areas. 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.
F. 
Site areas. Where the site area to be impacted by a proposed development activity differs significantly from the total site area, only the proposed impact area utilizing stormwater management measures shall be subject to the management district criteria. In other words, unimpacted areas bypassing the stormwater management facilities would not be subject to the management district criteria.
G. 
"No harm" option. For any proposed development site not located in a provisional direct discharge district, the applicant has the option of using a less-restrictive runoff control (including no detention) if the applicant can prove that no harm would be caused by discharging at a higher runoff rate than that specified by the stormwater management plan. The no-harm option is used when an applicant can prove that the proposed hydrographs can match existing hydrographs, or if it can be proved that the proposed conditions will not cause increases in peaks at all points downstream. Proof of no harm must be shown based upon the following downstream impact evaluation which shall include a downstream hydraulic capacity analysis consistent with § 92-12H to determine if adequate hydraulic capacity exists. The applicant shall submit to the municipality this evaluation of the impacts due to increased downstream stormwater flows in the watershed.
(1) 
The hydrologic regime of the site must be maintained.
(2) 
The downstream impact evaluation shall include hydrologic and hydraulic calculations necessary to determine the impact of hydrograph timing modifications due to the proposed development upon a dam, highway, structure, natural point of restricted streamflow or any stream channel section, established with the concurrence of the municipality.
(3) 
The evaluation shall continue downstream until the increase in flow diminishes due to additional flow from tributaries and/or stream attenuation.
(4) 
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 plans.
(5) 
Applicant-proposed conditions runoff controls which would generate increased peak flow rates at storm drainage problem areas would, by definition, be precluded from successful attempts to prove no harm, except in conjunction with proposed capacity improvements for the problem areas consistent with § 92-12H.
(6) 
A financial distress shall not constitute grounds for the municipality to approve the use of the no-harm option.
(7) 
Downstream capacity improvements may be provided as necessary to achieve the no-harm option.
(8) 
Any no-harm justifications shall be submitted by the applicant as part of the drainage plan submission per Article IV.
H. 
Downstream hydraulic capacity analysis. Any downstream hydraulic capacity analysis conducted in accordance with this chapter shall use the following criteria for determining adequacy for accepting increased peak flow rates:
(1) 
Existing natural or man-made channels or swales must be able to convey the increased runoff associated with a two-year return period event 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 return period runoff 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 DEP Chapter 105 regulations (if applicable) and, at minimum, pass the increased twenty-five-year return period runoff.
I. 
Hardship option. The stormwater management plan and its standards and criteria are designed to maintain existing conditions peak flows and volumes throughout the Brodhead/McMichaels watershed as the watershed becomes developed. There may be certain instances, however, where the standards and criteria established are too restrictive for a particular applicant. The existing drainage network in some areas may be capable of safely transporting slight increases in flows without causing a problem or increasing flows elsewhere. If an applicant cannot meet the stormwater standards due to lot conditions or if conformance would become a hardship to an applicant, the hardship option may be applied. A financial distress shall not constitute grounds for the municipality to approve the use of the hardship option. The applicant would have to plead his/her case to the governing body with the final determination made by the municipality. Any applicant's pleading the hardship option will assume all liabilities that may arise due to exercising this option. A financial distress shall not constitute grounds for the municipality to approve the use of the no-harm option.
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. The table below summarizes acceptable computation methods; the method selected by the design professional shall be based on the individual limitations and suitability of each method for a particular site. The municipality may allow the use of the Rational Method 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.
Acceptable Computation Methodologies for Stormwater Management Plans
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
U.S. 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 municipality and/or Municipal Engineer
Other methods
Varies
Other computation methodologies approved by the municipality and/or Municipal Engineer
B. 
All calculations consistent with this chapter 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 this chapter.[1] 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 chapter shall be used for the rainfall distribution.
[1]
Editor's Note: Appendix B is included at the end of this chapter.
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 this chapter.
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 PA Department of Transportation Design Rainfall Curves (1986) (Figures B-2 to B-4). 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 this chapter.
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 chapter.
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 this chapter.
I. 
Outlet structures for stormwater management facilities shall be designed to meet the performance standards of this chapter 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 chapter 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. The municipality may approve the use of any generally accepted full hydrograph approximation technique that shall use a total runoff volume that is consistent with the volume from a method that produces a full hydrograph.
A. 
Any stormwater facility located on state highway rights-of-way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).
B. 
Pretreatment in accordance with § 92-8L and M shall be provided prior to infiltration.
C. 
All wet basin designs shall incorporate biologic controls consistent with the West Nile Guidance found in Appendix E.[1]
[1]
Editor's Note: Appendix E is included at the end of this chapter.
D. 
Any stormwater management facility (i.e., BMP, detention basin) designed to store runoff and requiring a berm or earthen embankment required or regulated by this chapter shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year proposed conditions. The height of embankment must provide a minimum 1.0 foot of freeboard above the maximum pool elevation computed when the facility functions for the one-hundred-year proposed conditions inflow. Should any stormwater management facility require a dam safety permit under PaDEP Chapter 105, the facility shall be designed in accordance with Chapter 105 and meet the regulations of Chapter 105 concerning dam safety which may be required to pass storms larger than the one-hundred-year event.
E. 
Any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures), and any work involving wetlands governed by PaDEP Chapter 105 regulations (as amended or replaced from time to time by PaDEP), shall be designed in accordance with Chapter 105 and will require a permit from PaDEP.
F. 
Any other drainage-conveyance facility that does not fall under Chapter 105 regulations must be able to convey, without damage to the drainage structure or roadway, runoff from the twenty-five-year design storm with a minimum 1.0 foot of freeboard measured below the lowest point along the top of the roadway. Any facility that constitutes a dam as defined in PaDEP Chapter 105 regulations may require a permit under dam safety regulations. Any facility located within a PennDOT right-of-way must meet PennDOT minimum design standards and permit submission requirements.
G. 
Any drainage conveyance facility and/or channel not governed by Chapter 105 regulations must be able to convey, without damage to the drainage structure or roadway, runoff from the twenty-five-year design storm. Conveyance facilities to or exiting from stormwater management facilities (i.e., detention basins) shall be designed to convey the design flow to or from that structure. Roadway crossings located within designated floodplain areas must be able to convey runoff from a one-hundred-year design storm. Any facility located within a PennDOT right-of-way must meet PennDOT minimum design standards and permit submission requirements.
H. 
Storm sewers must be able to convey proposed conditions runoff from a twenty-five-year design storm without surcharging inlets, where appropriate.
I. 
Adequate erosion protection shall be provided along all open channels, and at all points of discharge.
J. 
The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The municipality reserves the right to disapprove any design that would result in the construction of or continuation of a stormwater problem area.
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.
A. 
Submissions. All regulated activities shall submit a Consumptive Use Tracking Report (CUTR) which shall be developed in accordance with Appendix F[1] as follows:
(1) 
Residential development or redevelopment. The CUTR shall be submitted to the Monroe County Conservation District along with the erosion and sedimentation control plan.
(2) 
Commercial/industrial development-redevelopment. The CUTR shall be submitted to the Monroe County Conservation District by the applicant along with a copy of the occupancy permit.
[1]
Editor's Note: Appendix F is included at the end of this chapter.