[Ord. No. 3-2023, 7/18/2023]
1. 
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 23-302:
A. 
Preparation and implementation of an approved SWM site plan is required.
B. 
No regulated activities shall commence until the Township, issues written approval of an SWM site plan which demonstrates compliance with the requirements of this chapter.
2. 
The SWM site plans approved by the Township, in accordance with § 23-406, shall be on the project site throughout the duration of the regulated activity.
3. 
The Township may approve measures for substantially meeting the state water quality requirements other than those in this chapter, provided that they meet the minimum requirements of, and do not conflict with, state law, including, but not limited to, the Clean Streams Law.[1]
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
4. 
Where a development site is traversed by an existing watercourse (natural and artificial), a drainage easement shall be provided conforming to the line of such watercourse. Where a riparian buffer is required pursuant to § 23-303, the drainage easement shall conform to the line of the riparian buffer. The terms of the easement shall conform to the riparian buffer requirements contained in § 27-303 of this chapter.
5. 
Any stormwater management facility regulated by this chapter that would be located in or adjacent to waters of the commonwealth or wetlands shall be subject to approval by DEP through the joint permit application process, or, where deemed appropriate by DEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the applicant to show that the land in question cannot be classified as wetlands; otherwise approval to work in the area must be obtained from DEP.
6. 
Any stormwater management facility regulated by this chapter that would be located on state highway rights-of-way shall be subject to approval by PennDOT.
7. 
All stormwater runoff, other than rooftop runoff, shall be treated for water quality prior to discharge to surface or groundwater.
8. 
For all regulated earth disturbance activities, erosion and sediment control BMPs shall be designed, implemented, operated and maintained during the regulated earth disturbance activities (e.g., during construction) to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code and Clean Streams Law. Various BMPs and their design standards are listed in the Erosion and Sediment Pollution Control Manual (E&S Manual), No. 363-2134-008, as amended and updated.
9. 
Impervious areas:
A. 
The measurement of impervious areas shall include all of the impervious areas in the total proposed development even if development is to take place in stages.
B. 
For development taking place in stages, the entire development plan must be used in determining conformance with this chapter.
C. 
For projects that add impervious area to the parcel, the total impervious area on the parcel is subject to the requirements of this chapter; except that the volume controls in § 23-304 and the peak rate controls of § 23-305 do not need to be retrofitted to existing impervious areas that are not being altered by the proposed regulated activity.
10. 
Stormwater flows onto adjacent property shall not be created, increased, decreased, relocated, or otherwise altered without written notification and authorization by the affected property owner(s). Such stormwater flows shall be subject to the requirements of this chapter.
11. 
All regulated activities shall include such measures as necessary to:
A. 
Protect health, safety, and property.
B. 
Meet the water quality goals of this chapter by implementing measures to:
(1) 
Minimize disturbance to floodplains, wetlands, and wooded areas.
(2) 
Maintain or extend riparian buffers.
(3) 
Avoid erosive flow conditions in natural flow pathways.
(4) 
Minimize thermal impacts to waters of the commonwealth.
(5) 
Disconnect impervious surfaces by directing runoff to pervious areas, wherever possible.
C. 
Incorporate methods described in the BMP Manual. If methods other than green infrastructure and low impact development (LID) methods are proposed to achieve the volume and rate controls required under this chapter, the SWM site plan must include a detailed justification demonstrating that the use of LID and green infrastructure is not practicable.
12. 
The design of all facilities over karst shall include an evaluation of measures to minimize adverse effects.
13. 
Infiltration BMPs should be spread out, made as shallow as practicable, and located to maximize use of natural on-site infiltration features while still meeting the other requirements of this chapter.
14. 
Normally dry, open-top, storage facilities should completely drain both the volume control and rate control capacities over a period of time not less than 24 hours and not more than 72 hours from the end of the design storm.
15. 
The design storm rainfall amounts to be used in the analysis of peak rates of discharge should 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.
16. 
For all regulated activities, stormwater management BMPs shall be designed, implemented, operated, and maintained to meet the purposes and requirements of this chapter and to meet all water quality requirements under Title 25 of the Pennsylvania Code, the Clean Streams Law[2] and the Storm Water Management Act.[3]
[2]
Editor's Note: See 35 P.S. § 691.1 et seq.
[3]
Editor's Note: See 32 P.S. § 680.1 et seq.
17. 
Various BMPs and their design standards are listed in the BMP Manual.
18. 
Stormwater conveyance facilities must be able to convey, at a minimum, without damage to the drainage structure, adjacent properties or roadway, runoff from the twenty-five-year design storm. Stormwater conveyance facilities may be required to convey larger design storms based on individual drainage/sub-drainage area characteristics as recommended by the Township Engineer and approved at the discretion of the Board of Supervisors. Stormwater 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. Open channels must be able to convey at a minimum, 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.
19. 
The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The Township reserves the right to disapprove any design that would result in the construction of or continuation of a stormwater problem area.
20. 
All wet basin designs shall incorporate biologic controls consistent with the West Nile Guidance found in Appendix E of the Act 167 Plan.
[Ord. No. 3-2023, 7/18/2023]
1. 
The following exemptions apply:
A. 
Regulated activities that result in cumulative earth disturbance less than one acre and less than 5,000 square feet of new impervious surface are exempt from the requirements in §§ 23-304 and 23-305 and Part 4 of this chapter. These criteria shall apply to the total development even if the development is to take place in phases. The date of the adoption of the original Brodhead and McMichaels Creek Stormwater Management Ordinance shall be the starting point from which to consider tracts as "parent tracts" in which future subdivisions and respective impervious area computations shall be cumulatively considered. Impervious areas existing on the "parent tract" prior to adoption of the original ordinance shall not be considered in cumulative impervious area calculations for exemption purposes.
B. 
Agricultural activity is exempt from the SWM site plan preparation requirements of this chapter, provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
C. 
Forest management and timber operations are exempt from the SWM site plan requirements of this chapter, provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
D. 
High tunnels shall be exempt from the provisions of this chapter if both of the following criteria are met:
(1) 
The high tunnel or its flooring does not result in an impervious area exceeding 25% of all structures located on the owner's total contiguous land area.
(2) 
The high tunnel meets one of the following:
(a) 
The high tunnel is located at least 100 feet from any perennial stream or watercourse, public road or neighboring property line.
(b) 
The high tunnel is located at least 35 feet from any perennial stream or watercourse, public road or neighboring property line and is located on land with a slope not greater than 7%.
(c) 
The high tunnel is supported with a buffer or diversion system that does not directly drain into a stream or other watercourse managing stormwater runoff in a manner consistent with requirements of this chapter and the Act of April 18, 2018, P.L. 91, No. 15, and the Act of October 4, 1978 (P.L. 864, No. 167).[1]
[1]
Editor's Note: See 32 P.S. § 680.1 et seq.
2. 
Exemptions from any provisions of this chapter shall not relieve the applicant from the requirements in § 23-301, Subsections 9 through 20.
3. 
The Township may deny or revoke any exemption pursuant to this section at any time for any project that the Township believes may pose a threat to public health, safety or the environment.
[Ord. No. 3-2023, 7/18/2023]
1. 
Riparian Buffer Establishment. In order to protect and improve water quality, riparian buffers are required adjacent to streams, wetlands, lakes, and ponds.
A. 
Wetlands.
(1) 
A 100-foot inner riparian buffer and fifty-foot outer riparian buffer measured perpendicular to and horizontally from the edge of the delineated wetland, for a total distance of 150 feet, shall be maintained for all wetlands.
(2) 
For purposes of establishing riparian buffers, wetlands shall be identified in accord with the 1987 U.S. Army Corps of Engineers Manual for Identifying and Delineating Wetlands, as may be amended, and properly flagged, surveyed, and plotted on the SWM site plan.
(3) 
Wetlands in an artificial watercourse. Wetlands contained within the banks of an artificial watercourse shall not be considered for riparian buffer delineation purposes.
B. 
Streams. A 100-foot inner buffer and fifty-foot outer buffer measured perpendicular to and horizontally from the top of streambank on both sides of any stream, for a total distance of 150 feet, shall be maintained on both sides of any stream.
C. 
Lakes and Ponds. A 100-foot inner buffer measured perpendicular to and horizontally from the edge of any lake or pond shall be maintained. There is no outer buffer around lakes and ponds.
D. 
Where resource buffers overlap, the more restrictive requirements shall apply.
2. 
Activities Prohibited/Permitted in a Riparian Buffer. No earth disturbance, grading, filling, buildings, structures, new construction, or development shall be permitted in the riparian buffer except for those activities specifically listed as permitted activities in this section. Septic drain fields and sewage disposal systems shall not be permitted within the riparian buffer and shall comply with setback requirements established under 25 Pa. Code Chapter 73.
A. 
Activities Permitted in the Inner Buffer. The following activities shall be permitted in the inner buffer, provided no buildings are involved and disturbance to the buffer is minimized to the greatest extent practicable; and for pond/lake buffer, provided the area of the buffer impacted by the permitted activities shall not exceed 35% of the cumulative buffer on the property.
(1) 
Public and private recreation trails for non-motorized use only. Trails shall be stable and unpaved and be designed to have the least impact on native plant species and other sensitive environmental features.
(2) 
Stormwater conveyance facilities approved by the Township.
(3) 
Buffer maintenance and restoration.
(4) 
The correction of hazardous conditions.
(5) 
Disturbance activities requiring a DEP permit in conjunction with a Township-approved project.
(6) 
Fish hatcheries.
(7) 
Wildlife sanctuaries.
(8) 
Boat docks and boat launch sites constructed so as not to alter the floodplain cross section.
(9) 
Lakefront views.
B. 
Activities Permitted in the Outer Buffer. The following activities shall be permitted in the outer buffer, provided no buildings are involved and no more than 20% of the cumulative outer buffer on the project site shall be altered by the activities:
(1) 
Activities permitted in the inner buffer.
(2) 
Stormwater BMPs permitted by the Township.
(3) 
Roads constructed within two feet of existing grade.
(4) 
Limited forestry activities that do not clear cut the buffer (e.g., selective regeneration harvest) in accord with a forest management plan.
(5) 
Improvements to an existing structure resulting in less than 10% horizontal expansion of that structure.
(6) 
Agricultural activities.
(7) 
Plant nurseries.
(8) 
Parking lots constructed to existing grade.
(9) 
Temporary fairs and carnivals.
(10) 
Accessory uses for residential purposes.
(11) 
Private sportsmen's club activities.
(12) 
Athletic facilities.
(13) 
Orchards.
C. 
Any permitted use within the riparian buffer shall be conducted in a manner that will maintain the extent of the 100-year floodplain, improve or maintain stream stability, and preserve and protect the ecological function of the floodplain.
D. 
Waiver for Improvements to Existing Structures in Outer Buffers. The provisions of this Subsection 2 do not require any changes or improvements to be made to lawfully existing structures in buffers. However, when any improvement to an existing structure is proposed which results in 10% or greater horizontal expansion of that structure, the improvement may only be permitted by the granting of a waiver from the requirements of this chapter. In considering a waiver application, the Board of Supervisors shall determine whether the applicant has presented evidence of hardship in addition to the standards for waivers set forth in § 23-110 of this chapter.
E. 
Pre-Existing Lots or Parcels/Development in Outer Buffers. In the case of legally pre-existing lots (approved prior to the effective date of this chapter) where the usable area of a lot lies within an outer buffer area, the applicant may apply for a waiver from the Board of Supervisors in accordance with § 23-110 of this chapter. In considering a waiver application, the Board of Supervisors shall determine whether the applicant has presented evidence of hardship in addition to the standards for waivers set forth in § 23-110 of this chapter.
3. 
Minimum Management Requirements for Riparian Buffers.
A. 
Existing native vegetation shall be protected and maintained within the riparian buffer.
B. 
Whenever practicable, invasive vegetation shall be actively removed, and the riparian buffer shall be planted with native trees, shrubs and other vegetation to create a diverse native plant community appropriate to the intended ecological context of the site.
4. 
The riparian buffer shall be enforceable by the Township and shall be recorded in the Monroe County Recorder of Deeds office, so that it shall run with the land and limit the use of the property located therein. The buffer shall allow for the continued private ownership and shall count toward the minimum lot area required by zoning, unless otherwise specified in the Township Zoning Ordinance.[1]
[1]
Editor's Note: See Ch. 27 of this Code.
[Ord. No. 3-2023, 7/18/2023]
1. 
The green infrastructure and low impact development practices provided in the BMP Manual shall be utilized for all regulated activities wherever possible. Water volume controls shall be implemented using the Design Storm Method in Subsection 1A or the Simplified Method in Subsection 1B below. For regulated activities equal or less than one acre that do not require hydrologic routing to design the stormwater facilities, this chapter establishes no preference for either methodology; therefore, the applicant may select either methodology on the basis of economic considerations, the intrinsic limitations on applicability of the analytical procedures associated with each methodology and other factors.
A. 
The Design Storm Method (CG-1 in the BMP Manual) is applicable to any size of regulated activity. This method requires detailed modeling based on site conditions.
(1) 
Do not increase the post-development total runoff volume for all storms equal to or less that the two-year, twenty-four-hour duration precipitation.
(2) 
For modeling purposes:
(a) 
Existing non-forested pervious area must be considered meadow in good condition.
(b) 
A percentage of no less than 20% of existing impervious area, when present, shall be considered meadow in good condition in the model for existing conditions.
B. 
The Simplified Method (CG-2 in the BMP Manual) provided below is independent of site conditions and should be used if the Design Method is not followed. This method is not applicable to regulated activities greater than one acre or for projects that require hydrologic routing to design the stormwater facilities. For new impervious surfaces:
(1) 
Stormwater facilities shall capture at least two inches of runoff from all new impervious surfaces.
(2) 
At least the first one inch of runoff from new impervious surfaces shall be permanently removed from the runoff flow, i.e., it shall not be released into the surface waters of this commonwealth. Removal options include reuse, evaporation, transpiration, and infiltration.
(3) 
Wherever possible, infiltration facilities should be designed to accommodate infiltration of the entire permanently removed runoff; however, in all cases at least the first 0.5 inch of the permanently removed runoff should be infiltrated.
[Ord. No. 3-2023, 7/18/2023]
1. 
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 as specified on the Brodhead-McMichaels Creek Stormwater Management District Watershed Map (Appendix D[1]) and Table 23-305.1. Areas located outside of the Brodhead-McMichaels Creek Watershed are subject to the same requirements as if they were located in Stormwater Management District A.
Table 23-305.1 - Rate Control Requirements
District
Proposed conditions 24-hour storm event
(reduce to)
Existing conditions 24-hour storm event
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
Due to the effect of the Leavitt Branch Dam, detention of storms less than the 50-year are not required in District B-3.
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 § 23-305, Subsection 7, of this chapter and is shown by the qualified 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 volume control, § 23-304 of this chapter. 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 for the specified design storms.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
2. 
District Boundaries. The boundaries of the stormwater management districts are shown on an official map included in Appendix D[2] of the Brodhead Creek and McMichael Creek Act 167 Stormwater Management Plan, available at the Monroe County Conservation District website. A copy of the official map at a reduced scale is included in Appendix D of this chapter. 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 SWM site plan.
[2]
Editor’s Note: Said appendix is included as an attachment to this chapter.
3. 
Sites Located in More Than One District. If a development site is 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. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea. The Board of Supervisors may grant a waiver if discharges from multiple subareas recombine in proximity to the development site. In this case, peak discharge in any direction may be a 100% release rate, provided that the overall site discharge meets the weighted average release rate.
4. 
Off-Site Areas. Off-site areas that drain through a 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.
5. 
Where the development site area differs significantly from the total property 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.
6. 
"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 applicable Act 167 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 Subsection 7 to determine if adequate hydraulic capacity exists. The applicant shall submit this evaluation of the impacts due to increased downstream stormwater flows in the watershed to the Township.
A. 
The hydrologic regime of the site must be maintained.
B. 
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 Township.
C. 
The evaluation shall continue downstream until the increase in flow diminishes due to additional flow from tributaries and/or stream attenuation.
D. 
The peak flow values to be used for downstream areas for the design return period storms (two-, five-, ten-, twenty-five-, fifty-, and 100-year) for the twenty-four-hour storm event shall be the values from the calibrated models in the original Act 167 plans for the Brodhead Creek Watershed and the McMichaels Creek Watershed.
E. 
Proposed BMPs 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 Subsection 6H.
F. 
A financial distress shall not constitute grounds for the Township to approve the use of the "no-harm" option.
G. 
Downstream capacity improvements may be provided as necessary to achieve the "no harm" option.
H. 
Any "no harm" justifications shall be submitted by the applicant as part of the SWM site plan submission per Part 4 of this chapter.
7. 
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:
A. 
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.
B. 
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.
C. 
Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area must be designed in accordance with 25 Pa. Code Chapter 105 (if applicable) and, at minimum, pass the increased twenty-five-year return period runoff.
8. 
Hardship Option. The applicable Act 167 plan and its standards and criteria are designed to maintain existing conditions peak flows and volumes throughout the 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 Township to approve the use of the hardship option. The applicant would have to plead its case to the Board of Supervisors with the final determination made by the Township. Any applicants pleading the "hardship option" will assume all liabilities that may arise due to exercising this option.
[Ord. No. 3-2023, 7/18/2023]
1. 
Stormwater runoff from all development sites shall be calculated using a generally accepted calculation technique that is based on the NRCS Soil Cover Complex Method. Table 23-306-1 summarizes acceptable computation methods, and the method selected by the qualified professional shall be based on the individual limitations and suitability of each method for a particular development site. The Township may allow the use of the Rational Method and Modified Rational Method after consultation with the Township Engineer to estimate peak discharges from drainage areas less than one acre and/or on a case-by-case basis.
Table 23-306-1 Acceptable Computation Methodologies for Stormwater Management Plans
Method
Method Developed By
Applicability
TR-20
USDA NRCS
Applicable where use of full hydrology computer model is desirable or necessary
TR-55
USDA NRCS
Applicable for land development plans with limitations described in TR55
HEC-1/HEC-HMS
US Army Corps of Engineers
Applicable where use of full hydrology 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
Modified Rational Method
Method to be approved by the Township Engineer
For drainage areas less than one acre and/or as approved by the Township or Township Engineer
Rational Method
Emil Kuichling
For collection and conveyance system design as approved by the Township and/or Township Engineer
Other Methods
Varies
Other computation methodologies approved by the Township and/or Township Engineer
2. 
All calculations using the Soil Cover Complex Method shall use the appropriate design rainfall depths for the various return period storms consistent with 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's Atlas 14 can be accessed at http://hdsc.nws.noaa.gov/hdsc/pfds. 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 of Appendix B[1] shall be used for the rainfall distribution.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
3. 
All calculations using the Rational Method or the Modified Rational Method shall use rainfall intensities consistent with appropriate times of concentration for overland flow and return periods 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's Atlas 14 can be accessed at http://hdsc.nws.noaa.gov/hdsc/pfds.
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.
5. 
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. Due to limitations of The TR-55 methodology, a minimum weighted curve number (CN) of 40 shall be utilized in the calculations.
6. 
Runoff coefficients (c) for both existing and proposed conditions for use in the Rational Method or Modified Rational Method shall be obtained from Table B-3 in Appendix B.
7. 
The qualified professional shall consider that the runoff from the development site graded to the subsoil will not have the same runoff conditions as the site under existing conditions, even after placement of topsoil or seeding. The qualified professional may adjust the proposed condition "CN" or "c" to better reflect proposed soil conditions.
8. 
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.[2]
[2]
Editor's Note: Said appendix is included as an attachment to this chapter.
9. 
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.
10. 
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. The design storm hydrograph shall be computed using a generally accepted calculation technique that is based on the NRCS Soil Cover Complex Method. The Township 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.