Township of Franklin, PA
Chester County
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Table of Contents
Table of Contents
[Ord. 2013-04, 12/18/2013, § 301]
1. 
Applicants proposing regulated activities in the municipality which are not exempt under § 19-106 shall submit a stormwater management site plan (SWM site plan) to the municipality for review and approval in accordance with Parts 3 and 4. SWM site plans approved by the municipality shall be on site throughout the duration of the regulated activity.
2. 
The stormwater management and runoff control criteria and standards in this chapter shall apply to the total proposed regulated activity, even if it is to take place in stages. The measurement of impervious surfaces shall include all of the impervious surfaces in the total proposed regulated activity even if the development is to take place in stages.
3. 
No regulated activity within the municipality shall commence until:
A. 
The municipality issues approval of a SWM site plan, which demonstrates compliance with the requirements of this chapter.
B. 
The applicant has received a letter of adequacy or approval for the erosion and sediment control plan review by the municipality and the Conservation District (if required), and has received all other local, state and federal permit approvals required for the project involving the regulated activity.
4. 
Neither submission of an SWM site plan under the provisions herein nor compliance with the provisions of this chapter shall relieve any person from responsibility for damage to any person or property otherwise imposed by law.
5. 
The applicant shall design the site to minimize disturbances to land, site hydrology, and natural resources, and to maintain the natural hydrologic regime, drainage patterns and flow conditions. The applicant shall apply the procedures set forth in § 19-304 for the overall site design and for selection, location and design of features and BMPs to be used to comply with the requirements of this chapter.
6. 
To the maximum extent practicable, post-construction stormwater shall be discharged within the drainage area of the same stream or water body receiving the runoff prior to construction of the proposed regulated activity.
7. 
Existing drainage peak rate discharges up to and including the one-hundred-year storm onto or through adjacent property(ies) or downgradient property(ies), including diffuse drainage discharge, shall not be altered in any manner without written permission from, and, where applicable as determined by the municipality an easement and agreement with, the affected landowner(s) for conveyance of discharges onto or through their property(ies). Such discharge shall be subject to any applicable discharge criteria specified in this chapter.
8. 
Areas located outside of the site (i.e., areas outside of the regulated activity) that drain through a proposed site are not subject to water quality and volume control, infiltration, stream channel protection, or peak flow rate control requirements (as presented in §§ 19-30519-308). Drainage facilities located on the site shall be designed to safely convey flows from outside of the site through the site.
9. 
If site conditions preclude capture of runoff from limited portions of the disturbed area for achieving water quality volume control standards, stream channel protection standards, and the two-year storm event peak runoff rate reduction standards for new development required by this chapter, the applicant shall propose alternate methods to mitigate the bypass of the BMPs, subject to the approval of the Municipal Engineer. In no case shall resulting peak rate be greater than the pre-development peak rate for the equivalent design storm.
10. 
For all regulated activities, erosion and sediment control BMPs shall be designed, implemented, operated, and maintained during the regulated activities (i.e., during construction) as required to meet the purposes and requirements of this chapter, to meet the erosion and sediment control requirements of the municipality, if applicable, and to meet all requirements under 25 Pa.Code and the Clean Streams Law.
11. 
For all regulated activities, permanent BMPs and conveyances shall be designed, implemented, operated, and maintained to meet the purposes and requirements of this chapter and to meet all requirements under 25 Pa.Code, the Clean Streams Law, and the Storm Water Management Act.
12. 
The design of all BMPs and conveyances shall incorporate sound engineering principles and practices in a manner that does not aggravate existing stormwater problems as identified by the municipality. The municipality reserves the right to disapprove any design that would result in construction in an area affected by existing stormwater problem(s) or continuation of an existing stormwater problem(s).
13. 
Existing wetlands, either on the site or on an adjacent property, shall not be used to meet the minimum design requirements for stormwater management or stormwater runoff quality treatment. Stormwater discharges to existing wetlands shall not degrade the quality or hydrologic integrity of the wetland.
14. 
Hotspots Runoff Controls. Specific structural or pollution prevention practices may be required, as determined to be necessary by the Municipal Engineer, to pretreat runoff from hotspots prior to infiltration. Following is a list of examples of hotspots:
A. 
Vehicle salvage yards and recycling facilities.
B. 
Vehicle fueling stations.
C. 
Vehicle service and maintenance facilities.
D. 
Vehicle and equipment cleaning facilities.
E. 
Fleet storage areas (bus, truck, etc.).
F. 
Industrial sites based on Standard Industrial Classification Codes.
G. 
Marinas (service and maintenance areas.).
H. 
Outdoor liquid container storage.
I. 
Outdoor loading/unloading facilities.
J. 
Public works storage areas.
K. 
Facilities that generate or store hazardous materials.
L. 
Commercial container nursery.
M. 
Contaminated sites/brownfields.
N. 
Other land uses and activities as designated by the municipality.
15. 
Contaminated and Brownfield Sites. Where BMPs may contribute to the migration of contaminants in groundwater, the water quality and runoff volume, stream channel protection, and peak rate control standards shall be met; however, at the Municipal Engineer's discretion, the minimum infiltration requirement may be reduced or eliminated commensurate with the contaminated area and the required water quality and runoff control measures may be increased to mitigate the reduced infiltration requirement for the contaminated area.
16. 
Additional Water Quality Requirements. The municipality may require additional stormwater control measures for stormwater discharges to special management areas including, but not limited to:
A. 
Water bodies listed as "impaired" by PADEP.
B. 
Any water body or watershed with an approved total maximum daily load (TMDL).
C. 
Areas of known existing flooding problems.
D. 
Critical areas with sensitive resources (e.g., state designated special protection waters, cold water fisheries, carbonate geology or other groundwater recharge areas that may be highly vulnerable to contamination, drainage areas to water supply reservoirs, etc.).
17. 
Applicants shall utilize the Pennsylvania Stormwater Best Management Practices Manual (PA BMP Manual), as amended, or other sources acceptable to the Municipal Engineer, for testing and design standards for BMPs, and where there is a conflict with the provisions of this chapter, the most restrictive applies.
18. 
For areas underlain by karst or carbonate geology that may be susceptible to the formation of sinkholes and other karst features, the location, type, and design of infiltration BMPs shall be based on a site evaluation conducted by a qualified licensed professional and based on the PA BMP Manual or other design guidance acceptable to the Municipal Engineer.
19. 
All regulated activities located within a Special Flood Hazard Area designated by the Federal Emergency Management Agency (FEMA) shall comply with Chapter 27, Part 13 of the Franklin Township Code of Ordinances, as amended, and shall be designed to maintain the flood carrying capacity of the floodway such that the base flood elevations are not increased, either upstream or downstream. The natural conveyance characteristics of the site and the receiving floodplain shall be incorporated into the stormwater management practices proposed for the site.
20. 
Disturbance of existing ground cover during construction of the proposed regulated activity is prohibited within 50 feet of top-of-bank of all perennial and intermittent waterways, water bodies (lakes, ponds, etc.) and wetlands, except for activities otherwise approved by state or local agencies (e.g. stream restoration projects, road crossings, subsurface utility projects etc.). At the Municipal Engineer's discretion and with Conservation District and PADEP approval where necessary, the non-disturbance buffer may be reduced because of setback or other site constraints, but never be less than 10 feet.
[Ord. 2013-04, 12/18/2013, § 302]
1. 
The following permit or other regulatory requirements may apply to certain regulated activities and shall be met prior to (or as a condition of) final approval by the municipality of the SWM site plan and prior to commencement of any regulated activities, as applicable.
A. 
All regulated activities subject to permit or regulatory requirements by PADEP under regulations at 25 Pa.Code, Chapter 102, or erosion and sediment control requirements of the municipality.
B. 
Work within natural drainage ways subject to permit by PADEP under 25 Pa.Code, Chapter 105.
C. 
Any BMP or conveyance that would be located in or adjacent to surface waters of the commonwealth, including wetlands, subject to permit by PADEP under 25 Pa.Code, Chapter 105.
D. 
Any BMP or conveyance that would be located on or discharge to a state highway right-of-way, or require access to or from a state highway and be subject to approval by PennDOT.
E. 
Culverts, bridges, storm sewers, or any other facilities which must pass or convey flows from the tributary area and any facility which may constitute a dam subject to permit by PADEP under 25 Pa.Code, Chapter 105.
[Ord. 2013-04, 12/18/2013, § 303]
1. 
No regulated activity within the municipality shall commence until:
A. 
The municipality receives documentation that the applicant has received:
(1) 
A "letter of adequacy" from the Conservation District or other approval from PADEP in compliance with 25 Pa.Code, Chapter 102, of an erosion and sediment control plan for construction activities, if applicable.
(2) 
A PADEP NPDES construction activities permit as required under 25 Pa.Code, Chapter 92.a, if applicable.
(3) 
Evidence of any other permit(s) or approvals required for the regulated activities.
B. 
An erosion and sediment control Plan has been approved by the municipality, if required.
2. 
A copy of the erosion and sediment control plan and any required permit(s), as required by PADEP regulations, shall be available on the site at all times.
3. 
Additional erosion and sediment control measures shall be applied where infiltration BMPs are proposed, at a minimum including those required in § 19-306, Subsection 1M.
[Ord. 2013-04, 12/18/2013, § 304]
1. 
The applicant shall design the site to minimize the disturbances to land, site hydrology, and natural resources, and to maintain the natural hydrologic regime, drainage patterns and flow conditions. The applicant shall demonstrate in its SWM site plan (as required in § 19-402, Subsection 2C) that the design sequence, objectives and techniques described below were applied to the maximum extent practicable in the site design of the regulated activity while complying with all other requirements of this chapter. The site design shall:
A. 
First, identify and delineate all existing natural resources and natural and man-made hydrologic features listed in § 19-402, Subsection 2B(8), that are located within the site, or receive discharge from, or may be impacted by the proposed regulated activity.
B. 
Second, provide a prioritized listing of these resources and features to identify:
(1) 
Those to be incorporated into the site design in a manner that provides protection from any disturbance or impact from the proposed regulated activity.
(2) 
Those to be protected from further disturbance or impact but for which the proposed regulated activity will provide improvement to existing conditions.
(3) 
Those that can be incorporated into and utilized as components of the overall site design in a manner that protects or improves their existing conditions while utilizing their hydrologic function within the limits of their available capacity (e.g., for infiltration, evapotranspiration, or reducing pollutant loads, runoff volume or peak discharge rates, etc.) to reduce the need for or size of constructed BMPs.
(4) 
Those that may be considered for alteration, disturbance or removal.
C. 
Third, develop the site design to achieve the following:
(1) 
Recognize and incorporate the priorities identified in Subsection 1B as the basis for the proposed site layout, grading, construction, and permanent ground cover design.
(2) 
Minimize earth disturbance (both surface and subsurface.)
(3) 
Maximize protection of or improvement to natural resources and special management areas.
(4) 
Minimize the disturbance of natural site hydrology, in particular natural drainage features and patterns, discharge points and flow characteristics, natural infiltration patterns and characteristics, and natural channel and floodplain conveyance capacity.
(5) 
Incorporate natural hydrologic features and functions identified in Subsection 1B into the site design to protect and utilize those features and their hydrologic functions to reduce the need for or size of constructed BMPs.
(6) 
Maximize infiltration and the use of natural site infiltration features, patterns and conditions, and evapotranspiration features.
(7) 
Apply selective grading design methods to provide final grading patterns or preserve existing topography in order to evenly distribute runoff and minimize concentrated flows.
(8) 
Minimize the cumulative area to be covered by impervious surfaces and:
(a) 
Minimize the size of individual impervious surfaces.
(b) 
Separate large impervious surfaces into smaller components.
(c) 
Disconnect runoff from one impervious surface to another.
(d) 
Utilize porous materials in place of impervious wherever practicable.
(9) 
Minimize the volume and peak discharge rates of stormwater generated.
(10) 
Avoid or minimize stormwater runoff pollutant loads and receiving stream channel erosion.
(11) 
Locate infiltration and other BMPs.
(a) 
At or as near to the source of generation as possible.
(b) 
At depths that are as shallow as possible.
(12) 
Prioritize the selection and design of BMPs as follows:
(a) 
Nonstructural and vegetation BMPs, then.
(b) 
Structural (surface and subsurface) BMPs.
(13) 
For flow volumes requiring conveyance from the source of generation to a BMP for management, give preference to open channel conveyance techniques that provide infiltration and water quality benefits, and landscaped-based management in common open space areas, where practicable.
(14) 
Consider additional guidance for incorporating natural hydrology into the site and BMP designs, methods and techniques that support the objectives of Subsection 1B and C. Appendix 19-B presents additional discussion of natural hydrology site design and sources of information for "Conservation Design," "Low Impact Design," and "Sustainable Design."
D. 
The procedures set forth above shall be utilized to the maximum extent practicable for the overall site design and selection, location and design of features and BMPs to be used to comply with the requirements of §§ 19-30519-308.
[Ord. 2013-04, 12/18/2013, § 307]
1. 
To control post-construction stormwater impacts from regulated activities and meet state water quality requirements, BMPs shall be provided in the site design that replicate predevelopment stormwater infiltration and runoff conditions, such that post-construction stormwater discharges do not degrade the physical, chemical, or biological characteristics of the receiving waters. The applicant shall comply with the following water quality and runoff volume requirements for all regulated activities, including all new development and redevelopment activities:
A. 
The post-construction total runoff volume shall not exceed the predevelopment total runoff volume for all storms equal to or less than the two-year, twenty-four-hour duration precipitation (design storm). The water quality and runoff volume to be managed shall consist of any runoff volume generated by the proposed regulated activity over and above the predevelopment total runoff volume and shall be captured and permanently retained or infiltrated on the site. Permanent retention options may include, but are not limited to, reuse, evaporation, transpiration, and infiltration.
B. 
For modeling purposes, the predevelopment ground cover conditions shall be determined using the corresponding ground cover assumptions presented in § 19-309, Subsection 4, of this chapter.
C. 
The design of the facility outlet shall provide for protection from clogging and unwanted sedimentation.
D. 
BMPs that moderate the temperature of stormwater shall be used to protect the temperature of receiving waters.
E. 
Water quality improvement shall be achieved in conjunction with achieving the infiltration requirements of § 19-306. The infiltration volume required under § 19-306 may be included as a component of the water quality volume. If the calculated water quality and runoff volume is greater than the volume infiltrated, then the difference between the two volumes shall be managed for water quality and runoff volume control through other techniques or practices but shall not be discharged from the site.
F. 
Runoff from the disturbed area shall be treated for water quality prior to entering existing waterways or water bodies. If a stormwater management practice does not provide water quality treatment, then water quality BMPs shall be utilized to provide pre-treatment prior to the runoff entering the stormwater management practice.
G. 
The municipality may require additional water quality and runoff control measures for stormwater discharging to special management areas such as those listed in § 19-301, Subsection 16.
H. 
When the regulated activity contains or is divided by multiple drainage areas, the water quality and runoff volume shall be separately addressed for each drainage area.
I. 
Weighted averaging of runoff coefficients shall not be used for manual computations or input data for water quality and runoff volume calculations.
J. 
Areas located outside of the site (i.e., areas outside of the regulated activity) may be excluded from the calculation of the water quality and runoff volume requirements.
K. 
Water quality and volume control practices shall be selected and designed to meet the criteria of § 19-304, Subsection 1C, that apply to water quality and volume control.
[Ord. 2013-04, 12/18/2013, § 306]
1. 
Providing for infiltration consistent with the natural hydrologic regime is required to compensate for the reduction in the recharge that occurs when the ground surface is disturbed or impervious surface is created or expanded. The applicant shall achieve the following infiltration requirements:
A. 
Wherever possible, infiltration should be designed to accommodate the entire water quality and runoff volume required in § 19-305.
B. 
For regulated activities involving new development, the volume of a minimum of one inch of runoff from all proposed impervious surfaces shall be infiltrated.
C. 
For regulated activities involving redevelopment, whichever is less of the following volume options shall be infiltrated:
(1) 
The volume of a minimum of one inch of runoff from all proposed impervious surfaces.
(2) 
The total water quality and runoff volume required in § 19-305 of this chapter.
D. 
If the requirements of Subsection 1B or C cannot be physically accomplished, then the applicant shall be responsible for demonstrating with data or calculations to the satisfaction of the Municipal Engineer why this infiltration volume cannot be physically accomplished on the site (e.g., shallow depth to bedrock or limiting zone, open voids, steep slopes, etc.) and what alternative volume can be infiltrated; however in all cases at least 1/2 inch of runoff volume shall be infiltrated.
E. 
Only if a minimum of at least 1/2 inch infiltration requirement cannot be physically accomplished on the site, shall a waiver from § 19-306 be considered by the municipality.
F. 
If site conditions preclude capture of runoff from portions of the impervious surfaces, the infiltration volume for the remaining area shall be increased an equivalent amount to offset the loss.
G. 
When a project contains or is divided by multiple watersheds, the infiltration volume shall be separately addressed for each watershed.
H. 
Existing impervious surfaces located in areas outside of the site (i.e., outside of the regulated activity) may be excluded from the calculation of the required infiltration volume.
I. 
A detailed soils evaluation of the site shall be conducted by a qualified professional and at a minimum shall address soil permeability, depth to bedrock, and subgrade stability. The general process for designing the infiltration BMP shall be conducted by a qualified licensed professional and shall be consistent with the PA BMP Manual (as amended) (or other guidance acceptable to the Municipal Engineer) and in general shall:
(1) 
Analyze hydrologic soil groups as well as natural and man-made features within the site to determine general areas of suitability for infiltration practices. In areas where development on fill material is under consideration, conduct geotechnical investigations of sub-grade stability; infiltration may not be ruled out without conducting these tests.
(2) 
Provide field tests such as double ring infiltrometer or other hydraulic conductivity tests (at the elevation of the proposed infiltration surface) to determine the appropriate hydraulic conductivity rate. Standard septic/sewage percolation tests are not acceptable for design purposes.
(3) 
Design the infiltration facility for the required retention (infiltration) volume based on field-determined infiltration capacity (and apply safety factor as per applicable design guidelines) at the elevation of the proposed infiltration surface.
(4) 
On-lot infiltration features are encouraged; however, it shall be demonstrated to the Municipal Engineer that the soils are conducive to infiltration on the identified lots.
J. 
Infiltration BMPs shall be selected based on suitability of soils and site conditions and shall be constructed on soils that have the following characteristics:
(1) 
A minimum depth of 24 inches between the bottom of the BMP and the top of the limiting zone. Additional depth may be required in areas underlain by karst or carbonate geology (see Subsection 1N).
(2) 
An infiltration rate sufficient to accept the additional stormwater volume and drain completely as determined by field tests conducted by the applicant.
(3) 
The infiltration facility shall completely drain the retention (infiltration) volume within three days (72 hours) from the end of the design storm.
K. 
All infiltration practices shall:
(1) 
Be selected and designed to meet the criteria of § 19-304, Subsection 1C, that are applicable to infiltration.
(2) 
Be set back at least 25 feet from all buildings and features with subgrade elements (e.g., basements, foundation walls, etc.), unless otherwise approved by the Municipal Engineer.
(3) 
For any infiltration practice that collects runoff from shared or multiple features and that is located within 50 feet of a building or feature with sub-grade elements (e.g., basements, foundation walls, etc.), the bottom elevation shall be set below the elevation of the sub-grade element.
L. 
Infiltration facilities shall, to the maximum extent practicable, be located to avoid introducing contaminants to groundwater:
(1) 
When a hotspot is located in the area draining to a proposed infiltration facility, an evaluation of the potential of groundwater contamination from the proposed infiltration facility shall be performed, including a hydrogeologic investigation (if necessary) by a qualified licensed professional to determine what, if any, pretreatment or additional design considerations are needed to protect groundwater quality.
(2) 
When located within a "well head protection area" of a public water supply well, infiltration practices shall be in conformance with the applicable approved source water protection assessment or source water protection plan.
(3) 
The applicant shall provide appropriate safeguards against groundwater contamination for land uses that may cause groundwater contamination should there be a mishap or spill.
M. 
During site construction, all infiltration practice components shall be protected from compaction due to heavy equipment operation or storage of fill or construction material. Infiltration areas shall also be protected from sedimentation. Areas that are accidentally compacted or graded shall be remediated to restore soil composition and porosity. Adequate documentation to this effect shall be submitted to the Municipal Engineer for review. All areas designated for infiltration shall not receive runoff until the contributory drainage area has achieved final stabilization.
N. 
Where sediment transport in the stormwater runoff is anticipated to reach the infiltration system, appropriate permanent measures to prevent or collect sediment shall be installed prior to discharge to the infiltration system.
O. 
Where roof drains are designed to discharge to infiltration practices, they shall have appropriate measures to prevent clogging by unwanted debris (for example, silt, leaves and vegetation). Such measures shall include but are not limited to leaf traps, gutter guards and cleanouts.
P. 
All infiltration practices shall have appropriate positive overflow controls.
Q. 
No sand, salt or other particulate matter may be applied to a porous surface material for winter ice conditions.
R. 
The following procedures and materials shall be required during the construction of all subsurface facilities:
(1) 
Excavation for the infiltration facility shall be performed with equipment that will not compact the bottom of the seepage bed/trench or like facility.
(2) 
The bottom of the bed and/or trench shall be scarified prior to the placement of aggregate.
(3) 
Only clean aggregate with documented porosity, free of fines, shall be allowed.
(4) 
The tops, bottoms and sides of all seepage beds, trenches, or like facilities shall be covered with drainage fabric. Fabric shall be non-woven fabric acceptable to the Municipal Engineer.
(5) 
Stormwater shall be distributed throughout the entire seepage bed/trench or like facility and provisions for the collection of debris shall be provided in all facilities.
[Ord. 2013-04, 12/18/2013, § 307]
1. 
For regulated activities involving new development with one or more acres of earth disturbance, the applicant shall comply with the following stream channel protection requirements to minimize stream channel erosion and associated water quality impacts to the receiving waters:
A. 
The peak flow rate of the post-construction two-year, twenty-four-hour design storm shall be reduced to the predevelopment peak flow rate of the one-year, twenty-four-hour duration precipitation, using the SCS Type II distribution.
B. 
To the maximum extent practicable, and unless otherwise approved by the Municipal Engineer, the post-construction one-year, twenty-four-hour storm flow shall be detained for a minimum of 24 hours and a maximum not to exceed 72 hours from a point in time when the maximum volume of water from the one-year, twenty-four-hour storm is stored in a proposed BMP (i.e., when the maximum water surface elevation is achieved in the facility). Release of water can begin at the start of the storm (i.e., the invert of the orifice is at the invert of the proposed BMP).
C. 
For modeling purposes, the predevelopment ground cover conditions shall be determined using the corresponding ground cover assumptions presented in § 19-309, Subsection 4, of this chapter.
D. 
The minimum orifice size in the outlet structure to the BMP shall be three inches in diameter unless otherwise approved by the Municipal Engineer, and a trash rack shall be installed to prevent clogging. For sites with small drainage areas contributing to the BMP that do not provide enough runoff volume to allow a twenty-four-hour attenuation with the three-inch orifice, the calculations shall be submitted showing this condition.
E. 
When the calculated orifice size is below three inches, gravel filters (or other methods) are recommended to discharge low-flow rates subject to the Municipal Engineer's satisfaction. When filters are utilized, maintenance provisions shall be provided to ensure filters meet the design function.
F. 
All proposed stormwater facilities shall make use of measures to extend the flow path and increase the travel time of flows in the facility.
G. 
When a regulated activity contains or is divided by multiple drainage areas, the peak flow rate control shall be separately addressed for each drainage area.
[Ord. 2013-04, 12/18/2013, § 308]
1. 
The applicant shall comply with the following peak flow rate control requirements for all regulated activities including those that involve new development and redevelopment.
A. 
Post-construction peak flow rates from any regulated activity shall not exceed the predevelopment peak flow rates as shown for each of the design storms specified in Table 19-308.1.
Table 19-308.1
Peak Rate Control Standards
(Peak Flow Rate of the Post-construction Design Storm Shall be Reduced to the Peak Flow Rate of the Corresponding Pre-development Design Storm Shown in the Table)
Pre-Development Design Storm
Post-Construction Design Storm Frequency
(24-Hour Duration)
New Development Regulated Activities
Redevelopment Regulated Activities
2-Year
1-Year
2-Year
5-Year
5-Year
5-Year
10-Year
10-Year
10-Year
25-Year
25-Year
25-Year
50-Year
50-Year
50-Year
100-Year
100-Year
100-Year
B. 
For modeling purposes, the pre-development ground cover conditions shall be determined using the corresponding ground cover assumptions presented in § 19-309, Subsection 4, of this chapter.
C. 
For regulated activities involving only redevelopment, no peak flow rate controls are required when and only if the total proposed impervious surface area is at least 20% less than the total existing impervious surface area to be disturbed by the regulated activity. In all cases where this requirement is not met, the redevelopment regulated activity shall achieve the peak flow rate controls presented in Table 19-308.1, using the redevelopment ground cover assumptions presented in § 19-309, Subsection 4.
D. 
Only the area of the proposed regulated activity shall be subject to the peak flow rate control standards of this chapter. Undisturbed areas for which the discharge point has not changed are not subject to the peak flow rate control standards.
E. 
Areas located outside of the site (i.e., areas outside of the regulated activity) that drain through a proposed site are not subject to peak flow rate control requirements. Drainage facilities located on the site shall be designed to safely convey flows from outside of the site through the site.
F. 
When a regulated activity contains or is divided by multiple drainage areas, the peak flow rate controls shall be separately addressed for each drainage area.
G. 
The effect of structural and non-structural stormwater management practices implemented as part of the overall site design may be taken into consideration when calculating total storage volume and peak flow rates.
[Ord. 2013-04, 12/18/2013, § 309]
1. 
Stormwater runoff from all regulated activity sites with a drainage area of greater than five acres shall be calculated using a generally accepted calculation technique(s) that is based on the NRCS Soil Cover Complex Method. Table 19-309.1 summarizes acceptable computation methods. The method selected for use shall be based on the individual limitations and suitability of each method for a particular site. The use of the rational method to estimate peak discharges for drainage areas greater than five acres shall be permitted only upon approval by the Municipal Engineer.
Table 19-309.1
Acceptable Computation Methodologies for SWM Site Plan
Method
Developed by
Applicability
TR-20 (or commercial computer package based on TR-20)
USDA NRCS
Applicable where use of full hydrology computer models desirable or necessary
TR-55 (or commercial computer package based on TR-55)
USDA NRCS
Applicable for land development plans where limitations described in TR-55 are met
HEC-1/HEC-HMS
US Army Corps of Engineers
Applicable where use of a full hydrologic computer model is desirable or necessary
Rational Method (or commercial computer package based on Rational Method)
Emil Kuichling (1889)
For sites up to 5 acres, or as approved by the municipality
Other Methods
Varies
Other computation methodologies approved by the municipality
2. 
All calculations using the Soil Cover Complex Method shall use the appropriate design rainfall depths for the various return period storms consistent with this chapter. Rainfall depths used shall be obtained from NOAA Atlas 14 values consistent with a partial duration series. When stormwater calculations are performed for routing procedures or infiltration, water quality and runoff volume functions, the duration of rainfall shall be 24 hours.
3. 
All calculations using the rational method shall use rainfall intensities consistent with appropriate times-of-concentration (duration) and storm events with rainfall intensities obtained from NOAA Atlas 14 partial duration series estimates, or the latest version of the PennDOT Drainage Manual (PDM Publication 584). Times-of concentration shall be calculated based on the methodology recommended in the respective model used. Times of concentration for channel and pipe flow shall be computed using manning's equation.
4. 
The applicant shall utilize the following ground cover assumptions for all predevelopment water quality and runoff volume, infiltration volume and peak flow rate calculations:
A. 
For regulated activities involving new development, the following ground cover assumptions shall be used:
(1) 
For areas that are woods, predevelopment calculations shall assume ground cover of "woods in good condition."
(2) 
For all other areas (including all impervious surfaces), predevelopment calculations shall assume ground cover of "meadow."
B. 
For regulated activities involving redevelopment, the following ground cover assumptions shall be used:
(1) 
For areas that are woods, predevelopment calculations shall assume ground cover of "woods in good condition."
(2) 
For areas that are not woods or not impervious surfaces, predevelopment calculations shall assume ground cover of "meadow."
(3) 
For areas that are impervious surfaces, predevelopment calculations shall assume at least 20% of the existing impervious surface area to be disturbed as "meadow" ground cover.
C. 
The applicant shall determine which stormwater standards apply to the proposed regulated activity as follows:
(1) 
Stormwater standards for new development shall apply to all proposed regulated activities that involve only new development activities as defined in this chapter.
(2) 
Stormwater standards for redevelopment shall apply to all proposed regulated activities that involve only redevelopment activities as defined in this chapter.
(3) 
At the discretion of the Municipal Engineer, regulated activities that involve a combination of both new development and redevelopment activities, as defined in this chapter, may either:
(a) 
Apply the stormwater standards (redevelopment or new development) that are associated with the activity that involves the greatest amount of land area.
(b) 
Apply the redevelopment and new development stormwater standards to the corresponding redevelopment and new development portions of the proposed regulated activity.
5. 
Runoff curve numbers (CN) for both predevelopment and proposed (post-construction) conditions to be used in the Soil Cover Complex Method shall be obtained from Table 19-C-1 in Appendix 19-C of this chapter.
6. 
Runoff coefficients (C) for both predevelopment and proposed (post-construction) conditions for use in the rational method shall be obtained from Table 19-C-2 in Appendix 19-C of this chapter.
7. 
Weighted averaging of runoff coefficients shall not be used for manual computations or input data for water quality and runoff volume calculations.
8. 
Hydraulic computations to determine the capacity of pipes, culverts, and storm sewers shall be consistent with methods and computations contained in the Federal Highway Administration Hydraulic Design Series Number 5 (Publication No. FHWA-NHI-01-020 HDS No. 5, as amended). Hydraulic computations to determine the capacity of open channels shall be consistent with methods and computations contained in the Federal Highway Administration Hydraulic Engineering Circular Number 15 (Publication No. FHWA-NHI-05-114 HEC 15, as amended). Values for Manning's roughness coefficient (n) shall be consistent with Table 19-C-3 in Appendix 19-C of this chapter.
9. 
Runoff calculations shall include the following assumptions:
A. 
Average antecedent moisture conditions (for the Soil Cover Complex Method only for example, TR-55, TR-20).
B. 
A type II distribution storm (for the Soil Cover Complex Method only for example, TR-55, TR-20).
[Ord. 2013-04, 12/18/2013, § 310]
1. 
Any BMP intended to hold standing water for four days or longer shall be designed to incorporate biologic controls consistent with the West Nile Guidance found in Appendix 19-D, PADEP Document 363-0300-001 "Design Criteria Wetlands Replacement/Monitoring" (as amended), (or contact the Pennsylvania State Cooperative Wetland Center or the Penn State Cooperative Extension Office for design information).
2. 
Any stormwater basin required or regulated by this chapter designed to store runoff and requiring a berm or earthen embankment shall be designed to provide an emergency spillway to safely convey flow up to and including the one-hundred-year proposed conditions. The height of embankment shall provide a minimum one foot of freeboard above the maximum pool elevation computed when the facility functions for the one-hundred-year proposed conditions inflow. Should any BMP require a dam safety permit under 25 Pa.Code, Chapter 105, regulations, the facility shall be designed in accordance with and meet the regulations of 25 Pa.Code, Chapter 105, concerning dam safety. PA 25 Pa.Code, Chapter 105, may require the safe conveyance of storms larger than one-hundred-year event.
3. 
Any drainage conveyance facility and/or channel not governed by 25 Pa.Code, Chapter 105, regulations shall be designed to convey, without damage to the drainage facility or roadway, runoff from the twenty-five-year storm event. Larger storm events fifty-year and one-hundred-year storms shall also be safely conveyed in the direction of natural flow without creating additional damage to any drainage facilities, nearby structures, or roadways.
4. 
Conveyance facilities to or exiting from stormwater management facilities (i.e., detention basins) shall be designed to convey the design flow to or from the facility.
5. 
Roadway crossings or structures located within designated floodplain areas shall be able to convey runoff from a one-hundred-year design storm consistent with Federal Emergency Management Agency, National Flood Insurance Program Floodplain Management Requirements.
6. 
Any facility located within a PennDOT right-of-way shall comply with PennDOT minimum design standards and permit submission and approval requirements.
7. 
Adequate erosion protection and energy dissipation shall be provided along all open channels and at all points of discharge. Design methods shall be consistent with the Federal Highway Administration Hydraulic Engineering Circular Number 11 (Publication No. FHWA-IP-89-016, as amended) and the PADEP Erosion and Sediment Pollution Control Program Manual (Publication No. 363-2134-008, as amended), or other design guidance acceptable to the Municipal Engineer.
[Ord. 2013-04, 12/18/2013, § 311]
1. 
The following provisions shall be followed and incorporated into the stormwater management design and construction process:
A. 
Stormwater management facilities, including, but not limited to, recharge facilities, detention facilities, storm sewers, culverts, bridges and related drainage installations shall be designed and constructed to meet the following purposes:
(1) 
To permit unimpeded flow of natural watercourses.
(2) 
To insure adequate drainage of all low points.
(3) 
To intercept stormwater runoff along streets at intervals reasonably related to the extent and grade of the area drained to prevent flow of stormwater across intersections.
(4) 
To insure adequate and unimpeded flow of stormwater over or under driveways.
(5) 
To prevent excessive flow on or across streets, sidewalks, drives, parking areas, and any other paved surface or access way.
(6) 
To lead stormwater away from springs.
B. 
All natural streams, channels, swales, drainage systems, and/or areas of concentration of surface water shall be maintained in their existing condition except as necessary for those uses that may be permitted by the municipality's Zoning Ordinance [Chapter 27] and as approved by the municipality.
C. 
Man-made structures shall be kept to a minimum.
D. 
Bridges, culverts, or riprap to be placed in or over a stream shall be chosen and constructed to maintain the natural characteristics of the stream and shall meet the approval of the municipality and must obtain necessary approvals from PADEP.
E. 
The municipality may require that a landowner or developer provide reasonable corrective measures to alleviate any existing off-site drainage problem that may be affected by the proposed land development or any other regulated activity.
F. 
No person shall deposit or place any debris or any other material whatsoever, or cause such to be thrown or placed, in any channel or stormwater facility in such a manner as to obstruct free flow.
G. 
No stormwater management facility shall create health, safety or sanitation problems.
H. 
No stormwater management facility shall impact the ability of on-lot sewage disposal systems to treat waste or adequately infiltrate treated wastewater effluent.
I. 
Various BMPs, both structural and non-structural, other than those listed in the following sections can be utilized in the stormwater design. Any BMP not addressed in this chapter shall be designed in accordance with the design parameters found in the PADEP BMP Manual, latest edition. Any design parameters found in the PADEP BMP Manual for the BMPs listed in the sections of this Part 3 below shall apply unless otherwise specified herein.
J. 
Reference to publications and source documents shall be deemed to include any amendments and revisions thereof.
K. 
Individual on-lot BMPs (serving only one residential lot) shall meet the design criteria of Appendix 19-A Simplified Approach for Stormwater Management for Small Projects and shall not be subject to §§ 19-312 and 19-313 unless deemed necessary by the municipality's Engineer based on design parameters.
[Ord. 2013-04, 12/18/2013, § 312]
1. 
General Requirements for All Types of Basins.
A. 
Basins shall meet the following minimum setbacks measured from the top and/or toe of slope (whichever is closer):
(1) 
Fifty feet from a special geologic feature as defined herein.
(2) 
Fifty feet from any property line.
(3) 
Fifty feet from any right-of-way.
(4) 
Fifty feet from any structure.
(5) 
Fifty feet from a wetland.
(6) 
Fifty feet from the top of bank of existing streams.
B. 
The use of multiple basin facilities that are smaller and less intrusive on the site is encouraged.
C. 
Privately owned basin facilities and BMPs shall be located entirely on one parcel unless otherwise permitted by the municipality.
D. 
Maintenance of a basin facility shall be the responsibility of the lot owner or, if the facility is located in a common area, the responsibility of the applicable homeowner's association. See Part 7.
E. 
When PADEP requires basin facilities to have a state permit, the developer shall submit all information to PADEP and obtain all necessary approvals and permits.
F. 
Easements shall be provided for all basins and shall meet the applicable requirements in § 19-704.
2. 
Design Requirements for All Types of Basins.
A. 
For basins that combine rate and volume controls, the infiltration "discharge" should not be taken into consideration when routing the peak discharge amounts, nor shall the infiltration volume be used in the routing.
B. 
It shall be the developer's responsibility to verify if the site is underlain by karst. Whenever basins will be located in an area underlain by karst:
(1) 
A geological evaluation of the proposed location shall be conducted to determine susceptibility to sinkhole formation.
(2) 
The design of all facilities over limestone formations shall include measures to prevent groundwater contamination and, where necessary, sinkhole formation.
(3) 
The installation of an impermeable liner may be required.
(4) 
A detailed hydrogeologic investigation may be required.
(5) 
Uses where a mishap or spill may cause groundwater contamination will require the developer to provide safeguards against contamination.
C. 
Inlet and outlet structures shall be located at maximum distances from one another. For above ground basins, a rock filter berm, rock-filled gabions, or other baffle may be required between inlet and outlet areas when the distance is deemed insufficient for water quality purposes.
D. 
A reinforced concrete outlet structure/box shall be used to regulate water flow through all basins and shall incorporate the following components and criteria:
(1) 
A multiple stage outlet release design is encouraged.
(2) 
The minimum circular orifice diameter for controlling discharge rates from basin facilities shall be three inches.
(3) 
The elevation of the top of the outlet structure shall be such that no flow enters the structure for the twenty-five-year frequency storm event.
(4) 
The base of the outlet structure shall extend a minimum of one foot below the bottom of the basin for above-ground basins.
(5) 
Outlet structure connections shall be water tight.
(6) 
The outlet structure shall be cast as one-piece.
(7) 
A concrete wash (flow channel) across the bottom of the structure shall be provided.
(8) 
Basins with a water depth less than or equal to 1.5 feet may be exempted from the outlet structure requirements as determined by the municipality.
E. 
A trash rack shall be provided for all above-ground orifices.
F. 
The outlet pipe shall have reinforced concrete pipe with rubber gaskets/O-ring joints.
G. 
Basins shall be designed to accommodate the one-hundred-year post-development storm such that the maximum water surface elevation is a minimum of six inches below:
(1) 
The emergency spillway elevation for above-ground basins.
(2) 
The top of facility for under-ground basins.
H. 
When the outfall point of a proposed basin facility is located at a point subject to tailwater conditions, a tailwater elevation at the outfall point will need to be assumed when performing the basin facility routing calculations. The tailwater elevation assumed shall be based on the same frequency of the storm being routed.
I. 
Any pipe or other component that discharges into an above-ground basin shall discharge at the bottom of the basin and shall be provided with an appropriate energy dissipater.
J. 
Any pipe or other component that discharges out of a basin shall be provided with an appropriate energy dissipater.
K. 
Where appropriate, adequate drainage channels shall be provided and maintained for discharge(s) from the basin. If the basin will not discharge to a suitable natural drainage channel, the developer may be required to provide facilities to safely and efficiently convey the discharge to a suitable drainage channel. Securing necessary drainage easements for this purpose shall be the sole responsibility of the developer.
3. 
Basins that are designed with berms/earthen embankments shall incorporate the following minimum standards:
A. 
The height of the berm shall not exceed 15 feet, unless all appropriate permits are issued by the PADEP and approved by the municipality.
B. 
The minimum top width of berms shall be 10 feet.
C. 
Side slopes of basins:
(1) 
Basin shape shall, whenever possible, be as shallow as possible and blend/conform to the natural topography.
(2) 
Shall not be steeper than four units horizontally to one unit vertically (4:1).
(3) 
May, depending upon the location and any other intended use of the detention facilities be required to have a side slope less steep than the maximum slope allowed under Subsection 3C(2) above for one or both slopes.
(4) 
When a basin is to be maintained by a residential lot owner, the side slope shall be four units horizontally to one unit vertically (4:1).
D. 
A key trench shall be provided:
(1) 
Extending at least two feet deep in undisturbed soil, or to stable subgrade whichever is deeper.
(2) 
Constructed of compacted relatively impervious material (Unified Soil Classification CL or ML).
(3) 
Having a minimum bottom width of four feet.
(4) 
Having maximum side slopes of one horizontal to one vertical.
E. 
A compacted impervious core shall be provided:
(1) 
Having at least eight feet wide at the top.
(2) 
Having a maximum side slope of one horizontal to one vertical.
(3) 
Extending for the full length of the embankment.
(4) 
Having the top elevation set at the fifty-year design water surface elevation.
F. 
All pipes and culverts through berms shall have properly spaced anti-seep collars incorporating the following requirements:
(1) 
Anti-seep collar connections shall be water tight.
(2) 
The number, spacing and size of anti-seep collars shall be designed using a method acceptable to the municipality's Engineer.
(3) 
Anti-seep collars shall be constructed of concrete, a minimum of one-foot thick.
G. 
Basin bottom grades shall be a minimum of 2% unless designed in combination with an infiltration facility or other BMP where bottom grade is not indicated or with the approval of the municipality's Engineer.
H. 
All basin embankments shall:
(1) 
Be constructed of suitable material.
(2) 
Be placed in eight-inch lifts, maximum.
(3) 
Compacted to a minimum of 95% of maximum dry density as established by ASTM D-1557.
(4) 
Have compaction operations be observed by the site inspector.
(a) 
When required by the municipality's Engineer, the developer shall perform compaction testing at the cost of the developer, by a qualified laboratory technician copies of all such compaction tests shall be provided and acceptable to the municipality's Engineer.
I. 
An emergency spillway shall be provided incorporating the following requirements:
(1) 
The emergency spillway shall be placed in undisturbed earth whenever possible.
(2) 
Emergency spillways shall be designed to safely convey the one-hundred-year post-development basin inflow with a minimum of six inches of freeboard above the water surface elevation to the top of berm, assuming blocked outlet structure conditions. The total minimum depth of emergency spillways shall be one foot.
(3) 
Emergency spillways shall be constructed such that the basin berm is protected against erosion. When necessary, erosion protection shall extend along the upstream and downstream berm slopes.
(4) 
Basins with a water depth less than or equal to 1 1/2 feet are exempt from emergency spillway and freeboard requirements unless otherwise deemed necessary by the municipality's Engineer.
J. 
When deemed necessary by the municipality, stormwater basin facilities shall be enclosed with a fence of a type, size, location and character acceptable to the municipality.
4. 
Under-ground basins shall incorporate the following minimum standards:
A. 
Flow through the outlet structure shall be attenuated with a concrete weir wall with appropriately sized orifices. Other designs will be considered with approval of the municipality.
B. 
Underground facilities that propose pipe storage as a means of detention shall be constructed of reinforced concrete pipe (RCP) or smooth-lined corrugated plastic pipe (SLCPP). No metal pipe shall be allowed.
5. 
Wet basins shall incorporate the following minimum standards:
A. 
Water surface area shall not exceed 1/10 of the tributary drainage area.
B. 
Bank protection shall be provided to prevent erosion.
C. 
Minimum normal water depth shall be four feet. If fish are to be used to keep the pond clean, a minimum of one-fourth of the pond area shall be a minimum of 10 feet deep.
D. 
Facilities shall be provided to allow the pond level to be lowered by gravity flow for cleaning purposes, and bank and other maintenance.
E. 
Aeration facilities shall be required as necessary to prevent pond stagnation. Manufacturer's information to substantiate the effectiveness of such aeration facilities shall be submitted with the site plans. Agreements for the perpetual operation and maintenance of aeration facilities shall be prepared and provided for review. See Part 7.
F. 
In the event that the water surface of the pond is to be raised for the purposes of storing water for irrigation or in anticipation of the evapotranspiration demands of dry weather, the volume remaining for storage of excess stormwater runoff shall be sufficient to contain the fifty-year design storm runoff.
G. 
All wet basin designs shall incorporate biological minimization controls consistent with the West Nile Guidance found in Appendix 19-D.
6. 
The following items shall be submitted for basin review:
A. 
Design computations for the sizing of the outlet structure.
B. 
Stage-storage curve.
C. 
Routed hydrographs for each storm.
D. 
Storage requirement calculations.
E. 
Plan(s) showing the berm/embankment and outlet structure in plan and cross-section views as well as details, including, but not limited to:
(1) 
Inlet pipe and energy dissipater.
(2) 
Top of berm elevations.
(3) 
Width of the top of the berm.
(4) 
Outlet pipe and energy dissipater.
(5) 
Side slopes.
(6) 
Emergency spillway elevation.
(7) 
Elevations of all features of the outlet structure.
(8) 
Clay core.
(9) 
Key trench.
(10) 
Dimensions and spacing of anti-seep collars.
(11) 
Trash rack.
(12) 
Anti-vortex device (if included in the design).
[Ord. 2013-04, 12/18/2013, § 313]
1. 
General.
A. 
Storm sewers and associated structures shall be required to be constructed to:
(1) 
Intercept runoff at such intervals as necessary along streets to provide safe vehicular movement.
(2) 
Eliminate standing water at the bottom of all grades regardless of location.
(3) 
Eliminate the use of cross gutters at street intersections and elsewhere, including in parking lots.
(4) 
Discharge collected water (from any and all locations including, but not limited to, streets, parking lots and lawn area) to an infiltration facility, detention basin or other acceptable BMP, that discharges to the nearest practical natural channel.
B. 
Manholes, inlets, headwalls and other stormwater structures must conform to the standards established by PennDOT and be per details shown in PennDOT Standards for Roadway Construction or as approved by the municipality's Engineer. Such structures must be supplied by a PennDOT Bulletin 15 approved supplier. These requirements shall be noted on the plan.
C. 
All materials, workmanship, and installation shall conform to PennDOT Specifications contained in Chapter 408, current edition.
D. 
Whenever practical, storm sewers and associated structures that drain the street system shall be located within the right-of-way of the street.
E. 
Easements shall be provided for all conveyance and collection systems that are not located within street rights-of-way and shall be a minimum of 20 feet in width. Easements shall meet the applicable requirements in § 19-704.
F. 
No conveyance shall be constructed within 50 feet of a unique geologic feature, except however that a conveyance constructed of reinforced concrete pipe utilizing rubber gasket/O-ring joints may be located 25 feet or more from such unique geologic feature.
G. 
Collection and conveyance systems shall be installed to prevent concentrated flow from crossing or following sidewalks. Pipe and inlet size and materials used for this purpose shall be acceptable to the municipality's Engineer.
H. 
Collection and conveyance systems shall be provided where runoff is concentrated in rear, side or front yards as necessary to prevent erosion.
I. 
Collection and conveyance systems shall be provided in order to adequately drain parking lots.
2. 
Sizing Criteria.
A. 
Collection and conveyance systems in public streets shall be adequate for the anticipated runoff when the area draining to the system is fully developed as permitted by zoning.
B. 
Collection and conveyance systems regardless of location shall be designed to carry the twenty-five-year peak flow rate determined using the Rational Method formula and good engineering practice.
C. 
The system shall be evaluated for both gravity (Manning's equation) and pressure (inlet/outlet control, hydraulic grade line) as appropriate.
D. 
Provisions must be made to transport the runoff from a one-hundred-year frequency storm to an appropriate stormwater management facility in a manner that does not damage property or flood streets.
3. 
Stormwater Pipes.
A. 
The minimum inside diameter of all pipe to be installed shall be not less than 15 inches. When cover is 25 feet or greater, the minimum inside diameter shall be 24 inches.
B. 
All pipes shall be reinforced concrete Class III or better meeting Penn-DOT's one-hundred-year life criteria.
C. 
Joints shall be provided with rubber gaskets/O-rings.
D. 
The minimum pipe slope shall be 1/2%.
E. 
The minimum cover of stormwater pipe shall be 24 inches. This minimum cover shall be provided and maintained during construction in order to protect pipe from damage.
F. 
Where cover is restricted, equivalent elliptical concrete pipe or concrete arch pipe maybe used in lieu of circular pipe.
G. 
When located within a street cartway, pipe shall be bedded on six inches of PennDOT 2A stone and backfilled with 2A stone placed and compacted in six-inch lifts.
H. 
All pipes shall be laid in a straight line. A manhole or inlet shall be provided at all horizontal deflections.
I. 
Storm pipe shall not be permitted under buildings or structures.
J. 
Underdrains and/or pavement base drains shall be:
(1) 
Required at all locations where subsurface water that could negatively impact the subgrade of a street is expected.
(2) 
Provided in areas deemed necessary by the municipality's Engineer as may be encountered during construction. A note to this effect shall be placed on the plan.
K. 
A water quality/pretreatment structure (or structures as necessary based on design flow) shall be:
(1) 
Provided at or near the terminus of all conveyance systems.
(2) 
Capable of capturing floatables, sediment, gravel, leaves and liquid contaminates prior to leaving the right-of-way and/or entering a channel or stormwater BMP whether an infiltration BMP or detention basin.
(3) 
Located such that they are easily accessible from the street, along a vehicular path to facilitate maintenance.
L. 
Prior to dedication of public streets and release of the maintenance bond:
(1) 
A video inspection of all collection and conveyance systems located within the street right-of-way shall be required using methods acceptable to the municipality's Engineer.
(2) 
A record of the video inspection shall be provided in an electronic format acceptable to the municipality's Engineer.
(3) 
Depending on the results of the video inspection, all pipes and inlets shall be cleaned and/or restored to design specifications.
4. 
Inlets.
A. 
Inlets shall be spaced to limit the gutter spread to no more than 1/2 of the width of the travel lane during a twenty-five-year design storm.
B. 
The capacity of all C, M, or S type inlets shall be determined using the Commonwealth of Pennsylvania, Department of Transportation, Design Manual, Part 2, "Highway Design."
C. 
The maximum allowable headwater depth shall be one-foot below the top of the inlet grate.
D. 
If double inlets are proposed, they shall be separated by a minimum of 20 feet.
E. 
Inlet capacity calculations shall be provided in the stormwater management report, including the design twenty-five-year peak flow rate to each inlet.
F. 
In non-sump areas, inlets shall be placed such that flow to any single inlet shall not exceed four cubic feet per second (cfs) for standard (2x4) inlets and five cfs for Type 1 standard (2x6) inlets whether located in streets, parking lots or lawn areas.
G. 
In sump areas, other than within a street, the maximum depth of water shall not be more than six inches above the inlet top elevation.
H. 
Regardless of capacity calculations, inlets shall be located to intercept runoff prior to handicapped ramps, prior to every street or driveway (not including those serving single family dwellings) intersection radius, and at sag points of vertical curves and any other low points whether in streets or in parking lots.
I. 
Inlets shall be placed prior to the radius of an intersection not on the curved portion unless unavoidable in order to be located at a low point.
J. 
No inlet smaller than standard PennDOT inlet types C, M and S shall be used within streets.
K. 
Inlets with a depth greater than four feet must be provided with anti-slip ladder rungs.
L. 
A minimum drop of 0.20 feet shall be provided across inlets between the invert elevations of the incoming and outgoing pipes of the same diameter. For pipes of different diameters, the elevation of the crowns of the pipes shall be equal.
M. 
Inlets shall contain the statement "No Dumping Drains to Creek" either cast or inserted into the tops to discourage the placement of anything other than stormwater into the inlet.
N. 
Inlets in paved areas shall be equipped with bicycle safe grates. All inlets shall be designed and located to prevent hazards to vehicles, bicycles and pedestrians.
O. 
Inlet grates shall be depressed one inch in paved areas with inlet tops flush with the curb. Inlets in landscaped areas shall be sumped a minimum of 12 inches.
P. 
To promote smooth flow and self-cleaning, the bottoms of inlets shall be provided with concrete washes (flow channels).
Q. 
All pipe entering an inlet shall be cut flush with the inside of the inlet box.
R. 
Weep holes shall be provided in inlets per PennDOT RC standards.
S. 
Adjustment rings shall only be made of a single pre-cast concrete grade a maximum of six inches in height.
T. 
The annular space where pipes enter inlet boxes shall be sealed with non-shrinking grout.
U. 
All backfill around inlets shall be PennDOT 2A stone compacted in accordance with PennDOT standards.
5. 
Manholes.
A. 
Manholes shall not be spaced more than 400 feet apart for pipes of less than or equal to twenty-four-inch diameter and 500 feet apart for pipes of greater than twenty-four-inch diameter.
B. 
A manhole shall be placed on a continuous storm sewer at all changes in alignment, grade or pipe size, and at all points of convergence of two or more influent storm sewer lines.
C. 
Inlets may be substituted for manholes where they serve a useful purpose.
D. 
Manhole covers shall have the word "STORM" cast on the top of the cover.
E. 
A minimum drop of 0.2 feet shall be provided across manholes between the invert elevations of the incoming and outgoing pipes of the same diameter. For pipes of different diameters, the elevation of the crowns of the pipes shall be equal.
F. 
The maximum allowable headwater depth shall be one-foot below the top of the inlet grate or manhole cover.
G. 
To promote smooth flow and self-cleaning, the bottoms of manholes shall be provided with concrete washes (flow channels).
H. 
All pipe entering a manhole shall be cut flush with the inside of the manhole.
I. 
The annular space where pipes enter manholes shall be sealed with non-shrinking grout.
J. 
Manholes with a depth greater than four feet must be provided with anti-slip ladder rungs.
6. 
End Treatments (Headwalls, Endwalls, Flared Endsections, and Similar Structures).
A. 
At-grade pipe outlets shall be provided with one of these structures.
B. 
All end treatments shall be concrete, regardless of pipe material.
C. 
Safety grates may be required at the municipality's discretion.
D. 
Acceptable energy dissipation devices shall be installed per PADEP's Erosion and Sedimentation Pollution Control Program Manual at every end treatment.
E. 
End treatments shall not be located closer than 10 feet from the edge of a sidewalk, curb or cartway edge.
7. 
Man-Made Open Channels/Swales.
A. 
Properly designed, graded, and lined channels may be permitted in lieu of storm sewers where it can be demonstrated that such channels will be stable under permanent conditions.
B. 
Channels shall not be less than 2% in grade nor more than 10%.
C. 
Underdrains may be required as determined by the municipality's Engineer.
D. 
Channels shall be located on lot lines as necessary to minimize stormwater from draining across lot lines.
E. 
Channel lining must meet the design standards of PADEP's Erosion and Sedimentation Pollution Control Program Manual.
F. 
Channels shall have a maximum side slope grade of three horizontal to one vertical (3:1).
G. 
Channels shall be provided with a minimum six-inch freeboard, measured from the top of the twenty-five-year design storm flow to the top of bank of the channel.
H. 
Channels leading away from emergency spillways, and other channels in areas where damage to property would result, shall be designed to convey the runoff from a one-hundred-year storm.
[Ord. 2013-04, 12/18/2013, § 314]
1. 
Cul-de-sac turnarounds shall be graded to direct all stormwater to the curb in order to minimize icing from sheet flows in freezing temperatures.
2. 
All grading (cut and fill) shall be set back from property lines a sufficient distance to prevent any adverse effects on adjacent properties but in no case less than 10 feet.
3. 
Where a grading cut slope creates an abrupt drop-off from the abutting property line in contrast to a previously existing gradual change, a fence or other suitable barrier shall be installed.
4. 
Grading shall not be done in such a way so as to divert water onto the property of another landowner.
5. 
Sites shall be graded to secure proper drainage away from buildings (minimum 2%) and to allow for the proper collection and conveyance of stormwater.
6. 
Grading operations shall be kept to a minimum to ensure conformity with the natural topography, to minimize erosion hazard, and to adequately handle the surface runoff.
7. 
Except as specified elsewhere in this chapter, cut and fill slopes shall not be steeper than 4:1.
8. 
During grading operations, necessary measures for dust control shall be exercised.
[Ord. 2013-04, 12/18/2013, § 315]
1. 
When subdivision, land developments or other earth disturbances are submitted to the municipality for approval in phases or portions, plans and calculations shall be submitted for the design of the entire tract, including all such phases or portions.
2. 
If construction is contemplated for less than the entire project, the proposed design of the stormwater from the constructed phase(s) shall be provided. The design shall prevent damage to adjacent properties and future phases. Any temporary construction required for the phased design shall be included with the submittal.
3. 
In the event that temporary measures cannot insure protection to adjacent properties or future phases, the permanent BMPs and permanent collection and conveyance system, as necessary, shall be included as part of the construction for the currently proposed phase.
[Ord. 2013-04, 12/18/2013, § 316]
1. 
Construction of a driveway on a lot shall not cause surface runoff on the lot to be directed or concentrated onto an adjoining lot or cause an increase in runoff to an adjoining lot. Stormwater runoff shall be addressed in accordance with the standards herein.
2. 
The intersection of all driveways with the street shall be constructed so that no surface water from the driveway is directed into the street. This may be accomplished by use of a drainage swale or a pipe culvert as follows:
A. 
The drainage swale side slope across the driveway shall slope down from the improved edge of the street for a maximum depth of four inches over a minimum distance of six feet, resulting in a grade of approximately 5 1/2%. Modifications to this requirement may be permitted as field conditions indicate at the sole discretion of the municipality designated official issuing the driveway permit.
B. 
If a pipe is used, it shall be:
(1) 
Sized according to stormwater runoff calculations based upon a twenty-five-year storm frequency, but in no case shall it be less than a minimum diameter of 15 inches.
(2) 
An approved pipe per PennDOT specifications in Publication 408 as amended, unless approved otherwise by the municipality designated official issuing the driveway permit.
(3) 
Placed with its edge at least 10 feet from the improved edge of the street (a 10 clearance). A greater distance from the improved edge of street may be required for larger pipes in order to allow for acceptable grade (maximum 3:1) from the improved edge of the street to the bottom of the pipe allowing for a shoulder and rounding of the cross-slope, four feet minimum. Modifications to this requirement may be permitted as field conditions indicate at the sole discretion of the municipality designated official issuing the driveway permit;
(4) 
Extended a minimum of two feet in length from each edge of the driveway.
(5) 
Provided with the appropriate concrete end treatments such as flared end sections or endwalls. Downstream end treatments may be waived at the sole discretion of the municipality's designated official issuing the driveway permit.