A. 
Applicants proposing regulated activities in the Township of Spring which do not fall under the exemption criteria shown in § 388-22 shall submit a Drainage Plan consistent with the applicable Watershed Stormwater Management Plan to the Township for review. These criteria shall apply to the total proposed development even if development is to take place in stages.
B. 
All regulated activities involving an increase in impervious cover, a diversion of stormwater runoff crossing or leaving a site, or an alteration to the existing groundcover, shall be conducted in conformance with the provisions of this chapter.
C. 
The applicant is required to evaluate practicable alternatives to the surface discharge of stormwater, the creation of impervious surfaces and the degradation of waters of the Commonwealth, and must maintain as much as possible the natural hydrologic regime.
D. 
The Drainage Plan must be designed consistent with the sequencing provisions of § 388-14 to ensure maintenance of the natural hydrologic regime and to promote groundwater recharge and protect groundwater and surface water quality and quantity. The Drainage Plan designer must proceed sequentially in accordance with Article IV of this chapter.
E. 
Existing points of concentrated drainage that discharge onto adjacent property shall not be altered in any manner which could cause property damage without permission of the affected property owner(s) and shall be subject to any applicable discharge criteria specified in this chapter.
F. 
Areas of existing diffused drainage discharge shall be subject to any applicable discharge criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas, except as otherwise provided by this chapter. If diffused drainage discharge is proposed to be concentrated and discharged onto adjacent property, the applicant must document that adequate downstream conveyance facilities exist to safely transport the concentrated discharge, or otherwise prove that no erosion, sedimentation, flooding or other impacts will result from the concentrated discharge.
G. 
Where a development site is traversed by existing watercourses, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easement shall conform to the stream buffer requirements contained in § 388-16F of this chapter.
H. 
Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the Commonwealth or wetlands shall be subject to approval by PaDEP through the Joint Permit Application process, or, where deemed appropriate by PaDEP, the General Permit process. When there is a question whether wetlands may be involved, it is the responsibility of the applicant or his agent to show that the land in question cannot be classified as wetlands, otherwise approval to work in the area must be obtained from PaDEP.
I. 
Any stormwater management facilities that would be located within State highway rights-of-way or any alteration that affects stormwater flow directly or indirectly toward a PennDOT facility shall be subject to PennDOT regulations.
J. 
Minimization of impervious surfaces and infiltration of runoff through seepage beds, infiltration trenches, etc., are encouraged, where soil conditions permit, to reduce the size or eliminate the need for detention facilities or other structural BMPs.
K. 
Roof drains shall not be connected to impervious surfaces in order to promote overland flow and infiltration/percolation of stormwater where advantageous to do so. When site conditions preclude infiltration/percolation, then it shall be permitted on a case by case basis by the Township.
L. 
All stormwater runoff shall be treated for water quality.
M. 
Transference of runoff to or from an EV/HQ watershed is prohibited unless otherwise authorized by PaDEP, DRBC or SRBC.
[Amended at time of adoption of Code (see Ch. 1, General Provisions, Art. I)]
A. 
Whenever the vegetation and topography are to be disturbed, such activity must be in conformance with Chapter 102, Title 25, Rules and Regulations, Part I, Commonwealth of Pennsylvania, Department of Environmental Protection, Subpart C, protection of natural Resources, Article II, Water Resources, Chapter 102, "Erosion Control."
B. 
No regulated earth disturbance activities within the Township shall commence until the Township receives an approval from the Conservation District of an Erosion and Sediment Pollution Control Plan for construction activities.
C. 
PaDEP has regulations that require an Erosion and Sediment Pollution Control Plan for any earth disturbance activity of 5,000 square feet or more, under 25 Pa. Code § 102.4(b).
D. 
In addition, under 25 Pa. Code Chapter 92a, a PaDEP "NPDES Construction Activities" permit is required for regulated earth disturbance activities.
E. 
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate PaDEP regional office or County Conservation District must be provided to the Township. The issuance of an NPDES Construction Permit (or permit coverage under the statewide General Permit (PAG-2) satisfies the requirements § 388-13A.
F. 
A copy of the Erosion and Sediment Pollution Control Plan and any required permit, as required by PaDEP regulations, shall be available at the project site at all times.
G. 
Additional erosion and sediment pollution control design standards and criteria, recommended to be applied where infiltration BMPs are proposed, shall include the following:
(1) 
Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase to maintain maximum infiltration capacity.
(2) 
Infiltration BMPs shall not be constructed nor receive runoff until the entire contributory drainage area to the infiltration BMP has achieved final stabilization.
H. 
Erosion and sediment pollution control devices shall be installed concurrently with earthmoving activities and whenever a situation is created which would contribute to increased erosion.
I. 
No earthmoving or stripping of vegetation will be conducted in areas of greater than 33% slope unless specific approval is obtained from the Township.
J. 
Earthmoving and the addition of fill shall be maintained where possible and practicable to preserve desirable natural features and the topography of the site. Changes in grade and topography and other earthmoving shall be in accordance with the approved Erosion and Sediment Pollution Control Plan.
K. 
Stripping of vegetation, regrading or other development shall be done in such a way that will minimize erosion.
L. 
All clearing and grading operations shall comply with the requirements for tree preservation included in Chapter 450, Zoning.
(1) 
Land disturbance shall be limited to the actual construction site and an access strip. The amount of disturbed area and the duration of exposure shall be kept to a practical minimum.
(2) 
To the maximum extent practicable, mature healthy trees of at least six inches trunk width measured three feet above the average surrounding ground level shall be retained and protected. Such trees shall not be removed except as provided on the approved subdivision or land development plan and in accordance with the applicable provisions of Chapter 450, Zoning. The filling of soil over the roots of trees to be preserved is prohibited. (The roots are presumed to extend out from the tree as far as the tree's branches extent outward.)
M. 
Procedures for protecting soils or geologic structures with water supply potential from contamination by surface water or other disruption by construction activity shall be established in consultation with the Township and such areas shall include, at minimum, those underlain by carbonate limestone formations. The Township may require pollution control facilities to be provided on existing and proposed stormwater management systems within or adjacent to the project site.
N. 
Provisions for protecting existing wells or other water supplies shall be established.
O. 
Unless otherwise permitted, graded slopes shall not be steeper than three horizontal units to one vertical unit.
P. 
A minimum of four inches of topsoil shall be provided on all disturbed areas prior to final seeding and mulching.
Q. 
Adequate erosion protection shall be provided along all open channels, and at all points of discharge (PaDEP Erosion, Sediment and Pollution Control Manual).
R. 
Sediment and erosion pollution control facilities shall be designed according to applicable governmental standards, specifically the following:
(1) 
PaDEP sediment and erosion control plan requirements in Chapter 102, Title 25 [Pa.Code].
(2) 
Berks County Conservation District standards, which has been delegated by the Pennsylvania Department of Environmental Protection to enforce the Erosion and Sediment Pollution Control Plan.
(3) 
It shall be the responsibility of the applicant to submit the application and other necessary material to the Berks County Conservation District. Comments shall be received and compliance therewith accomplished prior to final plan approval.
A. 
For projects disturbing one acre or more, the design of all regulated activities shall include evaluation of practicable alternatives to the surface discharge of stormwater, the creation of impervious surfaces, and the degradation of waters of the Commonwealth, and must maintain as much as possible the natural hydrologic regime of the site.
(1) 
An alternative is practicable if it is available and capable of being done after taking into consideration cost, existing technology and logistics in light of overall project purposes, and other Township requirements.
(2) 
All practicable alternatives to the discharge of stormwater are presumed to have less adverse impact on quantity and quality of waters of the Commonwealth unless otherwise demonstrated.
B. 
The applicant shall demonstrate that the design of regulated activities that disturb one acre or more include the following issues:
(1) 
Preparation of an Existing Resource and Site Analysis Map (ERSAM), showing environmentally sensitive areas, including, but not limited to, steep slopes, ponds, lakes, streams, wetlands, hydric soils, vernal pools, floodplains, stream buffer zones, hydrologic soil groups A and B (areas conducive to infiltration), areas of limestone or karst geology, special geologic features, any existing recharge areas and any other requirements outlined in Chapter 400, Subdivision and Land Development.
(2) 
Establishment of appropriate buffers for each of the delineated environmentally sensitive areas per Chapter 450, Zoning, and this chapter. (See § 388-16F for stream buffers and § 388-15B(11) for special geologic feature buffers.)
(3) 
Preparation of a draft project layout avoiding sensitive areas identified in § 388-14B(1).
(4) 
Identification of site specific existing conditions drainage areas, discharge points, recharge areas and hydrologic soil groups A and B.
(5) 
Evaluation of nonstructural stormwater management alternatives.
(a) 
Minimization of earth disturbance.
(b) 
Minimization of impervious surfaces.
(c) 
Break up of large impervious surfaces.
(6) 
Compliance with the infiltration objective (§ 388-15) and provisions for stormwater pretreatment prior to infiltration. Pretreatment may not be necessary for rooftop runoff which enters the infiltration facility directly from a roof leader.
(7) 
Compliance with water quality provisions (§ 388-16) and streambank erosion protection objective (§ 388-17).
(8) 
Determination of applicable Management District (Appendix D[1]) and performance of an existing conditions runoff analysis.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
(9) 
Preparation of final project design to maintain existing conditions drainage areas and discharge points, to minimize earth disturbance and impervious surfaces, and to the maximum extent possible, to ensure the remaining site development has no surface or point discharge.
(10) 
Performance of a proposed conditions runoff analysis based on the final design, and meeting the release rate and the overbank flow and extreme event requirements (§ 388-18).
(11) 
Management of any remaining runoff through treatment prior to discharge, as part of detention, bioretention, direct discharge or other structural control.
A. 
Maximizing the groundwater recharge capacity of the area being developed is required. Design of the infiltration stormwater management facilities shall give consideration to providing groundwater recharge to compensate for the reduction in the percolation that occurs when the ground surface is disturbed or impervious surface is created. It is recommended that roof runoff be directed to infiltration BMPs which can be over-designed to compensate for runoff from, and infiltration losses due to, parking areas. These measures are required to be consistent with § 388-3, and take advantage of utilizing any existing recharge areas.
B. 
Infiltration may not be feasible on every site due to site-specific limitations such as soil type. If it cannot be physically accomplished, due to seasonal high water table, soil permeability rate, soil depth or setback distances from special geologic features, then the design professional shall be responsible to show that this cannot be physically accomplished. If it can be physically accomplished, then the volume of runoff to be infiltrated shall be determined from § 388-15B(1)(c) depending on demonstrated site conditions and shall be the greater of the two volumes.
(1) 
Infiltration BMPs shall meet the following minimum requirements:
(a) 
Infiltration requirements. Regulated activities will be required to infiltrate, where site conditions permit, a portion of the runoff created by the development as part of an overall stormwater management plan designed for the site. The volume of runoff to be infiltrated shall be determined from § 388-15B(1)(c)[1] or [2], depending upon demonstrated site conditions.
(b) 
Infiltration BMPs intended to receive runoff from developed areas shall be selected based on suitability of soils and site conditions and shall be constructed on soils that have the following characteristics:
[1] 
A minimum depth of 24 inches between the bottom of the BMP and the limiting zone.
[2] 
An infiltration and/or percolation rate sufficient to accept the additional stormwater load and drain completely as determined by field tests conducted by the applicant's design professional.
[3] 
The infiltration facility shall be capable of completely infiltrating the required retention (infiltration) volume within four days (96 hours).
[4] 
Pretreatment shall be provided prior to infiltration. The pretreatment shall be designed to protect the infiltration system from clogging prior to scheduled maintenance and to protect groundwater quality.
(c) 
The size of the infiltration facility shall be based upon the following volume criteria:
[1] 
NRCS Curve Number equation.
[a] 
The NRCS runoff equation shall be utilized to calculate infiltration requirements (I) in inches.
I (Infiltration requirement, in inches) = (200/CN) - 2 Eqn: 305.1
Where:
CN
=
SCS (NRCS) curve number of existing conditions contributing to the infiltration facility.
[b] 
This equation is displayed graphically in, and the infiltration requirement can be determined from Figure 305.1.
[c] 
It has been determined that infiltrating 0.46 inches of runoff from the impervious areas will aid in maintaining the hydrologic regime of the watershed. However, the rounded number 0.5 inches will be used.
Figure 305.1. Infiltration requirement based upon NRCS Curve Number.
[d] 
The retention (infiltration) volume (Rev) required to meet the infiltration requirement would therefore be computed as:
Rev = (0.5 or I, whichever is greater)* impervious area (square feet)/(12 in/ft) = Cubic Feet
Eqn: 305.2
Where:
I
=
infiltration requirements (in inches.)
[2] 
Annual Recharge - Water Budget Approach.
[a] 
If the goals of § 388-15B(1)(c)[1] cannot be achieved, then 0.5 inches of rainfall shall be infiltrated from all impervious areas, up to an existing site conditions curve number of 81. Above a curve number of 81, Equation 305.1 or the curve in.
[b] 
Figure 305.1 should be used to determine the infiltration requirement.
[c] 
The retention (infiltration) volume (Rev) required again would therefore be computed as:
Rev = (0.5 or I, whichever is greater)* impervious area (sq. ft.)/(12 in/ft) = Cubic Feet.
(2) 
Soils. A detailed soils evaluation of the project site shall be required where practicable to determine the suitability of infiltration facilities. The evaluation shall be performed by a qualified design professional, and at a minimum, address soil permeability, depth to bedrock, presence of special geologic features and subgrade stability. The general process for designing the infiltration BMP shall be:
(a) 
Analyze hydrologic soil groups as well as natural and man-made features within the site to determine general areas of suitability for infiltration practices. In areas where development on fill material is under consideration, conduct geotechnical investigations of subgrade stability; infiltration is not permitted to be ruled out without conducting these tests.
(b) 
Provide field tests such as double ring infiltrometer or hydraulic conductivity tests (at the level of the proposed infiltration surface) to determine the appropriate hydraulic conductivity rate. Percolation tests are not recommended for design purposes.
(c) 
Design the infiltration structure for the required retention (Rev) volume based on field determined capacity at the level of the proposed infiltration surface.
(d) 
If on-lot infiltration structures are proposed by the applicant's design professional, it must be demonstrated to the Township that the soils are conducive to infiltrate on the lots identified.
(3) 
Carbonate areas.
(a) 
The applicant is required to investigate the ability of all areas on the site which are not underlain by carbonate rock to meet the infiltration requirements of § 388-15B(1). If this investigation proves infeasible, infiltration may occur on areas underlain by carbonate rock. Nevertheless, extreme caution shall be exercised where infiltration is proposed in geologically susceptible areas. Design of such infiltration facilities shall follow the recommended procedure below in conjunction with Figure B-1 in Appendix B[1]; however, the applicant is not required to use infiltration in carbonate areas even if the site falls into the "Recommended" range on Figure B-1 in Appendix V. If infiltration is not proposed, the calculated infiltration volume [§ 388-15B(1)] shall be treated by an acceptable BMP.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
(b) 
Infiltration BMP loading rate percentages in Figure B-1 in Appendix B shall be calculated as follows:
(Area tributary to the infiltration BMP\Base Area of the infiltration BMP)*100%
(c) 
The area tributary to the infiltration BMP shall be weighted as follows:
Area Description
Weighting
All disturbed area to be made impervious
100%
All disturbed areas to be made pervious
50%
All undisturbed impervious areas
100%
All undisturbed pervious areas
0%
(d) 
Soil thickness is to be measured from the bottom of any proposed infiltration BMP. The effective soil thickness in Figure B-1 in Appendix B is the measured soil thickness multiplied by the thickness factor based on soil permeability, as follows:
Permeability Range
Thickness Factor
6.0 to 12.0 inches/hr
0.8
2.0 to 6.0 inches/hr
1.0
1.0 to 2.0 inches/hr
1.4
0.75 to 1.0 inches/hr
1.2
0.5 to 0.75 inches/hr
1.0
(e) 
The design of all facilities over Karst shall include an evaluation of measures to minimize adverse effects.
(4) 
Stormwater hotspots. Following is a list of examples of designated hotspots. If a site is designated as a hotspot, it has important implications for how stormwater is managed. First and foremost, untreated stormwater runoff from hotspots shall not be allowed to recharge into groundwater where it may contaminate water supplies. Therefore, the Rev requirement shall NOT be applied to development sites that fit into the hotspot category (the entire WQv must still be treated). Second, a greater level of stormwater treatment shall be considered at hotspot sites to prevent pollutant washoff after construction. EPA's NPDES stormwater program requires some industrial sites to prepare and implement a stormwater pollution prevention plan.
(a) 
Examples of hotspots:
[1] 
Vehicle salvage yards and recycling facilities.
[2] 
Vehicle fueling stations.
[3] 
Vehicle service and maintenance facilities.
[4] 
Vehicle and equipment cleaning facilities.
[5] 
Fleet storage areas (bus, truck, etc.).
[6] 
Industrial sites (based on Standard Industrial Codes).
[7] 
Marinas (service and maintenance).
[8] 
Outdoor liquid container storage.
[9] 
Outdoor loading/unloading facilities.
[10] 
Public works storage areas.
[11] 
Facilities that generate or store hazardous materials.
[12] 
Commercial container nursery.
[13] 
Other land uses and activities as designated by an appropriate review authority.
(b) 
The following land uses and activities are not normally considered hotspots:
[1] 
Residential streets and rural highways.
[2] 
Residential development.
[3] 
Institutional development.
[4] 
Office developments.
[5] 
Non-industrial rooftops.
[6] 
Pervious areas, except golf courses and nurseries (which may need an Integrated Pest Management (IPM) Plan).
(c) 
While large highways (average daily traffic volume (ADT) greater than 30,000) are not designated as a stormwater hotspot, it is important to ensure that highway stormwater management plans adequately protect groundwater.
(5) 
Caution shall be exercised where infiltration is proposed in Source Water Protection Areas as defined by the Township or local Water Authority/Provider.
(6) 
Infiltration facilities shall be used in conjunction with other innovative or traditional stormwater control facilities that are found within the PaDEP State BMP Manual.
(7) 
Caution shall be exercised where salt or chloride (municipal salt storage) would be a pollutant since soils do little to filter this pollutant and it may contaminate the groundwater. The qualified design professional shall evaluate the possibility of groundwater contamination from the proposed infiltration facility and perform a hydrogeologic justification study if necessary.
(8) 
The infiltration requirement in High Quality or Exceptional Value waters shall be subject to the Department's Chapter 93 Antidegradation Regulations.
(9) 
Dependent upon certain land uses or hotspots an impermeable liner will be required in detention basins where the possibility of groundwater contamination exists. A detailed hydrogeologic investigation may be required by the Township.
(10) 
The Township shall require the applicant to provide safeguards against groundwater contamination for land uses that may cause groundwater contamination should there be a mishap or spill.
(11) 
For projects that disturb one acre or more, unless greater setbacks are specified in Chapter 450, Zoning, the following setbacks for infiltration facilities shall apply:
(a) 
One hundred feet from water supply wells;
(b) 
Ten feet downslope or 100 feet upslope from building foundations;
(c) 
Fifty feet from septic system drainfields;
(d) 
One hundred feet from a geologic contact with carbonate bedrock, unless a preliminary site investigation is done in the carbonate bedrock to show the absence of special geologic features within 100 feet of the proposed infiltration area; and
(e) 
One hundred feet from the property line unless documentation is provided to show all setbacks from wells, foundations and drainfields on the neighboring property will be met.
The applicant shall comply with the following water quality requirements of this chapter.
A. 
Developed areas shall provide adequate storage and treatment facilities necessary to capture and treat stormwater runoff. The infiltration volume computed under § 388-15 may be a component of the water quality volume if the applicant chooses to manage both components in a single facility. If the infiltration volume is less than the water quality volume, the remaining water quality volume may be captured and treated by methods other than infiltration BMPs. The required water quality volume (WQv) is the storage capacity needed to capture and treat a portion of stormwater runoff from the developed areas of the site. To achieve this goal, the following criterion is established:
(1) 
The following calculation formula is to be used to determine the water quality storage volume, (WQv), in acre-feet of storage for any watershed within the Township of Spring:
WQv = [(P)(Rv)(A)]/12
Eqn: 306.1
WQv
=
Water Quality Volume (acre-feet)
P
=
1 inch
A
=
Total contributing drainage area to the water quality BMP (acres)
Rv
=
0.05 + 0.009(I) where I is the percent of the area that is impervious surface ((impervious area/A)*100)
(2) 
This volume requirement can be accomplished by the permanent volume of a wet basin or the detained volume from other BMPs.
(3) 
Release of water can begin at the start of the storm (i.e., the invert of the water quality orifice is at the invert of the facility). The design of the facility shall provide for protection from clogging and unwanted sedimentation.
B. 
For areas within defined Special Protection subwatersheds which include Exceptional Value (EV) and High Quality (HQ) waters, Cold Water Fishery (CWF) the temperature and quality of water and streams shall be maintained.
C. 
To accomplish the above, the applicant shall use innovative or traditional stormwater control facilities that are found within the PaDEP State BMP Manual.
D. 
If a perennial or intermittent stream passes through the site, the applicant shall create a stream buffer extending a minimum of 50 feet to either side of the top-of-bank of the channel. The buffer area shall be maintained with appropriate native vegetation (Reference to Appendix H of Pennsylvania Handbook of Best Management Practices for Developing Area for plant lists). If the applicable rear or side yard setback is less than 50 feet, the buffer width may be reduced to 25% of the setback to a minimum of 10 feet. However, in no case shall such buffer be less in width than that specified for a riparian buffer in Chapter 450, Zoning. If an existing buffer is legally prescribed (i.e., deed, covenant, easement, etc.) and it exceeds the requirements of this chapter, the existing buffer shall be maintained. This does not include lakes or wetlands.
E. 
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate PaDEP regional office must be provided to the Township. The issuance of an NPDES Construction Permit (or permit coverage under the statewide General Permit (PAG-2) satisfies the requirements of § 388-16A.
F. 
In selecting the appropriate BMPs or combinations thereof, the land developer SHALL consider the following:
(1) 
Total contributing area.
(2) 
Permeability and infiltration rate of the site soils.
(3) 
Slope and depth to bedrock.
(4) 
Seasonal high water table.
(5) 
Proximity to building foundations and well heads.
(6) 
Erodibility of soils.
(7) 
Land availability and configuration of the topography.
G. 
The following additional factors SHOULD be considered when evaluating the suitability of BMPs used to control water quality at a given development site:
(1) 
Peak discharge and required volume control.
(2) 
Stream bank erosion.
(3) 
Efficiency of the BMPs to mitigate potential water quality problems.
(4) 
The volume of runoff that will be effectively treated.
(5) 
The nature of the pollutant being removed.
(6) 
Maintenance requirements.
(7) 
Creation/protection of aquatic and wildlife habitat.
(8) 
Recreational value.
(9) 
Enhancement of aesthetic and property value.
A. 
In addition to control of the water quality volume, in order to minimize the impact of stormwater runoff on downstream streambank erosion, the primary requirement is to design a BMP to detain the proposed conditions two-year, twenty-four-hour design storm to the existing conditions one-year peak flow using the NRCS Type II distribution. Additionally, provisions shall be made (such as adding a small orifice at the bottom of the outlet structure) so that the proposed conditions one-year storm takes a minimum of 24 hours to drain from the facility from a point where the maximum volume of water from the one-year storm is captured. (i.e., the maximum water surface elevation is achieved in the facility). Release of water can begin at the start of the storm (i.e., the invert of the water quality orifice is at the invert of the facility).
B. 
The minimum orifice size in the outlet structure to the BMP shall be a three inch diameter orifice and a trash rack shall be installed to prevent clogging. On sites with small contributing drainage areas to this 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. Orifice sizes less than three inches can be utilized provided that the design will prevent clogging of the intake.
A. 
The Watersheds within the Township of Spring have been divided into stormwater management districts as shown on the Management District Map(s) in Appendix D[1].
(1) 
In addition to the requirements specified in Tables 308.1a through 308.1.d below, the groundwater recharge (§ 388-15), water quality (§ 388-16), and streambank erosion control (§ 388-17), requirements shall be implemented.
(2) 
Standards for managing runoff from each subarea in the Schuylkill River, Tulpehocken Creek, Cocalico Creek and Conestoga River Watersheds for all required design storms are shown in Tables 308.1.a through 308.1.d. Development sites located in each of the Districts must control proposed conditions runoff rates to existing conditions runoff rates for the design storms in accord with Tables 308.1.a through 308.1.d.
Table 308.1.a - Water Quantity Requirements - Schuylkill River Watershed
Management District
Proposed Condition Design Storm
Existing Condition Design Storm
A
2-year
Reduce To
1-year
5-year
5-year
10-year
10-year
25-year
25-year
50-year
50-year
100-year
100-year
B
2-year
Reduce To
1-year
5-year
2-year
10-year
5-year
25-year
10-year
50-year
25-year
100-year
50-year
C
2-year
Reduce To
1-year
5-year
5-year
10-year
10-year
25-year
25-year
50-year
50-year
100-year
100-year
Table 308.1.b - Water Quantity Requirements - Tulpehocken Creek Watershed
Management District
Proposed Condition Design Storm
Existing Condition Design Storm
A
2-year
Reduce To
1-year
5-year
5-year
10-year
10-year
25-year
25-year
B-1
2-year
Reduce To
1-year
5-year
2-year
10-year
5-year
25-year
10-year
C
2-year
Reduce To
1-year
5-year
2-year
(3) 
Explanation of District C. Development sites which can discharge directly to the Tulpehocken Creek main channel or major tributaries or indirectly to the main channel through an existing stormwater drainage system (i.e., storm sewer or tributary) may do so without control of post-development peak rate of runoff greater than the five-year storm. If the post-development 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 downstream system does not exist and will not be provided through improvements, the post-development peak rate of runoff must be controlled to the pre-development peak rate as required in District A provisions (i.e., ten-year post-development flows to 10 pre-development flows) for the specified design storms.
Table 308.1.c - Water Quantity Requirements - Cocalico Creek Watershed
Post-development rates of runoff from any regulated activity within the Cocalico Creek Watershed shall not exceed 50% of the peak rates of runoff prior to development for all design storms unless the preexisting hydrograph is not exceeded at all points in time.
Table 308.1.d - Water Quantity Requirements - Conestoga River Watershed
Management District
Proposed Condition Design Storm
Existing Condition Design Storm
A
All Design Storms
Reduce To
30% of Peak Flow for All Design Storms
B
All Design Storms
Reduce To
50% of Peak Flow for All Design Storms
(4) 
All areas, regardless of the release rate, must still meet the requirements of the groundwater recharge criteria (§ 388-15), water quality criteria (§ 388-16), and streambank erosion criteria (§ 388-17).
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
B. 
General. Proposed condition rates of runoff from any regulated activity shall not exceed the peak release rates of runoff prior to development for the design storms specified on the Stormwater Management District Watershed Map(s) (Appendix D)[2] and § 388-18, of this chapter.
[2]
Editor's Note: Said appendix is included as an attachment to this chapter.
C. 
District boundaries. The boundaries of the Stormwater Management Districts are shown on an Official Map that is available for inspection at the Township office. A copy of the Official Map at a reduced scale is included in Appendix D[3]. The exact location of the Stormwater Management District boundaries as they apply to a given development site shall be determined by mapping the boundaries using the two-foot topographic contours (or most accurate data required) provided as part of the Drainage Plan.
[3]
Editor's Note: Said appendix is included as an attachment to this chapter.
D. 
Sites located in more than one district. For a proposed development site located within two or more stormwater management district category subareas, the peak discharge rate from any subarea shall meet the Management District Criteria for which the discharge is located, as indicated in § 388-18. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea. An exception to the above may be granted if discharges from multiple subareas recombine in proximity to the discharge site. In this case, peak discharge in any direction shall follow Management District A criteria provided that the overall site discharge meets the Management District Criteria for which the discharge is located.
E. 
Off-site areas. Off-site areas that drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates. However, on-site drainage facilities shall be designed to safely convey off-site flows through the development site.
F. 
Site areas. Where the site area to be impacted by a proposed development activity differs significantly from the total site area, only the proposed impact area utilizing stormwater management measures shall be subject to the Management District Criteria. In other words, unimpacted areas bypassing the stormwater management facilities would not be subject to the Management District Criteria.
A. 
Stormwater runoff from all development sites with a drainage area of greater than 200 acres shall be calculated using a generally accepted calculation technique that is based on the NRCS soil cover complex method. Table 309-1 summarizes acceptable computation methods and the method selected by the design professional shall be based on the individual limitations and suitability of each method for a particular site. The Rational Method shall be used to estimate peak discharges from drainage areas that contain less than 200 acres. The Soil Complex Method shall be used for drainage areas greater than 200 acres.
Table 309-1
Acceptable Computation Methodologies For Stormwater Management Plans
Method
Method Developed By
Applicability
TR-20 (or commercial computer package based on TR-20)
USDA NRCS
Applicable where use of full hydrology computer model is desirable or necessary.
TR-55 (or commercial computer package based on TR-55)
USDA NRCS
Applicable for land development plans within limitations described in TR-55.
HEC-1/HEC-HMS
US Army Corps of Engineers
Applicable where use of full hydrologic computer model is desirable or necessary.
PSRM
Penn State University
Applicable where use of a hydrologic computer model is desirable or necessary; simpler than TR-20 or HEC-1.
Rational Method (or commercial computer package based on Rational Method)
Emil Kuichling (1889)
For sites less than 200 acres and with time of concentration less than 60 minutes (tc <60 min), or as approved by the Township.
Other Methods
Varies
Other computation methodologies approved by the Township.
*
Note: Successors to the above methods are also acceptable. These successors include WinTR55 for TR-55 and WinTR20 for TR-20 and SWMM
B. 
All calculations consistent with this chapter using the soil cover complex method shall use the appropriate design rainfall depths for the various return period storms according to the region in which they are located as presented in Table B-1 in Appendix B of this chapter. If a hydrologic computer model such as PSRM or HEC-1/HEC-HMS is used for stormwater runoff calculations, then the duration of rainfall shall be 24 hours. The rainfall distribution should reference to NOAA Atlas 14.
C. 
For the purposes of existing conditions flow rate determination, undeveloped land shall be considered as "meadow" in good condition, unless the natural ground cover generates a lower curve number or Rational 'C' value (i.e., forest), as listed in Table B-1 or B-2 in Appendix B[1] of this chapter. In such cases, values representing the actual ground cover shall be utilized. Average antecedent moisture conditions shall apply to existing condition calculations.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
D. 
All calculations using the Rational Method shall use rainfall intensities consistent with appropriate times-of-concentration for overland flow and return periods from the NOAA Atlas 14 Precipitation-Frequency Atlas of the United States (2004, revised 2006). When approved by the Township, rainfall intensities may be based upon the current PennDOT Storm Intensity-Duration-Frequency chart for Region 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. NRCS lag equation divided by 0.6 as acceptable method for Tc in undeveloped areas.
E. 
Times of concentration shall be based on the following design parameters:
(1) 
Sheet flow: The maximum length for each reach of sheet or overland flow before shallow concentrated or open channel flow develops is 150 feet. Flow lengths greater than 100 feet shall be justified based on the actual conditions at each development site. The maximum construction phase and post-development sheet flow length for unpaved surfaces shall be 100 feet for most situations 150 feet for areas which will remain undisturbed).
(2) 
Shallow concentrated flow: Travel time for shallow concentrated flow shall be determined using Figure 3-1 from TR-55, Urban Hydrology for small watersheds, as shown in Appendix B6.
(3) 
Open channel flows: At points where sheet and shallow concentrated flows concentrate in field depressions, swales, gutters, curbs, or pipe collection systems, the travel times and downstream end of the development site between these design points shall be based upon Manning's Equation and/or acceptable engineering design standards as determined by the municipal engineer.
F. 
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-1 in Appendix B of this chapter.[2]
[2]
Editor's Note: Said appendix is included as an attachment to this chapter.
G. 
Runoff coefficients (c) for both existing and proposed conditions for use in the Rational method shall be obtained from Table B-2 in Appendix B of this chapter.[3]
[3]
Editor's Note: Said appendix is included as an attachment to this chapter.
H. 
Where uniform flow is anticipated, the Manning equation shall be used for hydraulic computations, and to determine the capacity of open channels, pipes, and storm sewers. Values for Manning's roughness coefficient (n) shall be consistent with Table B-3 in Appendix B of this chapter.[4] Full flow shall be assumed for closed conduits.
[4]
Editor's Note: Said appendix is included as an attachment to this chapter.
I. 
Outlet structures for stormwater management facilities shall be designed to meet the performance standards of this chapter using any generally accepted hydraulic analysis technique or method.
J. 
The design of any stormwater detention facilities intended to meet the performance standards of this chapter shall be verified by routing the design storm hydrograph through these facilities using the Storage-Indication Method. This shall be performed for both the post-development and construction phase conditions. For drainage areas greater than 200 acres in size, the design storm hydrograph shall be computed using a calculation method that produces a full hydrograph (i.e. TR-20, TR-55, HEC-1, PSRM). 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.
K. 
During the construction progression of a project, the discharge of stormwater runoff from the site may follow distinct patterns that will be altered during the course of the construction. In such an event, the comparison of the construction phase discharge rate to the predevelopment rate shall be performed for each separate and distinct pattern. At no time throughout the construction phase of a project shall the peak discharge rate discharging from any location along the boundary of a site exceed the predevelopment peak discharge rate at that location.
L. 
Where applicable, construction phase and post-development time of concentration to a storage facility shall be the time of concentration in the storm sewer to its point of discharge into the storage facility. Overland flow from the discharge point to the outlet structure shall not be included in the time of concentration.
M. 
When designing regional storage facilities for office parks, industrial parks, etc., the following design criteria shall be followed:
(1) 
Assumed impervious, lawn, etc., coverage areas shall be noted in the calculations for each lot which will drain to the basin. Impervious coverage shall be assumed to be the maximum coverage allowed by Chapter 450, Zoning.
(2) 
A six minute time of concentration shall be used to calculate the post-development basin inflow hydrographs (five minutes for rational method). Longer times of concentration shall be allowed only where significant portions of the drainage area will remain undeveloped or where it can be demonstrated that the longer times will occur even after the full potential development.
(3) 
For lots which will have on lot detention or retention basins, the predevelopment time of concentration for the lot shall be the same as the predevelopment time of concentration for the entire predevelopment drainage area in which it is located.
A. 
General requirements.
(1) 
For any of the activities regulated by this chapter, including the preliminary or final approval of subdivision and/or land development plans, the management of stormwater on the site, both during and upon completion of the proposed disturbances, shall be accomplished in accordance with the standards and criteria of this chapter.
(2) 
The design of any temporary or permanent facilities and structures and the utilization of any natural drainage systems shall be in full compliance with these terms and the interpretations of the Township.
(3) 
Any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures), water encroachments, and any work involving wetlands governed by PaDEP Chapter 105 regulations (as amended or replaced from time to time by PaDEP), are subject to PaDEP Chapter 105 regulations.
(4) 
Any proposed roadway drainage facilities shall be designed according to PennDOT Design Manual Part II.
(5) 
The Township reserves the right to disapprove any design that would result in the construction in or continuation of a stormwater problem area.
(6) 
All stormwater management facilities shall comply with the applicable provisions of the Township of Spring Construction Manual and Standard Specifications.
(7) 
Any developer shall be responsible for the control of surface water from his property to a point of natural disposal. It shall be the responsibility of the applicant to obtain, from adjacent property owners, any easements or other necessary property interests concerning flowage of water from the proposed development onto private lands. The construction of improvements necessary to control runoff and prevent property damage may be required. Whenever practicable, the easement shall be parallel with and conjunctive to property lines of the project site.
(8) 
All streets shall be so designed as to provide for the discharge of surface water from their rights-of-way.
(9) 
The slope of the crown on proposed streets shall not be less than 1/8 inch per foot and not more than 1/3 inch per foot.
(10) 
Increases or decreases in the hydrology of natural wetlands or changes to the function of wetlands shall be minimized to the maximum extent practical. Where such changes are proposed, the impact of the proposal on wetland functional values shall be assessed using standard methods appropriate to the affected wetland.
B. 
Detention and retention basin design.
(1) 
Any stormwater management facility (i.e., detention basin, retention basins) designed to store runoff and requiring a berm or earthen embankment required or regulated by this chapter shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year proposed conditions and may be subject to PaDEP Chapter 105 regulations.
(2) 
No stormwater detention or retention facility shall be placed within 50 feet of a special geologic feature.
(3) 
Whenever a basin will be located in an area underlain by limestone, a geological evaluation of the proposed location shall be conducted to determine susceptibility to sinkhole formations. The design of all facilities over limestone formations shall include measures to prevent groundwater contamination and, where necessary, sinkhole formation. The Township may require the installation of an impermeable liner in detention or retention basins. A detailed hydrogeologic investigation may be required by the Township.
(4) 
It shall be the developer's responsibility to verify if the site is underlain by limestone. The following note shall be attached to all Drainage Plans and signed and sealed by the professional responsible for confirming the site's geologic conditions:
"I, _______________, a registered __________ of the Commonwealth of Pennsylvania, do hereby certify that the proposed detention basin (circle one) is/is not underlain by limestone."
(5) 
Basins shall be installed prior to any earthmoving or land disturbances which they will serve. The phasing of their construction shall be noted in the narrative and on the plan.
(6) 
Energy dissipators and/or level spreaders shall be installed at points where pipes or drainageways discharge to or from basins.
(7) 
Interior and exterior slopes of compacted soil shall not exceed one foot vertical for three feet horizontal, and may be further reduced if the soil has unstable characteristics. Unless otherwise required to comply with PaDEP regulations, the minimum bottom slope shall be 2% for grass and 0.75% for concrete paving. 1% may be used for grass if an underdrain system is provided. A concrete low flow channel shall be required for all basins where the distance from the inlet pipe to the outlet structure exceeds 100 feet. The minimum channel width shall be four feet and the design must be approved by the Township.
(8) 
Detention and retention basins shall also be designed to meet the following requirements:
(a) 
The minimum top of berm width shall be eight feet.
(b) 
Outlet pipes shall have a minimum diameter of 12 inches. For pipe lengths exceeding 100 feet, the minimum diameter shall be 15 inches.
(c) 
Properly spaced antiseep collars shall be installed on all basin outlet pipes. Design calculations shall be provided.
(9) 
A key trench at least two feet deep, or extending down to stable subgrade, whichever is deeper, of compacted relatively impervious material (Unified Soil Classification CL or ML) shall be provided. Minimum bottom width for the key trench shall be four feet. Maximum side slopes for the key trench shall be one horizontal to one vertical. A compacted impervious core at least eight feet wide at the top, having a maximum side slope of one horizontal to one vertical, shall extend for the full length of the embankment, and the top elevation shall be set at the design year water surface elevation.
(10) 
All pipes and culverts through embankments shall have properly spaced anti-seep collars (minimum six-inch thick).
(11) 
Outlet structures within basins which will control peak discharge flows and distribute the flows by plans to discharge areas shall be constructed of reinforced concrete, and shall have childproof, nonclogging trash racks over all design openings 12 inches in diameter, except those openings designed to carry perennial stream flows.
(12) 
Emergency spillways shall be constructed of concrete of sufficient mass and structural stability to withstand the pressures of impounded waters and outlet velocities. Precast concrete paving blocks and sod may be used when approved by the Township. Emergency spillways shall be designed to safely convey the one-hundred-year basin inflow hydrograph through the basin assuming the principal outlet is completely blocked, and a minimum one foot freeboard shall be provided. Should any stormwater management facility require a dam safety permit under PaDEP Chapter 105, the facility shall be designed in accordance with Chapter 105 and meet the regulations of Chapter 105 concerning dam safety which may be required to pass storms larger than the one-hundred-year event.
(13) 
Inlet and outlet structures shall be located at maximum distances from one another. The Township may require a rock filter berm or rock-filled gabions between inlet and outlet areas when the distance is deemed insufficient for sediment trappings.
(14) 
Permanent grasses or stabilization measures shall be established on the sides of all earthen basins by hydroseeding within five days of initial construction. The Township may require jute or erosion control matting to be installed inside the basin or on the basin embankment.
(15) 
Adequate drainage courses shall be provided and maintained for the discharge(s) from the basin. If the basin will not discharge to a suitable natural drainage course, the Township may require the developer to provide facilities to safely and efficiently convey the discharge to a suitable drainage course. Securing of necessary drainage easements for this purpose shall be the sole responsibility of the developer.
(16) 
When PaDEP requires facilities to have a State permit, the designer shall submit all information to PaDEP and obtain all necessary approval and permits. No stormwater facility shall create health or sanitation problems. Consideration shall be given to safety standards.
(17) 
When deemed necessary by the Board of Supervisors, stormwater detention facilities shall be enclosed with a fence of a type approved by the Board of Supervisors.
(18) 
Paved surfaces that are to serve as stormwater storage areas shall have minimum grades of 1/2% and shall be restricted to storage depths of one-half feet maximum. If a portion of an area within a stormwater storage area is to be paved for parking or recreational purposes, the paved surface shall be placed at the highest elevation with the storage area as possible.
(19) 
The following additional conditions shall be complied with for wet bottom stormwater storage areas:
(a) 
Water surface area shall not exceed 1/10 of the tributary drainage area,
(b) 
Shoreline protection shall be provided to prevent erosion from wave action.
(c) 
Minimum normal water depth shall be four feet. If fish are to be used to keep the pond clean, a minimum of 1/4 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 shoreline maintenance.
(e) 
Aeration facilities as may be required to prevent pond stagnation shall be provided. Design calculations to substantiate the effectiveness of these aeration facilities shall be submitted with final engineering plans. Agreements for the perpetual operation and maintenance of aeration facilities shall be prepared to the satisfaction of the municipality.
(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 still be sufficient to contain the design year storm runoff.
C. 
Collection and conveyance system design.
(1) 
Storm sewers must be able to convey proposed conditions runoff from a twenty-five-year design storm without flooding inlets, where appropriate.
(2) 
No stormwater conveyance facility shall be constructed within 50 feet of a special geologic feature, unless it is constructed of durable pipe utilizing watertight joints.
(3) 
Storm sewers, culverts, bridges and related installations shall be provided:
(a) 
To permit unimpeded flow of natural watercourses. Such flow may be redirected as required, subject to the approval of PaDEP.
(b) 
To insure adequate drainage of all low points along the line of streets.
(c) 
To intercept stormwater runoff along streets at intervals reasonably related to the extent and grade of the area drained, and to prevent substantial flow of water across intersections or flooded intersections during the specified design storm.
(d) 
To insure adequate and unimpeded flow of stormwater under driveways in, near or across natural watercourses or drainage swales. Suitable pipes or other waterway openings shall be provided as necessary.
(4) 
Storm sewers, as required, shall be placed under or immediately in front of the curb, when parallel to the street within the right-of-way. Generally, locating storm sewers under curbs in curves or at street intersections shall be prohibited. When located in undedicated land, they shall be placed within an easement not less than 20 feet wide as approved by the Township Engineer.
(5) 
Storm sewer systems shall have curb inlets located at curb tangents on the uphill side of street intersections and at other locations as may be required by the Township as necessary to intercept runoff. Design and location of curb inlets shall be in accordance with Pennsylvania Department of Transportation Design Manual Part 2.
(6) 
Storm sewers shall be installed in accordance with the following requirements:
(a) 
All storm sewers shall be constructed per PennDOT Form 408 Specifications and Design Manual, Part 2, Highway Design and Standards for Roadway Construction, unless otherwise directed by the Township.
(b) 
Storm sewers shall have a minimum diameter of 15 inches and a minimum slope of 1/2%.
(c) 
Storm sewers at design flows shall have a minimum velocity of 2.5 fps and a maximum velocity of 12.0 fps.
(d) 
Reinforced concrete pipe is acceptable for all storm sewer construction. Corrugated polyethylene pipe will be permitted for diameters of 15 inches to 36 inches only. Pipe materials shall be subject to approval by the Township.
(e) 
All storm sewer pipe within street cartways or other paved areas shall be bedded and backfilled in accordance with the provisions of the Township of Spring Construction Manual and Standard Specification.
(7) 
Storm sewers shall be designed based upon the following criteria:
(a) 
Any changes in alignment shall be accomplished utilizing straight sections connected by inlets or manholes.
(b) 
When there is a change in pipe size through a structure, the top inside elevation of the outlet pipe shall be at or below the elevations of all incoming pipes.
(c) 
Storm sewers shall be sized to handle the flow anticipated during the twenty-five-year design storm. Where inlets or storm sewers are designed to drain low points in streets or other areas, or wherever stormwater amounts exceeding the capacity of the proposed conveyance facilities would cause potential erosion or damage to property, overflow facilities capable of handling the calculated one-hundred-year flows are required.
(d) 
Storm sewer design shall be based upon PennDOT design methods. Inlet efficiency and bypass flow shall be determined for all inlets, and the gutter flow spread shall not exceed one-half the travel lane width.
(e) 
Where necessary, storm sewers and culverts shall be evaluated for inlet and outlet control restrictions.
(8) 
Inlets shall conform to PennDOT standards. Precast concrete inlets may be used but the Township Engineer must approve these inlets for each project.
(a) 
Inlets shall generally be located at the lowest point of street intersections to intercept the stormwater before it reaches pedestrian crossings or at sag point of vertical curves in the street alignment which provides a natural point of ponding of surface stormwater.
(b) 
At street intersections, inlets shall be placed in the tangent and not the curved portion of the curbing.
(c) 
Inlets shall be designed and located to prevent hazards to vehicles, bicycles and pedestrians.
(d) 
Where the Township deems it necessary because of special land requirements, special inlets may be approved.
(e) 
The interval between inlets serving stormwater runoff flow along the curb shall not exceed a maximum of 1,000 feet when located along any one continuous curbline. More frequent spacing shall be required when the entrance capacity of any individual inlet warrants closer spacing as determined by calculations which incorporate consideration of the area drained, intensity of rainfall, slope or grade, runoff coefficient of imperviousness and cross-sectional rear of the gutter.
(f) 
When inlets are used in a storm system within the right-of-way limits of a street, in lieu of manholes, the spacing of such inlets shall not exceed the maximum distance of 450 feet along any one continuous line.
(9) 
Manholes shall be installed in accordance with the following requirements:
(a) 
The construction locations of manholes shall be as indicated on the subdivision Drainage Plan or area Drainage Plan approved by the governing municipal authorities.
(b) 
Manholes shall be located on a continuous storm sewer system at all abrupt changes of grade, at all locations where a transition in storm sewer pipe sizing is required, at all angle points and at all points of convergence of two or more influent storm sewer mains.
(c) 
Manholes shall not be more than 300 feet apart on sizes up to 24 inches and not more than 450 feet apart on larger sizes. Inlets may be substituted for manholes on approval by the Township.
(10) 
The construction of endwalls shall be required at ends of all stormwater conveyance structures.
(a) 
Special care shall be used by the design engineer to select the proper endwall to fit the condition.
(b) 
The design engineer shall provide energy dissipators at endwalls where the discharge velocity with pipe flowing full is more than one fps.
(11) 
Stormwater roof drains shall not discharge water directly over a sidewalk or into any sanitary sewer line.
(12) 
Bridges and culverts shall have ample waterway to carry expected flows, based on a minimum storm frequency of 25 years. Bridge and/or culvert construction shall be in accordance with the PennDOT specifications and shall meet the requirements of DEP.
(a) 
Culverts shall be provided with wing walls and constructed for the full width of the right-of-way. The cartway area over the bridge shall be 24 inches wider, on either side, than the road connecting with the bridge, or if the character of the road is expected to change for future planning, the cartway of the bridge shall be made to anticipate this condition. On either side of the bridge cartway, the bridge railing must be set back from the edge of the final cartway and this area may be used to place sidewalks, present or future.
(13) 
Provisions shall be made to prevent erosion within watercourses and at points of discharge from storm drainage facilities into watercourses. The velocity of the discharge into a watercourse shall not exceed 0.5 feet/second perpendicular to the axis of the watercourse and 1.0 feet/second parallel to the axis of the watercourse.
(14) 
Design of open channels and swales shall comply with the following:
(a) 
Open ditches will not be permitted but properly designed, graded and turfed drainage swales shall be permitted in lieu of storm sewers, where approved by the Township. Swales shall be located within an easement not less than 20 feet wide, but of sufficient width to allow access for maintenance.
(b) 
Such swales shall be designed not only to carry the required twenty-five-year storm discharge completely contained within the channel bottom and banks without excessive erosion, but also to increase the time of concentration, reduce the peak discharge and velocity and permit the water to percolate into the soil. The minimum grassed swale grade shall be 1% and all swales shall be designed with a minimum six inches of freeboard. For grass swales the minimum design flow velocity shall be (2.0) fps, and PennDOT approved turf reinforcement mat shall be installed where design velocities exceed four fps.
(c) 
Swales shall be designed in accordance with the Channel Design procedures found in the Department of Environmental Protection Bureau of Water Quality Protection, Erosion and Sediment Pollution Control Program Manual.
(d) 
All open channels shall be designed to convey the twenty-five-year stormwater flow. In addition, open channels shall be design to convey the one-hundred-year stormwater flow from emergency spillways and areas where damage to property would result.
(e) 
Open channels located adjacent to streets shall be limited to a top width of six feet, depth of 1.5 feet, and if trapezoidal in cross section, a minimum bottom width of two feet.
D. 
Miscellaneous.
(1) 
All wet basin designs shall incorporate biologic minimization controls consistent with the West Nile Guidance found in Appendix F.
(2) 
Where pervious pavement is permitted for parking lots, recreational facilities, non-dedicated streets, or other areas, pavement construction specifications shall be noted on the plan.
(3) 
Intercepting underdrains shall be required at all locations in which subsurface water is encountered which may permeate or endanger the subgrade of the street. Underdrains shall be required in all cuts three feet deep and greater, and in all other locations stipulated by the Township Engineer. Pipe foundation underdrains shall be parallel to the established street grade to outlet in approved drainage structures. Pipe foundation underdrain shall consist of a trench excavated to a minimum depth of 24 inches below the underneath elevation of the special subgrade and to the minimum width of 18 inches in which a six inch pipe underdrain shall be laid. The trench shall be backfilled with Pennsylvania Department of Transportation 2B aggregate to its full depth around and above the laid pipe.
(4) 
If the length of pipe underdrain exceeds 600 feet in one run, the minimum diameter of six inches shall be increased to eight [inches] beyond that point. Pipe shall meet PennDOT, Form 408 Specifications.