A. 
Applicants proposing regulated activities in the municipality that do not fall under the exemption criteria shown in § 228-6 shall submit a drainage plan consistent with this chapter and the respective Act 167 Stormwater Management Plan to the municipality for review. The stormwater management criteria of this chapter shall apply to the total proposed development even if development is to take place in stages.
B. 
The applicant is required to find practicable alternatives to the surface discharge of stormwater, the creation of impervious surfaces, and the degradation of waters of the commonwealth and must maintain as much as possible the natural hydrologic regime.
C. 
The drainage plan must be designed consistent with the sequencing provisions of § 228-19 to ensure maintenance of the natural hydrologic regime, to promote groundwater recharge, and to protect groundwater and surface water quality and quantity. The drainage plan designer must proceed sequentially in accordance with Article IV of this chapter.
D. 
Stormwater drainage systems shall be designed in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with 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, whether proposed to be concentrated or maintained as diffused drainage areas, shall be subject to any applicable discharge criteria in the general direction of existing discharge, 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 streams, drainage easements shall be provided conforming to the line of such streams. The terms of the easement shall conform to the stream buffer requirements contained in § 228-21G 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 delineated wetlands shall be subject to approval by DEP through the joint permit application or the environmental assessment approval process, or where deemed appropriate, by the DEP general permit process. When there is a question as to 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 DEP.
I. 
Any proposed stormwater management facilities regulated by this chapter that would be located on state highway rights-of-way shall be subject to approval by PennDOT.
J. 
Minimization of impervious surfaces and infiltration of runoff through seepage beds, infiltration trenches, etc., is encouraged where soil conditions permit in order to reduce the size or eliminate the need for detention facilities or other structural BMPs.
K. 
All stormwater runoff shall be pretreated for water quality prior to discharge to surface or ground water.
L. 
All regulated activities within the municipality shall be designed, implemented, operated, and maintained to meet the purposes of this chapter, through these two elements:
(1) 
Erosion and sediment control during earth disturbance activities (e.g., during construction); and
(2) 
Water quality protection measures after completion of earth disturbance activities (i.e., after construction), including operations and maintenance.
M. 
No regulated earth disturbance activities within the municipality shall commence until the requirements of this chapter are met.
N. 
Post-construction water quality protection shall be addressed as required by § 228-21.
O. 
Operations and maintenance of permanent stormwater BMPs shall be addressed as required by Article VII.
P. 
All BMPs used to meet the requirements of this chapter shall conform to the state water quality requirements and any more stringent requirements as set forth by the municipality.
Q. 
Techniques described in Appendix D, Low Impact Development Practices, of this chapter[1] shall be considered because they reduce the costs of complying with the requirements of this chapter and the state water quality requirements.
[1]
Editor's Note: Appendix D is included at the end of this chapter.
R. 
In selecting the appropriate BMPs or combinations thereof, the applicant shall consider the following:
(1) 
Total contributing area.
(2) 
Permeability and infiltration rate of the site's soils.
(3) 
Slope and depth to bedrock.
(4) 
Seasonal high water table.
(5) 
Proximity to building foundations and wellheads.
(6) 
Erodibility of soils.
(7) 
Land availability and configuration of the topography.
(8) 
Peak discharge and required volume control.
(9) 
Stream bank erosion.
(10) 
Effectiveness of the BMPs to mitigate potential water quality problems.
(11) 
The volume of runoff that will be effectively treated.
(12) 
The nature of the pollutant being removed.
(13) 
Maintenance requirements.
(14) 
Creation/protection of aquatic and wildlife habitat.
(15) 
Recreational value.
The following permit requirements may apply to certain regulated earth disturbance activities and must be met prior to commencement of regulated earth disturbance activities, as applicable:
A. 
All regulated earth disturbance activities subject to permit requirements by DEP under regulations at 25 Pennsylvania Code Chapter 102.
B. 
Work within natural drainageways subject to permit by DEP under 25 Pennsylvania Code Chapter 105.
C. 
Any stormwater management facility that would be located in or adjacent to surface waters of the commonwealth, including wetlands, subject to permit by DEP under 25 Pennsylvania Code Chapter 105.
D. 
Any stormwater management facility that would be located on a state highway right-of-way or require access from a state highway shall 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 DEP under 25 Pennsylvania Code Chapter 105.
A. 
No regulated earth disturbance activities within the municipality shall commence until the municipality receives an approval from the Conservation District of an erosion and sediment control plan for construction activities.
B. 
DEP has regulations that require an erosion and sediment control plan for any earth disturbance activity of 5,000 square feet or more, under 25 Pennsylvania Code § 102.4(b).
C. 
In addition, under 25 Pennsylvania Code Chapter 92, a DEP permit for stormwater discharges associated with construction activities is required for land disturbances greater than one acre.
D. 
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or County Conservation District must be provided to the municipality.
E. 
A copy of the erosion and sediment control plan and any required permit, as required by DEP regulations, shall be available on the project site at all times.
F. 
Additional erosion and sediment control design standards and criteria are recommended to be applied where infiltration BMPs are proposed. They 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. Additional measures, such as placement of orange construction fencing around proposed infiltration BMPs during construction to minimize or eliminate traffic overtop of these areas, and temporary sealing off of pipes and inlet connections to infiltration BMPs to prevent sediment clogging should be given consideration.
(2) 
Infiltration BMPs shall not be constructed nor receive runoff until the entire drainage area contributory to the infiltration BMP has achieved final stabilization.
A. 
The design of all regulated activities shall include the following to minimize stormwater impacts:
(1) 
The applicant shall find practicable alternatives to the surface discharge of stormwater, such as those listed in Appendix E, Table E-4,[1] 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]
Editor's Note: Appendix E is included at the end of this chapter.
(2) 
An alternative is practicable if it is available and capable of implementation after taking into consideration existing technology and logistics in light of overall project purposes and other municipal requirements.
(3) 
All practicable alternatives to the discharge of stormwater are presumed to have less adverse impact on quantity and quality of waters of the commonwealth unless otherwise demonstrated.
B. 
The applicant shall demonstrate that the regulated activities were designed in the following sequence. The goal of the sequence is to minimize the increases in stormwater runoff and impacts to water quality resulting from the proposed regulated activity:
(1) 
Prepare an existing resource and site analysis map (ERSAM) showing environmentally sensitive areas, including, but not limited to, steep slopes, ponds, lakes, streams, wetlands, hydric soils, vernal pools, stream buffers, hydrologic soil groups, wooded areas, and potential infiltration areas. Land development, any existing recharge areas, and other requirements outlined in the municipal SALDO shall also be included.
(2) 
Establish a stream buffer according to § 228-21G.
(3) 
Prepare a draft project layout avoiding sensitive areas identified in § 228-19B(1).
(4) 
Identify site-specific existing conditions drainage areas, discharge points, recharge areas, and hydrologic soil groups A and B (areas conducive to infiltration). Infiltration should still be considered in well draining soils listed as hydrologic soil group C, but additional soils testing should be performed to verify onsite conditions and placement of these BMPs.
(5) 
Evaluate nonstructural stormwater management alternatives:
(a) 
Minimize earth disturbance.
(b) 
Minimize impervious surfaces.
(c) 
Break up large impervious surfaces.
(6) 
Satisfy the groundwater recharge (infiltration) objective (§ 228-20) and provide for stormwater pretreatment prior to infiltration.
(7) 
Provide for water quality protection in accordance with § 228-21, Water quality requirements.
(8) 
Provide stream bank erosion protection in accordance with § 228-22, Stream bank erosion requirements.
(9) 
Conduct an existing conditions runoff analysis.
(10) 
Prepare 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 that the remaining site development has no surface or point discharge.
(11) 
Conduct a proposed conditions runoff analysis based on the final design that meets the management district requirements (§ 228-23).
(12) 
Manage any remaining runoff prior to discharge through detention, bioretention, direct discharge, or other structural control.
Maximizing the groundwater recharge capacity of the area being developed is required. Design of the infiltration facilities shall consider groundwater recharge to compensate for the reduction in the recharge that occurs when the ground surface is disturbed or impervious surface is created. It is recommended that roof runoff be directed to infiltration BMPs that may be designed to compensate for the runoff from parking areas. These measures are required to be consistent with § 228-3 and to take advantage of utilizing any existing recharge areas. Infiltration may not be feasible on every site due to site-specific limitations such as soil type. If it cannot be physically accomplished, then the design professional shall be responsible to show that this cannot be physically accomplished, to the satisfaction of the Municipal Engineer. Appropriate soils testing and/or geotechnical evaluation should be included as part of any documentation for infiltration BMPs. If it can be physically accomplished, the volume of runoff to be infiltrated shall be determined from § 228-20A(2).
A. 
Infiltration BMPs shall meet the following minimum requirements:
(1) 
Infiltration BMPs intended to receive runoff from developed areas shall be selected based on suitability of soils and site conditions and shall be constructed on soils that have the following characteristics:
(a) 
A minimum depth of 24 inches, between the bottom of the BMP and the top of the limiting zone (e.g., SHWT, groundwater, bedrock, etc.).
(b) 
An infiltration rate sufficient to accept the additional stormwater load and dewater completely as determined by field tests conducted by the applicant's design professional.
(c) 
The infiltration facility shall be capable of completely infiltrating the recharge (infiltration) volume (Rev) within three days (72 hours) or less.
(d) 
Pretreatment shall be provided prior to infiltration.
(2) 
The size of the infiltration facility shall be based upon the net two-year volume approach, where the recharge (infiltration) volume (Rev) to be captured and infiltrated shall be the volume difference between the pre-development two-year, twenty-four-hour storm event and post-development two-year, twenty-four-hour storm event. The recharge volume calculated using this section is the minimum volume the applicant must control through an infiltration BMP facility. However, if a site has areas of soils where additional volume of recharge can be achieved, the applicant is encouraged to infiltrate as much of the stormwater runoff from the site as possible.
B. 
Soil testing. If on-lot infiltration is proposed as part of a project, the applicant's design professional must demonstrate to the satisfaction of the municipality that the soils are conducive to infiltration at the proposed location of the infiltration facilities. Soil testing shall be completed as follows:
(1) 
Soil testing must be conducted by a qualified design professional and at a minimum shall address depth to limiting zone, soil permeability, and subgrade stability. Soil testing must be observed by the Municipal Engineer or a municipal representative. The Municipal Engineer shall be provided a minimum of 48 hours' notice prior to the start of soil testing to arrange for proper inspection.
(2) 
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 may not be ruled out without conducting these tests.
(3) 
Conduct field testing, including test pits to determine soil horizons and depth to limiting zone and permeability tests, at the elevation of the proposed infiltration facility surface, to determine the appropriate hydraulic conductivity rate. Double ring infiltrometer or hydraulic conductivity tests should be used to determine soil permeability (percolation tests are not permitted for design purposes). Site evaluation and soils testing should be conducted in accordance with Appendix C of the Pennsylvania Stormwater Best Management Practices Manual.
(4) 
The proposed infiltration facilities shall be designed for the required recharge (Rev) volume based on the field determined capacity at the surface elevation of the proposed infiltration facility. The applicant should incorporate design guidelines from the Pennsylvania Stormwater Best Management Practices Manual as required by the Municipal Engineer.
C. 
Stormwater hotspots. Below 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. The Environmental Protection Agency's (EPA) NPDES stormwater program requires some industrial sites to prepare and implement a stormwater pollution prevention plan.
(1) 
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 Codes.
(g) 
Marinas (service and maintenance).
(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) 
Other land uses and activities as designated by an appropriate review authority.
(2) 
The following land uses and activities are not normally considered hotspots:
(a) 
Residential streets and rural highways.
(b) 
Residential development.
(c) 
Institutional development.
(d) 
Office developments.
(e) 
Nonindustrial rooftops.
(f) 
Pervious areas, except golf courses and nurseries [which may need an integrated pest management (IPM) plan].
(3) 
While large highways [average daily traffic volume (ADT) greater than 30,000] are not designated as stormwater hotspots, it is important to ensure that highway stormwater management plans adequately protect groundwater.
D. 
Extreme caution shall be exercised where infiltration is proposed in SWPAs as defined by the local municipality or water authority.
E. 
Infiltration facilities shall be used in conjunction with other innovative or traditional BMPs, stormwater control facilities, and nonstructural stormwater management alternatives.
F. 
Extreme 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. Specific consideration should be given to the particular type of salt or deicing material to be used within this watershed in regards to its potential long-term effects on the soils, especially in areas that contain clay soil.
G. 
The infiltration requirement in HQ or EV waters shall be subject to the Department's Chapter 93 Antidegradation Regulations.
H. 
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 municipality.
I. 
The municipality 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.
J. 
Infiltration design criteria.
(1) 
All infiltration systems shall have appropriate positive overflow controls to prevent storage within one foot of the finished surface or grade.
(2) 
All infiltration systems shall have a minimum setback of 20 feet from principal structures, 10 feet from property lines, 100 feet from wells, and 50 feet from septic system drain fields. Care should be taken to prevent any seepage into subgrade structures.
(3) 
Surface inflows shall be treated to prevent the direct discharge of sediment and pollutants into the infiltration system; accumulated sediment reduces stormwater storage capacity and ultimately clogs the infiltration mechanism.
(4) 
During site construction, all recharge system components shall be protected from compaction due to heavy equipment operation or storage of fill or construction material. Recharge areas shall be protected from sedimentation. All areas designated for recharge shall not receive runoff until the contributory drainage area has achieved final stabilization. Construction fencing shall be installed around recharge areas during construction activities.
(5) 
The following procedures and materials shall be required during the construction of all subsurface facilities:
(a) 
Excavation for the infiltration facility shall be performed with equipment which will not compact the bottom of the seepage bed/trench, or like facility.
(b) 
The bottom of the bed and/or trench shall be scarified prior to the placement of aggregate.
(c) 
Only clean aggregate, free of fines, shall be allowed.
(d) 
The top and sides of all seepage beds, trenches, or like facilities shall be covered with drainage filtration fabric. Fabric shall meet the specifications of PennDOT Publication 408, Section 735 Construction Class 1.
(e) 
Perforated distribution pipes connected to centralized catch basins and/or manholes with provision for the collection of debris shall be provided in all facilities. The perforated pipes shall distribute stormwater throughout the entire seepage bed/trench, or like facility.
(6) 
All infiltration facilities which service more than one lot and are considered a common facility shall have an easement provided to the Township for future access if necessary.
(7) 
No more than 50% of the required infiltration volume may be provided in detention basin bottoms. The remaining 50% of infiltration volumes shall be provided at or near the proposed impervious coverage.
The applicant shall comply with the following water quality requirements of this article:
A. 
No regulated earth disturbance activities within the municipality shall commence until approval by the municipality of a plan that demonstrates compliance with post-construction state water quality requirements.
B. 
The BMPs shall be designed, implemented, and maintained to meet state water quality requirements and any other more stringent requirements as determined by the municipality.
C. 
To control post-construction stormwater impacts from regulated earth disturbance activities, state water quality requirements can be met by BMPs, including site design, which provide for replication of pre-construction stormwater infiltration and runoff conditions so that post-construction stormwater discharges do not degrade the physical, chemical, or biological characteristics of the receiving waters. As described in the DEP Comprehensive Stormwater Management Policy (#392-0300-002, September 28, 2002), this may be achieved by the following:
(1) 
Infiltration: replication of pre-construction stormwater infiltration conditions;
(2) 
Treatment: use of water quality treatment BMPs to ensure filtering out of the chemical and physical pollutants from the stormwater runoff; and
(3) 
Stream bank and stream bed protection: management of volume and rate of post-construction stormwater discharges to prevent physical degradation of receiving waters (e.g., from scouring).
D. 
Developed areas shall provide adequate storage and treatment facilities necessary to capture and treat stormwater runoff. If site conditions allow for infiltration, the water quality volume and the recharge volume are the same volume and may be managed in a single facility. If infiltration cannot be physically accomplished, the water quality volume should be calculated using the net two-year volume approach described in § 228-20A(2). In this case, the water quality volume may be captured and treated by methods other than infiltration BMPs.
(1) 
This volume requirement can be accomplished by the detained volume of wet basins and other BMPs. Only the detained volume of water above the permanent pool elevation in a wet basin can be utilized. Where appropriate, wet basins shall be utilized for water quality control and shall follow the guidelines of the BMP manuals referenced in Appendix F.[1]
[1]
Editor's Note: Appendix F is included at the end of this chapter.
(2) 
The water quality volume shall take a minimum of 24 hours to be discharged from a BMP facility. Release of the water quality volume 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.
E. 
For areas within defined special protection subwatersheds that include EV and HQ waters, the temperature and quality of water and streams shall be maintained through the use of temperature sensitive BMPs and stormwater conveyance systems.
F. 
To accomplish the above, the applicant shall submit original and innovative designs to the Municipal Engineer for review and approval. Such designs may achieve the water quality objectives through a combination of different BMPs.
G. 
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 and encouraged to use appropriate native vegetation (refer to Appendix B of the Pennsylvania Stormwater Best Management Practices Manual, latest version, for plant lists). 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.
H. 
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office must be provided to the municipality. The issuance of an NPDES construction permit [or permit coverage under the statewide general permit (PAG-2)] satisfies the requirements of § 228-21A.
A. 
In addition to the control of water quality volume (in order to minimize the impact of stormwater runoff on downstream stream bank 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 flow using the SCS Type II distribution. Additionally, provisions shall be made (such as adding a small orifice at the bottom of the outlet structure) so that the proposed conditions one-year storm takes a minimum of 24 hours to drain from the facility from a point where the maximum volume of water from the one-year storm is captured (i.e., the maximum water surface elevation is achieved in the facility). 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 three inches in diameter where possible, and a trash rack shall be installed to prevent clogging. On sites with small drainage areas contributing 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. 
Peak runoff control shall be designed to reduce the post-development peak flow to 50% of the pre-development peak flow. Development sites must control proposed conditions runoff rates to 50% of the existing conditions runoff rates for the two- , five- , ten- , twenty-five- , fifty- and one-hundred-year storm events.
B. 
The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea.
C. 
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.
D. 
Site areas. Where the site area to be impacted by a proposed development activity is less than 50% of the total site area, only the proposed impact area utilizing stormwater management measures shall be subject to the peak rate control standards noted above.
E. 
Alternate criteria for redevelopment sites. For redevelopment sites, one of the following minimum design parameters shall be accomplished, whichever is most appropriate for the given site conditions as determined by the municipality:
(1) 
Meet the full requirements specified by Subsections A through D.
(2) 
Reduce the total impervious surface on the site by at least 20%, based upon a comparison of existing impervious surface to proposed impervious surface.
A. 
Stormwater runoff from all development sites with a drainage area of greater than five acres shall be calculated using a generally accepted calculation technique that is based on the NRCS Soil Cover Complex Method. Table 2 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 municipality may allow the use of the Rational Method to estimate peak discharges from drainage areas that contain less than five acres.
Table 2
Acceptable Computation Methodologies for Stormwater Management Plans
Method
Developed By
Applicability
TR-55 (or commercial computer package based on TR-55)
USDA NRCS
Applicable for land development plans within limitations described in TR-55
Rational Method (or commercial computer package based on Rational Method)
Emil Kuichling (1889)
For sites less than 5 acres, or as approved by the municipality and/or Municipal Engineer
Other methods
Varies
Other computation methodologies approved by the municipality and/or Municipal Engineer
B. 
All calculations consistent with this chapter using the Soil Cover Complex Method shall use the appropriate design rainfall depths for the various return period storms according to the region in which they are located as presented in Table E-1 in Appendix E of this chapter.[1]
[1]
Editor's Note: Appendix E is included at the end of this chapter.
C. 
The following criteria shall be used for runoff calculations:
(1) 
For development sites not considered redevelopment, the ground cover used in determining the existing conditions flow rates shall be as follows:
(a) 
Wooded sites shall use a ground cover of "woods in good condition." A site shall be considered to be a wooded site where a biological community dominated by trees and other woody plants exists that covers an area of 10,000 square feet or more, and contains at least 100 trees with at least 50% of those trees having a dbh of two inches or greater. (Duerksen, Christopher J., with Suzanne Richman, Tree Conservation Ordinances, Planning Advisory Service Report Number 446, American Planning Association, Chicago, Illinois, and Scenic America, Washington, D.C., August, 1993.)
(b) 
The undeveloped portion of the site, including agriculture, bare earth, and fallow ground, shall be considered as "meadow in good condition," unless the natural ground cover generates a lower curve (CN) number or Rational "c" value (i.e., woods) as listed in Tables E-2 or E-3 in Appendix E of this chapter.[2]
[2]
Editor's Note: Appendix E is included at the end of this chapter.
(c) 
Offsite land use conditions used to determine storm flows for designing storm facilities shall be based on existing land uses assuming winter or poor land cover conditions.
(2) 
For development considered redevelopment sites, the ground cover used in determining the existing conditions flow rates for the developed portion of the site shall be based upon actual land cover conditions.
D. 
All calculations using the Rational Method shall use rainfall intensities consistent with appropriate times-of-concentration for overland flow and return periods presented in the appropriate curves from the PennDOT Storm-Duration-Frequency Chart (Region 4 is included as Figure E-3-A. The user should refer to the Atlas 14, Volume 2, Storm-Duration-Frequency Chart). Times-of-concentration for overland flow shall be calculated using the methodology presented in Chapter 3 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as amended or replaced from time to time by NRCS). Times-of-concentration for channel and pipe flow shall be computed using Manning's equation.
E. 
Runoff curve numbers (CN) for both existing and proposed conditions to be used in the Soil Cover Complex Method shall be obtained from Table E-2 in Appendix E of this chapter.
F. 
Runoff coefficients (c) for both existing and proposed conditions for use in the Rational Method shall be obtained from Table E-3 in Appendix E of this chapter.
G. 
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 in accordance with Table E-5 in Appendix E.
H. 
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.
I. 
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. The design storm hydrograph shall be computed using a calculation method that produces a full hydrograph. The municipality may approve the use of any generally accepted full hydrograph approximation technique that shall use a total runoff volume that is consistent with the volume from a method that produces a full hydrograph.
A. 
All wet basin designs shall incorporate biologic controls consistent with the West Nile Guidance found in Appendix G.[1]
[1]
Editor's Note: Appendix G is included at the end of this chapter.
B. 
Any stormwater management facility (i.e., detention 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 handle flow up to and including the one-hundred-year proposed conditions. The emergency spillway shall be designed assuming no storage volume is available below the emergency spillway crest elevation. The height of embankment must provide a minimum one foot of freeboard above the maximum elevation computed when the flow is passing over the emergency spillway. Should any stormwater management facility require a dam safety permit under DEP Chapter 105, the facility shall be designed in accordance with Chapter 105 and meet the regulations of Chapter 105 concerning dam safety. Chapter 105 may be required to pass storms larger than the one-hundred-year event.
C. 
Any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures) and any work involving wetlands governed by DEP Chapter 105 regulations (as amended or replaced from time to time by DEP) shall be designed in accordance with Chapter 105 and will require a permit from DEP.
D. 
Any other drainage conveyance facility that does not fall under Chapter 105 regulations must be able to convey, without damage to the drainage structure or roadway, runoff from the one-hundred-year design storm with a minimum one foot of freeboard measured below the lowest point along the top of the roadway. Any facility that constitutes a dam as defined in DEP Chapter 105 regulations may require a permit under dam safety regulations. Any facility located within a PennDOT right-of-way must meet PennDOT minimum design standards and permit submission requirements.
E. 
Any drainage conveyance facility and/or channel not governed by Chapter 105 regulations must be able to convey, without damage to the drainage structure or roadway, runoff from the one-hundred-year design storm. Conveyance facilities to or exiting from stormwater management facilities (i.e., detention basins) shall be designed to convey the design flow to or from that structure. Roadway crossings must be able to convey runoff from a one-hundred-year design storm, while providing a minimum one foot of freeboard measured below the lowest point along the top of the roadway. Any facility located within a PennDOT right-of-way must meet PennDOT minimum design standards and permit submission requirements.
F. 
Storm sewers must be able to convey proposed conditions runoff from a one-hundred-year design storm without surcharging inlets.
G. 
Adequate erosion protection shall be provided along all open channels and at all points of discharge.
H. 
The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The municipality reserves the right to disapprove any design that would result in construction in or continuation of a stormwater problem area.
The following criteria shall be used for the design of detention and wet basins. Any reference to a "detention basin" shall also include a "wet basin."
A. 
Basin setback. Basin setback is to be measured from the elevation of the one-hundred-year routed water surface elevation. The following basin setbacks are to be considered minimums. Any basin setback criteria outlined in other sections and considered to be more restrictive than the information mentioned below shall govern. The following setbacks are required for stormwater management facilities:
(1) 
Stormwater retention or detention basins shall be located at least 50 feet from any structure, whether existing or proposed.
(2) 
Stormwater retention or detention basins shall be located at least 50 feet from any property line or right-of-way.
(3) 
Stormwater retention or detention basins shall be located at least 50 feet from existing wetlands, or the banks of existing streams.
B. 
Outlet structure. An outlet structure shall be utilized to regulate water flow at all detention basin locations. The outlet structure shall be constructed of precast or poured in place concrete with controlled orifices. The outlet structure shall be constructed to provide a minimum of two feet between the top of the outlet structure and the crest elevation of the emergency spillway. The height of the outlet structure shall be designed such that no flow enters the top of the structure for the one-hundred-year storm event. A trash rack shall be provided to prevent debris from entering the outlet structure. All outlet structures shall have a concrete base attached with a watertight connection. The base shall extend three feet below the bottom of the basin elevation. All outlet structure connections are to be watertight. All outlet structures are to be one-piece units with low-flow channels installed.
C. 
Emergency spillway. Whenever possible, the emergency spillway for detention basins shall be constructed on undisturbed ground. Emergency spillways shall be constructed of reinforced concrete checker blocks or other permanent material, if approved by the Township Engineer. All emergency spillways shall be constructed so that the detention basin berm is protected against erosion. Emergency spillway erosion protection shall extend along the upstream and downstream berm embankment slopes. The protection for the upstream edge of the emergency spillway shall be installed a minimum of two feet below the spillway crest elevation. The protection for the downstream edge of the spillway shall, at a minimum, extend to the toe of the berm embankment slope. The emergency spillway shall not discharge over earthen fill and/or easily erodible material. The design depth across the emergency spillway shall not exceed six inches. The minimum capacity of the emergency spillway shall be designed to equal the peak flow rate from the one-hundred-year basin captured design storm. The capacity of the emergency spillway must consider the outlet structure to be blocked as well as no volume being available below the emergency spillway crest elevation.
D. 
Antiseep collars. Antiseep collars shall be installed around the basin outfall pipe barrel within the normal saturation zone of the detention basin berm. The antiseep collars and their connections to the pipe barrel shall be watertight. The antiseep collars shall extend a minimum of two feet beyond the outside of the basin outfall pipe barrel. The maximum spacing between collars shall be 14 times the minimum projection of the collar measured perpendicular to the pipe. A minimum of two antiseep collars shall be installed on each pipe outlet. The antiseep collars shall be a minimum of eight inches in thickness.
E. 
Freeboard. Freeboard is the difference between the design flow elevation over top of the emergency spillway and the top of the detention basin berm. The minimum freeboard shall be one foot.
F. 
Width of berm. The minimum top width of detention basin berms shall be 10 feet.
G. 
Slope of basin bottom. In order to insure proper drainage of the detention basin, a minimum grade of 2% shall be maintained for all sheet flow. A minimum grade of 1% shall be maintained for all channel flow. Under certain circumstances, such as continuous seasonal flow, the Township may require a low flow channel to be constructed. These standards do not apply, if approved by the Township Engineer, if the basin is to be utilized for infiltration or as a biofiltration device.
H. 
Energy dissipaters. Energy dissipating devices (rip-rap aprons, impact stilling basins, etc.) shall be placed at all basin outlet locations. Any pipe or other component which discharges directly into the basin shall be equipped with an energy dissipating device and shall outlet into the bottom of the basin. Impact stilling basins shall be utilized in all applicable areas unless approved otherwise by the Township Engineer.
I. 
Landscaping and grading of detention basins. All landscaping and grading standards shall be as follows:
(1) 
Cuts. No excavation shall be made with a cut face steeper than three horizontal to one vertical. Retaining walls are permitted in basin cut areas. Retaining wall designs must be approved by the Township Engineer. The top of the slope or headwall of any cut must be located a minimum of 25 feet from property lines.
(2) 
Fills. No fills shall be made which create any exposed surfaces steeper in slope than three horizontal to one vertical. Retaining walls are not permitted in basin fill areas. The top of any fill or toe of the slope of any fill shall be located 25 feet from any property line with the exception of a downstream property line where the toe of the embankment shall be placed a sufficient distance, as determined by the Township Engineer, to allow for energy dissipating devices, but in no case less than 25 feet.
(3) 
Planting requirements. All areas proposed for recreational use, whether active or passive, shall be planted to effectively naturalize the areas to become an integral and harmonious element in the natural landscape. Whenever possible, the side slopes and basin shape shall be amendable to the natural topography. Straight side slopes and rectangular basins shall be avoided. The planting of trees in basin embankment areas is prohibited.
(4) 
Drainage channels and retention areas. All storm drainage channels and retention areas, whether existing or proposed, shall be graded and planted to effectively naturalize areas so as to become an integral and harmonious part of the landscape by contour and type of plant material employed.
(5) 
Fence or screening. A fence or suitable vegetation screen shall be provided around all detention basins as required by the Township. Fencing and gates shall be a type approved by the Township, a minimum of four feet in height with locking gates. Each basin shall be provided with a minimum of two gates, one wide enough for maintenance vehicles and a second gate for pedestrian access. All vegetative screening shall be at least 3 1/2 feet in height and shall be composed of the following shrubs: Barberry (Barberis species); Eleagnus (Eleagnus species); Firethorn (Pyracantha species); or Rose (Rose species). All vegetative screening shall provide a barrier to prevent entrance to the detention basin area and planted in such a way as to gain the approval of the Township. The fencing or vegetative screening requirement shall be waived only upon Township approval.
J. 
Basin location.
(1) 
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 basins. The Township may require a detailed hydrogeologic investigation.
(2) 
The municipality may require the developer to provide safeguards against groundwater contamination for uses, which may cause groundwater contamination, should there be a mishap or spill.
(3) 
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 developer's engineer/surveyor/landscape architect/geologist:
______________________, represents that the proposed detention basin is/is not (circle one) underlain by limestone.
K. 
Basin outfall pipe. All basin outfall pipes shall contain rubber-gasketed-style joints as utilized and meeting the requirements of the Pennsylvania Department of Transportation.
L. 
Embankment placement. All detention basin embankments shall be placed at a maximum of eight-inch lifts to a minimum of 95% of maximum dry density as established by ASTM D-1557. Prior to proceeding to the next lift, the compaction shall be checked by the Township Engineer or the Soils Engineer. The developer's contractor shall obtain the services of a qualified laboratory technician to conduct compaction tests on the leading and the trailing edge of the berm along with the top of berm. All tests shall be furnished to the Township for review.
M. 
Key trench. A key trench (cutoff trench) of impervious material shall be provided under all embankments that require fill material. The key trench shall be a minimum of eight feet wide, two feet below existing grade, a minimum of two feet above the top of the pipe and have side slopes of 1:1. The key trench must be constructed with soils suitable for this application and found to be acceptable by the Township Engineer. Proper compaction techniques acceptable to the Township Engineer are to be utilized during construction.
N. 
Trash rack. A trash rack shall be installed on all outlet structures. Trash racks are to be constructed of #5 rebar with a 3/8 inch by 1.5 inch flat steel anchoring frame. The rebar is to be constructed at six inches on center in either direction. All rebar crossings are to be welded. The trash rack is to be mounted to the outlet structure using four-inch bolts with concrete anchors at a maximum of twelve-inch spacing. The trash rack is to be triple coated with a rust-prohibitive coating. All hardware is to be stainless steel. The trash rack is to be sized to allow a minimum of six inches of clearance around any orifice located on the outlet structure. Trash racks are to be a minimum of 18 inches in depth.
O. 
Wet basins. Permanent plantings for wet ponds shall be designed by a wetland biologist to have a mixture of plants that thrive in wet areas.
P. 
Easements. Easements for all basins and storm pipes not located within the public street right-of-way shall be provided.
Q. 
Miscellaneous. The following items listed below shall be submitted to the Township for review. Any reference to a "detention basin" shall also include a "wet basin."
(1) 
Design computations for the sizing of the outlet structure.
(2) 
A stage-storage discharge curve for the detention/wet basin.
(3) 
Flood routing and/or storage requirement calculations.
(4) 
A cross-section through the basin embankment berm. The detail shall indicate top of berm elevations, top of berm width, emergency spillway and lining, side slopes, outlet structure, trash rack, routed one-hundred-year water surface elevation, outfall pipe, key trench, antiseep collars, energy dissipater, basin bottom and other information found to be necessary by the Township Engineer.
(5) 
A separate detail illustrating all necessary outlet structure information.
(6) 
A separate detail illustrating all necessary emergency spillway information.
(7) 
A separate detail illustrating all necessary trash rack information.
(8) 
Any other calculations or details determined to be necessary by the Township Engineer.
The following criteria shall be used for the design of stormwater drainage systems:
A. 
Design flow rate. The storm drain system as well as sump conditions shall be designed to carry a one-hundred-year peak flow rate without surcharging the structure. The design one-hundred-year peak flow rate for each inlet shall be indicated on the stormwater management plan. The flow rate shall be determined by the rational formula:
Q = CIA
Where:
Q
=
Peak runoff rate, cubic feet per second (cfs)
C
=
Runoff coefficient equal to the ratio of the runoff rate to the average rate of rainfall over a time period equal to the time of concentration
I
=
Average rainfall intensity to inches per hour for a time equivalent to the time of concentration
A
=
Drainage area in acres
Appropriate values for runoff coefficients and rainfall intensities are found in Appendix E, Table E-3 entitled "Rational Runoff Coefficients."[1]
[1]
Editor's Note: Appendix E is included at the end of this chapter.
B. 
Overflow system. An overflow system shall be provided to carry flow to the detention basin when the capacity of the storm drainpipe system is exceeded or structures become blocked. The overflow system shall be of sufficient capacity to carry the one-hundred-year peak flow rates.
C. 
Inlet capacity. All inlets must be designed to accommodate the one-hundred-year peak flow rate. Inlets shall be spaced to limit the gutter spread to no more than 1/2 of the width of the travel lane during the ten-year storm. Inlets shall be sumped no more than one inch in depth at gutter face. The capacity of all C, M, or S type inlets shall be determined from the following source:
Commonwealth of Pennsylvania
Department of Transportation
Design Manual, Part 2
Highway Design
D. 
Straight pipe selections. Wherever possible, all storm drainpipes shall be designed to follow straight courses. No angular deflections of stormwater pipe sections shall be permitted. No vertical curves shall be permitted in the storm drainpipe system.
E. 
Minimum grade and size. All storm drainpipes shall be designed to maintain a minimum grade of 1/2%. All storm pipes shall have a minimum inside diameter of 15 inches, except that pipes under a twenty-five-foot or greater fill shall not be less than 24 inches.
F. 
Pipe material. All storm sewers shall be a Class III reinforced concrete pipe material with rubber-gasketed joints, which meets the one-hundred-year life expectancy criteria as defined by the Pennsylvania Department of Transportation.
G. 
Pipe capacity. The capacity of all pipe culverts shall be calculated as outlined by the following source:
United States Department of Commerce
Bureau of Public Roads
Hydraulic Engineering Circular No. 5
Hydraulic Charts for the Selection of Highway Culverts
H. 
Elliptical pipe/pipe arches. Where headroom is restricted, elliptical pipe or equivalent pipe arches may be used in lieu of circular pipes. If elliptical pipe or pipe arches are chosen, appropriate structural information and/or calculations must be submitted to the Township Engineer to gain approval.
I. 
Allowable headwater depth. At all inlets or manholes, the maximum allowable headwater depth shall be six inches below the top of the inlet grate or manhole cover.
J. 
Horizontal pipe deflections. A manhole or inlet shall be provided at all horizontal deflections in the storm pipe system. In order to maximize hydraulic efficiency in inlets, the angle between inflow and out flow pipes shall not be less than 90°, unless approved by the Township Engineer.
K. 
Minimum and maximum cover. A minimum of 24 inches of cover shall be maintained over all storm drainpipes. The top of storm drainpipes shall be at least six inches below subgrade elevation.
L. 
Pipe discharge into basins. Storm pipe systems shall be designed to discharge at the basin's bottom or at the permanent pool elevation for wet basins. No discharge at the top or side of basin embankments is permitted.
M. 
Energy dissipaters. Energy dissipating devices (rip-rap aprons, impact stilling basins, etc.) shall be placed at all pipe end treatments. Impact stilling basins shall be utilized in all applicable areas unless approved otherwise by the Township Engineer.
N. 
Drainage easements. Drainage easements shall be provided to accommodate all storm drainage systems and shall be a minimum of 20 feet in width. Easements shall be provided for all watercourses and storm drainage piping that are not located within street rights-of-way. Storm drainage pipes are not permitted under buildings or structures.
O. 
Culverts and drainage channels.
(1) 
Design flow standards. All culverts and drainage channels shall be designed to carry a flow rate equal to a one-hundred-year, twenty-four-hour storm (NRCS, Soil Conservation Service, Technical Release No. 55).
(2) 
Erosion prevention.
(a) 
All drainage channels shall be designed to prevent the erosion of the bed and bank areas. The flow velocity in all vegetated drainage channels shall not exceed three feet per second to prevent erosion unless special provisions are made to protect banks and channel bottoms against erosion. Suitable bank stabilization shall be provided where required to prevent erosion of the drainage channels.
(b) 
Where storm sewers discharge into existing drainage channels at an angle greater than 30° from parallel with the downstream channel flow, the far side bank shall be stabilized by the use of rip-rap, masonry and/or concrete walls. The stabilization shall be designed to prevent erosion and frost heave under and behind the stabilizing media.
(3) 
Maximum side slope. Any vegetated drainage channel requiring mowing of the vegetation shall have a maximum grade of three horizontal to one vertical of those areas to be mowed.
(4) 
Design standard. Because of the critical nature of the vegetated drainage channels, the design of all vegetated channels shall, at a minimum, conform to the design procedures outlines in the PADEP manuals. Several acceptable sources outline procedures for nonvegetated drainage channels, including the following:
(a) 
Bureau of Public Roads.
(b) 
Hydraulic Engineering Circular No. 5.
(c) 
Hydraulic Charts for the Selection of Highway Culverts.
(d) 
Federal Highway Administration.
(e) 
Hydraulic Engineering Circular No. 13.
(f) 
Hydraulic Design of Improved Inlets for Culverts.
(5) 
Reference to publications and source documents in this section shall be deemed to include any amendments and revisions thereof.
P. 
Manholes, inlets and endwalls. Manholes, inlets, and endwalls shall be constructed to the requirements of PennDOT Specifications, Publication 408, Section 605 and the latest details of the PennDOT standards for roadway construction, these specifications and the Township Standard Construction Details. All stormwater management structures must be supplied by a PaDOT Bulletin 15 approved supplier. These requirements must be stated on the approved plans.
(1) 
Concrete structures.
(a) 
Manholes, inlets and endwalls shall be constructed of concrete, built on prepared foundations, conforming to the dimensions and form indicated on the plans. The construction shall conform to the methods, forms, mixture, placement, and curing, as specified in PennDOT Specifications, Publication 408, Section 704, unless Township procedures are provided. Any reinforcement required shall be of the kind, type, and size, and shall be furnished, located, spaced, bent, and fastened as indicated on the plans or mentioned in Publication 408, and shall be reviewed by the Engineer before the concrete is poured. Inlet tops shall contain a warning that no dumping is permitted, and that the structure drains to a waterway, in accordance with applicable NPDES Stormwater Permit requirements. Type "C" inlet tops must contain a thirty-six-inch by five-inch cast aluminum plate containing the following language "NO DUMPING . . . DRAINS TO WATERWAY". The text is to be black with the entire plate being clear-coated for protection. The plate should be attached to the inlet hood with an appropriate epoxy.
(b) 
All low-flow channels shall be installed and shaped accurately so as to be smooth, uniform, and cause minimum resistance to flow. The sides of the low-flow channel shall extend up the side of the inlet a minimum of 12 inches. The surface of the bottom slab shall be sloped downward toward the outlet.
(2) 
Manholes.
(a) 
All manholes, which are less than seven feet from top of manhole to invert, shall be constructed with "flat slab" top sections in lieu of the standard conical-shaped top sections.
(b) 
The base slab shall consist of reinforced concrete mixed prepared, and placed in accordance with the requirements of the PennDOT Specifications as set forth in Publication 408, unless Township procedures are provided. It shall be built to the correct elevation, and shall be finished to cause the least possible resistance to flow. The invert may be formed directly in the concrete of the manhole base, or be constructed by laying half sections of pipe through the manhole and casting the concrete base around the pipe. The base slab shall be a minimum of 12 inches thick below the pipe.
(c) 
All castings shall be true to form and dimensions, and shall be free from inclusions of foreign material, casting faults, injurious blow holes, cracks, sponginess, and other defects rendering them unsuitable.
(d) 
The finished frame and cover or grate shall have the surfaces machined or ground so that there will be no variation that will permit rocking or rattling, and the diameter of the cover or grate shall be such as to fit the frame without wedging: All castings shall be thoroughly cleaned and given one coat of Hydrocide 648 or equal. The words "UPPER FREDERICK TOWNSHIP" and the word "STORM" in two-inch letters shall be cast into the manhole cover. Manhole covers shall also contain a warning in one-inch (minimum) lettering that no dumping is permitted, and that the structure drains to waterways, in accordance with applicable NPDES Stormwater Permit requirements. The following language shall be used: "NO DUMPING . . . DRAINS TO WATERWAY".
(e) 
Manhole castings shall have a lid with a diameter of 24 3/4 inches placed in a frame opening diameter of 25 inches.
(f) 
Grates for inlets shall be bicycle safe as detailed in PennDOT Standard for Roadway Construction Steel Grate - Bicycle Safe.
(3) 
Inlets. At street intersections, inlets shall be placed to prevent the flow of water across intersections. When there is a change in pipe size in the inlet, the elevation of the top of pipes shall be the same or the smaller pipe higher. A minimum drop of 0.2 of one foot shall be provided between the inlet pipe invert elevation and the outlet pipe invert elevation.
(4) 
Endwalls. Pipe end sections and/or headwalls shall be utilized at all terminated pipe segments.
(5) 
Manhole, inlet and endwall spacing. When proposed, manholes, inlets and endwalls shall not be spaced more than 400 feet apart for pipes of less than or equal to 24 inches in diameter and 500 feet apart for pipes of greater than 24 inches in diameter. Additionally, manholes or inlets shall be placed at all changes in alignment, grade or pipe size, and at all points of convergence of two or more influent storm sewer lines. Inlets may be substituted for manholes where they will serve a useful purpose.
(6) 
Steps. All manholes and inlets greater than four feet in depth shall be provided with steps. Steps shall conform to PennDOT Publication 408, Section 605 and be made of aluminum, nondeterioration material, or galvanized steel. Steps of aluminum shall be protected from galvanic reaction between the aluminum and the concrete.
Q. 
Swales. Properly designed, graded and lined drainage swales may be permitted in lieu of storm sewers in commercial, industrial and residential areas where approved by the Township. Swales are to be designed to carry the one-hundred-year peak flow rate. Swale lining must meet the County Soil Conservation design standards. All drainage channels shall have a maximum side slope grade of three horizontal to one vertical. All drainage swales shall be provided with a minimum of 12 inches of freeboard, measured from the top of the design storm flow to the top of the swale.
R. 
Pavement base drain. Pavement base drains shall be provided in areas delineated as having a "seasonal high water table" or in areas deemed necessary by the Township Engineer during the design or construction phase of the project. The installation of the underdrain system shall be approved by the Township Engineer and paid for by the developer. Pavement base drains shall be constructed in accordance with PennDOT Pub. 408, Section 610, as amended. Appropriate construction details must be provided on the construction detail sheet to gain Township Engineer approval.
S. 
PennDOT right-of-way. All drainage structures located within a state highway right-of-way shall be reviewed and approved by the Pennsylvania Department of Transportation (PennDOT). A letter from PennDOT indicating such approval shall be submitted to the Township prior to municipal approval.
T. 
Other requirements. At the direction of the Township, in situations where the design standards or ordinance requirements contained within this section do not adequately address stormwater management concerns for the given site conditions, the Township may require the applicant provide additional and/or alternative design methods to meet the objectives of this chapter as determined by the Township.