A. 
Applicants may select runoff control techniques, or a combination of techniques, which are most suitable to control stormwater runoff from the development site. All controls shall be subject to approval of the Township Engineer. The Township Engineer may request specific information on design and/or operating features of the proposed stormwater controls in order to determine their suitability and adequacy in terms of the standards of this chapter.
B. 
The applicant should consider the effect of the proposed stormwater management techniques on any special soil conditions or geological hazards which may exist on the development site. In the event such conditions are identified on the site, the Township Engineer, at his sole and absolute discretion, may require in-depth studies by a competent geotechnical engineer approved by the Township Engineer. Not all stormwater control methods may be allowable at a particular development site.
C. 
In developing a stormwater management plan for a particular site, stormwater controls shall be selected according to the following order of preference:
(1) 
Minimization of impervious surfaces during site design.
(2) 
Flow attenuation by use of open vegetated swales and natural depressions.
(3) 
Stormwater detention/retention structures.
D. 
Infiltration practices shall be used to the extent practicable to reduce volume increases and promote groundwater recharge. A combination of successive practices may be used to achieve the applicable minimum control requirements. The applicant shall provide justification for rejecting each of the preferred practices based on actual site conditions.
A. 
Infiltration systems shall be sized and designed based upon local soil and ground water conditions.
B. 
Infiltration systems greater than three feet deep shall be located at least 10 feet from basement walls.
C. 
Infiltration systems may not receive runoff until the entire drainage area to the system has received final stabilization.
D. 
The stormwater infiltration facility design shall provide an overflow system with measures to provide a nonerosive velocity of flow along its length and at the outfall.
E. 
All stormwater infiltration systems shall provide a volume of at least one cubic foot of every two square feet of impervious surface, and any stormwater infiltration system shall be located to capture runoff from all impervious surfaces.
[Amended 11-15-2022 by Ord. No. 2022-03]
F. 
Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase, so as to maintain their maximum infiltration capacity.
A. 
If flow attenuation facilities are employed to assist in the control of peak rates of discharge, their effects must be quantified using the NRCS Technical Release (TR) 55 Urban Hydrology for Small Watersheds or other approved method approved by the Township Engineer. The effects of the flow attenuation facilities on travel time should be reflected in the calculations.
B. 
Flow attenuation facilities such as swales and natural depressions should be properly graded to ensure positive drainage and avoid prolonged ponding of water.
C. 
Swales shall be properly vegetatively stabilized or otherwise lined to prevent erosion.
D. 
Swales shall be designed according to the recommendations contained in the Erosion and Sediment Pollution Control Program Manual (E&S Manual)2, No. 363-2134-008 (April 15, 2000), as amended and updated.
A. 
If detention/retention facilities are utilized for the development site, the facilities shall be designed such that postdevelopment peak runoff rates from the developed site are controlled to those rates defined by this chapter.
B. 
All detention facilities shall be equipped with outlet structures to provide discharge control for the designated storm frequencies. Provisions shall also be made to safely pass the postdevelopment one-hundred-year storm runoff with a minimum of one foot of freeboard without damaging or impairing the continued function of the facilities. Should any stormwater management facilities be regulated by Pennsylvania DEP Chapter 105 regulations, the facility shall be designed in accordance with those regulations and meet the Pennsylvania DEP regulations concerning dam safety which may require the passage of storms larger than the one-hundred-year event.
C. 
Shared-storage facilities which provide detention of runoff for more than one development site within a single subarea are encouraged wherever feasible and provided such facilities meet the criteria contained in this chapter. In addition, runoff from the development sites involved shall be conveyed to the facility in a manner that avoids adverse impacts (such as flooding or erosion) to channels and properties located between the development site and the shared-storage facilities.
D. 
Where detention facilities will be utilized, multiple use facilities, such as wetlands, lakes, ball fields or similar recreational/open space uses are encouraged wherever feasible, subject to the approval of the Township and compliance with the Pennsylvania DEP's Chapter 105 regulations.
E. 
Construction of the detention/retention facilities shall conform to the construction specifications of the PennDOT, Publication 408, latest edition, and RC Standards for Roadway Construction, latest edition.
F. 
Design of the detention/retention facilities shall be in accordance with the standard details included in Appendix B[1] and include the following:
(1) 
Inflow and outflow structures shall be designed and installed to prevent erosion to the side slopes and bottom of the structures shall be protected from soil erosion.
(2) 
Control and removal of debris both in the storage structure and in all inlet or outlet devices shall be a design consideration.
(3) 
Inflow and outflow structures, pumping stations, and other structures shall be designed and protected to minimize safety hazards.
(4) 
The water depth at the perimeter of a storage pond should be limited to that which is safe for children. Current ordinances call for restriction of access by way of fencing is required. Further restriction of access (walls, for example) may be necessary depending on the location of the facility and the maximum depths of water.
(5) 
Side slope of storage ponds shall not exceed a ratio of 2.5:1 horizontal to vertical dimension.
(6) 
Landscaping shall be provided for the facility which harmonizes with the surrounding area.
(7) 
Facilities shall be located to facilitate maintenance, considering the frequency and type of equipment that will be required. All detention ponds shall be provided with a suitable access road to be approved by the Township.
(8) 
Bottoms of detention basins should be graded with sufficient slope to provide positive surface drainage. A subdrainage system may be required depending on the location of the pond bottom relative to groundwater levels.
(9) 
The perimeter of all stormwater detention/retention basins shall be completely fenced with a fence having a minimum height of six feet. Said fence shall be constructed of chain link or similar material as may be approved by the Township. A double gate having a minimum width of 12 feet shall be installed to provide access to the stormwater detention/retention basin. The developer shall furnish a gate lock. To facilitate maintenance and inspection, all stormwater detention/retention basins shall be provided with a stabilized access roadway of a type subject to approval of the Township Engineer and having a minimum width of 12 feet. The access roadway shall be placed with an easement not less than 20 feet wide, as approved by the Township Engineer, who may require additional width of easement as circumstances warrant. The fence shall be constructed in accordance with PennDOT, Publication 408 Sections 624 and 1110, latest edition, and the standard detail contained in Appendix B.[2]
(a) 
Fencing may be waived if the proposed facility meets the following three criteria:
[1] 
Maximum possible ponding depth of 12 inches or less;
[2] 
Maximum side slopes of the facility are 3:1;
[3] 
Calculations are provided to demonstrate the facility will dewater within 72 hours of a storm event.
[2]
Editor's Note: Said appendix is on file and available for review in Township offices.
[1]
Editor's Note: Said appendix is on file and available for review in Township offices.
A. 
All stormwater runoff collection or conveyance facilities, whether storm sewers or other open or closed channels, shall be designed in accordance with the following criteria:
(1) 
Lots shall be laid out and graded to provide positive drainage away from and around structures. The Township may require a grading and drainage plan for individual lots indicating the buildable area within each lot, complying with the setback requirements, for which positive drainage is assured.
(2) 
Springs, surface sump pump discharges and French drains shall extend to a stormwater collection/conveyance/control system or natural watercourse in accordance with the approved stormwater management plan for the development site. The outlets for these facilities shall be equipped with energy dissipation devices to prevent erosion.
(3) 
Collection/conveyance facilities should not be installed parallel and close to the top or bottom of a major embankment to avoid the possibility of failing or causing the embankment to fail.
(4) 
All collection/conveyance facilities shall be designed to convey the twenty-five-year storm peak flow rate from the contributing drainage area and to carry it to the nearest suitable outlet such as a stormwater control facility, curbed street, storm sewer or natural watercourse without damage to the drainage structure or roadway, with runoff from the twenty-five-year design storm at a minimum 1.0 foot of freeboard measured below the lowest point along the top of the roadway. Roadway crossings located within designated floodplain areas must be able to convey runoff from a one-hundred-year design storm with a minimum of 1.0 foot freeboard measured below the lowest point along the top of the roadway. When it can be shown that, due to topographic conditions, natural drainageways on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainageways. Work within natural drainageways shall be subject to approval by Pennsylvania DEP through the joint permit application process, or, where appropriate by Pennsylvania DEP, through the general permit process.
(5) 
Where drainage swales or open channels are used, they shall be suitably lined to prevent erosion and designed to avoid excessive velocities. Rock lining shall conform to Section 850, Rock lining, of PennDOT Publication 408. The minimum size of rock lining shall be R4.
(6) 
Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with this chapter.
(7) 
Existing points of concentrated drainage that discharge onto adjacent property shall not be altered without permission of the altered property owner(s) and shall be subject to any applicable discharge criteria specified in this chapter.
(8) 
In those instances where proposed stormwater facilities alter existing drainage flow patterns, or concentrate discharge flows, flow across lands of adjoining property owners before entering waters of the commonwealth, the developer must secure stormwater releases from said adjoining property owners evidencing their approval of the proposed alteration. Securance of such releases shall be a precondition of Township subdivision and land development preliminary plan approval.
(9) 
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 flow is proposed to be concentrated and discharged onto adjacent property, the developer must document that adequate downstream conveyance facilities exist to safely transport the concentrated discharge or otherwise prove that no erosion, sedimentation, flooding, or other harm will result from the concentrated discharge.
(10) 
Where watercourses traverse a development site, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easements shall prohibit excavation, the placing of fill or structures, and any alterations that may adversely affect the flow of stormwater within any portion of the easement. Also, maintenance, including mowing of vegetation within the easement shall be required except as approved by the appropriate governing authority.
(11) 
Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the Commonwealth of Pennsylvania or wetlands shall be subject to approval by Pennsylvania DEP through the joint permit application process or, where deemed appropriate by Pennsylvania DEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the developer 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 by Pennsylvania DEP.
(12) 
Any stormwater management facilities regulated by this chapter that would be located on federal, commonwealth or county highway rights-of-way shall be subject to approval by the appropriate governmental agency having jurisdiction.
(13) 
Stormwater drainage, including roof drains, shall not be connected to the sanitary sewer system.
B. 
Wherever storm sewers are proposed to be utilized, they shall comply with the following criteria:
(1) 
Where practical, storm sewer shall be designed to traverse under seeded and planted areas. If constructed within 10 feet of road paving, walks or other surfaced areas, drains shall have a narrow trench and maximum compaction of backfill to prevent settlement of the superimposed surface or development. When located in undedicated land, storm sewers shall be placed within an easement not less than 20 feet wide, as approved by the Township Engineer, who may require additional width of easement as circumstances warrant.
(2) 
Storm sewers shall be installed after excavating and filling in the area to be traversed is completed, unless the drain is installed in the original ground with a minimum of three feet cover and/or adequate protection during the fill construction.
(3) 
Storm sewers shall be designed with cradle when traversing fill areas of indeterminate stability and with anchors when gradient exceeds 20%.
(4) 
Storm sewers shall be backfilled with PennDOT No. 2A coarse aggregate when traversing under a paved area and shoulder areas.
(5) 
Storm sewers shall be designed to adequately handle the anticipated stormwater flow and be economical to maintain. The minimum pipe size shall be 15 inches in diameter.
(6) 
Storm sewer pipe, trenching, bedding and backfilling requirements shall conform to the requirements of PennDOT Publication Form 408 specifications.
(7) 
Storm sewers shall be constructed of one of the materials specified in PennDOT Publication Form 408 specifications, Sections 601, 602 and 603. All corrugated polyethylene pipe shall be Type S pipe within a Township right-of-way shall be reinforced concrete pipe.
(8) 
Storm inlets and structures shall be designed to be adequate, safe, self-cleaning and unobtrusive and consistent with Township standards. The maximum spacing of inlets shall be 600 feet. Inlets shall be PennDOT Type C or M with cast-in-place reinforced concrete or precast concrete tops.
(9) 
The appropriate grates shall be provided for all stormwater inlets and other entrance appurtenances.
(10) 
Manholes shall be designed so that the top shall be at finished grade and sloped to conform to the slope of the finished grade. Top castings of structures located in roads or parking areas shall be machined or installed to preclude clanking.
(11) 
Where a proposed storm sewer connects with an existing storm sewer system, the developer shall demonstrate that sufficient capacity exists in the downstream system to handle the additional flow. The developer shall furnish a letter from the owner of the existing storm sewer system approving the connection of the proposed storm sewer system.
(12) 
Storm sewer outfalls and culverts, including driveway cross pipes, shall be equipped with either reinforced concrete headwalls or pipe end sections and energy dissipation devices to prevent erosion and conform with applicable requirements of the Pennsylvania DEP for stream encroachments (Chapter 105 of Pennsylvania DEP rules and regulations).