A. 
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 109-15:
(1) 
Preparation and implementation of an approved SWM site plan is required.
(2) 
No regulated activities shall commence until the municipality issues written approval of an SWM site plan which demonstrates compliance with the requirements of this chapter.
B. 
All SWM site plans for regulated activities shall include such measures as necessary to:
(1) 
Protect health, safety, and property.
(2) 
Meet the water quality goals of this chapter, as stated in § 109-3, by including measures that:
(a) 
Minimize disturbance to floodplains, wetlands, wooded areas, and existing vegetation.
(b) 
Maintain or extend riparian buffers.
(c) 
Avoid erosive flow conditions in natural flow pathways.
(d) 
Minimize thermal impacts to waters of the commonwealth.
(e) 
Disconnect impervious surfaces by directing runoff to pervious areas.
(f) 
Minimize soil disturbance and compaction.
(3) 
Incorporate the techniques for low-impact development practices described in the Pennsylvania Stormwater Best Management Practices Manual (BMP Manual).
C. 
Stormwater flows onto adjacent property shall not be created, increased, or relocated, without the written notification of the adjacent property owner(s) by the developer. Copies of all such notifications shall be included in the SWM site plan submission.
D. 
For all regulated activities where erosion and sediment control is required in accordance with Title 25 of the Pennsylvania Code and the Clean Streams Law,[1] the SWM site plan shall include the required erosion and sedimentation control measures. Necessary E&S BMPs shall be designed in accordance with the Erosion and Sediment Pollution Control Program Manual (E&S Manual) 2, No. 363-2134-008 (April 15, 2000), as amended and updated. Approval of the SWM site plan by the Township shall be conditioned on the applicant obtaining erosion and sedimentation control approval from the appropriate agency(ies), when applicable.
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
E. 
For all regulated activities where NPDES permitting is required in accordance with the Clean Water Act [33 U.S.C. § 1251 et seq. (1972), as amended], the SWM site plan shall include the information required in the applicant's NPDES permit application. Approval of the SWM site plan by the Township shall be conditioned on the applicant obtaining NPDES permit approval from the appropriate agency(ies), when applicable.
F. 
For all regulated activities, implementation of the volume controls in § 109-17 is required unless the project is determined to be exempt pursuant to § 109-15.
G. 
Special management areas. SWM site plans involving regulated activities within special management areas shall be prepared in a manner consistent with the guidance provided in Chapter 7 of the BMP Manual. The SWM site plan submission shall include design details for SWM BMPs within said special management area, and shall include information on why the area is deemed to be a "special management area."
H. 
A SWM site plan may propose that stormwater related to the proposed regulated activities be accommodated by existing stormwater management facilities on adjoining or nearby properties, provided that the SWM site plan documents the following.
(1) 
The use of the stormwater management facilities located on said adjoining or nearby property is approved in writing by the owner of the property.
(2) 
The stormwater management facilities located on said adjoining or nearby property are designed in a manner that can accommodate the stormwater management needs of the regulated activity in a manner consistent with all requirements of this chapter. The SWM site plan shall include all documentation necessary for the Township to confirm such compliance.
I. 
The design storm volumes to be used in the analysis of peak rates of discharge shall be obtained from the Precipitation-Frequency Atlas of the United States, Atlas 14, Volume 2, Version 3.0, as amended and updated, United States Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Hydrometeorological Design Studies Center, Silver Spring, Maryland. NOAA's Atlas 14 can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
J. 
SWM site plans, once approved by the Township, shall remain on site throughout the duration of the regulated activity and be available for review as may be necessary by representatives of the Township.
K. 
The design of all facilities over karst shall include an evaluation of measures to minimize adverse effects.
L. 
The Township may, after consultation with DEP, approve measures for meeting the state water quality requirements other than those in this chapter, provided that they meet the minimum requirements of, and do not conflict with, state law including, but not limited to, the Clean Streams Law. The municipality shall maintain a record of consultations with DEP pursuant to this subsection.
A. 
A property owner or developer of any regulated activity that meets the following exemption criteria is, upon approval from the Township, exempt from the formal SWM site plan submission requirements of this chapter as specified herein. However, the property owner or developer shall be subject to all other requirements of this chapter other than the formal SWM site plan submission requirements for which an exemption or exemptions have been authorized, unless otherwise indicated. The criteria for exemption in this section apply to the total development proposed, including instances in which the development is proposed to take place in phases. The date of enactment of this chapter shall be the starting point from which future development and the respective exemption criteria shall be cumulatively considered and regulated.
(1) 
Regulated activities that involve equal to or less than 1,000 square feet of impervious surface may be exempted from the peak rate control, volume control and the SWM site plan preparation and submission requirements of this chapter. The applicant shall complete the Municipal Stormwater Management Worksheet from the Stormwater Management Design Assistance Manual and file said worksheet with the Township.
(2) 
Regulated activities that involve greater than 1,000 square feet and equal to or less than 10,000 square feet of impervious area, and where all the proposed impervious area can be entirely disconnected, may be exempted from the peak rate control, volume control, and the SWM site plan preparation and submission requirements of this chapter. The applicant shall complete the Stormwater Management Worksheets from the Stormwater Management Design Assistance Manual and file said worksheets with the Township.
(3) 
Regulated activities that involve greater than 1,000 square feet and equal to or less than 5,000 square feet of impervious area may be exempted from the peak rate control and volume control preparation and submission requirements of this chapter. A minor stormwater site plan, as detailed in the Stormwater Management Design Assistance Manual, shall be submitted to the Township instead of the submission of a full SWM site plan in accordance with Article IV of this chapter.
(4) 
Agricultural activities shall be exempt from the rate control, volume control and SWM site plan preparation and submission requirements of this chapter, provided the agricultural activities are performed in accordance with the requirements of 25 Pa. Code 102. Further, such activities shall not be subject to the exemption approval process of § 109-15B of this chapter.
(5) 
Forest management and timber operations are exempted from the rate control, volume control and SWM site plan preparation and submission requirements of this chapter, provided the forest management and timber operations are performed in accordance with the requirements of 25 Pa. Code 102, as amended or repromulgated from time to time.
(6) 
Regulated activities involving domestic gardening for single-family consumption shall be exempted from volume control, rate control, and SWM site plan preparation and submission requirements of this chapter, and shall not be subject to the exemption approval process of § 109-15B of this chapter.
(7) 
In-kind repair, in-kind replacement, and maintenance of existing surfaces, and structures shall be exempted from volume control, rate control, and SWM site plan preparation and submission requirements of this chapter, and shall not be subject to the exemption approval process of § 109-15B of this chapter.
B. 
Authorization of exemptions. The Township shall determine, in accordance with the following requirements and process, whether a proposed regulated activity may be exempted from any of the requirements of this chapter.
(1) 
The property owner or developer proposing the regulated activity shall submit, in writing on a form supplied by the Township, a request for said proposed regulated activity to be exempted from allowable requirements of this chapter pursuant to Subsection A. The written request shall identify the project and shall indicate the specific exemption criteria, as listed in § 109-15A, that apply to the project and shall be submitted in accordance with the Stormwater Management Worksheets from the Stormwater Management Design Assistance Manual.
(2) 
Upon receipt of the exemption request form, the Township or its designee shall either approve or deny the exemption request. If the exemption request is denied, the Township or its designee shall direct the property owner or developer to submit the information required to demonstrate that the proposed regulated activity complies with the requirements of this chapter or meets the exemption criteria.
(3) 
Exemption request approval shall be at the discretion of the Township, and shall be subject to the following:
(a) 
The Township may deny any exemption request or suspend or revoke any approved exemption request at any time for any project where the Township believes that the proposed regulated activity poses a threat to public health, safety, property, or the environment.
(b) 
Approval of an exemption request does not relieve the property owner or developer from other applicable requirements of this chapter or of other Township ordinance or regulations.
(c) 
The Township reserves the right to deny an exemption request if a drainage problem is known or identified as existing or is expected to exist downstream from the proposed regulated activity.
A. 
Impervious area.
(1) 
The measurement of impervious areas shall include all of the impervious areas in the total proposed development, even if development is to take place in phases.
(2) 
For development taking place in phases, the total proposed impervious area within the SWM site plan must be used in determining conformance with this chapter.
(3) 
For projects that add impervious area to a parcel, the total impervious area on the parcel is subject to the requirements of this chapter; except that the volume controls in § 109-17 and the peak rate controls of § 109-18 do not need to be retrofitted to existing impervious areas that are not being altered by the proposed regulated activity.
B. 
Normally, dry, open-top storage facilities, designed as such, shall completely drain both the volume control and rate control capacities over a period of time not less than 24 hours and not more than 72 hours from the end of the design storm. However, any designed infiltration volume at such facilities is exempt from the minimum twenty-four-hour standard, i.e., may infiltrate in a shorter period of time, so long as none of the stormwater intended for infiltration is discharged into the surface waters of the commonwealth.
C. 
Infiltration BMPs shall be spread out, made as shallow as practicable, and located to maximize use of natural on-site infiltration features while still meeting the other requirements of this chapter.
D. 
A stormwater management plan shall be submitted for all subdivisions and/or land developments. The plan shall show all drainage within the area affecting the subject property, all existing and proposed drainage facilities and all grading proposed for the subject property, as well as the additional plan information required in this section.
E. 
All land areas shall be graded to secure proper drainage away from buildings, on-lot sewage disposal facilities and the like and to prevent the collection of stormwater in pools. Drainage provisions shall be of such design as to carry surface waters to the nearest practical natural drainage channel, storm sewer system detention basin or other drainage facilities. The landowner or developer shall construct and/or install such drainage structures and/or pipes as are determined necessary by the Township to prevent soil erosion, damage and siltation and to satisfactorily carry off surface water. In the design of storm drainage facilities, special consideration must be given to preventing excess runoff onto adjacent developed or undeveloped properties. In no case may any slope exceed the normal angle of slippage of the material involved. All slopes must be protected against erosion. In no case may a change be made in the existing topography which would alter the existing drainage or topography in a way so as to adversely affect adjoining properties.
F. 
Storm sewers, culverts, bridges and related drainage installations shall be provided to:
(1) 
Permit unimpeded flow of natural watercourses. Such flow may be redirected as required, subject to the approval of the Pennsylvania Department of Environmental Protection.
(2) 
Ensure adequate drainage of all low points as may be related to streets.
(3) 
Intercept stormwater runoff along streets at intervals reasonably related to the extent and grade of the area drained to prevent flow of stormwater across intersections and to prevent the flooding of intersections during the design storm.
(4) 
Ensure adequate and unimpeded flow of stormwater under driveways in, near or across natural watercourses or drainage swales. Properly sized pipes or other conduits shall be provided as necessary.
(5) 
Prevent excessive flow on or across streets, sidewalks, drives, parking areas and any other paved surface or access way.
(6) 
Lead stormwater away from springs.
(7) 
Provide adequate drainage away from on-site sewage disposal systems.
G. 
The stormwater management plan for each subdivision and/or land development shall take into account and provide for upstream areas within the entire watershed in computing discharge quantities, sizing of pipes, inlets and other structures. The runoff from any proposed development shall be subject to evaluation which includes the anticipated runoff from other existing or proposed developments within the same watershed. Stormwater management facilities designed to serve more than one property or development in the same watershed are encouraged, in which case consultation with the Township is required prior to design.
H. 
All natural streams, channels, swales, drainage systems and/or areas of concentration of surface water shall be maintained in their existing condition unless alteration is approved by the Township. In any event, all encroachment activities shall comply with Chapter 105 of the Commonwealth of Pennsylvania Department of Environmental Protection, Dam Safety and Waterway Management Rules and Regulations.
I. 
Man-made structures shall be kept to a minimum and bridges, culverts, or riprap shall be constructed to maintain the natural characteristics of the stream and shall meet the approval of the Township.
J. 
Retention/detention basins shall be designed to utilize the natural contours of the land. When such design is impracticable, the construction of the basin shall utilize slopes as shallow as possible to blend the structures into the existing terrain.
K. 
Any subdivision and/or land development within a flood hazard district shall comply with all of the provisions of the Straban Township Zoning Ordinance, and the rules and regulations of the Pennsylvania Department of Environmental Protection.
L. 
The Township may require that a landowner or developer provide reasonable corrective measures to alleviate an existing off-site drainage problem which may be affected by the proposed subdivision and/or land development. It shall be the responsibility of the landowner or developer to obtain all drainage easements in, over or through other properties, and the Township, its agents, workmen, servants and employees shall be indemnified and held harmless from any liability.
M. 
All lots, tracts or parcels shall be graded to provide proper drainage away from buildings and dispose of the runoff without ponding, and all land within a development shall be graded to drain and dispose of surface water without ponding, except where other arrangements are approved by the Township. Grading shall not be done in such a way so as to divert water onto the property of another landowner without the expressed consent of the Township and the affected landowner.
The low-impact development practices provided in the BMP Manual shall be utilized for all regulated activities. Water volume controls shall be implemented using the Design Storm Method in § 109-17A or the Simplified Method in § 109-17B. For a regulated activity involving less than one acre of impervious coverage that does not require hydrologic routing to design the stormwater facilities, the applicant may select either methodology on the basis of economic considerations, the intrinsic limitations on applicability of the analytical procedures associated with each methodology, and/or other factors. The Design Storm Method in § 109-17A shall be used for all regulated activity involving greater than one acre of impervious coverage.
A. 
The Design Storm Method (CG-1 in the BMP Manual) may be used for any size of regulated activity. This method requires detailed modeling to achieve the following standards.
(1) 
The post-development total runoff volume shall not increase for all storms equal to or less than the two-year twenty-four-hour duration precipitation.
(2) 
For modeling purposes:
(a) 
Existing (predevelopment), non-forested, pervious areas must be considered meadow.
(b) 
Twenty percent of existing impervious area, when present, shall be considered meadow in the model for existing conditions.
B. 
The Simplified Method (CG-2 in the BMP Manual) is independent of site conditions and may be used for projects involving regulated activities proposing equal to or less than one acre of impervious coverage and that do not require design of stormwater storage facilities. When the Simplified Method is used to address stormwater management needs of new impervious surfaces, the following design standards shall be achieved:
(1) 
Stormwater facilities shall capture at least the first two inches of runoff from all new impervious surfaces.
(2) 
At least the first one inch of runoff from new impervious surfaces shall be permanently removed from the runoff flow and shall not be released into the surface waters of the commonwealth. Removal options for the first one inch of runoff include, but are not necessarily limited to, reuse and infiltration.
(3) 
Infiltration facilities shall be designed to accommodate infiltration of as much of the permanently removed runoff as site conditions will allow. If the soils within the project area do not allow for infiltration of the entire first one inch of runoff from new impervious surfaces, other forms of runoff volume control shall be used to achieve the required removal volume. Such measures may include, but are not limited to vegetated roofs, biorention, and capture-and-reuse systems. In addition, the infiltration alternative authorized in § 109-17C may be employed.
(4) 
This method is exempt from the requirements of § 109-18, Rate controls.
C. 
Infiltration alternative. Where infiltration is not possible due to soil characteristics or is not desirable given other characteristics, water quality control may be proposed as an alternative to strict adherence to the volume control standards of § 109-17 of this chapter. Where water quality control is proposed, the following standards shall be achieved.
(1) 
At a minimum, the following documentation shall be provided to justify the proposal to reduce the infiltration requirements:
(a) 
Description of and justification for field infiltration/permeability testing with respect to the type of test and test locations.
(b) 
An interpretive narrative describing existing soils of the site and their structure as these relate to the interaction between soils and water characteristics of the site. In addition to providing soil and soil profile descriptions, this narrative shall identify depth to seasonal water tables and depth to bedrock and provide a description of all subsurface elements (restrictive layers, geology, etc.) that influence the direction and rate of subsurface water movement.
(c) 
A qualitative assessment of the site's contribution to annual aquifer recharge shall be made, along with the identification of any restrictions or limitations associated with the use of designed infiltration facilities.
(d) 
The provided documentation must be signed and sealed by a professional engineer or geologist.
(2) 
Water quality BMPs shall be implemented on all permanent stormwater discharges from the proposed project site to achieve pollutant removal efficiencies in accordance with the Table 109-17.
Table 109-17 Required Pollutant Removal Efficiencies for Infiltration Alternatives
Pollutant Load
Units
Required Removal Efficiency
(%)
Total suspended solids (TSS)
Pounds
85%
Total phosphorus (TP)
Pounds
85%
Total nitrate (NO3)
Pounds
50%
(3) 
Design guidance from the most current version of the Pennsylvania Stormwater Best Management Practices Manual, or equivalent resource as precoordinated with the Township, shall be consulted when choosing design criteria for water quality BMPs.
A. 
Post-development discharge rates shall not exceed the predevelopment discharge rates for the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year, twenty-four-hour storms. If it is shown that the peak rates of discharge indicated by the post-development analysis are less than or equal to the peak rates of discharge indicated by the predevelopment analysis for one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year, twenty-four-hour storms, then the requirements of this section have been met. Otherwise, the applicant shall provide additional controls as necessary to satisfy the peak rate of discharge requirement.
B. 
For computation of predevelopment peak discharge rates, 20% of existing impervious areas, when present, shall be considered meadow.
Where an applicant proposes to utilize riparian buffers as the means to meet the requirements of this chapter, said riparian buffers shall be established and/or maintained in accordance with the BMP Manual or the publication Riparian Forest Buffer Guidance, published November 2010 by the Pennsylvania Department of Environmental Protection, and as may be amended or updated.
A. 
Any drain or conveyance, whether on the surface or subsurface, that allows any nonstormwater discharge including sewage, process wastewater, and wash water to enter the waters of the commonwealth is prohibited.
B. 
No person shall allow, or cause to allow, discharges into surface waters of the commonwealth which are not composed entirely of stormwater, except:
(1) 
As provided in Subsection C below; and
(2) 
Discharges allowed under a state or federal permit.
C. 
The following discharges are authorized unless they are determined to be significant contributors to pollution to the waters of the commonwealth:
(1) 
Discharges from fire-fighting activities.
(2) 
Potable water sources including waterline flushing.
(3) 
Irrigation drainage.
(4) 
Air-conditioning condensate.
(5) 
Springs.
(6) 
Water from crawl space pumps.
(7) 
Pavement wash waters where spills or leaks of toxic or hazardous materials have not occurred (unless all spill material has been removed) and where detergents are not used.
(8) 
Diverted stream flows.
(9) 
Flows from riparian habitats and wetlands.
(10) 
Uncontaminated water from foundations or from footing drains.
(11) 
Lawn watering.
(12) 
Dechlorinated swimming pool discharges.
(13) 
Uncontaminated groundwater.
(14) 
Water from individual residential car washing.
(15) 
Routine external building wash-down (which does not use detergents or other compounds).
(16) 
Water discharged in well testing for potable water supplies.
D. 
In the event that the municipality or DEP determines that any of the discharges identified in Subsection C significantly contribute to pollution of the waters of the commonwealth, the municipality or DEP will notify the responsible person(s) to cease the discharge.
Roof drains, sump pumps, and footer drains should discharge to infiltration or vegetative BMPs and, to the maximum extent practicable, satisfy the criteria for DIAs. Discharges of each should be conveyed in such a manner as to not cause water problems for adjoining property owners. Roof drains, sump pumps, and footer drains shall not discharge to roadways, curblines, or storm sewer systems without approval by the Township.
No person shall modify, remove, fill, landscape, or alter any SWM BMPs, facilities, areas, or structures in a manner, without the written approval of the Township, with the exception of necessary maintenance activities such as mowing.
A. 
Standards and criteria.
(1) 
Storm drainage system.
(a) 
Design flow rate.
[1] 
The storm sewer system shall be designed to carry a twenty-five-year peak flow rate without surcharging inlets. The peak flow rate into each inlet shall be indicated on the stormwater drainage plan. The design 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 peak runoff rate to the average rate of rainfall over a time period equal to the time of concentration.
I
=
Average rainfall intensity in inches per hour for a time equal to the time of concentration.
A
=
Drainage area in acres.
[2] 
Appropriate values for the runoff coefficient and rainfall intensity shall be taken from the following source, unless otherwise approved by the Township:
Commonwealth of Pennsylvania
Department of Transportation
Publication 584, PennDOT Drainage Manual
2010 Edition (or the latest revision thereto)
(b) 
Storm sewer system design.
[1] 
The storm sewer system shall be designed to the more restrictive of the following: to collect stormwater at any point where three to five cubic feet per second is accumulated during the design storm; and/or inlets/manholes shall not be spaced more than 300 feet apart on pipe sizes up to 24 inches in diameter and not more than 400 feet apart on greater sizes.
[2] 
Inlets, manholes, grates, covers, frames and the like shall conform to the Pennsylvania Department of Transportation Roadway Construction Standards and Form No. 408 specifications and all amendments, revisions or updates thereto.
[a] 
All inlets and manholes shall be precast concrete, unless approved otherwise by the Township.
[b] 
Sump areas below inlet piping shall not be permitted unless approved otherwise by the Township.
(c) 
Bridge/culvert/channel design.
[1] 
Bridges and culverts shall have ample waterway to carry expected flows, based on a minimum storm frequency of 100 years or as required by the Pennsylvania Department of Environmental Protection. Bridge and/or culvert design shall be in accordance with the Pennsylvania Department of Transportation and/or the Pennsylvania Department of Environmental Protection requirements. All culverts shall be provided with concrete end walls.
[2] 
All drainage channels shall be designed to carry a flow rate equal to a one-hundred-year, twenty-four-hour storm.
[3] 
All drainage channels shall be designed to prevent the erosion of the stream bed and stream bank areas. The flow velocity in all vegetated drainage channels shall not exceed the maximum permissible velocity to prevent soil erosion. Suitable bank stabilization shall be provided where required to prevent soil erosion of the drainage channels. 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 riprap and masonry and/or concrete walls. The stabilization shall be designed to prevent soil erosion and front heave under and behind the stabilizing media.
[4] 
Any vegetated drainage channel requiring mowing of the vegetation shall have a maximum slope of four horizontal to one vertical on those areas to be mowed.
[5] 
In all instances where a proposed driveway culvert will cross a drainage channel/swale, a minimum fifteen-inch diameter driveway culvert must be provided that will be adequate to convey the design flows of the drainage channel.
[6] 
The design of all channels shall, as a minimum, conform to the design procedures outlined with the Pennsylvania Department of Transportation standards, Pennsylvania Stormwater Best Management Practices Manual, and Pennsylvania Department of Environmental Protection Erosion and Sediment Pollution Control Program Manual.
(d) 
Overflow system. An overflow system shall be provided to carry flow to the detention basin when the capacity of the storm drain pipe system is exceeded. The overflow system shall have sufficient capacity to carry the difference between the one-hundred-year and the twenty-five-year peak flow rates.
(e) 
Inlet capacity.
[1] 
All inlets must be designed to accommodate the twenty-five-year peak flow rate. The capacity of Type C, M, or S inlets shall be determined from the following source:
Commonwealth of Pennsylvania
Department of Transportation
Publication 584, PennDOT Drainage Manual
2010 Edition (or the latest revision thereto)
[2] 
The capacity of each inlet shall be indicated within the SWM site plan narrative. All stormwater management plans shall indicate that inlet grates be installed in such a manner that the roadway stormwater will be directed into the inlet and away from the roadway. All inlets shall be designed to create a one-inch sump condition below finished road surface unless approved otherwise by the Township. At curbed street/driveway intersections, inlets shall be placed on the tangent section and not in the curved portion of the curbing.
(f) 
Straight pipe sections. All storm sewers shall be designed to follow straight courses. No angular deflections of storm sewer pipe sections in excess of 5° shall be permitted. No vertical curves shall be permitted in the storm sewer system.
(g) 
Horizontal pipe deflections. A manhole or inlet shall be provided at all horizontal deflections in the storm pipe system exceeding 5°.
(h) 
Minimum grade and size. All storm drain pipes shall be designed to maintain a minimum grade that will result in a full flow velocity of at least two feet per second. All storm sewer pipes shall have a minimum inside diameter of 15 inches.
(i) 
Pipe capacity. The capacity of all pipe culverts shall, as a minimum, provide the required carrying capacity to meet current Pennsylvania Department of Transportation standards and criteria.
(j) 
Pipe arches. Where headroom is restricted, equivalent pipe arches may be used in lieu of circular pipes.
(k) 
Pipe material and gauge thickness. All storm sewers shall be either reinforced cement concrete, corrugated aluminum, corrugated polyethylene pipe, smooth lined corrugated polyethylene pipe, or aluminized Type II steel pipe. Storm sewers shall be of the proper class and thickness to support the above fill material. Pipe class and gauge or thickness shall be noted on the plans. All pipe shall conform to Pennsylvania Department of Transportation specifications.
(l) 
Allowable headwater depth. At all inlets or manholes, the maximum allowable headwater depth shall be one foot below the top of the inlet grate or the manhole.
(m) 
Minimum and maximum cover. In lawn areas, a minimum of 12 inches of cover shall be maintained over all storm drain pipes or as specified by the pipe manufacturer. Under streets, the top of storm drain pipes shall be a minimum of six inches below sub grade elevation or as specified by the pipe manufacturer. The maximum cover over storm drain pipes shall be 10 feet unless otherwise approved by the Township.
(n) 
Storm sewer system outlets. Storm sewer system outlet pipes shall extend to proposed stormwater management facilities, natural watercourses and the like. A concrete end wall shall be required on all storm sewer system inlet and outlet pipes. All storm/sewer outlets 24 inches in diameter or greater shall be equipped with a galvanized child-proof horizontal bar rack, bolted to the end wall.
(o) 
Drainage easements.
[1] 
All storm sewer easements through undedicated land shall be a minimum of 20 feet in width.
[2] 
Where a site is traversed by a watercourse, a drainage easement or right-of-way conforming substantially with the line of such watercourse and of such width as will be adequate to preserve natural drainage and provide sufficient width for maintenance shall be created, as determined by the Township.
(p) 
Diversion of surface water runoff. All storm sewers and/or drainage swales shall be designed to carry such runoff into a detention basin or similar facility utilized to control the rate of runoff, unless approved otherwise by the Township.
(2) 
Detention/retention basins.
(a) 
Detention basins shall be designed in accordance with the Soil Cover Complex Method and the procedures developed by the United States Department of Agriculture, Soil Conservation Service, as outlined in their Technical Release No. 55, Urban Hydrology for Small Watersheds, with specific attention given to antecedent moisture conditions, flood routing and peak discharge and Hydrology National Engineering Handbook Section 4, or other method as approved by the Township Engineer.
(b) 
Basin design criteria (SCS). Basins shall be designed to safely convey the quantity of water resulting from a one-hundred-year, twenty-four-hour storm under full development conditions. Stormwater management calculations shall ensure that the predevelopment discharge from the site conforms with § 109-18.
(c) 
Outlet control structures.
[1] 
All outlet control structures shall be constructed of concrete, properly anchored to prevent flotation and equipped with childproof, nonclogging removable trash racks over all design openings 12 inches or greater in diameter, except those openings designed to carry perennial stream flows.
[2] 
Temporary sedimentation controls shall be provided during construction to prevent the flow of sediment through the basin outlet pipe. Such measures may include temporary riser pipes, rock-filled gabions, plywood standboxes, silt fences and the like.
(d) 
Emergency spillways. Whenever possible, the emergency spillway for basins shall be constructed on undisturbed ground. Emergency spillways shall be constructed of reinforced concrete, concrete moundslabs or vegetated earth. All emergency spillways shall be constructed so that the basin berm is protected against soil erosion. The minimum capacity of the emergency spillway shall be designed to pass the one-hundred-year post-development flow neglecting the capacity of the principal outlet structure. Emergency spillways shall extend along the upstream and downstream berm embankment slopes. The emergency spillway shall not discharge stormwater over earthen fill and/or easily erodible material without adequate protection against soil erosion.
(e) 
Freeboard. The minimum freeboard shall be one foot. (Freeboard is the difference between the design flow elevations in the emergency spillway and the top of the settled basin embankment.)
(f) 
Basin outlet pipes. Basin outlet pipes shall be equipped with watertight joints.
(g) 
Antiseep collars. Antiseep collars shall be installed around the principal pipe barrel within the normal saturation zone of the basin berms. The antiseep collars and their connections to the pipe barrel shall be watertight. The antiseep collars shall be designed in accordance with USDA SCS criteria. Design calculations for antiseep collars must be submitted with the basin calculations.
(h) 
Basin outlets. Energy-dissipating devices (concrete aprons and the like) shall be placed at all basin outlets. Concrete end walls shall be placed at all basin outlets. All basin outlet pipes 24 inches in diameter or greater shall be equipped with childproof devices to deter entry by pedestrians or animals. Design calculations for proposed energy dissipaters must be submitted with basin calculations.
(i) 
Slope of detention basin embankment.
[1] 
The maximum slope of earthen basin embankments shall be four to one (4:1), unless otherwise approved by the Township. The top or toe of any slope shall be located a minimum of 15 feet from adjacent property lines with the exception of the downstream property line where the toe of the embankment shall be placed a sufficient distance to allow for energy dissipating devices but in no case less than 40 feet unless approved otherwise by the Township.
[2] 
Whenever possible, the side slopes and basin shape shall blend with the natural topography. Straight side slopes and rectangular basins shall be avoided whenever possible.
(j) 
Width of berm. The minimum top width of detention basin berms shall be six feet.
(k) 
Construction specifications. The plans shall indicate the construction specifications and compaction requirements for all detention/retention basins.
(l) 
Cutoff trench. A cutoff trench shall be excavated along the center line of dam on earth fill embankments. The minimum depth shall be three feet. The minimum bottom width shall be 10 feet or wide enough to permit operation of compaction equipment. The side slopes shall be no steeper than 1:1. The trench shall be kept free from standing water during the backfilling operations.
(m) 
Grading and landscaping of basins; cuts and fills. No excavation or fill shall be made with a cut-and-fill slope steeper than four feet horizontal to one foot vertical unless otherwise approved by the Township Engineer. A written statement shall be required from a civil engineer licensed by the Commonwealth of Pennsylvania having experience in soils engineering certifying that he has inspected the site and that any proposed deviation from the slope specified above should not endanger any property or result in personal injury. Retaining walls will be required if a stable slope cannot be maintained. Any retaining wall design must be designed by an experienced structural engineer licensed by the Commonwealth of Pennsylvania. The toe of any cut or fill slope must be located a minimum of 15 feet from adjacent property lines.
(n) 
Landscaping.
[1] 
A minimum of four inches of topsoil shall be placed on all areas affected by the basin construction (bottom of basin, side slopes, top of berm and the like).
[2] 
All earthen basins shall be seeded with a standard seed mix containing temporary and permanent grasses capable of providing a minimum uniform seventy-percent perennial ground cover, or other approved ground covers, within seven days after final grading. Application rate shall be in accordance with the seed supplier's guidelines and recommendations.
[3] 
Fencing may be required around detention/retention basins where the Township determines that circumstances warrant the fencing.
[4] 
All detention/retention basins shall be landscaped.
(o) 
Permanent pond.
[1] 
A five-foot-wide bench sloping at 4% shall be provided for all detention/retention basins designed to contain a permanent pond of water. The toe of the bench shall begin at the permanent water surface elevation. Alternate designs may be submitted for review to the Township and its engineer.
[2] 
When a permanent pond is proposed, a report prepared by a certified geotechnical specialist must be provided certifying that the water will not become stagnant. The basin side slopes below the waterline must not exceed 4:1.
(p) 
Positive drainage. Detention basins must be designed to eliminate standing water or swampy conditions after the basin has drained. This must be accomplished either by the installation of stone-trenched underdrains or by providing a minimum basin bottom slope of 2% to the basin outlet. Other arrangements may be presented for review and approval by the Township, provided the facility is entirely dewatered in accordance with § 109-16B.
(3) 
Subsurface infiltration/disposal/retention basin systems. The following procedures and materials shall be required for all subsurface stormwater management facilities:
(a) 
Prior to starting any excavation for subsurface facilities, the contractor must notify the Township's Engineer 48 hours in advance for inspection of said facilities. Inspection is required for all subsurface stormwater management facilities at the time of installation and prior to backfilling.
(b) 
Excavation for all subsurface facilities shall be performed in a manner that will minimize compaction of the subsurface facility floor and surrounding areas as well as minimize smearing of the sidewalls of the subsurface facility.
(c) 
The floor and sidewalls of the subsurface stormwater management facility shall be roughened prior to placement of the geofabric and aggregate.
(d) 
Only clean, open graded aggregate, free of fines, shall be used in subsurface stormwater management facilities.
(e) 
The top, sides, and floor of all subsurface stormwater management facilities shall be covered with a drainage filtration fabric which meets the requirements of the Pennsylvania Department of Transportation, Publication 408 for Class I Geofabrics.
(f) 
All pipes leading into subsurface stormwater management facilities shall be equipped with screening or water quality devices to prevent debris from entering the system.
(g) 
The floor of all subsurface stormwater management facilities shall be located a minimum of 12 inches above the seasonal high-water table or bedrock limiting zone as established by a soil test pit and site specific soil profile. Depths of less than 12 inches above the limiting zone will only be allowed where it is certified by a registered professional engineer, geologist, or hydrogeologist that the proposed facility will not create an environmental hazard.
(h) 
For all subsurface stormwater management facilities that propose to use infiltration as a means to manage stormwater runoff, infiltration testing must be performed at the same elevation of the invert of the proposed facility to determine a design infiltration rate and dewatering time for the proposed facility. The proposed facility dewatering time must be in accordance with § 109-16B.
(i) 
Inspection points, cleanouts, and overflow facilities shall be provided for all subsurface stormwater management facilities. All inspection points and cleanouts must be located in a configuration that will allow for cleaning and maintenance of the entire subsurface facility.
(j) 
Detailed maintenance instructions and a proposed maintenance schedule must be provided on the plan drawings and provided to the property owner prior to plan approval.
(k) 
All subsurface stormwater management facilities must be located a minimum of 100 feet from any potable water wells.
(4) 
Alternative stormwater management BMPs not mentioned above may be utilized provided that all applicable design criteria within § 109-23 has been met and that the design is in conformance with the current edition of the Pennsylvania Best Management Practices Manual.