A. 
A stormwater management site plan shall be required for each subdivision, land development and regulated activity, unless exempted by § 172-29. The stormwater management site plan shall demonstrate effective control of stormwater runoff and compliance with the stormwater management requirements, standards and design criteria of this chapter. The stormwater management site plan shall be an integral part of each subdivision and land development plan at the preliminary and final plan stage. For the purposes of this section of the chapter, the following activities are defined as regulated activities and shall be considered as land development (in addition to subdivision and land development) for regulation by this chapter:
(1) 
Construction of new or additional impervious or semipervious surfaces (driveways, parking lots, etc.); and
(2) 
Construction of new buildings or additions to existing buildings; and
(3) 
Diversion or piping of any natural or man-made stream channel; and
(4) 
Installation of stormwater management facilities or appurtenances thereto.
(5) 
Alteration of conditions that may increase or alter natural drainage from the existing site.
B. 
Additionally, subdivisions, land developments, and regulated activities shall be in compliance with all stormwater management plans within East Hanover Township watersheds.
A. 
For all regulated earth disturbance activities, erosion and sediment control BMPs shall be designed, implemented, operated, and maintained during the regulated earth disturbance activities (e.g., during construction) to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code and the Clean Streams Law. Various BMPs and their design standards are listed in the Erosion and Sediment Pollution Control Program Manual (E&S Manual) 2, No. 363-2134-008 (April 15, 2000), as amended and updated.
B. 
On parcels regulated under this chapter, stormwater flows onto adjacent property shall not be created, increased, decreased, relocated, or otherwise altered without written notification of the adjacent property owner(s) by the developer, and concurrence by the adjacent property owner. Such stormwater flows shall be subject to the requirements of this chapter.
C. 
Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by SWM BMPs or open channels consistent with this chapter.
D. 
If diffused flow is proposed to be concentrated and discharged onto adjacent property with permission from the receiving property owner, 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 and downstream easements shall be established to provide drainage paths for concentrated discharge, maximum use shall be made of the existing on-site natural and man-made stormwater management facilities.
E. 
For all regulated activities, SWM BMPs shall be implemented, operated, and maintained to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code, the Clean Streams Law (35 P.S. § 691.1 et seq.), and the Storm Water Management Act (32 P.S. § 680.1 et seq.).
F. 
Various BMPs and their design standards are listed in the Pennsylvania Stormwater Best Management Practices Manual (BMP Manual).
G. 
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 172-29:
(1) 
Preparation and implementation of an approved SWM site plan is required.
(2) 
No regulated activities shall commence until East Hanover Township issues written approval of an SWM site plan, which demonstrates compliance with the requirements of this chapter.
(3) 
The Township Engineer shall determine if an SWM site plan is required or if an SWM site plan exemption is warranted.
H. 
SWM site plans approved by East Hanover Township shall be on site throughout the duration of the regulated activity.
I. 
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.
J. 
Impervious areas:
(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 entire development 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 § 172-23 and the peak rate controls of § 172-25 do not need to be applied to existing impervious areas that are not being altered by the proposed regulated activity.
(4) 
In all drainage areas where disturbance is taking place and new impervious surface is added, up to 50% of the existing impervious area may be utilized in the pre-development coverage calculation.
(5) 
The anticipated flooded surface area occurring within the site shall be considered as impervious.
K. 
All regulated activities shall include such measures as necessary to:
(1) 
Protect health, safety, and property;
(2) 
Meet the water quality goals of this chapter by implementing measures to:
(a) 
Minimize disturbance to floodplains, wetlands, and wooded areas.
(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, wherever possible.
(f) 
To the maximum extent practicable, incorporate the techniques for low-impact development practices described in the BMP Manual.
L. 
The design of all facilities over karst geology shall include an evaluation of measures to minimize adverse effects, such as sinkholes and groundwater contamination.
M. 
Infiltration BMPs should 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.
N. 
Normally dry, open top, storage facilities should completely drain both the volume control and rate control capacities over a period of time not less than 24 and not more than 72 hours from the end of the design storm.
O. 
Those proposing regulated activities which do not fall under the exemption criteria provided in § 172-29, shall submit an SWM site plan, consistent with this chapter, to the East Hanover Township Engineer for review. In applying the exemption criteria set forth in § 172-29, the total proposed development is to be calculated, even if the development is to take place in phases. For the purposes of the exemption, impervious surface shall include, but not be limited to, any roof, parking or driveway areas and any new streets and sidewalks. Any areas designed to be gravel or crushed stone shall be assumed to be impervious for the purposes of the exemption criteria in § 172-29.
P. 
Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the commonwealth or wetlands shall be subject to approval by DEP through the joint permit application process or, where deemed appropriate by 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 from DEP. A wetlands report, prepared by a qualified professional, shall be submitted whenever wetlands are disturbed.
Q. 
Roof drains shall not be connected to streets, sanitary or storm sewers or roadside ditches to promote overland flow and infiltration/percolation of stormwater. When it is more advantageous to connect directly to streets or storm sewers, then it shall be permitted on a case by case basis by East Hanover Township.
R. 
Stormwater management facilities, which involve a State Highway, shall be subject to the approval of PennDOT.
S. 
Minimization of impervious surfaces and infiltration of runoff through seepage beds, infiltration trenches, etc., are encouraged, where soil conditions permit, to reduce the size or eliminate the need for detention facilities.
T. 
Where a development site is traversed by watercourses other than permanent streams, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easement 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.
U. 
Title 25 Pa. Code, Chapter 105, Rules and Regulations, apply to the construction, modification, operation or maintenance of both existing and proposed water obstructions and encroachments throughout the watershed, including work in wetlands. Inquiries on permit requirements or other concerns shall be addressed to the DEP, Bureau of Waterways Engineering in Harrisburg. Mailing Address: PA Department of Environmental Protection, Bureau of Waterways Engineering, PO Box 8460, Harrisburg, PA 17105-8460. Site Address: 400 Market Street, 3rd Floor Rachel Carson State Office Building, Harrisburg, PA, 17101.
V. 
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 DEP through the joint permit application process, or, where deemed appropriate by DEP, through the general permit process.
W. 
Stormwater resulting from regulated activities shall not be discharged into sinkholes.
X. 
To the lowest extent possible, incorporate the techniques for low-impact development practices described in the BMP Manual.
A. 
East Hanover Township is located within the Swatara Creek Watershed. The East Hanover Township Board of Supervisors have adopted standards concerning design criteria for this watershed based on Lebanon County guidelines and as recommended by Act 167, the Pennsylvania Storm Water Management Act, 32 P.S. § 680.1 et seq.
B. 
As of the adoption date of this chapter, the Swatara Creek Watershed is considered to be the only stormwater management district in the Township.
C. 
Implementation of these provisions shall be subject to the following requirements:
(1) 
Post-development rates of runoff from any subdivision, land development, or regulated activity shall meet the peak release rates of runoff prior to development that are specified within the design criteria and calculation methodology.
(2) 
Stormwater runoff should not be transferred from one watershed to another. If a transfer cannot be avoided, the peak discharge limits of the receiving watershed shall be satisfied in accordance with Subsection A above.
(3) 
Additional stormwater management districts may be established by the East Hanover Township Board of Supervisors as new watershed or sub-watershed studies are completed. Upon adoption of those new watershed districts or plans by East Hanover Township, the applicable design criteria within the watershed plan shall be satisfied by owners and developers of the affected land.
(4) 
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 for the one-hundred-year event.
(5) 
Site areas. Where the site area to be impacted by a proposed development activity differs significantly from the total site area, only the proposed impact area utilizing stormwater management measures shall be subject to the management district criteria. In other words, unimpacted areas bypassing the stormwater management facilities would not be subject to the management district criteria.
(6) 
Adequate erosion protection shall be provided along all open channels, and at all points of discharge.
Stormwater management planning and stormwater management facilities shall be designed and constructed in accordance with the following:
A. 
General standards.
(1) 
The design of all stormwater management facilities shall incorporate sound engineering principles and practices.
(2) 
All stormwater runoff flowing over the development site shall be considered in the design of the stormwater management facilities.
(3) 
Runoff from impervious areas shall be drained to pervious areas of the development site and the stormwater management control facilities.
(4) 
Stormwater runoff from a development site shall flow directly into a natural watercourse, into an existing storm sewer system or onto adjacent properties in a manner similar to the runoff characteristics of the pre-development flow.
(5) 
A concentrated discharge of stormwater to an adjacent property shall be within an existing watercourse or storm sewer system and enclosed within an easement. All discharges must be to stable areas or conveyances. If the existing waterway or drainage system is not stable, a design must be proposed that when implemented, will ensure a stable conveyance. Downstream easements are required to be established to provide drainage paths for concentrated discharge. Design and construction shall preclude erosion, sedimentation, flooding or similar damage.
(6) 
Where a development site is traversed by watercourses, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easement 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 within BMP areas where mowing is not desired. The drainage easement shall adequately contain the anticipated inundation associated with the identified one-hundred-year floodplain, or be depicted 50 feet from the top of the channel bank for undefined floodplain areas.
(7) 
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 PADEP through the Chapter 105 permit process, or, where deemed appropriate by PADEP, through the general permit process.
(8) 
Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the commonwealth or wetlands shall be subject to approval by PADEP, through the joint permit application process or, where deemed appropriate by PADEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the 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 from PADEP.
(9) 
Any stormwater management facilities regulated by this chapter that would discharge to state highway rights-of-way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT). Stormwater detention basins, retention basins, infiltration basins and similar structures shall maintain a ten-foot isolation from PennDOT right-of-way.
(10) 
Minimization of impervious surfaces and infiltration of runoff through infiltration beds, infiltration trenches, etc., is encouraged, where soil conditions permit, to reduce the size or eliminate the need for detention facilities.
(11) 
Roof drains shall not be connected to streets, sanitary or storm sewers or roadside ditches so as to promote overland flow and infiltration/percolation of stormwater where advantageous to do so. When it is more advantageous to connect directly to streets or storm sewers, then it shall be permitted on a case by case basis, based upon adequate justification to be provided by the applicant.
(12) 
Stormwater management facilities and discharges shall not be located within sinkhole prone areas of carbonate geology, including areas containing sinkholes, closed depressions, fractured limestone traces and limestone rock outcrops.
(13) 
Stormwater facilities that are not located within a street right-of-way shall be centered within an adequate easement of no less than 20 feet in width. Easements shall follow property lines where possible and are to be provided with metes and bounds descriptions that tie to known points and shall close on individual lots.
(14) 
A variety of methods for stormwater detention and retention are available for use. These include surface detention, subsurface detention, use of existing facilities (ponds, etc.) or a combination thereof. Subsurface detention shall be utilized only where the subsurface is stable, the area is not prone to sinkhole formation, and all underground pipes are sealed to prevent leaks.
(15) 
Storage of equivalent stormwater runoff for a portion of a property may be considered in lieu of storage of generated runoff provided:
(a) 
The site is located so that it is physically impossible to detain runoff from the proposed facilities or drainage problems exist upgrade that would impact upon the site or downgrade properties.
(b) 
The impact of generated runoff discharging off site from the subdivision or land development is determined by the Township Engineer to be negligible and not detrimental to adjacent properties.
(c) 
Implementation of equivalent storage shall be determined applicable and feasible by the Township Engineer.
(16) 
Storm sewer pipes, culverts, manholes, inlets, endwalls, endsections, and other stormwater management facilities shall be designed and constructed in accordance with the requirements of the Pennsylvania Department of Transportation, Design Manual Part 2 Highway Design, Publication 13, including amendments thereto, unless specifications are otherwise provided herein. Structures and their installation within or directly connected to existing or intended public rights-of-way shall conform to the current PennDOT Pub 72M, Roadway Construction Standards.
(17) 
Headwalls and endwalls shall be used where stormwater runoff enters or leaves the storm sewer horizontally from a natural or man-made channel. PennDOT Type "DW" headwalls and endwalls shall be utilized. Galvanized metal end sections are also acceptable, but polyethylene flared end sections are prohibited. All headwalls and endwalls and flared end sections with pipes of 12-inch or greater diameter shall be protected from child entry by placing removable stainless steel bars (and compatible mounting hardware), spaced four inches apart across the opening.
Any stormwater management facility designed to store stormwater runoff and requiring a berm or earthen embankment (i.e., detention or retention basin) shall be designed to provide an emergency spillway to handle the one-hundred-year post-development peak flow rate tributary to the basin. The use of inlets and pipes are prohibited for the emergency spillway. Stormwater runoff from existing natural swales and/or other existing drainage conveyors shall not be directed towards or intercepted by the stormwater management facilities. The height of embankment must be set as to provide a minimum 1.0-foot of freeboard above the maximum pool elevation computed when the entire one-hundred-year peak flow rate to the structure passes through the spillway. Rain gardens, with a maximum water depth of 12 inches, shall be exempt from this requirement; however, conveyance of the one-hundred-year peak discharge must be shown to be conveyed in a stable condition. The criteria for design and construction of stormwater management facilities are not the same criteria that are used in the permitting of dams under the DEP Dam Safety Program. Depending upon the physical characteristics of a dam, a dam permit may be required and the design will have to meet the provisions of 25 Pa. Code Chapter 105. Depending on the physical characteristics of a dam, the design could require that anywhere from a one-hundred-year to a probable maximum flood (PMF) storm event be considered. Retention and detention basins shall be designed and constructed according to the following minimum standards:
A. 
The maximum water depth to the base of the emergency spillway shall not exceed six feet in residential areas. Depths up to eight feet are permitted in nonresidential projects, provided minimum six-foot high fencing is provided when depths exceed six feet.
B. 
The minimum top width of dams shall be three feet for all impoundments draining one acre or less, five feet for impoundments draining one to five acres, and eight feet minimum width for impoundments with drainage areas of or exceeding five acres.
C. 
The side slopes of earth fill dams shall not be less than three horizontal to one vertical on both sides of the embankment. However, any portion of the inside berm of an unfenced basin above a proposed water depth of three feet shall have a side slope of five horizontal to one vertical or flatter. All pond areas, including bottoms of non-water quality ponds, side slopes and top of berms, shall be provided with a minimum four inches of topsoil and shall be mulched and seeded with formula B in accordance with PennDOT publication 408, § 804. All areas to receive topsoil should be scarified 12 inches deep before topsoil placement.
D. 
All basins shall be structurally sound and shall be constructed of sound and durable materials. The completed structure and the foundation of all basins shall be stable under all probable conditions of operation. An emergency spillway shall be provided for the basin and shall be capable of discharging the one-hundred-year peak rate of runoff which enters the basin after development, in a manner which will not damage the integrity of the facility and will not create a downstream hazard. Where practical, the emergency spillway shall be constructed in undisturbed ground. An easement for inspection and repair shall be provided when the conveyance structure crosses property boundaries. Downstream drainage easements from the emergency spillway may be required.
E. 
A cutoff or key trench of impervious material shall be provided under all basin berms.
F. 
All discharge control devices with appurtenances (except discharge pipes) shall be made of reinforced concrete and stainless or hot dip galvanized steel. Bolts/fasteners are to be stainless or galvanized steel. Discharge pipes shall conform to the requirements of § 172-18.
G. 
Concrete, polyethylene or welded galvanized steel anti-seep collars compatible with the discharge pipe shall be placed around all basin discharge pipes to increase the seepage length along the pipe by 15% within the saturated zone of the pipe based on a 4:1 phreatic line. The connection of the anti-seep collar to the discharge pipe shall be completely watertight.
H. 
Basin principal spillway outlet structures shall consist of stainless steel orifice plates (and mounting hardware), galvanized or reinforced concrete riser and discharge pipe, and welded structural steel inlet grates (with a bituminous coating). Smooth lined corrugated polyethylene pipe may be used for discharge piping. The use of PVC pipe is prohibited for basin discharge piping except for small applications. Principle spillways with riser pipes where the designed water depth is deeper than 0.4 times the diameter of the riser, shall have an anti-vortex device to prevent reduced capacity of the riser.
(Example, if the top of an 18 inches riser is 100.00, the riser shall have an anti-vortex device if the water is higher than 100.00 + [(18*0.4)/12] = 100.60). Materials used for design shall be specified on the plans.
I. 
All pipes and culverts through dams shall have properly spaced cutoff collars or anti-seep collars.
J. 
Minimum floor elevations for all structures that would be affected by a basin or storm conveyance system shall be two feet above the one-hundred-year water surface elevation.
K. 
An emergency spillway shall be provided to safely pass the peak flow rate of the incoming one-hundred-year storm, with one foot of freeboard between the maximum pool elevation and the top of the embankment. The maximum pool elevation shall be established using the weir equation through the spillway while ignoring discharge flows from the principal spillway and storage volume within the basin. Routing calculations for rate control structures discharging to the ground surface shall ignore exfiltration or infiltration discharges from the structure.
L. 
Except for retention basins, permanent ponds and wetlands, all basins shall have dewatering features such as low flow channels or tile fields. Low flow channels shall be provided with reinforced matting extending two feet beyond the channel. All detention basins shall include an outlet structure designed to completely drain the basin within 24 hours following the end of the design rainfall. However, basins containing groundwater recharge and/or water quality storage shall include an outlet structure designed to fully drain the recharge and/or water quality volume in no less than 24 hours or more than 72 hours.
M. 
Basin discharges to proposed or existing conveyance systems shall require evidence of adequate capacity in the receiving facility.
N. 
The minimum slope of any detention basin bottom surface shall be 2% positive grade toward the outlet, along all flow paths except those basins specifically designed to provide infiltration of stormwater in conformance with the water quality standards of this chapter.
O. 
Detention basin length or basin flow path length shall be at least two times the basin width to facilitate water treatment and infiltration.
P. 
In areas of carbonate geology, retention and detention basins shall:
(1) 
Be placed at least 100 feet from the rim of any sinkhole or closed depression; and
(2) 
Be placed a minimum of 25 feet from rock outcroppings or pinnacles; and
(3) 
Not discharge into a sinkhole; and
(4) 
Be designed and located to prevent groundwater contamination and sinkhole formation, including the use of impermeable liners where deemed necessary to avoid or abate such problems. The construction of clay liners shall conform to the minimum requirements included in the Appendix.[1]
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
(5) 
Be constructed under the supervision of a professional engineer or professional geologist licensed by the commonwealth. A professionally sealed as-built construction report, and plan including relative dates, name(s) of contractor(s), methods of construction, and verification of conformance to plan specifications and good engineering practices shall be provided to the East Hanover Township Planning Department prior to bond reduction requests related to the basin(s).
Q. 
Basins shall not be divided by a property line.
R. 
Vertical pipes, inlets, and other surface water receiving structures shall be installed with trash racks.
Pipes, curbs, gutters, manholes, inlets, headwalls, endwalls, streets, and other stormwater conveyance facilities shall be designed and constructed in accordance with the following:
A. 
Pipes.
(1) 
Pipe trenching and backfilling shall be in accordance with the requirements of the Pennsylvania Department of Transportation, Publication 408 and Roadway Construction Drawings, current edition, unless manufacturer's specifications and the Township Engineer authorize alternative procedures.
(2) 
Pipe sizes and type shall be in accordance with the approved drawings. Minimum pipe size for drainage facilities to be dedicated for municipal ownership shall be 15 inches in diameter and the type shall be corrugated galvanized metal pipe (CMP), smooth lined high density polyethylene pipe (HDPEP), reinforced concrete pipe (RCP) or approved equivalent.
(3) 
Pipes shall be constructed and set to line and grade as shown on approved drawings. All pipes shall be laid on straight runs between drainage structures.
(4) 
Pipes shall be provided with a minimum of 12 inches of cover from the top of pipe barrel to bottom of base course. In unpaved areas, one foot of cover is required to the finished grade.
(5) 
Backfilling shall be to four feet above the top of the proposed pipe elevation or to subgrade, whichever is less, before excavating for the pipe. Additionally, hauling shall not be permitted over pipe with less than four feet of cover.
(6) 
All pipe outlets shall be discharged to natural or man-made waterways and shall be provided with reinforced concrete headwalls or pipe end sections. Pipe outlets shall also be provided with an erosion resistant material or energy dissipaters to calm the anticipated velocity and discharge of stormwater.
(7) 
Underdrains, pavement base drains, or combination storm sewer and underdrains shall be provided at low points, cut sections, poorly drained areas and other areas which, in the opinion of the Township Engineer, are required to provide adequate subsurface drainage to protect the integrity of the street.
(8) 
All storm sewers which cross a street shall be perpendicular to the street center line or within 30° of perpendicular. Vertical and horizontal isolation conflicts with other utilities shall be avoided. Storm sewers within a street shall not cross underneath a curb, especially at curb radii locations.
(9) 
A concentrated discharge of stormwater to an adjacent property shall be within an existing watercourse or otherwise an easement shall be required. Pipe outlets shall also be provided with erosion resistant material or energy dissipaters to calm the anticipated velocity and discharge of stormwater.
A. 
Inlet tops shall be precast concrete top units conforming to the Pennsylvania Department of Transportation, Publication 408, current edition, and as detailed on the Roadway Construction Standards RC-45M drawings providing an eight-inch curb reveal from the gutter grade point. Type "C" inlets with 10 inches hoods that provide a two-inch sump condition may be used with approval from the Township Engineer. The maximum allowable spread of water shall be 1/2 of a through travel lane. Design calculations are required to document the capacity and spacing. Inlets shall be analyzed for collection efficiency and bypass flows from upstream structures shall be accounted for in inlet spacing design. The efficiency of storm inlets shall be supported with calculations based on the FHWA HEC-22. Yard inlets and other nondedicated inlets may be designed with alternative components, subject to Township Engineer approval.
B. 
All inlets over four feet in depth shall be provided with steps for accessibility. Inlets shall be placed along the curbline, gutter line, or edge of paving.
C. 
All inlets in paved areas shall have bicycle safe grates.
D. 
All inlets shall be constructed with concrete flow channels cast in-place in the bottom of each inlet.
E. 
Inlets and manholes shall not be spaced more than 400 feet apart. Manholes or inlets are required at all points of horizontal or vertical deflection.
All new catch basins located in street right-of-way must be marked with high performance preformed thermoplastic markings. Two layer combination with blue/white contrast. Bottom thermoplastic is blue with top layer white. Markings to say "NO DUMPING!" on the first line and "INTO STORM DRAIN" on the second line. Specify Pre-mark® PLUS storm drain marking, or equal. Size shall be 29 inches by five inches.
All channels shall be lined with adequate channel lining material, regardless of the designed velocity or shear stress. Maximum permitted channel velocities are:
A. 
Three feet per second where only sparse vegetation can be established.
B. 
Four feet per second under normal conditions where vegetation is to be established by seeding or sodding.
C. 
Velocities may not exceed four feet per second for newly constructed grass channels, unless appropriately designed and approved by the Lebanon County Conservation District.
D. 
For lined water-carrying channels, the following velocities are permitted:
(1) 
Minimum six-inch rock riprap up to six f.p.s.
(2) 
Minimum nine-inch rock riprap up to eight f.p.s.
(3) 
Asphalt: up to seven f.p.s.
(4) 
Durable bedrock: up to eight f.p.s.
(5) 
Twelve-inch riprap: up to nine f.p.s.
(6) 
Concrete or steel: up to 12 f.p.s.
(7) 
The normal maximum velocity of open channel flows shall not exceed 10 f.p.s.
E. 
The following conditions shall be met for all swales:
(1) 
Swales shall be designed using Manning's equation. Vegetated swales shall be designed based upon accepted "n" factors for the anticipated degree of vegetative retardance. The maximum allowable velocity for an established grass swale is four feet per second.
(2) 
The "n" factors to be used for paved or rip-rap swales or gutters shall be based upon accepted engineering design practices as approved by the Township Engineer.
(3) 
Swale side slopes shall be 2:1 minimum. Side slopes for grass covered swales which will be mowed shall be 3:1 minimum.
(4) 
All swales shall be designed to concentrate low flows to minimize siltation and meandering.
(5) 
All vegetated swales shall have a minimum slope of 1% unless approved by the Township Engineer.
(6) 
Swales shall be centered within a minimum twenty-foot wide easement.
A. 
All streets shall be so designed to provide for the discharge of surface water from their rights-of-way.
B. 
The slope of the crown on proposed streets shall be of an inch per foot. Slope of the center line grade shall be at least 1%. On curbed streets, the right-of-way beyond the street shall be sloped toward the street at of an inch per foot.
C. 
Adequate facilities shall be provided at low points along streets and where necessary to intercept runoff.
D. 
Pipes and basin outlets shall not discharge directly onto or be conveyed onto a public street.
E. 
The maximum allowable spread of water on proposed streets shall be 1/2 of a through travel lane or one-inch less than the curb depth, whichever is less.
F. 
Driveway intersections with streets shall be designed so that street flows are not diverted onto driveways.
G. 
Water flows across street intersections shall not exceed one inch in depth.
H. 
Stormwater roof drains, sump pumps, and pipes, shall not directly discharge water into a street right-of-way or discharge into a sanitary sewer or storm sewer.
A. 
Provisions for stormwater volume reductions are required for areas being developed. Design of the stormwater BMPs shall give consideration to providing groundwater recharge to compensate for the reduction in the percolation that occurs when the ground surface is paved and roofed over. These groundwater recharge measures are required wherever feasible. Soils used for the construction of basins shall have low-erodibility factors ("K" factors).
B. 
The low impact development practices provided in the Pennsylvania Stormwater BMP Manual shall be utilized for all regulated activities to the maximum extent practicable. Water volume controls shall be implemented using the Design Storm Method in Subsection B(1) or the Alternate Method in Subsection B(2) below.
(1) 
The Design Storm Method (CG-1 in the Pennsylvania Stormwater BMP Manual) is applicable to any size of regulated activity. See Appendix[1] for CG-1 Worksheets 1–5, which shall be used to perform the required calculations. This method requires detailed modeling based on site conditions.
(a) 
Do not increase the post-development total runoff volume to surface waters of the Commonwealth for all storms equal to or less than the two-year twenty-four-hour duration precipitation.
(b) 
For modeling purposes:
[1] 
Existing (pre-development) nonforested pervious areas must be considered meadow in good condition.
[2] 
50% of existing impervious area, when present, shall be considered meadow in good condition in the model for existing conditions.
(c) 
If site conditions prevent total removal of the two-year volume increase to surface waters of the commonwealth after all feasible BMP options are considered, the Alternate Method shall be applied [see Subsection B(2) below].
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
(2) 
The Alternate Method provided below should only be used where the volume control requirements of the Design Storm Method are not attainable. See the Appendix[2] for Worksheets 7 and 8, which shall be used to perform the required calculations.
(a) 
Stormwater facilities shall capture at least the first two inches of runoff from all new impervious surfaces.
(b) 
At least the one-first inch of run off from new impervious surfaces shall be permanently removed from the runoff flow (i.e., it shall not be released into the surface waters of this commonwealth). Removal options include reuse, evaporation, transpiration, and infiltration.
(c) 
Wherever possible, infiltration facilities should be designed to accommodate infiltration of the entire permanently removed runoff; however, in all cases at least the first one-half inch of the permanently removed runoff should be infiltrated.
[2]
Editor's Note: Said appendix is included as an attachment to this chapter.
(3) 
Stormwater Calculation Process (as outlined in the PADEP Pennsylvania Stormwater Management Best Management Practices Manual, current version)
(a) 
Stormwater Calculation Process - nonstructural BMPs.
[1] 
Step 1: Provide General Site information (Worksheet 1).
[2] 
Step 2: Identify sensitive natural resources, and if applicable, identify which areas will be protected (Worksheet 2).
[3] 
Step 3: Incorporate nonstructural BMPs into the stormwater design. Quantify the volume benefits of nonstructural BMPs (Worksheet 3).
Proceed to design storm method.
(b) 
For Design Storm Method:
[1] 
Step 4: Estimate the increased volume of runoff for the two-year storm event, using the soil cover complex Curve Number method. Combining Curve Numbers for land areas proposed for development with Curve Numbers for areas unaffected by the proposed development into a single weighted curve number is NOT acceptable. Runoff volume should be calculated based on land use and soil types (Worksheet 4).
[2] 
Step 5: Design and incorporate structural and nonstructural BMPs that provide volume control for the two-year volume increase indicated on Worksheet 4. Provide calculations and documentation to support the volume estimate provided by BMPs. For nonstructural BMPs, provide nonstructural BMP checklists to demonstrate that BMPs are appropriate. Indicate the volume reduction provided by BMPs (Worksheet 5). Note: If the designer is unable to incorporate the two-year volume increase after all feasible BMP options have been considered, the designer proceeds to the Alternate Method described below.
[3] 
Step 6: Provide detailed routing analysis to demonstrate peak rate control for the one-year through one-hundred-year storm events. This routing should consider the benefits of BMPs. Provide additional detention capacity if needed. Note: there are no exemptions from the peak rate analysis except as permitted under § 172-29.
Proceed to Water Quality Calculations (Step 7). See § 172-24.
(c) 
For Alternate Method:
[1] 
Step 4: Capture the first two inches of runoff from all contributing impervious surfaces. The first one-inch of runoff should be permanently removed and not be released to the surface waters of the commonwealth. The other one inch of runoff should be detained. Compute runoff volumes using Worksheet 7.
[2] 
Step 5: Design and incorporate structural and nonstructural BMPs that provide permanent removal for the PRV and extended detention. The removal options for PRY include reuse, evaporation, transpiration, and infiltration. Infiltration for the first 0.5 inch is encouraged. Documentation to support the computations for volumes can be provided using Worksheet 8. For nonstructural BMPs, checklists can be used to demonstrate that selected BMPs are appropriate. Indicate the volume reduction provided by BMPs on Worksheet 8.
[3] 
Step 6: Provide detailed routing analysis to demonstrate peak rate control for the one-year through one-hundred-year storm events. This routing should consider the benefits of BMPs. Note: There are no exemptions from the peak rate analysis except as permitted under § 172-29.
Proceed to Water Quality Calculations (Step 7). See § 172-24.
(4) 
To comply with Subsections B(1) or (2) above, the land developer MAY submit original and innovative designs to the Township Engineer for review and approval. Such designs may achieve the objectives through a combination of BMPs.
C. 
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 facility and the seasonal high water table and/or bedrock (limiting zones).
(b) 
An infiltration and/or percolation rate sufficient to accept the additional stormwater load and drain completely as determined by field tests conducted by the developer's/landowner's professional designer.
[1] 
The recharge volume provided at the site shall be directed to the most permeable hydrologic soil group (HSG) available.
[2] 
The recharge facility shall be capable of completely infiltrating the impounded water within 72 hours subsequent to any storm event.
D. 
A detailed soils evaluation of the project site shall be performed to determine the suitability of recharge facilities. The evaluation shall be performed by a qualified professional, and at a minimum, address soil permeability, depth to bedrock, susceptibility to sinkhole formation, and subgrade stability. The general process for designing the infiltration BMP shall be:
(1) 
Analyze hydrologic soil groups as well as natural and man-made features within watershed to determine general areas of suitability for infiltration practices.
(2) 
Provide field test(s) to determine appropriate percolation rate and/or hydraulic conductivity.
(3) 
Design infiltration structure for required storm volume based on field determined capacity at the level of the proposed infiltration surface.
E. 
Extreme caution shall be exercised where infiltration is proposed in geologically susceptible areas such as limestone areas. Extreme caution shall also be exercised where salt or chloride would be a pollutant since soils do little to filter this pollutant and it may contaminate the groundwater. It is also extremely important that the design professional evaluate the possibility of groundwater contamination from the proposed infiltration/recharge facility and recommend a hydrogeologic justification study be performed if necessary. Whenever an SWM BMP 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 SWM BMPs over limestone formations shall include measures to prevent groundwater contamination and, where necessary, instability resulting from sinkhole formation. The Township may require the installation of an impermeable liner in SWM basins. A detailed hydrogeologic investigation may be required by the Township.
(1) 
The Township may require the developer to provide safeguards against groundwater contamination for uses which may cause groundwater contamination, should there be a mishap or spill.
(2) 
It shall be the developer's responsibility to verify if the site is underlain by limestone. The following note shall be attached to all SWM site plans and signed and sealed by the developer's engineer/surveyor/landscape architect/geologist:
______________________, certify that the proposed detention basin (circle one) is/is not underlain by limestone.
F. 
If the developer's professional consultant can prove through analysis that the development site is located in an area underlain by carbonate geology, and such geologic conditions would likely result in sinkhole formations, then the site may be exempted from groundwater recharge requirements. However, the development site shall be required to meet all other hydrologic and water quality management standards as mandated by this chapter.
G. 
Where pervious pavement is proposed for parking lots, recreational facilities, nondedicated streets, or other areas, pavement construction specifications shall be noted on the plan.
H. 
Recharge/infiltration facilities may be used in conjunction with other innovative or traditional BMPs, stormwater control facilities, and nonstructural stormwater management alternatives.
A. 
Water quality calculations:
(1) 
Step 7: Determine if the stormwater management design complies with either the Design Storm Method or the Alternate Method. If volume compliance is achieved under either of these methods, proceed to Step 8. If compliance is not achieved, proceed to Step 10.
(2) 
Step 8: Determine if at least 90% of the disturbed site area is controlled by a BMP (maximum disturbed, uncontrolled area of 10%). To be considered "controlled" by a BMP, the disturbed area must either drain to a structural BMP (or series of BMPs) or be offset by a preventive BMP, such as reduced imperviousness or landscape restoration. If at least 90% of the disturbed area is controlled, proceed to Step 9; else proceed to Step 11.
(3) 
Step 9: Total Suspended Solids (TSS) and Total Phosphorus (TP) requirements are considered met. Demonstrate use of specific nitrate prevention/reduction BMPs (Worksheet 10 in Appendix G). If the required BMPs (two primary or four secondary or one primary and two secondary) are proposed within the stormwater management plan, then the water quality requirement for nitrate is achieved. If the required BMPs are not proposed, proceed to Step 10.
(4) 
Step 10: If volume control is not met using either the Design Storm Method or Alternate Method, demonstrate use of specific BMPs for pollutant prevention. Worksheet II in Appendix G.
(5) 
Step 11: Estimate pollutant load from disturbed areas of the site, excluding preventive measures (if proposed). Worksheet 12 in Appendix G.
(6) 
Step 12: Calculate pollutant load reductions with the proposed structural BMPs. Worksheet 13 in Appendix G. If target load reductions are achieved for TSS, TP, and nitrate, then the water quality requirements are met.
A. 
Stormwater runoff calculations for all development sites and regulated activities shall be calculated in accordance with the following computation methodologies:
B. 
Accepted calculation methods.
Method (a)
Applicability
Soil Cover Complex Method
Acceptable for all watersheds (formerly SCS)Preferred for watersheds > 10 acres and for use with detention basin routings
Rational Method
Acceptable for small watersheds and residential underground absorption systems (see Storm Event Criteria below). Recommended for watersheds <10 acres
TR-20, USDA Department of Environmental Protection
Acceptable for all watersheds, especially where full hydrologic computer model is desired
HEC-1 U.S. Army Corps of Engineers
Acceptable for all watersheds, especially where full hydrologic computer model is desired
(a)
Selection of the method of calculation by the design professional shall be based upon the limitations and suitability of each method for the development site. The Township Engineer should be consulted for method alternatives and applicability.
C. 
Storm event criteria.
(1) 
All runoff calculations shall be completed in accordance with the standard guidelines for the selected method of calculation.
(a) 
Rational method. Rainfall intensities shall be obtained from NOAA Atlas 14 or from the PennDOT Storm Intensity-Duration-Frequency Chart provided in the Appendix.[1] Where stormwater runoff hydrographs are produced using the Rational Method, the method shall be "modified" to create a triangular hydrograph with the ascending leg of the hydrograph having a length equal to three times the time of concentration (3xTc) and the descending leg having a length equal to seven times the time of concentration (7xTc) to approximate an SCS type II hydrograph. Alternate "modified" rational methods shall be subject to acceptance by the Township Engineer.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
(b) 
Soil cover complex method. The Soil Conservation Service Type II, twenty-four-hour rainfall distribution shall be used in conjunction with the rainfall depths from NOAA Atlas 14 or consistent with the following table.
(2) 
Established twenty-four hour rainfall depths for the various storm events throughout East Hanover Township are:
Design Storm Frequency
(years)
Rainfall
(inches)
1
2.5
2
3.0
5
4.0
10
4.8
25
5.3
50
6.0
100
6.7
D. 
Stormwater runoff control criteria. Stormwater management shall be accomplished by controlling post-development runoff rates to pre-development runoff rates for the storm events listed as follows:
Post-development Design Storm
(years)
Pre-development Design Storm
(years)
2
1
5
2
10
5
25
25
100
100
E. 
Assumptions and criteria.
(1) 
Runoff calculations shall include a hydrologic and hydraulic analysis indicating volume and velocities of flow and the grades, sizes, and capacities of water carrying structures, sediment basins, retention and detention structures and sufficient design information to construct such facilities. Runoff calculations shall also indicate both pre-development and post-development rates for peak discharge of stormwater runoff from the development site.
(2) 
All pre-development calculations, unless in woodland, shall be based upon the assumption of meadow in good hydrologic condition. Wooded areas shall utilize forest/woodland cover coefficients. Where the site contains existing impervious surface, up to 50% of the impervious area may be considered as an existing pre-development condition. Runoff coefficients and curve numbers shall be selected from the tables in the appendix.
(a) 
Drainage areas tributary to sinkholes or closed depressions shall be excluded from the modeled analysis defining pre-development flows. If left undisturbed during construction, activities areas draining to closed depressions may also be removed from peak runoff rates and post development analysis. New additional contributing runoff shall not be directed to existing sinkholes or closed depressions.
(3) 
Runoff calculations for the pre- and post-development comparison shall evaluate all stormwater events listed within the stormwater runoff control criteria § 172-25F.
(4) 
Post-development analysis shall consider open areas of possible water impoundments receiving rainfall (such as detention basins, rain garden, etc.) to have an impervious cover area of the maximum surface storage area of the water surface correlating to the storm event of interest.
(5) 
Design of stormwater facilities shall be verified by routing the storm event hydrographs through the facilities using the storage indication method. Routings of rational method hydrographs shall determine the critical duration corresponding to the highest peak water surface elevation in the detention facility based on extended runoff inflows for each control storm event, or consist of a methodology approved by the Township Engineer. The combination of rational method hydrographs based on timing shall be prohibited.
(6) 
Pre- and post-development time-of-concentration paths shall be delineated on topographic mapping with the end and beginning of segments clearly identified as well as the lengths and corresponding end elevations used for each segment. The post-development time-of-concentration shall never be greater than the pre-development time-of-concentration for any watershed or subwatershed. Times of concentration shall be based upon the following:
(a) 
The maximum length of overland sheet flow shall be 100 feet before shallow concentrated or open channel flow develops and shall be justified using the methodology presented in Chapter 3 of the NRCS Technical Release 55 (TR-55) to include the following. For pre-development conditions, the sheet flow Manning's n value of 0.24 (dense grasses), 0.40 (woods light underbrush) and 0.80 (woods dense underbrush) shall be used. For post development sheet flow over proposed mowed areas the Manning's n value shall be 0.15. All other Manning's n assignments shall follow generally accepted standards.
(b) 
Travel time for shallow concentrated flows shall utilize the NRCS Methodology using the Velocity Factor Kv (NEH-4 Figure 15.2) in feet/sec.; 20.3 (paved), 16.1 (unpaved), 15.0 (grassed waterway), 7.0 (short grass), 5.0 (woodland) and 2.5 (woodland with heavy litter).
The travel time is calculated as Tt = L/V and V = Kv*S1/2
Where:
Tt = travel time (sec)
L = length (ft)
V = Velocity (ft/sec)
Kv = applicable factor
S = path slope (ft/ft)
(c) 
Overland flows which are concentrated within field depressions, swales, gutters, curbs or pipe collection systems shall be designed using Manning's Equation for time of concentration criteria for open channel conditions between these design points using acceptable Manning's n values.
(7) 
Storm sewer pipes, culverts, gutters, inlets, outlets and swales shall be designed and constructed in accordance with the standards of the PADOT Design Manual, Part 2, Highway Design (latest edition), including the following requirements:
Facility
Minimum Post Development Peak Discharge Requirements
Pipes, gutters and swales
10-year storm
Culverts and cross drains
25-year storm
Bridges and stream crossings
100-year storm
(a) 
All stormwater collection facilities shall investigate and account for bypass scenarios.
(b) 
Conveyance of the one-hundred-year storm event in a safe manner with acceptable hydraulic elevations shall be verified for all systems that:
[1] 
May affect improvements such as buildings (etc).
[2] 
All drainage areas directed to stormwater facilities used for post rate management.
(8) 
Swales shall be designed utilizing Manning's Equation to insure adequate capacity, control of velocity and swale stability. Calculations shall support swale stability for initial conditions (prior to established vegetation) and long term conditions for the required peak flow rate. Vegetated swales shall have a minimum longitudinal slope of 1% and maximum side slopes of 3 to 1, unless specifically designed as a BMP structure. Culvert design shall investigate, at a minimum, inlet, barrel and outlet control conditions.
F. 
Calculation process. A general procedure recommended for site evaluation and stormwater design is as follows:
(1) 
Evaluate factors influencing stormwater runoff, with a goal of limiting earth disturbance, minimizing grading, and reducing or dispersing impervious surfaces.
(2) 
Satisfy the volume control requirements (see § 172-23).
(3) 
Meet water quality (BMP) standards, preferably with BMPs near the source of the runoff (see § 172-24).
(4) 
Calculate and satisfy peak runoff objective, considering all measures other than detention basins.
(5) 
Size detention basins accordingly.
(6) 
Demonstrate compliance with pre-development hydrograph requirements.
A. 
Goals and objectives.
(1) 
Preserve existing natural features, especially those which store, infiltrate or filter water runoff.
(2) 
Infiltrate rainfall to recharge the groundwater table.
(3) 
Use physical (structural) and biological or vegetative (nonstructural) filtration of water runoff to reduce pollutants and remove sediment.
(4) 
Moderate water runoff velocities to minimize erosion and damage to downstream aquatic habitat.
(5) 
Integrate BMPs into the site layout to perform a water quality function and compliment the developed use of the site.
(6) 
Enhance site aesthetics through the use of a variety of BMP techniques and components.
(7) 
Maximize collection and treatment of small storm event (first flush) stormwater runoff which contains the highest concentration of pollutants.
(8) 
Utilize a system of BMP facilities and groundwater recharge devices throughout the site.
B. 
General standards.
(1) 
Water quality shall be maintained through the requirement for BMP design components for all subdivisions, land developments and regulated activities within East Hanover Township, except where other provisions of this chapter provide for plan or stormwater design exemptions. Also exempted are minor subdivisions such as lot additions, lot revisions, division of existing buildings and other plans where no new construction or development is proposed. Revision or expansion projects requiring land development approval with stormwater design shall include measures to retrofit the site with BMPs to maintain or improve the water quality of the stormwater discharges.
(2) 
The required volume control, specified elsewhere herein, shall be detained and treated within BMPs for all areas of the site to be developed.
(3) 
Site designs shall minimize earth disturbance and the generation of stormwater runoff while maximizing pervious areas for treatment of stormwater.
(4) 
All BMPs shall be sized to capture the required control volume, designed according to the BMP criteria within this chapter, constructed properly and maintained regularly.
(5) 
Stormwater runoff which is directly discharged to wetlands, streams, ponds, high quality or exceptional value watersheds or which originates from land uses or activities with higher potential for pollutant loadings (such as auto salvage yards, vehicle service areas, loading/unloading areas, truck centers, etc.) may require the use of additional or specific structural BMPs for pollution prevention and maintenance of water temperatures and quality.
(6) 
Place BMPs near the source of stormwater runoff and treat runoff from impervious surfaces before mixing with runoff from less contaminated sources.
(7) 
Use native vegetation and water tolerant plants. Trees and shrubs shall not be planted on stormwater facility embankments or in other areas where roots may endanger pipes, headwalls, endwalls, spillway structures or other structural facilities.
(8) 
All impervious area runoff shall be directed to BMPs. The volume control shall be provided within each watershed or sub watershed to provide the intended treatment for upstream runoff. Volume control credit will not be allowed toward noncontributing runoff areas.
(9) 
BMP categories used within these regulations are 1) Ponds 2) Wetlands 3) Infiltration Systems 4) Filtering Systems, and 5) Open Channels. The Design Criteria subsection listed hereafter provides specific descriptions of the BMPs within these classifications. Where effectiveness can be demonstrated, alternative BMP designs and concepts may be utilized.
(10) 
Site designs shall include measures to reduce stormwater velocities and collect sediment near the source of the water runoff so that BMPs can be effective in treating water quality and maintenance can be reduced. Recommended facilities are forebays, energy dissipaters, outlet stabilization structures, inlet protection devices, level spreaders, and flow splitters.
(11) 
"A" type soils (very permeable) may require installation of a clay, bentonite or poly liner where water retention is designed, such as with ponds and wetlands.
(12) 
Carbonate geology (limestone or dolomite bedrock) areas require careful evaluation for appropriate BMP design. Facility depths should be minimized and liners may be required.
(13) 
Forebays and micropools are recommended for ponds and required for wetlands. Forebays and micropools should each contain approximately 10% of the required water volume. Forebays should be at least 10 feet long and be baffled from the main basin with a berm of rip rap or similar material, to a depth of one foot below the water quality volume level, to ensure an indirect flow path. Additionally, when forebays are used, a minimum of 90% of the discharge into the facility shall be directed into the forebays.
(14) 
All ponds and wetlands shall be surrounded by a riparian buffer strip of a minimum 25 feet in width. Streams shall be bordered by a riparian buffer strip, a minimum of 25 feet or the width of the floodplain, whichever is greater.
(15) 
Planting of wetland plants is required within created wetlands and encouraged in ponds and other applicable BMPs. Fringe wetland plants may be used on aquatic benches or within shallow pools, while emergent wetlands vegetation should be planted alongside slopes and facility edges.
(16) 
Infiltration, filtering or other BMP systems which are designed to treat the required control volume from small storms shall be preceded by a flow splitter or equivalent bypass device to route larger water volumes around the system.
(17) 
All underground stone and sand BMP systems shall be lined with geotextile fabric on the sides, bottom and top, (double layer on top) have a level (flat) bottom, be underlain by a minimum of two feet of soil or sand above the seasonal high water table and be placed a minimum of 10 feet horizontally from building foundation walls.
(18) 
Infiltration systems with stone shall utilize AASHTO No. 1 or AASHTO No. 3 stone and assume a maximum of 40% voids area.
(19) 
Grass swales should be designed with a flat channel bottom at least two feet in width, with a longitudinal slope of one to 2%. If grass swale slopes exceed 4%, check dams or similar water velocity modifiers should be used.
C. 
Design criteria.
(1) 
The following site factors should be considered in selecting and designing the appropriate BMPs:
(a) 
Total contributing area.
(b) 
Permeability and infiltration rate of the site soils.
(c) 
Slope and depth to bedrock.
(d) 
Seasonal high water table.
(e) 
Proximity to building foundations and well heads.
(f) 
Erodibility of soils.
(g) 
Land availability and configuration of the topography.
(2) 
The following factors should be evaluated when determining the suitability of BMPs for a development site:
(a) 
Peak discharge and required volume control.
(b) 
Stream bank erosion.
(c) 
Efficiency of the BMPs to mitigate potential water quality problems.
(d) 
The volume of runoff that will be effectively treated.
(e) 
The nature of the pollutant being removed.
(f) 
Maintenance requirements.
(g) 
Creation/protection of aquatic and wildlife habitat.
(h) 
Recreational value.
(i) 
Enhancement of aesthetic and property value.
D. 
Examples.
(1) 
Ponds (Basins) are enhancements to conventional detention basins, usually containing a pool of water to perform the BMP function of capturing pollutants to improve the water quality of the discharge. Specific pond types and guidelines are:
(a) 
Wet retention pond. A permanent pool of standing water, normally containing a perimeter aquatic bench of six inches to 18 inches in depth, where pollutants are removed through sedimentation and plant absorption.
(b) 
Extended detention pond. A basin designed to temporarily hold stormwater for an extended period of time to facilitate physical settling of pollutants. These facilities may be normally dry, contain a shallow marsh, have a small wet pool, and often contain a combination of these features. Extended detention ponds usually include a vegetated forebay that is baffled from the main basin with a rip rap mound, a small sized outlet for the water quality storm discharge, a primary outlet for large storm events and a benched basin for varying water depths.
(c) 
Multiple pond. A pond system containing a series of two or more pools or cells to create a longer pollutant removal pathway.
(d) 
Rain garden. An excavated shallow (maximum pending depth of 12 inches) surface depression planted with specially selected native vegetation to treat and capture runoff.
(2) 
Wetlands may be constructed to contain an environment of shallow marsh where pollutants can be removed through a combination of settling, absorption, retention, plant uptake and biological decomposition. Wetland designs are best suited for larger watersheds and must be accompanied by a landscaping plan which specifies plant species, planting arrangement, bed preparation and operation/maintenance requirements. Additionally, wetlands shall be planted with three or more plant species for diversity and survival, plus at least 50% of the wetland area must be planted and maintained in plant cover. Specific wetland types and guidelines are:
(a) 
Shallow wetlands. These systems are configured with several varying levels of marsh areas, containing a meandering water pathway from the forebay to a micropool at the outlet. Water depths usually range from six inches to 18 inches.
(b) 
Pocket wetlands. Wetlands for small locations where a seasonal high water table is needed to help sustain the water elevations.
(3) 
Infiltration systems are designed to capture stormwater runoff and infiltrate it into the ground. These systems are best adapted for small drainage areas and effectively reduce runoff volume, remove many pollutants, recharge the groundwater and contribute to maintaining stream baseflows. Specific infiltration system types and guidelines are:
(a) 
Infiltration trench. Shallow excavations that are lined with geotextile fabric and filled with stone to create an underground water reservoir, which gradually percolates into the surrounding subsoil. Infiltration trenches are especially useful for connection to roof drains. Larger trenches will require an under drain to a stormwater conveyance system.
(b) 
Infiltration basin. A large, open depression (basin), which collects stormwater for percolation. The basin surface should be vegetated with deep rooted plants to enhance infiltration. Soils, slope, geology and hydrogeology may restrict use of these basins.
(c) 
Porous pavement. Low traffic or overflow parking areas may be designed with porous pavement, a porous asphalt layer which permits runoff to drain into an underground stone area where it can infiltrate into the subsoil.
(d) 
Depressed pervious area. These facilities are useful for capturing runoff within a parking lot island. They are designed lower than the surrounding areas, contain permeable soils with a filtration system or a beehive drain and often contain an underdrain for excess runoff. Plants, shrubs and trees enhance performance and aesthetics. Contributing parking areas require curb cuts, curbs with weep holes or similar design to facilitate runoff discharge to the pervious area.
(4) 
Filtering systems are effective for filtering sediment and other pollutants from runoff by passing it through sand, soil, sand/soil mix, vegetation, a structural filter or any combination thereof. Filtered runoff is then infiltrated or drained to other on-site facilities. These systems may be integrated into landscaped areas and parking islands where plantings will add aesthetic enhancements. Specific filtering system types and guidelines are:
(a) 
Sand filter. An underground chamber or bed with sand designed to filter pollutants as water drains through it, with an underdrain system for discharge of the filtered water to a stormwater conveyance system.
(b) 
Bioretention system. These designs utilize a mixture of sand and permeable soil underneath a planted, landscaped depression to collect and treat surface water runoff. Bioretention areas are especially advantageous for parking lot islands and snow storage locations.
(c) 
Riparian buffer strip. Along streams, wetlands and ponds, an area of land which is vegetated with a combination of trees, shrubs and herbaceous plants. This land strip is designed to protect the water resource by filtering pollutants, improving the habitat and cooling the waterways by shading. The riparian buffer strip shall include the one-hundred-year floodplain, or be a minimum of 25 feet wide from the edge of the normal water level, whichever is greater.
(d) 
Vegetated filter strip. These BMPs are characterized by grass or low growing vegetation on a uniformly sloped area which is designed to intercept sheet flow water runoff between an impervious surface and the stormwater conveyance facilities. Vegetated filter strips reduce water velocities and trap sediment and pollutants. They require good vegetation and soil permeability and should be avoided on steep slopes. They are best used along small parking lots, should be a minimum of 20 feet wide in the direction of water flow, and normally are designed equal in size to the impervious area draining to the filter strip.
(e) 
Vegetated swale. A broad, shallow, low gradient swale with a dense stand of medium height vegetation, which is designed to trap pollutants and promote infiltration.
(f) 
Water quality inlet. Underground boxlike structure, such as an oil/grit separator, which is used to remove sediment and hydrocarbons from water runoff originating from parking lots and heavy traffic areas with the potential for petroleum discharges. These facilities are used close to the source of the runoff and currently include other products such as Stormceptor and Vortechnics.
(5) 
Open channels convey, filter and percolate stormwater runoff. They are often used as an alternative to, or component of, a storm sewer system. Specific open channel types and guidelines are:
(a) 
Grass swale. Grass swales filter pollutants as stormwater runoff is drained to other areas. These facilities are best combined with other BMPs and may include check dams or minor depression storage to reduce water velocity and encourage infiltration. An underbedding of mixed sand and soil with a pipe or stone underdrain will improve the use for infiltration and groundwater recharge.
(b) 
Lined channel. Rip rap, concrete or other erosion resistant material may be used to line a channel to prevent scouring and degradation of a water carrying channel.
(6) 
Additional information and requirements. The information, guidelines and requirements of this section of this chapter are intended to provide guidance in the design, construction, operation, and maintenance of BMPs to protect water quality throughout East Hanover Township. It is recognized that BMP technology is relatively new and, therefore subject to continuing modifications and improvements. As such these regulations provide for considerable design flexibility, provided the design is consistent with the standards listed in this chapter. Additionally, it is further intended that comprehensive handbooks and design manuals for BMPs shall be utilized and relied upon for guidance. Recommended sources of information are as follows:
(a) 
Pennsylvania Stormwater Best Management Practices Manual, effective date December 30, 2006.
(b) 
2000 Maryland Stormwater Design Manual, Volumes I and II, prepared by the Maryland Department of the Environment.
(c) 
Minnesota Urban Small Sites BMP Manual, printed July 2001 by the St. Paul Metropolitan Council Environmental Services.
(d) 
D.E.P. Erosion and Sedimentation Pollution Control Program Manual, dated March 2000 from PA DEP.
[Amended at time of adoption of Code (see Ch. 1, General Provisions, Art. I)]
All subdivision and land development plans which propose earthmoving activity shall include erosion and sediment pollution control design to satisfy the requirements of Chapter 102 Pennsylvania Department of Environmental Protection 25 Pa. Code Chapter 92a and/or 102 and the PA Clean Streams Law (35 P.S. § 691.1 et seq.) and to prevent soil erosion, sediment and other pollutants from entering streams, lakes and neighboring properties. In order to demonstrate and maintain compliance with erosion and sediment pollution control requirements, subdividers and land developers shall:
A. 
Prior to earth moving or subdivision/land development plan approval, obtain erosion and sediment pollution control design approval from the Lebanon County Conservation District.
B. 
Obtain applicable NPDES approvals or permits through the Lebanon County Conservation District and the PA DEP, and maintain plans and permits on site.
C. 
Install required erosion and sediment pollution control facilities prior to the start of construction and maintain said facilities during the construction period.
D. 
Preserve and protect natural vegetation where possible.
E. 
Adhere to approved erosion and sediment pollution control design requirements and NPDES standards.
F. 
Inspect weekly and after each runoff event and maintain all erosion and sediment pollution control facilities to insure their effectiveness. Accumulated sediment shall be promptly removed and disturbed areas shall be reseeded or stabilized.
G. 
Design, install and maintain facilities in accordance with the PA DEP Erosion and Sediment Pollution Control Program Manual, March 2000, as amended.
H. 
Include standard erosion and sediment control notes on all plans, as per the list within the Appendix.[1]
[1]
Editor's Note: Said Appendix is included as an attachment to this chapter.
I. 
Be subject to penalties for noncompliance, in accordance with Article VII provisions.
J. 
Construction of temporary roadways (for utility construction, timber harvesting, etc.) shall comply with all applicable standards for erosion and sedimentation control and stream crossing regulations under 25 Pa. Code Chapters 102 and 105. The erosion and sedimentation control plan shall be submitted to the Lebanon County Conservation District for approval and shall address the following, as applicable:
(1) 
Design of roadway systems, including all roads, skid roads, landing areas, trails, and storage and staging areas.
(2) 
Runoff control structures (e.g., diversions, culverts, detention ponds, etc.).
(3) 
Stream crossings for both perennial and intermittent streams.
(4) 
Access to public roadways, including design of rock construction entrance for mud and debris control.
(5) 
A remediation plan for restoring the disturbed area through re-grading, topsoil placement, reseeding, and other stabilization techniques as required.
K. 
Additional erosion and sedimentation control design standards and criteria that must be applied where infiltration BMPs are proposed include the following:
(1) 
Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase, as to maintain their maximum infiltration capacity.
(2) 
Infiltration BMPs shall be protected from receiving sediment laden runoff.
(3) 
The type of protection for infiltration BMPs shall be identified (i.e., orange construction fence surrounding the perimeter of the BMP).
L. 
Maintenance during development of a project shall be the responsibility of the developer and/or landowner and shall include, but not be limited to:
(1) 
Removal of silt and debris from basins, traps, inlet protection, silt fencing, or other structures or measures when capacity of those structures is reached.
(2) 
Periodic maintenance of temporary control facilities such as replacement of straw bale dikes, straw filters or similar measures.
(3) 
Establishment or reestablishment of vegetation by seeding and mulching or sodding of scoured areas or areas where vegetation is not successfully established.
(4) 
Installation of necessary controls to correct unforeseen problems caused by storm events within design frequencies.
(5) 
The contractor or developer shall be responsible for removal of all temporary measures and installation of permanent measures upon completion and stabilization of the project.
M. 
Total maximum daily load (TMDL) requirements.
(1) 
Agricultural activities contributory to a watershed within East Hanover Township containing an established nonpoint source (agriculture) TMDL, shall be conducted in compliance with Chapter 102 (Erosion and Sediment Control), Chapter 91, § 91.36 (general provisions related to manure management) and Act 38 (3 Pa.C.S.A. § 501, nutrient management).
(2) 
This section shall apply to agricultural activities conducted in watersheds where TMDLs are established in the future.