[Ord. 690, 9/10/2009]
A cul-de-sac shall not be permitted unless the applicant can
demonstrate to the satisfaction of the Township Engineer that construction
of a through street is infeasible. A cul-de-sac shall be permitted
only upon the approval of the Board of Supervisors subject to the
following minimum standards:
A. Cul-de-sac streets shall be designed to permit future extension into
adjacent undeveloped property. Unless future extension is clearly
impractical or undesirable, the turnaround right-of-way shall be placed
adjacent to property line and contained within an easement area. A
right-of-way of the same width as the street shall be carried to the
property line in such a way as to permit future extension of the street
into the adjoining tract. At such time as such a street is extended,
the overage created by the turnaround outside the boundaries of the
extended street shall revert in ownership to the property owners fronting
on the cul-de-sac turnaround.
B. Permanent cul-de-sac streets shall be kept to a minimum and shall
not exceed 500 feet in length or serve as access to more than 12 dwelling
units, whichever is more restrictive, unless specifically authorized
by the Board of Supervisors. The minimum length of a cul-de-sac shall
be 250 feet. For the purposes of this chapter, cul-de-sac length is
measured from the intersection of the proposed right-of-way lines
of the intersecting streets, or in the case of a proposed cul-de-sac
intersecting an existing street, from the intersection of the proposed
right-of-way line and ultimate right-of-way line of the existing street,
to the center of the turnaround area.
C. Cul-de-sac streets, whether permanent or temporary, shall be provided
with a turnaround at the closed end having a minimum radius to the
edge of the finished street or curbline of not less than 40 feet.
Permanent cul-de-sac streets shall be provided at the terminus with
a right-of-way radius of 60 feet.
D. A planted island may be provided in the center of the cul-de-sac
turnaround, which shall be maintained by a lot owner or homeowners'
association. The planted island shall have a radius of 30 feet with
a twenty-foot-wide cartway around the island. A fifty-foot paving
radii shall be provided to transition the cartway at the entrance
and exit of the turnaround. The turnaround shall be restricted to
one-way traffic. Landscaping of the island shall be subject to the
approval of the Township.
E. Commercial and industrial cul-de-sac streets shall be reviewed for
adequacy by the Township Engineer. When deemed necessary by the Township
Engineer, additional cartway and/or right-of-way radius may be required.
F. A snow storage area shall be provided along the right-of-way of the
turnaround. The snow storage area shall be contained within an easement
not less than 15 feet measured from the right-of-way line and of sufficient
length as deemed necessary by the Township to provide adequate snow
storage area.
G. Prospective purchasers of any property located either entirely or
partially on a temporary cul-de-sac, as defined above, shall be advised
by the owners of such property or their authorized agents or representatives
that such property is so located on a temporary cul-de-sac. Actual
purchasers of any property located either entirely or partially on
a temporary cul-de-sac shall signify, in writing, that they have been
advised that the property to be purchased is either entirely or partially
on a temporary cul-de-sac. A signed copy of such writing shall be
delivered and received by the Township before settlement of the property
takes place.
H. Drainage, where feasible, shall be toward the open end of the cul-de-sac.
[Ord. 690, 9/10/2009; as amended by Ord. 737, 1/19/2017]
1. A drive-through facility is any vehicle-related commercial facility
where a service is provided, or goods, food, or beverages are sold,
to the operator of or passengers in a car without the necessity of
the operator or passengers disembarking from the vehicle. Any facility
which proposes a drive-through or drive-up window as an accessory
facility to a retail, service, financial, eating place, or other use
where customers are served in their vehicles shall be subject to the
following requirements.
2. General standards. A drive-through facility is subject to the following
standards:
A. The drive-through facility shall be designed so as not to impede
or impair vehicular and pedestrian traffic movement or exacerbate
the potential for pedestrian/vehicular conflicts.
B. A drive-through facility with the drive-through service area/facility
located in an existing or proposed shopping center shall have circulation
patterns that are integrated with that of the center.
C. An on-site circulation pattern is to be provided for drive-through
facility traffic that separates such traffic from that of walk-in/sit
down/takeout patrons.
D. The driveway entrance and exit lane of a drive-through facility must
be set back at least 100 feet from an intersection.
3. Drive-through lanes and bypass/escape lanes.
A. A bypass lane/escape lane shall be provided for all drive-through
facilities.
B. The drive-through lanes shall not be the sole ingress and egress
to the site.
C. The design of a drive-through lane and bypass lane/escape lane shall
minimize the blocking, crossing, or passing through of off-street
parking areas and minimize crossing of, or the need to be crossed
by, pedestrian accessways for patrons.
D. Drive-through lanes shall be marked by signs which indicate the entrance
and exit for the drive-through lane. The direction of traffic flow
for the drive-through lane and bypass lane/escape lane shall be clearly
marked.
E. Delayed service parking areas shall be located a minimum of 20 feet
from the point where the drive-through lane and bypass lane/escape
lane merge.
4. Stacking distance.
A. A stacking area is to be provided for vehicles waiting for service
in the drive-through lane that is separated from other traffic circulation
on the site. Stacking shall not be provided in parking aisles or in
driveways provided for on-site circulation.
B. The stacking distance shall be as follows:
|
Use
|
Maximum Number of Vehicles
|
Lane Length
(feet)
|
---|
|
Restaurant
|
6
|
132
|
|
Bank
|
6
|
132
|
|
Car wash
|
10
|
220
|
|
Dry cleaner
|
2
|
44
|
|
Pharmacy
|
7
|
154
|
|
Other uses
|
6
|
132
|
5. Lane width.
A. Drive-through lanes are to be separated from the bypass lane/escape
lane and parking aisles by painted lines. The lanes shall be a minimum
of 12 feet wide. If two or more parallel drive-through lanes are provided,
they shall each be a minimum of 10 feet wide.
B. A bypass lane/escape lane shall be a minimum of 10 feet wide.
6. Application requirements. A traffic impact study shall be submitted
to provide information which will be used to determine the necessary
stacking area and the impact the proposal will have upon local traffic
circulation. The traffic impact study shall address the following
issues:
A. Nature of the product or service being offered.
B. Method by which product or service is being offered (e.g., window
service or brought to vehicle by employee).
C. Time required to service typical customer.
D. Arrival rate for patrons.
F. Anticipated vehicular stacking required.
G. Anticipated traffic generation.
H. Diagram of traffic flow, stacking and pedestrian crossings.
[Ord. 690, 9/10/2009]
All curbs shall be constructed in accordance with the Warminster
Township Specifications and Design Standards for Streets and Roads.
[Ord. 690, 9/10/2009; as amended by Ord. 737, 1/19/2017]
The owner, developer, or subdivider shall provide stormwater management in accordance with Chapter
26, Part
4, Stormwater Management, Chapter
26, Part
5, Neshaminy Creek Watershed Stormwater Management, Pennypack Creek Watershed Stormwater Management Ordinance, and as follows:
A. Applicability.
(1)
This section shall apply to all areas of Warminster Township.
Regulated activities include:
(c)
Construction of new or additional impervious surfaces (driveways,
parking lots, etc.).
(d)
Construction of new buildings or additions to existing buildings.
(f)
Diversion or piping of any natural or man-made stream channel.
(g)
Installation of stormwater systems or appurtenances thereto.
(h)
Prohibited or polluted discharges.
(i)
Alteration of the natural hydrologic regime.
(j)
Nonstructural and structural stormwater management best management
practices (BMPs) or appurtenances thereto.
(2)
Stormwater management design and criteria such as stormwater runoff peak rate requirements and districts, runoff calculation methodology, stormwater management plan requirements, operations and maintenance requirements, etc., shall be as described in this section, the Chapter
26, Part
4, Stormwater Management, Chapter
26, Part
5, Neshaminy Creek Watershed Stormwater Management, and Pennypack Creek Watershed Stormwater Management Ordinance.
(3)
The standards contained in this section shall apply as minimum
design standards; however federal, state, and other Warminster Township
regulations may impose additional standards subject to their jurisdiction.
The more stringent requirements of this section, federal, state, and
other Warminster Township regulations shall apply to any activity
which requires compliance with other ordinances and regulations of
Warminster Township.
(4)
Earth disturbance activities and associated stormwater management
controls are also regulated under existing state law and implementing
regulations. This section shall operate in conjunction with those
parallel requirements; the requirements of this section shall be no
less restrictive in meeting the purposes of this section than state
law.
(5)
No regulated activities within the municipality shall commence
until the requirements of this section and all other applicable stormwater
management criteria are met.
(6)
All best management practices (BMPs) used to meet the requirements
of federal, state, and Warminster Township regulations shall conform
to the state water quality requirements and any more stringent requirements
as set forth by the Township.
(7)
Developers shall construct and/or install stormwater management
facilities, on site and off site, as necessary to meet the stormwater
management design and criteria provided by these and other Warminster
Township requirements and to:
(a)
Prevent erosion damage and to satisfactorily carry off, detain
or retain, and control the rate of release of stormwater.
(b)
Manage the anticipated peak discharge from property being subdivided
or developed and existing runoff being contributed from all land at
a higher elevation in the same watershed.
(c)
Convey stormwater along or through the property to a natural
outfall. If a developer concentrates dispersed stormwater flow or
redirects stormwater flow to exit at another location on the property,
the developer is responsible for constructing an adequate channel
on the adjacent property and on all downstream properties until a
natural outfall is reached.
1)
Natural outfall shall have sufficient capacity to receive stormwater
without deterioration of the facility and without adversely affecting
property in the watershed. This natural outfall may be a river, creek
or other drainage facility so designated by Warminster Township for
the proposed system.
(8)
Additional studies and higher levels of control than the minimum
provided in these and other Warminster Township requirements and criteria
may be required by the Board of Supervisors to ensure adequate protection
to life and property.
B. Retention of existing watercourses and natural drainage features.
(1)
Whenever a watercourse, stream or intermittent stream is located
within a development site, it shall remain open in its natural state
and location and shall not be piped.
(2)
The existing points of natural drainage discharge onto adjacent
property(ies) shall not be altered without the written approval of
the affected property owners.
(3)
No stormwater runoff or natural drainage shall be so diverted
as to overload existing drainage systems (including existing stormwater
management facilities) or create flooding.
(4)
The Board of Supervisors may require a developer to provide a permanent easement along any watercourse located within or along the boundary of any property being subdivided or developed. The purpose of any such easement shall be for the maintenance of the channel of any watercourse; and the terms of the easement shall prohibit excavation, the placing of fill or structures and any alterations which may adversely affect the watercourse. The easement shall be provided for Zone 1 of the riparian buffer in accordance with §
22-602, Subsection
8. The developer will retain the easement until such time as one of the following is accomplished:
(a)
The easement is offered for dedication by the developer and
accepted by Warminster Township.
(b)
If an easement acceptable to the Township is established, the
maintenance shall then be the responsibility of the individual lot
owners over whose property the easement passes. For land developments,
the maintenance shall then be the responsibility of the owner.
(c)
A homeowners' association or other approved legal entity, approved
by Warminster Township, assumes responsibility for the maintenance
of the development, including the retention of the watercourse easement.
C. Runoff control measures or best management practices (BMPs).
(1)
Stormwater runoff which may result from regulated activities shall be controlled by permanent stormwater runoff BMPs that will provide the required standards within this section, Chapter
26, Part
4, Stormwater Management, Chapter
26, Part
5, Neshaminy Creek Watershed Stormwater Management, and Pennypack Creek Watershed Stormwater Management Ordinance, or other requirements of Warminster Township. The methods of stormwater control or best management practices (BMPs) which may be used to meet the required standards are described in this section and "Pennsylvania Stormwater Best Management Practices Manual," December 2006, as amended. The choice of BMPs is not limited to those referenced in this section and/or the manual. Any selected BMP must meet or exceed the required standards.
(2)
Any stormwater facility located on state highway rights-of-way
shall be subject to approval by the Pennsylvania Department of Transportation.
(3)
Developers are encouraged to use BMPs other than the minimum
BMPs specified in this subsection, if appropriate, to provide for
additional water quality improvement and groundwater recharge. In
evaluating potential stormwater BMPs, the order of preference shall
be as follows:
(d)
Minimum first flush detention or dual purpose detention (where
appropriate).
(4)
Infiltration best management practices (BMPs). Infiltration
BMPs shall be designed in accordance with the design criteria and
specifications in the PA BMP Manual and shall meet the following minimum
requirements:
(a)
A detailed soils evaluation of the project site shall be performed to determine the suitability of infiltration BMPs per protocol in Chapter
26, Part
4, Stormwater Management, Chapter
26, Part
5, Neshaminy Creek Watershed Stormwater Management, and Pennypack Creek Watershed Stormwater Management Ordinance. 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 site testing shall include adequate sampling of all portions of the site not limited by one-hundered-percent protected natural resources to determine areas of the property which are suitable for infiltration BMPs. The general process for designing infiltration BMPs shall be:
1)
Analyze hydrologic soil groups as well as natural and man-made
features within the site to determine general areas of suitability
for infiltration BMPs.
2)
Provide field testing data at the elevation of the proposed infiltration zone (bottom surface of the infiltration facility) to determine appropriate percolation rate and/or hydraulic conductivity. Field testing guidelines are identified in Appendix B of Chapter
26, Part
4, Stormwater Management, Appendix A of Chapter
26, Part
5, Neshaminy Creek Watershed Stormwater Management, and the Pennypack Creek Watershed Stormwater Management Ordinance.
3)
Design infiltration BMPs for required stormwater volume based
on field-determined capacity per Subsection C(4)(a)2 above.
(b)
Soil characteristics. Subject to the specific considerations
in Subsection C(4)(f) below:
1)
Infiltration BMPs are particularly appropriate in hydrologic
soil groups A and B, as described in the SCS TR-55 Manual.
2)
Low-erodibility factors ('K' factors) are preferred
for the construction of basins.
3)
There shall be an infiltration and/or percolation rate sufficient
to accept the additional stormwater load and to drain completely as
determined by field tests.
4)
A minimum of 10 feet of undisturbed fill or compacted impermeable
material shall separate the foundation wall of any building and an
infiltration BMP.
5)
A minimum of 50 feet of undisturbed fill or compacted impermeable
material shall separate water supply wells and an infiltration BMP.
6)
A minimum of 50 feet shall separate a septic system disposal
area and an infiltration BMP unless specific circumstances allow for
a reduced separation distance.
7)
Infiltration in native soils without prior fill or disturbance
is preferred but not always possible. Areas that have experienced
historic disturbance or fill are suitable for infiltration provided
sufficient time has elapsed and the soil testing indicates that infiltration
is feasible. In disturbed areas it may be necessary to infiltrate
at a depth beneath soils that have previously been compacted by construction
methods or long periods of mowing.
8)
The infiltration system shall have positive overflow controls
to prevent storage within one foot of the finished surface grade.
9)
Surface inflows shall be designed to prevent direct discharge
of sediment into the infiltration system.
(c)
Any infiltration BMP shall be capable of completely infiltrating
the impounded water within 48 hours from the peak of the storm.
(d)
Special attention shall be paid to proper installation of infiltration-oriented
stormwater management systems during construction and to careful avoidance
of soil compaction during site development.
(e)
Caution shall be exercised where salt or chloride would be a
pollutant since soils do little to filter this pollutant, and it may
contaminate the groundwater. Caution shall be exercised where infiltration
is proposed in source water protection areas. The qualified design
professional shall evaluate the possibility of groundwater contamination
from the proposed infiltration/recharge facility and perform a hydrogeologic
justification study if required by the Township Engineer.
(f)
Infiltration BMPs shall be constructed on soils with an infiltration
rate of a minimum of 0.25 inch per hour, including a safety factor
of 50% applied for design purposes (e.g., for soil which measured
0.5 in/hr, the BMP design should use 0.25 in/hr to insure safe infiltration
rates after construction) and shall have the following separation
between the bottom of the facility and seasonal high water table and/or
bedrock and/or groundwater (limiting zones);
1)
For runoff from impervious surfaces associated with residential
land use and/or pervious surface runoff associated with both residential
uses and nonresidential uses: a minimum depth of 36 inches between
the intended bottom of facility and limiting zones.
2)
For runoff from impervious surface associated with nonresidential
uses: a minimum depth of 36 inches between the bottom of facility
and limiting zones. The minimum required separation between the limiting
zone may be increased at the Township's discretion if project
specific conditions, such as anticipated contaminants, dictate greater
prevention of groundwater contamination.
3)
For rooftop runoff: a minimum depth of 24 inches between the
intended bottom of the facility and limiting zones.
(g)
Soils with infiltration rates in excess of 6.0 inches per hour
may require an additional soil buffer, such as an organic layer over
the bed bottom, if the cation exchange capacity (CEC) is less than
five and pollutant loading is expected to be significant.
(h)
All infiltration BMPs shall be designed to, as a minimum:
1)
Provide adequate storage to accommodate the volume of runoff
calculated as the difference between the predevelopment runoff volume
and the post-development runoff volume based on the largest required
design storm.
2)
Control the post-development peak rate of runoff to the predevelopment
peak rate of runoff for design storms greater than one-year, twenty-four-hour
storm.
3)
Provide an overflow or spillway which safely permits the passing
of runoff greater than that occurring during the largest design storm.
4)
Release rate requirements of the Chapter
26, Part
4, Stormwater Management, Chapter
26, Part
5, Neshaminy Creek Watershed Stormwater Management, and Pennypack Creek Watershed Stormwater Management Ordinance may be met by use of infiltration BMPs alone or in combination with other facilities.
(5)
Wet pond and artificial wetland best management practices (BMPs).
(a)
Wet pond and artificial wetland BMPs shall be designed in accordance
with the design criteria and specifications in the PA BMP Manual.
(b)
Artificial wetland facilities shall meet the following minimum
requirements:
1)
At least 80% of the wetland shall be developed as a shallow
water emergent wetland, with a water depth between eight inches and
12 inches. It is recommended that the shallow water emergent wetland
area be separated into high marshes (zero to six inches below normal
water surface) and low marshes (six to 18 inches below normal water
surface). The remainder shall be constructed as open water with depths
between two feet and four feet.
2)
The length of the constructed treatment wetland between the
inflow and outflow points shall be maximized. The minimum length to
width ratio for all wetland systems shall be 3:1. A medial berm may
be used to reduce flow width and improve flow distribution and length.
3)
Constructed treatment wetlands shall be constructed on hydric
or wet soils and/or soils which have an infiltration rate of less
than 0.1 inch per hour. A base flow of 0.10 cfs/50 acres is recommended
for all constructed treatment wetland facilities, unless a source
of recharge is available such as a natural spring or well.
4)
A shallow forebay shall be provided adjacent to all inflow areas,
unless the inflow area provides less than 10% of the total inflow
to the facility. The forebay serves to enhance sediment trapping and
pollutant removal, as well as concentrating accumulated sediment in
an area where it can be readily removed. To create a forebay, a baffle
may be introduced to restrict hydraulic communication between the
inlet and the remainder of the retention basin. The minimum standards
for forebays are as follows:
a)
Minimum length shall be 10 feet.
b)
Sufficient storage volume shall be provided to trap sediment
between clean-out intervals (typically five to 15 years). At a minimum,
the forebay shall be sized to contain 0.25 inch per impervious acre
of contributing drainage.
c)
The forebay shall be three to five feet deep.
d)
The height of the berm or baffle separating the forebay from
the pond shall be one foot below the one-year water surface elevation
or at the normal water surface elevation, whichever is higher.
e)
The forebay shall be accessible and stabilized to accommodate
equipment used in removing accumulated sediment.
5)
A planting plan prepared by a landscape architect shall be developed
for the artificial wetland showing all proposed aquatic, emergent,
and upland plantings. The planting plan shall be developed to provide
a diversity of species resulting in a dense stand of wetland vegetation.
(c)
Retention basins/wet ponds shall meet the following minimum
requirements:
1)
Constructed treatment wetlands shall be constructed on hydric
or wet soils and/or soils which have an infiltration rate of less
than 0.1 inch per hour. A base flow of 0.10 cfs/50 acres is recommended
for all constructed treatment wetland facilities, unless a source
of recharge is available such as a natural spring or well.
2)
The length of the pond between the inflow and outflow points
shall be maximized, and an irregular shoreline shall be provided.
The minimum length to width ratio for all wetland systems shall be
2:1.
3)
A shallow forebay shall be provided adjacent to all inflow areas,
unless the inflow area provides less than 10% of the total inflow
to the facility. The forebay serves to enhance sediment trapping and
pollutant removal, as well as concentrating accumulated sediment in
an area where it can be readily removed. To create a forebay, a baffle
may be introduced to restrict hydraulic communication between the
inlet and the remainder of the retention basin. The minimum standards
for forebays are as follows:
a)
Minimum length shall be 10 feet.
b)
Sufficient storage volume shall be provided to trap sediment
between clean-out intervals (typically five to 15 years). At a minimum,
the forebay shall be sized to contain 0.25 inch per impervious acre
of contributing drainage.
c)
The forebay shall be three to five feet deep.
d)
The height of the berm or baffle separating the forebay from
the pond shall be one foot below the one-year water surface elevation
or at the normal water surface elevation, whichever is higher.
e)
The forebay shall be accessible and stabilized to accommodate
equipment used in removing accumulated sediment.
f)
Nonerodible material shall be used to construct the forebay
berm. Armoring, such as riprap, is generally preferred to stabilize
the upgradient face of the berm.
4)
Wet ponds shall be designed with public safety as a primary
concern. An aquatic safety bench shall be provided around the perimeter
of the permanent pool. The aquatic safety bench shall be a minimum
of 10 feet wide with a maximum slope of 10:1. A 3:1 slope shall lead
from the edge of the safety bench toward the deep water portion of
the pond for at least 15 feet. Slopes on the remainder of the pond
below the permanent pool elevation shall be a maximum of 2:1. The
portion of the pond devoted to storage and peak attenuation of storm
runoff, the terrestrial bench, shall be nearly level and shall be
planted with shrubs and trees that shade the pool and mitigate thermal
impacts. Terrestrial bench shall be at least 10 feet wide.
5)
A planting plan prepared by a landscape architect shall be developed
for the wet pond showing all proposed aquatic, emergent, and upland
plantings.
6)
The perimeter slope above the terrestrial bench shall have a
maximum slope of 4:1.
7)
Wet ponds shall have a deep water zone to encourage gravity
settling of suspended fines and to prevent stagnation and possible
eutrophication. The maximum depth shall not exceed eight feet.
8)
Wet ponds shall be capable of being substantially drained by
gravity flow. Where possible, wet ponds shall be equipped with a manually
operated drain that can be secured against unauthorized operation.
9)
The preferred method of low flow discharge from a pond is a
submerged, reverse-slope pipe that extends downward from the outlet
structure to an inflow point one foot below the normal water surface
elevation. Alternative methods may be employed and shall include provisions
to prevent debris clogging of the structure.
(6)
Bioretention facilities and rain gardens.
(a)
All concentrated discharges directed to a bioretention facility
shall be conveyed through a pretreatment filter strip. The filter
strip shall be designed to reduce the incoming velocities and to filter
out coarser sediment particles. Examples of pretreatment filter strips
include sand or gravel diaphragms, grass swales, sand filters, stone
check dams, etc.
(b)
Bioretention facilities shall meet the following minimum standards:
1)
Minimum width of 10 feet, excluding side slopes.
2)
Minimum length of 20 feet.
3)
Minimum length to width ratio of 2:1.
4)
Maximum shallow ponding depth of six inches.
5)
Minimum planting soil bed depth of two feet for herbaceous plants
and three feet for trees and shrubs.
(c)
All bioretention facilities shall incorporate an organic mulch
layer. The organic mulch layer shall be standard landscape style,
single or double, shredded hardwood mulch or chips. The mulch layer
shall be well aged, uniform in color, and free of other materials
such as weed seed, soil roots, etc. The mulch layer shall be applied
to maximum depth of three inches. Grass clippings shall not be used
as mulch material.
(d)
Planting soil shall be a loam soil capable of supporting healthy
vegetative cover. Soils shall be amended with a composted organic
material consisting of 20% to 30% compost material and 70% to 80%
soil base, preferably topsoil. A soil analysis of the planting bed
soil shall verify that the soils meet the following:
1)
pH range between 5.5 and 6.5.
2)
Organic matter content 5% to 10%.
3)
Magnesium provided at 35 pounds per acre minimum.
4)
Phosphorus provided at 75 pounds per acre minimum.
5)
Potassium provided at 85 pounds per acre minimum.
6)
Soluble salts shall be less than 500 ppm.
7)
Clay content between 0% and 10%.
8)
Silt content between 30% and 55%.
9)
Sand content between 35% and 60%.
(e)
All bioretention facilities shall incorporate landscaping and
shall be provided with a landscaping plan prepared by a landscape
architect that meets the following standards:
1)
Plant species shall be selected based on the ability to tolerate
urban stresses, such as pollutants, variable soil moisture and ponding
fluctuations. A list of acceptable native plants is provided in the
PA BMP Manual.
2)
A minimum of three species each of trees, shrubs, and/or herbaceous
plants shall be selected to insure diversity.
(f)
In cases where the coefficient of permeability of the existing
soils is less than 0.1 inch per hour, an underdrain facility shall
be provided. The underdrain facility shall be protected from sediment
accumulation with filter fabric.
(g)
Where underdrain is proposed, an eight-inch deep sand bed shall
be provided between the planting soil bed and the underdrain system.
(h)
An overflow spillway or storm drain shall be provided to adequately
convey the fifty-year storm event. The spillway or storm drain facility
shall be set above the maximum proposed ponding depth.
(7)
Permeable pavement.
(a)
The type of permeable pavement material (perforated brick pavers,
concrete grid pavers, porous bituminous concrete, porous concrete,
etc.) shall be determined based on required surface infiltration rates,
total surface area of pavement, and proposed use of the pavement/parking
area.
(b)
Permeable pavements shall be constructed with a perimeter overflow
edge. The edge is intended to intercept runoff from the pavement if
for any reason the permeable surface were to become clogged. The perimeter
overflow edges shall connect directly into the base layer of the pavement.
(c)
Soil percolation/infiltration rates shall equal or exceed 0.2
inch per hour. Soils with infiltration rates in excess of 6.0 inches
per hour may require an additional soil buffer, such as an organic
layer over the bed bottom, if the cation exchange capacity (CEC) is
less than five and pollutant loading is expected to be significant.
(d)
Permeable pavement recharge beds shall dewater within 72 hours.
(e)
A minimum depth of 24 inches between the intended bottom of
the facility and the seasonal high water table and/or bedrock and/or
groundwater (limiting zones). The minimum required separation between
the limiting zone may be increased at the Township's discretion
if project specific conditions, such as anticipated contaminants,
dictate greater prevention of groundwater contamination.
(f)
All recharge bed bottoms shall be flat (0% slope). Porous pavement
surface slopes shall not exceed 2% and are encouraged to be designed
at 1%. In certain cases, the Township may allow surface slopes up
to 3% if natural grades are left largely undisturbed.
(8)
Extended detention/dual-purpose detention.
(a)
Detention basin BMPs shall be designed in accordance with the
design criteria and specifications in the PA BMP Manual and shall
meet the following the following minimum requirements.
(b)
Grading of detention basins shall be designed to utilize the
natural contours of land whenever possible. When such design is impractical,
the construction of the basin shall utilize slopes as shallow as possible
to blend the structure into the terrain.
1)
Maximum depth of stored water in detention basins shall be five
feet, unless a greater depth is approved by the Board of Supervisors.
2)
Maximum side slopes shall be a four-to-one ratio, horizontal
to vertical. A ten-foot wide access shall be provided for maintenance
of the facility with a maximum slope of 10:1 ratio.
3)
A minimum grade of 2% shall be maintained for all areas in the
basin where sheet flow occurs. A one-percent minimum grade shall be
maintained for channel flow in the basin.
(c)
The top width of the embankment shall be a minimum of 10 feet
for storage volumes greater than 15,000 cubic feet. The top width
of the embankment may be reduced to five feet for maximum storage
volumes under 15,000 cubic feet.
(d)
A cutoff trench shall be provided along the center line of any
dam or earth fill embankments. The trench shall have a bottom width
of not less than four feet, but adequate to allow use of equipment
necessary to obtain proper compaction. Side slopes of cutoff trench
shall be no steeper than 1:1 ratio. The trench shall be filled with
successive thin layers of relatively impervious material, each layer
being thoroughly compacted.
(e)
All basin embankments shall be placed in lifts not to exceed
eight inches in thickness and each lift shall be compacted to a minimum
of 95% of modified proctor density as established by ASTM D-1557.
Prior to proceeding to the next lift, the compaction shall be checked
by a soils engineer employed by the applicant/developer. Compaction
tests shall be run on the leading and trailing edge of the berm along
with the top of the berm. Verification of required compaction shall
be submitted to the Township prior to utilization of any basin for
stormwater management.
(f)
Spillways shall be provided to convey storm runoff around or
under the embankment in a controlled manner to prevent overtopping.
The spillway also must convey the water from the basin to a stable
outlet below without damage to the downstream slopes.
1)
Primary spillway. The riser shall be solidly attached to the
barrel and all connections for riser and pipe barrel shall be watertight.
The barrel and riser shall be placed on a firm foundation. The fill
material around the primary spillway shall be placed in four-inch
lifts and compacted to at least the same density as the adjacent embankment.
If the basin is being used as a temporary sediment control facility
during construction, the riser shall be constructed in accordance
with specifications set forth by PADEP and NRCS in the "Erosion and
Sediment Pollution Control Manual," latest edition.
2)
Emergency spillway. Whenever possible, the emergency spillway
for detention basins shall be constructed on undisturbed ground. Emergency
spillways constructed on undisturbed ground may be constructed of
reinforced vegetated earth. All other spillways shall be constructed
of riprap, concrete checkerblocks, or similar materials approved by
the Township Engineer.
a)
The minimum capacity of all emergency spillways shall be equal
to the peak flow rate from the one-hundred-year design storm.
b)
Emergency spillways shall extend along the upstream and downstream
berm embankment slopes. The upstream edge of the spillway material
shall be a minimum of three feet below the spillway crest elevation.
The downstream slope of the spillway shall extend to the toe of the
berm embankment. The emergency spillway shall not discharge over earthen
fill or easily erodible material.
3)
The minimum freeboard through the emergency spillway shall be
one foot. Freeboard is defined as the difference between the design
flow elevation through the spillway and the elevation of the top of
the settled basin berm. Six inches, minimum, is required between the
one-hundred-year water surface elevation and the emergency spillway
crest.
4)
Antiseep collars shall be installed around the principal spillway
pipe barrel within the normal saturation zone. The collars and their
connections to the pipe shall be watertight. The maximum spacing shall
be approximately 14 times the minimum projection of the collar measured
perpendicular to the pipe. The minimum projection shall be two feet.
5)
All basin outlets which discharge to surface waters shall have
energy dissipating devices designed in accordance with the PADEP "Erosion
and Sediment Pollution Control Manual," latest edition.
6)
Basins shall be protected against erosion by vegetative means
as soon as practical after construction and before runoff is directed
to the facility via storm conveyances. Areas that have eroded during
construction shall be regraded and stabilized prior to final seeding
procedures. Basins shall receive a minimum of eight inches of topsoil,
conditioned as needed, prior to seeding.
7)
Vegetative cover. Basins shall be landscaped in accordance with §
22-523.
(9)
All stormwater control facility designs shall conform to the
applicable standards and specifications of the following governmental
and institutional agencies:
(a)
American Society of Testing and Materials (ASTM).
(c)
Bucks County Conservation District.
(d)
Federal Highway Administration (FHWA).
(e)
National Crushed Stone Association (NCSA).
(f)
National Sand and Gravel Association (NSGA).
(g)
Pennsylvania Department of Environmental Protection (DEP).
(h)
Pennsylvania Department of Transportation (PennDOT).
(i)
U.S. Department of Agriculture, Natural Resources Conservation
Service, Pennsylvania (NRCS).
(10)
If special geological hazards or soil conditions, such as carbonate
derived soils, are identified on the site, the developer's engineer
shall consider the effect of proposed stormwater management measures
on these conditions. In such cases, the Township may require an in-depth
report by a competent soils engineer.
[Ord. 690, 9/10/2009; as amended by Ord. 737, 1/19/2017]
The owner, developer, or subdivider shall install erosion and
sedimentation control measures for any site improvements. The measures
shall be shown on a plan in accordance with present Township ordinances
and Bucks County Conservation District standards. All required permits
shall be obtained from the Bucks County Conservation District prior
to approval by the Township.
A. All erosion and sedimentation control measures shall be regulated in accordance with Chapter
19, Erosion and Sediment Control, of the Code of the Township of Warminster, as well as all rules and regulations established by the Pennsylvania Department of Environmental Protection.
B. No regulated earth disturbance activities within the Township shall
commence until the Township approves an erosion and sedimentation
control plan for construction activities.
C. Evidence of any necessary permit(s) for regulated earth disturbance
activities from the appropriate DEP regional office or County Conservation
District shall be provided to the Township.
D. A copy of the erosion and sedimentation control plan, narrative report,
and any required permits shall be available on the project site at
all times.
E. Additional erosion and sedimentation control designed standards and
criteria shall be applied where infiltration BMPs are proposed.
(1)
Areas proposed for infiltration BMPs shall be protected from
sedimentation and compaction during the construction phase to maintain
maximum infiltration capacity. Barriers such as orange construction
fencing should be used to protect and keep construction traffic away
from the area where infiltration BMPs are proposed. Inlets or pipes
that are installed to these systems should be completely sealed or
protected and monitored until the drainage areas are completely stabilized.
(2)
Infiltration BMPs shall not be constructed nor receive runoff
until the entire contributory drainage area to the infiltration BMP
has achieved final stabilization.
F. Sediment traps per design criteria presented in the PADEP "Erosion
and Sediment Control Program Manual" are recommended to be used in
lieu of sediment basins.
G. Detailed construction schedules shall be included in all erosion
and sediment control plans and stormwater management plans reviewed
by the Bucks County Conservation District.