A.
General design guidelines.
(1)
The applicant should consider the effect on the proposed stormwater
management techniques of any special soils conditions or geological
hazards which may exist on the development site. In the event such
conditions are identified on the development site, the Township may
require in-depth studies by a competent geotechnical engineer.
(2)
Stormwater shall not be transferred from one watershed to another,
unless:
(3)
Consideration shall be given to the relationship of the subject property
to the drainage pattern of the watershed. A concentrated discharge
of stormwater to an adjacent property shall be within an existing
watercourse or confined in an easement or returned to a predevelopment-flow-type
condition.
(4)
Stormwater BMPs and recharge facilities are encouraged (e.g., rooftop
storage, cisterns, recreation area ponding, diversion structures,
porous pavements, holding tanks, infiltration systems, in-line storage
in storm sewers, and grading patterns). They shall be located, designed,
and constructed in accordance with the latest technical guidance published
by PADEP, provided they are accompanied by detailed engineering plans
and performance capabilities and supporting site-specific soils, geology,
runoff and groundwater and infiltration rate data to verify proposed
designs. Additional guidance from other sources may be accepted at
the discretion of the Municipal Engineer. (A preapplication meeting
is suggested.)
(5)
All existing and natural watercourses, channels, drainage systems
and areas of surface water concentration shall be maintained in their
existing condition unless an alteration is approved by the appropriate
regulatory agency.
(6)
The design of all stormwater management facilities shall incorporate
sound engineering principles and practices. Peters Township shall
reserve the right to disapprove any design that would result in the
continuation or exacerbation of a documented adverse hydrologic or
hydraulic condition within the watershed, as identified in the plan.
(7)
The design and construction of multiple-use stormwater detention
facilities are strongly encouraged. In addition to stormwater management,
facilities should, where appropriate, allow for recreational uses,
including ball fields, play areas, picnic grounds, etc. Consultation
with Peters Township and prior approval are required before design.
Provision for permanent wet ponds with stormwater management capabilities
may also be appropriate.
(a)
Multiple-use basins should be constructed so that potentially
dangerous conditions are not created.
(b)
Water quality basins or recharge basins that are designed for
a slow release of water or other extended detention ponds are not
permitted for recreational uses, unless the ponded areas are clearly
separated and secure.
B.
Stormwater management facility design considerations. All stormwater
management facilities shall meet the following design requirements:
(1)
Shared storage facilities, which provide detention of runoff for
more than one development site, are encouraged within a single subarea.
Such facilities shall meet the design criteria contained in this section.
In addition, runoff from the development sites involved shall be conveyed
to the facility in a manner so as to avoid adverse impacts, such as
flooding or erosion, to channels and properties located between the
development site and the shared storage facilities.
(2)
No outlet structure from a stormwater management facility, or swale,
shall discharge directly onto a municipal or state roadway.
(3)
The minimum horizontal distance between any structure and any stormwater
facility shall be 25 feet. The lowest floor elevation of any structure
constructed immediately adjacent to a detention basin or other stormwater
facility shall be a minimum of two feet above the one-hundred-year
water surface elevation.
(4)
Stormwater management facility bottom (or surface of permanent pool)
elevations must be greater than adjacent floodplain elevations (FEMA,
HEC-RAS, or other acceptable analysis). If no floodplain is defined,
bottom elevations must be greater than existing ground elevations
50 feet from top of stream bank in the facilities' vicinity.
(5)
Basin outflow culverts discharging into floodplains must account
for tailwater. Tailwater corresponding to the one-hundred-year floodplain
elevation must be used for all twenty-four-hour design storms, or
the applicant may elect to determine flood elevations of the adjacent
watercourse for each twenty-four-hour design storm. The floodplain
is assumed to be 50 feet from top of stream bank in areas where a
floodplain is not designated or no other evidence is provided.
(6)
The invert of all stormwater management facilities and underground
infiltration/storage facilities shall be located a minimum of two
feet above the seasonal high groundwater table. The invert of stormwater
facilities may be lowered if adequate subsurface drainage is provided.
(7)
To the extent practical, the side slopes and basin shape shall be
amenable to and harmonize with the natural topography.
(8)
Interior slopes of the basin shall not exceed 3:1.
(9)
Unless specifically designed as a volume control facility, all stormwater
management facilities shall have a minimum slope of 1% extending radially
out from the principal outlet structure. Facilities designed as water
quality/infiltration BMPs may have a bottom slope of zero.
(10)
Impervious low-flow channels are not permitted within stormwater
management facilities.
(11)
Unless specifically designed as a volume control or water quality
facility, all stormwater management facilities must empty over a period
of time not less than 24 hours and not more than 72 hours from the
end of the facility's inflow hydrograph. Infiltration tests performed
at the facility locations and proposed basin bottom depths, in accordance
with the BMP Manual, must support time-to-empty calculations if infiltration
is a factor.
(12)
Energy dissipaters and/or level spreaders shall be installed
at points where pipes or drainageways discharge to or from basins.
Discharges to drainage swales shall be dissipated, or piped, to an
acceptable point.
(13)
A safety fence may be required, at the discretion of Peters
Township, for any stormwater management facility. The fence shall
be a minimum of four feet high, and of a material acceptable to Peters
Township. A gate with a minimum opening of 10 feet shall be provided
for maintenance access.
(14)
Principal outlet structures. The primary outlet structure shall
be designed to pass all twenty-four-hour design storms (up to and
including the one-hundred-year event) without discharging through
the emergency spillway. All principal outlet structures shall:
(a)
Be constructed of reinforced concrete or an alternative material
approved by the Municipal Engineer. When approved for use, all metal
risers shall:
[1]
Be suitably coated to prevent corrosion.
[2]
Have a concrete base attached with a watertight connection.
The base shall be sufficient weight to prevent flotation of the riser.
[3]
Provide a trash rack or similar appurtenance to prevent debris
from entering the riser.
[4]
Provide an anti-vortex device, consisting of a thin vertical
plate normal to the basin berm.
(b)
Provide trash racks to prevent clogging of primary outflow structure
stages for all orifices equivalent to 12 inches or smaller in diameter.
(c)
Provide outlet aprons which shall extend to the toe of the basin
slope at a minimum.
(15)
Emergency spillways. Any stormwater management facility designed
to store runoff shall provide an emergency spillway designed to convey
the one-hundred-year post-development peak rate flow with a blocked
primary outlet structure. The emergency spillway shall be designed
per the following requirements:
(a)
The top of embankment elevation shall provide a minimum one
foot of freeboard above the maximum water surface elevation. This
is to be calculated when the spillway functions for the one-hundred-year
post-development inflow, with a blocked outlet structure.
(b)
Avoid locating on fill areas, whenever possible.
(c)
The spillway shall be armored to prevent erosion during the
one-hundred-year post-development flow, with a blocked primary outlet
structure.
[1]
Synthetic liners which harmonize and blend into the surrounding
landscape (such as geogrid) are encouraged for aesthetic purposes.
Calculations sufficient to support proposed armor must be provided.
An earthen plug or concrete cutoff wall must be used to accurately
control the spillway invert if riprap is the proposed armoring material.
Emergency spillway armor must extend up the sides of the spillway,
and continue at full width to a minimum of 10 feet past the toe of
slope. Peters Township reserved the right to require an armor other
than riprap based on the visual impact to the surrounding properties.
(d)
The Municipal Engineer may require the use of additional protection
when slopes exceed 4:1 and spillway velocities might exceed NRCS standards
for the particular soils involved.
(e)
Any underground stormwater management facility (pipe storage
systems) must have a method to bypass flows higher than the required
design (up to a one-hundred-year post-development inflow) without
structural failure, or causing downstream harm or safety risks.
(16)
Stormwater management basins. Design of stormwater management
facilities having three feet or more of water depth (measured vertically
from the lowest elevation in the facility to the crest of the emergency
spillway) shall meet the following additional requirements:
(a)
The maximum water depth within any stormwater management facility
shall be no greater than eight feet when functioning through the primary
outlet structure.
(b)
The top of embankment width shall be at least 10 feet.
(c)
A ten-foot-wide access to the basin bottom must be provided
with a maximum longitudinal slope of 10%.
(d)
Berms shall be constructed using soils that conform to the unified
soil classification of CH, MH, CL or ML. The embankments will be constructed
in a maximum of six-inch lifts. The lifts will each be compacted to
a density of 98% of a standard proctor analysis as per each layer
of compacted fill shall be tested to determine its density analysis
per ASTM 698. Each layer of compacted fill shall be tested to determine
its density per ASTM 2922 or ASTM 3017.
(e)
A cutoff and key trench of impervious material shall be provided
under all embankments four feet or greater in height. The cutoff trench
shall run the entire length of the embankment and tie into undisturbed
natural ground.
(f)
Anti-seep collars, or a PADEP-approved alternative, must be
provided on all outflow culverts in accordance with the methodology
contained in the latest edition of the PADEP E&S Manual. An increase
in seepage length of 15% must be used in accordance with the requirements
for permanent anti-seep collars.
(17)
Construction of stormwater management facilities.
(a)
Basins used for rate control only shall be installed prior to
or concurrent with any earthmoving or land disturbances which they
will serve. The phasing of their construction shall be noted in the
narrative and on the plan.
(b)
Basins that include water quality or recharge components shall
have those components installed in such a manner as to not disturb
or diminish their effectiveness.
(c)
Compaction test reports shall be kept on file at the site with
copies being forwarded to the Municipal Engineer.
(d)
Temporary and permanent grasses or stabilization measures shall
be established on the sides and base of all earthen basins within
15 days of construction.
(18)
Exceptions to these requirements may be made at the discretion
of Peters Township for BMPs that retain or detain water, but are of
a much smaller scale than traditional stormwater management facilities.
C.
Stormwater-carrying facilities.
(1)
All storm sewer pipes, grass waterways, open channels, swales and
other stormwater-carrying facilities that service drainage areas within
the site must be able to convey post-development runoff from the twenty-five-year
twenty-four-hour design storm.
(2)
Stormwater management facilities that convey off-site water through
the site shall be designed to convey the twenty-five-year storm event
(or larger events, as determined by the Municipal Engineer).
(3)
All developments shall include provisions that allow for the overland
conveyance and flow of the post-development one-hundred-year storm
event without damage to public or private property.
(4)
Storm sewers.
(a)
Storm sewers must be able to convey post-development runoff
without surcharging inlets for the twenty-five-year storm event.
(b)
When connecting to an existing storm sewer system, the applicant
must demonstrate that the proposed system will not exacerbate any
existing stormwater problems and that adequate downstream capacity
exists.
(c)
A minimum pipe size of 15 inches in diameter shall be used in
all roadway systems (public or private) proposed for construction
in Peters Township. Pipes shall be designed to provide a minimum velocity
of 2 1/2 feet per second when flowing full, but, in all cases,
the slope shall be no less than 0.5%. Arch pipe of equivalent cross-sectional
area may be substituted in lieu of circular pipe where cover or utility
conflict conditions exist.
(d)
All storm sewer pipes shall be laid to a minimum depth of one
foot from subgrade to the crown of pipe.
(e)
In curbed roadway sections, the maximum encroachment of water
on the roadway pavement shall not exceed half of a through travel
lane or one inch less than the depth of curb during the ten-year design
storm of five-minute duration. Gutter depth shall be verified by inlet
capture/capacity calculations that account for road slope and opening
area.
(f)
For inlets containing a change in pipe size, the elevation for
the crown of the pipes shall be the same or the smaller pipe's
crown shall be at a higher elevation.
(g)
All inlets shall provide a minimum two-inch drop between the
lowest inlet pipe invert elevation and the outlet pipe invert elevation.
(h)
At all roadway low points, swales and easements shall be provided
behind the curb or swale and through adjacent properties to channelize
and direct any overflow of stormwater runoff away from dwellings and
structures.
(i)
Inlets must be sized to accept the specified pipe sizes without
knocking out any of the inlet corners. All pipes entering or exiting
inlets shall be cut flush with the inside wall of the inlet. A note
to this effect shall be added to the SWM site plan or inlet details
therein.
(j)
Inlets shall have weep holes covered with geotextile fabric
placed at appropriate elevations to completely drain the subgrade
prior to placing the base and surface course on roadways.
(k)
Inlets, junction boxes, or manholes greater than five feet in
depth shall be equipped with ladder rungs and shall be detailed on
the SWM site plan.
(l)
Inlets shall not have a sump condition in the bottom (unless
designed as a water quality BMP). Pipe shall be flush with the bottom
of the box or concrete channels shall be poured.
(m)
Accessible drainage structures shall be located on continuous
storm sewer system at all vertical dislocations, at all locations
where a transition in storm sewer pipe sizing is required, at all
vertical and horizontal angle points exceeding 5°, and at all
points of convergence of two or more storm sewer pipes.
(n)
All storm drainage piping shall be provided with either reinforced
concrete headwalls or end sections compatible with the pipe size involved
at its entrance and discharge.
(o)
Outlet protection and energy dissipaters shall be provided at
all surface discharge points in order to minimize erosion consistent
with the E&S Manual.
[1]
Flow velocities and volumes from any storm sewer shall not result
in a degradation of the receiving channel.
(p)
Stormwater roof drains and pipes shall not be connected to storm
sewers or discharge onto impervious areas without approval by the
Municipal Engineer.
(q)
Collection/conveyance facilities should not be installed parallel
and close to the top or bottom of a major embankment to avoid the
possibility of failing or causing the embankment to fail.
(r)
Where practical, storm sewers shall be designed to traverse
under seeded and planted areas. If constructed within 10 feet of road
paving, walks, or other surfaced areas, drains shall have a narrow
trench and maximum compaction of backfill to prevent settlement of
the superimposed surface or development.
(s)
Storm sewers shall be installed preferably after excavating
and filling in the area to be traversed is completed, unless the drain
is installed in the original ground with a minimum of three feet cover
and/or adequate protection during the fill construction.
(u)
Drainpipe, headwalls, endwalls, trenching, bedding and backfilling
requirements shall conform to the requirements of the Township and/or
applicable requirements of the Pennsylvania Department of Highways
Specifications, current Form 408.
(v)
All corrugated metal pipe shall be polymer coated, or aluminized
with bonding and paved inverts where prone to erode. All pipe within
the Township road right-of-way and all road crossing pipes or piping
between inlets shall be Class III reinforced concrete pipe, N12 ADS
smooth flow pipe or approved equal with a minimum diameter of 15 inches.
When the plastic storm sewer pipe is used, magnetic tape shall be
installed over the top of the storm sewer with a minimum of three
feet of cover over the top of the pipe.
(w)
Manholes shall be designed so that the top shall be at finished
grade and sloped to conform to slope of finished grade. Top castings
of structures located in roads or parking areas shall be machined
or installed to preclude "rattling."
(5)
Swale conveyance facilities.
(a)
Swales must be able to convey post-development runoff from a
twenty-five-year twenty-four-hour design storm with six inches of
freeboard to top of the swale.
(b)
Swales shall have side slopes no steeper than 2:1.
(c)
All swales shall be designed, labeled on the SWM site plan,
and details provided to adequately construct and maintain the design
dimension of the swales.
(d)
Swales shall be designed for stability using velocity or shear
criteria. Velocity criteria may be used for channels with less than
ten-percent slope. Shear criteria may be used for all swales. Documentation
must be provided to support velocity and/or shear limitations used
in calculations.
(f)
Manning's "n" values used for swale capacity design must
reflect the permanent condition.
A.
All calculations shall be consistent with the guidelines set forth
in the BMP Manual, as amended herein.
B.
Stormwater runoff from all development sites shall be calculated
using either the Rational Method or the NRCS Rainfall-Runoff Methodology.
Methods shall be selected by the design professional based on the
individual limitations and suitability of each method for a particular
site.
C.
Rainfall values.
(1)
Rational Method. The Pennsylvania Department of Transportation Drainage
Manual, Intensity-Duration-Frequency Curves, Publication 584, Chapter
7A, latest edition, shall be used in conjunction with the appropriate
time of concentration and return period.
(2)
NRCS Rainfall-Runoff Method. The Soil Conservation Service Type II,
twenty-four-hour rainfall distribution shall be used in conjunction
with rainfall depths from NOAA Atlas 14 or be consistent with the
following table:
|
Return Interval
(year)
|
24-Hour Rainfall Total
(inches)
| |
|---|---|---|
|
1
|
1.99
| |
|
2
|
2.38
| |
|
10
|
3.35
| |
|
25
|
3.96
| |
|
50
|
4.46
| |
|
100
|
4.99
|
D.
Runoff volume.
(1)
Rational Method. Not to be used to calculate runoff volume.
(2)
NRCS Rainfall-Runoff Method. This method shall be used to estimate
the change in volume due to regulated activities. 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.
E.
Peak flow rates.
(1)
Rational Method. This method may be used for design of conveyance
facilities only. Extreme caution should be used by the design professional
if the watershed has more than one main drainage channel, if the watershed
is divided so that hydrologic properties are significantly different
in one versus the other, if the time of concentration exceeds 60 minutes,
or if stormwater runoff volume is an important factor. The combination
of Rational Method hydrographs based on timing shall be prohibited.
(2)
NRCS Rainfall-Runoff Method.
(a)
This method is recommended for design of stormwater management
facilities and where stormwater runoff volume must be taken into consideration.
The following provides guidance on the model applicability:
(b)
The NRCS Antecedent Runoff Condition II (ARC II, previously
AMC II) must be used for all simulations. The use of continuous simulation
models that vary the ARC are not permitted for stormwater management
purposes.
(3)
For comparison of peak flow rates, flows shall be rounded to 1/10
of a cubic foot per second (cfs).
F.
Runoff coefficients.
(1)
Rational Method. Use Table C-1 (Appendix C).[1]
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
(2)
NRCS Rainfall-Runoff Method. Use Table C-2 (Appendix C).[2] Curve numbers (CN) should be rounded to tenths for use
in hydrologic models as they are a design tool with statistical variability.
For large sites, CNs should realistically be rounded to the nearest
whole number.
[2]
Editor's Note: Said appendix is included as an attachment to this chapter.
(3)
For the purposes of predevelopment peak flow rate and volume determination,
existing nonforested pervious areas conditions shall be considered
as meadow (good condition).
(4)
For the purposes of predevelopment peak flow rate and volume determination,
20% of existing impervious area, when present, shall be considered
meadow (good condition).
G.
Twenty-four-hour design storm.
(1)
All stormwater management facilities shall be verified by routing
the proposed one-year, two-year, ten-, twenty-five-, fifty-, and one-hundred-year
hydrographs through the facility using the Storage Indication Method
or Modified Puls Method. The twenty-four-hour design storm hydrograph
shall be computed using a calculation method that produces a full
hydrograph.
(2)
The stormwater management and drainage system shall be designed to
safely convey the post-development one-hundred-year storm event to
stormwater detention facilities, for the purpose of meeting peak rate
control.
(3)
All structures (culvert or bridges) proposed to convey runoff under
a municipal road shall be designed to pass the fifty-year design storm
with a minimum one foot of freeboard measured below the lowest point
along the top of the roadway.
H.
Time of concentration.
(1)
The time of concentration is to represent the average condition that
best reflects the hydrologic response of the area. The following time
of concentration (Tc) computational methodologies
shall be used unless another method is preapproved by the Municipal
Engineer:
(a)
Predevelopment. NRCS's Lag Equation:
|
Time of Concentration = Tc = [(Tlag/0.6) * 60] (minutes)
|
 |
|
Where:
| ||||
|
Tlag
|
=
|
Lag time (hours)
| ||
|
L
|
=
|
Hydraulic length of watershed (feet)
| ||
|
Y
|
=
|
Average overland slope of watershed (percent)
| ||
|
S
|
=
|
Maximum retention in watershed as defined by: S = [(1000/CN)
- 10]
| ||
|
CN
|
=
|
NRCS Curve Number for watershed
| ||
(b)
Post-development; commercial, industrial, or other areas with
large impervious areas (>20% impervious area) - NRCS Segmental Method.
The length of sheet flow shall be limited to 100 feet. Tc for channel and pipe flow shall be computed using Manning's
Equation.
(c)
Post-development; residential, cluster, or other low-impact
designs less than or equal to 20% impervious area - NRCS Lag Equation
or NRCS Segmental Method.
(2)
Additionally, the following provisions shall apply to calculations
for time of concentration:
(a)
The post-development Tc shall never be
greater that the predevelopment Tc for any
watershed or subwatershed. This includes when the designer has specifically
used swales to reduce flow velocities. In the event that the designer
believes that the post-development Tc is greater,
it will still be set by default equal to the predevelopment Tc for modeling purposes.
(b)
The minimum Tc for any watershed shall
be five minutes.
(c)
The designer may choose to assume a five-minute Tc for any post-development watershed or subwatershed
without providing any computations.
(d)
The designer must provide computations for all predevelopment
Tc paths. A five-minute Tc cannot be assumed for predevelopment.
(e)
Undetained fringe areas (areas that are not tributary to a stormwater
facility but where a reasonable effort has been made to convey runoff
from all new impervious coverage to best management practices) may
be assumed to represent the predevelopment conditions for purpose
of Tc calculation.
I.
Drainage areas tributary to sinkholes or closed depressions in areas
underlain by limestone or carbonate geologic features shall be excluded
from the modeled point of analysis defining predevelopment flows.
If left undisturbed during construction activities, areas draining
to closed depressions may also be used to reduce peak runoff rates
in the post-development analysis. New, additional contributing runoff
should not be directed to existing sinkholes or closed depressions.
J.
Where uniform flow is anticipated, the Manning's Equation shall
be used for hydraulic computations and to determine the capacity of
open channels, pipes, and storm sewers. The Manning's Equation
should not be used for analysis of pipes under pressure flow or for
analysis of culverts. Manning's "n" values shall be obtained
from PennDOT's Drainage Manual, Publication 584. Inlet control
shall be checked at all inlet boxes to ensure the headwater depth
during the ten-year design event is contained below the top of grate
for each inlet box.
K.
Peters Township may approve the use of any generally accepted full
hydrograph approximation technique that shall use a total runoff volume
that is consistent with the volume from a method that produces a full
hydrograph.
L.
Peters Township has the authority to require that computed existing
runoff rates be reconciled with field observations, conditions and
site history. If the designer can substantiate, through actual physical
calibration, that more appropriate runoff and time of concentration
values should be utilized at a particular site, then appropriate variations
may be made upon review and recommendation of Peters Township.
Landscaping should be provided for all proposed stormwater detention/retention areas located within the Township in an effort to mitigate any incompatibility or aesthetic issues they may cause. The required landscaping in this section shall not be counted towards the landscaping requirements of any other section. Refer to Chapter 440, Zoning, and Chapter 385, Subdivision and Land Development, of the Peters Township Code of Ordinances, for additional requirements.
A.
Two different planting schemes have been developed to address different
site environments and surroundings. Developers are encouraged to review
proposed stormwater facilities with the Peter's Township Planning
Department to determine which planting scenario is best for their
proposed improvements.
(1)
Open/developed area scenario. This design should be used for areas
where a more groomed and manicured appearance is desired such as within
an office park, retail development or adjacent to a housing development.
(a)
Required trees. One shade tree per 30 linear feet of pond circumference
shall be planted on the outside perimeter of the stormwater pond.
Trees shall be randomly placed up and down the bank and may be grouped.
A variety of evergreen and deciduous trees shall be used which shall
come from the "Recommended Plant List for Peters Township," or as
approved by the Township. One third of the proposed trees shall be
evergreen, and 2/3 of the proposed trees shall be deciduous. Evergreen
trees shall be a minimum of six feet in height, and deciduous trees
shall be a minimum of two inches' caliper. In those circumstances
outside of the developer's control that make it impractical to
fully meet this requirement, it may be modified by the Township.
(b)
Required seeding. Ernst Seeding Mix No. 126 Retention Basin
Floor Seeding, or approved equal, shall be planted on the floor and
on the inside banks of the proposed detention pond.
(2)
Naturalized/wooded area scenario. This design should be used for
areas where a more naturalized look is desired such as at the edge
of the woods.
(a)
Required trees. One shade tree per 30 linear feet of pond circumference
shall be planted on the outside perimeter of the stormwater pond.
Trees shall be randomly placed up and down the bank and may be grouped.
A variety of evergreen and deciduous trees shall be used which shall
come from the "Recommended Plant List for Peters Township," or as
approved by the Township. One third of the proposed trees shall be
evergreen, and 2/3 of the proposed trees shall be deciduous. Evergreen
trees shall be a minimum of six feet in height and deciduous trees
shall be a minimum of two inches' caliper. In this particular scenario,
existing trees to remain of greater or equal caliper may be substituted
for the required trees upon approval by the Township's landscape
architect. Trees and root systems must be properly protected during
construction activities with no construction activity occurring within
the dripline of the trees. In those circumstances outside of the developer's
control that make it impractical to fully meet this requirement, it
may be modified by the Township.
(b)
Required seeding. Ernst Seeding Mix No. 180 Rain Garden Mix,
or approved equal, shall be planted on the floor and on the inside
banks of the proposed detention pond.
