A preapplication conference shall be held with the Township
Superintendent and/or his designee prior to the submittal of a stormwater
management plan. The purpose of the preapplication conference is to
provide information and guidance that will assist the proprietor in
preparing the required plan.
The Township Board shall establish fees and escrow requirements
by resolution. Fees and escrow account payments shall be sufficient
to cover administrative and technical review costs anticipated to
be incurred by the Township including the costs of on-site inspections.
All developments and earth changes subject to review under the
requirements of this chapter shall be designed, constructed, and maintained
to prevent flooding and protect water quality. The particular facilities
and measures required on site shall reflect the natural features,
wetlands, and watercourses on the site; the potential for on-site
and off-site flooding, water pollution, and erosion; and the size
of the site.
A. General standards for on-site and off-site stormwater management.
(1) Stormwater management conveyance, storage and infiltration measures
and facilities shall be designed to prevent flood hazards and water
pollution related to stormwater runoff and soil erosion from the proposed
development.
(2) Stormwater from upstream and off-site locations shall be conveyed
around or through the site, or stored on site.
(3) A primary drainage system which manages runoff from storms up to
a ten-year-frequency storm event shall be provided.
(4) A secondary drainage system, such as an overland flow routing system
to manage runoff from storms up to a one-hundred-year-frequency storm
event shall be provided (secondary drainage system).
(5) Every detention basin shall control the release of stormwater for
the ten-year- and one-hundred-year-frequency storm events. For the
ten-year-frequency storm event, the peak rate of discharge shall not
exceed 0.2 cubic foot per second per acre. For the one-hundred-year-frequency
storm event, the runoff rate shall not exceed the predevelopment rate.
(6) Unless otherwise approved, stormwater runoff shall be conveyed through
swales and vegetated buffer strips so as to decrease runoff velocity,
allow for natural infiltration, allow suspended sediment particles
to settle, and to remove pollutants.
(7) Alterations to natural drainage patterns shall not create flooding
or water pollution for adjacent or downstream property owners.
(8) Watercourses shall not be dredged, cleared of vegetation, deepened,
widened, straightened, stabilized or otherwise altered without applicable
permits or approvals from the Township Board and the State Department
of Environmental Quality. If the watercourse is a designated county
drain, approval from the County Water Resources Commissioner shall
also be obtained.
(9) No modifications of major watercourses shall be permitted when the
primary purpose is to increase the flow capacity of the watercourse.
(10)
Discharge of runoff from any site which may contain oil, grease,
toxic chemicals, or other polluting materials is prohibited unless
measures to reduce and trap pollutants meet the requirements of the
State Department of Environmental Quality and the Township, based
upon professionally accepted principles.
(11)
Drainage systems shall be designed to protect public health
and safety and to be visually attractive.
B. Soil erosion control.
(1) Cutting, filling and grading shall be minimized and the natural topography
of the site shall be preserved to the maximum feasible extent, except
where specific findings demonstrate that major alterations will still
meet the purposes and requirements of this chapter.
(2) All development and other earth changes shall be designed, constructed
and completed in such a manner that the exposed area of any disturbed
land is limited to the shortest possible period of time.
(3) Soil erosion control measures shall be installed between the disturbed
area and any watercourses (including rivers, streams, creeks, lakes,
ponds and other watercourses), wetlands, or roadways on or near the
site.
(4) Sediment resulting from accelerated soil erosion shall be removed
from runoff water before it leaves the site of the development or
earth change.
(5) Temporary and permanent soil erosion control measures designed and
constructed for the conveyance of water around, through or away from
the development or earth change area shall be designed to limit the
water flow to a nonerosive velocity.
(6) Temporary soil erosion control measures shall be removed after permanent
soil erosion control measures have been implemented. All developments
and earth change areas shall be stabilized with permanent soil erosion
control measures.
(7) If lakes, ponds, rivers, creeks, streams or other watercourses and
wetlands are located on or near the site, erosion control measures
which trap sediment shall be provided. Straw bale berms may be used
as temporary stormwater diversion structures but will not be considered
sufficient by themselves for trapping sediment on site. The use of
sediment basins, sediment traps, filter fabric, and rock filters in
lieu of straw bale berms shall be strongly encouraged. Other measures
may be required if reasonably determined to be necessary to protect
a watercourse or wetland.
(8) When it is not possible to permanently stabilize a disturbed area
after an earth change has been completed or where significant earth
change activity ceases, temporary soil erosion control measures shall
be implemented within 30 calendar days.
(9) Permanent soil erosion control measures for all slopes, channels,
ditches, or any disturbed land area shall be completed within 15 calendar
days after final grading or the final earth change has been completed.
All temporary soil erosion control measures shall be maintained until
permanent soil erosion control measures are implemented.
(10)
Vegetated buffer strips shall be created or retained along the
edges of all lakes, ponds, creeks, streams, other watercourses, and
wetlands, when reasonably determined to be necessary to protect the
watercourse.
C. Stormwater storage and infiltration facilities.
(1) Stormwater storage and/or infiltration facilities which protect water
quality and minimize flooding shall be required for all developments.
Storage facilities may include, but are not limited to, detention
basins, retention basins, infiltration trenches, swales with check
dams, and other facilities.
(2) All detention basins shall be designed to maximize the ability of the basin to hold and trap sediment. The types of basins listed in this Subsection
C(2) meet Township requirements. The following types of basins are listed in order of preference, with the most desirable listed first:
(a)
Infiltration facilities, provided that soils and groundwater
conditions are suitable.
(b)
Detention basins with a fixed minimum water elevation between
runoff event (wet basins). Wet basins which serve to trap soil particles
on site are preferable to dry basins.
(c)
Detention basins which hold stormwater from the one-year storm
event for more than 24 hours before completely draining to become
a dry basin (extended detention). Dry basins without extended detention
shall not be permitted.
(3) Detention and retention basins shall be designed to hold runoff from
a one-hundred-year-frequency storm event. Basins shall be permanently
stabilized to minimize erosion.
(4) Retention and detention basins shall have an overflow system. If
the overflow system cannot discharge to a creek, lake or wetland without
causing flooding on adjacent or downstream properties, then the basin
shall be designed to hold stormwater runoff from two back-to-back
one-hundred-year-frequency storm events.
(5) Unless a variation is approved by the Township Board (See Article
IV of this chapter.), detention and retention basins with banks sloping more than one on five (vertical to horizontal) shall not be permitted.
(6) Detention basins and associated berms and landscaping shall be designed
to protect public safety and to be visually attractive.
(7) Constructed detention basins shall not be a part of a platted subdivision
lot, but shall be provided in platted outlots or open space areas.
D. Discharge of stormwater runoff to wetlands.
(1) Stormwater runoff discharged to wetlands must be diffused to nonerosive
velocities before it reaches the wetland.
(2) Wetlands may be used for stormwater detention if the following conditions
are met:
(a)
The wetland storage or detention area is set back at least 100
feet from the edge of any lake or stream.
(b)
The wetland does not have significant wildlife habitat or ecological
values which would likely be impaired or destroyed.
(c)
The wetland has sufficient holding capacity for stormwater,
based upon calculations prepared by the proprietor and reviewed and
approved by the Township Engineer.
(d)
Adequate on-site soil erosion control is provided to protect
the natural functioning of the wetland.
(3) During the construction phase of development, adequate erosion control
and protection of wetlands shall be provided as required, including
such things as:
(a)
One or more sediment traps or soil settling basins located in
upland locations; and/or
(b)
Open-water sediment traps within or adjacent to wetlands, provided
that the proposal meets the wetland protection requirements of the
State Department of Environmental Quality and the Township for wetlands
alteration.
(4) If off-site wetlands are used for stormwater management, an easement must be ensured in accordance with the requirements of Article
VI of this chapter.