No application for development shall be approved unless the
Township Engineer has certified to the approving authority in writing
that:
A.
The applicant has provided the Township Engineer with sufficient
information for him to determine whether or not the proposed development
will conform to Township runoff standards, runoff control details
and stormwater detention facility design criteria.
B.
In the judgment of the Township Engineer, the proposed development
will substantially conform to these standards and design criteria
set forth herein.
A.
Retention and detention basins as may be required for surface runoff and drainage control shall be located on-site and within the zoning district permitting that use, subject to the requirements outlined herein. Such basins shall be considered accessory uses and also subject to the conditions of § 170-159 of this chapter.
Where it can be demonstrated, at the time of Planning Board
review, that such on-site basin location within the zoning district
permitting that use is impractical due to engineering feasibility
factors, then the Planning Board may permit such basins to be located
off-tract and/or out of the zoning district, provided that the following
requirements are met:
B.
The location of the basin does not hinder or discourage the appropriate
development and use of the property on which it is located or the
use of adjacent land and buildings.
C.
Permanent access or easement to the basin for maintenance purposes
shall be provided.
D.
Utilization of other nearby off-tract basin facilities is not feasible
or practicable as determined by the Township Engineer.
Basins other than those providing long-term water retention,
such as at a recreational or irrigation lake or basin facility serving
three or more properties, shall be designed to be dewatered with the
side slopes and floor of such basins to be sodded. Where dewatering
is not practical, then areas adjacent to such basins shall contain
protective landscaping (e.g., thorny, decorative shrubs), arranged
so as to restrict access to its edge. Where basins in general are
to be located in parking lots or areas adjacent to pedestrian or vehicular
traffic, dense plantings of shrubs to act as barriers and adequate
low-level lighting for safety precautions shall be required.
A.
No land area in the Township shall be developed so that:
(1)
The maximum rate of stormwater runoff from the area from any
storm up to and including the one-hundred-year-probability storm (which
shall be known as the "design storm") is increased over what occurs
there under existing conditions. The one-hundred-year-probability,
twenty-four-hour, Type II storm shall be as defined by publications
of the Soil Conservation Service, or shall be a one-hundred-year probability
storm as defined by publications of the Department of Environmental
Protection for the size of site in question.
(2)
The drainage of adjacent areas is adversely affected.
(3)
Soil erosion during and after development is increased over
what naturally occurs there.
(4)
Soil absorption and groundwater recharge capacity of the area
is decreased below what occurs under existing conditions.
(5)
The natural drainage pattern of the area is significantly altered.
B.
Provisions should be made for retention of runoff from small storms
long enough for settlement of particulates. Specifically, the stored
runoff from 1 1/4 inches of rainfall occurring in two hours must
allow only 90% to be evacuated from the detention facility during
36 hours, or during 18 hours in the case of dry basins in residential
areas. This requirement for retention may be waived for residential
areas where runoff is passed in sheet flow over 30 feet of lawn or
leaf-mulch area, and the full extent of retention will not be required
where this would require outlets less than three inches in diameter.
In order to duplicate as nearly as possible natural drainage
conditions, regulation and control of stormwater runoff and erosion
for any land area to be developed shall be through on-site water detention
and/or ground absorption systems which include, but are not limited
to, the following:
A.
Detention areas which may be depressions in parking areas, excavated
basins, basins created through use of curbs, stabilized earth berms
or dikes, or any other form of grading which serves to temporarily
impound and store waters.
B.
Rooftop storage, through temporary impoundment and storage of stormwater,
on flat or slightly pitched building rooftops by use of drain outlets
which restrict the stormwater runoff from the roof surface.
C.
Drywells or leaching basins which control stormwater runoff through
ground absorption and temporary storage.
D.
Porous pavement or gravel, which preserves the natural ground absorption
capacity of a site and provides a subsurface reservoir for temporary
storage of stormwater.
E.
Any system of porous media, such as gravel trenches drained by porous
wall or perforated pipe, which temporarily store and dissipate stormwater
through ground absorption.
F.
Any combination of the above mentioned techniques which serve to
limit stormwater runoff from a given site to what presently occurs
there.
G.
Preservation of natural vegetation.
A.
Stormwater detention facilities shall be designed to contain an amount
equal to the increase in volume of runoff which would result from
development of any site. The volume of runoff shall be computed on
the basis of the one-hundred-year-probability storm, as previously
defined. The difference between the runoff from one-hundred-year storm
after development and the runoff from a two-year storm prior to development
shall be known as the "runoff excess."
B.
The runoff shall be computed for each site using accepted, published
runoff coefficients such as found in Urban Hydrology for Small Watershed,
Technical Release No. 55 Engineering Division, Soil Conservation Service,
United States Department of Agriculture, January 1977, and as may
be modified by the Township Engineer. The range of coefficients for
each land use and surface type reflects differences in land slope,
intensity of development, amount of impervious surface and degree
of ground saturation due to antecedent precipitation.
C.
The runoff shall be determined for each site for both existing and
proposed conditions and the difference in the two, or runoff excess,
shall be used to determine the capacity of the stormwater detention
facilities. If any such facility will contain water under normal conditions,
the amount so contained shall not be counted in calculating the capacity
required for the detention of water for the design storm.
D.
In the case of detention facilities utilizing porous media for ground
absorption, such as drywell, porous pavement or the like, the volume
of the porous media above the water table shall be large enough to
contain the total volume of runoff excess within the voids. Ground
absorption systems shall be used only where the infiltration rate
of the receiving soil is acceptable as determined by percolation tests
and soil borings, or as determined by the Township Engineer. Provisions
shall be made to contain overflow on such systems on-site or to surface
drain the overflow in such a way as not to adversely affect any other
property.
E.
If detention facilities utilizing surface impoundment, such as detention
basins or rooftop storage, are used, sufficient volume to fully contain
the total volume of runoff excess shall be provided. The outlets of
such facilities shall discharge in such a way as not to adversely
affect any other property. If rooftop storage is proposed, the weight
of the impounded water on the roof shall be accounted for in the structural
design of the building, and the roof shall be designed to provide
maximum protection against leakage. If berms or dikes are used to
create the impounding area, they shall be adequately stabilized and
the slopes protected with vegetative cover, paving or rip-rap to protect
against failure or breathing.
F.
If a combination of different stormwater detention techniques is
used, combined volume of the systems shall be large enough to fully
contain the total volume of runoff excess.
G.
Stormwater detention facilities shall be constantly maintained by
the owner to ensure continual functioning of the systems at design
capacity and to prevent the health hazards associated with debris
buildup and stagnant water. In no case shall water be allowed to remain
in any facility long enough to constitute a mosquito-breeding, disease
or any other type of health problem, unless approved as a multifunction
facility to include water, such as a pond. If the land or stormwater
detention facility or facilities are proposed to be dedicated to the
Township and said dedication is accepted by the Township, the procedures
for the construction, dedication and acceptance and maintenance of
such facilities set forth herein, including but not limited to performance
and maintenance bonds, inspections, etc., shall govern.
H.
Detention and sediment and erosion control facilities shall be designed
in conformance with the Standards for Soil Erosion and Sediment Control
in New Jersey of the New Jersey State Soil Conservation Committee,
as approved by the Township Engineer or the Salem County Soil Conservation
District under agreement, except where the Township Engineer has determined
that conditions peculiar to a certain site warrant exception.
I.
Sediment and erosion control measures shall be installed prior to
any other site development, shall apply to all aspects of the proposed
development, and shall be in operation during all stages of development.
Increased runoff and sediment, resulting from modified soil and surface
conditions caused by the proposed development, shall be minimized
and where possible, retained on-site.
J.
For each detention basin, an emergency spillway shall be provided which will accommodate flows from storms in excess of the design storm. Outlets shall be designed so as to reduce the maximum rate of outflow from the design storm after development to a rate not in excess of that which would have occurred prior to development as required by § 170-160A(1) above, both for the peak instantaneous flow and the peak hourly flow, and to provide for retention of runoff from small storms as required by § 170-160B above. Outlets shall effect the maximum practicable degree of detention of runoff from storms of intermediate size. If an affirmative showing is made that storage in an amount less than the runoff excess will satisfy requirements of § 170-160 for both the design storm and for storms respectively 1/4, 1/2, 3/4 of that amount of rainfall, then that reduced amount of storage will be sufficient to satisfy the requirements of this chapter. In making this determination, all lands in the site shall be assumed, prior to development, to be in good condition (if the lands are pastures, lawns or parks) with good cover if the lands are woods, or with conservation treatment (if the land is cultivated) regardless of conditions existing at the time of computation.
K.
Outlet waters from the site or the detention facility shall be discharged
at such locations and velocities as not to cause additional erosion,
or to create additional channels below the development.
Prior to the granting of any site development approval, the
applicant may be required to enter into an agreement with the Township,
in form satisfactory to the Township Attorney, requiring the installation
and maintenance by the applicant and the applicant's successors in
interest, of such improvements on or to the site or imposing such
limitations upon the development thereof, as are deemed necessary
by the Planning Board for implementing the standards and criteria
set forth in this chapter, providing that the municipality may cause
such improvements to be installed or maintained and developments in
violation of such limitations to be corrected at the expense of the
applicant or the applicant's successors in interest, if they shall
fail to do so, and granting to the municipality such rights and easements
as shall be reasonably required for access by the municipality to
such improvements and developments for such purposes. The agreement
shall also provide for inspection annually and after each major flood
by the Township Engineer and by another qualified engineer acceptable
to the Township Engineer, at the expense of the applicant and the
applicant's successors in interest, and for the undertaking by the
applicant and successors of such corrective measures as are shown
by such inspection to be required for the proper functioning of the
facilities.
Such improvements and developments on the site, during and upon
completion of their construction, shall be subject to inspection and
approval by the Township Engineer, who shall be notified by the applicant
at least 24 hours prior to the start of construction. No underground
installation shall be covered until inspected and approved. Approval
or reasons for withholding approval shall be given promptly, and in
any event within 45 days after inspection. If work proceeds without
such approval or not in compliance therewith, the Township Engineer,
in addition to any other remedies available to the municipality, may
issue an order requiring immediate cessation of the affected work
and prohibiting resumption thereof until approval is obtained or noncompliance
corrected.
Prior to the acceptance by the Township of any stormwater facilities,
the developer's engineer shall certify that said facilities were constructed
in accordance with the approved plan.
A.
The provision of separate detention facilities for a number of single
sites is generally more expensive and more difficult to maintain than
provision of joint facilities each serving a number of sites. In such
cases, a properly planned staged plan and program of detention facilities
may be approved by special ordinance; and, in such a case, compliance
with detention requirements for areas first developed may be postponed
at early stages while preliminary work is being undertaken, sites
acquired and construction funds accumulated.
B.
In such a case, an initial money contribution will be levied upon
each developer, proportionate to the runoff excess of his proposed
development. Such funds will be held in escrow for use in carrying
out the joint plan. Construction and maintenance responsibility for
the joint facilities will be determined and specified as part of the
plan.
