[Amended 12-28-2000 by Ord. No. 34-2000]
In accordance with N.J.A.C. 5:21-7 and the following:
Each subdivision and/or site plan submitted
to the Township Planning and/or Zoning Board shall be reviewed by
the Planning Board Engineer to establish requirements to prevent adverse
drainage conditions relating to drainage facility, roads or nearby
properties. Water retention basins may be required for flood control
and erosion control purposes in accordance with § 131-35
hereof.
A. On-site drainage easements. Drainage and flood control
easements will be required across lands of the subdivider and/or developer
where stormwaters flow directly or indirectly to or from a Township
street, road or drainage structure.
B. Calculation basis.
(1) Rainfall intensity. Provisions shall be made for a
minimum time of concentration of 10 minutes for the following frequencies:
(a)
Minor inlets: two-year recurrence interval.
(b)
Inlets at low points: five-year recurrence interval.
(c)
Sump inlets: ten-year recurrence interval.
(d)
Stream structures with no headwaters: twenty-five-year
recurrence interval.
(e)
Stream structures with headwaters: one-hundred-year
recurrence interval.
(2) Runoff determination.
(a)
In setting the value of the runoff coefficient "C," consideration will be given to the physical features of the drainage basin and the Planning Board's estimate of its future development, giving due consideration to Chapter
700, Zoning. In general, the value of the runoff coefficient "C" will fall within the following range:
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Classification
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Runoff Factor "C"
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Park lands, golf courses, etc.
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0.15 to 0.30
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Open residential, single family
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0.30 to 0.50
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Multifamily residential and business
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0.50 to 0.70
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Commercial and industrial
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0.70 to 0.90
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(b)
In computing runoff, the rational formula shall
be used for all watersheds of five acres or less:
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Q = CIA
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Where:
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Q
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=
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Volume, in cubic feet per second
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C
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=
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Runoff factor
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---|
|
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I
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=
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Intensity of rainfall, in inches per hour
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A
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=
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Watershed area, in acres
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(c)
Where the watershed exceeds five acres but is
less than one square mile, the runoff shall be calculated using the
Soil Conservation Service Method. Special Report No. 38 as prepared
by the United States Geological Survey shall be used in computing
the runoff for all watersheds equal to or greater than one square
mile.
(3) Pipeline and open channel hydraulics. All storm sewers
shall serve two major functions, to carry the maximum discharge for
which it is designed and to transport suspended solids in such a manner
that deposits in the sewer are kept to a minimum.
C. Open channel design.
(1) Permissible design velocities, feet per second.
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Excavation Material
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Velocity
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Fine sand to firm loam
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2.5 to 3.5
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Stiff clay to hardpan
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3.75 to 6
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Concrete-lined ditch
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15
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Velocity shall be controlled by the use of check
dams or ditch banks and shall be protected by the use of sod, riprap
or paving, as design velocity dictates.
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(2) Discharge flow: Manning's formula.
(3) Values of "n," Manning's formula:
(a)
Best concrete-lined ditch: 0.015.
(b)
Best unlined ditch: 0.025.
(c)
Fair to poor natural streams and watercourses:
0.03 to 0.15.
D. Pipe flow design criteria. All stormwater piping shall
be designed using Manning's formula for flow in pipes.
(1) Pipes shall be considered flowing full at maximum
capacity.
(2) Minimum design velocity at flowing-full condition
shall be 3 1/2 feet per second.
(3) Friction factor "n" shall be 0.012 for circular cross
section nonporous concrete pipe. Other cross sections or pipe materials
shall have commensurate friction factors as may be approved by the
Township Engineer.
E. Sewer pipe; type required. Pipe used shall be reinforced
concrete pipe, Class III, Wall B with O-ring-type joint, unless otherwise
directed by the Township Engineer. All pipe shall be installed with
not less than two feet depth of cover over the top of the pipe. If
the pipe is to be installed with less than two feet of cover, proper
engineering mechanics calculations shall be submitted. These calculations
shall indicate that an HS-20 wheel load can be safely supported by
the pipe within the limits of a 0.1 "D" flexure crack.
F. Line transitions. In pipe sizes of 48 inches or less
in diameter, all transitions in slope, horizontal direction, junctions
and change in pipe sizes shall be confined to manholes, catch basins,
or other accessible structures designed for one or more of these purposes.
In pipe lines 48 inches and larger, vertical and horizontal deflections
may be accomplished by using one-hundred-foot or greater radius curves.
G. Catch basin and manhole type required. Catch basins
and manholes shall be constructed in accordance with New Jersey State
Standard Specifications for Road and Bridge Construction, 1961 Edition,
including amendments thereto. The casting curb head height shall be
two inches greater than the curb height specified. Castings shall
conform to New Jersey State Standards.
H. Inlet spacing. Inlet spacing shall not exceed 600
feet or a design inlet flow of 55 cubic feet per second, whichever
condition shall be more stringent. Access manholes shall be spaced
at eight-hundred-foot intervals, maximum, through rights-of-way and
at sewer junctions where there are no catch basins. Discharge and
collection systems shall not be designed for inlet heads under any
circumstances.
I. Intersections and gutters. A sufficient number of
catch basins shall be installed at each street intersection to avoid
the use of rocker gutters or gutter overflow. Catch basins shall also
be installed at all low points in the street grade.
J. Headwalls. The ends of pipe starting or terminating
in open ditches shall have headwalls. The size, shape and type of
materials to be used for headwalls shall be as approved by the Township
Engineer. When outlet velocities will cause erosion, energy dissipaters
will be required.
K. Stormwater discharge. No subdivided tract, either
during construction or after development, shall discharge stormwater
to contiguous neighbors in a quantity, in cubic feet per second, that
exceeds the tract discharge in its natural undeveloped stage. The
quantity of natural and developed discharge shall be determined utilizing
natural and developed runoff parameters and an intensity of 6.0 inches
of rainfall in 24 hours. The excess stormwater shall be suitably detained
and discharged at the preconstruction quantity. The detention devices'
performance shall also be investigated for storms of lesser frequency.
If no watercourse is available for discharge, a retention basin with
groundwater recharge may be permitted after the applicant has demonstrated
the feasibility of successful operations.
L. Outlet trenches.
(1) The installation of subbase outlet trenches will be
required in roadways at all inlets as follows:
(a)
Low points: two outlet trenches per each inlet.
(b)
Intermediate inlets: one per each inlet installed
on the upgrade side of the inlet.
(2) Subbase outlet trenches may be waived if the developer
can demonstrate that the subgrade soils will adequately dissipate
any water entering the subbase of the roadway.
M. Detention basins in residential subdivisions should
be designed as an open space amenity and comply with the following:
(1) The maximum side slope of any basin shall be 3:2 with
4:1 recommended, and shall be constructed with side slope protection
consisting of a minimum of four inches of topsoil and sod, pegged
in place.
(2) The minimum depth from the bottom of any infiltration
basin to the seasonal high water table (SHWT) shall not be less than
two feet.
(3) The maximum overall depth of any basin should not
exceed six feet from the top of the berm to the bottom of the basin
(i.e., invert elevation of the outfall structure).
(4) If a homeowners' association is formed, the developer/applicant
shall fund the maintenance of the basin with a capital contribution
to a trust fund, of which the interest will be available for the maintenance
of the basin. In the event the association ceases to exist or defaults,
the trust fund will accrue to the Township, which will use the interest
of such funds to maintain the basin. The amount of the contribution
will be determined by the Township Engineer based upon estimates prepared
by the applicant's engineer. The estimate will be based on an amount
equal to the basin maintenance over a two-year period.
[Added 11-2-1993 by Ord. No. 18-1993]
A. There shall be included in any new multifamily housing
development that requires subdivision or site plan approval at least
one indoor or outdoor recycling area for the collection and storage
of residentially generated recyclable materials. The dimensions of
the recycling area shall be sufficient to accommodate recycling bins
or containers which are of adequate size and number, and which are
consistent with anticipated usage and with current methods of collection
in the area in which the project is located. The dimensions of the
recycling area and the bins or containers shall be determined in consultation
with the municipal recycling coordinator, and shall be consistent
with the district recycling plan adopted pursuant to Section 3 of
P.L. 1987, c. 102 (N.J.S.A. 13:1E-99.13) and any applicable requirements
of the municipal master plan, adopted pursuant to Section 26 of P.L.
1987, c. 102. Multifamily housing developments of less than 10 dwelling
units may, at the option of the Planning Board, submit an alternative
recycling plan.
B. The recycling area shall be conveniently located for
the residential disposition of source separated recyclable materials,
preferably near, but clearly separated from, a refuse dumpster.
C. The recycling area shall be well lit, and shall be
safely and easily accessible by recycling personnel and vehicles,
collection vehicles shall be able to access the recycling area without
interference from parked cars or other obstacles. Reasonable measures
shall be taken to protect the recycling area, and the bins or containers
placed therein, against theft of recyclable materials, bins or containers.
D. The recycling area or the bins or containers placed
therein shall be designed so as to provide protection against adverse
environmental conditions which might render the collected materials
unmarketable. Any bins or containers which are used for the collection
of recyclable papers or cardboard, and which are located in an outdoor
recycling area, shall be equipped with a lid, or otherwise covered,
so as to keep the paper or cardboard dry.
E. Signs clearly identifying the recycling area and the
materials accepted therein shall be posted adjacent to all points
of access to the recycling area. Individual bins or containers shall
be equipped with signs indicating the materials to be placed therein.
F. Landscaping and/or fencing shall be provided around
any outdoor recycling area and shall be developed in an aesthetically
pleasing manner.