No application for development shall be approved
unless the Township Engineering Department has certified to the approving
authority in writing that:
A. The applicant has provided the Engineering Department
with sufficient information for it 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 the standards and design
criteria set forth in this article.
[Amended 11-18-1991 by Ord. No. 91-33]
No land area in the Township shall be developed
so that:
A. The drainage of any adjacent area is adversely affected.
B. The natural drainage pattern of the area is significantly
altered.
C. Soil erosion during and after development is increased
over the natural erosion rate.
D. Any downstream area is subjected to increase in flooding
or erosion.
In order to duplicate as nearly as possible
natural drainage conditions, the 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 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
water.
[Amended 11-18-1991 by Ord. No. 91-33]
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. Dry wells or leaching basins which control stormwater
runoff through ground absorption and temporary storage.
D. Porous asphaltic pavement, 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 stores
and dissipates stormwater through ground absorption.
F. Any combination of the abovementioned techniques which serves to limit stormwater runoff from a given site to conform to the requirements of §
126-280, Runoff standards.
[Amended 11-18-1991 by Ord. No. 91-33]
G. Preservation of natural vegetation.
H. Plantings and trees shall not be used in detention
basins.
[Added 11-18-1991 by Ord. No. 91-33]
[Amended 11-18-1991 by Ord. No. 91-33]
A. Existing stormwater runoff and proposed inflow hydrographs
shall be determined by the United States Department of Agriculture,
Soil Conservation Service, Technical Release No. 55, Urban Hydrology
for Small Watersheds (TR-55) method, as amended, by the Handbook for
Stormwater Detention Basins, Somerset County, New Jersey, and the
most recent addendum of each publication, or as modified by the Township
Engineer.
B. Existing and proposed peak stormwater runoff rates shall be determined by the method specified above, for the one- , ten-and one-hundred-year design storms. The existing and proposed peak flow shall be compared for each storm so that conformance with §
126-280, Runoff standards, may be determined by the Township Engineer.
C. Hydrographs for storms other than the one , ten- and
one hundred-year design storms and existing and/or proposed conditions
may be required by the Township or other concerned agencies.
D. If the conditions of §
126-280, Runoff standards, are not met by the proposed condition, on-site stormwater detention and/or ground absorption shall be provided to create conditions which do comply. If a regional detention facility is currently available and if the Township Engineer approves, the developer may be allowed to make a contribution to the regional facility instead of constructing a basin on site.
E. Detention basin routings for the one- , ten- and one-hundred-year
design storms shall be provided along with detention basin plans and
performance statistics. Routings for other design storms may also
be required by the Township.
F. Copies of calculations required for other concerned
agencies shall also be provided to the Township.
G. Berms and dikes used to create impoundment areas shall
be adequately stabilized and the slopes protected against failure
or breaching. The control structure design and berm core materials
shall be chosen to prevent seepage through the berm. Detention basin
berms shall be designed to comply with applicable New Jersey Department
of Environmental Protection and Soil Conservation Service regulations
and the Somerset County Handbook for Stormwater Detention Basins.
H. Minimum slopes within detention basins shall be 2%
for vegetated areas and swales. A minimum slope of 1% shall be allowed
for smooth, impervious low flow channels.
I. Outfalls from detention/retention basin shall design to be stable and not to create conditions which violate §
126-280, Runoff standards.
J. Detention/retention basins should be situated on the
site so as to naturally intercept the runoff for the one-hundred-year
Somerset TR 55 storm. If the basin cannot be situated to naturally
intercept overflow from the storm sewer system, then the portions
of the storm sewer system necessary to intercept the storm runoff
prior to its leaving the site must be able to convey the one-hundred-year
Somerset County TR-55 storm to the basin.
K. 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.
L. Retention basins shall be designed to maintain a minimum
water level of three feet year round.
M. Seepage pits should be designed to contain 85% of
the runoff volume of the developed one-hundred-year design storm.
The alternative shall be to design the seepage pit as a detention
basin with the percolation as the outflow control. The developed one-hundred-year
storm hydrograph shall be used for this design.
N. Ground absorption systems shall only be used 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.
O. The use of underground detention for public facilities
is discouraged for reasons of maintenance. If, in the opinion of the
Township Engineer, there is not a viable alternative to an underground
facility, it shall be incumbent on the applicant to provide a design
which is maintainable. Such systems must have access manholes with
rungs at all junction and pipe ends; be constructed of durable materials;
have sufficient inside dimensions to allow for a person to walk (60
inches high minimum); and have a minimum pitch of 1%.
P. Underground detention on commercial sites must also be designed for ease of maintenance, but the physical requirements will be reviewed individually. The plan shall include a maintenance schedule acceptable to the Township Engineer for the owner. Deviation from the schedule will be considered a variation from the approval site plan. (See §§
126-109,
126-113 and
126-115.)
Q. Provisions shall be made to provide for emergency overflow. Overflow shall be contained or directed such that no adverse conditions are created on site and that the conditions of §
126-280, Runoff standards, are not violated.
R. 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 Council, the procedures for the construction, dedication and acceptance and maintenance of such facilities set forth in Part
9, Subdivisions, of this chapter, including but not limited to performance and maintenance bonds, inspections, etc., shall govern.
S. 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
Commission as approved by the Township Engineer or the Somerset-Union
Soil Conservation District under agreement, except where the Township
Engineer has determined that conditions peculiar to a certain site
warrant exception.
T. 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.
[Added 4-4-2005 by Ord. No. 05-12]
Landscaping design for stormwater facilities
shall utilize the plant selections and designs in accordance with
New Jersey Stormwater Best Management Practices Manual, Chapter 7.
Any departure from the species/designs identified in Chapter 7 will
not be accepted unless there is a written request for such departure,
which characterizes the unique circumstances that necessitate an alternate
approach. The Township reserves the right to select species from Chapter
7 that will require minimal maintenance and that will create minimal
vegetative litter that might otherwise clog the drainageways and outlet
structures.
Prior to the granting of any site development
approval, the applicant may be required to enter into an agreement
with the municipality, in form satisfactory to the Municipal 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 Part 11, provided 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 or 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 or by another
qualified engineer acceptable to 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.