The following measures represent the minimum
requirements necessary to satisfy the no net increase provisions of
this chapter. A project's stormwater management plan shall be designed
in accordance with the Department of Community Affairs' Residential
Site Improvement Standards (N.J.A.C. 5:21) as promulgated, the requirements
of the Municipal Land Use Law (N.J.S.A. 40:55D-95), the provisions
of the Soil Erosion and Sediment Control Act (N.J.S.A. 4:24-39) and
any NJDEP approved stormwater management regulations. For guidance
regarding conformance with the provisions of this chapter, applicants
are directed to the "Stormwater and Nonpoint Source Pollution Control
Best Management Practices Manual" (BMP Manual) dated December 1994
and authored by NJDEP and New Jersey Department of Agriculture, or
the most recent revision thereto. Applicants will be required to demonstrate
that the project plan has considered current techniques suitable for
attaining the objectives of this chapter.
A. No net increase in stormwater quantity.
(1) Stormwater control systems.
(a)
Stormwater control systems shall be designed
to control stormwater runoff resulting from a development site such
that the postdevelopment peak runoff rates from the site shall be
50% of the predevelopment peak for the two-year storm event, 75% of
the predevelopment peak for the ten-year storm event and 80% of the
predevelopment peak for the one-hundred-year storm event.
(b)
If a stormwater management plan for the region or watershed containing the watercourse affected by the proposed development has been adopted, the project's stormwater control systems shall be designed to conform to that regional or watershed plan, to the extent practicable in satisfying the requirements of Subsection
A(1)(a) above.
(c)
Stormwater control systems shall be designed,
to the extent practicable, to infiltrate the quantity of runoff that
exceeds predevelopment runoff for the NJDEP Water Quality Design Storm
(1.25 inch two-hour rainfall). If infiltration on site for the design
storm is not practicable (i.e., for example based on soil permeability
constraints, topography or groundwater level considerations), an applicant
shall provide off-site mitigation subject to the approval of the Planning
Board prior to project commencement. Options for mitigation are as
follows:
[1]
The acquisition of and mitigation on privately
owned lands, preferably adjacent to state open water and nearby and
within the same drainage basin, located in the sewer service area/applicable
watershed to be dedicated for preservation or reforestation, in equivalent
size and used to off set the increase in volume of the 1.25 inch two-hour
rainfall from the proposed development site.
[2]
Mitigation on previously developed properties,
public or private, and preferably nearby within the same drainage
basin, that currently lack stormwater management facilities designed
and constructed in accordance with the purposes and standards of this
chapter. A construction cost estimate of a suitable infiltration system
sized for the proposed development based on the assumption that average
permeability had existed on the subject property shall be prepared
and submitted by the applicant's professional engineer. Upon certification
by the Township Engineer that the proposed design and estimate are
reasonable, the amount so determined will be the amount required to
fund the mitigation measures on previously developed properties in
order to offset increase in volume of the 1.25 inch two-hour rainfall
from the proposed development site.
[3]
Funding specific projects recommended in watershed
based stormwater management plans in order to offset the increase
in volume of the 1.25 inch two-hour rainfall from the proposed development
of the site.
[4]
Funding stormwater related studies or regional
stormwater management plans approved by the Township Council in an
amount equivalent to a construction cost estimate of a suitable infiltration
system sized for the proposed development submitted and prepared by
the applicant's professional engineer and approved by the Township
Engineer or Planning Board Engineer and local approving authority.
(2) This requirement shall be applied equally to all applications
for development and redevelopment within the sewer service area portion
of Greenwich Township. Increased stormwater runoff shall be calculated
by the applicant's engineer and approved by the Township Engineer
or Planning Board Engineer and local approving authority utilizing
accepted engineering practices.
B. No net increase in stormwater pollutant loads.
(1) Stormwater control system shall be designed to the
extent practicable so that there is no calculated or anticipated increase
from predevelopment to post development conditions in conventional
pollutant loads (e.g., total suspended solids, nitrogen, phosphates,
etc.) to the receiving watercourse due to stormwater runoff. Compliance
with this provision shall be attained when it is demonstrated that
the project's stormwater management plan has considered current BMPs
(e.g., those presented in the NJDEP BMP Manual) for applicability
to the project in order to achieve the goal of no net increase in
stormwater pollutant loads. Implementation of these measures should
be successful in achieving 80% removal of total suspended solids loading
and therefore meet this goal. The applicant shall not be required
to install BMPs which exceed the goal, but, where possible, is strongly
encouraged to do so. The applicant must provide economic or other
justification where implementation of the plan is not predicted to
achieve compliance with the goal of no net increase in stormwater
pollutant loads.
(2) Nonstructural stormwater management practices shall
be utilized prior to the use of structural management measures, unless
it is demonstrated that these practices are not feasible from an engineering,
environmental or economic perspective on a particular site. Nonstructural
measures include elements of site design to protect water quality
(e.g., vegetated buffers adjacent to watercourses, limitations on
use of impervious surfaces, limitations on site disturbance, use of
native vegetation, and requirement of appropriate fertilizer and pesticide
use).