The purpose of this chapter is to establish
minimum stormwater management requirements and controls to protect
and safeguard the general health, safety, and welfare of the public
residing in watersheds within this jurisdiction. This chapter seeks
to meet that purpose through the following objectives:
A. Minimize increases in stormwater runoff from any development
in order to reduce flooding, siltation, increases in stream temperature
and stream bank erosion and maintain the integrity of stream channels
B. Minimize increases in nonpoint source pollution caused
by stormwater runoff from development which would otherwise degrade
local water quality.
C. Reduce stormwater runoff rates, soil erosion and nonpoint
source pollution, wherever possible, through stormwater management
controls and to ensure that these management controls are properly
maintained and pose no threat to public safety,
This chapter is not intended to interfere with,
abrogate, or annul any other ordinance, rule or regulation, statute,
or other provision of law. The requirements of this chapter should
be considered minimum requirements, and where any provision of this
chapter imposes restrictions different from those imposed by any other
ordinance, rule or regulation, or other provision of law, whichever
provisions are more restrictive or impose higher protective standards
shall be considered to take precedence.
If the provisions of any article, section, subsection,
paragraph, subdivision or clause of this chapter shall be judged invalid
by a court of competent jurisdiction, such order of judgment shall
not affect or invalidate the remainder of any article, section, subsection,
paragraph, subdivision or clause of this chapter.
The Town of Westerly may furnish additional
policy, criteria and information, including specifications and standards,
for the proper implementation of the requirements of this chapter
and may provide such information in the form of a stormwater design
manual. This manual will include a list of acceptable stormwater treatment
practices, including the specific design criteria and operation and
maintenance requirements for each stormwater practice. The manual
may be updated and expanded from time to time, at the discretion of
the Planning Board, based on improvements in engineering, science,
monitoring and local maintenance experience. Stormwater treatment
practices that are designed and constructed in accordance with these
design and sizing criteria will be presumed to meet the minimum water
quality performance standards.
As used in this chapter, the following terms
shall have the meanings indicated:
ACCELERATED EROSION
Erosion caused by development activities that exceeds the
natural processes by which the surface of the land is worn away by
the action of water, wind, or chemical action.
APPLICANT
A property owner or agent of a property owner who has filed
an application for a stormwater management permit.
BUILDING
A structure, either temporary or permanent, having walls
and a roof, designed for the shelter of any person, animal, or property,
and occupying more than 100 square feet of area.
CHANNEL
A natural or artificial watercourse with a definite bed and
banks that conducts continuously or periodically flowing water.
DEDICATION
The deliberate appropriation of property by its owner for
general public use.
DETENTION
The temporary storage of storm runoff in a stormwater management
practice with the goals of controlling peak discharge rates and providing
gravity settling of pollutants.
DETENTION FACILITY
A detention basin or alternative structure designed for the
purpose of temporary storage of stream flow or surface runoff and
gradual release of stored water at controlled rates.
DEVELOPER
A person who undertakes land disturbance activities.
DRAINAGE EASEMENT
A legal right granted by a landowner to a grantee allowing
the use of private land for stormwater management purposes.
HOTSPOT
An area where land use or activities generate highly contaminated
runoff, with concentrations of pollutants in excess of those typically
found in stormwater.
HYDROLOGIC SOIL GROUP (HSG)
A Natural Resource Conservation Service classification system
in which soils are categorized into four runoff potential groups.
The groups range from A soils, with high permeability and little runoff
production, to D soils which have low permeability rates and produce
much more runoff.
IMPERVIOUS COVER
Those surfaces that cannot effectively infiltrate rainfall
(e.g., building rooftops, pavement, sidewalks, driveways, etc).
INDUSTRIAL STORMWATER PERMIT
A National Pollutant Discharge Elimination System permit
issued to a commercial industry or group of industries which regulates
the pollutant levels associated with industrial stormwater discharges
or specifies on-site pollution control strategies.
INFILTRATION
The process of percolating stormwater into the subsoil.
INFILTRATION FACILITY
Any structure or device designed to infiltrate retained water
to the subsurface. These facilities may be above grade or below grade.
LAND DISTURBANCE ACTIVITY
The grading, digging, cutting, scraping, or excavating of
soil, placement of fill materials, paving, construction, substantial
removal of vegetation, or any activity which bares soil or rock or
involves the diversion or piping of any natural or man-made watercourse.
LANDOWNER
The legal or beneficial owner of land, including those holding
the right to purchase or lease the land, or any other person holding
proprietary rights in the land.
NONPOINT SOURCE POLLUTION
Pollution from any source other than from any discernible,
confined, and discrete conveyances, and shall include, but not be
limited to, pollutants from agricultural, silvicultural, mining, construction,
subsurface disposal and urban runoff sources.
OFFSET FEE
A monetary compensation paid to a local government for failure
to meet pollutant load reduction targets.
RECHARGE
The replenishment of underground water reserves.
REDEVELOPMENT
Any construction, alteration or improvement exceeding 10,000
square feet in areas where existing land use is high-density commercial,
industrial, institutional or multifamily residential.
STOP-WORK ORDER
An order issued which requires that all construction activity
on a site be stopped.
STORMWATER MANAGEMENT
The use of structural or nonstructural practices that are
designed to reduce stormwater runoff pollutant loads, discharge volumes,
peak flow discharge rates and detrimental changes in stream temperature
that affect water quality and habitat.
STORMWATER RETROFIT
A stormwater management practice designed for an existing
development site that previously had either no stormwater management
practice in place or a practice inadequate to meet the stormwater
management requirements of the site.
STORMWATER TREATMENT PRACTICES (STPS)
Measures, either structural or nonstructural, that are determined
to be the most effective, practical means of preventing or reducing
point source or nonpoint source pollution inputs to stormwater runoff
and water bodies.
STORMWATER MANUAL
The town of westerly shall incorporate the RIDEM Stormwater
Design Manual and Installation Manual, latest revision.
WATER QUALITY VOLUME (WQv)
The storage needed to capture and treat 90% of the average
annual stormwater runoff volume. Numerically (WQv) will vary as a function of long-term rainfall statistical data.
WATERCOURSE
A permanent or intermittent stream or other body of water,
either natural or man-made, that gathers or carries surface water.
Unless judged by the Town of Westerly to be
exempt or granted a waiver, the following performance criteria shall
be addressed for stormwater management at all sites:
A. All site designs shall establish stormwater management
practices to control the peak flow rates of stormwater discharge associated
with specified design storms and reduce the generation of stormwater.
The stormwater management practice should conform to RIDEM best management
practices.
B. All stormwater runoff generated from new development
shall not discharge untreated stormwater directly into a jurisdictional
wetland or local water body without adequate treatment. Where such
discharges are proposed, the impact of the proposal on wetland functional
values shall be assessed using a method acceptable to the Town of
Westerly. In no case shall the impact on functional values be any
less than allowed by the Army Corp of Engineers (ACE) or the appropriate
state agency (RIDEM or CRMC).
C. Annual groundwater recharge rates should be maintained
by promoting infiltration through the use of structural and nonstructural
methods.
D. For new development, structural stormwater treatment
practices shall be designed to remove 80% of the average annual postdevelopment
total suspended solids load (TSS). As defined by RIDEM BMPs.
E. Protect stream channels from degradation, a specific
channel protection criteria shall be provided as prescribed in the
current stormwater manual.
F. Stormwater discharges to critical areas with sensitive
resources (i.e., cold-water fisheries, shellfish beds, swimming beaches,
recharge areas, water supply reservoirs) may be subject to additional
performance criteria, or may need to utilize or restrict certain stormwater
management practices.
G. Industrial sites are required to prepare and implement
a stormwater pollution prevention plan, and shall file a notice of
intent (NOI) under the provisions of the National Pollutant Discharge
Elimination System (NPDES) general permit. The stormwater pollution
prevention plan requirement applies to both existing and new industrial
sites.
H. Prior to design, applicants are required to consult
with the Town Planner to determine if they are subject to additional
stormwater design requirements.
I. Calculations for determining peak flows as found in
the stormwater design manual shall be used for sizing all stormwater
management practices.
All applicants are required to submit as built
plans for any stormwater management practices located on-site after
final construction is completed. The plan must show the final design
specifications for all stormwater management facilities and must be
certified by a Rhode Island professional engineer or land surveyor.
A final inspection by the Town of Westerly is required before the
release of any performance securities can occur.