[HISTORY: Adopted by the Board of Trustees of the Village
of Roslyn as indicated in article histories. Amendments noted where
applicable.]
[Adopted 3-21-2006 by L.L. No. 2-2006 (Ch. 22-A of the 2000
Code)]
Regulating the quantity and quality of stormwater runoff stored
and recharged, and the means of collecting and transmitting stormwater,
is essential to maintaining the safety and public welfare of the Village
of Roslyn and its residents. Regulating and improving the quantity
and quality of the stormwater recharged into the ground and discharged
into Hempstead Harbor or tributaries of Hempstead Harbor are vital
to preserving the quality of Long Island's drinking water supply
and the designated Significant Coastal Fish and Wildlife Habitat associated
with Hempstead Harbor and the Hempstead Harbor Creek. The purpose
and objectives of this article are to improve and regulate stormwater
management and erosion control management within the Village resulting
in the enhancement of the stormwater quality which recharges into
the ground and discharges into Hempstead Harbor in accordance with
the Village's responsibilities associated with Stormwater National
Pollutant Discharge Elimination System (NPDES) Phase II Regulations.
A.
Plans submitted for review. Plans submitted shall be submitted to
the Department of Public Works for its review and shall consist of
a plot plan, drainage plans, erosion and sedimentation control plan
and profile plans where applicable.
B.
Drainage plan.
(1)
The drainage plan shall include both existing and proposed topographic
information plotted at two-foot intervals for the property proposed
for development and the immediate surrounding area. Where required,
information may need to be provided to assess any contribution from
outside sources that may contribute runoff to the site proposed for
development. The property shall not be regraded for the purpose of
directing site runoff to off-site areas.
(2)
The drainage plan shall show all means of collecting property runoff
whether by means of catch basins, area drains, swales, roof drains
or other collection devices. The drainage plan shall also show adequate
information for the analysis of the drainage system directing runoff
to collection areas. Information to be provided shall include, at
a minimum, types of drainage structures, inlet elevations, pipe inverts,
pipe sizes and gradients. Applicable drainage details are to be shown
on separate sheets of the subdivision plans. For any subdivision proposing
the creation of a stormwater basin or basins, a separate plan shall
be included for each basin delineating the proposed configuration
and is to include all details of structures or devices proposed for
directing and storing runoff, location and details pertaining to plant
screenings and fence details. The stormwater basin plan shall show
the proposed high-water mark utilized in determining the storage proposed
for that basin. The plans shall show locations of all drainage reserve
areas (DRAs) proposed for the storage of runoff, including shape,
elevations and contours, for the assessment of storage capacity. The
drainage plan shall also include all calculations pertaining to the
assessment of the storage requirement for the subdivision on the plans.
Additional information may be requested to justify the assumptions
concerning flows from outside areas, flow capacities for specific
pipe diameters and storage of runoff.
C.
Erosion and sedimentation control plan. The erosion and sedimentation
control plan shall include details to be enacted during construction
to prevent or limit the migration of sediments from the site as a
result of construction practices. The plan shall also include details
showing the protection measures to be utilized to prevent sediment
contamination of any on-site or applicable off-site drainage structures.
The methods proposed shall conform to the New York State Stormwater
Management Design Manual and the New York Standards and Specifications
for Erosion and Sediment Control. The institution and enactment of
these measures during construction are solely the responsibility of
the developer.
D.
Profile plan. The profile plan, for subdivisions where roads are
proposed, shall include proposed stations, gradients and pertinent
data necessary to define any proposed vertical curves, including overall
length. Drainage structures and interconnecting pipes are to be plotted
corresponding to the information shown on the drainage plan. All information
pertaining to the roadway drainage system is to be included, such
as pipe sizes, gradients and inverts, surface grades for structures
and applicable location associated with roadway stations. Other information
may be included if it assists in the analysis.
A.
On-site drainage storage requirement.
(1)
Developers are responsible for providing storage for eight inches
of runoff from the subdivision's tributary area, whether contributed
from on-site or off-site sources. The storage can be provided through
construction of stormwater basins, drainage reserve areas, installation
of dry wells, or by other storage devices deemed acceptable by the
Village. The storage volume requirement is to be determined utilizing
the following formula:
|
Volume = A x C x 8"/12"
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|---|---|---|---|---|
|
A
|
=
|
Tributary area in square feet.
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|
C
|
=
|
Runoff coefficient determined.
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B.
Waiver of storage requirement.
(1)
The Village is aware that conditions may exist which could affect
the potential of providing the storage required herein for specific
sites. The developer may request a waiver of a portion of the storage
requirement. A letter outlining the hardship and limitations for reaching
the potential storage goal shall be forwarded to the Village for consideration.
The letter shall include the following information:
(2)
Should the proposed subdivision direct overflow runoff into water
bodies under the jurisdictional control of the New York State Department
of Environmental Conservation (NYSDEC), the developer will be required
to forward a copy of any permits required by NYSDEC pertaining to
the overflow.
(3)
The Village will evaluate the information submitted and will consider
the request. However, developers are responsible for providing the
maximum amount of storage the site permits in an effort to attain
the eight-inch requirement.
(4)
Where the Village concurs with the hardship, the developer will be
primarily required to install a stormwater treatment system to improve
water quality and runoff volume and secondarily will be subject for
the payment of compensation to the Village. Stormwater treatment units
shall be designed to meet the requirements of stormwater treatment
criteria outlined herein and with current general best management
practices (BMPs). If the installation of a stormwater treatment system
is not feasible, the Village will seek compensation as follows for
improvements relative to water quality and flood mitigation elsewhere
within the Village. For waiver where the on-site storage is less than
eight inches but is five inches or greater, there will be no fee.
However, if the volume of storage provided under the design is less
than five inches of runoff from the tributary area, the developer
is responsible for paying compensation to the Village for the volume
of storage less than five inches. The fee payable to the Village per
every 1,000 cubic feet of storage deficient of not meeting the Village's
standard shall be determined by resolution of the Board of Trustees.
If the developer chooses to pay the compensation, the following note
is to be included on the street grading and drainage plan: "The developer
will pay a fee of ________ to the Village of Roslyn as compensation
for a partial waiver of drainage requirements, upon approval of the
subdivision."[1]
(5)
The fee is assessed to compensate the Village for the added maintenance
cost incurred as a result of accepting responsibility for the maintenance
of the site overflow associated with the stricter control of runoff
mandated by federal regulations enacted under Phase II of the Stormwater
Discharge Program and as may be amended. Where sites overflow solely
to facilities maintained by municipalities other than the Village,
the developer shall be responsible for providing the storage of runoff
that satisfies that municipality's requirement. A letter from
the municipality holding jurisdiction shall be forwarded to the Village
stating that the municipality is willing to accept the overflow runoff.
This letter is required prior to the Village's agreement to any
reduction in the eight-inch storage requirement. The Village will
not approve any waiver for less than two inches of storage on site.
A.
General plan requirements.
(1)
A plot plan shall be submitted showing metes and bounds of subdivision
property and individual lots. The plot plan shall be stamped and signed
by a licensed surveyor or licensed professional engineer.[1]
(2)
A drainage plan shall be submitted containing sufficient information
to determine if the Village drainage requirements have been met. The
drainage plan is to be stamped and signed by a licensed professional
engineer.[2]
(3)
The plot plan and drainage plan shall include a key map showing the
general location of the proposed subdivision.
(4)
The minimum scale for the plot plan and drainage plan shall be one
inch equals 100 feet.
(5)
A North arrow shall be included on the plot plan and drainage plan.
(6)
The plot plan and drainage plan shall provide consistent information.
(7)
Profile plan grades shall be defined by center-line elevations, waterline
grades or top of curb grades. The plan(s) shall denote proper designation.
(8)
The drainage plan and profile plan shall show locations of proposed
drainage structures and proposed drainage pipe. Information shall
be consistent.
(9)
Drainage structures, pipe diameters and inverts shall be identified
on the profile plan.
(10)
Elevations shall conform to Nassau County's datum. A note
indicating datum shall be placed on plans.
(11)
The drainage plan shall include existing and proposed contour
elevations set at two-foot increments.
(12)
The plans shall contain appropriate notes designating dedication
of roadways, easements, conservation areas, stormwater basins, drainage
reserve areas, or other applicable easements.
(13)
Minimum drainage easements shall be 10 feet in width.
(14)
Location of sanitary sewers and utilities is to be shown on
the plot plan or separate sewer plan.
(15)
Test holes are required at proposed stormwater storage site(s).
A representative of the Village shall be on site to witness the results
of test holes. Test hole log information is to be included on plans
in subsequent plan submissions.
(16)
Approvals, where applicable, shall be required from New York
State Department of Transportation, New York State Department of Environmental
Conservation, or other authorities holding jurisdiction as might be
required by the site. It is the responsibility of the engineer acting
as agent for the developer to determine if an approval is required
from any agency having interest. Copies of approvals or permits required
by these authorities are to be forwarded to the Village.[3]
(17)
All areas regulated by the New York State Department of Environmental
Conservation shall be defined on the drainage plan.
B.
Drainage pipe design criteria.
(1)
Drainage pipe shall be of sufficient diameter and set at an appropriate
gradient to accommodate the flow determined by the requirements of
the tributary area.
(2)
Minimum size pipe on Village roads shall be 18 inches for collector
systems. Fifteen-inch pipe may be allowed for crossover from single-unit
catch basins and leaching pools.
(3)
Minimum cover over drainage pipe is 2.0 feet.
(4)
The grade for the same diameter pipe shall not be flattened after
steep gradients.
(5)
Maximum velocity in pipes shall be 12 feet per second.
(6)
Minimum velocity in pipes shall be 2.5 feet per second.
(7)
Maximum pipe gradient shall be 6%.
(8)
Minimum pipe gradient shall be 0.2%
(9)
Inverts of pipes at catch basin are to be located at a sufficient
depth to provide no conflict with the catch basin's deck.
(10)
A minimum spacing of 10 feet is required between drainage pipes
and water supply lines.
(11)
Pipe material shall be selected and designed for proper strength
relative to loading conditions.
(12)
The design of drainage pipes, conduits or ditches is to be performed
by the use of the Manning Formula:
 | ||||
|---|---|---|---|---|
|
Where:
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|
V
|
=
|
Velocity of flow (feet per second).
| ||
|
n
|
=
|
Manning roughness coefficient (no unit); example: n = 0.013
for precast reinforced concrete pipes.
| ||
|
rh
|
=
|
Hydraulic radius (feet).
| ||
|
s
|
=
|
Slope of the pipe (feet per feet).
| ||
C.
Drainage manholes.
(1)
Maximum distance between manholes shall be 350 feet.
(2)
The design and material standards for drainage manholes shall be
consistent with the requirements of the Nassau County Department of
Public Works (NCDPW).
(3)
Maximum height of a NCDPW Type 1 manhole is 10 feet.
(4)
Manholes greater than 10 feet in depth shall be NCDPW Type 2.
(5)
Differential distance between inverts for drop manholes shall be
no more than 2 1/2 times the diameter of the inlet pipe.
D.
Catch basins.
(1)
The design and material standards for catch basins shall be consistent
with the requirements of the Nassau County Department of Public Works
(NCDPW).
(2)
The maximum tributary area for a NCDPW Type A or B catch basin is
4.5 acres.
(3)
The maximum tributary area for a NCDPW Type C or D catch basin is
9.0 acres.
(4)
Flow-through catch basins are to be NCDPW Type B or D.
(5)
Catch basin inlet elevations are to be shown on the drainage plan
and the profile plan.
(6)
Maximum depth of catch basins is 10 feet.
(7)
Catch basins located on roadways with gradients greater than 5% require
the basin to be recessed. An additional basin shall be located 20
feet downgrade of a recessed basin. A detail of a recessed basin shall
be included on the plans.
(8)
Maximum two catch basins are allowed to be interconnected in a drainage
system; thereafter a proposed drainage manhole structure is required.
(9)
A detail is required showing modifications of existing catch basins.
E.
Yard inlets.
(1)
Structure shall be constructed of reinforced concrete material.
(2)
Minimum required interior dimension is 24 inches by 24 inches (or
24 inches in diameter).
(3)
Maximum four yard inlet structures are allowed to be interconnected
in a drainage system; thereafter a drainage manhole structure is required.
(4)
Maximum allowed depth of any yard inlet is six feet.
A.
The developer, as part of the site development, is responsible for
the installation and maintenance of erosion and sediment control measures
necessary to prevent the transportation of sediments to off-site areas.
The subdivision plans shall include an erosion and sediment control
plan as part of the submission for review. Erosion and sediment control
measures shall be continuously maintained and modified to address
field conditions encountered during various phases of construction.
The erosion and sediment control plan shall include details showing
the intended measures to be employed during construction to meet the
requirements of this section. The specific methods and materials employed
in the installation and maintenance of erosion control measures shall
conform to the New York State Stormwater Management Design Manual
and the New York Standards and Specifications for Erosion and Sedimentation
Control.
B.
Erosion control measures shall include the following:
(1)
The proposed erosion control measures shown on the plans shall be
installed prior to the start of construction. Additional erosion control
measures may be necessary, based upon field conditions that may develop
as construction progresses.
(a)
Existing vegetation to remain shall be protected and remain
undisturbed.
(b)
Clearing and grading shall be scheduled so as to minimize the
size of exposed areas and length of time that areas are exposed.
(c)
The length and steepness of cleared slopes shall be minimized
to reduce runoff velocities and quantities.
(d)
Runoff shall be diverted away from clear slopes.
(e)
Sediment shall be trapped on site.
(f)
Specific methods and materials employed in the installation
and maintenance of erosion control measures shall conform to the New
York State Guidelines for Urban Erosion and Sediment Control.
(2)
Sediment control barriers (silt fence, hay bales or approved equal)
shall be installed prior to any grading work along the limits of disturbances
and shall be maintained for the duration of the work. No sediment
from the site shall be permitted to wash onto adjacent properties
or roads.
(3)
Graded and stripped areas and stockpiles shall be kept stabilized
through the use of temporary seeding or sod as required. Seed mixtures
shall be in accordance with the Natural Resources Conservation Service
(NRCS) recommendations.[1]
(4)
Soils stockpiled on individual lots as a result of excavation for
foundations shall be placed to increase the distance these soils must
travel to reach the drainage system. Stockpiles shall be covered to
reduce sediment loading on the site.
(5)
Drainage inlets installed as part of the project shall be protected
from sediment buildup through the use of sediment barriers, sediment
traps, etc., as required.
(6)
Proper maintenance of erosion control measures shall be performed
as indicated by the periodic inspection after a rainfall event totaling
0.5 inch of rainfall or greater or during a seven-day inspection program
occurring throughout the period of the construction. Maintenance measures
include, but are not limited to, cleaning of sediment basins or traps,
cleaning and repair of berms and diversions and cleaning and repair
of inlet protection devices.
(7)
Appropriate means shall be used to control dust during construction.
(8)
A stabilized construction entrance/exit shall be maintained to prevent
soil and loose debris from being tracked onto adjacent roads. In addition,
a water source is to be maintained adjacent to this entrance for the
purpose of washing debris from truck tires. The construction entrance
shall be maintained until the site is permanently stabilized.
(9)
Sediment barriers and other erosion control measures shall remain
in place until upland disturbed areas are permanently stabilized.
(10)
All slope areas of 1:2 and 1:3 will be protected against erosion
during construction, and permanent ground cover shall be such that
erosion will be prevented. Necessary measures shall include, but not
be limited to, hay bales, silt fence, silt trap/basins, jute mesh,
anchored straw mulch, hydroseeding, sod, etc., and shall be maintained
for the duration of the construction as well as following the completion
of construction until such time that the proposed plantings have become
acclimated/established as determined by the Village's representative.
C.
The plans shall also address the following environmental issues the
developer shall be responsible for during construction:
(1)
Pollution prevention measures to be instituted to prevent litter,
construction chemicals, and construction debris from becoming pollutant
sources in stormwater discharges from the site.
(2)
Description of the method of storing waste materials on site and
a description of controls to be employed to reduce pollutants from
these materials, including storage practices to minimize exposure
of materials to stormwater. Include a spill prevention and response
plan.
(3)
The installation of a portable sanitary system or a sanitary system
established in a field office trailer shall be maintained throughout
the term of the project.
A.
Stormwater treatment devices.
(1)
For subdivisions where overflow runoff from the property's tributary
area enters directly into streams, tidal waters, or roadway drainage
systems, such water shall be routed through on-site treatment devices
in conformance with the New York State Stormwater Design Manual. A
note shall be included on the drainage plan designating maintenance
responsibility for the proposed devices.
(2)
The Village is willing to consider new technologies proposed for
storage. Prior to approval of new technologies, the developer or engineer
shall provide manufacturer information for consideration.
(3)
Stormwater treatment devices shall include methods to store settleable
solids in a manner and a location that will prevent resuspension of
previously captured particulates.
(4)
Stormwater treatment systems shall be of a hydraulic design that
includes flow controls designed and certified by a professional registered
engineer using accepted principles of fluid mechanics that raise the
water surface inside the tank to a predetermined level in order to
prevent the re-entrainment of trapped floating contaminants.
(5)
Stormwater treatment systems shall be capable of removing 80% of
the net annual total suspended solids (TSS) load based on a fifty-micron
particle size. Annual TSS removal efficiency models are to be based
on a documented removal efficiency performance from full-scale laboratory
tests. Annual TSS removal efficiency models shall only be considered
valid if they are corroborated by independent third party field testing.
This field testing is to include influent and effluent composite samples
from a minimum of 10 storm events at one location.
(6)
Stormwater treatment systems and design treatment capacities shall
be submitted to the Village for review. The stormwater treatment system
shall not resuspend trapped sediments or re-entrain floating contaminants
at flow rates up to and including the specified treatment capacity.
(7)
Stormwater treatment units shall have flow control (i.e., weir, orifice)
structures.
B.
Dry wells.
(1)
Excavations for dry wells shall extend to a depth where a minimum
of six feet of permeable leaching material exists.
(2)
Bottoms of dry wells shall be a minimum of two feet above groundwater.
(3)
Dry wells are to be installed with a three-foot collar consisting
of approvable graded leaching material.
(4)
The maximum depth of dry wells and/or diffusion wells is 25 feet.
If suitable leaching material does not occur within the 25 feet, the
excavation shall extend six feet into suitable material and the hole
shall be backfilled with graded material to the proposed bottom elevation
of the dry well.
(5)
A dry well and/or diffusion well detail shall be provided on the
plans.
(6)
The minimum spacing between dry wells shall be 10 feet between outside
walls.
(7)
For condominiums, cooperatives, and townhouses, roof drains shall
be directed into dry wells separate from site drainage unless downspouts
are to be located on the outside of the building(s). If site conditions
prevent the installation of separate dry wells for roof drains, a
note is to be placed on the drainage plan stating that the downspouts
are to be located on the exterior of the building(s).
(8)
Floor drains and trench drains require their own dry wells.
(9)
No storage considerations will be allowed for domed sections.
(10)
No storage credit is allowed for percolation.
(11)
Where dry wells are proposed within individual lots, a note
is to be included on the drainage plans stating that the property
owner or homeowners' association is responsible for the maintenance
of these structures.
C.
Drainage reserve areas (DRAs).
(1)
Drainage reserve areas shall be dedicated either to an individual
homeowner or to the homeowners' association for the developed
property as may be applicable. A note of dedication is to be included
on the plans.
(2)
Maximum depth of drainage reserve areas is four feet. Where drainage
reserve areas extend beyond 30 inches in depth, a five-foot-wide aquatic
berm shall be provided at a level two feet below the anticipated high-water
mark.
(3)
Overflow between drainage reserve areas shall be a minimum of one
foot lower than the roadway grade adjacent to it.
(4)
No fill is to be placed on the site for the purpose of constructing
a drainage reserve area.
D.
Stormwater basins.
(1)
Stormwater basins are to be constructed in conformance with the applicable
sections of the County of Nassau Department of Public Works 1964 Standard
Specifications for the Construction of Highways and Bridges, as subsequently
amended, and the County of Nassau Department of Public Works Standard
Sheets for the Construction of Highways and Bridges.
(2)
The stormwater basin's side slopes are to be graded one on two.
(3)
Stormwater basins shall be constructed with two levels. The lower
level is to be two feet deeper for the purpose of acting as a sedimentation
settling area. The transition slope between the two areas is to be
graded one on three between tiers.
(4)
Drainage pipes connected to stormwater basins shall outfall into
the lower sedimentation area of the basin.
(5)
Drainage pipes which outfall into stormwater basins require a headwall
conforming to the detail shown in the Nassau County Standard Drawings.
(6)
The minimum size pipe to outfall into a stormwater basin is 24 inches.
(7)
The maximum gradient for pipes that outfall into stormwater basins
is 2%.
(8)
Sluiceways are to be constructed in conformance with the Nassau County
Department of Public Works (NCDPW) details.
(9)
Maintenance access ramps shall be 12 feet wide and constructed at
an eight-percent grade from top of berm to bottom of basin. The ramp
is to be tilted with the inside edge constructed six inches higher
than the elevation of the side slope side opposite it.
(10)
Where proposed, the minimum turning radius for ramps shall be
25 feet.
(11)
No topsoil is to be placed on side slopes.
(12)
A six-foot-high chain link fence with its bottom anchored in
a two-foot-deep curb is to be constructed around the perimeter of
the basin with a sixteen-foot-wide access gate located near the vicinity
of the maintenance ramp, both conforming to Nassau County standards.
(13)
A planting screen consisting of approved evergreen trees a minimum
of six feet in height shall be planted along the perimeter of the
stormwater basin. The trees shall be planted in conformance with Nassau
County standard requirements.
(14)
Berms (distance between fence and top of slope) shall be 10
feet or 13 feet wide and one foot higher at top of slope than at the
fence to prevent erosion.
(15)
The fence and plant screening around the basin shall be placed
in accordance with the following format:
(a)
On street fronts, the fence shall be placed five feet inside
the stormwater basin's property line, with an adjacent ten-foot
berm. The five feet outside the fence is for planting.
(b)
On sides abutting property of others, the fence shall be placed
two feet inside the stormwater basin's property line, with an
adjacent thirteen-foot berm. The planting is to be located on the
inside of the fence.
(c)
On sides abutting property of the developer (builder of the
stormwater basin), the fence shall be located two feet inside the
stormwater basin property, with an adjacent ten-foot berm. A five-foot
planting strip shall be located outside the basin's property
line with planting located at the center of the strip.
(16)
A planting detail is to be included on the plans showing the
applicable configuration proposed for the stormwater basins.
(17)
No fill is to be placed for the purpose of creating a stormwater
basin.
(18)
Elevation of anticipated high water is to be shown on the stormwater
basin plan.
(19)
Access to a landlocked stormwater basin shall be provided through
a twenty-foot strip from the street to the basin's entrance and
included as part of the basin's property.
E.
Retention ponds.
(1)
A note is to be included on the drainage plan dedicating maintenance
responsibility for the retention pond to the homeowners' association.
(2)
Retention ponds proposed for aesthetic value without a surrounding
fence will require the construction of a five-foot-wide aquatic shelf
located one foot below the pond's established water level.
(3)
The pond is to be designed to allow the anticipated storage to be
renewed as a result of percolation between storm events.
(4)
Fill is not to be used for the purpose of creating storage.
(5)
The minimum size pipe to outfall into the pond is 24 inches.
(6)
Pipes directing flow to dry wells for restoration of storage retention
shall be back pitched away from the retention pond at a maximum gradient
of 2%.
(7)
The plans shall include all details relevant to the construction
of the retention pond.
F.
Linear leaching chambers.
(1)
Stormwater storage claimed for proposed bedding material shall be
substantiated by an approved testing laboratory. The results shall
be forwarded to the Village for consideration. The results will be
reviewed before permitting claimed storage. A note is to be added
to the detail for this unit stating the tested material is required.
(2)
Bottom of bedding material shall be a minimum of two feet above groundwater.
(3)
A stormwater treatment unit shall be installed to intercept contaminants
before dispersing runoff into leaching units.
(4)
No consideration will be given to stormwater storage plans proposing
an anticipated percolation loss as a substitute for volume storage
in the drainage calculations.
