[Adopted 6-6-1988 by Ord. No. 14-1988]
This article shall be known and may be cited
as the "Stormwater Management” article.
It is hereby determined that the lakes and waterways
within the City of Pleasantville of Atlantic County are subject to
flooding; that development tends to accentuate such flooding by increasing
stormwater runoff, due to alteration of the hydrologic response of
the watershed in changing from the undeveloped to the developed condition;
that such increased flooding produced by development of real property
contributes increased quantities of waterborne pollutants and tends
to increase channel erosion; that such increased flooding, increased
erosion and increased pollution constitutes deterioration of the water
resources of the City of Pleasantville, the county and the state;
and that such increase in flooding, increased erosion and increased
pollution can be controlled to some extent by the regulation of stormwater
runoff from such development. It is determined that it is in the public
interest to regulate the development of real property and to establish
standards to regulate the additional discharge of stormwater runoff
from such developments as provided in this article.
The criteria within this article are applicable
to all site and subdivision plans that require approval by the Municipal
Planning or Zoning Boards.[1]
[1]
Editor's Note: See Arts. XII, XIV and XV of
Chapter 290, Zoning and Land Use.
In order to protect, maintain and enhance both
the immediate and long-term health and general welfare of its citizens,
Pleasantville established the following goals and objectives for stormwater
control:
A.
To ensure that stormwater runoff after development
of a site will approximate the same rate of flow and timing of stormwater
runoff that would have occurred under predevelopment conditions.
B.
To maintain the adequacy of existing and proposed
culverts and bridges, dams and other conveyance structures.
C.
To minimize, to the greatest extent possible, the
transport of pollutants to receiving waters necessary for the preservation
of the chemical, physical and biological integrity of those waters.
D.
To minimize erosion and sedimentation from any development
or construction project.
A.
Burden of proof. Whenever an applicant seeks a municipal
approval of a development to which this article is applicable from
any board or official of the municipality, that applicant shall be
required to demonstrate that his project meets the standards set forth
in this article.
B.
Submission materials due. The applicant shall submit materials, as required by § 251-6 hereof, to the municipal board or official from which he seeks municipal approval prior to or at the same time he submits his application for municipal approval.
C.
Review of project. The applicant's project shall be
reviewed by the municipal board or official from which he seeks his
municipal approval. That municipal board or official shall consult
with the Municipal Engineer to determine if the project meets the
standards set forth in this article.
D.
Time for decision. The municipal board or official
shall promptly determine if the project meets the standards set forth
in this article. The time for that determination should be the time
permitted to review and act on the applicant's application for a municipal
approval.
E.
Failure to comply. Failure of the applicant to demonstrate
that the project meets the standards set forth in this article is
reason to deny the applicant's underlying application for a municipal
approval.
The following submissions shall be required
for a proposed project under review:
A.
Topographic base map. A topographic base map of the
site extending 200 feet beyond the limits of the proposed development
at a scale of one inch equals 200 feet shall display two-foot contour
intervals; existing surface water drainage; marsh lands; outlines
of woodland cover; existing, natural and man-made features; roads;
utilities; and bearings and distances of property lines.
B.
Vicinity map. Preparation of a map at the scale of
one inch equals 400 feet will reflect the site of the proposed development,
access to the site and surface date reflected from United States Geological
Survey Quads and Soils Maps.
C.
Environmental site analysis. A written and graphic
description of the site shall include existing soil conditions, slope
factors, wetlands, vegetation and animal life. Particular attention
should be given to unique features of the site.
D.
Water detention facilities map. The following information
shall be illustrated on a map of the same scale as the topographic
base map:
(1)
The total area to be impervious or built-upon, the
estimated land area to be occupied by water-retention or -detention
facilities and the type of vegetation thereon, and details of the
proposed plan to control and dispose of surface water.
(2)
Details of all water-retention or -detention plans,
during and after construction, including discharge provisions, discharge
capacity and spillway provisions, where applicable.
Each proposed project not exempted from the
operation of this article shall meet the following storm drainage
standards:
A.
General standards. The project plans submitted shall
demonstrate careful consideration of the general and specific concerns,
values and standards of the Municipal Master Plan and applicable county,
regional and state storm drainage control programs and any County
Mosquito Commission control standards and shall be based on environmentally
sound site planning, engineering and architectural techniques.
B.
Alternatives to detention basins.
(1)
Basin requirements may also be satisfied the following
ways: Tanks, infiltration pits, dry wells or gravel layers underneath
paving may be used for the purpose, with appropriate consideration
for length of life and feasibility of continued maintenance.
(2)
Nonstructural management practices, such as cluster
land use development, open space acquisition, stream encroachment
and flood hazard controls should be coordinated with detention requirements.
Changes in land use can often reduce the scope and cost of detention
provisions required by means of appropriate changes in runoff coefficients.
C.
Specific standards.
(1)
Detention basins.
(a)
A detention facility must accommodate the volume
of site runoff generated from a two-year, five-year, ten-year and
twenty-five-year twenty-four-hour storm considered individually (in
each case, a Type III rainfall as defined in Soil Conservation Service
Publications, Technical Release No. 55). Runoff greater than that
occurring from a twenty-five-year twenty-four-hour storm will be passed
over an emergency spillway. Detention will be provided such that,
after development, neither the peak rate of flow from the site nor
the total flow during the hour of maximum release will exceed the
corresponding flows which would have been created by a similar storm
prior to development.
(b)
The water quality design storm for dry detention
basins shall be defined as a one-year frequency Soil Conservation
Service Type III twenty-four-hour storm or a one-and-one-fourth-inch
two-hour rainfall. The outlet from the detention facility must require
that the runoff from a settleability design storm be retained such
that not more than 90% will be evacuated prior to 36 hours for all
nonresidential projects or 18 hours for all residential projects.
The retention time shall begin at the time of peak storage. Retention
will not be required in any case to an extent which would reduce the
outlet size to a diameter of three inches or less.
(c)
Multiple level outlets or other fully automatic
outlets shall be designed so that discharge rates from the developed
condition will not exceed the predevelopment runoff rate for a two-
, five- , ten- or twenty-five-year storm considered individually.
Outlet waters shall be discharged from the development at such locations
and velocities as not to cause additional erosion.
(d)
Outlets from detention facilities shall be designed
to function without manual, electric or mechanical controls.
(e)
In many instances, the provisions of separate
detention facilities for a number of single sites may be more expensive
and difficult to maintain than provisions of joint facilities for
a number of sites. In such cases, the municipality will be willing
to consider provisions of joint detention facilities which will fulfill
the requirements of this regulation. In such cases, a properly planned
staged program of detention facilities may be approved by the municipality
in which compliance with some requirements may be postponed at early
stages while preliminary phases are being undertaken and construction
funds accumulated.
(f)
If detention basins are provided through which
water passes at times other than following rainfall, the Municipal
Engineer should be consulted concerning design criteria. It will be
necessary for detention requirements to be met, despite the necessity
of passing certain low flows. This applies to all on-line detention
basins.
(g)
Soil borings must be made at least five feet
below the lowest invert of the basin bottom. Two soil borings will
be required per facility.
(h)
Where the project consists of two phases, (a)
new construction which required provisions of storm drainage under
the terms of this article and (b) repair or rehabilitation of structures
and surfaces which does not result in increasing the extent of impervious
areas or in rendering existing surfaces less pervious, the detention
requirements may be computed on the basis of Phase (a) exclusively.
(i)
Soil within the recharge system shall be protected
with filter fabric during construction; then, when site construction
is complete, the filter fabric will be removed and basin soils stabilized.
(j)
The location of a detention facility shall be
in an area with seasonal high water a minimum of 1.5 feet below the
lowest invert elevation of the facility.
(k)
A low flow channel shall be incorporated into
the detention basin to prevent broad area ponding.
(2)
Stabilized access 20 feet wide is to be provided to
the detention facility capable of supporting maintenance vehicles.
(3)
Retention-infiltration basin.
(a)
A retention basin system must accommodate stormwater
runoff so that the minimum rate of percolation of the soil is 15 minutes
per inch, which allows infiltration of 36 inches of runoff over a
three-day period from the basin.
(b)
One soil boring shall be required for each 1,000
square feet of all retention stormwater facilities. All borings must
extend 10 feet below the lowest invert elevation of the proposed stormwater
facility.
(c)
The location of a retention facility shall be
in an area with seasonal high water a minimum of two feet below the
lowest invert elevation of the facility. Furthermore, the bottom of
any proposed basin shall be at least five feet above any impervious
soil formations found in the soil logs; otherwise, the impervious
layer shall be penetrated at required intervals.
(d)
Sediment traps must be located such that all
inflowing stormwater be treated before entering any subsurface recharge
system.
(e)
Soil within the recharge system shall be protected
with filter fabric during construction; then, when site construction
is complete, the filter fabric shall be removed and basin soils stabilized.
(f)
A low flow channel shall be incorporated into
the retention basin to prevent broad area ponding.
(g)
Stabilized access 20 feet wide is to be provided
to the retention facility capable of supporting maintenance vehicles.
(h)
The retention of site runoff as required by
this article will result in the accumulation of sediment, including
particulate, silt and debris. Provision must be made for periodic
removal of accumulated solid materials, such that the basin continues
to operate as designed.
(i)
Infiltration practices, such as dry wells, infiltration
basins, infiltration trenches, buffer strips, etc., may be used to
satisfy this requirement, provided that they produce zero runoff from
the water quality design storm and allow for complete infiltration
within 36 hours.
(4)
Detention/retention facilities in flood hazard areas.
(a)
Whenever practicable, developments and their
stormwater facility basins should be beyond the extent of Zone A5
flood hazard boundary. When this is not possible and facility basins
are located partially or wholly within Zone A5 (as defined by New
Jersey Division of Water Resources, Bureau of Flood Plain Management),
some storm conditions will make the facility ineffective at providing
retention of site runoff. This will happen if the stream is already
overflowing its banks and the basin, causing the basin to be filled
prior to the time it is needed for containment of runoff. In such
cases, the standards established in these regulations will be modified
in order to give only partial credit to detention capacities located
within the A5 Zone. The credit will vary in ratio intended to reflect
the probability that storage will be available at the time a storm
occurs at the site.
(b)
Stormwater runoff storage parameters shall be
based upon the location and elevation of said facility. If a facility
is located on the edge or within the base flood elevation (A5 Zone),
the following criteria shall be used to determine effective storage:
[1]
When the bottom of the stormwater facility is
less than two feet below the base flood elevation, a storage volume
of 2 1/2 times the calculated site runoff storage volume must
be accommodated by the basin.
[2]
When the bottom of the stormwater facility is
between two feet and four feet below base flood elevation, a storage
volume of 10 times the calculated site runoff storage volume must
be provided by the basin.
[3]
When the bottom of said facility is four feet
or more below of the base flood elevation, a storage volume of 10
times the calculated site runoff storage volume must be provided by
the basin.
(c)
As an alternative approach to the above criteria,
if the developer can demonstrate that the detention provided would
be effective during runoff from the twenty-five-year twenty-four-hour
Type III storm, peaking simultaneously at the site and on the flood
hazard area, his plan will be accepted as complying with provisions
in the above set criteria.
(5)
Landscaping. All detention and retention-infiltration
basins shall be landscaped in the following manner:
(6)
Basin design. Design of both detention and retention-infiltration
basin will be the same except for outlet design for detention basins.
(a)
Side slopes of all basins shall not exceed three
to one.
(b)
All basins must maximize the distance between
inflow and outflow.
(c)
At inflow point to basins, energy dissipaters
should be incorporated to reduce the velocity of inflowing waters.
(d)
Design of facility should be based upon peak
rates of runoff for the entire drainage area upstream from the parcel
in question and design release rates computed on the basis of preexisting
conditions for the entire watershed.
A.
Detention facilities. For the purpose of determining
the total quantity of runoff prior to and following development, the
applicant shall utilize the Soil Conservation Service's Technical
Release No. 55 (TR-55). This methodology shall serve as the basis
for determining total storage capacity required subject to the guidelines
identified in previous sections of this report and will also serve
as the basis for determining release rates from the two- , five- ,
ten- and twenty-five-year storms.
B.
Calculations shall be computed on the basis of all
areas upstream of the parcel(s) in question. Peak rates of runoff
shall be computed for the entire area and design release rates computed
on the basis of preexisting conditions for the entire watershed.
C.
Maximum curve number values suitable for use in computing
runoff values for on-site undeveloped conditions are as follows:
|
Hydrologic
Soil Group
|
Curve Number
Value
| |
|---|---|---|
|
A
|
25
| |
|
B
|
55
| |
|
C
|
70
| |
|
D
|
77
|
D.
Rainfall values for each of the storms used in designing
stormwater facilities include (Type III rainfall distribution):
|
Storm Event
|
Total Rainfall (P)
(inches)
| |
|---|---|---|
|
2-year
|
3.5
| |
|
5-year
|
4.5
| |
|
10-year
|
5.6
| |
|
25-year
|
6.0
|
E.
The applicant must identify:
(1)
The peak rate of runoff, making adjustments as required
for percent of impervious cover, alterations of hydraulic length and
percentage of watershed as wetland as described in TR-55 and supplemented
by notes provided by the Soil Conservation Service. Either the tabular
method described in TR-55 or the charts contained in Appendix D of
TR-55 shall be used.
(2)
Total quantity of runoff utilizing the tabular hydrographic
data contained in TR-55. Total quantities of runoff shall be estimated
prior to and after development by calculating total area under the
hydrograph utilizing hydographic coefficients contained in TR-55.
(3)
The relative timing of the peak rate of discharge
following onset of a storm, which shall be identified within the stormwater
calculations.
F.
Methods and standards.
(1)
For storm sewer design, the rational method may be
utilized for calculating runoff quantities subject to the following
criteria: Design requirements for storm sewers shall be the ten-year
storm. Runoff generated by storms of greater intensity (up to and
including the twenty-five-year storm) shall be directed towards detention
basins or alternative stormwater facilities on the site.
(2)
Rainfall intensity (I) shall be computed as a function
of time of concentration by generally accepted procedures found in
Seeyles algebraic equations, Soil Conservation Service Engineering
Field Manual, etc.
(3)
Area (A) shall include all off-site acreage draining
onto or through the site.
(4)
The coefficient of runoff (C) shall not be less than
the values stated below unless well documented and approved by the
Municipal Engineer:
|
Surface
|
Minimum C
| |
|---|---|---|
|
Structures and pavements
|
0.90
| |
|
Cultivated dense or clay soils
|
0.30
| |
|
Cultivated sand or loam soils
|
0.25
| |
|
Meadows and rural areas
|
0.20
| |
|
Heavily wooded areas
|
0.15
|
(5)
Overall drainage runoff factors will not, in general,
be less than the following:
|
Proposed Development
|
Minimum C
| |
|---|---|---|
|
Site plans (to the limits of improvements)
|
0.70
| |
|
1/4-acre residential
|
0.50
| |
|
1/2-acre residential
|
0.40
| |
|
1-acre residential
|
0.30
|
(6)
The above tables are intended as minimum design standards.
They are not mandated design criteria.
(7)
Hydraulics will be computed using Manning's equation
or generally accepted nomographs for pipe flow. Pipe may be reinforced
concrete, corrugated metal or other material approved by the Municipal
Engineer.
(8)
Minimum friction factors (n) are listed below:
|
Pipe
|
n
| |
|---|---|---|
|
Corrugated aluminum and annular helical
| ||
|
15 to 27 inches
|
0.022 to 0.016
| |
|
30 to 42 inches
|
0.023 to 0.019
| |
|
42 inches and greater
|
0.024 to 0.022
| |
|
Concrete cast iron
|
0.013
| |
|
With paved invert
|
Subtract 0.003
|
(9)
Minimum pipe diameter shall be 15 inches. Maximum
distances between manholes or inlets shall be 500 feet.
(10)
Pipe rim elevations shall be matched in all manholes
and inlets. In general, a cover of one diameter shall be maintained
over the drainage pipe. If this is not possible, trench conditions
must be designed and detailed to ensure at least 85% relative compaction.
(11)
Inlets shall be specified with cast curb inlets attached.
Inlets shall be depressed one to two inches to increase capacities
on steep grades (6% or more).
(12)
Design velocities shall be at least two feet per second
and no more than 10 feet per second.
G.
Designed structures. All drainage structures, including
manholes, inlets, headwalls and sections and box culverts, shall conform
to the current details of the New Jersey Department of Transportation.
Unless approved otherwise by the Planning Board Engineer, all curb
inlets shall be standard Type B with curb piece heights equal to the
exposed curb face of the adjacent curb, plus two inches. All lawn
inlets shall be standard Type E. When the pipe size is such as to
require a larger structure, standard Type B1 or B2, E1 and E2 shall
be used. If still larger sizes are required, they shall be specifically
detailed using standard frames and grates.
H.
Dished gutters on local streets shall be permitted
only at T intersections involving local streets. Dished gutters shall
not be permitted on arterial or collector streets.
I.
Storm drainpipes running longitudinally along streets
shall not be located under curbing.
J.
Storm drainpipes shall be reinforced concrete, corrugated
aluminum pipe, pipe arch or helical corrugated pipe and shall be of
the size specified and laid to the exact lines and grades approved
by the Planning Board Engineer. All pipe shall support AASHTO HS-20
loading per the pipe manufacturer.
K.
For both major and minor development, blocks and lots
shall be graded to secure proper drainage away from all buildings,
to prevent the collection of stormwater in pools and to avoid concentration
of stormwater from each lot to adjacent lots.
Operation and maintenance of a stormwater management
facility includes periodic removal and disposal of accumulated material
and debris.
A.
Responsibility for operation and maintenance of the
facility lies upon the owner or owners of the property, unless assumed
by a governmental agency or where portions of the land are sold and
legally binding arrangements shall be made to the successor or new
owner in title.
B.
A schedule of maintenance shall be required on an
annual basis and shall be submitted to the Municipal Engineer and
Construction Official. In cases where maintenance or repair is neglected,
the municipality has the authority to perform the work and to backcharge
the owner.
C.
Prior to obtaining preliminary approval, the applicant
shall describe in detail the mechanisms for maintenance, including
but not limited to:
(1)
Types and quantities of equipment necessary for maintenance.
(2)
The methodology for maintaining all stormwater facilities
on-site.
(3)
The body responsible for the maintenance activity.
Where property is subdivided and sold separately, a homeowners' association
or similar permanent entity should be established as the responsible
entity, absent an agreement by government agency to assume responsibility.
(4)
The lifetime of the stormwater facility.
(5)
Itemized costs associated with all maintenance items
and foreseeable costs associated with repair of a system which fails.
D.
Prior to receiving final approval, the applicant shall
enter into a formal agreement with the municipality specifying both
maintenance bonds, maintenance responsibilities and maintenance activities.
This agreement shall be in a form satisfactory to the Municipal Attorney
and may include, but not necessarily, guaranties, deed restrictions,
covenants and bonds.
E.
In the event that the detention facility becomes a
danger to public safety or health or if it is in need of maintenance,
the municipality shall notify in writing the responsible party. From
the notice, the responsible person shall have 14 days to effect such
maintenance and repair of the facility in a manner that is approved
by the Municipal Engineer or his designee. If the responsible person
fails or refuses to perform such maintenance and repair, the municipality
may immediately proceed to do so and shall bill the cost thereof to
the responsible party.
Upon final approval of a stormwater management
facility:
A.
A reproducible Mylar as-built construction plan must
be submitted to the Municipal Engineer for documentation of final
design.
B.
As-built material test results have to be supplied
to the Municipal Engineer from a certified laboratory within two weeks
after facility installation and prior to performance bond release.
C.
When excavated and completed, the design engineer
shall certify in writing to the municipality that the stormwater facility
will operate as intended in the design phase, taking into consideration
all soil and water conditions encountered during construction.
If no fee is due to the municipality as a result
of the applicant's underlying application for a municipal approval
and if the application does not require the Planning Board or Zoning
Board approval process, there shall be due to the municipality at
the time of submission of materials in support of this application
a fee as follows:
[Added 2-17-1999 by Ord. No. 6-1999]
Any person who violates the provisions of this
article shall, upon conviction, be subject to a fine not of not less
than $100 nor more than $1,000, imprisonment for a term not exceeding
90 days and/or a period of community service not exceeding 90 days.
