B.
General criteria for residential subdivisions. The number of home
sites used to determine the appropriate width of traffic lanes and
sidewalks/bike paths shall be based upon the number of potential home
sites serviced by the proposed road.
[Amended 10-17-2022]
Local Street
|
Secondary Street
|
Sidewalk
(on one side)
| ||
---|---|---|---|---|
Right-of-way
|
50 feet
|
60 feet
| ||
Traffic lanes
| ||||
1 to 10 home sites
|
2 10-foot lanes
|
2 12-foot lanes
|
Not required
| |
11 to 20 home sites
|
2 10-foot lanes
|
2 12-foot lanes
|
Required
| |
21 to 30 home sites
|
2 11-foot lanes
|
2 12-foot lanes
|
Required
| |
Over 30 home sites
|
2 12-foot lanes
|
2 12-foot lanes
|
Required
| |
Paved shoulders
|
None
|
2 6-foot shoulders
| ||
Park strips (minimum)
|
2 5-foot strips
|
2 6-foot strips
| ||
Sidewalks/Bike path
|
1 6-foot path
|
1 8-foot path
| ||
Utility strips (at sides of pavement)
|
2 1-foot strips
|
2 1-foot strips
| ||
Maximum gradient
|
8% to 10%
|
8% to 10%
| ||
Minimum horizontal center line radius
|
200 feet
|
400 feet
|
Notes:
| |
a.
|
Greater width may be required by the Board where necessary to
meet present or future traffic demands.
|
b.
|
Minimum gradient of any street shall be one foot in 100 feet.
|
c.
|
Efforts shall be made to minimize the gradient of street by
locating streets so that they follow contours rather than crossing
contours. The gradient shall never exceed 10%.
|
d.
|
Sidewalks and/or bicycle paths and curbs will be required only
in areas of the Town where the Planning Board determines them to be
necessary for public safety. At the discretion of the Planning Board,
bike paths may be created by delineating a special lane on a paved
way. The center line grade of the proposed road at any point shall
be not more than five feet above or below the existing center line
grade.
|
e.
|
Cut or fill side slopes shall not be steeper than 3:1.
|
f.
|
All above-grade features, such as hydrants, utility poles, etc.,
shall be confined to the utility strip adjacent to the property line
and are not to be placed in the park or green strip, no greater than
40 feet on center of both sides of the street.
|
g.
|
The number of curb cuts into the streets should be minimized
by the use of common driveways serving more than one lot. Such common
driveways shall have at least a ten-foot width of traveled way with
suitable additional spaces provided for vehicles to be parked on each
lot without blocking the common driveway.
|
h.
|
All utilities shall be underground. Cable TV shall be included.
|
i.
|
A one-hundred-foot-long leveling area shall be provided at all
intersections. The leveling area will have a maximum slope of 3%.
|
j.
|
Guard rails shall be installed where slopes from the right-of-way
exceed 1:4 and the slope exceeds five feet in height, or where required
by the Board to protect vehicles from obstructions or to maintain
public safety.
|
k.
|
Where changes in roadway grade exceed 1%, vertical curves shall
be provided.
|
A.
All streets in the subdivision shall be designed so that, in the
opinion of the Board, they will provide safe vehicular travel.
B.
The proposed streets shall conform to the Master or Study Plan of
the Town adopted in whole or in part by the Board.
C.
All dead-end streets shall have either:
[Amended 10-17-2022]
D.
Street jogs with center line offsets of less than 125 feet shall
be avoided.
E.
Curves at intersecting streets shall have a tangent distance of not
less than 20 feet.
F.
All reverse curves on secondary streets shall have a minimum tangent
between curves of 100 feet.
G.
Streets shall be laid out so as to intersect as nearly as possible
at right angles. No street shall intersect any other street at less
than 60°.
[Amended 10-17-2022]
H.
Property lines at street intersections shall be rounded to cut back
to provide for a curb radius of not less than 20 feet.
I.
All roads shall be built such that the bottom of the gravel base
lies above the probable maximum high groundwater.
J.
Roads not yet released by the Planning Board from performance guarantee
shall be maintained to standards acceptable to the Planning Board.
Potholes in these roads must be repaired within two months of their
report to the Planning Board (from April 1 to November 1).
K.
No land may be stripped of all vegetation and left as bare soil without
approved erosion control.
L.
A twenty-five-foot no-disturbance vegetation buffer shall be maintained
around wetlands, streams, ponds and vernal pools.
M.
No dead-end street shall exceed 500 feet in length to the center
of the cul-de-sac or hammerhead.
[Amended 10-17-2022]
N.
Center line offsets for intersecting streets shall not be less than
200 feet.
O.
In all cases, the center line of the paved surface shall be coincidental
with the center line of the right-of-way, unless specifically excepted
by the Board.
P.
Sight distance requirements at intersections shall conform to the
requirements of the procedures utilizing a 3.5-foot height observer
and a 0.5-foot object.
Q.
The roadway pavement shall consist of a four-inch thickness, after
compaction, prepared and installed in conformity with Section 460
of the Massachusetts Department of Transportation Standard Specifications
(hereafter referred to as MassDOT Standard Specifications). The pavement
shall be spread and rolled in two courses: a 2.5-inch thickness standard
base course and a 1.5-inch thickness top course, in conformity with
the Specifications aforementioned.
A.
Easements for utilities across lots shall be provided where necessary
but, where practicable, shall be centered along rear or side lot lines
and shall be at least 25 feet wide.
B.
Where a subdivision is traversed by a watercourse, drainage way,
channel or stream, easements as required to meet the Conservation
Commission's order of conditions shall be provided.
C.
See § 300-3.3C(6), Common land and ways," for easements covering common driveways.
D.
A separate, numbered lot, upon which a detention/retention pond(s)
is located and all easements on the other lots which are pertinent
to said detention/retention pond(s) themselves, shall be held by a
legal entity to be formed by the applicant-owner for the benefit of
owners of lots within the subdivision. The documents describing the
above legal entity, which shall hold the lots and easements, shall
be reviewed by the Town Counsel and shall be subject to his or her
approval. The applicant-owner shall execute such legal documents as
are required to effectuate the conveyances above described. Maintenance
of the detention/retention pond(s), including periodic dredging, shall
be a responsibility incorporated in the above-described document.
A.
Before approval of a plan, the Board shall also, in proper cases
and in conformance with the most recently adopted Master Plan and
Open Space Plan, require the plan to show a park or parks suitably
located for recreational purposes. The park or parks shall not be
unreasonable in area in relation to the land being subdivided and
to the prospective uses of the land. The park shall be located on
a separate lot under common ownership and shall be labeled as nonbuildable.
B.
No change shall be made in the contour of the land that adversely
affects the land abutting the proposed subdivision.
C.
All possible steps shall be taken to preserve all natural features,
such as, but not limited to, desirable and mature trees and shrubs,
watercourses, scenic views and vistas, open space, historic spots,
the habitat of species listed as rare, endangered, or of special concern
by the Massachusetts Department of Fisheries, Wildlife and Environmental
Law Enforcement, Natural Heritage and Endangered Species Program,
and similar community assets, which, if preserved, will add attractiveness
and value to the subdivision. It is the intent of the Planning Board
with these provisions to preserve any especially large or unusual
species of plants. Property within any overlay district must meet
the requirements of the district.
[1]
Editor's Note: Former § 300-4.5, Floodplain protection,
was repealed as part of the recodification of the Town's General and
Zoning Bylaws adopted 10-23-2017 STM by Art. S7. The specific changes
made are noted in a document entitled "Town of Marion Final Draft,"
dated August 16, 2017, which document is on file in the Town offices.
A.
General.
(1)
Management of stormwater runoff from all developments reviewed
by the Marion Planning Board shall meet the standards and design criteria
contained in this section for both flood control and non-point source
pollution reduction. All assumptions, methodologies, and procedures
used to design the stormwater management system components shall accompany
all site plan review and subdivision of land applications to the Planning
Board.
(2)
Strict adherence to these standards may be waived by the Planning
Board upon a clear demonstration by the proponent that full compliance
with any specific standard would not serve the public interest or
would not be practical due to physical site constraints.
(3)
All applicable standards of the Department of Environmental
Protection (DEP) Stormwater Management Policy, dated March, 1997,
amended January 2008, and all subsequent amendments thereto, and the
(DEP) Hydrology Handbook for Conservation Commissioners dated March,
2002, as amended from time to time, shall apply as minimum standards
to all plan submittals, except where this section requires more stringent
standards.
(4)
The applicant shall be responsible for compliance with the Marion
Board of Health and Conservation Commission requirements governing
the pertinent aspects of the stormwater management system.
(5)
Prior to the release of any portion of the performance guarantee,
the stormwater management system must be substantially complete, stabilized,
and operational. The functionality of the system shall be evaluated
by the consulting engineer and the Department of Public Works Superintendent.
The applicant shall submit an as-built plan of the constructed stormwater
management system prepared by a registered land surveyor and certified
by a registered professional engineer. If the system is found to be
inadequate by virtue of physical evidence of operational failure even
though it was built as called for in the definitive plan, it shall
be corrected before the performance guarantee is released. Examples
of inadequacy shall include errors in the infiltrative capacity, errors
in the maximum groundwater elevation, failure to properly define or
construct flow paths, or erosive discharges from the basins.
[Amended 10-17-2022]
B.
Performance standards.
(1)
All design and construction shall be done in a manner such that
the post-development stormwater runoff will not exacerbate or create
flooding conditions, or alter surface water flow paths, resulting
in impacts to the receiving wetland resource area or any adjacent
properties to the site for the two-, twenty-five-, and one-hundred-year
twenty-four-hour storm events. The pre-development standard shall
be those conditions prevailing prior to abandoned projects or previously
disturbed terrain.
(2)
The stormwater management systems shall be designed to attenuate
the peak rate of the runoff for the two-, twenty-five-, and one-hundred-year
twenty-four-hour storm events at or below the pre-development levels.
Additional stormwater volume attenuation in excess of the required
recharge volume under the DEP Stormwater Policy for these storm events
may also be required for any stormwater discharges into floodprone
areas, off-site culvert inlets, isolated topographic depressions,
adjacent properties, and any receiving wetland and/or water body which
may be sensitive to increases in runoff volume.
(3)
Stormwater management systems that may eventually be owned and
maintained by the Town of Marion shall be designed and constructed
to provide the required level of treatment at the least cost to the
Town.
[Amended 10-17-2022]
(4)
Stormwater management systems shall be designed and constructed
so that they do not negatively impact groundwater quality or elevations
adjacent to or downgradient of the system area. Upon review of the
specific site conditions, the Planning Board may require a groundwater
mounding analysis based on the Hantush Method and a groundwater water
quality evaluation to determine the potential impacts to any adjacent
sensitive receptors (i.e., drinking water supplies and basements of
existing dwellings).
(5)
Stormwater management systems shall be designed and constructed
so that they do not represent safety hazards or nuisances to public
health as determined by the Planning Board in consultation with the
Board of Health.
(6)
Stormwater management systems shall be designed and constructed
so that they do not visually detract from the neighborhood. A landscape
design shall be prepared that provides appropriate screening from
the adjacent properties and roadways, while providing the degree of
access necessary for O&M activities. Landscape plans shall be
submitted that appropriately address visibility issues through proper
placement, preservation of existing natural vegetation and supplemental
plantings where necessary. Rain garden BMPs or other LID BMPs are
encouraged.
[Amended 10-17-2022]
C.
Submittal requirements.
(1)
All site plan and definitive subdivision submittals shall be
accompanied by a stormwater management system report. At a minimum,
the report shall consist of the following:
(a)
Hydrologic calculations for the two-, twenty-five-, and one-hundred-year
twenty-four-hour storm events based on the TR-20/55 Methodology for
the pre- and post-developed conditions for the overall project as
well as specific calculations for the two-, twenty-five-, and one-hundred-year
twenty-four-hour storm events also based on the TR-20/55 Methodology
for each specific area subject to flooding, including but not limited
to isolated depressions, culvert inlets, and ponding areas for the
pre- and post-developed condition.
[Amended 10-17-2022]
(b)
Supporting water quality calculations, specific BMP sizing calculations,
and a stormwater management form stamped by a registered professional
engineer shall also be provided.
(c)
Discussion of the environmental and hydrological conditions of the site for the pre- and post-developed condition, as well as the proposed alterations of the site, all proposed components of the stormwater management system and low-impact development (LID) consistency summation outlined in Subsection D(8)(c).
(d)
Soil evaluation logs, permeability test results and predicted
maximum groundwater levels at each component of the stormwater management
system validated by an agent of the Board of Health and/or the Planning
Board. On-site permeability tests may be required to determine the
appropriate infiltration value from Table 2.3.3 of the DEP Stormwater
Management Policy. Rawls rates may also be used for the exfiltration
analysis.
[Amended 10-17-2022]
(e)
An operation and maintenance plan for the stormwater management
system. The plan shall include a maintenance schedule for each component
of the stormwater management system, an outline of responsible parties
and owners, and all pertinent agreements to be executed to insure
proper maintenance of the facilities.
(2)
Pre- and post-development watershed plans at a preferred scale
of one inch equals 40 feet shall be submitted with the stormwater
management system report and shall clearly depict the following information:
(a)
Pre-development watershed plan.
[1]
The location of all surface waters, wetland resource areas,
and all other state/federal jurisdictional resource areas on or within
100 feet adjacent to the site. The boundaries of all such resource
areas shall be verified to be accurate by the Marion Conservation
Commission.
[2]
The delineation of the one-hundred-year flood elevation as indicated
on the Federal Flood Insurance Rate (FIRM) maps. If FIRM maps do not
exist or if the one-hundred-year flood elevation of the water body
or watercourse is not indicated on the FEMA map, the elevation shall
be calculated, utilizing the U.S. Army Corps of Engineers' HEC floodwater
modeling methodology or the SCS TR-20.
[Amended 10-17-2022]
[3]
Existing topography at a two-foot contour interval within the
watershed study area. Areas with less than a 1.0% grade shall be shown
at a one-foot contour interval with existing spot grades.
[4]
Delineation of the existing watershed boundaries on the property,
inclusive of all off-site areas contributing runoff to the property.
[5]
Boundaries of existing surficial ground cover conditions within
the watershed study area in order to verify the runoff curve number
(Cn).
[6]
Prevailing soil types on the site and the hydrological soil
groups based on the most current Natural Resource Conservation Service
soils map. The provisional soil mapping at the NRCS office in Wareham
shall be used in place of the published 1967 Plymouth County mapping.
[7]
Flow paths, lengths, slopes, and design points for each watershed
with each segment of the flow path defined.
[Amended 10-17-2022]
[8]
Areas subject to flooding, including but not limited to isolated
topographic depressions, culvert inlets, and ponding areas with the
calculated one-hundred-year flood elevation associated with each area.
[9]
The location of any public or private water supplies on the
property or within 100 feet of the property location, including any
mapped Water Resource Protection Overlays (i.e., Zone II, IWPA.)
[10]
Location of soil test pits and groundwater elevations.
(b)
Post-development watershed plan.
[1]
Existing and proposed topography at a two-foot contour interval
within the watershed study area. Areas with less than a 1.0% grade
shall be shown at a one-foot contour interval with proposed spot grades.
[Amended 10-17-2022]
[2]
Delineation of the proposed watershed boundaries on the property,
inclusive of all off-site areas contributing runoff to the property.
[3]
Boundaries of proposed surficial ground cover conditions within
the watershed study area, including roadway areas, building footprints,
driveways, lawn/landscaped areas and areas to remain in their natural
condition in order to verify the runoff curve number (CN).
[Amended 10-17-2022]
[4]
Prevailing soil types on the site and the hydrological soil
groups based on the most current Natural Resource Conservation Service
soils map. The provisional soil mapping at the NRCS office in Wareham
shall be used in place of the published 1967 Plymouth County mapping.
[5]
Flow paths, lengths, slopes, and design points for each watershed
with each segment of the flow path defined.
[Amended 10-17-2022]
[6]
Areas subject to flooding, including but not limited to isolated
topographic depressions, culvert inlets, and ponding areas with the
calculated one-hundred-year flood elevation associated with each area
as a result of development in the watershed.
[7]
Location of soil test pits, permeability tests, and groundwater
elevations for each component of the proposed stormwater management
system.
[8]
The proposed development layout, including the locations of
roadways, parking areas, limits of land alteration, undisturbed areas,
state/federal jurisdictional wetlands, floodplains, drainage collection
systems and stormwater management facilities.
D.
Design criteria.
(1)
General.
(a)
The criteria presented herein are provided to assist the designer by identifying minimum requirements, general procedures to be followed as well as specifying any limitations regarding the types of systems to be allowed. The designer is responsible for ensuring that the design complies with the performance standards enumerated in Subsection B above as well as conformance with state and federal requirements and with accepted engineering practice.
(b)
All runoff from storms up to the one-hundred-year storm event
must flow through the stormwater management/treatment systems. Systems
for the proper conveyance of the predicted one-hundred-year storm
to the stormwater management/treatment systems shall be provided.
(2)
Location.
(a)
Stormwater management systems (exclusive of the conveyance system)
shall be located on a separate and segregated parcel specifically
designated for such use, to be conveyed to the Town should Town acceptance
of the subdivision roadway and infrastructure be contemplated. Provisions
for vehicular access shall be provided at the circumference of each
system. Components of the collection system such as drainage piping,
ditches, swales, and certain LID components etc. may be located within
access/utility easements. Provisions for vehicular access shall be
provided along the entire length of storm drain lines and swales within
all designated access/utility easements.
(b)
The following minimum setback requirements shall apply to all
stormwater management systems. Any of these setback distances may
be waived by the Board upon a clear finding that the proposed stormwater
management system will utilize the preferred LID structural stormwater
best management practices on a LID scale through decentralization
and dispersion.
(3)
Soil testing.
(a)
Soil testing to determine the maximum groundwater elevation
and soil profiles shall be performed by a Massachusetts approved Soil
Evaluator or Certified Soil Scientist and witnessed by the Board of
Health and/or an agent of the Planning Board. At the discretion of
the Board, soil permeability testing may be required if the initial
soil logs exhibit variable soil conditions and inconsistent groundwater
profiles.
[Amended 10-17-2022]
(b)
Investigations.
[1]
Subsurface investigations for infiltration practices are required
to define the suitability of soils for subsurface disposal of stormwater
runoff. These explorations are necessary to determine the textural
characteristics of the various soil strata, restricting layers, location
of the estimated seasonal high water table elevation and depth to
bedrock in the location of the proposed system.
[Amended 10-17-2022]
[2]
The soil investigation must include an identification of the
soil through examination of the soil profile in the location of the
proposed system. In addition, the following determinations must be
included in the investigation:
[a]
Soil textures, measurement of soil permeability
rates, soil hydrologic group, estimation of seasonal high water table
elevation by identifying soil gleying and mottling, and identification
of any restricting layer(s).
[b]
Acceptable testing methods to determine the soil
suitability for infiltration practices are the falling head permeameter
test (ASTM D5126-90) or the double ring infiltrometer (ASTM D3385-03/D5093-02).
Soil test pits shall be excavated to a depth no less than five feet
below the design bottom of the system or to the static water level,
to inspect and describe the soil profile. A minimum of one inspection
pit must be dug per 5,000 square feet of system bottom area and must
be located within the perimeter of the system.
(4)
Calculations.
(a)
Rainfall data shall be as determined from the National Oceanic
and Atmospheric Administration (NOAA) Atlas 14 dated September 30,
2015, providing precipitation data for New England and New York, or
the document with the most recent date.
(b)
The use of the Rational Method for volume-related calculations
is not permitted.
(c)
In areas where the actual on-the-ground soil evaluations exhibit
subsurface conditions inconsistent with the NRCS mapping, or in cases
where the site has been extensively reworked, the hydrologic soil
group (HSG) curve number (CN) values utilized in the TR-20 calculations
should be adjusted to reflect the actual on-the-ground cover conditions
based on the determination by the Massachusetts-approved Soil Evaluator
or Certified Soil Scientist.
[Amended 10-17-2022]
(d)
The analysis points for the hydrologic study shall be at the
edge of the wetland resource area boundary, adjacent downgradient
property line, existing storm drain system, or other sensitive receptors
such as adjacent agricultural uses. For each pre-development analysis
point there shall be a corresponding post-development point.
[Amended 10-17-2022]
(e)
For all infiltration facilities where the bottom is proposed
to be within two feet zero inches of the Estimated Seasonal Highwater
Table, a groundwater mounding analysis based on the Hantush method
for the required design storms shall be prepared by a professional
engineer or hydrologist. The applicant shall assess the potential
effects from the subsurface disposal of stormwater on adjacent road
surfaces, private wells, building foundations, embankments and any
other site features that may be sensitive to groundwater flow.
[Amended 10-17-2022]
(f)
The sediment forebay volume below the elevation of the spillway
to the detention/retention stage cannot be utilized as available flood
storage volume or recharge volume for purposes of sizing the detention/retention
basin.
(5)
Treatment required.
(a)
The discharge of untreated stormwater runoff from the developed
areas of the property is prohibited.
(b)
Stormwater management systems shall be designed to treat the
first flush volume of the entire project site at full build out and
shall achieve an eighty-percent TSS removal rate of the total suspended
solids at the point of discharge. The first flush volume is a function
of the initial 1.25 inches of stormwater runoff from impervious surfaces.
The first flush treatment volume in cubic feet (Vt) is determined by the following formula:
Vt = (1.25/12 inches) (Rv)(Site Area in Square Feet)
|
Where Rv = 0.05 + 0.009(I) and I = the
% impervious area. "Impervious area" is defined as any man-made cover
that is not vegetated.
|
(c)
Any development in the Sippican Harbor and Wings Cove watershed
areas shall incorporate a physical treatment processes to remove nitrogen
at a minimum efficiency rate of 40%. Development in the Mary's Pond
watershed shall incorporate phosphorus removal at a minimum design
rate of 50%.
(6)
Aboveground basins.
(a)
All water quality basins/ponds shall have a sediment forebay
consisting of a separate cell separated from the detention/retention
stage by a rock fill filter berm to allow lateral flow into the lower
stage. The top elevation of the filter berm shall be at or below the
elevation of the inlet piping.
(b)
A gravel access drive not less than 12 feet wide shall be provided
around the outer perimeter of all basins to allow for vehicular access.
(c)
The maximum depth of the sediment forebay shall be no greater
than two feet.
(d)
Where appropriate, the interior side slopes of all basins shall
be no greater than 4:1 but in no case less than 3:1. Exterior side
slopes of the embankment shall be no greater than 3:1.
(e)
The bottom elevation of the basin shall be no less than two
feet above the maximum groundwater table elevation or bedrock and
shall be at least one foot above the elevation of the receiving wetland.
(f)
The calculated peak water levels within the basin for all design
storms shall be no greater than three feet and shall be no less than
12 inches below the elevation of the containment berm.
(g)
The entire detention basin area shall be treated with a four-inch
layer of screened organic soil borrow conforming to Massachusetts
Department of Transportation (MassDOT) Standard Specifications M1.05.0.
The side slopes shall be seeded with an erosion seed mix conforming
to MassDOT Specifications M6.03.0. The basin bottom shall be seeded
with a New England erosion control/restoration mix as manufactured
by New England Wetland Plants, Inc., or approved equal, applied at
a rate of 35 pounds per acre and supplemented by landscape plantings.
Infiltration basins shall be treated with four-inch layer of screened
organic soil borrow conforming to Massachusetts Department of Transportation
(MassDOT) Specifications M1.07.0 and planted with a water-tolerant
grass seed mix.
[Amended 10-17-2022]
(h)
The maximum allowable ponding or storage time for infiltration
basins for design storms up to the twenty-five-year storm event is
48 hours. For the one-hundred-year storm event, the maximum drain
time shall be 72 hours.
(i)
The bottom elevation of the infiltration basin shall be no less
than two feet above the Estimated Seasonal Highwater Table or bedrock
and shall be at least one foot above the elevation of the receiving
wetland.
[Amended 10-17-2022]
(j)
Infiltration basins may be constructed in fill, providing that
a minimum four-foot layer of naturally occurring soil meeting the
infiltration requirements of this section is available below the bottom
of the basin and that the fill material is a clean granular fill conforming
to 310 CMR 15.255(3). Construction in fill shall mean any system where
fill is required to replace topsoil, subsoil, peat, or unsuitable
soil layers above the requisite four feet of naturally occurring soil.
(k)
Recharge structures shall be provided at the bottom of the infiltration
basin to ensure adequate recharge is provided under frozen ground
cover conditions.
(l)
All infiltration basins must be provided with an overflow mechanism
to a receiving wetland or water body. Access/Utility easements must
be provided along the designated overflow path to the receiving wetland
or water body. All infiltration basins must have an outlet structure
with an accessible valve to allow manual drainage of the basin in
an emergency condition, nonerosive flows at the outlets, inlet splash
pads and emergency spillway weirs. Outlet structures and all inlet
and outlet piping 18 inches or greater in diameter shall be fitted
with trash racks.
[Amended 10-17-2022]
(m)
Infiltration practices are limited to soils in Hydrologic Soil
Groups A, B and C only, as identified by the most recent NRCS Soil
Survey mapping. The provisional soil mapping at the NRCS office in
Wareham shall be used in place of the published 1967 Plymouth County
mapping. Dry wells for individual residential dwellings and small
LID technologies such as rain gardens, bioretention cells and infiltration
strips may be permitted in Hydrologic Soil Group C soils, providing
the minimum infiltration rate of 0.50 inch per hour can be achieved.
(n)
Detention and infiltration basins may not be located within
the VE Zone as depicted on the map entitled, "Flood Insurance Rate
Map, Town of Marion," which is in effect at the time of application.
(7)
Subsurface recharge systems.
(a)
Subsurface recharge systems may be used on subdivisions consisting
of five lots or less, commercial and industrial site developments.
All infiltration systems including aboveground basins and subsurface
recharge must be provided with a pretreatment system capable of removing
80% of the total suspended solids (TSS) loading from the contributing
watershed area. Subsurface recharge systems are not allowed on residential
subdivisions in excess of five lots or land uses with a high-potential
pollutant load as defined in the DEP Stormwater Management Policy.
(b)
Infiltration practices are limited to soils in Hydrologic Soil
Groups A, B and C only, as identified by the most recent NRCS Soil
Survey mapping. The provisional soil mapping at the NRCS office in
Wareham shall be used in place of the published 1967 Plymouth County
mapping. Dry wells for individual residential dwellings and small
LID technologies such as rain gardens, bioretention cells and infiltration
strips may be permitted in Hydrologic Soil Group C soils, providing
the minimum infiltration rate of 0.50 inch per hour can be achieved.
(c)
The bottom elevation of the subsurface recharge system shall
be no less than two feet above the Estimated Seasonal Highwater Table
elevation or bedrock.
[Amended 10-17-2022]
(d)
The maximum allowable ponding or storage time for recharge systems
for design storms up to the twenty-five-year storm event is 48 hours.
For the one-hundred-year storm event, the maximum drain time shall
be 72 hours.
(e)
Subsurface recharge systems may be constructed in fill, providing
that a minimum four-foot layer of naturally occurring soil meeting
the infiltration requirements of this section is available below the
bottom of the basin and that the fill material is a clean granular
fill conforming to 310 CMR 15.255(3). Construction in fill shall mean
any system where fill is required to replace topsoil, subsoil, peat,
or unsuitable soil layers above the requisite four feet of naturally
occurring soil.
(f)
Subsurface recharge systems located under paved parking areas
shall be designed to an H-20 vehicle loading.
(g)
The entire area of the proposed subsurface recharge system shall
be roped off during construction to prevent compaction of the underlying
soils by heavy equipment. The basin shall be excavated with light
earth-moving equipment to prevent compaction of soils beneath the
basin floor or side slopes. Light earth-moving equipment does not
include bulldozers or standard-size pay loaders, but may include Low
Ground Pressure Equipment (LGP).
[Amended 10-17-2022]
(h)
Proper soil erosion and sediment control methods must be used
during and after development of the site. Stormwater runoff shall
not be allowed into any infiltration basin or recharge structure until
the entire contributing watershed area has been stabilized with vegetation
and other soil erosion and sediment control techniques.
(i)
Under no circumstances shall any infiltration basin or subsurface
recharge system be utilized as temporary sediment traps or stormwater
management during construction.
(j)
Subsurface recharge systems shall consist of precast concrete
or HDPE galleys, or large-diameter perforated HDPE pipe. The systems
shall be encompassed with a 0.75-inch to 1.5-inch double-washed stone
conforming to 310 CMR 15.247(1) and wrapped in filter fabric. An individual
recharge system for each catch basin inlet or pair of inlets is preferred
over a single recharge facility serving multiple inlets. Direct connections
from the catch basin inlets to the recharge systems are not permitted.
Proprietary treatment systems may be considered in order to satisfy
the 80% TSS removal target prior to discharge into the subsurface
recharge system.
[Amended 10-17-2022]
(k)
For each line of subsurface galleys or trenches, a minimum of
two inspection manholes with cast iron frames and covers to grade
for access and maintenance shall be provided at opposite ends of each
line. The maximum length of each trench/galley line shall not exceed
50 feet. When multiple trench/galleys are used each row of trenches
or galleys shall be separated by a distance not less than three times
the effective width or depth, whichever is greater.
[Amended 10-17-2022]
(l)
Individual recharge systems shall be interconnected with an
overflow pipe to a downgradient outfall device to prevent flooding
of the roadway and adjacent properties in the event the design storm
is exceeded or hydraulic failure of the infiltration structure.
(8)
Low-impact development techniques.
(a)
Low-impact development (LID) techniques to manage stormwater
shall be considered for new construction and redevelopment of projects
for all commercial, industrial, and residential site development projects.
Designs that reduce impervious surfaces and employ decentralized stormwater
management systems that involve the use of small treatment and infiltration
devices and LID best management practices (LID-BMPs) throughout the
site in place of a centralized system of closed pipes and a single
large facility are preferred.
[Amended 10-17-2022]
(b)
Effective low-impact development includes the use of both nonstructural
and structural stormwater best management practices (LID-BMPs). The
use of these BMPs is governed by certain principles, objectives and
requirements. The maximum practical use of the following seven nonstructural
strategies shall be considered:
[1]
Protect areas that provide water quality benefits or areas particularly
susceptible to erosion and sediment loss.
[2]
Minimize impervious surfaces and break up or disconnect the
flow of runoff over impervious surfaces through the use of vegetative
filter strips and buffers.
[3]
Minimize the decrease in the pre-construction time of concentration.
[4]
Minimize land disturbance activities including clearing and
grading and preserve naturally vegetated areas.
[5]
Provide low-maintenance landscaping that promotes retention
and planting of native vegetation and minimizes the use of lawns,
fertilizers, and pesticides.
[6]
Provide vegetated open channel conveyance systems which discharge
into and through stable vegetated filter strip areas.
[7]
Provide preventative source controls.
(c)
The applicant shall prepare a low-impact development (LID) consistency
statement showing how the above strategies have been incorporated
into the developments design in the stormwater management report.
For each of the above strategies that were not able to be incorporated
into the design due to physical site constraints, engineering, environmental,
or safety reasons, the applicant must provide a basis for this contention.
(d)
Preferred structural stormwater best management practices such
as rain gardens, bioretention areas, sand filters, and infiltration
strips provide storage, infiltration, and treat runoff close to its
source. Other standard best management practices such as dry wells,
infiltration systems, surface and subsurface detention basins can
all be done at an LID scale by downsizing and addressing stormwater
runoff close to its source and dispersing these systems throughout
the development site.
(e)
Commercial and industrial site development projects shall provide
preventative source controls to prevent pollutants from being part
of the stormwater runoff. Source controls such as the prevention and
containment of spills and other harmful accumulations of pollutants
as well the management of trash and debris shall be incorporated into
all commercial and industrial site development plans.
(9)
Proprietary treatment devices.
(a)
A proprietary treatment device is a prefabricated stormwater
treatment structure utilizing settling, filtration, absorptive/adsorptive
materials, vortex separation, and/or other appropriate technology
to remove pollutants from stormwater runoff.
(b)
These devices are allowed for new construction and redevelopment
projects on privately owned commercial/industrial land development
sites. The operation and maintenance of these proprietary treatment
devices will be the obligation of the owner of the facility being
served. These devices may also be considered on real estate subdivisions
upon a clear finding by the Board that no other practical alternative
is available to achieve the water quality treatment goals of these
rules and regulations.
(c)
On-line devices must be fitted with an overflow bypass for storm
events exceeding the stormwater quality design storm.
(d)
The specified devices shall be furnished by a manufacturer regularly
engaged in such work and who has furnished similar installations in
the Commonwealth of Massachusetts and had them successful and continuous
operation for a minimum period of five years. Devices which have been
evaluated and assigned a TSS removal efficiency by the DEP through
the Massachusetts Strategic Envirotechnology Partnership (STEP) program
are approved for use in the Town of Marion. Other proprietary technologies
will be evaluated by the Board on a case-by-case basis in accordance
with the DEP Technical Guide for Compliance with the Massachusetts
Stormwater Management Standards Volume 2, Chapter 4.
(e)
Manufacturers' documentation on similar systems, including but
not limited to data on performance testing, service history, TSS removal
efficiency, sizing criteria, and operation/maintenance requirements
of the specified devices, shall be submitted to the Planning Board.
(f)
Approval of proprietary devices will be based on the following:
[1]
Optimal TSS removal efficiency.
[2]
Minimal operation and maintenance costs.
[3]
Compatibility with existing infrastructure, other BMP devices
and physical site constraints.
[4]
Frequency of maintenance and special handling or installation
techniques.
[5]
Special equipment required for maintenance and the capability
of the Department of Public Works to provide maintenance service.
[6]
Reliability of performance data and potential failure rates.
E.
General landscaping guidance.
(1)
All submittals shall be accompanied by a stormwater management
system landscaping plan prepared by a landscape architect registered
in the State of Massachusetts. At a minimum, the landscaping plan
shall consist of the following:
(a)
Plan views of each stormwater management system with detailed
planting locations identified by species, size, and count. The wetted
hydrologic zones within and around the basins should be identified
and noted on the plan views. The planting species should be selected
based on the frequency and depth of inundation within the hydrologic
zones.
[Amended 10-17-2022]
(b)
A detailed planting schedule table identifying the size and
type of species planted and individual plant counts. The planting
schedule shall identify the botanical and common name and spacing.
[Amended 10-17-2022]
(c)
Notation specifications describing the site preparation activities,
soil amendments, and procedures for plant installation. Specifications
should also address the type of materials (e.g., balled and burlap,
bare root, containerized); time of year of installations, sequence
of installation of type of plants; fertilization, stabilization seeding,
watering and general care.
(d)
Maintenance program consisting of inspection intervals, mulching
frequency, removal and replacement of dead and diseased vegetation,
watering schedule, repair and replacement of staking and wires, removal
and eradication of invasive species.
(e)
A two-year guarantee on all new plant material requiring replacement
of any dead plant material within this period is required.
[Added 10-17-2022]
(2)
Planting plan design considerations.
(a)
Use of native plant species is required. Invasive species as
defined by the Massachusetts Invasive Plant Advisory Group (MIPAG)
are prohibited for use. Existing natural vegetation is to be preserved
where possible and enhanced with native plant species. Plantings requiring
routine or intensive chemical applications are not permitted.
[Amended 10-17-2022]
(b)
Appropriate plantings should be selected based on the zone's
hydric tolerance. Planting locations should be random and consistent
with the surrounding native vegetation.
(c)
Trees, shrubs and/or any type of woody vegetation is not allowed
on basin embankments. Herbaceous embankment plantings should be limited
to 10 inches in height. Trees and shrubs should be planted at least
25 feet away from any perforated pipes and principal spillway structures.
Trees and shrubs known to have long taproots should not be planted
within the vicinity of any earth embankments or subsurface drainage
facilities.
(d)
Inflow and outflow channels and southern exposure areas of any
permanent pool areas should be shaded to reduce thermal warming.
(e)
Aesthetics and visual characteristics should be a prime consideration
in the landscaping plan. Desirable views should be framed and maintained
while unattractive views should be effectively screened from any adjacent
residences and roadways.
F.
Stormwater collection systems.
(1)
Design criteria.
(a)
The quantity of stormwater carried by storm drains shall be
determined by the Rational Method on the basis of a twenty-five-year-frequency
design storm. The inlet capacity and spacing for catch basins shall
be designed to limit the flow in the gutter during a twenty-five-year
design storm to a maximum of four feet in width as calculated utilizing
methodologies described in Drainage of Highway Pavements, Hydraulic
Engineering Circular No. 12, as published by the U.S. Department of
Transportation, Federal Highway Administration. In any event, water
shall not be allowed to run for more than 300 feet on paved surfaces.
Computations for drainage requirements shall be prepared by a registered
professional civil engineer and submitted with the drainage report
prepared for the project.
[Amended 10-17-2022]
(b)
Supporting data for the sizing of the storm drain collection
system shall include the following:
[1]
Subcatchment area plan(s) at a clear legible scale showing the
following information.
[Amended 10-17-2022]
[2]
Existing and proposed contour grading at the predicted full
build out of the subdivision.
[3]
Existing and proposed ground cover conditions.
[4]
Predicted flow paths and delineation of subcatchment areas to
each inlet.
[5]
Rational Method calculations based on the twenty-five-year storm
event and the one-hundred-year storm event where the collection system
is expected to convey the one-hundred-year storm flows to the receiving
stormwater management facility.
[6]
Time of concentration (Tc) worksheets based on TR-55 methodology.
[7]
Weighted average ground cover coefficient (C) calculations.
[8]
Inlet grate capacity calculations based on Hydraulic Engineering
Circular #12.
[9]
Rainfall intensity based on local rainfall/intensity/duration
data.
[Added 10-17-2022]
(c)
The system may make use of gutters, inlets, culverts, catch
basins, manholes, subsurface piping, surface channels, and open detention
basins. Leaching catch basins will not be permitted. The Board will
not approve any design or component which, in its opinion, does not
meet the standards of good engineering practice, will not function
without frequent maintenance, or is unsuited to the character of the
subdivision.
(d)
Where feasible, stormwater should be directed to enter the nearest
open stream channel. At all outfalls of drainage systems, a reinforced
concrete headwall or reinforced concrete flared end shall be provided.
Stormwater shall not be permitted to cross any roadway upon the surface
but must be piped underground.
(e)
In general, the design of pipes shall be such as to provide
for a flow of water at velocities between two feet per second and
10 feet per second under full flow conditions than that required to
achieve the velocities specified. The minimum grade shall be not less
than 0.5% or less than that required to achieve the velocities specified
and the minimum pipe diameter shall be 12 inches, designed to flow
full with the hydraulic gradient at the crown.
[Amended 10-17-2022]
(f)
Storm drains with Class III RCP pipe shall have a minimum of
three feet of cover. Drains with less than three feet of cover shall
use Class V RCP pipe. In no event shall drains have less than 2.0
feet of cover. All changes in pipe class shall be noted on the plan.
In determining the capacity of the pipe drains, the Manning formula
shall be used with coefficient of friction "n" equal to 0.013 for
RCP.
(g)
Catch basins shall have a minimum four-foot sump below the invert.
Catch basins or inlets shall be spaced along both sides of a street
at no greater than 300-foot intervals, and located at all low points
and corner rounding at street junctions. Drain manholes shall be located
at every change of direction and/or elevation but in no cases greater
than 300 feet apart. Catch basins shall not serve as manholes. All
pipes from catch basins shall flow to manholes.
[Amended 10-17-2022]
(h)
Roof drains, cellar drains or any other "private" non-preexisting
drainage systems will not be allowed to connect to the storm drainage
system, unless specifically waived by the Planning Board.
[Amended 12-19-2019]]
(i)
Cross culverts and drainage control facilities shall be based
on all storms up to a one-hundred-year-frequency storm. At cross culverts,
drainage easements shall be established upgradient of the culvert
and delineated on the definitive plan based on the projected one-hundred-year
headwater elevation. The determination of the headwater elevation
shall be based on TR-20 model calculations and the Federal Highway
Administration Hydraulic Engineering Circular No. 5 (HEC 5).
(j)
In some cases, earth and stone-paved open channels should be
used. The typical section of the earth channel should have a flat
bottom and side slopes of one vertical on three horizontal with the
top of the slope at least one foot higher than the design water surface.
The maximum velocity allowed in an open earth channel at design flow
should be 6.0 fps. A coefficient of friction "n" equals to 0.025 maximum
should be used for both the earth and stone-paved channels. Detailed
calculations, plans and profiles showing proposed channels and treatment
of channel base and side slopes shall be submitted for Planning Board
approval.
[Amended 10-17-2022]
(k)
Wherever drainage systems within the subdivision are located
in or terminate in lands owned by others, proper easements in a form
and content acceptable to Town Counsel shall be taken for their access
and maintenance by Town personnel.
(l)
Granite curb inlets per Section M9.04 of the Standard Specification
shall be installed adjacent to all catch basins at low points and
any other location granite curbing is required. If located within
an area of Cape Cod berms, a minimum six feet transition curbing (granite,
Type VA4) shall be installed along the curbline on both sides of the
curb inlet. The Cape Cod berms shall be constructed to blend with
the transition curb.
[Amended 10-17-2022]
(m)
Components of the collection system such as drainage piping,
ditches, swales, etc. may be located within access/utility easements.
Provisions for vehicular access shall be provided along the entire
length of storm drain lines and swales within all designated utility
easements.
(n)
Rip-rap spillways shall be provided at all pipe outfalls and
critical areas within drainage swales or ditches.
[Amended 10-17-2022]
(o)
The drainage design in its entirety shall minimize long-term
safety issues, maintenance, and/or reconstruction requirements to
the satisfaction of the Planning Board.
(p)
All pipe crowns in manholes must match or the crown of the inlet
pipe must be higher than the crown of the outlet pipe.
(q)
No catch basins shall be installed in front of driveway or handicap
ramp openings.
(r)
All runoff from storms up to the one-hundred-year storm must
flow through the drainage control facilities (detention ponds, etc.)
and be mitigated prior to flowing beyond the site. Although the pipes
are designed for the twenty-five-year storm, the runoff for storms
up to the one-hundred-year storm must reach the drainage control facility
either through the pipe systems, swales or overland with easements.
(s)
Stormwater drainage pumping stations are not allowed.
(t)
When in the opinion of the Planning Board, and confirmed by
the reviewing independent registered professional engineer, the existing
street drainage and/or downstream drainage systems are inadequate,
the stormwater management system design shall maintain both rate and
volume controls at pre-development levels.
(2)
Storm drainage construction requirements.
(a)
Drainage facilities shall be provided as indicated on the plan
and in conformity with these regulations and the requirements of Sections
100, 200, 220, 230, 258, and 260 of the Commonwealth of Massachusetts
Department of Transportation Standard Specifications for Highways
and Bridges, herein referred to as the "Standard Specifications."
[Amended 10-17-2022]
(b)
The drainage system shall be in place and functional and approved
by the Highway Surveyor and the Planning Board at the time of the
installation of the binder course pavement. Utility as-built plans
of the installed drainage system must be submitted and approved by
the Planning Board and the Department of Public Works prior to the
installation of the binder course pavement.
(c)
Unsuitable material below normal pipe invert shall be removed
and replaced with suitable material. Unsuitable material shall not
be used for trench backfill. Pipe and conduits shall be surrounded
by six inches of compacted screened gravel if set in earth, and 12
inches if set in rock.
(d)
The standard depth of catch-basins shall be four feet below
the invert of the outlet. Manholes shall be constructed to the required
depth at each junction point and as shown on the plan. Pipe culvert
and pipe drains shall be in conformity with the requirements of Section
230 of the Standard Specifications for installation of pipes.
[Amended 10-17-2022]
(e)
All drain pipes except subdrains shall be reinforced concrete
pipe (RCP) with bell and spigot gasketed joints and shall be installed
according to the size as shown on the plans. No backfilling of pipes
shall be done until approval of the Department of Public Works. All
drainage trenches shall be backfilled per Section 201 of the Standard
Specifications.
[Amended 10-17-2022]
(f)
Where subdrains are required they shall be constructed in conformance
with Section 260 of the Standard Specifications. Such subdrains may
be required by the Board following clearing and grubbing operations.
No drainage pipes from roof drains, driveway drains, or other on-lot
sources shall be connected to the street drainage system. Cast iron
manhole covers and catch basin grates shall be as manufactured by
or equivalent to EJ OMA 5540 frame with EJ OMA 5520 grate. Frame and
grate type to suit. Manhole frames and covers. EJ OMA 1240 solid cover
marked "DRAIN" cast into the manhole for catch basins. The word "DRAIN"
shall be cast into the drain manhole covers.
[Amended 10-17-2022]
(g)
No more than four pipe openings shall be allowed in any one
manhole. Four-foot-diameter manholes will be used for drains up to
30 inches in diameter. Five-foot-diameter manholes shall be used for
pipe diameters between 36 inches and 48 inches. Pipes shall not enter
a manhole less than 90° of the direction of flow. All connecting
lines shall have bricked inverts rounded into the direction of flow.
A.
Gas, cable, TV, and electric lines shall be installed to meet the
standards of the respective utility companies.
B.
All utilities shall be underground. Other portions of the utility
systems that are constructed above ground shall be screened by evergreen
shrubs.
C.
The utility strip shall be located on the opposite side of the street
from the sidewalk.
D.
All utilities installed shall have a capacity judged by the Planning
Board to meet future requirements.
E.
Utilities shall be inspected upon installation, in accordance with § 300-6.1, and approved before continuing the project.
F.
Where public sewers are required, the following design standards
shall apply:
(1)
Public sewers shall be designed according to professional engineering
practices and in accordance with the requirements of the standards
of the Sewer Department.
[Amended 10-17-2022]
(2)
Public sewers shall be not less than eight inches in diameter;
house services not less than six inches.
(3)
Manholes shall be located at every change in grade or horizontal
alignment but not more than 300 feet apart.
G.
Where public water service is required, the following design standards
shall apply:
(1)
Public water mains shall be not less than eight-inch-diameter
Class 52 cement-lined ductile iron pipe and fittings with push-on
gasket joints.
[Amended 10-17-2022]
(2)
Connection to Town water mains shall be the subdivider's responsibility
but shall be made only under the direction of the Department of Public
Works Superintendent. A water permit must be obtained from the Department
of Public Works prior to tapping any main.
(3)
Water mains shall be laid in dry trenches on a twelve-inch bed
of sand or approved material. Construction pipe shall be manually
tamped with sand the full length of the pipe up to 1/2 the diameter
of the pipe so as to eliminate any voids under the pipe.
(4)
Water mains shall be laid to provide a minimum cover of five
feet below the finished grade and a maximum of seven feet.
A.
Suitable mature trees along the road should be kept where possible.
Once the road has been completed, shade trees of at least two-inch
caliper at diameter breast high (DBH) should be planted on average
every 40 feet along each side of the road. Trees shall be located
four feet beyond the edge of the curbing and shall not interfere with
existing or proposed sewer or utility connections. Shade trees meeting
the approval of the Planning Board shall be planted.
B.
In order to protect against the potential for all of the street trees
in any subdivision to be lost to disease or insects, no more than
1/3 of the trees planted shall be of the same species.
C.
Trees planted shall have temporary labels so that inspectors can
determine that the species shown on the plan have actually been planted.
The applicant is responsible for assuring that all planted trees are
alive at the time of final performance guarantee release. All trees
should be alive one year after planting.
In determining the design standards to apply to any particular
subdivision plan, the Board shall consider the potential for future
development along or off the proposed ways. The extent of the potential
for future development shall be based upon the existence of developable
land contiguous with the subdivision property, and of dividable lots
in the subdivision property, whether or not such development or division
might constitute a subdivision; and shall also be based upon the topography
of such land or lots, and the zoning provisions and other laws applicable
to such land or lots which may affect its use. The Board shall apply
to the particular subdivision plan those design standards that would
be applied if the adjoining land or dividable lots were developed
so as to maximize the burden imposed upon the ways, utilities, and
services of the proposed subdivision. The Board may waive the requirements
of this section only upon the undertaking of the applicant, by covenant
or otherwise, to the satisfaction of the Board, which will prevent
the imposition of an increased burden upon the subdivision by future
development, and also upon a finding by the Board that such waiver
is in the interest of the public health, safety and welfare.