A.
All lots shown on a definitive plan submitted to the Board for approval
shall comply with the applicable zoning bylaws for the Town of Cohasset,
Massachusetts, in force at the time of application.
B.
Convenient maintenance of all proposed construction shall be a consideration.
C.
Due regard shall be exercised in the design and during the construction
process to ensure that drainage or any other activity above or below
the surface of the ground is not allowed to contaminate any watercourse,
body of water or groundwater.
D.
Earth removal. The tentative or final approval of a definitive plan
by the Board shall not be construed as authorizing the removal of
material from the premises, even though in connection with the construction
of streets shown on the plan. All earth removal within subdivisions
shall be in accordance with the regulations governing earth removal
contained in the Zoning Bylaw for the Town of Cohasset, Massachusetts.[1]
E.
The subdivision shall harmonize and conform with plans for Cohasset
as adopted by the Planning Board and/or Board of Selectmen.
F.
Protection of natural features. Due regard shall be shown for all
natural features, such as large trees, watercourses, scenic points,
historic spots and similar community assets, to preserve, promote
and enhance the natural beauties and amenities of the Town and add
value to the subdivision.
G.
Open spaces. Before approval of a plan, the Board may in proper cases
require the plan to show a park or parks suitably located for playground
or recreation purposes or for providing light and air in accordance
with the Subdivision Control Law. The park or parks shall not be unreasonable
in area in relation to the land being subdivided and to the prospective
uses of such land. Final disposition of such areas shall be in accordance
with the Subdivision Control Law.
H.
In the case of a definitive plan showing the connection of ways within
the subdivision over a private way to a public way, approval of the
definitive plan shall be denied unless the applicant has sufficient
rights in the private way to enable the applicant to bring the private
way into conformance with the requirements of these rules and regulations,
or as waived pursuant to MGL c. 41, § 81R. The definitive
plan shall show such private way, together with other applicable systems.
I.
Obligations of applicant to make improvements. Where the physical
condition or width of a public way from which a subdivision has its
access is considered by the Board to be inadequate to carry the traffic
expected to be generated by such subdivision, the Board may require
the applicant to dedicate a strip of land for the purpose of widening
the abutting public way to a width at least commensurate with that
required within the subdivision and/or to make physical improvements
to and within such public way to the same standards required within
the subdivision. Any such dedication of land for the purpose of way
and any such work performed within such public way shall be made only
with permission of the governmental agency having jurisdiction over
such way, and all costs of any such widening or construction shall
be borne by the applicant.
J.
Wherever possible, subdivision design shall incorporate principles
of sustainable development, energy-conscious design and the Cohasset
Open Space and Recreation Plan.
A.
Streets in the subdivision shall be coordinated with each other and
with the existing street system in a manner satisfactory to the Board,
with due regard to the purpose of the Subdivision Control Law and
these rules and regulations.
(1)
Provision satisfactory to the Board shall be made for the proper
extension of streets, or for access to adjoining property which is
not yet subdivided.
(2)
Reserve strips prohibiting access to streets or adjoining property
shall not be permitted, except where, in the opinion of the Board,
such strips shall be in the public interest.
(3)
Insofar as practical, streets shall be located a suitable distance
from existing dwellings of abutters and/or landscaping shall be provided
as required by the Board to buffer noise and other impacts from proposed
streets.
B.
Alignment.
(1)
The street system shall conform to the approved preliminary plan,
if any.
(2)
Streets shall be continuous, of uniform width and in alignment with
existing streets.
(3)
Long straight roadway sections should be avoided in minor streets.
(4)
Street jogs with center-line offsets of less than 125 feet shall
be avoided.
(5)
Proposed names of all streets in the subdivision shall be subject
to approval by the Assessor, Police Chief, Fire Chief and Emergency
Notification Coordinator (utilizing street naming Form 7 contained
in these rules and regulations) as indicated by the signature of each.
In the event that a proposed name is not approved, the Assessor will
recommend or assign a replacement name.
(6)
Connections with uncompleted extensions of adjacent ways shall be
accomplished. When adjoining property is not subdivided, if required
by the Board, ways shall be laid out to the perimeter of the subdivision
shown on the plan. Easements for temporary turnarounds outside of
the way lines shall be provided. Such easements shall terminate in
the manner provided in MGL c. 41, § 81Q. Except by permission
of the Board, such turnarounds shall be constructed to the same standards
as permanent turnarounds. Frontage for lots abutting a temporary turnaround
shall be computed along the way lines. Due provision shall be made
for demolition of temporary turnaround construction not needed or
authorized after extension of the way.
(7)
The minimum center-line radii of streets shall be 150 feet. Greater
radii may be required for streets which are principal streets in the
Board's opinion. All streets shall be designed to permit safe vehicular
travel. Adequate clear sight distance shall be provided at all road
intersections.
(a)
Clear sight distance at the intersection of a subdivision access
road and an existing way shall be defined by a clear sight triangle
at the intersection. Two sides of the triangle shall coincide with
the center lines of the access road and the existing way respectively.
The third side of the triangle, measured from the center line of the
access road at a point 30 feet from the center line of the existing
way, shall be identified as the clear sight distance. Depending on
maximum design approach speed, along the existing way, minimum clear
sight distance shall be as follows:
|
Maximum Design Approach Speed
(miles per hour)
|
Clear Sight Distance
(feet)
| |
|---|---|---|
|
45
|
350
| |
|
35
|
250
| |
|
25
|
150
|
(b)
Measurements of the clear sight distance shall be based on a
line of sight of a level 5 1/2 feet above road surfaces at each end
of the clear sight distance.
(c)
Inside the clear sight triangle, no vision-obstructing object
shall be permitted within a vertical distance of 3 1/2 feet from the
line of sight.
(d)
Similar sight distance methodology shall be used in the design
of interior subdivision intersections.
(8)
As a minimum requirement for adequate sight distance at intersections,
right-of-way lines shall be rounded by tangent arcs with minimum radii
of 30 feet. To ensure adequate sight and to accommodate turning of
emergency vehicles, the Board may require greater radii.
(9)
No street shall intersect any other street at less than a seventy-five-degree
angle.
(10)
Intersections shall be separated from other road intersections
on the same or opposite side by a minimum of 200 feet. This requirement
shall apply not only to separation of road intersections within a
subdivision, but also to separation of any subdivision access road
from any other intersection at any existing way.
C.
Width.
(1)
In areas zoned for residences, street layouts shall not be less than
40 feet in width. Streets which, in the opinion of the Board, may
be used for through or heavy local traffic must be at least 50 feet
in width.
(2)
In areas zoned for industry, the minimum street widths shall be not
less than 50 feet.
D.
Grade. Except as noted below, grades of all streets shall not be
less than 1%, nor more than 6%. Where the 6% requirement would result
in considerable injury to the aesthetic value of the site due to extensive
cut and/or fill or tree removal, the Board may waive the 6% requirement
provided such waiver is consistent with safety determinants, including
the distance from an intersection, the number of housing units served,
the type of street, the length of the steeper graded portion of the
street, the horizontal alignment and street curvature. At all intersections,
grades of streets shall not exceed 2% within a distance of 50 feet
from the beginning of the intersection. (The beginning of the intersection
as referred to herein shall be defined as the point at which the edges
of the travel lanes intersect.) At intersections of two proposed streets,
grades of streets shall not exceed 2% within 50 feet from the beginning
of the intersection. Street grade at cul-de-sac turnarounds shall
not exceed 3%. There shall be a vertical curve for any change in street
grade. Vertical curves shall be designed considering drainage and
sight distance impacts. Vertical curves shall not be designed with
over 50 feet of the curve at a grade less than 0.5%.
E.
Cross section. Streets shall be constructed in accordance with the
standards as shown on the Typical Cross Sections for Street Layouts
(see Figure 1 and Figure 2) and in accordance with these regulations.[1]
[1]
Editor's Note: Figures 1 and 2 are included as attachments to this chapter.
F.
Dead-end street.
(1)
Dead-end streets shall not be longer than 1,500 feet as measured
by street stationing.
(2)
The paved area of temporary or permanent culs-de-sac shall have an
outside radius not less than 50 feet. Cul-de-sac stationing shall
loop around the cul-de-sac 20 feet or other approved distance off
the street side line and rejoin the roadway stationing at the beginning
of the cul-de-sac.
(3)
Permanent culs-de-sac in residential zones shall have planting islands
in their center with a radius of 15 feet.
All utilities, except as otherwise specified, shall be placed
underground at the time of initial construction in accordance with
the following:
A.
Storm drainage.
(1)
A complete and adequate storm drainage system, designed to the satisfaction
of the Board, shall be so laid out and of sufficient size as to permit
unimpeded flow of all natural waterways, to provide adequate drainage
of all surface and subsurface water of the street system so that water
does not accumulate thereon, to intercept stormwater runoff from the
adjoining land and to eliminate undesirable or unnatural accumulation
of water on any portion of the subdivision or surrounding property.
(a)
The design shall provide for minimum subsequent maintenance.
Design of drainage shall be such as not to increase off-site flooding.
Analysis of drainage and flooding impacts off site for the two-, ten-,
and one-hundred-year storm shall be submitted as evidence of conformance
with these regulations.
(b)
The design of all drainage systems for street drainage within
the subdivision, including catch basin grates, shall be in accordance
with calculations, based upon the storm frequency and rainfall intensity
data provided in Figure 6,[1] utilizing the rational method. Other methods with proven
predictive capabilities (e.g., those based on TR 55) may be approved.
Said approval shall be solely at the discretion of the Board.
[1]
Editor's Note: Figure 6 is included as an attachment to this chapter.
(c)
Design of detention ponds shall be based on the latest edition
of Urban Hydrology for Small Watersheds, Technical Release No. 55,
by the Engineering Division, Natural Resources Conservation Service,
United States Department of Agriculture, with the exception that rainfall
intensity curves used for the design of all drainage conveyance and
storage systems shall be based on Atlas of Precipitation Extremes
for the Northeastern United States and Southeastern Canada, Northeast
Regional Climate Center Research Series Publication No. RR 93-5, September
1993, or the most recent version. The rational method shall not be
used to generate rainfall hydrographs used in the design of detention
ponds or similar water storage structures. Calculations shall be based
upon the following storm frequencies:
(d)
Notwithstanding the above requirements, all components of the
drainage system shall be designed so that the drainage system functions
as intended.
(2)
In certain instances, the Board may require that the design of a
drainage system be based upon storms of greater frequency.
(3)
Calculations shall be made using recent topographic maps for the
entire contributing drainage area, including those areas outside the
subdivision. Copies of all drainage calculations and Town topographic
maps or other more recent or accurate maps (where available) illustrating
the entire drainage area and showing all subarea boundaries utilized
in said calculations shall be submitted as part of the definitive
plan submission.
(4)
The storm drain system shall include catch basins, manholes, culverts,
drain lines, headwalls, flared ends and such other items as may be
required to complete the system to the satisfaction of the Board.
(a)
Catch basins shall be located in pairs, one on each side of
the roadway, at all low points or sag curves in the roadway, at intervals
of not more than 400 feet on continuous grades of the roadway, and
at or near the corners of the roadway at intersecting streets. Each
catch basin shall connect directly to a manhole.
(b)
Manholes shall be located at all changes in direction, either
horizontally or vertically, of a drain line or at the intersection
of two or more drain lines, or so located that no drain line of a
length greater than 400 feet would exist without a manhole.
(c)
Culverts shall be designed on the assumption that the entire
drainage area is built up to that intensity and in the manner which
the applicable section(s) of the Zoning Bylaw would allow. The calculations
(or a copy thereof) necessary to determine the size of any culvert
which carries a brook, stream, river, or other natural waterway shall
be submitted to the Board for review. All culverts shall have a concrete
headwall at each end, and any culvert over 36 inches in diameter shall
include at the upstream end additional protection, as approved by
the Board, for roadway side slopes. Headwalls shall be constructed
in accordance with MassDOT Standard Details.
(d)
In areas where the finished grade of the roadway is less than
four feet above the water table or in other areas where, in the opinion
of the Board, the subgrade must be drained, a system of subdrains
acceptable to the Board may be required.
(e)
All drains shall be a minimum of 12 inches in diameter and shall
be laid on a slope of not less than 0.5%. The minimum design velocity
shall be three feet per second and the maximum design velocity shall
be 10 feet per second. All outfalls shall extend to a natural waterway.
Provision shall be made for the disposal of surface water intercepted
or collected by the system in such manner that no flow is conducted
over Town ways, or over land of others unless a drainage easement
therefor is obtained or unless such flow is essentially the same quantity
as previously existed in the same location.
[1]
Stormwater shall be directed to enter the most suitable natural
watercourse or be properly connected to any existing drains in adjacent
streets or easements which may exist. Where no adequate drainage system
exists, or where it is inadequate in the opinion of the Planning Board,
it shall be the responsibility of the applicant to extend the system
outside the subdivision in a manner specified or approved by the Board
to properly dispose of all the drainage from the proposed subdivision.
[2]
Where adjacent land is not subdivided, provision shall be made
for the extension of the system by continuing appropriate drains to
the boundary of the subdivision at such size and grade as will allow
their proper projection.
(f)
A concrete headwall or concrete flared end section designed
in accordance with MassDOT Standard Details shall be provided at the
outfall end of all drains. Scour protection shall be provided at all
headwalls or flared ends.
(g)
Where applicable, tidal effects shall be taken into account
in the design of the storm drainage system.
(h)
Private drains may be installed to connect to the public stormwater
drainage system. Design and installation shall be by agreement with
the Town. A plan of the private drain shall be furnished to the Board
for approval.
(i)
Private drains shall be so located on the lot and so constructed
such that no seepage from any on-lot sewerage system shall enter the
private drain.
(j)
Culverts or drains proposed to have grates at their inlets shall
be designed with their inlet capacity reduced 25%.
(k)
Culvert and drain design shall be based on a Manning roughness
coefficient "n" = 0.013.
(l)
Grates shall be provided on the inlet and outlet ends of all
pipes over 15 inches in diameter.
(m)
At the request of the Board a drainage design to eliminate or
remove any other water or waters within the subdivision limits and
not designated as roadway or subsurface water, and which is otherwise
not taken care of, shall be drawn in a manner approved by the Board.
(n)
Drainage design for street drainage shall be such that pipes
flow without surcharge for the storm frequency and intensity required.
B.
Public water supply.
(1)
No subdivision of land shall be approved by the Planning Board unless
all lots therein are provided with water by connection to the Town
of Cohasset's public water supply system. Water mains and their appurtenances
must be installed in accordance with the Rules and Regulations of
the Cohasset Water Department and approved by the Department. Size
of water mains shall be as recommended by the Cohasset Water Department.
(2)
Public water mains shall be not less than eight inches in diameter
unless a smaller diameter is approved by the Cohasset Water Department.
There shall be a hydrant within 500 feet of any existing or potentially
existing building.
(3)
Hydrants shall be located as shown on the typical cross section for
the applicable street.
C.
Sewer system.
(1)
All public sewer facilities design shall conform to the applicable
current rules and regulations of the Sewer Commission and Guides for
the Design of Wastewater Treatment Works by the Technical Advisory
Board of the New England Interstate Water Pollution Control Commission.
(2)
Sewer design shall be reviewed by the Sewer Commission and the Planning
Board. Subdivisions within 500 feet of an existing sewer may be required
to connect into the existing sewer.
(3)
On-site sewage disposal systems shall be designed in accordance with
all applicable local, state and federal regulations.
D.
Other public utilities.
(1)
Electricity, communication, gas and cable television shall be installed
in all subdivisions. They shall be installed underground in the location
shown on the appropriate typical cross section contained herein and
shall be installed in accordance with the utility company having jurisdiction.
(2)
If a utility mentioned above is not proposed for the site, written
evidence from the specific utility company involved that the utility
is not available to serve the site shall be submitted.
E.
Easements.
(1)
Easements for storm drains, sanitary sewers or water mains across
lots, or centered on rear or side lot lines, shall be provided for
the Town where necessary and shall be at least 20 feet wide. No easement
shall be permitted across land of others unless an agreement in proper
form is obtained permitting such easement.
(2)
No building or on-lot sewerage system shall be erected within an
easement.
(3)
Where a subdivision is traversed by a watercourse, drainageway, channel
or stream, the Board may require that there by conveyed to the Town
without cost a stormwater easement of adequate width depending upon
the width of the stream. This easement shall conform substantially
to the lines of such watercourse, drainageway, channel or stream and
shall provide for construction, maintenance or other necessary purposes
in relation thereto.
