See also Chapter
235, Stormwater Management, of the Town Bylaws.
A. General. Storm drains, culverts, swales, detention basins, and related
facilities shall be designed to permit the unimpeded flow of all natural
watercourses, to ensure adequate drainage at all low points along
streets, to control erosion, and to intercept stormwater runoff along
streets at intervals reasonably related to the extent and grade of
the area being drained. Where determined to be appropriate to the
Planning Board, stormwater may be carried on the surface of the ground
and recharged (herein, "open system") rather than piped to surface
water (herein, "closed system"). Peak storm discharge rate at the
boundaries of the subdivision in a twenty-five-year-frequency storm
shall be no higher following development than prior to development,
unless authorized by the Planning Board after consultation with the
Conservation Commission, and determination that the receiving wetlands
or water bodies may absorb the increase, or that the provision of
detention capacity is sufficient. In a floodplain, adequate drainage
systems shall be provided to reduce exposure to flood hazards.
B. Full build-out. Stormwater run-off calculations for proposed conditions
should use general land use conditions that assume full build-out
within the existing zoning requirements. Less conservative values
may be applied to determine peak storm discharge rate when coupled
with enforceable land use restrictions.
C. Location of detention basins. Detention basins shall not be located
on a separate parcel. No detention basin shall be located within 50
feet of any lot line. Detention ponds shall have deeded easements
to the Town. A bond shall be kept in the Town's detention ponds escrow
for upkeep in case of owner's lack of maintenance.
D. Storm drains.
(1) Except where drainage swales are used, catch basins will be required
on both sides of the roadway on continuous grades at intervals of
not more than 250 feet. Storm drains and culverts shall be no less
than 12 inches inside diameter and shall be of greater size if required
by design considerations. All drains shall have a minimum of three-foot
cover, except where reinforced concrete pipe is used and there the
minimum cover shall be two feet. Pipe approved by the Massachusetts
Department of Transportation (DOT) shall be installed in accordance
with DOH requirements. The subdivider shall specify the class of pipe
to be used.
(2) Proper connections shall be made with any existing drains in adjacent
streets or easements where they may exist and prove adequate to accommodate
the drainage flow from the subdivision; and in the absence of such
facilities, or the inadequacy of the same, it shall be the responsibility
of the developer to extend drains from the subdivision as required
a manner determined by the Department of Public Works, or Planning
Board.
(3) Side drains during construction may be required by the Department
of Public Works. Six-inch subdrains, five feet off the side line,
may be required in all cuts over three feet.
E. Catch basins. Catch basins shall be provided with grates installed
and approved as to design by the Planning Board. Manholes shall be
provided at changes in direction, whenever there is a change in size
of pipe, and so as to eliminate the draining of one basin into another
basin. Catch basins and manholes shall be constructed with standard
concrete blocks, with brick and mortar or, if required by depth, of
reinforced concrete, and shall have a two-foot-deep sump.
F. Certificate of occupancy. No certificate of occupancy shall be issued
for any dwelling unit in a subdivision until the stormwater management
system is fully operational.
In a floodplain, all public utilities and facilities such as
gas, electrical, and water systems shall be located and constructed
to minimize or eliminate flood damage.