Specifications and drawings on Figures 9 and 10, Appendix B, show the minimum acceptable construction for typical catch basins
and curb inlets. Whenever, in the opinion of the Town Superintendent or designated
Town Engineer, ground conditions or other circumstances require larger or
heavier materials, additional materials, reinforcing, or other modifications
and improvements in design and construction shall be made as directed by the
Town Superintendent or designated Town Engineer at any time prior to paving.
A. Location. Catch basins shall be constructed at all points
of change of slope of alignment and at all junction points. Catch basins shall
be located in the lows of sag vertical curves as necessary to prevent excess
ponding. At no time shall catch basins be spaced farther apart than 400 feet
on slopes less than 3% in grade, 300 feet on slopes from 3% to 6% in grade
and 250 feet on slopes over 6% in grade.
B. Excavation and construction.
(1) Holes for catch basins shall be excavated to a depth
of 36 inches below the designated elevation of the invert of the effluent
pipe. Crushed stone or run-of-bank gravel to a uniform depth of nine inches
shall be leveled and compacted over the entire area under the base. On this
stone or gravel base, an eight-inch thick slab of 1-2-4 mix portland cement
concrete shall be placed. The slab shall extend four inches beyond the outside
of the walls of the catch basin on every side and shall be smooth and level.
(2) To a maximum depth of 10 feet below the finished surface,
the catch basin walls shall be constructed of solid concrete catch basin corner
and cast-in-place concrete. Use of solid concrete blocks shall be authorized
only in situations where the elevation of the catch basin frame must be adjusted
for field conditions.
(3) Below 10 feet from the finished surface, the catch basin
walls shall be 12 inches thick and shall be constructed of cast-in-place concrete.
(4) Inside dimensions of the catch basin shall remain constant
from top to bottom and shall match the frame opening of the curb inlet to
be used.
(5) All construction and materials shall comply with Section
604 of the current Standard Specifications of the State of New York, Department
of Transportation. Use of precast basins acceptable to the designated Town
Engineer shall be encouraged.
C. Installation of pipes.
(1) Openings for all pipes entering or leaving the catch
basin shall be cut to fit the contours of the pipes as closely as possible.
Remaining interstices shall be solidly filled with mortar for the full thickness
of the wall. Ends of all pipes shall be cut off flush with the inside surfaces
of the catch basin walls and shall project outside a sufficient distance to
allow for proper connection with adjoining pipe sections.
(2) When the diameter of the effluent pipe is greater than
that of an influent pipe, the elevation of the top of the influent pipe shall
be no lower than the elevation of the top of the effluent pipe.
(3) When the diameter of the effluent pipe is the same as
or smaller than that of an influent pipe, the elevation of the invert of the
influent pipe shall be no lower than the elevation of the invert of the effluent
pipe. In no case shall the top of any influent pipe be more than five feet
above the invert of the effluent pipe.
D. Curb inlets.
(1) Wherever required, catch basins shall be capped with
curb inlets having a minimum frame opening of 30 inches by 48 inches of a
type specified by the designated Town Engineer.
(2) Curb-type inlets shall be installed so that the top of
the grating shall be flush with the finished grade, and the pavement shall
be sloped toward the inlet as shown in Figure 1, Appendix B.
(3) Curb-front openings on all curb inlets shall have, centered
in the opening, a solid horizontal bar to prevent the accidental ingress of
small children. This bar shall be part of the casting or solidly welded in
place subsequent to manufacture.
(4) Catch basin covers and cast-iron curb boxes shall conform
to the current Standard Specifications of the State of New York, Department
of Transportation, Division of Construction, and be designed to carry H-20
highway loading.
E. Steps for catch basins. Catch basins having a depth greater
than 48 inches from the finished surface to the top of the concrete base shall
be provided with steps. Steps shall be solidly set in the masonry at the time
of construction and shall extend all the way through the wall. The steps shall
extend 4 1/2 inches inside the wall of the catch basin. The top step
shall not be more than 18 inches below the finished surface and thence to
the base steps shall be no more than 18 inches apart. Reinforced plastic steps
meeting Section 725-012 of the Standard Specifications, State of New York,
Department of Transportation, Construction Division, are preferred, with aluminum
being an acceptable alternate if approved by the designated Town Engineer.