Specifications and drawings on Figures 9, 10,
11, Appendix B, show the minimum acceptable construction for typical catch
basins and curb inlets. Whenever, in the opinion of the Town Superintendent,
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 at any time prior to paving.
A. Location. Catch basins shall be constructed at all
points of change of slope or 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%, 300
feet on slopes from 3% to 6% and 250 feet on slopes over 6% in steepness.
B. Excavation and construction.
(1) Holes for catch basin shall be excavated to a depth
of nine inches below the bottom of the catch basin. The subbase shall
be spread to a uniform compacted depth of nine inches over the entire
area under the base. On this 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 stretcher blocks eight inches thick or cast-in place
concrete.
(3) Below 10 feet from the finished surface, the catch
basin walls shall be 12 inches thick and shall be constructed of concrete
block or cast-in-place concrete. All hollows between blocks in each
course shall be completely filled with mortar before the succeeding
course is laid so that finished wall is solid.
(4) All blocks forming the catch basin walls shall be
laid up with mortar composed of portland cement and mortar sand in
the proportion of one to two.
(5) Approved precast catch basins may also be used.
(6) 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.
(7) Mortar used for filling vertical or inclined joints
shall be of such consistency that will require rodding for placing.
The mortar shall be rodded until it rises to the top and completely
fills the joint. All joints in masonry units shall be full mortar
joints not greater than 1/2 inch wide on the inside and outside.
(8) All construction and materials shall comply with Section
604 of the current Standard Specifications of the State of New York,
Department of Transportation.
C. Installation of pipes.
(1) Concrete blocks around all pipes entering or leaving
catch basins 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 section.
(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) Catch basins shall be capped with curb inlets having
a minimum frame opening of 24 inches by 36 inches of a type as designated
by the Town Superintendent of Highways.
(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 9, Appendix B.
(3) Cast-iron frames and grates 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.
(4) Curb-front openings on all curb inlets shall have,
centered in the opening, a solid horizontal bar to prevent the ingress
of small children. This bar shall be part of the casting or solidly
welded in place subsequent to manufacture.
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 of wrought
iron having a minimum diameter of one inch, which shall be hot-bent
to shape and hot-dipped galvanized after bending. They 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 to the base steps
shall be no more than 18 inches apart. Reinforced plastic steps meeting
Section 725-02 of the Standard Specifications, State of New York,
Department of Transportation, Construction Division, may be used in
lieu thereof.