A.
A hydraulic design report prepared by a professional
engineer, containing design information for all street or highway drainage
structures, storm sewers and channels, must be submitted to the designated
Town Engineer and Town Superintendent of Highways. This report should analyze
before- and after-development conditions and contain the basic design data
required to arrive at each drainage structure size, such as design frequency,
flow rate, grade, velocity, area and method used in determining the waterway
size. A consideration should also be given to anticipated (if any) future
development and any urbanization of the area.
B.
The after-development condition should limit the peak
discharge rate of runoff from the property being served by the proposed road
to that value determined in the before-development condition. Furthermore,
the design frequency storm should be a function of the size of the drainage
basin which is being analyzed, i.e.:
(1)
For watersheds with drainage areas less than 320 acres,
all structures shall be designed to carry the peak runoff for a twenty-five-year
storm.
(2)
For watersheds with drainage areas between 320 and 640
acres, the structures shall be designed to carry peak runoff for a fifty-year
storm.
(3)
For watersheds with drainage areas larger than one square
mile, all structures shall be designed to carry peak runoff for the one-hundred-year
storm.
C.
There should be enough information shown on plans and
profiles to properly construct all the required drainage facilities. Type
and size of culvert, end treatments of inlet and outlet, the gage of metal
pipe or class of concrete pipe, invert elevation of inlet and outlet, ditch
and channel section, gutters, channel protection and alignment of ditches
are some of the information required on plans and profiles.
A.
The developer shall dedicate to the Town by recordable
instrument all easements as shown on the plat.
B.
All drainage easements must have a minimum width of 30
feet and shall include the right to enter upon said property for the purposes
of installing, maintaining and repairing the ditches and pipes as placed in
such easement. It is the policy of the Town that all storm drainage be enclosed
in drainage pipe, and all easements shall contain a provision providing for
the right to install underground pipes and to discharge stormwater therein.
The developer shall also install in said easements pipe of a size sufficient
to provide for present and anticipated future runoff.
C.
Where it is proposed that stormwater be drained from
the street or highway or from other lands of the developer to the perimeter
of the developer's property, easements shall be provided in recordable
form and free and clear of all liens from the adjoining owners permitting
the discharge of stormwater drainage onto such adjoining lands.
D.
The developer shall provide an attorney's certificate
of title indicating that the above-mentioned easements and rights to discharge
surface water are free and clear of all liens.
A.
Storm drain and culvert pipe may be corrugated metal
or reinforced concrete with a minimum diameter of 15 inches.
B.
Round corrugated steel pipe and pipe arches, fully bituminous
coated, and end sections shall conform to Section 707-02 of the current Standard
Specifications of the State of New York, Department of Transportation, with
the following exceptions:
(1)
All collars or connecting bands shall be 12 inches wide
and shall be furnished with bolts six inches long.
(2)
Round corrugated aluminum pipe, pipe arches and end sections
shall conform to Section 707-13 of the current Standard Specifications of
the State of New York, Department of Transportation.
(3)
Reinforced concrete pipe shall conform to Sections 706-02
and 706-10, respectively, of the current Standard Specifications of the State
of New York, Department of Transportation.
(4)
All reinforced concrete pipe shall be manufactured with
slip joints or bell and spigot joints.
(5)
Each piece of reinforced concrete pipe shall be marked
with the specification number and the date of manufacture.
(6)
Reinforced concrete pipe shall be sealed with flexible
watertight elastromeric gaskets, approved bituminous sealers or plastic sealers.
Bituminous or plastic sealants shall be applied at the time the pipe is being
laid to line and grade. Such sealants shall be installed in accordance with
the sealant manufacturer's instructions so that the joint is completely
filled with the sealant.
(7)
Corrugated metal pipe and pipe arch connections for making
field joints shall consist of corrugated bands so constructed as to lap on
equal portions of each culvert section to be connected.
(8)
The height of the fill and pipe classes shall be designed
to meet the minimum requirement of H-20, highway loading.
A.
Whenever a drain pipe begins or ends in an open ditch,
pond or stream, inlet and outlet ends shall be designed to protect embankments
and channels and to preserve the hydraulic efficiency of the pipe.
C.
Prefabricated end sections shall be of similar material
and construction to the pipe. End sections shall be connected to the pipe
in the same manner as pipe sections are connected.
A.
Underdrains may be a perforated-metal or porous-pipe
type and placed in trenches and surrounded by material which is both pervious
to water and capable of protecting the pipe infiltration by the surrounding
soil. (See Figure 8a.[1])
[1]
Editor's Note: Figure 8a is included in Appendix B at the end
of this chapter.
B.
Underdrains must be sloped positively to an outlet such
as a drainage channel or a closed drainage system.
C.
Figures 8b and 11 of Appendix B[2] show the installation of underdrain for the purpose of draining
of pavement sections. These figures may be modified to apply to specific conditions.
However, criteria described below should be considered.
[2]
Editor's Note: Figures 8b and 11 of Appendix B are included at
the end of this chapter.
D.
The underdrains should be placed at the interface of
the pavement and curb and should intercept the water from the highest water-bearing
layer of the pavement section.
Specifications and drawings on Figures 9 and 10, Appendix B,[1] 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.[2]
[2]
Editor's Note: Figure 1 of Appendix B is included at the end of this chapter.
(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.
[1]
Editor's Note: Figures 9 and 10 of Appendix B are included at
the end of this chapter.
A.
With the approval of the Town Superintendent of Highways
and the designated Town Engineer, open ditches and swales for back lots and
side slopes may be used in lieu of storm drain pipes when the grade of the
land traversed is flat or when it is desirable to drain and dry up the surrounding
area.
B.
In no case shall the grade of an open ditch or swale
exceed 6%. The following guideline shall be used in treatment of these ditches:
|
Grade
|
Treatment
| |
|---|---|---|
|
Up to 1%
|
Seed and mulch
| |
|
Up to 3 1/2%
|
Jute mesh and seed
| |
|
Up to 5%
|
Sod
| |
|
Over 5%
|
Rip-rap or asphalt concrete
|
C.
Rip-rap, when called for, shall consist of field stone
or rough, unhewn quarry stones as nearly cubical in form as is practicable,
placed upon a slope not steeper than one-to-two and so laid that the weight
of the large stones is carried by the soil and not by the stone adjacent.
All stones shall weigh 50 to 150 pounds each, and at least 60% of them shall
weigh more than 100 pounds each.
D.
The largest stones shall be placed first, roughly arranged
and in close contact. The spaces between the larger stones shall be filled
with spalls of suitable size.
E.
Whenever a drain pipe enters an open ditch, the bottom
and sides of the ditch shall be rip-rapped for a distance of at least 30 feet
beyond the end of the pipe.
F.
Roadside ditches over five-percent grade shall be paved
with asphalt concrete in minimum three-inch thickness.
