[HISTORY: Adopted by the Town Board of the Town of Warwick as Appendix
3 of Warwick Municipal Code, 1973. Amended in its entirety 6-23-1988 by L.L.
No. 1-1988. Subsequent amendments noted where applicable.]
The purpose of these specifications is to establish the minimum acceptable
standards for sewers in streets in the Town of Warwick, County of Orange and
State of New York.
A.
General.
(1)
All plans for sewage works shall bear a suitable title
showing the name of the municipality, sewer district or institution. They
shall show the scale in feet, a graphical scale, the North point, date and
the name of the engineer, with his certificate number and imprint of his registration
seal.
(2)
Detail plans shall consist of: plan views, elevations,
sections and supplementary views which, together with the specifications and
general layouts, provide the working information for the contract and construction
of the works. They shall also include: dimensions and relative elevations
of structures, the location and outline form of equipment, location and size
of piping, water levels and ground elevations.
B.
Plans of sewers.
(1)
A comprehensive plan of existing and proposed sewers
shall be submitted for projects involving new sewer systems and substantial
additions to existing systems. This plan shall show the following:
(a)
Topography and elevations. Existing or proposed streets
and all streams or water surfaces shall be clearly shown. Contour lines at
suitable intervals should be included.
(b)
Streams. The direction of flow in all streams and high-
and low-water elevations of all water surfaces at sewer outlets and overflows
shall be shown.
(c)
Boundaries. The boundary lines of the municipality or
the sewer district and the area to be sewered shall be shown.
(2)
The plan shall show the location, size and direction
of flow of all existing and proposed sanitary sewers draining to the treatment
works concerned. Detail plans shall be submitted. Profiles should have a horizontal
scale of not more than 100 feet to the inch and a vertical scale of not more
than 10 feet to the inch. Plan views should be drawn to a corresponding horizontal
scale and preferably be shown on the same sheet. Plans and profiles shall
show:
(a)
Location of streets and sewers.
(b)
Line and material; depth.
[1]
Line of ground surface; size, material and type of pipe;
length between manholes; invert and surface elevation at each manhole; and
grade of sewer between each two adjacent manholes. (All manholes shall be
numbered on the profile.)
[2]
Where there is any question as to the sewer being sufficiently
deep to serve any residence, the elevation and location of the basement floor
shall be plotted on the profile of the sewer which is to serve the house in
question. The engineer shall state that all sewers are sufficiently deep to
serve adjacent basements except where otherwise noted on the plans.
(c)
Locations of all special features, such as inverted siphons,
concrete encasements, elevated sewers, etc.
(d)
All known existing structures and utilities, both above
and below ground, which might interfere with the proposed construction, particularly
water mains, gas mains, storm drains and telephone and power conduits.
(e)
Special detail drawings, made to a scale to clearly show
the nature of the design, shall be furnished to show the following particulars:
[1]
All stream crossings and sewer outlets, with elevation
of the stream bed and of normal and extreme high- and low-water levels.
[2]
Details of all special sewer joints and cross sections;
and details of all sewer appurtenances such as manholes, inspection chambers,
inverted siphons and elevated sewers.
Complete technical specifications for the construction of sewers shall
accompany the plans. The specifications accompanying construction drawings
shall include, but not be limited to, all construction information not shown
on the drawings which is necessary to inform the builder in detail of the
design requirements for the quality of materials, workmanship and fabrication
of the project. It shall also include: allowable infiltration; construction
materials; special filter materials, such as stone, sand, gravel or slag;
miscellaneous appurtenances; instructions for testing materials and equipment
as necessary to meet design standards; and performance tests for the completed
works and component units.
Any deviation from approved plans or specifications affecting capacity,
flow or point of discharge shall be approved, in writing, before such changes
are made. Plans or specifications so revised should, therefore, be submitted
well in advance of any construction work which will be affected by such changes,
to permit sufficient time for review and approval. As-built plans clearly
showing such alterations shall be submitted to the Town Engineer at the completion
of the work.
A.
Minimum size. No gravity sewer conveying raw sewage shall
be less than eight inches in diameter.
B.
Depth. In general, sewers should be sufficiently deep
to receive sewage from basements and to prevent freezing. Insulation shall
be provided for sewers that cannot be placed at a depth sufficient to prevent
freezing.
C.
Slope.
(1)
All sewers shall be designed and constructed to give
mean velocities, when flowing full, of not less than 2.0 feet per second based
on Kutter's formula using an "n" value of 0.013.
(2)
Slopes slightly less than those required for the two-and-zero-tenths-feet-per-second
velocity, when flowing full, may be permitted. Such decreased slopes will
only be considered where the depth of flow will be 0.3 of the diameter or
greater for design average flow. Whenever such decreased slopes are selected,
the design engineer must furnish his computations of the anticipated flow
velocities of average and daily or weekly peak flow rates. The pipe diameter
and slope shall be selected to obtain the greatest practical velocities to
minimize settling problems.
(3)
Sewers shall be laid with uniform slope between manholes.
(4)
Where velocities greater than 15 feet per second are
attained, special provision shall be made to protect against displacement
by erosion and shock.
(5)
Sewers on twenty-percent slopes or greater shall be anchored
securely with concrete anchors or equal, spaced as follows:
D.
Alignment. Sewers 24 inches or less shall be laid with
straight alignment between manholes. The alignment shall be checked by either
using a laser beam or lamping.
E.
Changes in pipe size. When a smaller sewer joins a larger
one, the invert of the larger sewer should be lowered sufficiently to maintain
the same energy gradient. An approximate method for securing these results
is to place the eight-tenths-depth point of both sewers at the same elevation.
F.
Materials.
(1)
Any generally accepted material for sewers will be given
consideration. The material selected shall give consideration to local conditions,
such as: character of industrial wastes, soil characteristics, exceptionally
heavy external loadings and abrasion.
(2)
All sewers shall be designed to prevent damage from superimposed
loads. Proper allowance for loads on the sewer shall be made because of the
width and depth of trench. Where necessary to withstand extraordinary superimposed
loading, special bedding, concrete cradle or special construction may be used.
G.
Installation.
(1)
Trenching.
(a)
The width of the trench shall be ample to allow the pipe
to be laid and jointed properly and to allow the backfill to be placed and
compacted as needed. The trench sides shall be kept as nearly vertical as
possible. When wider trenches are dug, appropriate bedding class and pipe
strength shall be used.
(b)
Ledge rock, boulder and large stones shall be removed
to provide a minimum clearance of six inches below and on each side of all
pipe(s).
(2)
Connections. Wye or tee fittings or strap-on saddles
shall be installed on the main for all house connections. This connection
shall have a minimum diameter of four inches. The connection shall be laid
in a straight line from the main to a point two feet behind the curbline.
A cleanout to grade shall be installed at the point two feet behind the curbline.
(3)
Pipelaying. All sewers shall be laid true to line and
grade with bells upgrade. The sections of the pipe shall be so laid and fitted
together that, when complete, the sewers will have a smooth and uniform invert.
The pipe shall be thoroughly cleaned before being lowered into the trench,
and any defective pipe shall be removed from the job and discarded.
(4)
Bedding.
(a)
Bedding Classes A, B and C, as described in ASTM C12-74
(ANSI A106.2) or WPCF MOP No. 9 (ASCE MOP No. 37), shall be used for all rigid
pipe, provided that the proper strength pipe is used with the specified bedding
to support the anticipated load.
(b)
Bedding Classes I, II and III, as described in ASTM D2321-74
(ANSI K65, 171), shall be used for all flexible pipe, provided that the proper
strength pipe is used with the specified bedding to support the anticipated
load.
(5)
Backfill.
(a)
Immediately after the pipes have been laid and inspected,
backfilling shall be done with approved material. The material to surround
the pipe shall be loose earth or sand carefully placed and carefully backfilled
and tamped so as to have a thoroughly compacted material, but tamped in such
a manner that the line and grade of the pipe are not disturbed. Backfill material
shall be placed evenly and carefully around the pipe in six-inch layers, and
each layer shall be thoroughly tamped until one foot of cover exists over
the pipe. This portion of the backfill material shall contain no stone larger
than two inches in diameter. The remainder of the backfill may be material
excavated from the trench containing no stones larger than 1/2 cubic foot,
but shall be carefully placed and compacted. This additional material shall
extend to within 12 inches of the road surface where the sewer is in the road,
and shall extend to ground surface where the sewer is in a right-of-way. In
road surfaces, the last 12 inches of fill over the pipe shall be suitable
run-of-bank gravel approved by the Town Engineer.
(b)
If, in the opinion of the Town Engineer, the material
excavated from the trench is not suitable to be used as backfill, the Town
Engineer may direct that the trench be backfilled with run-of-bank sand and/or
gravel.
(c)
Compaction of all backfill material shall be accomplished
by mechanical tampers or vibrators intended for the purpose. Flooding or puddling
may be used with granular materials; but these methods may not be used on
clay material.
(6)
Deflection test.
(a)
Deflection tests shall be performed on all flexible pipe.
The test shall be conducted after the final backfill has been in place at
least 30 days.
(b)
No pipe shall exceed a deflection of 5%.
(c)
If the deflection test is to be run using a rigid ball
or mandrel, it shall have a diameter equal to 95% of the inside diameter of
the pipe. The test shall be performed without mechanical pulling devices.
(7)
Leakage test.
(a)
Rate of infiltration or exfiltration shall not exceed
100 gallons per mile per 24 hours per inch of diameter of pipe. Air test allows
the minimum amount of time for the air pressure inside pipe to drop from 3.5
psig to 2.5 psig; allowable time is a function of pipe size.
(b)
The sewer shall be visually inspected from manhole to
manhole by the Town Engineer prior to final acceptance. The contractor shall
furnish two men to assist the Engineer in seeing that all manholes are complete,
the pipe is cleaned and all sewers are laid straight from manhole to manhole
unless otherwise shown on the drawings. Any defects noted during this inspection
shall be corrected by the contractor to the satisfaction of the Town Engineer,
and the sewer shall be reinspected as specified above.
(c)
When the sewer has been satisfactorily inspected visually,
an infiltration or exfiltration test shall be performed.
(d)
An infiltration or exfiltration test shall be performed
with a minimum positive head of two feet.
(e)
When performing an infiltration test, the contractor
shall block off a section of the system not exceeding 1,000 linear feet and
install a measuring device at the downstream end of the test section. Infiltration
shall not exceed the allowable amount. If the actual infiltration exceeds
the allowable infiltration or if there are visible signs of infiltration,
such as gushing or spurting streams, the contractor shall effect all repairs
necessary to make the pipe sufficiently watertight. The section shall be retested
until the rate of allowable infiltration is met.
(f)
The water exfiltration test shall be performed between
consecutive manholes. After water has been introduced into the section and
all air expelled, a stabilization period shall be allowed for absorption of
water. The water level shall then be raised to two feet above the top of pipe
in the upstream manhole. The quantity of water required to maintain this level
over a forty-eight-hour period shall be measured. Exfiltration shall not exceed
the allowable amount. If the actual exfiltration exceeds the allowable exfiltration
or if there are visible signs of exfiltration from the pipe, the contractor
shall effect all repairs necessary to make the pipe sufficiently watertight.
The section shall be retested until the rate of allowable exfiltration is
met.
(g)
Air testing may be used instead of the water exfiltration
test to measure exfiltration. The section to be tested shall be between consecutive
manholes. Each end of pipe and all branches, laterals and wyes shall be plugged
and securely braced. The plug at each end of pipe shall have provisions to
connect an air hose. Air shall be supplied to the section and monitored so
as not to exceed 5.0 psig. The air pressure shall be maintained between 4.0
and 3.5 psig for at least two minutes to allow air temperature to come to
equilibrium with pipe walls. The air supply shall then be disconnected and
the air pressure allowed to decrease to 3.5 psig. At 3.5 psig, the time shall
be measured for the pressure to drop to 2.5 psig. The following table shows
the allowable time for a loss of 1.0 psig at an average pressure of 3.0 psig:
|
Pipe Size
(inches)
|
Allowable
Time Minutes
|
Seconds
| |
|---|---|---|---|
|
6
|
2
|
15
| |
|
8
|
3
|
57
| |
|
10
|
4
|
43
| |
|
12
|
5
|
40
| |
|
15
|
7
|
05
| |
|
18
|
8
|
30
| |
|
20
|
9
|
50
| |
|
24
|
11
|
20
| |
|
27
|
12
|
40
| |
|
30
|
14
|
30
| |
|
33
|
15
|
50
| |
|
36
|
17
|
10
|
|
If the actual time for a loss of 1.0 psig is less than the allowable
time shown in the above table, the contractor shall determine the source of
leakage and effect all repairs necessary to make the pipe sufficiently airtight.
The section shall be retested until the allowable time is met or exceeded.
|
H.
Manholes.
(1)
Location. Manholes shall be installed: at the end of
each line; at all changes in grade, size or alignment; at all intersections;
and at distances not greater than 400 feet for sewers 15 inches or less and
500 feet for sewers 18 inches to 30 inches.
(2)
Drop type.
(a)
A drop pipe should be provided for a sewer entering a
manhole at an elevation of 24 inches or more above the manhole invert. Where
the difference in elevation between the incoming sewer and the manhole invert
is less than 24 inches, the invert should be filleted to prevent solids deposition.
(b)
Drop manholes should be constructed with an outside drop
connection. Inside drop connection (when necessary) shall be secured to the
interior wall of the manhole and provide access for cleaning. The entire outside
drop connection shall be encased in concrete.
(3)
Diameter. The minimum diameter of manholes shall be 48
inches. A minimum access diameter of 30 inches shall be provided.
(4)
Construction.
(a)
Manholes shall be of the precast concrete or poured-in-place
concrete type. Manholes shall be waterproofed on the exterior. Manholes shall
be provided with aluminum steps on twelve-inch centers vertical.
(b)
Manhole bases shall be installed on a twelve-inch bed
of one-and-one-half-inch crushed stone extending one foot beyond the periphery
of the base.
(c)
Manhole sections shall be set vertical and with sections
and steps in true alignment.
(d)
Rubber gaskets shall be installed in all joints in accordance
with the manufacturer's recommendations.
(e)
Lift holes in sections shall be thoroughly plugged with
rubber plugs made specifically for the sections and as approved by the Engineer
or with mortar. The mortar, made of one part cement to l 1/2 parts sand and
mixed slightly damp to the touch (just short of balling), shall be hammered
into the holes until it is dense and an excess of paste appears on the surface
and shall be finished smooth and flush with the adjoining surface.
(f)
Frames shall be set with the tops conforming accurately
to the grade of the pavement or finished ground surface.
(g)
A maximum of two courses of brick shall be used to adjust
the grade of the frames.
(h)
Frames shall be set concentric with the top of the masonry
and in a full bed of mortar so that the space between the top of the manhole
masonry and the bottom flange of the frame shall be completely filled and
watertight.
(i)
A thick ring of mortar extending to the outer edge of
the masonry shall be placed all around and on the top of the bottom flange.
The mortar shall be smoothly finished and have a slight slope to shed water
away from the frame.
(j)
The flow channel through manholes should be made to conform
in shape and slope to that of sewers.
(k)
Inlet and outlet pipes shall be joined to the manholes
with a gasketed flexible watertight connection or any watertight connection
arrangement that allows differential settlement of the pipe and manhole wall
to take place.
(l)
Watertight manhole covers are to be used wherever the
manhole tops may be flooded by street runoff or high water. Locked manhole
covers may be desirable in isolated easement locations or where vandalism
may be a problem.
A.
Horizontal separation. Sewers shall be laid at least
10 feet horizontally from any existing or proposed water main. The distance
shall be measured edge to edge. In cases where it is not practical to maintain
a ten-foot separation, the Engineer may allow deviation on a case-by-case
basis if supported by data from the design engineer. Such deviation may allow
installation of the sewer closer to a water main, provided that the water
main is in a separate trench or on an undisturbed earth shelf located on one
side of the sewer and at an elevation so that the bottom of the water main
is at least 18 inches above the top of the sewer.
B.
Crossings. Sewers crossing water mains shall be laid
to provide a minimum vertical distance of 18 inches between the outside of
the water main and the outside of the sewer. This shall be the case where
the water main is either above or below the sewer. The crossing shall be arranged
so that the sewer joints will be equidistant and as far as possible from the
water main joints. Where a water main crosses under a sewer, adequate structural
support shall be provided for the sewer to prevent damage to the water main.
C.
Special conditions. When it is impossible to obtain proper
horizontal and vertical separation as stipulated above, the sewer shall be
designed and constructed equal to water pipe and shall be pressure tested
to assure watertightness prior to backfilling.
