Excavation and backfill shall conform to the requirements for
subsurface structure excavation. The contractor shall provide adequate
equipment and so operate it as to maintain an essentially dry excavation,
stable trench bottoms, suitable working conditions, and protection
from water damage throughout and until the completion of the work.
Where groundwater is known to exist or is anticipated in the
area before the air testing would be conducted, the following procedure
shall be used at the time the sewer main and manholes are constructed:
A. Install one-half-inch-diameter pipe nipple (threaded one or both
ends, approximately 10 inches long) through the manhole wall directly
on top of one of the sewer pipes entering the manhole with threaded
end of nipple extending inside the manhole;
B. Seal pipe nipple with a threaded one-half-inch cap;
C. Immediately before testing, determine the groundwater level by removing
the threaded cap from the nipple, blowing air through the pipe nipple
to remove any obstructions, and then connect a clear plastic tube
to the pipe nipple;
D. Hold plastic tube vertically, permitting water to rise in it to the
groundwater level;
E. After water level has stabilized in plastic tube, measure vertical
height of water, in feet, above invert of sewer pipe;
F. Determine air-pressure correction, which must be added to the 3.0
psig normal starting pressure of test, by dividing the vertical height
in feet by 2.31. The result gives the air-pressure correction in pounds
per square inch to be added;
G. Example:
(1)
If the vertical height of water from the sewer invert to the
top of the water column measures 11.55 feet, the additional air pressure
required would be:
(2)
Therefore, the starting pressure of the test would be 3.0 plus
5 or 8.0 psig, and the one-half-pound drop becomes 7.5 psig. There
is no change in the allowable drop (0.5 psig) or in the time requirements
established for the basic air test.
Lamping of all gravity sanitary sewer lines shall be performed
by the engineer in accordance with the following requirements:
A. Lamping consists of visually examining inside of pipe between two
consecutive manholes with the aid of a light and mirror;
B. A light is shown from one manhole towards the other manhole;
C. A mirror is held at the invert of pipe and adjusted so the light
and barrel of pipe can be seen;
D. The barrel of the pipe shall have no vertical deflection and at least
75% of the barrel shall be visible in the horizontal direction;
E. In the event that lamping shows the pipe not laid true and to grade,
it shall be repaired and be lamped as necessary until the lamping
complies with these requirements.
In addition to the visual and lamping inspections, the Township
may employ the use of television cameras to inspect sewers after or
during construction. If defective workmanship or materials are found,
these shall be corrected and the cost of TV inspection paid for by
the applicant. No TV inspection costs shall be assessed against the
applicant if the workmanship and materials are found to be satisfactory.
Drop connections at manholes are shown on the standard details.
Concrete cradles over existing pipe shall be constructed where and
as directed by the engineer. All concrete work shall conform to the
requirements as set forth elsewhere herein.
When so required by the engineer, the contractor shall flush
such newly completed sewers as may be designated by the engineer,
in order to remove any foreign matter which may have accumulated therein
during construction. The contractor shall furnish all labor, material,
equipment and water necessary for flushing and shall provide for the
disposal of water used for flushing.