allowed to rise above the bottom of the manhole, it shall be lowered for the duration
of the test.
The manhole shall be filled with water to the top of the cone section. If the
excavation has not been backfilled and observation indicates no visible leakage, that is,
no water visibly moving down the surface of the manhole, the manhole may be
considered to be satisfactorily water-tight. If the test, as described above, is
unsatisfactory as determined by the Engineer or if the manhole excavation has been
backfilled, the test shall be continued. A period of time may be permitted if the
Contractor so wishes, to allow for absorption by the manhole. At the end of this
period, the manhole shall be refilled to the top of the cone, if necessary, and a
measuring time of at least 8 hours begun. At the end of the test period, the manhole
shall be refilled to the top of the cone, measuring the volume of water added. This
amount shall be extrapolated to a 24-hour loss rate and the leakage determined on the
basis of depth. The leakage for each manhole shall not exceed one gallon per
vertical foot for a 24-hour period. If the manhole fails this requirement, but the
leakage does not exceed 3 gallons per vertical foot per day, repairs by approved
methods may be made as directed by the Engineer to bring the leakage within the
allowable rate of one gallon per foot per day. Leakage due to a defective section or
joint or exceeding the 3 gallon per vertical foot per day, shall be cause for rejection of
the manhole. It shall be the Contractor's responsibility to uncover the rejected
manhole as necessary and to disassemble, reconstruct or replace it as directed by the
Engineer. The manhole shall then be retested and, if satisfactory, interior joints shall be
filled and pointed.
No adjustment in the leakage allowance will be made for unknown causes such as
leaking plugs, absorption, etc. It shall be assumed that all loss of water during the
test is a result of leaks through joints or through the concrete. Furthermore, the
Contractor shall take any steps necessary to assure the Engineer that the water table is
below the bottom of the manhole throughout the test.
If the groundwater table is above the highest joint in the manhole, and there is no
leakage into the manhole, as determined by the Engineer, such a test can serve to
evaluate water-tightness of the manhole. However, if the Engineer is not satisfied
with the results, the Contractor shall lower the water table and carry out the test as
described hereinbefore.
3.03 CLEANING:
All new manholes shall be thoroughly cleaned of all silt, debris and foreign matter of any
kind, prior to final inspection.
END OF SECTION
2019 Sewer Replacement Project Precast Manholes and Catch Basins
Nashua, NH
02631-8
