[HISTORY: Adopted by the Board of Health of the Town of Dalton 8-21-1989. Amendments noted where applicable.]
Provided that the groundwater level is a minimum of two feet above the top of the pipe, leakage tests by infiltration shall be performed after the backfill has been placed. The Engineer shall determine if this condition exists. Infiltration tests shall be made when directed by the Engineer, and the length of line to be tested shall be not less than the length between adjacent manholes and not more than the total length of each size of pipe. The allowable infiltration shall be 100 gallons per inch of diameter per day per mile of pipe. Leakage between two adjacent manholes may be up to twice the amount above stated, provided that the average leakage for the total length of any size does not exceed the amount first stated and provided that there are no gushing or spurting leaks.
If an inspection of the completed sewer or any part thereof shows pipes or joints which allow noticeable infiltration of water, the defective work or material shall be replaced or repaired as directed.
Rates of infiltration shall be determined by means of V-notch weirs, pipe spigots, or by plugs in the end of the pipe to be provided and installed by the contractor in an approved manner and at such times and locations as may be directed by the Engineer.
If the groundwater table is not at a sufficient elevation to make the infiltration test acceptable, an exfiltration test must be performed. Water shall be used.
Leakage tests by exfiltration will be made on all pipe before or after backfilling at the discretion of the Engineer. The contractor will be required to test the first section of pipeline installed to demonstrate that the work conforms to these specifications. The initial test section shall be not less than the length of pipe between adjacent manholes and not more than 1,000 feet of pipeline. Testing of all pipe shall closely follow pipe laying. The length of the pipe to be tested shall be such that the head over the downstream crown is not more than six feet. The pipe shall be plugged by pneumatic bags or mechanical plugs in such a manner that the air can be released from the pipe while it is being filled with water. The test shall be continued for one hour, and provisions shall be made for measuring the amount of water required to maintain the water at a constant level during this period.
If any joint shows an appreciable amount of leakage, the jointing material shall be removed and the joint remade or replaced. If any pipe is defective, it shall be removed and replaced. If the quantity of water required to maintain a constant level in the pipe for one hour does not exceed 100 gallons per inch of diameter per day per mile of pipe and all the leakage is not confined to a few joints, the workmanship shall be considered satisfactory. If the amount of leakage indicates defective joints or broken pipe, they shall be corrected, and the line shall be retested.
In lieu of the water exfiltration test described above, and where applicable as determined by the Engineer, the contractor shall perform an air pressure test on the pipe. The pressure test section shall not be more than the length of pipe between adjacent manholes.
The contractor shall plug the pipe opening in the downstream manhole and place the pressure testing apparatus in the upstream manhole at the opening of the pipe section to be tested.
A pressure of 3.5 psi shall be reached in the test section. The valve on the pressure testing apparatus shall then be closed.
The minimum time duration permitted for a low-pressure exfiltration test between two consecutive manholes shall not be less than that shown in the table below. The prescribed pressure drop shall not exceed 0.5 psi for 3.5 to 3.0 psi in excess of the groundwater pressure above the top of the sewer. If the pipe section fails the test, the contractor shall locate the defects and repair or replace the defects at his expense. The pipe section shall then be retested until the allowable pressure drop is met.
Pipe deflection measured not less than 90 days after the backfill has been completed as specified shall not exceed 7.5%. The allowable minimum diameter shall be computed by multiplying the base inside diameter as listed in ASTM D3034 by 0.925.
Deflection shall be measured with a rigid mandrel (Go/NO/Go) device cylindrical in shape and constructed with a minimum of nine or ten evenly spaced arms or prongs. Drawings of the mandrel with complete dimensions shall be submitted to the Engineer for each diameter of pipe to be tested. The mandrel shall be hand pulled by the contractor through all sewer lines.
Any section of sewer not passing the mandrel shall be uncovered and the contractor shall replace the sewer at the contractor's expense.
At the conclusion of the work, the contractor shall thoroughly clean all of the new sewers by flushing with water or other means to remove all dirt, stones, pieces of wood, or other material which may have entered during the construction period. Debris cleaned from the lines shall be removed from the lowest manhole. If, after this cleaning any obstructions remain, they shall be removed.
Leakage tests shall be made by the contractor on each manhole and shall be observed by the Engineer. The test shall be the exfiltration test made as described below:
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 watertight. 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. At the end of this period, the manhole shall be refilled to the top of the cone, if necessary, and the measuring time of at least eight 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 twenty-four-hour 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 twenty-four-hour period.
If the manhole fails this requirement, but the leakage does not exceed three 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 three-gallon per vertical foot per day shall be cause for the rejection of the manhole. It shall be the contractor's responsibility to uncover the manhole as necessary and to disassemble, reconstruct or replace it as directed by the Engineer. The manhole shall then be retested as specified and to the satisfaction of the Engineer.
No adjustment in the leakage allowance will be made for unknown causes such as leaking plugs, absorptions, etc., i.e., it will be assumed that all loss of water during the test is a result of leaks through the 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.
In lieu of the water leakage test mentioned above, and where applicable as determined by the Engineer, the contractor shall perform a vacuum test on the manholes.
The vacuum test shall be done immediately after the complete assembly of the manhole (including filling liftholes, etc., as specified).
The contractor shall plug the pipe openings and place the vacuum testing apparatus in the manhole using a sixty-inch per pound torque to tighten the external clamps. The compression band shall then be inflated to seal the vacuum base. The vacuum pump shall be connected to the outlet port of the base with the valve open. A vacuum of 10 inches of Hg shall be drawn. The valve shall then be closed.
The test shall pass if the vacuum remains at 10 inches Hg or drops to nine inches Hg in a time greater than one minute. If the manhole fails the initial test, the contractor shall locate the leak and make the proper repairs. Leaks may be filled with a wet slurry of quick-setting material as approved by the Engineer.
All new manholes shall be thoroughly cleaned of all silt, debris and foreign matter of any kind, prior to final inspection.