Pumping test on the dewatering systems
(a) After the deep-well dewatering system is completely installed, a pumping test shall be made on the entire sysem by pumping all the wells at the same time at a constant pump speed or flow rate for each well, the pumping rate to be determined by the C. O.R. prior to the test. If the selected pumping rate lowers the water level in any well below the pump bowl, the engine speed shall be reduced or the discharge valve partially closed so that the water level in that well is not lowered below the pump bowl.
(b) This test, the first, shall be made prior to starting to unwater the Phase I excavation. The wells shall be pumped continuously for at least 24 hours and for not more than 48 hours as required by the C. O.R. The Contractor shall have previously installed the M piezometers around the perimeter of the excavation, the R, S, and T piezometers on lines out from the excavation, and provision has been made to measure the flow as shown on the drawings and specified herein. The C. O.R. will keep a systematic record of discharge throughout the test period and will record the water level in the piezometers and wells immediately prior to commencing the test and at certain intervals thereafter, The pumping test shall be conducted under the general direction of the C. O.R. with the Contractor being responsible for actual operation of the system.
(c) If an analysis of the pumping data by the Government indicates probable adequacy of the system, the Contractor may start unwatering the Phase I excavation while continuing to operate the dewatering well system so as to maintain the groundwater table in the deep sand formation, as indicated by the M piezometers installed around the top of the excavation, 3 to 5 feet or more below the water level in the excavation.
(d) After the Phase I excavation is unwatered, all wells shall be pumped at a constant rate to be prescribed by the C. O.R. for at least 48 hours and not more than 120 hours, as determined by the C. O.R., as a further check on the adequacy of the dewatering well system with the excavation unwatered. As during the first test, the rate of flow from each well and the entire system shall be measured throughout the test period, and the water level in the M, R, S, and T piezometers and in the dewatering wells will be measured and recorded at certain intervals during the test. The adequacy of the deep-well system will be evaluated on the basis of the pumping test made upon completion of unwatering of the excavation, for a Red River stage of elevation 60 feet. If at the end of the pumping test, an analysis of the data by the Contracting Officer or his C. O.R. indicates the system to be adequate, it will be approved; if the dewatering well system appears to be inadequate, for a design Red River stage of elevation 60 feet, the Contracting Officer will direct the Contractor to install additional dewatering wells, pumps, engines, and necessary pertinent piping and fittings for which he will be compensated as an extra.
(e) If it appears, while unwatering the Phase I excavation and the second pumping tests on the deep – well system, that the groundwater table in the top stratum has not been adequately lowered by the specified jet-eductors wells and pumping the deep-well system, the Contractor shall install whatever additional jet-eductor wells, pumps, and piping considered necessary by the C. O.R. for which he will be compensated as an extra.