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Interim Investigation Report June 21, 1996 <br /> Chapin Brothers Automotive Stockton, California <br /> A-2.0 FIELD METHODS FOR WELL CONSTRUCTION <br /> The vapor wells VE-5 and VE-6, and the monitoring well MW5 were constructed using 4 and 2-in <br /> ' inner diameter PVC casing respectively No chemical cements, glues, or solvents were used in well <br /> construction The base of each well was fitted with a threaded PVC end cap, the top of each well was <br /> ' fitted with a watertight locking cap <br /> The screened portion of the vapor wells consist of factory-perforated PVC casing with 0 1-in-wide <br /> factory slots placed between approximately 5 ft and 25 ft below surface grade The screened portion of <br /> the monitoring well MW5 consist of factory perforated PVC casing with 0 02-in wide slots from 10 to 30 <br /> ' feet below surface grade The top of the slotted zones are several feet above the current groundwater <br /> surface elevation <br /> The annular spaces of the vapor wells were filled with 3/8-in pea gravel, the annular space of the <br /> monitoring well was filled with No 3 Monterey sand to approximately 1 ft above the top of the perforated <br /> ' casing A 24-in plug consisting of 3/8-in bentonite chips was placed above the sand/pea gravel and <br /> hydrated to restrict entry of cement into the sand pack The remaining annulus was backfilled with a <br /> mixture of neat cement and powdered bentonite (<5%) to grade <br /> A cast-iron utility box with steel apron was placed over the monitoring wells and set in concrete at <br /> 1 a level slightly above the surrounding grade These utility boxes have a water-resistant seal to protect <br /> against surface-water infiltration Each well head was fitted with a locking well cap to help protect the <br /> ' well These features discourage vandalism and reduce the possibility of accidental disturbance of the <br /> well <br /> �I <br /> 1 <br /> I <br /> LusH GEOSCIENCES <br />