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October 25, 1993 accompanied all of the samples to the laboratory Copies of these records are presented in Appendix B of this report 3.2 Monitoring Well Construction and Groundwater Sampling Monitoring wells were constructed in the borings using thread-jointed, 2-in inner diameter, Schedule 40 polyvinyl chloride (PVC) casing No chemical cements, glues, or solvents were used in well construction The base of each well was fitted with a threaded PVC end cap The screened portion of each well consists of factory-perforated PVC casing with 0 020-in wide slots The well screen extends from approximately 10 ft below the groundwater level, near the bottom of each boring, to approximately 5 ft above the groundwater surface for a total screen length of 15 ft This allows sampling near the air/water interface in the formation during seasonal fluctuation of groundwater Ievels 1 The annular space of each well was packed with No 3 cleaned and sorted sand to a point approximately 2 ft above the top of the perforated casing A 12-in to 24-m plug consisting of 3/8-m bentonite pellets was placed above the sand and hydrated to restrict cement from entering the sand pack The remaining annulus was backfilled with a mixture of neat cement and powdered bentonite (<5%) to grade An aluminum utility box with an aluminum apron was placed over each monitoring well and set in concrete at a level slightly above the surrounding grade The utility boxes have a watertight seal to restrict surface-water infiltration Each well head was fitted with an aluminum and brass locking well cap These features discourage vandalism and reduce the possibility of accidental disturbance of the well At the time of our initial site visit, the existing well was noted to have no watertight utility box It appeared as if oily surface nun off had reached the well casing and possibly entered the well At the request of the San Joaquin County Public Health Department, the existing well was refitted with a watertight utility box, as described above, and a locking aluminum and brass well cap Following initial water-level measurements using an electric water-level indicator, all r three wells were developed on September 28, 1993, by gentle surging and purging _ using a 2-In pneumatic well Pump Approximately 65 gallons of water was purged from AMI, 55 gallons from MW2, and 55 gallons from MW3 Each monitoring well was purged until there was less then 10 percent settleable solids Water purged from each well was placed into ROGER -5 - FDTT ASSOCIATES