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Mr Nuel Henderson,Jr, SJCEHD June 27,2005 } • Former Apache Plastics Facility, Stockton, CA Protect No 2005-2050-01 Well Installation and Destruction Letter Report Page 2 Soil Borings A Stratus geologist oversaw Woodward Drilling Company of Rio Vista, California (C-57 4710079), complete onsite drilling, well installation, and well destruction activities between March 29 and 31, 2004 The drilling was completed using a truck mounted drilling rig equipped with 8-inch diameter hollow stem augers Locations of all newly installed or re- constructed wells are shown on Figure 2 The initial 5 feet of each boring were advanced with hand tools to reduce the possibility of damaging underground utilities Soil samples were collected at select intervals using a California-type split-spoon sampler equipped with three precleaned brass tubes Given the proximity of well boring MW-18 to previously sampled borings MW-2 and MW-8, soil samples were not collected Boring MW-15 was sampled from approximately 0 to 60 feet below ground surface (bgs), boring MW-16 was sampled from approximately 65 to 90 feet bgs, and boring MW-17 was sampled from approximately 93 to 120 feet bgs The ends of the bottom-most, intact tube from each sample interval were lined with Teflon"m sheets, capped, and sealed Each sample was labeled, placed in a resealable plastic bag, and stored in an ice-chilled cooler Strict chain-of-custody procedures were followed from the time the samples were collected until the time the samples were relinquished to the laboratory Soils were classified on-site using the Unified Soil Classification System Given the close proximity of borings MW-15, MW-16, and MW-17, a single boring log depicting soil conditions at the well cluster location was generated and is presented in Appendix A Additional soil from each sampled interval was placed and sealed in plastic bags to allow the accumulation of volatile organic compound (VOC) vapors within the airspace in the bags A portable photo-ionization detector (PID) was used to measure VOC concentrations from each sample, in parts per million by volume (ppmv) PID results are included on the boring logs presented in Appendix A PID results were also used to evaluate which soil samples should be sent to the laboratory for chemical analysis Monitoring Well Installation Monitoring wells MW-15 through MW-18 were constructed using 2-inch diameter schedule 40 PVC well casing and 0 02-inch diameter factory slotted well screen Well MW-15 was screened from approximately 40 to 60 feet bgs, wells MW-16 and MW-18 were screened from approximately 85 to 90 feet bgs, and well MW-17 was screened from approximately 104 to 119 feet bgs A filter pack of LonestarTM #3i graded sand was placed in the annular space around the well from the bottom of the casing to approximately 2 feet above the top of the well screen Bentonite was placed on top of the filter pack to provide a transition seal for each well The remaining annular space around the well casing was backfilled to surface grade with neat cement A traffic rated vault box was placed over the wells, and a watertight �l K lApache Plastjcs\Reports\Apache-well install-destruct letter report doe