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Mr. Nuel Henderson, Jr., SJCEHD June 27, 2005 Former Apache Plastics Facility, Stockton, CA Project 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 #710079), 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 %-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 MW4, 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 0.024nch 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 #3 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 K:Wpache PlasticslReportsWpache-well-install-destruct-letter report.doc