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during this investigation are described in Appendix A. All work was conducted under the direct supervision of a State of California Professional Geologist. Copies of the well installation and destruction permits and encroachment permit are provided in Appendix B. Field Activities Soil Borings A Stratus geologist oversaw Gregg Drilling and Testing, Inc. of Martinez, California (C-57 4485165), complete drilling and associated well destruction and construction activities between April 10 and 14, 2006. The drilling of the well borings was completed using a limited access drilling rig equipped with 8-inch diameter hollow stem augers. Drilling locations are shown on Figure 2. The upper 5-feet of the MW-13 and MW-14 boreholes were advanced using air knife and vacuum extraction equipment, and/or hand tools, to minimize the possibility of damaging underground utilities. Soil samples were collected at select intervals during the advancement of the well borings using a California-type split-spoon sampler equipped with three precleaned brass tubes. The ends of the bottom-most, intact tube from each sample interval were lined with Teflon TM 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. Boring logs detailing soil stratigraphy are presented in Appendix C. 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 C. 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-13 and MW-14 were constructed using 2-inch diameter schedule 40 PVC well casing and 10 feet of 0.01-inch factory slotted well screen from approximately 105 to 115 feet bgs. A filter pack of Lonestarrm #2112 sand was placed in the annular space around the well from.the bottom of the casing to approximately 2 to 3 feet above the top of the well screen. Approximately 3 feet of bentonite was placed on top of the filter pack to provide a transition seal for the 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 locking cap was placed on the top of the well casing. WeR details acid DWR well completion reports for each monitoring well are included in Appendix C. K:\Apache Plastics\Reports\apache-sem-assessment report2006,doc Page 7 OTRATUS