SITE INFORMATION AND CORRESPONDENCE

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GEOMATRIX 3.1 SOIL BORING PROGRAM Under the direction of Radian personnel, Gregg Drilling and Testing. Inc. (Gregg), of Martinez. California, advanced six soil borings (SB-3 to SB-8) using direct-push technology (DPT) on July 14 and 15, 1998. Borings were advanced to delineate the extent of petroleum-affected soil within the area of former pump station operations at the site. Each DPT boring was advanced until refusal was encountered (26 to 27.5 feet bgs). Radian described soil samples in general conformance with the Unified Soil Classification System, as described in the American Society for Testing and Materials Standard D 2488-90. Soil boring logs, as completed by Radian. are presented in Appendix B. Soil samples were collected from the DPT borings at five-foot intervals between depths of 5 and 27.5 feet bgs. Samples were checked for visual (discoloration) and olfactory (odor) evidence of petroleum hydrocarbons, and headspace testing of soil vapors was performed. Samples retained for laboratory analysis were covered with Teflon`s end patches and sealed with airtight plastic caps, labeled and stored in an ice chest for laboratory transport. Completed chain-of-custody documentation accompanied the soil samples to the analytical laboratory. Soil borings subsequently were backfilled to grade with a cement-bentonite grout mixture. An SJC-EHD representative was present at the site on July 14, 1998, and approved the grouting of all of the borings. 3.2 GROUNDWATER MONITORING WELL INSTALLATION Under Radian's direction Gregg installed four groundwater monitoring wells (MW-1 through MW-4)between July 20 and 22, 1998 (Figure 3). The borings were advanced using a hollow- stem auger drill rig equipped with 8'/4-inch-diameter augers; the borings were continuously cored for lithologic control. Soil samples were obtained at five-foot intervals at depths ranging from 5 to 47 feet bgs as described in Section 3.1. Where the well bores where collocated with previously advanced borings (i.e.,MW-1/SB-8 and MW-4/SB-5), soil samples were not obtained for laboratory analyses at depths shallower than the terminal depth of the previous borings. Following completion of each boring, a monitoring well was constructed using 2-inch- diameter, Schedule 40 flush-threaded polyvinyl chloride(PVC)casing and factory-slotted well screen with 0.010-inch slots. The wells were screened across the water table between depths of 28 and 38 feet bgs. A sand filter pack(Lonestar#2116)was placed from the bottom of the well screen to 2 feet above the top of the well screen. After a 2-foot bentonite seal was placed above N\s#3ldeptdatalDoc_Safe15000s1501 t151 HRA 4t.dac 4