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Chevron U S A , Inc January 7, 1992 02320 1978 Page 4 ' The aerated soil, shown by chemical analysis not to contain detectable levels of hydrocarbons, was backfilled into the pit as compacted fill beginning October 19, 1990 Fills were ' compacted using a vibratory sheepfoot roller and were tested at a maximum interval of two vertical feet to assure a minimum of 90 percent relative compaction The site was finish-graded to minimize any drainage to neighboring properties other than to the frontage road to the west The final inspection of the site was performed by Mr Harlan Knolls of SJCPHS on October 30, 1990 The details of aeration, backfilling, compaction, and compaction testing results are described in the copy of Dames & Moore's Soil Remediation report, dated November 30, 1990 ' (Appendix D) ' 3 4 GROUNDWATER MONITORING, SAMPLING, AND ANALYSIS The on-site monitoring wells were gauged and sampled once on August 9, 1989, and four times (quarterly) between November 18, 1990 and September 11, 1991 The samples were analyzed for BTEX and TPH-G No dissolved hydrocarbons were over detected in MW-2 and MW- 3 In a water sample collected from MW-1 on November 18, 1990 (approximately three weeks after completion of soil aeration and backfilling operations at the site) dissolved hydrocarbons were detected at concentrations of 600 parts per billion (ppb) TPH-G, and approximately 200 ppb total BTEX No dissolved hydrocarbons were detected in MW-1 before November 18, 1990 or during the three sampling rounds since then, indicating that the groundwater beneath the site has not ' been impacted by hydrocarbons ' The historical groundwater monitoring data and results of groundwater sample analyses are summarized in the latest Quarterly Groundwater Monitoring Report, prepared by Alton Geoscience, ' dated October 25, 1991 (Appendix E) 4 0 CONCLUSIONS This report summarizes the data in the attached documents which indicate that the ' groundwater beneath the site is not impacted by hydrocarbons, and that the soils beneath the site, which had been impacted by hydrocarbons, have been excavated, remediated, and backfilled Chemical analyses of sods treated by aeration indicate that hydrocarbon concentrations in the soils were reduced below detectable levels prior to backfilling Compaction of the backfilled sods to a minimum of 90 percent relative compaction and finish-grading of the site have eliminated migration pathways to groundwater for any undetected hydrocarbonsQ ❑�- , GROUNDWATER HWY89FR RPT ❑ TECHNOLOGY,INC