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c i v A S S O C I A T E S I N C contained calcium chloride and sodium dichromate chill water solution. Vaults 7 and 8 had 3,000 and 5,000-gallon capacities, respectively, and were located against the north wall of the processing f building (Figure 2). All of the vaults were taken out of service and cleaned in June 1990 Weiss Associates, April 1991). Several phases of subsurface oil and groundwater investigation ct property since December 1988. This work was Performed h by Weiss ave been oA Associatnducted at es (WA)he subjeof Emeryville,_ California. The threeound gr water monitoring wells were constructed to monitor the upper-most water-bearing zone, which was encountered at a depth of approximately 71 feet below in each boring. wells were screened at a minimum f 56 feet and at a maximum of 89 feet etbelow ground surface The (bgs). On January 31, 1991, after appropriately developing each well, WA personnel collected groundwater samples from each well. Samples collected from monitoring wells MW-I and MW-2 (adjacent to Vaults I and 6, respectively) wereanalyzed by GC/FID for ethylene and Propylene glycol. The water sample collected from MW-3, adjacent to Vault 8, was analyzed for total soluble chromium, sodium and calcium (EPA method 6010), hexavalent chromium (EPA method 7196) and chlorides (EPA method 325.2). All constituents detected were below the California maximum contaminant level (MCL) or below the EPA secondary standard (aesthetic); with the exception of total (0.10 milligrams per liter(mg/1)) and hexavalent(0.11 mg/1) chrome in well MW-3. In order to assess the validity of the MW-3 results for chrome species, a verification round of sampling was performed in August of 1991 by WA. Water samples were collected from monitoring well MW-3, and City wells WP-I and WP-2. Each sample was analyzed for total and hexavalent chromium by Clayton Environmental Consultants. The results indicated both City wells were below method detection limits for total (0.05 mg/1) and hexavalent (0.01 mg/1) chrome. However, total and hexavalent chrome levels of 0.07 mg/l were recorded for the MW-3 sample. In an effort to determine the, significance of the recorded concentration, a quarterly monitoring/sampling program was implemented to include all three shallow on-site monitoring wells in addition to the four adjacent City wells. . Historical monitoring data are included in Appendix A. 2.0 METHODS AND PROCEDURES Nine soil borings were advanced using truck mounted Geoprobe® narrow diameter, direct push technology. Drilling was conducted by Fisch Environmental, California License C57 #683865. . A field geologist will be present to log all soil samples. Descriptions of soil types encountered and sample collection intervals were recorded on boring logs. Soil samples were collected from each of the borings at depths of 20 feet and 40 feet bgs and were submitted for laboratory 4 analysis. w:lwordpro1625831reportslSuhsurf repwtdoc 2