ARCHIVED REPORTS_PRELIMINARY ASSESSMENT_SITE INVESTIGATION REPORT

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allowed to recover to at least 80 percent of the pre-purge level, and then the wells were sampled. During purging activities, the pH, temperature, and conductivity of the purged water was monitored and recorded at regular intervals to assess the influx of representative formation water into the well. Data collected prior to and during purging and sampling was recorded on monitoring well purge tables, wich are presented in Appendix C. The groundwater samples were analyzed for TPH j by EPA Method 8015M, BTEX by EPA Method 8020 and MTBE and the additional oxygenates (di-isopropyl ether, ethyl tertiary butyl ether, and tertiary amyl methyl ether) by EPA Method 8260. 3.4 Storage and Disposal of Wastes Drill cuttings and water collected during the soil drilling operation and groundwater sampling activities were stored in labeled, DOT-approved containers or lidded five-gallon buckets in secure areas at the Site. The contents of the containers and the dates of collection were clearly marked on appropriate labels. All equipment, decontamination materials, and disposable personal protective gear were also placed in appropriate containers. Once the hazardous characteristics of the materials were determined, they were disposed of appropriately. 3.5 Geophysical Survey Tear gas canisters have been reported by Stockton CA ARNG personnel to have been buried in the area between the CSMS and the AASF, in the location indicated on Figure 4. In accordance with the work plan, Versar conducted geophysical survey in the area outlined to assess the presence or absence of the reportedly buried tear gas canisters. The geophysical survey utilize a proton-precession magnetometer survey to locate magnetic anomalies. Identified anomalies were further evaluated with a metal detector and ground penetrating radar(GPR) to further define the area, depth, and surface shape of the anomaly. Two additional locations having surface relief anomalies identified by Stockton CA ARNG personnel were surveyed with the metal detector and the GPR in an attempt to assess the cause of the surface relief features. The two features comprise uplifted pavement in a vehicle storage area east of the CSMS. The pavement at one location appears to be raised approximately 18 inches, and is visibly raised over an area approximately eight feet in diameter. The second area is approximately 20 feet west northwest of the first, impacts an area of approximately 18 inches diameter, and is upraised approximately four inches. The locations of the two features are shown in Figure 4. 3.6 CSMS and OMS Clarifier Cleaning On March 30, 2000, Versar observed the removal of the clarifier contents at the CSMS. Laboratory analytical results from clarifier sampling were not available for inclusion in this report. 2187-01/3134-100/MAY26'00 9