ARCHIVED REPORTS_PRELIMINARY ASSESSMENT_SITE INVESTIGATION REPORT

Home Browse Search

. during well purging were recorded on field data sheets, copies of the monitoring well purge tables are presented in Appendix C. The samples were analyzed for TPH j; BTEX; and fuel oxygenates,including MTBE. MTBE was detected at a concentration of 0.5 ,ug/L in well MW- 2, BTEX and petroleum hydrocarbons were not detected. Benzene and total xylene concentrations of 1.1 kg/L and 1.7,ug/L were detected, respectively, in well MW-3, MTBE and petroleum hydrocarbons were not detected. The analytical results for this sampling and historical sampling events is presented as Table 3. 4.3 Storage and Disposal of Wastes Based on the analytical data collected during this investigation, soil and groundwater IDW generated during the investigation does not contain hazardous concentrations of the constituents of concern. Special handling and storage requirements for the IDW are not required. 4.4 Geophysical Survey Versar conducted a geophysical survey in vehicle and equipment storage areas to assess the presence or absence of the reportedly buried tear gas canisters. The geophysical survey utilized a proton-precession magnetometer survey to locate magnetic anomalies. Identified anomalies were further evaluated with a metal detector and GPR to further define the area, depth, and surface shape of the anomaly. Two areas were assessed, the unpaved,fenced enclosure due east of the . CA ARNG Armory building, and a paved area east of the CSMS building. The geophysical survey areas are indicated on Figure 4. One primary anomaly and two smaller anomalies were detected and further delineated and defined during the geophysical survey in the unpaved area east of the Armory. The primary anomaly could represent buried tear gas canisters. The two smaller anomalies are less likely to represent buried canisters. Two areas of uplifted asphaltic-concrete pavement in the second survey area, east of the CSMS, were surveyed using the metal detector and GPR, since the survey targets were self evident. Metal was not detected over the two targets. The GPR indicated an object was located immediately beneath the pavement at each location. The geophysical surveyor's report, including scale maps, is presented in Appendix E. 5.0 CONCLUSIONS The following conclusions are based on the results of our review of pertinent documents, interviews, field investigations, and laboratory analyses of collected soil, soil vapor, and groundwater sampes. The conclusions are presented for each investigated area of the Stockton CA ARNG facility. In general, minor amounts of petroleum hydrocarbons have impacted shallow soils in the AASF and CSMS areas, and higher concentrations of petroleum hydrocarbons have impacted deeper soil, and potentially groundwater, at the OMS. Elevated • concentrations of metals likely associated with Site activities have been detected in shallow soil 2187-01/3134-100/MAY2600 13