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San Joann County Environmental Health Division June 20, 2008 Page 6 purging and subsequent groundwater sample collection will be performed using a peristaltic pump fitted with disposable tubing, with the groundwater sample collected into laboratory-supplied containers. The turbid groundwater will be field-filtered through 0.45-micron filters prior to sample preservation for metals analysis. Each sample container will be labeled with the sample location ID, placed in a resealable plastic bag, and stored in a cooler contain ice. The investigation derived waste (IDW) generated from the field sampling activities will include soil cuttings, purge water, and equipment decontamination water. The IDW will be stored in labeled 55-gallon drums, with soil stored separated from water. It is anticipated that one soil drum and two water drums will be generated during this investigation. The analytical results obtained will be used to characterize the drummed IDW for proper disposal, currently anticipated to be designated as California Class II waste. The drums will be securely stored at the Westway facility prior to off-site disposal. The disposable field sampling equipment (e.g., nitrile gloves, peristaltic pump tubing) will be collected in plastic garbage bags and properly disposed. Task 3. Geophysical Survey The 1991 Phase II investigation identified the presence of a subsurface magnetic anomaly. In addition, the 2007 Phase I ESA included historical aerial photographs apparently showing two manmade features, with one situated in the location identified to have the magnetic anomaly. The geophysical survey will consist of performing a magnetic survey of the entire 6.3-acre parcel using a Geomterics magnetic gradiometer. The survey will focus on the potential locations identified in Figure 1 by conducting 10 feet parallel traverses across the eastern half of the Site, while 20 feet parallel traverses will be performed across the western half of the Site to asses if other subsurface magnetic anomalies exist. Tighter grids may be used near detected anomalies. The magnetic data acquisition will be conducted by a California Professional Geophysicist. The results of the geophysical survey will be reviewed to determine if further investigatory measures are warranted. Should the survey identify the presence of significant magnetic anomalies, a backhoe may be used to pothole at the suspected locations. The potholing is not expected to encounter groundwater and the removed soil will be placed back into the pothole upon completing the investigation of each suspected location. Task 4. Reporting BC will prepare a report documenting the results of the Phase II investigation of the Site. This report will include a narrative summary of the field activities, tabulated analytical data, sample location maps, the results of the geophysical survey and copies of the analytical laboratory reports. The reported analytical results will be compared against available regulatory action levels to assess the data. P:11350001135531-U3BDG Phase II InvesTinal DocumentsIFinal REG Phase II Work Plan 052808.docIdt