SITE INFORMATION AND CORRESPONDENCE FILE 1

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Voice 209 468-0337 Fax 209-468-3433 San JoaquinCounty Environmental Fcaix To: Roger Hoff more From: Mary Meays, Senior REHS Fax: (916) 858-23S5 Pages: 3 Phone: (916)858-2350 Date: October 3, 1997 Re: 139 South Center CC: Brett Hunter(510) 842-8370 CC: Jim Kleinfelder(209) 465-8773 Roger, I have enclosed copies of the drilling permits, #013841 and #013842, issued on October 3, 1997 for work which is scheduled for October 6, 1997. Additional permits were requested since the drilling contractor, to whom the permits are issued, was changed. Unfortunately, the additional permits were issued prior to receiving your telephone call indicating that the on site work would be performed by Mitchell Drilling instead of the recently permitted Spectrum Drilling. Both contractors will be drilling on October 6, 1997, Mitchell on site and Spectrum off site. A vapor extraction well with 15 feet of screen will be installed in the location of soil boring SB10 and drilled to a proposed maximum depth of 27 feet below ground surface (bgs) which is the reported most recent depth to groundwater. Please note that PHS/EHD has not yet received the report of the May 1997 monitoring results. Please note that the vertical extent of the soil contamination was not characterized before the groundwater table has risen. Significant soil contamination was detected at 43 feet bgs in soil boring SB4 of 15,000 ppm TPH-gas and 160 ppm benzene. The proposed boring which will be converted into a vapor extraction well will not provide information to determine the vertical extent of the soil contamination. The off site well will be installed by Spectrum Drilling in Caltrans right of way and according to the Pacific Field and Laboratory Procedures, the well will be constructed with 15 to 20 feet of screened casing placed at the bottom of the borehole. According to work plan approval you shall contact me following the completion of field activities to discuss which soil samples will undergo analysis. It can be inferred from the Pacific correspondence dated October 1, 1997 that evaluation of active remedial alternatives for the contaminated groundwater will be included in the Corrective Action Plan due December 30, 1997. Soil vapor extraction is a remedial alternative wah both vadose and groundwater zone applications. Thank you. Please call if you have questions.