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�-W <br /> Wright <br /> Environmental <br /> D3 SEP 11 Services, Inc. <br /> 67 Fast 1(r Street,Tracy CA 95376 <br /> Ph:209-833-0758—Fax: 209-832-5152 <br /> September 12, 2003 <br /> Trust of Mary Gardella <br /> 525 2nd Street <br /> Santa Cruz, California 95060 <br /> Attn.: Ms. Winifred Alexander <br /> Re: Addendum for Workplan for Soil Vapor Extraction Testing <br /> Stefanos Gasoline 1419 Charter Way, Stockton, CA <br /> Project No. 4233-3 (revision 1) <br /> Dear Ms. Alexander, <br /> At the request of the County of San Joaquin Public Health Service Environmental <br /> Health Division (PHS EHD) Wright Environmental has prepared this addendum to <br /> the workplan to address PHS EHD comments. <br /> Soil Vapor Extraction Workplan (August 12, 2003) <br /> Soil vapor extraction (SVE) has been proposed as an interim remediation measure <br /> to clean up petroleum hydrocarbon impacted vadose zone soils at the subject site <br /> (Figure 1- Location Map). This workplan describes the installation of extraction wells <br /> and soil vapor monitoring probes and the protocol for conducting a SVE pilot test at <br /> the subject site. The objective of the test is to assess the feasibility of SVE in <br /> removing chemicals of concern (COCs) that occur at depths of 12 to 35 feet in site <br /> vadose zone soils. The CDCs include total petroleum hydrocarbons as gasoline <br /> (TPH-G); benzene, toluene, ethylbenzene, and xylenes (BTEK); 1,2 dichioroethane <br /> (1,2 DCA) and several fuel oxygenates detected in site soil or ground water. <br /> SVE Well Construction Details <br /> Two extraction wells will be constructed to target the silt/clay and sandy zones that <br /> have been identified at different depths in the source area. The proposed wells will <br /> be located within the area of highest soil contamination (Figure 2- Site Plan). Should <br /> the test show SVE to be feasible these wells will be utilized for 'interim soil <br /> remediation. The proposed extraction well specifications are as follows: <br /> Silt/clay zone - EW-1, 2-inch diameter, PVC Schedule 80, 0.020 slot size, screened <br /> 12-27 feet, TD 30 ft. Well terminated within silt zone. <br /> Sandy zone }- EW-2, 2-inch diameter, PVC Schedule 80, 0.020 slot size, screened <br /> vw-.�ir, feet, I 3v fi. <br /> Revision 1 Page 1 of 3 <br />