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09/17/2663 09:39 2098325'— WRIGHT ENVIRONMr --XL PAGE 02 <br /> Na/ <br /> Wright <br /> Environmental <br /> Services, Inc. <br /> 67 East lo'4 street,Tracy C.A,95376 <br /> September 12, 200Fh:209-833-0758—Fax:209-832-51.52 <br /> Trust of Mary Gardella <br /> 525 21111 Sheet Vitt <br /> Santa Cruz, Califomia 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 s) <br /> Dear Ms. Alexander, <br /> At the request of the County of San Joaquin Public Health Service Environment,il <br /> Health Division (PHS EHD) Wright Environmental has prepared this addendum lo <br /> the workplan to address PHS EHD comments. <br /> Soil Vapor Extraction Workplan (August 12, 2003) <br /> Soil vapor extraction (SVE) Inas been proposed as an interim remediation measura <br /> to clean up petroleum hydrocarbon impacted vadose zone soils at the subject sit.a <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 4.1 <br /> the subject site. The objective of the test is to assess the feasibility of SVE in <br /> removing chemicals of concern (COCl) that occur at depths of 12 to 35 feet in sits <br /> vadose zone soils. The COCs include total petroleum hydrocarbons as gasoline <br /> (TPH-G), benzene, toluene, ethyibenzene, and xylenes (STEX); 1,2 dichlcroethan� <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 silticlay 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 (f=igure 2- Site Plan). Shout 1 <br /> the test show SVE to be feasible these wells will be utilized for interim scI <br /> remediation. The proposed extraction well specifications are as follows.- <br /> Silt/clay <br /> ollows:Silt/clay zone - EW-1, 2-inch diameter, PVC Schedule 80, 0,020 slot size, screene.1 <br /> 12-27 feet, TO 30 ft. Well terminated within silt zone. <br /> Sandy zone , EW-2, 2-inch diameter, PVC Schedule 8o, 0.020 slot size, screene-1 <br /> 3r'-f'5 fee} 70 3r- 4 <br /> Revision 1 • Page i of a <br />