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URS,l <br /> September 2, 2003 R[EC IM WIF D <br /> SEP 0 5 2003 <br /> Mr Michael Infurna ENVIRONMENT HEALTH 02130 <br /> San Joaquin County Environmental Health Department PERMIT/SERVICES 06 a4 <br /> 304 East Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Re: Vertical Flow Assessment Report <br /> ARCO Service Station No. 2130 <br /> 7906 North El Dorado Street,Stockton, Califorma <br /> Dear Mr Infurna <br /> URS Corporation Americas (URS) has prepared this report on behalf of Atlantic Richfield Company <br /> (ARCO) to present the results of vertical flow assessment conducted on July 23-24, 2003 This vertical <br /> assessment was conducted as a result of discussions with the State Water Resources Control Board <br /> (SWRCB) regarding the potential for vertical flow within groundwater monitoring and/or current or <br /> former site remediation wells See Figure I and 2 for Site Location and a Site Map, respectively The <br /> focus of the investigation was on wells with screen lengths of 30 feet or greater Wells VW-2 and VW- <br /> 10 at this site meet the screen length criteria In addition to VW-2 and VW-10, two additional <br /> monitoring wells screened over different depth intervals were studied The additional wells selected for <br /> this study, MW-2 and MW-5, have well screens less than 30 feet in length <br /> URS performed depth-discrete FloVisionT"' surveys of wells VW-2 and VW-10 to assess vertical flow <br /> URS performed down-hole camera surveys of wells MW-2 and MW-5 to assess well conditions <br /> SITE DESCRIPTION <br /> Currently, the site is operated as an ARCO service station with an AM/PM mini-mart The site is <br /> bounded by North El Dorado Street to the west and Hammer Lane to the south The majority of the site <br /> is paved <br /> Site structures include double-walled fiberglass gasoline underground storage tanks (UST's), two pump <br /> islands, and the AM/PM mini-mart During previous site work, 10 groundwater monitoring wells <br /> (MW-1 through MW-10), 12 soil vapor extraction wells (VW-1 through VW-12), I multi-level air <br /> sparging (AS) well (AS-1), 2 single level AS wells (AS-2 and AS-3), and 3 multi-level AS/groundwater <br /> monitoring wells (MS-1 through MS-3) have been installed at the site Two of the groundwater <br /> monitoring wells (MW-8 and MW-9) have been destroyed Currently, the site is on a quarterly <br /> groundwater monitoring schedule <br /> i� URS Corporation <br /> Crown Corporate Center <br /> { 2870 Gateway Oaks Drive Suite 300 <br /> Sacramento CA 95833 <br /> Tel 916 679 2000 <br /> Fax 916 679 2900 K 1WprocessU5 BP ARCM213OWertrcal Flow Study12130 Vgradient Report V2 doc <br />