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URS <br /> . September 2, 2003 D <br /> S E P 0 5 2003 <br /> Mr Harlin Knoll ENVIRORMENT HEALTH 02093 <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 2093 <br /> 3425 Tracy Boulevard,Tracy, California <br /> Dear Mr Knoll <br /> URS Corporation Americas (URS), has prepared this report on behalf of Atlantic Richfield Company <br /> (ARCO) to present the results of the vertical flow assessment conducted on July 23, 2003 This <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 1 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 Well TEX-1 at this site <br /> meets the screen length criteria In addition to Well TEX-1, three additional monitoring wells screened <br /> over different depth intervals were studied The three additional wells selected for this study, ATR-2, <br /> ATR-7, and ATR-8, have well screens less than 30 feet in length <br /> URS performed a depth-discrete FloVisionTM survey of wells ATR-2 and TEX-1 to assess vertical flow <br /> URS performed down-hole camera surveys of wells ATR-7 and ATR-8 to assess well conditions <br /> SITE DESCRIPTION <br /> Currently, the site is operated as an ARCO service station with an AMVPM mint-mart The site is <br /> bounded by commercial property to the west and north, Tracy Boulevard to the east, and West Clover <br /> Road to the South The majority of the site is paved <br /> Site structures include double-walled fiberglass gasoline underground storage tanks (USTs), two pump <br /> islands, and the AMIPM mini-mart During previous site work, 12 groundwater monitoring wells <br /> (ATR-1 through ATR-12), 7 soil vapor extraction wells (VES-1 through VES-7), 3 air sparging (AS) <br /> wells (S-1 through S-3), 1 groundwater monitoring/AS well (SMW-1), and one groundwater extraction <br /> well (TEX-1) have been installed at the site Currently, the site is on a quarterly groundwater <br /> monitoring schedule Soil vapor extraction and air sparging is ongoing at the site <br /> SCOPE OF WORK <br /> URS conducted vertical groundwater flow on wells ATR-2 and TEX-1 and well condition assessments <br /> on wells ATR-7 and ATR-8 Welenco, Inc , of Bakersfield, California was subcontracted to perform the <br /> depth-discrete vertical flow analysts for wells ATR-2 and TEX-1 with a FloVisionT" flowmeter probe <br /> The F1oVisionT"A apparatus indicated the direction and flux of groundwater movement within the wells <br /> 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 ARC01020931Verttcal Flow Study12093 Vgradient Report V2 doe <br />