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CLEARWATER <br /> G R O U P, I N C <br /> Environmental Services <br /> Ms Lora Duncan April 9, 2001 <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 East Weber Avenue <br /> Stockton, CA 95202 <br /> Re Groundwater Monitoring Report - Second Quarter 2001 <br /> Ruiz Grocery <br /> 4491 West Durham Ferry Road, Tracy, CA <br /> Dear Ms Duncan, <br /> Introduction <br /> This report, prepared by Clearwater Group (Clearwater) on behalf of Mrs Stella Ruiz, presents the <br /> results of second quarter 2001 groundwater monitoring activities at Ruiz Grocery, 4491 West Durham <br /> Ferry Road, Tracy, California (Figure 1) <br /> Background <br /> Two gasoline USTs and dispensers were removed from the site in 1988 Seven monitoring wells (MW- <br /> 1 through MW-7), one groundwater recovery well (RW-1), four soil vapor extraction wells (VW-1 <br /> through VW-4), and two air sparge wells (SW-1 and SW-2) have been installed at the site (Table 1 and <br /> Figure 2) A domestic well (DW), screened an a deeper water bearing zone, also exists at the site The <br /> extent of soil and water contamination was delineated Based on historical investigation data, it was <br /> calculated that approximately 5,050 lbs (842 gals) of gasoline contaminants were present in the vadose <br /> zone prior to remediation Based on cumulative site data, Clearwater recommended construction of a <br /> remediation system consisting of combined groundwater and soil vapor extraction with air sparging <br /> The results of this work were presented in Clearwater's Problem Assessment Report, Feasibility Shidy, <br /> and Remedial Action Plan dated February 21, 1996 <br /> Following further d;scussion with the SJCPHS/EHD, Clearwater submitted a Revised Remedial Action <br /> Plan dated November 12, 1996, which recommended remediation by only soil vapor extraction and air <br /> sparging The SJCPHS/EHD approved this plan in a letter dated November 6, 1996 <br /> In late summer 1998, the SVE/AS remediation system was installed at the site Wells RW-1, MW-1, <br /> MW-2 and VW-1 through VW-4 were used to extract soil vapors, which were treated by an electric <br /> catalytic oxidizer An air blower was used to deliver air to the subsurface via wells SW-1 and SW-2 <br /> The system was operational from October 1998 to the end of September 1999, which resulted in 6,638 <br /> hours of total system operation Contaminant recovery from the subsurface was dramatic at first, <br /> 520 Third Street,Some 104 o Oakland,Cahforrua 94607 o Telephone 510-893-5160 o Fax 510-893-5947 <br />