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�1{ Y <br /> CLEARWATER <br /> G R O U P, I N C <br /> 01 <br /> Environment.! Services <br /> ti <br /> Ms Lori Duncan August 3, 200b e^ <br /> San Joaquin County Public Health Services / Environmental Health Division <br /> 304 East Weber Avenue <br /> Stockton, CA 95202 <br /> Re Groundwater Monitoring Report-Third Quarter 2000 <br /> Ruiz Grocery, 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 third quarter 2000 groundwater monitoring activities at Ruiz Grocery, 4491 West Durham <br /> Ferry Road, Tracy, California (Figure 1) This sampling event is the fourth quarter of verification <br /> monitoring following remediation system shut-down in October 1999 <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 A domestic <br /> well (DW), screened in a deeper water bearing zone, also exists at the site The extent of soil and water <br /> contamination was delineated Based on historical investigation data, it was calculated that <br /> approximately 5,050 lbs (842 gals) of gasoline contaminants were present in the vadose zone prior to <br /> remediation Based on cumulative site data, Clearwater recommended construction of a remediation <br /> system consisting of combined groundwater and soil vapor extraction with air sparging The results of <br /> this work were presented in Clearwater's Problem Assessment Report, Feasibility Study, and Remedial <br /> Action Plan dated February 21, 1996 <br /> Following further discussion 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 /> averaging approximately 2 lbs/hr during the first five months of operation However, by July 1999, <br /> contaminant recovery rates had decreased to approximately 0 02 lbs/hr For the last three months of <br /> 520 Third Street,Suite 104 o Oakland,Califorrua 94607 o Telephone 510-893-5160 o Fax 510-893-5947 <br />