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dL CLEARWATEI G R 0 U P, I N C Environmental Services i QUARTERLY GROUNDWATER MONITORING REPORT FIRST QUARTER 1997 Ruiz Grocery,4491 West Durham Ferry Road,Tracy,CA February 12, 1997 BACKGROUND Two gasoline USTs and dispensers were removed from the site in 1988 Seven monitoring wells (MW-1 through MW-7), one groundwater recovery well (RW-1), three soil vapor extraction wells (VW-1 through VW-3), and two air sparge wells (SW-1 and SW-2) have been installed at the site A domestic i well—screened in a deeper water bearing zone, has also been installed at the site The extent of soil and water contamination has been delineated Pilot testing has been completed and a remedial action plan prepared based on results GROUNDWATER MONITORING FIELD ACTIVITIES Date of field activities 1/22/97 Wells monitored/sampled MW-1 to MW-7, and the domestic well Analytes tested TPHg, BTEX,and MTBE Analytical methods EPA Methods 8015/8020(modified) and 8260 for MTBE confirmation Laboratory American Environmental Network, Inc of Pleasant Hill, CA Remarks MW-4 was not gauged or sampled due to pooled surface water A depth to water measurement could not be obtained from the domestic well due 00 to wellhead plumbing GROUNDWATER MONITORING RESULTS Depth to water 1610 to 17 55 feet below ground surface(bgs) Flow direction/gradient Northeast at 0 0003 to 0 0017 ft/ft SPH - wells/thicknesses <0 01-foot thick sheen in MW-1 & MW-2 TPHg concentration range <50 µg/L(DW,MW-3,5,6, and 7)to 150,000 gg/L (MW-2) Benzene concentration range <0 5 µg/L (DW,MW-3,5, 6,and 7) to 1,200 µg/L (MW-2) MTBE concentration range <5 0 dig/L (DW,MW-3 and 6) to 1,300 Fig/L (MW-2) Remarks Groundwater flow direction (to the northeast) is perpendicular to that most commonly observed at the site (to the northwest) but generally consistent with previous measurements taken during the first quarter The extent of the contaminant plume remains delineated except in the vicinity of MW-4 with was not sampled The domestic well remains free of detectable contamination PROJECT STATUS Clearwater Group, Inc submitted a Revised Remedial Action Plan, letter dated November 12, 1996, which was approved by the San Joaquin County PHS/EHD in a letter dated November 6, 1996 Costs associated with completion of a remediation system specifications package, an authority to construct permit, and four additional quarters of groundwater monitoring was pre-approved by the USTCF in a letter dated January 8, 1997 Performance of these tasks is underway 520 Third Street,Suite 104 + Oakland,Calif orrua 94607 ® Telephone 510-893-5160 ® Fax 510-893-5947