SITE INFORMATION AND CORRESPONDENCE

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Kwikee Market 2081 Country Club Blvd., Stockton page 2 With the repeat of groundwater flow direction to the west and the rise in groundwater contamination in KF-3, EHD is concerned that residual petroleum contamination remains in the shallow subsurface at the former UST area and is continuing to impact the aquifer. In researching data from monitoring well KF-3, EHD was unable to locate any soil data that should have been collected at the time of its installation. The elevated level of petroleum detected in the soil samples from beneath the USTs removed in March 1998 (sample "ES-1" at 13 feet below ground surface ['bgs]) is up gradient to KF-3. Subsurface investigations conducted since the USTs were removed have not confirmed the soil status at this depth. The Geoprobe investigation during May 1998 placed one probe in the pit and collected soil samples starting at 20' bgs. The status of the shallow soil up gradient of KF-3 in unresolved. Two Chevron monitoring wells (MW-6 & 7) are located just west of Kwikee market. Chevron monitoring well MW-7 is approximately 50' west/northwest of KF-3 and detected 200 ug/I of TPHg and <2.5 ug/I of MtBE by EPA Method 8260B at the November 2001 sampling event. Chevron monitoring well MW-6, approximately 25' west/southwest of KF-3 detected TPI-Ig in the groundwater at 2,000 ug/I and MtBE at 80 ug/l, also by 8260B. Since the levels of TPI-Ig are higher in the monitoring wells on the Chevron site, a valid argument may be made that some TPI-Ig contamination is emanating from the Chevron site. But with the lower concentration of MtBE (140 ug/1) detected in the groundwater samples from Kwikee monitoring well KF-3, (up gradient) an argument can be made that MtBE isn't increasing in concentration as is travels away from Kwikee and that the source for this constituent is still present at the Kwikee site. This pattern of increasing concentrations of MtBE and TPI-Ig in KF-3 samples as the groundwater flows to the west doesn't support your consultant's conclusion that Chevron is responsible for all the groundwater contamination at Kwikee. With these concerns, EHD doesn't approve your request that"the site should be closed with no further investigation or remediation". Further groundwater monitoring and sampling is required. Please schedule an appointment with Michael Infurna to conduct at least two consecutive quarterly monitoring events under his witness starting First Quarter- 2002. Be prepared to include all constituents of concern and utilize EPA Methodology discussed above. The report of the first monitoring event should be submitted to EHD before the next sampling event is held and with adequate time for EHD to evaluate and comment as needed. You may contact Michael Infurna at (209) 468-3454 should you have any questions and schedule any field activities. Donna Heran, REHS, Director Environ ental Health Division ZL�G�� 4 —�� A- Uec� Michael J. Infurna Jr., enior REHS Margaret Lagorio, REHS LOP / Site Mitigation Unit IV Supervisor MI/ c: CVRWQCB— Marty Hartzell, Sacramento. c: SWRCB—CUF— Mark Owens, Sacramento. c: Upgradient Consulting —V. Cherven PO Box 8002 Stockton, 95208.