SITE INFORMATION AND CORRESPONDENCE FILE 1

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U1 HEALTH SERVIC:f' s SAN JOAQUIN COUNTY V. ENVIRONMENTAL HEALTH DIVISION Karen Furst, M.D., M.P.H., Health Officer 304 East Weber Avenue, Third Floor • Stockton, CA 95202 `'FORS 209/468-3420 FILE COPY BRETT HUNTER CHEVRON USA PRODUCTS COMPANY PO BOX 6004 JUL 221999 SAN RAMON CA 94583-0904 RE: CHEVRON STATION SITE CODE: 1039 139 S.CENTER STREET STOCKTON CA San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) and the Underground Storage Tank Cleanup Fund (USTCF) have recently reviewed the files associated with the site referenced above. Although groundwater monitoring is continuing, the plume is undefined. The . responsible parties at this site have failed to appropriately define (laterally and vertically) the soil and groundwater plume and are currently out of compliance with corrective action regulations. No fuel oxygenates (EPA Method 8260) analyses have been performed since June 10, 1998. Quarterly j Monitoring Report tabulated analytical data for the 3rd and 4`"quarters of 1998 and the I' quarter of 1999 suggest that Method 8260 analyses results are non-detect, however, the chain of custody for sampling indicate that the analyses was not requested. Please correct these reports and submit the amended data sets to PHS/EHD within 30 days from the date of this letter. You must sample and analyze groundwater from all monitor wells for oxygenates including MTBE, TAME, ETBE, DIPE, TBA, Ethanol, and Methanol until further written notice from PHS/EHD. Data from cumulative tables indicate that ground water in many monitor wells exceed the screened intervals. As such, the monitoring wells existing at this Underground Fuel Tank (UST) leak site are now inadequate and insufficient to properly locate and define the extent of contaminant distribution in the saturated zone. I The responsible party has submitted a workplan dated February 13, 1998 approved by PHS/EHD. The workplan has not been implemented to date. An amended workplan is now required. Boreholes shall be completed as monitoring wells constructed with appropriate screen intervals to locate and effectively define the plume (soil and groundwater). At least two boreholes should be continuously cored. One borehole should be located near known source areas (i.e., former tank cavity). All wells installed and surveyed shall be referenced to an appropriate and designated benchmark. Well screen intervals shall not exceed 20' in total length and should not create a potential vertical conduit. Report the results of your investigation to this agency within 30 days of completion of the approved scope of work. Please submit a well permit application with the amended workplan. PHS/EHD now directs the responsible party to submit the amended workplan, obtain approval, and implement the workplan within 90 calendar days from the date of this letter. I 1 A Division of San Joaquin County Heaith Care Services i