SITE INFORMATION AND CORRESPONDENCE_1994-1996

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9 LATE OF CALIFORNIA-ENVIRONMENTAL PFA�:;TION AGENCY _ _ PETE WILSON,GOVWW CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION ] 3443 ROUTIER ROAD,SUITE A SACRAMENTO,CA 95827.3098 PHONE: (916)255-3000 FAX: (916)255-3015 RECEIVED" � �r i I March 11, 1996 � `�C rrI I�rw V MAR 14 1996 ENVIRONMENTAL HEALTH Mr. Carlton Jordan PERMIT/SERVICES Shell Oil Company P.O.Box 4848 Anaheim,CA 92803 BULK TERMINAL, STOCKTON: REVIEW OF ANNUAL MONITORING REPORT FOR 1995 AND SITE STATUS (SAN JOAQUIN COUNTY, Case No. 3007) Staff has reviewed the 1995 Annual Monitoring Report,the Additional Site Assessment Report and the Third Quarter 1995 Monitoring Report for your bulk facility in Stockton. The reports were prepared by Pacific Environmental Group (PACIFIC) in compliance with Monitoring and Reporting Program 94-801. The reports show the existence of a hydrocarbon plume in the"deep" water-bearing zone at the Stockton facility. Hydrocarbon concentrations were detected in both the now-destroyed well, DW- S, and its replacement well, DW-2. The reports also show contamination in the Secondary Source Area 3 (SSA-3), to be lower in the new well,MW-28, than in the older well, MW-27, possibly indicating that the edge of the plume has been found. The soil vapor extraction(SVE) system that was scheduled for installation by 1 December 1994 under the terms of Cleanup and Abatement Order 94-705 has not been implemented,but the reports indicate that the installations were scheduled for completion in February 1996. Please inform us in writing when the installation is completed. Our review finds you in compliance with MRP 94-801. PACIFIC recommends reduction in monitoring frequency for certain wells on the site. As discussed in the attached staff memo (see memo, p.3), staff agrees that revision of the MRP should be considered. For the present, however, staff recommends only the reduction in frequency from semiannual to annual for wells MW-5 , -6, -7, and -8, providing the monitoring is done during the wet season (first or second quarter of the calendar year, but no later than April). We will add MW-28 and DW-2 to the quarterly monitoring program. We anticipate accomplishing this in time for your second 1996 quarterly monitoring round. Further revisions will be considered after better understanding of the SSA-3 and deep zone conditions are achieved,there has been time to assess the effects, if any, of the recent spill, and the combined effects of the SVE system and the ground water extraction have been observed.