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MEMORANDUM K CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 ' Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Wendy L. Cohen FROM: Philip S. Isorena k Senior Engineer Associate Engineer 3 DATE: 7 April 1993 SIGNATURE: JJib M` SUBJECT: PROBLEM ASSESSMENT REPORT REVIEW, BP OIL COMPANY, STOCKTON TERMINAL, SAN JOAQUIN COUNTY I have reviewed RESNA's 29 March 1993 problem assessment report for the BP Oil Bulk Fuel Terminal in Stockton. My comments follow. 1. Figures and tables were interspersed with the text instead of being placed in the appendix. This made reading and referencing to the figures and tables , cumbersome. :r 2. The objective of the investigation was to define the lateral and vertical extent of soil and ground water contamination. The report did not state if this objective was achieved. 3. Soil and ground water analytical results were merely presented but not interpreted. For example, the significance of detecting benzene and TP.HG, albeit at low levels, at SB-9 and MW-9, respectively, was not stated. SB-9 and MW-9 are hydraulically downgradient from MW-2 and MW-1 , respectively. Furthermore, the report did not discuss the approximately 20-fold increase in benzene concentration at MW-2 between the December 1992 and March 1993 sampling F" events. In fact, this trend is also apparent in MWs 1-4 yet no explanation was provided. 4. The report states that historically the direction of ground water flow has been to the southwest and west. The March 1993 ground water contour map confirms the westerly component of the flow but it also shows a slight northwesterly flow from MW-3 to MW-8 (see attached Figure 5). In the vicinity of MW-4 the ground water flow is to the west. Nonetheless, MW-7 was placed cross-gradient ftJ from MW-4. In the vicinity of MW-9 the ground water flows almost directly north towards MW-1 thence to MW-8. However, if the predominant flow is southwest and west, there is no well downgradient of MW-1. MWs 8 and 9 are unlikely to catch the ground water flowing in the direction of MW 1. A well placed at SB-7 or in its immediate vicinity would have fulfilled this need. 5. Recommendations for future course of actions were not included in the report.