SITE INFORMATION AND CORRESPONDENCE_FILE 2

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a + `ool v1 Jimco Truck Plaza Page 2 of 3 that a City of Ripon groundwater supply well is located 750 feet west of this site, additional assessment for MTBE may be necessary if significant concentrations of MTBE are confirmed. Cambria recommended that Olympian JV take ownership of wells MW-7 and MW-8 from Ripon Farm Services. EHD cannot assign ownership and responsibility for wells to other parties but can only direct responsible parties to properly investigate, characterize and monitor their plumes. Exchange of well ownership, etc. must be worked out between the parties involved and EHD urges all parties to work cooperatively on this issue. Cambria also proposed a simplified groundwater sampling schedule for future quarterly events. Because Cambria does not have ownership of MW-6, MW-7, and MW-8, or an access agreement to sample the wells at this time, EHD can only comment about the wells currently owned by Olympian JV. EHD approves sampling quarterly for total petroleum hydrocarbons as gasoline (TPH-g) and TPH-diesel (TPH-d) by Environmental Protection Agency (EPA) SW-846 method 8015B; benzene, toluene, ethyl benzene, and total xylenes, (BTEX) by EPA SW-846 method 8021B; and MTBE, ethyl tertiary-butyl ether (ETBE), tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), and tertiary-amyl methyl ether(TAME) by EPA SW-846 method 8260B for MW-1 through MW-3, MW-9, MW-10, and DW-1. However, because motor oil has been detected in MW-1, EHD directs you to continue sampling this well for motor oil and consider sampling additional nearby wells for motor oil. As stated previously by letter dated March 1, 2005, 1,2- dichloroethane (1,2-DCA) continues to be detected at high concentrations adjacent to your site at Ripon Farm Service located at 932 Frontage Road; therefore, EHD believes it would be prudent to continue sampling for 1,2-DCA in the domestic well, considering the close proximity of this well to the contaminated site. EHD agrees that MW-4 and MW-5 can be sampled annually starting in the first quarter of the year for TPH-g and TPH-d by EPA SW-846 method 8015B; and BTEX and MTBE by EPA SW-846 method 8021B, confirming any positive MTBE results by EPA SW-846 method 8260B. Cambria will continue monitoring groundwater levels in all wells on a quarterly basis. During review of Site Assessment Report and Quarterly Monitoring Report — Fourth Quarter 2005, it became apparent that the groundwater elevation contour maps submitted do not agree with the report narratives. Also, information submitted for soil borings B- 14, B-15, and B-16, collected in October 1996, and reported in narratives and tables for soil and groundwater in Site Assessment Report and Feasibility Test Report is incorrect.