SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Jerry Moore 5491 F Street, Banta, California Page 2 of 3 • A shift of groundwater flow direction does not mean that a plume formerly pushed toward the northeast would now be oriented toward the north — plume delineation toward the northeast is still a necessity. • The railroad company's requirement for a performance bond and the requirement for an insurance policy, given the nature of railroad operations and property, does not seem unreasonable. As these are necessary costs to install the approved well, the costs may be reimbursable by the State Water Board Cleanup Fund, although you should check with the Fund to be sure. The EHD will not waive installation of MW-15 based on this particular cost issue. • The AEI letter of 10 August 2005 and the railroad company's submittal of the requirements for an insurance policy and a performance bond to you indicates to the EHD that the railroad company is being cooperative with you and it appears that you mainly need to satisfy these requirements to obtain an access agreement to install and monitor MW-15. • A technical demonstration has not been presented to the EHD that the purposes for which installation of MW-15 was approved have been adequately met with existing wells and data. If you can provide a technical demonstration that the intended monitoring objectives of MW-15 are being met with current data, submit a report to the EHD by 15 May 2007 with the demonstration and the EHD will reconsider the matter, otherwise proceed with completing the arrangements with the railroad company and install MW-15. Include.in future quarterly reports updates on the status of your efforts to obtain the access agreement with the railroad company; note all actions taken by you to reach such agreement and all responses made by the railroad company during the reported quarter. The recent sensitive receptor survey findings should be incorporated into a site conceptual model (SCM) to demonstrate adequate protection of all sensitive receptors identified in the SRSR. The EHD described the components and uses of an SCM in the EHD letter dated 30 December 2003. To date the EHD has not received an SCM for your site. You are directed to prepare and submit an SCM to the EHD by 02 July 2007. The SCM should include maps and cross-sections that show that the potential receptors most likely to be impacted by your dissolved plume are adequately monitored through sentinel wells and/or direct domestic well sampling. The site investigation report provided the results from two cone penetration test borings (CPTs) advanced in November 2005. The two borings encountered predominantly coarse-grained soil (sand and gravel with some silt) from approximately 25 feet below surface grade (bsg) to total depth of 80 feet bsg, the upper 25 feet of the borings are characterized by finer-grained soil such as clayey silt, silty clay, silt, and silty sand. Most of the current groundwater monitoring wells bottom at 20 to 25 feet bsg in the finer- grained interval; only RW-2 appears to penetrate the uppermost portion of the coarser soil, bottoming at 30 feet bsg. The grab water samples collected from CPT1 between 30 and 58 feet bsg did not contain detectable concentrations of the analytes of concern, but the 78-foot sample contained 49 milligrams per liter (mg/1) chemical(s) quantified as motor oil (TPH-mo). All four water samples collected from CPT2 between 28 and 78 feet bsg were impacted by