SITE INFORMATION AND CORRESPONDENCE

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Ms. Laurie Cotulla San Joaquin County Re: Genstar-Western Stone Site - Tracy August 6, 1991 Page 2 that you believe that MW4 is incapable of intercepting a hypothetical plume of groundwater contamination. The unusual non- dispersive attributes of this hypothetical plume did not seem to be taken into account in your letter of April 12, 1991, wherein you offered apparent contamination in the upgradient well MW1 as the rationale for the installation of an additional well. We are confident that MW4 is within the path of any plume of groundwater contamination that might have emanated from the former location of Tank #3. If necessary we can provide analytical and empirical data in defense of this conclusion, at which point we would request technical review by CRWQCB and/or SWRCB professional staff. Regarding the need for soil remediation we must reiterate our position that there is no evidence of appreciable soil contamination, groundwater has not been affected and there is no indication that groundwater will be affected. Therefore, remediation is not warranted. I apologize for the fact that the static water level shown on the well log for MW4 is incorrect. That measurement was made subsequent to well development before the water level had fully recovered and should not have appeared on the well log. The initial depth to water of 6 feet shown on the log is correct and represents the static level. This was confirmed one week after well installation on 5/30/90 when depth to water in MW4 was found to be 6. 19 feet below grade. The soil sample from this well at a depth of 5. 5 feet was, in fact, collected from the capillary fringe. I have no information in my files regarding the odor observed in the soil sample collected from the south end of Tank #3 on August 23, 1988. This observation is, of course, subjective in nature and should not weigh heavily in a decision making process unless supported by independent data, of which there are evidently none. Concerning the prior correspondence cited in your letter as reasons 3 and 4 for demanding soil remediation, I find it surprising that you would construe this to be evidence that soil contamination exists. These letters were preliminary in nature and were meant to lay the groundwork for excavation, should it prove necessary. Subsequent analysis of soil samples collected from the on-site borings/wells confirmed that no appreciable soil contamination existed and for this reason excavation was not conducted. WSTLRB06.WP