SITE INFORMATION AND CORRESPONDENCE

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1_mw/ Ms. Laurie Cotulla February 24, 1992 Page 2 An addendum to the Draft Final Remediation Plan will be prepared upon the receipt of adequate data (laboratory results from the soil vapor extraction pilot test and a compilation of other site data pertaining to the to soil remediation). The County-imposed deadline for this document is March 31, 1992. If for any reason this deadline cannot be met, the County will be notified in writing prior to this date. A discussion of the down gradient Municipal Wells 2 and 10 was brought up by the County as to whether the wells are being sampled for gasoline related hydrocarbons. It is apparent by a letter (attached) dated January 30, 1992 by the State of California, Department of Health Services, Office of Drinking Water (DHS) by Mr. Homer Vaughn, that these wells are not being tested for gasoline hydrocarbons on a regular basis. ARCO has a down gradient monitoring well PR-1 which has shown not detectable (ND) laboratory results for gasoline related hydrocarbons since February 27, 1989. ARCO has demonstrated that gasoline hydrocarbons impacting groundwater on site is being captured through a groundwater remedial system. Confirmation of any down gradient migration of gasoline hydrocarbons are being continually verified quarterly by the ND laboratory results for monitoring well PR-1 for three years. ARCO agrees that it would be advisable for the City of Stockton to have these wells sampled for gasoline related hydrocarbons on a regular basis but only through the coordination of the appropriate state and local agencies. At this time, ARCO does not see the need for the County's request to coordinate sampling for the City of Stockton's wells. The January 30, 1992 letter from the DHS to the City of Stockton contains inaccurate information provided by the County. The letter states that the County had informed the DHS that the underground storage tanks (UST's) were removed at the ARCO service station as well as the adjacent Chevron service station because of a failed pressure test. The UST's at the ARCO service station were replaced in 1984 because of a broken leak detector, not a failed pressure test. ARCO does not know the history of the Chevron's UST's and do not know if, when or why their UST's were removed. Second, the DHS letter states that the County informed the DHS that soil saturated with gasoline exists at both sites. During the 1984 UST's replacement at ARCO, the soil affected by gasoline hydrocarbons in the UST's area was removed. There is no current information to conclude that soil beneath the ARCO site is saturated with gasoline hydrocarbons. This statement is based on the results of various sampling activities at the ARCO site. ARCO does not know the condition of soil beneath the Chevron site.