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IF Wright <br />Environmental <br />Services, Inc. <br />Construction • Engineering • Remediation <br />July 17, 1998 <br />POSDEF Power Company, L.P. <br />Attn: Ed Stockton <br />2526 W. Washington Street <br />Stockton, CA 95203 <br />Re: Site Assessment <br />POSDEF Power Company - 2526 West Washington St., Stockton, CA <br />Wright Project No. 98-4535 <br />Dear Mr. Stockton, <br />At your request, Wright Environmental Services, Inc. (Wright) has prepared this workplan to sample soil <br />and groundwater adjacent to the existing underground waste oil storage tank (UST) at the above- <br />referenced site. The purpose of the assessment is to determine if soil and/or groundwater has been <br />impacted and to satisfy the requirements of the San Joaquin County Public Health Services Environmental <br />Health Division (PHS-EHD) for the in-place closure of the UST. <br />Background <br />In approximately 1987, POSDEF installed a 1,000 gallon underground waste oil storage tank to <br />temporarily store waste oil products that are generated in connection with the operation of the power plant <br />facilities. That underground tank is a double walled tank with primary and secondary containment. The <br />tank system also utilizes a monitoring system to detect potential releases of product into the environment. <br />That tank system is monitored on a continuing basis. <br />Based on information provided to Wright by POSDEF, water had recently appeared in the interstitial space <br />between the primary and secondary containment of the underground tank. Promptly upon discovering <br />those facts, POSDEF retained a California certified underground storage tank inspector. POSDEF <br />reviewed its underground tank monitoring records and concluded that there was no evidence of a loss of <br />product or a release. Pending the inspection and testing of the tank, POSDEF removed the contents of <br />the waste oil tank and took it out of service. <br />On or about April 18, 1998, the tank was inspected and tested and it was determined that the secondary <br />containment but not the primary containment had failed. It appeared that the source of the water in the <br />interstitial space resulted from the secondary containment failure and the high groundwater existing in that <br />area. Based on these findings, POSDEF has begun to formulate plans to abandon the tank in place. This <br />decision to abandon the tank in place rather than removing the tank has been made because the tank is <br />located in close proximity to a concrete pedestal which supports a large turbine. Tank removal operations <br />would significantly impact the power generating structure. <br />67 E. 10th Street • Tracy, CA 95376 <br />209.833.0758 • Fax 209.832.5152 <br />wright@inreach.com Lic. #651501 A-B HazMat <br />websit http://hotne.inreach.com/wright