SITE INFORMATION AND CORRESPONDENCE_1988-1991

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MEMORANDUM • CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 n ATSS Phone: 8-495-5600 TO: Antonia K. J. Vorster FROM: Camilla Williams Senior WRC Engineer ( ` Engineering Geologist DATE: 16 September 1991 SIGNATURE: Y�IiY�tfG�t/ i�� SUBJECT: REVIEW OF THE DRAFT GROUND WATER FEASIBILITY STUDY REPORT, DEFENSE DISTRIBUTION REGION WEST (DDRW), SHARPE SITE, SAN JOAQUIN COUNTY I have reviewed the Draft Ground Water Feasibility Study (FS) Report for the DDRW, Sharpe Site (Sharpe) . The Report was submitted on 18 June 1991 by the U. S. Army Toxic and Hazardous Materials Agency (USATHAMA) and was prepared by Environmental Science and Engineering, Inc. (ESE) . This FS is for ground water and has been separated from the FS for soils. The Report is intended to be a site wide FS for ground water and therefore, was to include the final remedy for the North and South Balloon Areas as well as the Central Area. The Draft FS Report also discussed the State applicable or relevant and appropriate requirements (ARARs) for each treatment alternative. The review of the State ARAR issues is under a separate memorandum. Although the Report is intended to be the site-wide FS for ground water, the technical proposals are primarily geared for the Central Area. As presented in the Report, the interim remedial measures (IRMs) , which were installed during the Remedial Investigation (RI) in the North and South Balloon Areas, will essentially remain the same entering into the final remedial design. This is a major concern because the North and South Balloon ground water extraction systems have not been demonstrated to have complete plume capture. (Sharpe's letter dated 1 May 1991 documents the lack of complete plume capture in all of the aquifer zones in the North and South Balloon Areas. ) If there is incomplete plume capture and the IRMs for the North and South Balloon IRMs become the final remedial action for ground water, regardless of the selected final treatment alternative, the volatile organic constituent (VOC) plumes will not be fully remediated at the Sharpe Site. I am concerned that the Draft Ground Water FS Report has only partially addressed our comments and concerns with two previous feeder secondary documents. Specifically, by letter dated 5 December 1991, we provided our review of the North Balloon Pumping Tests, Extraction Well Evaluation Draft Report and by letter dated 13 March 1991, we provided our review of the Focused Feasibility Study, Preliminary Draft. The Draft Ground Water FS Report has not addressed our concerns with respect to the design of the extraction systems. The design of the extraction systems is of paramount importance to the effectiveness of the overall ground water cleanup. All of the screened treatment alternatives, except the no action alternative, and the disposal alternatives are dependent on the extraction system. There is no evidence in the Draft FS Report that Sharpe has used the existing data base (from the automated system) to refine the existing extraction systems in the North and South Balloon Areas. The existing data base and performance data also appear not to have been used in the design of the extraction system for the Central Area. I am concerned that the Draft FS Report proposed the installation of three extraction wells near MW-505A, MW-407C and MW-524C. These areas of the aquifer are currently essentially uncontaminated. Installation of extraction wells at this location would only serve to exacerbate the extent of the VOC plumes. Therefore, we cannot agree to