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 ATSS Phone: 8-495-5600 TO: Antonia K. J. Vorster�JG` FROM: Camilla Williams Senior WRC Engineer Engineering Geologist DATE: 17 December 1991 SIGNATURE: SUBJECT: REVIEW OF WORK PLAN FOR NORTH BALLOON EXTRACTION WELLS, DEFENSE DISTRIBUTION REGION WEST (DORM), SHARPE SITE, SAW JOAQUIN COUNTY I have reviewed the Work Plan for the North Balloon Extraction Wells at the DDRW, Sharpe Site (Sharpe) . The Work Plan was submitted on 17 October 1991 by the U. S. Army Toxic and Hazardous Materials Agency (USATHAMA) and was prepared by Environmental Science and Engineering (ESE) . On 20 October 1991, I met with Mr. Craig MacPhee of USATHAMA, to discuss USATHAMA/ESE's plans for the North Balloon extraction well system prior to my review of the Plan. In addition, on 8 November 1991, 1 discussed my major concerns in a telephone conversation with Mr. MacPhee after I had completed my review of the report. Based on my conversations with Mr. MacPhee and my review of the Work Plan, there appeared to be differences in the extraction well design between what was discussed and what was written in the Plan. Mr. MacPhee indicated that Sharpe is committed to installing the extraction wells with screen lengths determined by lithology, whereas the Plan indicated that the extraction wells were to be installed with 10 foot screen lengths. On 13 November 1991, in another telephone conversation with Mr. MacPhee, he indicated that some of the wells would be installed with 20 foot screen lengths. As for the Work Plan itself, the strengths and weaknesses remain similar to other plans and reports prepared by USATHAMA/ESE. The strengths of the Work Plan are the summary tables and the figures which help to expedite the review of the Plan. The major weakness of the Work Plan is the lack of supporting rationale on the design of the extraction wells system. My overall comment on the Work Plan is that Sharpe needs to evaluate the advantages of the changes in design approach from the North Balloon Area and apply this information to the design of the Central Area. My specific concerns and comments are discussed below. Page 1-3. Table 1-1 is a well construction summary for all of the monitor and extraction wells at the site. The placement of this table in this Plan was an excellent idea and helped to expedite my review of the document. ESE should continue to provide summary graphics in Plans and reports. However, Table 1-1 should be amended to include the on-site supply wells. The construction summary table should be made as complete as possible. Page 2-5. The Work Plan states that the leading edge of the plume is defined by monitor well clusters 505 and 522 which have historically had volatile organic constituent (VOC) concentrations below the Primary Drinking Water Standard (DWS) . This statement is true with respect to the concentrations. However, it needs to be clarified that the edge of the plume (i .e. , the non-detect level ) actually extends beyond these wells because of the fact that VOCs are found in samples from these wells.