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`9 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 Senior WRC tngineer DATE: 7 November 1991 FROM: Camilla Williams Engineering Geologist SIGNATURE: SUBJECT: REVIEW OF WORK PLAN FOR UNDERGROUND STORAGE TANK INVESTIGATION, DEFENSE DISTRIBUTION REGION WEST (DDRW), SHARPE SITE, SAN JOAQUIN COUNTY I have reviewed the Work Plan for Underground Storage Tank Investigation submitted on 2 October 1991 by the U. S. Army Toxic and Hazardous Materials Agency (USATHAMA) and prepared by Environmental Science and Engineering (ESE) for the DDRW, Sharpe Site (Sharpe). The strengths of this report were the tables and figures which summarized of the previous investigations performed at each of the tank sites. The summary tables helped to expedite the review of the Work Plan. On 15 and 18 October 1991, I discussed my concerns on the Work Plan with Mr. Craig MacPhee of USATHAMA. It is my understanding that not all of the tanks can be investigated at this time with the available funding and that future necessary tank investigations must be funded through a separate mechanism by Sharpe. USATHAMA has taken the approach to try to do a "complete" investigation on the selected tank sites rather than investigate all of the tank sites to fill data gaps. There are merits to both investigative approaches. However, ultimately Sharpe will need to investigate each tank site to determine if there have been any leaks, if ground water has been impacted and if soil and/or ground water remediation is necessary. My other two major concerns with the Work Plan were the placement of the six monitor wells and the cleanup levels. The placement of the wells was resolved with my discussions with Mr. MacPhee. It is my understanding that the some of the wells will be relocated based on my recommendations. My other outstanding concern is the proposed soil cleanup levels for diesel at 100 milligrams per liter (mg/kg) and for gasoline at 10 mg/kg. Because the ground water table at the site may be as shallow as five feet below some of the UGTs, these concentrations may not be acceptable. The existing soil data summarized in the Plan did not include the depths of the samples. These proposed levels may not be acceptable because if left in-place, these concentrations may pose a threat to water quality. The analytical data developed in this investigation should help to determine an acceptable cleanup level for these contaminants. Below are my detailed comments on the Plan. Page 2-1. The Plan states that the California Regional Water Quality Control Board (CRWQCB) published the Leaking Underground Fuel Tanks (LUFT) Manual. The LUFT Manual was published by the State Water Resources Control Board (State Board) and not the CRWQCB. The LUFT Manual is to be used as guidance for cleanups of contaminated soils only. The LUFT Manual presents several different approaches to determining the cleanup level for the soils. The LUFT Manual is not to be used if it is determined that ground water has been impacted by the leaking underground tank (UGT). The Central Valley Regional Board UGT staff recommend that the Tri -Regional Board Staff Recommendations for