SITE INFORMATION AND CORRESPONDENCE

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STATE OF CALIFORNIA- Environmental Proteo&lgency PETE WILSON, Governor CALIFORNIA REGIONAL WATER OLALI i Y CONTROL BOARD CENTRAL VALLEY REGION �� 3443 Routier Road, Suite A ``v��' Sacramento, CA 95827-3098V"�� PHONE: (916) 255-3000 �LFCWu�,<� DOD FAX: (916) 255-3052 Raw 23 November 1992 NOY 3 0 1992 ENaIPONMENTAL HEALTH PERM I'f/sERVIt;tb Mr. Jim Pinasco Site Mitigation Unit Department of Toxic Substances Control 10151 Croydon Way Sacramento, CA 95827-2106 Mr. Richard McJunkin Geologic Support Unit Department of Toxic Substances Control 10151 Croydon Way Sacramento, CA 95827-2106 DRAFT FINAL WELL EVALUATION AND ABANDONMENT ENGINEERING REPORT, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY We have received your 22 October 1992 review of the Draft Final Well Evaluation and Abandonment Engineering Report for DDRW, Tracy. The Draft Final Report was submitted on 1 October 1992. We have not received any comments from the Department of Toxic Substances Control (DTSC) on the Draft Well Evaluation and Abandonment Engineering Report, submitted on 27 July 1992. Your letter on the Draft Final Report causes us concern for two reasons. First, we disagree with some of your technical comments and therefore, we cannot concur with your recommendations for future well abandonments. Our areas of technical concern are discussed below. 1 . Comment No. 3 of your letter states that perforating permeable units prior to grouting wells during decommissioning is counter productive and recommends that aquitard units which have a microannul'u's, as revealed by geophysical logging, be perforated. We do not concur with the concept that placing a seal opposite a permeable zone is counter productive. We are also concerned that perforating opposite a pressure isolated impermeable zone for the purposes of remedial cementing (i .e. , squeezing or pressure grouting) , may run the risk of "fracturing" the formation or puts safety at risk due to unanticipated increases in pressure. Permeable areas tend to be conduits for cross- contamination and should therefore be sealed. We recommend that permeable areas, such as void spaces behind the casing or a gravel packed annulus, be the target for selecting the perforated intervals. 2. Comment No. 5 states that the grout used for the first lift was probably too thin because seven gallons of water were used for 94 pounds of Type I-II Portland Cement with 130 pounds of sand. Sand as an additive to cement has a slight increased water requirement in order for the slurry to remain pumpable. Considering the amount of sand that was added to the slurry, seven gallons of water per sack of cement may be within an appropriate mix water ratio range.