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STATE OF CALIFORNIA • • GEORGE DEUKMEJIAN. Gover <br /> a t <br /> CA)_IEORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL. VALLEY REGION <br /> 3443 ROUTIER ROAD, SUITE A <br /> SACRAMENTO, CA 95827-3098 <br /> APR .27 ,s''' <br /> 24 April 1990 LIQ ROjvMENTAL H FA <br /> 1 <br /> Thi <br /> Mr. Richard A. Ragaini , Chief <br /> University of California <br /> Environmental Protection Department <br /> Lawrence L i ve,iiiore National Lab—tory <br /> Post Office Box 808 <br /> Livermore, CA 94550 <br /> SUBCHAPTER 15 COMPLIANCE REVIEW, CLOSURE AND POST-CLOSURE PLANS FOR PITS 1 AND 7, <br /> UNIVERSITY OF CALIFORNIA, LAWRENCE LIVERMORE NATIONAL LABORATORY SITE 300, SAN <br /> JOAQUIN COUNTY - CASE NO. 2677 <br /> We have reviewed the 17 November 1989 "Response to Comments by the California <br /> Regional Water Quality Control Board on Closure and Post-Closure Ptans for <br /> Landfill Pits 1 and 7" (Subchapter 15 response) and the 5 February 1990 revised <br /> "Resource Conservation and Recovery Act RCRA Closure and Post-Closure Plans <br /> for a dfill Pits 1 and 7 revised CP To assist in this review, we have used <br /> o L n ( ) <br /> data and hydrogeologic analyses presented in the 17 November 1989 "Remedial <br /> Investigation and Feasibility Study for the Pit 7 Complex. " <br /> LLNL' s proposed engineered alternative to the Subchapter 15 siting criteria and <br /> construction standards for Class I landfills will likely achieve the performance <br /> goals of these requirements, which are to prevent the landfill from releasing <br /> waste constituents to surface or ground water. LLNL has demonstrated that <br /> removing the waste to retrofit a liner would be impractical . We also agree with <br /> LLNL ' s conclusion that the interceptor drainage ditch and trenches cut to bedrock <br /> are better controls for the ground water laterally migrating along the perching <br /> horizon than would be grout curtains or cutoff walls, behind which excessive head <br /> could develop. The final landfill cover designs specified in the CP comply with <br /> Subchapter 15 §2581. <br /> We hereby approve closure and post-closure of Pits 1 and 7 in accordance with <br /> analyses and designs included in the revised CP and the Subchapter 15 response, <br /> with the following conditions. LLNL shall further detail the interceptor trench <br /> designs by providing additional cross-sectional drawings showing the depths to <br /> bedrock and specifying associated trench design details. Please submit the <br /> drawings and a time schedule for the closure by 23 May 1990. Also, please notify <br />