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STAFF REPORT IN RESPONSE TO THE CENTRAL VALLEY REGIONAL WATER QUALITY CONTROL BOARD'S (CVRWQCB)TRANSNUTTAL OF ITS RESOLUTION NO. 5-00-213 TO THE STATE WATER RESOURCES CONTROL BOARD (SWRCB) ISSUE Should the Regional Water Quality Control Boards (RWQCB) allow the state and federal minimum prescriptive liner standard (single-composite liner) only in a case where the RWQCB determines that the liner design, in and of itself, will isolate waters of the State from the contained waste constituents for as long as a release from the municipal solid waste (MSW) landfill could pose a threat ? CONCLUSION No. The RWQCB should require a liner system design which, when installed under an effective construction quality assurance program, has a reasonable likelihood of providing effective waste containment during the landfill's operating life, during closure, and during at least the first 30 years of the post-closure maintenance period. The State and federal prescriptive composite liner design, or an equivalent alternative composite design, constitutes a minimum design, for this purpose, and the RWQCB should require a more stringent design in a case where it determines that the minimum design will not provide adequate protection to a given body of ground water. In all cases, a design's incremental additional cost, over that of the prescriptive design, should provide a commensurate additional benefit. Upon closure, the landfill's liner system may cease to be the principal containment feature of the landfill. The RWQCB should continue to regard a closed landfill's final cover as the main element of the landfill's containment system and should require its design, monitoring, and maintenance to reflect this special role. The State Water Resource Control Board (SWRCB) should make a practice of obtaining and. compiling upper-liner leakage rate data for MSW landfills, nationwide, which have double- composite liners. Such leakage rates will indicate the likely leakage rate of Californias sfn al composite lined landfills. The SWRCB may reconsider its minimum standard(single-composite liner) if the data indicate that the actual leakage rate is high enough to degrade the beneficial uses of underlying ground water. Once it matures, RWQCBs should improve the reliability of single-composite liner and cover systems requiring the use of currently-emerging technology that identifies the location of problem areas in a flexible plastic membrane. BACKGROUND At its regular August 4, 2000, meeting, the CVRWQCB considered approving the use of a single-composite liner(flexible plastic membrane over two feet of compacted clay) as a component of the.liner system for a proposed expansion of a landfill at the University of California at Davis (UCD Landfill). This is the minimum liner system design established for MSW landfills by both the federal regulations (40CFR258) and by SWRCB Resolution No. 93-62. During the meeting, the CVRWQCB received extensive verbal and written comments by Dr. G. Fred Lee. Dr. Lee apparently opposes the CVRWQCB's approving any liner system, unless the CVRWQCB makes a technically-based determination that such a system would provide complete containment for as long as the waste could pose a threat to ground water. In