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a , Ms. Wendy Arano Project No.: 791291 June 7, 2001 Page 3 The RWQCB approved corrective action plan for remediation of the release (e.g., the VOCs entrained in the LFG) consisted of the installation of the final cover to greatly limit infiltration into the refuse mass, and the installation of a LFG extraction system within the refuse mass. The final cover was placed on the landfill from November 1995 to May 1996. Since the placement of final cover, the number and the consistency of VOC detections have become more persistent at MW-5 and started at SB-1. It should be pointed out that SB-1 is located at the toe of refuse. This provides further evidence that LFG is the sole source of VOC migration from the landfill. The LFG extraction system was put into operation in May 2001. During the installation of the LFG wells the refuse was observed to be very dry, and no leachate was detected at the base of the landfill. This also provides further evidence that LFG is the sole source of VOC migration from the landfill. Because the refuse mass was very dry and no leachate was detected at the base of the landfill, there is little potential for fluid migration of contaminants from the landfill. In addition the suction vacuum of the LFG extraction wells will also act to remove unsaturated fluids from the refuse mass. This along with the installation of the final cover will virtually remove the future leachate production potential of the landfill. ADEQUACY OF EXISTING MONITORING SYSTEM The California Code of Regulations Title 27, Section 20415 General Water Quality Monitoring and System Requirements describe the requirements of a Groundwater Monitoring System for the following three types of programs: • Detection Monitoring Program(DMP)—Section 20415(b)(1)(B) • Evaluation Monitoring Program (EMP) - Section 20415(b)(1)(C) • Corrective Action Program(CAP) - Section 20415(b)(1)(D) The purpose of the DMP is to have a sufficient number of monitoring points to allow for the detection of a release from the landfill unit, and to provide the best assurance of the earliest possible detection of a release from the landfill unit. The existing shallow monitoring wells at the CHSL have functioned properly in accordance with the requirements of a DMP. The existing shallow monitoring wells detected the first signs \\SACRFPi\COMMON\sacDP\2001\PRJ\PJ7\791291.1 aa.doc (00006000)