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a - 0 0 Foothill Sanitary Landfill -2— Module 2_Module LF-2 -Liner Performance Demonstration San Joaquin County The revision of the Evaluation Monitoring Plan, required in the Board's letter of 29 January 2001, was submitted on 24 May 2001. We have not received the Final Closure Plan with the cost details for Module LF-1 as of the date of this letter. Neither do we note reference to the closure of Module LF-1 in the liner performance demonstration report. During past conversations, County staff has mentioned the need for capacity(air space)between the old fill area and the proposed expansion area. Please elaborate on the County's plan to line the adjacent side-slope of the original Module LF-1 as part of the expansion of Module LF-2. For clarity, we propose the second module be labeled Module LF-2 to be consistent with WDRs. Evaluation Monitoring Plan (EMP) Based on the Board's previous letters and the fact that VOCs are"measurably significant" (Title 27 §20385) at the Foothill Landfill, it imperative the nature and extent of the impacted groundwater be delineated(Title 27 §20425) coupled with a closure design as the corrective action measure meeting the requirements of Title 27 §20430. Historically, dischargers have closed unlined waste management units as a corrective action measure, but failed to incorporate mitigation measures for increased VOCs in the vadose zone and groundwater. Upon closure of a site, VOCs are trapped under the impermeable cover and migrate to groundwater and the vadose zone causing an increase in concentrations of constituents of concern(COCs). Therefore, the Closure Plan and associated engineering feasibility study should incorporate measures to remediate the vadose zone and groundwater. The Water Quality Protection Standards must also be updated to compare background concentrations of inorganic COCs with downgradient water quality. Please ensure that the California Integrated Waste Management Board and the Local Enforcement Agency receive copies of the Final Closure Plan for review and approval. We realize that the County is pursuing an accelerated path to expanding the Foothill Landfill due to waste management issues. We propose to get back on track with ensuring compliance with Title 27 timelines in addition to responding to your request for the imminent expansion of the facility in 2003. In this regard,we expect that the County may want to revise the current EMP, at a minimum, due to the proposed expansion associated with Module LF-1 with regards to direct push method locations and additional groundwater monitoring well locations. Your current revised EMP proposes two direct push sampling locations 500 feet downgradient from MW-3. The plan does not include step-out and step- down criteria for this activity with regards to VOC concentrations relative to delineating the extent of the COCs. The sampling and analysis plan (SAP) should include,but not be limited to, sampling locations and depths, step-down and step-out criteria, sampling procedures, analytical methods,method detection limits, and listed COCs. Conversations with County staff revealed that there is a possibility that landfill gas and not leachate may be causing the problem. The EMP should, therefore, include an investigation of the vadose zone in this regard. Title 27 addresses gas control for closed landfills. For MSW landfills, the County must also comply with the additional notification and monitoring system requirements incorporated by reference into SWRCB Resolution No. 93-62, regarding notification and monitoring relative to offsite or potential off-site migration of waste constituents [see § 258.55(g)(1)(ii &iii) of 40CFR258].