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Taj Bahadori Page 2 of 8 August 30, 2018 The RWQCB's August 8, 2018 Review Response letter requires the County to submit a Revised Work Plan by August 30, 2018 to: 1) install background well MW -4A; 2) install a Point of Compliance well (MW -7) southeast of Module I near SG -6A; 3) submit a design of the proposed LFG extraction wells; and 4) provide a schedule for expansion of the LFG extraction system. The installation of the two new groundwater monitoring wells (MW -4A and MW -7) and initial sampling will be completed by the end of 2018. Installation of the new LFG extraction wells is part of the new enclosed flare project which is scheduled to be completed by July 2019. Approved portions of the July 16, 2018 Work Plan and a revised scope are provided below in this Revised Work Plan. Revised Work Plan Approved—Replacement of Background Well MW -4 The RWQCB stated in the Notice of Violation that the Detection Monitoring Program requires a background well that can provide consistent groundwater samples to determine if up -gradient water quality is changing. Background well MW -4 has been dry for two consecutive years. The last water level measurement taken in MW -4 was during the fourth quarter 2015 monitoring event. APTIM understands that the County will install replacement background well MW -4A adjacent to MW -4. MW -4A will be used to determine if up - gradient water quality is changing for the purpose of reassessment of calculated concentration limits for the down -gradient wells in the Detection Monitoring Program. Well Location - The location of replacement well MW -4A will be approximately 15 feet from the existing well MW -4, refer to Figure 1 for approximate location. The exact location will be determined in the field, based on a suitable location that is relatively level for the drill rig to set up on. The well location will be surveyed after installation. Exploration - The total depth of existing well MW -4 is 298 feet below top of casing (ft. btoc). The proposed initial exploration depth of drilling at replacement well MW -4A is 320 ft. below ground surface (bgs). The borehole for MW -4A will be advanced using the sonic drilling method. The intent of initially exploring to a depth of 320 ft. bgs is to determine the depth of first encountered groundwater (i.e., the water table) at the MW -4A location. The actual depth of the completed well will be based on encountering at least 15 ft. of water in MW -4A. The actual depth of MW -4A will be determined in the field and the borehole will be extended 15 feet below the encountered water table. 083018 FH-RWQCB-Revised Work Plan_Final.docx