COMPLIANCE INFO_JTD 2/11/26 - Laserfiche WebLink

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Preliminary Closure and Postclosure Maintenance Plan 2-4 Department of Public Works/Solid Waste North County Recycling Center and Sanitary Landfill County of San Joaquin 2.4 Decommissioning of Environmental Control Systems Internal soil gas wells SG-5, -6, and -7 will be decommissioned prior to the extension of the liner into that area and overfilling with refuse, and will not be part of closure activity or closure costs. Decommissioning will be as approved by the applicable regulatory agencies. At this time, it is anticipated that the boreholes will be re-drilled and the resulting hole filled with concrete slurry or other approved fluid. Single-probe soil gas well SG-4 will be retained for VOC sampling, if required. All other environmental control systems will remain operable during closure and in the postclosure period. These include: groundwater monitoring, leachate collection, landfill gas migration monitoring, landfill gas collection and control, and vadose zone monitoring and surface water monitoring. The landfill gas (LFG) control system will be expanded to include the new lined areas as they are constructed. 2.5 Description of Closure Activities Sections 21790 (b)(8)(A) through (F) require Preliminary Closure Plans to provide a preliminary description and schedule for the elements discussed in the following subsections. 2.5.1 Final Cover The County proposes placement of an evapotranspirative (ET) cover as an engineered alternative to the prescriptive 1-foot-thick low-permeability soil layer, as allowed under Section 21090(a). This proposal is based on: • The success of the ET cover at the Foothill Sanitary Landfill and other landfills • Suitability of soils at the NCRC&SL for an ET cover (sandy silts) • Recent determination by Regional Water Board staff that a barrier layer comprised of GCL requires seven feet of overburden soil to compress the GCL sufficiently to provide the equivalent of one foot of 10-6 cm/sec permeability. The County will obtain approval of the ET closure method prior to construction. 2.5.2 Final Grading and Drainage Plan The Final Grading and Drainage Plan incorporates the following constraints and objectives (Figure 3 and Drawing): 1. Maximum fill elevation to 320 feet msl. 2. The minimum 100-foot setback of waste from the west, south, and east property boundaries. The setback includes the perimeter soil berm and outboard drainage ditch (Drawing 2 and Drawing 3 - Detail 1).