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WASTE DISCHARGE REQUIREMENTSORDER NO. R5-2003-0020 -4- FOR COUNTY OF SAN JOAQUIN FOR CONSTRUCTION, OPERATION, CLOSURE AND EVALUATION MONITORING FOOTHILL SANITARY LANDFILL, MUNICIPAL SANITARY LANDFILL SAN JOAQUIN COUNTY l_ Additional groundwater monitoring points proposed for Module 1 include MW -2R near the southwest comer of the module as shown on Attachment B. This downgradient location was selected because the groundwater flow direction beneath the site has historically been toward the southwest. The Discharger shall include the one other well on the property (domestic /supply) as part of the monitoring and reporting program. 24. The current Module "I" does not include unsaturated zone monitoring. Unsaturated zone lysimeter LZ -1 is proposed to be installed near MW -1 for background monitoring data. Unsaturated zone lysimeters LZ -2 through LZ -4 are proposed to be installed beneath Module 1, under the leachate sump (LZ -2), under one LCRS trench (LZ -3), and under the southwest area of the base liner system (LZ -4). The secondary containment system beneath the leachate sump for Module 1 is identified as L-1. The lysimeters have access ports available at the surface for sampling of soil -pore liquids. 25. Surface water flow enters the Foothill Landfill property boundary as an intermittent water way and then flows offsite to a pond. Surface water sampling location S-1 (upstream) is located where the water way enters the property. The downstream sampling location S-2 captures water quality that runs off the facility prior to the stockpond. Cattle graze on the property along the water way and the stockpond. 26. The drainage management system is a complex system. The site development plans utilize 12 -foot -wide drainage channels along the landfill perimeter to handle storm water runoff from the Module "I" landfill. The channels will discharge to sedimentation/detention basin(s) for sediment control, and to minimize stormwater flows off site. Initial construction of Module 1 will include a 20 -foot -wide drainage bench constructed along the common edge of the existing landfill to divert drainage, and 50 -foot wide perimeter berms will be constructed along the other three sides of the module for access and drainage. Initial excavations of Module 1 will create a temporary sedimentation/detention basin for the evaporation, and if needed, pumped discharger to the natural downgradient drainage swale. Stormwater from onsite soil Stockpile 1 west and southwest of Module 1 will be retained in a temporary southeast basin. Stockpile 2 is near the south site boundary where a sedimentation/detention basin will be constructed within the 200 -foot setback area of the landfill site to control sediment, before stormwater release back to a natural swale. 27. The Discharger's proposed detection monitoring program for groundwater and soil -pore liquids in the unsaturated zone at this Unit satisfies the requirements of Title 27. 28. The Discharger proposes to install a landfill gas monitoring system that also functions as a soil gas extraction trench beneath the single -composite liner as horizontal soil gas piping around the base of the perimeter and below the center of Module 1 to monitor the unsaturated zone for the presence of VOCs. Horizontal LFG collectors will also be installed in the first refuse lift, a minimum 15 feet above the liner. These two systems will have riser pipes to the surface for sampling and/or future collection of LFG, as applicable. The horizontal LFG collector pipes will be surveyed to allow for future connection by drilling.