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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2010-0016 -2-SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS NORTH COUNTY LANDFILL SAN JOAQUIN COUNTY Groundwater The average depth to groundwater at the site is about 154 feet bgs (-36.5 feet MSL) with about six (+/-3) feet of seasonal variation. The gradient is typically about 0.004 ft/ft toward the southwest. The upper water-bearing zone occurs in the alluvial deposits of the Turlock Lake and Laguna formations. There are currently six groundwater monitoring wells at the site including one upgradient (G-1), one side gradient (G-2), and four down gradient (Gs-3D, 4, 5 and 6). Monitoring of well G-2 was discontinued in 1997. In 2002, a VOC release to groundwater consisting primarily of low to trace concentrations of BTEX constituents was confirmed. Subsequent monitoring showed attenuation of the VOCs, however; no VOCs have been detected in groundwater since startup of a LFG extraction system installed as a corrective action measure in 2006. Historical monitoring data for the landfill shows good upper zone groundwater quality, with no indication of impacts from leachate constituents. In the First Half 2008, for example, the maximum concentration of TDS and chloride detected down gradient of the landfill were 160 mg/L and 7 mg/L, respectively. Revised WDRs These revised WDRs prescribe updated requirements for landfill construction, operations and monitoring. Construction The WDRs (Construction Specifications 1 and 2) require that future landfill modules be constructed in accordance with Subtitle D; the approved EAD for Module 4; or as separately proposed and approved by the Regional Water Board. Discharge Specification B.1 limits vertical expansion to the maximum proposed elevations for each module under the Discharger’s Vertical Expansion Plan, as supported by geotechnical analysis and approved by the Local Enforcement Agency. Facilities and Operations Provision G.8 requires that the Discharger investigate the condition of certain landfill facilities, including manually operated LCRS sumps, lysimeters that have been historically dry, and inactive monitoring well G-2. A report as to the status of these facilities, including work plans and schedules for necessary/required repairs and improvements, must be submitted by 31 March 2010. (Facility Specification C.4 requires that manually sumps must be upgraded with automatic controls within two years of adoptions of this Order.) Discharge Prohibition A.3 and Discharge Specification B.4 allow the Discharger to continue returning landfill leachate and LFG condensate to Subtitle D-lined modules consistent with liquids restrictions in Title 27 and Subtitle D. The WDRs also prescribe requirements for the handling and disposal of hazardous treated wood waste (TWW) under the California Health and Safety Code (division 20, chapter 6.5, article 5, section 25150.7); and CCR, title 22 (chapter 34, section 67386.2). The WDRs allow the landfill to accept TWW, provided that the discharge is limited to Subtitle D-lined modules and that it is handled in accordance with specified alternative management standards under Title 22. A copy of Title 22, Chapter 34