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1.0 INTRODUCTION This Well Completion Report has been prepared for the County of San Joaquin, Public Works Department, Solid Waste Division (County) by Geo -Logic Associates (GLA) to fulfill a reporting requirement contained in Item 2, Page 4 of the Section 13267 Order for Technical Reports issued by the California Regional Water Quality Control Board — Central Valley Region (RWQCB) on July 7, 2011. Work described herein has been conducted as part of an ongoing Evaluation Monitoring Program (EMP) at the Corral Hollow Sanitary Landfill (CHSL). Work conducted to date has been in accordance with the EMP workplan that was approved by the RWQCB on August 25, 2011. 2.0 BACKGROUND The CHSL is a closed, Class III municipal solid waste disposal facility located southeast of the intersection of Corral Hollow Road and State Route 580 at 31130 South Corral Hollow Road in San Joaquin County, California. The site ceased operations in 1991, and was formally closed in 1995 with construction of a prescriptive final cover system in accordance with Title 27, Section 21090 of the California Code of Regulations. Groundwater monitoring at the CHSL began in 1987 with the installation of wells MW-1 through MW-5 as part of the Solid Waste Assessment Test (SWAT) program. Through construction of these wells, two water-bearing zones were identified: a shallow zone and a deeper zone. The shallow zone is limited to the north-eastern third of the site at approximately 230 feet above mean sea level. This zone is apparently created by water perched on the Corcoran Clay member of the Tulare Formation, which is intermittent in this area. The deeper water bearing zone underlies the entire site at approximately 50 feet below mean sea level. In 1991, volatile organic compounds (VOCs), including trichlorofluoromethane and tetrachloroethene, were detected in samples from shallow groundwater monitoring well MW-5. The detections were verified during subsequent monitoring events, and the presence of VOCs has historically been attributed to minor landfill gas migration. In response to these detections, the County installed a landfill gas collection and destruction system at the site in 2001. The deep aquifer remains unimpacted by landfill gas. Groundwater levels in the deeper zone decreased until wells MW-1, MW-2, and MW-3 went dry. In 2003, wells MW-6 and MW-7 were drilled to replace the deeper zone monitoring wells that had gone dry, and well SB-1 was drilled to provide additional information regarding the shallow zone groundwater conditions. In 2007, well MW-8 was constructed to better assess the distribution of VOCs in the shallow zone. Well Completion Reporte-IC Page ■ 1 Corral Hollow Sanitary Landfill Ass ® c ! A r 8 $T— December December 15, 2011