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1.0 INTRODUCTION This document is submitted in compliance with Item 1 on Page 4 of the Water Code Section 13267 Order issued by the RWQCB to the County on July 7, 2011, which requires an Evaluation Monitoring Program (EMP) investigation at the Corral Hollow Sanitary Landfill (CHSL) in San Joaquin County, California, and with Article 1, Subchapter 3, Title 27 of the California Code of Regulations (27 CCR). This document identifies work to be conducted for the EMP investigation at the CHSL in San Joaquin County, California. The work approach incorporates the discussion at a meeting between the County, RWQCB, Ausenco Vector, and GLA held on July 26, 2011. The ultimate goal of this EMP is to define and characterize the nature and extent of shallow groundwater impact to provide a database to support an Engineering Feasibility Study (EFS) and identify the County's corrective action options. As detailed herein, project work will involve advancement of offsite groundwater monitoring wells, groundwater sampling and analyses, and an evaluation of groundwater flow, impacts, and impact sources. 2.0 BACKGROUND The CHSL is a closed Class III municipal solid waste disposal site. Operations at the site began in the 1950's. The County began operating the landfill in 1991. Waste acceptance ceased in 1995, and formal closure was completed in 1996. The final cover system includes a two- to six-foot thick foundation layer that is overlain by a one -foot thick low -permeability soil layer and a one -foot thick vegetative soil layer. A landfill gas collection and destruction system was constructed at the site in 2001. The County maintains operational responsibility through the post -closure maintenance period. Groundwater monitoring has been conducted at the site since 1988. The results of past routine groundwater monitoring conducted by the County identified impacts from volatile organic compounds (VOCs) in the shallow groundwater zone near the northern edge of the landfill at two wells (MW -5, MW -8). These impacts are believed to be related primarily to landfill -gas sources. Two other shallow wells remain without impact, as do the two deep - aquifer wells. Historical groundwater elevation data suggest that groundwater in the shallow, perched zone flows to the southeast beneath the landfill. However, as a result of the somewhat linear arrangement of wells that monitor this perched aquifer and the fact that historical geological investigations indicate that the perched aquifer is limited in area to the northwestern corner of the site, the fate and extent of the perched aquifer groundwater is not well defined. 2011-0115 CHSL EMP Workplan y Geo -Logic Associates Revision 2 — January 11, 2012