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All VOCs detected in this well are among the VOCs found in MW-5 and MW-8, generally at lower concentrations. These data support the conclusion that MW-5 is closer to the source of the VOCs. There are no significant trends reported for VOCs by the Sanitas program. Extent of Groundwater Impact Delineated The area of groundwater impact had apparently extended to the northeast to a maximum distance of approximately 900 feet from the landfill property (Figure 5). The extent of groundwater impact is conservatively delineated based on the following evaluation of PCE concentration, as follows: • Since PCE was not detected at MW-9A and MW-10A, a 0.0 ug/L concentration is assigned to these wells. • The PCE concentration detected at MW-11 A(0.19 ug/L) is slightly above the laboratory method detection limit of 0.13 ug/L • A linear extrapolation of the 1 ug/L contour interval lines between a PCE concentration of 5.1 ug/L at MW-5 and a PCE concentration of 0.19 ug/L at MW-11 A The overall shape of the PCE plume is assumed to be relatively symmetrical from an apparent source located near the northern boundary of the landfill, an area that includes both County and Caltrans refuse. The source location appears to be centered between well MW-5,perimeter LFG well GW-1, and well MW-8. The apparent western edge of VOC impacted groundwater adjacent to the landfill is the western edge of the Corcoran Clay Formation, (Figures 2 and 5). The apparent eastern edge of VOC impacted groundwater adjacent to the landfill is well S13-1,which is an apparent groundwater high elevation point in the shallow aquifer(Figure 2). The plume of impacted groundwater is elongated in the direction of groundwater flow, which is generally to the north-northeast from the landfill. After the first nine monitoring events and two climatic cycles, the data seems to indicate a decreasing plume beyond the landfill property. The concentration of VOCs at wells MW-5 and W-8 have been relatively stable since the installation of the LFG collection system in 2001, allowing the presumption that the on-site source of the plume has remained relatively constant. However,the data from the off-site wells (MW- 9A, MW-l0A and MW-11A) indicate that the extent of the off-site plume is decreasing,probably due to the effect of the LFG collection system. ® Deep Aquifer ■ MW-6(Down gradient): Concentrations of all the parameters analyzed were within established concentration limits this quarter(Table 2). Corral Hollow Sanitary Landfill 16 Department of Public Works/Solid Waste 2nd Quarter 2014 Groundwater Monitoring County of San Joaquin—July 15,2014