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• • Draft Supplemental Environmental Impact Report Page IV.G-15 • Forward Inc. Landfill 2018 Expansion Project • Current Groundwater Quality To date evaluation monitoring indicates that chlorinated hydrocarbon impacts extend as much • as 7,700 feet downgradient of the Austin Road Unit. The zone of groundwater affected by VOCs • is shown in Figure IV.G-2 (the principal VOCs of concern include PCE and TCE). As shown in this figure, the limits of affected groundwater appear to be well-constrained both laterally and • vertically on the east by wells AMW-5R, AMW-30S and AMW-30 and partially to the west by • wells AMW-28, AMW-325, AMW-32, and AMW-2. The zero line for the vertical and lateral • extent of the plume has not been fully established to the northwest,north, and north-northeast. • The overall shape of the VOC-affected plume with respect to groundwater contours and the distribution of VOCs between the shallow and deeper zones indicate the lateral and vertical • limits of the VOC affected groundwater have likely been affected by regional flow conditions . (agricultural/industrial pumping, recharge rates, etc.). • In addition to the sampling at the NCYC, groundwater samples were collected from 56 • residences between June 19 and July 6,2017. Six of the 56 residential wells showed detected • VOCs in the wells as reported by GLA (2017). • These monitoring well results support two conclusions: (1) that Forward's corrective actions at • and around the unlined Austin Road Unit are improving groundwater quality in the area, and • (2)the offsite groundwater contamination represent historical releases from the Austin Road • landfill that are slowly spreading but becoming less concentrated over time. • Forward is continuing to assess landfill gas and groundwater issues at the Austin Road Unit • and complying with RWQCB requirements for the CAP. The April 2009 installation of two new • groundwater extraction wells at Forward increases the volume of groundwater being extracted • and treated "at the source" and to an extent draws back the groundwater plume migrating offsite. Leachate Generation, Treatment, and Monitoring ; The two new WMU expansions proposed would have current required Class II lining and leachate collection designs. The Forward Class II Surface Impoundments would be lined with • high density polyethylene (HDPE) geomembrane.Both new areas would have the leachate • collection and monitoring required (by the RWQCB) of the landfill operations, as described the updated O&M manual and in the project description of the expansion. The new units would have blanket LCRS. The components of the LCRSs are summarized in the Project Description. • The blanket LCRS described would be placed on both the base and slopes of the landfill • expansion modules. The LCRS is the first line of defense for the protection of groundwater from any leachate generated from the landfill. • • • • •