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Draft Supplemental Environmental Impact Report Page IV.G-11 Forward Inc. Landfill 2018 Expansion Project Groundwater Quality Groundwater quality has been impacted by Forward (including Austin)Landfills historical operations. The discussion of groundwater quality at the Forward Landfill is provided for background information regarding the overall site setting. Refuse accumulated at landfills can impact groundwater by leaching out chemicals over time. In the case of the unlined units at the Forward Landfill, the leachate generated had a direct path to the subsurface environment and groundwater. Landfill gas can also move VOCs form the vapor to dissolved groundwater phase. The lined portions of the Forward Landfill have not measurably impacted groundwater. The groundwater in the area between the Forward and Austin units (near the existing scale- house)shows the most impact from contaminants of concern. Since 2016,low level VOCs have been detected in point of compliance wells MW-13,MW-16, and MW-17. In addition, concentration limits (CLs)for several inorganic constituents have also been consistently exceeded in well MW-10,MW-18, and MW-19. The VOCs and inorganic CL exceedances are believed to be associated with landfill gas. GLA performed an investigation to assess the source and potential impacts of low-level VOCs in groundwater adjacent to the Forward Landfill (GLA 2017c,d). The investigation concluded that the low-level VOCs in groundwater (and lysimeter samples) at the original Forward Landfill are most likely due to landfill gas from unlined unit WMU B. This is based on the fact that WMU B is the only unlined landfill cell and VOCs have typically been concentrated near it;the VOCs measured are typically erratic, low concentrations, characteristic of fluctuating landfill gas conditions; the detected VOCs are typical of landfill gas constituents,VOCs have been detected in upgradient and downgradient wells; and there is generally an absence of notable inorganic constituents that would be associated with a liquid release. The most prevalent chemicals of concern that affect groundwater quality at typical landfill sites are chlorinated solvents (referred to as VOCs), common to hundreds of consumer products. The origin of the VOCs in landfills is likely the result of a long process of degradation of household waste, containing common solvents such as tetrachloroethene (PCE), and trichloroethene (TCE). The VOCs can be retained in solid state media (by adhering to clay particles as they move down in the unsaturated zone), in soluble form(as a dissolved fraction in surface water or groundwater), or in the form of a gas (circulating in the flux of the other common landfill gases, methane and carbon dioxide). The VOCs can transform easily from the solid, soluble, or gas form depending on the circumstances. The next cell planned for construction at the landfill is WMU FU-19, which is located between the Forward and Austin units in the area of the current scale-house. This cell is within the permitted footprint of the existing permitted landfill and not part of the expansion areas. Forward Landfill has requested the closure of wells that would be impacted by the construction of WMU FU-19 (Lewis Engineering 2017). RWQCB staff reviewed the January 23, 2018 Request for Relocation and Abandonment of MW-17,MW-18, MW-19 (Republic Services 2017). The request included a groundwater monitoring well installation workplan that proposed to install and monitor replacement groundwater monitoring wells MW-17R and MW-19R prior to properly destroying groundwater monitoring wells MW-17, MW-18, and MW-19.