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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 I 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 an 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 I 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 i 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. '