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• As far back as May 1983, Libbey Owens Ford (LOF) Glass stated that an area of the plant grounds was set aside for the purpose of waste disposal and consists of approximately 18 acres that was estimated to contain 10,000 to 20,000 tons of material at the time; the anticipated disposal volume being 5 to 20 tons/week in the future. This estimate was prior to closure of the WDS. This waste volume estimate is significantly higher than the estimated volume of wastes removed and should be taken into consideration when estimating the remaining volume of wastes at the site. Landfill Gas Investigation and Reporting • Based on available documents reviewed, one "soil vapor' well was proposed to be advanced using a 3-inch diameter auger with a "sampling point"to collect soil-vapor samples. The soil-vapor point was proposed to be advanced to depths of approximately 5 feet bgs or within the base of the waste. It is not clear why a depth of 5 feet was proposed. A schematic figure was provided showing two different boring diameters and information was missing from the figure. A soil vapor well point is not the same as a LFG well. LFG wells are typically constructed in larger diameter boreholes and should be designed so that the screened interval corresponds to the depths and thicknesses of the wastes and should take into consideration subsurface lithologies and topography of the WDS. • Based on available information, there did not appear to be an "as built' well design or a report indicating what was actually constructed at the site. It is not clear whether a LFG well was drilled and constructed or a soil vapor well was constructed. Typically after a LFG well is constructed at a WDS, it is field monitored for a period of one year and sampled quarterly also for one year, at which time, the data is summarized and a report is provided to the regulatory agencies summarizing results of both the field monitoring and quarterly analytical testing. Based on this, the necessity/requirements, if any,for additional LFG monitoring can be evaluated. Work Plans for Site Investigation and Remedial Action Plan for Waste Excavation at a Portion of the Waste Disposal Site • Available background information indicates that a work plan was not prepared and submitted for regulatory agency approval(s) prior to conducting the initial site investigations. The work plan typically includes: site identification and description; states the project objectives; descriptions of regional and/or site specific site geology and hydrogeology; a review and summary of background information; historical aerial photographs and summaries; information on regulatory requirements/notifications; references a site health and safety plan and as necessary, a community health and safety plan; describes in detail the planned scope of work (SOW) and methodologies and rationale for what is proposed; the analytical testing program and rationale; sample collection plan and methodologies; and reporting requirements. • Typically prior to waste excavation, a remedial action plan is prepared and submitted to the LEA and other regulatory agencies for their comments and approval(s). It appears that such a plan that includes an evaluation of remedial alternatives based on planned future site use was not prepared based on available documents provided for review. It is understood that there were time constraints. A brief "work plan" was submitted for planned waste excavation at a portion of the waste disposal site(please refer to the plan for specific comments included in Section 4.0). Ninyo&Moore 1 500 E.Louise Avenue,Lathrop,San Joaquin County,California 1 104690095 1 August 11,2017