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M Pilkington North America, Inc. - 2 - 16 March 2015 (approximately 10-15 feet below ground surface (ft bgs)). The sampling locations were selected both within and outside the known estimated dissolved plume area to determine extent of contamination and migration. Groundwater samples will be analyzed for TPH as diesel, TPH as motor oil, kerosene, naphthalene, and BTEX. Soil Investigation Following first groundwater sampling, drilling will continue for an additional 20 to 40 ft depth below the shallow zone to collect two continuous soil cores from this deeper zone. One soil core will be selected from an up-gradient location and the other from a cross- gradient locations to study the subsurface stratigraphy and identify target zones for future deep zone sampling at all locations to define the vertical extent of dissolved plume and contribute to the best design of future additional recovery wells. Selected soil samples will be analyzed for TPH as diesel, TPH as motor oil, kerosene, BTEX, and naphthalene. LNAPL Recovery Well Installations The Work Plan proposes to overdrill wells RW-1 through RW-4 and reconstruct them with larger diameter, 6 inch casing with 0.06 screen slots, and appropriate filter pack. The Work Plan also proposed to install two additional recovery wells, RW-7 and RW-8, in the central portion of the LNAPL plume near the utility corridors to a total depth of 18 ft bgs. The recovery wells will be surveyed and the data uploaded to the Geotracker database. Skimmers are planned for all recovery wells. Based on the planned weekly skimming and bailing product recovery, PNA will provide recommendations for enhanced LNAPL recovery in the subsequent semi-annual groundwater monitoring report. Sump Evaluation The site Furnace Building contains four dewatering sumps in the basement to prevent the glass furnace from becoming submerged during periods of high groundwater. PNA will provide the Regional Water Board with sump construction details and future operation. Regional Water Board Work Plan Comments: 1. The discussion of the fourteen boring locations on page 3 of the Work Plan includes a statement that the deeper target zone encountered in these borings (20-60 ft bgs) will be identified for sampling at all locations to determine the vertical extent of the dissolved plume. However, the Work Plan needs to specify when this sampling to determine the vertical extent will occur. 2. The Work Plan proposes to obtain the deep soil core from a cross-gradient location and one deep soil core from an up-gradient location to provide data on subsurface stratigraphy and target zones for future deep zone sampling. However, these borings may not provide information on down-gradient stratigraphy, which is crucial to develop target sample locations and design effective additional recovery wells. Borings need to be selected to define stratigraphy for the conceptual site model, and in particular, to define the down- gradient and vertical extents of the plume.