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The draft Phase III Technical Memorandum was submitted to DTSC in January 1995 (CH2M HILL, January 31, 1995). DTSC provided comments on the draft report in a meeting on February 28, 1995 and indicated the need for further groundwater investigation at the site. DTSC confirmed their comments to the draft Technical Memorandum in a letter dated March 8, 1995, stating that further groundwater investigation is required and requesting a work plan describing the additional work (Phase IV). The final Phase III Technical Memorandum was submitted to DTSC on March 14, 1995. As discussed in Section 1.1, a work plan for the Phase IV groundwater investigation will be submitted after 6 months of evaluation of the groundwater gradient. ® 1.4 Proposed Supplemental Soil Investigation The primary chemicals of potential concern found in soil in Area I are PNAs and petroleum ' hydrocarbons. The greatest concentrations of PNAs in soil are generally associated with the fill underlying the site. The fill is primarily located where former MGP facilities existed, such as beneath the foundations of buildings, tar sumps and pits, gas holders, and lampblack separators and bins. These facilities were used to store and process the raw feed materials and residues from the MGP process, which may have contained PNAs. PNAs are present beneath the fill in native soil near the location of former underground and in- ground fuel tanks such as occur near wells MW-9 and MW-10, or with other specific features where petroleum hydrocarbons may have been used at the former MGP, such as the lampblack pit (boring B-17) and the tar pit (boring B-15). See Figures 1-2 and 1-3. Several PNAs including acenaphthene, acenaphthylene, anthracene, fluoranthene, naphthalene, phenanthrene, and pyrene can be present in petroleum-derived fuels such as diesel. It is believed that residuals from several of the above mentioned former MGP facilities and former underground storage tanks could be potential sources of PNAs and petroleum ' hydrocarbons to groundwater. The extent of these potential source areas will be further defined during this investigation. Figure 1-3 presents the locations of suspected source areas. The following is a description of four suspected source areas: • Source area #1. This is the location of former underground fuel tanks. Soil at ' 24 feet bgs contains PNAs, TPH-diesel, and cyanide. Groundwater in the vicinity contains TPH-diesel and gasoline,benzene, and PNAs. • Source area#2. This is the location of the former lampblack pit and gas holder. Soil is saturated with oil and water at depths of 5 to 25 feet bgs. The soil adjacent to the former lampblack pit contained PNAs, TPH-diesel, and TPH- ' gasoline. 1 ' SF010030B7E.DOC 1-6