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Ms. Diane Hinson Page 2 August 5, 1991 Proposed Scope of Work Based on past analytical data and groundwater flow direction, ERM-West recommends investigating the area south of the currently identified zone of diesel-affected soil and groundwater. We propose installing four soil borings south and southwest of this zone as shown in Figure A-3. These soil borings will be used to collect both soil samples and groundwater samples. The groundwater samples will be collected with the HydroPunch sampler following the same procedures used in the March 7, 1991 investigation. Soil and groundwater samples will be analyzed on site with a mobile laboratory. Two of the borings will be converted into 4-inch diameter monitoring wells. These two wells can be used in conjunction with existing monitoring well MW-4 to continue monitoring groundwater elevations and flow direction at the site. The exact well locations will be decided on site after reviewing the analytical data provided by the mobile laboratory. In addition, we propose that monitoring wells MW-1, MW-2, and MW-3 be abandoned, since groundwater levels are approaching the bottom of the well screens in these wells. All sampling, laboratory analyses, well construction and development, and borehole abandonment will be performed in accordance with the methodologies and protocols outlined in Section 2, and the health and safety procedures in Section 3 of the Workplan. On-site Biotreatment of Drill Cuttings We expect that we will generate approximately 2 to 3 cubic yards of drill cuttings at the site. We propose to biotreat these cuttings on site with a commercial product called X-19. The X-19 material is a commercially prepared mixture of organic matter, nutrients and micro-organisms designed to break down fuel hydrocarbons. The cuttings will be thoroughly mixed with the X-19 product in a ratio of 1 part X-19 to 3 parts of cuttings. During the mixing process, the moisture content of the mix will be adjusted to provide ample moisture for the biodegradation process while maintaining adequate aerobic conditions. The mixed material will then be placed on Visqueen in a pile no higher than 4 feet. The pile will be covered with Visqueen and left for approximately 90 to 100 days. Two samples will be taken from the pile at the end of the treatment period and analyzed for TPH by EPA Method 8015 (Modified). If TPH is detected above 1 mg/kg in the samples, then the mixture will be left another 30 days and resampled. We will consider the cuttings successfully remediated when TPH is no longer detectable above 1 mg/kg. The mixture can then be used by Safeway on site for landscaping purposes.