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' Work Plan-Pilot Testing Page 2 Cutter Lumber Site Project No. 102.3 October 30,2001 1.1 Site History The site of the subject gasoline release was discovered as a result of a groundwater ' monitoring event at the Western Lift Site in the southerly part of the subject Property (as shown in Figures 1, 2) during which a sample was collected from an on-site domestic ' well. After a review of historic records, a former 1,000-gallon underground gasoline tank and an above ground diesel tank were identified along the western Property margin in the north central portion of the site. Subsequent soil borings confirmed that the release had 1 impacted the vadose zone soil and the groundwater. In March of 1998, seven groundwater monitoring wells were installed to monitor the groundwater plume. Two earlier wells, MW-1 and MW-4 still remain from the initial Western Lift investigation ' near the south end of the Property. i 1.2 Current Site Status Based on available groundwater monitoring data, the gasoline contaminant plume is stable or decreasing. The core of the contaminant mass is, however, not degrading at a rate that will result in a site closure in the foreseeable future. The groundwater in the ' immediate area of the release is oxygen deficient and does not allow for appreciable growth of aerobic bacteria that could metabolize the adsorbed petroleum hydrocarbons. 1.3 Proposed Scope of Work The goal of the work described herein is to develop new engineering data, which will be used in conjunction with existing data, as the basis of a Feasibility Study to identify the most feasible and cost effective method to adequately mitigate the residual soil and ' groundwater contamination at the Cutter Lumber Site. This will be augmented by information from the remedial investigation at the adjacent property, the Former Manna Pro Property - 4004 S. El Dorado Street. The Feasibility Study will compare several alternatives for remedial action and determine which methods should be used to generate ' the final Remedial Action Plan (RAP). This work, described in the following sections is proposed pursuant to a directive of the San Joaquin County PHS/EHD dated September 7, 2001. The following two sub-sections discuss the guiding concepts of the tasks being proposed by this Work Plan, and introduce the major elements of the work that will be needed to accomplish the stated goals. 1.3.1 Conceptual Basis ' Past work performed at the former Manna Pro Property documented pilot-level held testing and a Feasibility Study of a remedial concept involving simultaneous vapor extraction and groundwater pumping. This work provides much of the basis for possible future corrective action at the Cutter Lumber site. Both of these sites bear many ' 2937 Venernan Ave.,#B240 Geo-Phase Environmental Inc. Phone(209)569-0293 Modesto,CA 95356 Fax(209)569-0295 1 I