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h" KLEINFELDER August through November 1998. Quarterly groundwater sampling has continued since that time. In March 2000, the PHS/EHD approved a request by Wilbur-Ellis to reduce the groundwater sampling frequency to semi-annual, and to discontinue sampling for fuel oxygenates and alcohols. However, said testing must resume prior to closure application. Groundwater contamination at the site has been evaluated to the south, east and west of the former underground storage tank location. Additional evaluation of the plume to the north and northwest has been requested by PHS/EHD. -- Krazan & Associates has described the ratio of benzene to gasoline in water samples from MW-1 as elevated. Both the PHS/EHD and Krazan have suggested that the areal distribution of benzene in groundwater grab samples and monitoring well samples is unusual. Possible explanations suggested by Krazan for the "elevated" benzene concentrations include a source of non-gasoline-derived benzene from on-site spills or an off-site location. According to Krazan's reports, the areal distribution of the groundwater contamination trends northwest/southeast across the site. This observation agrees with field data presented by Krazan indicating more permeable soils and sand lenses are present to the north-northwest (B-2) and south-southeast (B-3) of the former underground tank location. PROPOSED SERVICES Task E01 —Additional Report Review Kleinfelder will review previous soil and groundwater reports completed by Krazan and others for the subject site. The information will be supplied by Wilbur-Ellis Company. The review will include the Phase I Preliminary Hazardous Materials Site Assessment by Telic Engineering Corporation and subsequent Phase II work for the site by Krazan and Associates. The Phase II work should include previous field data, boring logs, purge logs, surveys, etc. This information will be used to modify the draft workplan as appropriate. Task E02—Sensitive Receptor Survey A sensitive receptor survey will be conducted to identify wells, surface water and other potential receptors within 2,000 feet of the site boundaries. The survey will include a Department of Water Resources (DWR) survey (conducted in October, 1998) within 2,000-foot radius, and a visual survey for wells, surface water bodies, etc. within a 500-foot radius of the site boundaries. In addition to the DWR survey, local permitting agencies and local water purveyors will be contacted to assess potential receptors within a 2,000-foot radius of the site boundaries. The receptors will be illustrated on a site map. A short letter-style report detailing the data obtained relevant to each receptor will be included including construction details, copies of well logs, (as available), etc. 20-4439-0I.E01/20008311 Page 2 of 6 Copyright 2000 IUeinfelder,Inc. April 25,2000