SITE INFORMATION AND CORRESPONDENCE

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Ms. Kathleen Minahan - 2 - * 14 June 2006 constituents of concern. However, the Workplan appears to base the assessment of groundwater gradient on a single sampling event. In this Workplan, Lesco does not propose any permanent monitoring wells, nor does it discuss any future monitoring wells. Monitoring wells provide repeatable sampling points that can detect changes in groundwater gradient, seasonal fluctuations in constituent concentrations, declining trends that may show remediation success, or increasing trends that may show an off-site source or ongoing on-site source. Since the site is adjacent to bulk petroleum facilities, and since petroleum in groundwater appears to facilitate degradation of nitrate in groundwater, Lesco should add analyses for total petroleum hydrocarbons by EPA method 8015 to all of its groundwater samples. In a 2 June 2006 telephone conversation, Regional Water Board staff discussed questions about the Workplan with Mr. Matt Scheeline of ERM. In this conversation and as documented in a 2 June 2006 email, we agreed on the following: • The soil sample interval is refined and discrete soil samples will be obtained at depths of 0.5 feet below ground surface (bgs),and just above the water table (estimated at about 4 feet bgs). • Soil and groundwater samples will be obtained in the locations indicated in the Workplan, and the information will be used to site permanent groundwater monitoring wells in the future. • An Investigation Summary Report will be provided summarizing the Workplan activities and results and will include tabulated historical data and a figure showing neighboring off-site properties, landmarks and monitoring wells. Regional Water Board staff conditionally concur with the Workplan provided Lesco adds the above changes as well as the following: • All groundwater samples should be analyzed for total petroleum hydrocarbons by EPA method 8015 in addition to the proposed analyses. In the Workplan, ERM identifies monitoring wells and/or piezometers in the vicinity of the Lesco facility that are associated with Riverside Cement Company, ST Services, Arco, and the Port of Stockton. The reports associated with these off-site monitoring wells and the associated investigations are available for public review at the Regional Water Board office at the letterhead address. If Lesco is interested in reviewing any of the records and reports produced on behalf of its neighbors in the Port of Stockton, Regional Water Board staff can assist in setting up an appointment for a file review. Lesco may proceed with the Workplan provided it incorporates the above listed changes. According to the timetable proposed in the Workplan, Lesco intends to conduct the site work within two months of the date of this letter, and provide an Investigation Summary Results Report about one month afterwards. This timetable