SITE INFORMATION AND CORRESPONDENCE

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hn KLEINFELDER analyzed as a single sample for TPH-D by EPA Method 8015M/3550 and the composite did not contain TPH-D above the laboratory reporting limit. The sidewall samples were analyzed separately for diesel by the toxic characteristic leacheate procedure (TCLP). None of the sidewall samples had leachable concentrations above the laboratory reporting limit. The results of the soil sampling were reported in Kleinfelder's "Additional Diesel Excavation Sampling Results" letter report, dated May 18, 1992. Based on the results of the soil samples, the RWQCB approved closure of the excavation, and requested a workplan for the initial assessment of potentially impacted groundwater. In September 1992, Kleinfelder installed two wells near the containment area (EW-1 and MW-1). EW-1 was installed with a 4-inch casing for potential use as a groundwater extraction well. MW-1 was constructed using 2-inch casing. The results of the well installation and sampling were presented in Kleinfelder's "Initial Groundwater Assessment Report" dated October 20, 1993. The water sample from EW-1 contained 1500 ug/l TPH-D and the water sample from MW-I contained 240 ug/I TPH-D. During a May 27, 1993 site visit, Kleinfelder observed a product layer in both EW-1 and MW-1 of from 7-1/2 to 8 inches thick. The RWQCB requested a workplan for additional site assessment. Kleinfelder prepared a proposal for additional assessment dated September 10, 1993 for the following tasks: • Geoprobe groundwater assessment • Installation and sampling of three monitoring wells • Extraction well sampling for disposal characterization The workplan was approved by the RWQCB with comments on November 23, 1993. The Geoprobe investigation was performed on December 17, 1993. Results of the investigation were provided in a report entitled "Summary of Geoprobe Investigation" dated January 5, 1994. The Geoprobe investigation was performed to provide preliminary groundwater data to optimize the location of monitoring wells. Soil samples were also collected surrounding the former diesel fuel soil excavation to further assess soil conditions. i . 24-220176:FO1/CR43-8 (1994) Page 3 of 13 June 3, 1994 Copyright 1994 Kleinfelder, Inc.