ARCHIVED REPORTS_2003 FEASABILITY STUDY REPORT AND SITE ASSESSMENT WORK PLAN

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S E C O R 2003 Feasibility Study Report and Site Assessment Work Plan July 18, 2003 Page 7 electron acceptors. This situation indicates natural attenuation should be sufficient to remediate the downgradient margin of the plume. ■ In July of 2001, SECOR submitted an assessment report and workplan for additional assessment as part of the ongoing investigation of hydrocarbon-impacted groundwater and soil at the site (SECOR, 2001). Data collected in April of 2001 and May of 2001 indicated the extent of the MtBE within shallow groundwater (northeast of the site and on private property) was not defined. Off-site groundwater analysis results in May of 2001 reported MtBE concentrations ranging from 6.1 Ng/L to 95 ,ug/I. Microbiological analysis of soil and groundwater samples collected on April 12, 2001 suggested a healthy population of hydrocarbon degraders exists with good natural attenuation potential at the offsite sample locations. ■ On December 28, 2001, a flange on a piping manifold near MW-15A failed and released less than 10 gallons of red dye diesel at the site. On January 9, 2002, 15 soil samples were collected in and around the spill area. Borings were advanced to approximately 0.5 to 1.5 feet bgs (SECOR, 2002a). ■ In November of 2002, SECOR submitted an assessment report and work plan for additional site assessment, which summarized the results of the installation of five offsite monitoring • wells (MW-54A through MW-59A) (SECOR, 2002b). The objective of the off-site assessment activities was to delineate the lateral extent of petroleum hydrocarbons (including MtBE) in offsite groundwater. MtBE concentrations were detected in five of the five borings, ranging from 0.6 µg/I (MW-55, MW-57 and MW-59) to 1.0 Ag/I (MW-54). TPHd concentrations were detected in three of the five samples at concentrations ranging from 84 lag/I (MW-55) to 160µg/I (MW-57). ■ In August of 2002, SECOR submitted a construction support activities report (SECOR, 2002e). This report documented the following activities: 1. Pre- and post-removal soil characterization within the footprint of the ethanol transfer facility excavation. 2. The destruction & proper abandonment of MW-14A and TW-3 by Watermark Drilling of Woodland, California. 3. The collection of post-remedial soil data in the former DE area and post-demolition soil data in the card-lock area. 4. The segregation, profiling, transportation and disposal of effected soil within the transfer facility excavation. A total of 397 tons of soil was removed from the excavated area and transported by Integrated Wastestream Management Inc. (IWM) to Forward Landfill located in Manteca, California. • On January 21 through 29, 2003, Cascade Drilling Incorporated (Cascade) completed site assessment activities performed to delineate the vertical and lateral extent of pollutants at the site. The site assessment included 15 soil borings (NSB-0 through NSB-4, NSB-6 through NSB-15) and 5 monitoring wells (MW-61 UA, MW-62UA, MW-63A, MW-64B, and MW-65A) (SECOR, 2003b). I:\Chevron\1001621\REPORTS\2003\2003FS\FS 2003 revD.doc