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the RWQCB on June 2, 1997. The seven DE wells (DE-1 through DE-7) were subsequently renamed MW-36UA, MW-37UA, MW-38UA MW-39UA, MW-40UA, MW-41UA, and MW-42UA. • Between September 2001 and April 2002, a six-month ISO-GEN TM pilot test/feasibility study for groundwater treatment was conducted. The pilot test included the installation of six four-inch test wells (TW-1 through TW-6) and nine two-inch ISO-GEN TM monitoring wells (MW-24A through MW-32A). The groundwater monitoring wells and ISO-GENTM remediation wells have screen intervals of approximately 15 to 30 feet bgs and 5 to 30 feet bgs, respectively. The ISO-GENTM treatment system appeared to have limited impact on the increase of dissolved oxygen (DO) concentrations and the reduction of MtBE concentrations. However, the ISO-GENTM system did reduce TPHd concentrations in well MW-26A and MtBE concentrations in wells MW-28A and MW-32A (SECOR, 2003h). The results of the ISO-GENTM Pilot Study indicated the following biological activity is occurring at the Banta Fuel Terminal: 1. Nitrates (NOD and sulfate (SO4) are present throughout the site, with the exception of the area around MW-26A. Nitrate and sulfate depletion around MW-26A is believed to be due to natural biodegradation. 2. Surface water infiltration from the agricultural drainage trench is high in nitrates and sulfates. This situation creates a biodegradation-barrier to petroleum hydrocarbon. 3. The mass flux of TPHd and MtBE along the down-gradient margin of the Banta Fuel Terminal is three orders of magnitude lower than the concentrations of available electron acceptors. This indicates natural attenuation potential should be sufficient to remediate the downgradient margin of the plume. • Between October 29 and 31, 2003, 17 soil borings (TS-1 through TS-8, TS-10 through TS-17 and TS- 19) were advanced. Groundwater samples and selected soil samples were submitted for chemical analysis. Results of the 2003 site assessment indicates the presence of SPH in the area between AST #131 and AST #139. Based on the results cited in the Site Assessment Report and Interim Remediation Action Plan dated January 9, 2004, a Non-aqueous Extraction Technique (NETTM) system was selected as an interim remedial measure to remove the SPH and mitigate hydrocarbon mass from this source area. • Between December 1 and 18, 2003, 65 soil borings (OW-1 through OW-65) were advanced. Between February 10 and 17, 2004, oxygenation wells OW-1 through OW-65 were developed and purged. Approximately ten casing volumes of water was purged, and the field parameters including pH, conductivity, temperature, and turbidity were monitored and recorded during development. Twenty-one oxygenation points were monitored and sampled a minimum of 48 hours following development. Groundwater samples were submitted for chemical analysis. • Between March 1 and 25, 2004, the groundwater oxygenation points via above-and below-grade pipe to an onsite air compressor were connected with a series of in-line filters to remove particulates. Between March 26 and April 16, 2004, the system was tested to verify the correct operation of all process equipment and controls. During system testing, all onsite buildings and confined spaces were monitored daily for volatile organic compounds (VOCs) concentrations using a photo ionization detector (PID). On April 19, 2004, the system was configured to operate continuously. During the first week of • continuous system operation, onsite buildings, confined spaces, and monitoring wells within 50 feet of BLASLAND,BOUCK&LEE,INC. 3124106 — engineers,scientists,economists 3-5 J:\D0006\44634 00161022 Conceptual Site Model.doc