SITE INFORMATION AND CORRESPONDENCE

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Mr. Mike Pitta - 2 - 19 December 2006 Hydrocarbons (TPH) as gasoline was reported at a maximum concentration of 130 milligrams per liter (mg/L), TPH diesel at 5.4 mg/L, benzene at 9,900 micrograms per liter (ug/L), and methyl tertiary butyl ether (MTBE) at 200,000 ug/L. Groundwater samples were collected for natural attenuation parameters in the fourth quarter 2005. Sulfate, ferrous iron, and methane were detected in source area wells at higher concentrations than the plume perimeter wells suggesting that anaerobic biodegradation of the petroleum hydrocarbons is occurring. The Soil Remediation Report describes the discharge of transmix fuel (gasoline and diesel mixture) on 24 July 2006 and associated remedial response activities. The release occurred from a pump back-pressure valve in the manifold area of the site. The volume discharged is unknown; however, approximately 160 gallons of SPH were recovered from the containment pad, surface water catch basin, and hand-excavated trenches and sumps. Approximately 450 gallons of petroleum-impacted groundwater were recovered from the remedial excavation area. Visibly stained soils were removed by hand-excavation down to the groundwater table about 3 feet deep across an area measuring 23 feet wide by 70 feet long. Approximately 189 tons of soil and surface gravel were excavated and placed in covered roll-off bins. The lateral extent of excavation was limited by existing infrastructure though stained soils related to the transmix discharge were reportedly completely removed from the vadose zone. Seventeen sidewall soil confirmation samples and two groundwater characterization samples were collected from the remedial excavation area. The samples were analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX compounds), and five fuel oxygenates of MTBE, ethyl tertiary butyl ether (ETBE), diisopropyl ether (DIPE), tertiary amyl methyl ether (TAME), and tertiary butyl alcohol (TBA) using EPA Method 8260B, and TPH gasoline, TPH jet fuel, and TPH diesel using EPA Method 8015M. Maximum soil sample chemical concentrations were 29,000 milligrams per kilogram (mg/kg) TPH diesel; 9,600 mg/kg TPH gasoline; 4,000 mg/kg benzene; and 9,000 micrograms per kilogram (ug/kg) MTBE. Maximum groundwater sample chemical concentrations were 31 mg/L TPH diesel; 39 mg/L TPH gasoline; 4,800 ug/L benzene; 850 ug/L MTBE. Groundwater sample chemical concentrations were within the range of historical data from nearby monitoring well SP/M-9. Regional Water Board staff in a teleconference on 12 October 2006 concurred with KMEP's request to backfill the excavation based on complete removal of soils containing SPH. The Feasibility Study (FS) was proposed in the Soil Remediation Report to re-evaluate monitored natural attenuation (MNA) as the preferred remedial alternative to address groundwater pollution at the site. Based on the range of current manifold area soil and groundwater petroleum hydrocarbon concentrations compared with historical site data, KMEP recommended that MNA should remain as the selected remedial alternative with contingencies for SPH removal if present in the future. REGIONAL WATER BOARD REVIEW COMMENTS Figures were provided in the Annual Report tabulating groundwater chemical data for the two semiannual sampling events. Although a similar depiction was referenced in the First Semiannual Report as Figure 4, the version of Figure 4 provided in the document showed shallow groundwater elevation data for May 2005. Note that in accordance with Monitoring and Reporting Program (MRP) No. R5-2005-0815, groundwater monitoring reports should include isoconcentration contour maps for chemical constituents. These maps should be