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Mr. Steven Osborn 2 • 14 November 2007 KMEP Holt Release Site, Holt about 10 feet away from N-17. An increasing benzene trend is observed in both of these wells. KMEP believes the increase in concentrations is because N-17 is no longer pumping and pulling in clean water from offsite, which was diluting the benzene concentrations. KMEP believes that the benzene concentrations will come to equilibrium and start to decline soon. Overall, KMEP believes that monitored natural attenuation (MNA) is effective at the Site. The Pilot Study Report concluded that MNA is occurring and that phytoremediation will enhance the reduction of hydrocarbons in the subsurface. The Pilot Study Report recommends the following changes to the Monitoring and Reporting Program (MRP): • Reduce sampling frequency to semi-annual; • Remove select upgradient wells (M-1, M-2, and M-3) and deep wells (N-21 , N-22, N-23, and N-24) from the MRP; • Eliminate current annual monitoring program for methyl tertiary butyl ether (MTBE) and tert butyl alcohol (TBA) because these compounds are related to background concentrations in Trapper Slough; • Eliminate the MNA general chemistry analyses that were added to the MRP for the bioremediation pilot study; and • Adjust the current semi-annual reporting periods from fourth/first quarter and second/third quarter to first/second quarter and third/fourth quarter. KMEP submitted the Work Plan to describe the methods to be used to destroy 10 SVE wells (SVE-1 through SVE-10) and four deep groundwater monitoring wells (N-21 through N-24). KMEP discontinued operation of the SVE wells in 2004 and removed the aboveground portions of the SVETS system in 2005. The SVE wells are no longer necessary because future remediation will be via MNA. KMEP believes the deep groundwater monitoring wells are no longer necessary because they have been consistently below detection limits. The Annual Report summarizes the groundwater data collected in 2007. Groundwater elevations declined in 2007 because of the abnormally low precipitation, but groundwater flow patterns were to the southeast, which is consistent with historic monitoring data. TPH as gasoline (TPHg) and benzene were not detected in upgradient wells or shallow downgradient wells. Deep wells were also below detection limits, with the exception of N-24. N-24 contained benzene and TPHg at 47 micrograms per liter (pg/L) and 110 pg/L, respectively. These are the highest concentrations in this well since 2005. Our comments are presented below: 1 . Regional Water Board staff concur with the conclusion in the Pilot Study Report that MNA is occurring. 2. Regional Water Board staff reviewed the recommended MRP revisions and prepared a draft MRP for your review and comment. By 26 November 2007, please review the attached draft MRP and provide any comments. Changes to the existing MRP include the following: • The sampling and reporting frequency is reduced to semi-annual and the reporting periods changed to first/second quarters and third/fourth quarters.