SITE INFORMATION AND CORRESPONDENCE

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Mr. Steve Osborne -2 - 22 February 2011 KMEP Stockton Terminal Appendix D contains a Mann-Kendall statistical analysis (Mann-Kendall) for MTBE that supplements a monitored natural attenuation (MNA) analysis initially provided in the 28 March 2008 Estimated Times For Petroleum Hydrocarbons and Fuel Oxygenates to Achieve Water Quality Objectives at the SFPP, L.P Stockton Terminal, Stockton, California (MNA Estimate). The analysis shows that there are decreasing MTBE concentration trends in four of the nine wells including SP/M-9. KMEP concluded that the other wells, including SP/M-10, displayed no trend. Section 6.3 of the Annual Report presents an attenuation rate evaluation that updates the March 2008 evaluation. As requested by Central Valley Water Board staff in a 12 May 2009 letter, attenuation rates were calculated in accordance with the USEPA's guidance document Calculation and Use of First Order Rate Constants For Monitored Natural Attenuation Rate Studies available on the internet at http://www.epa.gov/nrmrl/pubs/540sO2500/540SO2500.pdf KMEP has limited the updated evaluation to wells SP/M-1 and SP/M-9 and to MTBE based on the rationale that CDCs in the remaining Site wells are commingled with pollutants from adjacent sites. Despite high concentrations of benzene and TPHg, KMEP excluded these CDCs from the attenuation analysis on the basis that benzene has many non-detects (NDs) in the historical dataset, and that MTBE contributes to the quantification results for TPHg. Appendix E contains two graphs showing that MTBE concentrations in SP/M-1 and SP/M-9 will achieve the MTBE water quality objective (WQO) in 2039 and 2015, respectively. This updated estimate represents an increase in the time required to reach WQOs over that calculated in the 2008. The 2008 evaluation concluded that MTBE in SP/M-1 and SP/M-9 would achieve the MTBE WQO in 2009 and 2010, respectively. As required by the Central Valley Water Board Executive Officer's 25 March 2005 approval of KMEP's Cleanup Plan, the Annual Report lists MNA parameters collected annually since 2005. The data show that the highest concentrations of total organic carbon, chemical oxygen demand, ferrous iron, and methane are present in SP/M-1, SP/M-9, and SP/M-10. However, the Annual Report does not contain updated oxygen reduction potential (ORP), dissolved oxygen (DO) or electrical conductivity (EC) field parameter data. Sulfate (SO4) concentrations are up to three orders of magnitude higher in B zone and upgradient wells than in the SP/M-1 and SP/M-9, which are close to the source area. Nitrate (NO3) and total orthophosphate were generally absent or depleted in all wells. KMEP concludes that the decreasing petroleum hydrocarbon concentrations in SP/M-9 indicate that biodegradation is a principal mechanism for petroleum hydrocarbon attenuation in the plume interior. Central Valley Water Board staff also reviewed the 10 February 2011 Monitoring Well Installation Report (Report). Between 28 and 30 December 2010, KMEP installed two wells (SP/M-9B and SP/M-9C) at total depths of 33 feet and 66 feet bgs. Attempts to install the wells near SP/M-9 on the Nustar property started in October 2009, but were delayed by property access negotiations and tank farm maintenance for more than a year. The wells were eventually installed at an alternate location in the parking lot area of the KMEP property. Grab groundwater sampling 1998 was ND for benzene around this location. Therefore, the lot likely is not a source of groundwater pollution at this Site. KMEP plans to sample SP/M-9B and SP/M-9C during the first quarter of 2011.