SITE INFORMATION AND CORRESPONDENCE

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Mr. Nathan Crum - 2 - 16 December 2009 Valley Pacific Petroleum Sen Valley Pacific selected air sparge/soil vapor extraction (AS/SVE) to remediate the COCs in the groundwater and vadose zone based on the rationale that AS/SVE would likely enhance the biodegradation potential at the Site by increasing the dissolved oxygen (DO) levels in groundwater. Valley Pacific estimates that DO levels of greater than 1-2 mg/L can sustain aerobic degradation of compounds such as BTEX. Starting in the fourth quarter of 2008, biodegradation indicator parameter monitoring was conducted in five wells for a year-long assessment of the baseline bioremediation potential to support the implementation of an AS/SVE pilot study. MW-12 is upgradient, MW-6R is in the heart of the plume, MW-2 and MW-3 are cross gradient, and MW-10 is downgradient. Quarterly monitoring was conducted in October 2008, and January, April, and July 2009. The results are documented in the 1 December 2009 Biodegradation Parameters Baseline Study (Study). SPH was present in MW-6R in April 2009, so this well was not sampled during April 2009. Previous laboratory analytical results showed that the SPH is high sulfur diesel similar to the type used in California prior to 1993. During the other three quarters, MW- 6R had the highest concentrations of organic carbon, respiration by-products, anaerobic terminal electron acceptors, and oxygen demand, as well as the lowest concentrations of DO. The oxygen-reduction potential (ORP) was generally lowest in MW-10. Conversely, this well also had the highest DO concentrations. The highest concentrations of nutrients were present in upgradient well MW-12. Heterotrophic plate counts varied from 40 to 600 colony forming units per milliliter of water (cfu/mL). Our comments are presented below. 1. We concur that AS has the potential to enhance biodegradation by increasing the DO concentration. However, before the remedy can be implemented we will need Valley Pacific to submit an Implementation Work Plan detailing schematics of the proposed system design. The Implementation Work Plan must also contain calculations and results for initial estimates of (1) the combined mass of the vapor, separate, and dissolved phases of hydrocarbon mass underlying the Site, (2) the mass of oxygen required to sustain microbial activity and achieve water quality objectives (WQOs), (3) any nutrient amendments that may be needed based on the four quarters of MNA data, and (4) the time required to achieve WQOs. 2. The MNA data indicate that the biodegradation parameters at the Site are typical of most established contaminant plumes. However, MW-3 and MW-4 are the only two wells in which dissolved plume concentrations have decreased since monitoring began. There is potential for biodegradation, but the nutrients required to sustain biodegradation have been depleted, and bacterial counts are uncharacteristically low. In addition, SPH has been present at the Site since 1997 despite continuous removal. These indicators show that biodegradation has stalled and/or there is an active ongoing source of petroleum hydrocarbons, as discussed in Comment No.3 of our 3 July 2008 letter. Implementation of a remedial action will be necessary to meet WQOs. However, Valley Pacific must also modify operations to prevent fuel discharges to the ground surface during fuel transfers to eliminate any ongoing sources.