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monitoring, extraction, and injection wells; and installation of a bioremediation treatment system. The <br /> treatment system combined the use of proprietary additives with specialized oxygenation equipment to <br /> promote in situ biological breakdown of petroleum hydrocarbon constituents, MTBE, and degradation <br /> products (e.g., tert-butyl alcohol [TBA]). The system is described in detail in the Enhanced Bioremediation <br /> Pilot Study Implementation Report(Hart Crowser, 2004a) and the Enhanced Bioremediation Pilot Study <br /> Evaluation Report(Hart Crowser, 2004b). The system ran continuously from mid-January 2004 through <br /> June 2004, during which time a total of 86,000 gallons of augmented water was cycled. Results indicated <br /> that while the process successfully promoted biodegradation of petroleum hydrocarbons, hydraulic control of <br /> the upper silt unit (containing the majority of the remaining petroleum mass) was not practicable due to <br /> seasonal groundwater fluctuations and the fine-grained nature of the unit. Consequently, bioaugmentation <br /> was not further considered as a feasible cleanup approach. <br /> 2.7 Cleanup Plan and Addendum to Cleanup Plan <br /> In accordance with a June 15, 2005 letter request, a cleanup plan (Ash Creek, 2006a)was submitted to the <br /> Water Board on January 5,2006. The Cleanup Plan identified the steps to achieve cleanup: <br /> • Removal of ongoing sources of petroleum hydrocarbons to groundwater; <br /> • Addressing dissolved-phase petroleum hydrocarbon concentrations in groundwater; and <br /> • Groundwater monitoring to verify compliance with remedial action objectives(RAOs). <br /> Removal of the sources was largely achieved by the soil and SPH removal action conducted in 2003 by Hart <br /> Crowser. <br /> The following technologies were evaluated to address dissolved-phase petroleum hydrocarbon <br /> concentrations: <br /> • Dual-phase extraction; <br /> • "Passive"SPH removal; <br /> • Recirculation bioaugmentation; <br /> • Anaerobic in situ biologic treatment; <br /> • Bioventing and biosparging; <br /> • Monitored natural attenuation; and <br /> • Ozone injection. <br /> Based on the evaluation, a remedial alternative consisting of MNA coupled with SPH removal from <br /> ST/MW-1 was recommended. The following points supported the alternative. <br /> Revised Cleanup Plan Page 10 <br /> NuStar Stockton Terminal-Stockton,California <br /> November 7,2012 <br /> 1014-12 <br />