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Mr. Nathan Crum - 2 - 5 April 2010 <br /> Valley Pacific Petroleum Service. <br /> potential to support the implementation of an air sparge/soil vapor extraction (AS/SVE) <br /> pilot test. Tables 12 and 13 summarize the data. Heterotrophic plate counts varied from <br /> 40 to 600 colony forming units per milliliter of water (cfu/mL). Valley Pacific concluded <br /> that the results of the baseline study are consistent with microbial activity occurring <br /> within the plume of contamination. <br /> Valley Pacific selected AS/SVE to remediate the CDCs in the groundwater and vadose <br /> zone based on the rationale that AS/SVE would likely enhance the biodegradation <br /> potential at the Site by increasing the dissolved oxygen (DO) levels in groundwater. <br /> Valley Pacific estimates that DO levels of greater than 1-2 mg/L can sustain aerobic <br /> degradation of compounds such as BTEX. Valley Pacific prepared the 9 March 2010 <br /> Workplan For Soil Vapor Extraction Pilot Test (Pilot Test Work Plan) in response to our <br /> request for an implementation work plan. <br /> The Pilot Test Work Plan proposes to conduct a 3-day SVE pilot test to evaluate the <br /> scope of a full-scale AS/SVE syst.c.m. The SVE well will be located 17 feet northeast of <br /> source area well MW-8 and will consist of one triple-nested SVE well cluster screened <br /> in zones where significant soil contamination has been observed. Extracted vapors will <br /> be treated by a thermal catalytic oxidizer. Vacuums will be alternately applied to each <br /> well within the cluster for 18 to 24 hours. Induced vacuum and flow rates will be <br /> monitored every 15 to 60 minutes during each test in the other two SVE wells in the <br /> cluster and in MW-8. Periodic photoionization detector (PID) and Tedlar® bag samples <br /> will be collected to analyze extracted vapors. A report will be submitted to Central Valley <br /> Water Board staff. <br /> We concur with the Pilot Test Work Plan. As stated in our 16 December 2009 letter, we <br /> request that Valley Pacific submit initial estimates of (1) the combined mass of the <br /> vapor, separate, and dissolved phases of hydrocarbon mass underlying the Site, (2) the <br /> mass of oxygen required to sustain microbial activity and achieve water quality <br /> objectives (WQOs), (3) any nutrient amendments that may be needed based on the <br /> four quarters of biodegradation indicator data, and (4) the time required to achieve <br /> WQOs. This information along with an implementation work plan for the full-scale <br /> AS/SVE system may be included in the SVE Pilot Test Report. <br /> Based on a 5 April 2010 telephone discussion with GZA regarding an reasonable <br /> estimate of the time required to complete the pilot study, please submit the SVE Pilot <br /> Test Report by 28 June 2010. If you have any questions regarding this letter, you may <br /> contact me at (91 '464-4811 or betaylor@waterboards.ca.gov. <br /> BRIAN TAYLOR, P.G. <br /> Engineering Geologist <br /> cc: Mr. Harlin Knoll, San Joaquin County Environmental Health Department, Stockton <br /> Mr. Gregory Stahl, Ground Zero Analysis, Inc., Escalon <br /> Mr. Patrick Riddle, Law Offices of Patrick D. Riddle, Acampo <br /> Mr. John Miller, Valley Pacific Petroleum Services, Inc., Stockton <br />