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INFORMATION SHEET <br /> ORDER NO. R5-2003-XXXX <br /> ATLANTIC RICHFIELD COMPANY <br /> STOCKTON TERMINAL#40T <br /> ENHANCED BIOREMEDIATION PILOT STUDY <br /> SAN JOAQUIN COUNTY <br /> Atlantic Richfield Company(ARCO) owns the bulk fuel terminal at 2700 Washington Street <br /> in Stockton(site). ARCO is a member of the Stockton Terminals Technical Committee, <br /> which was formed with three other bulk fuel terminal companies on the same assessor's <br /> parcel to address site wide groundwater pollution. A majority of the mass of petroleum <br /> pollution is in the A water bearing zone which is about 5 to 20 feet below ground surface. <br /> ARCO proposes to inject sulfate,nitrate, and ammonium phosphate into the A water bearing <br /> zone through three wells to enhance anaerobic biodegradation. The remedial process for <br /> hydrocarbon plumes depends upon stimulating growth of indigenous microorganisms. The <br /> microorganisms obtain energy by oxidizing one compound and reducing another compound. <br /> Different amounts of energy can be obtained from different compounds. The first compounds <br /> to be utilized are those that provide the most energy. Microorganisms will consume carbon <br /> (i.e.,petroleum hydrocarbons) first using oxygen as the electron acceptor until it is depleted, <br /> as oxygen provides the most energy. After oxygen depletion, a succession of anaerobic <br /> microorganisms becomes dominant, oxidizing (consuming) carbon and reducing the specific <br /> compounds, such as nitrate and sulfate,upon which their metabolism depends. In general, <br /> nitrate and sulfate are the next compounds to be reduced after oxygen. Iron is also reduced, <br /> but is not proposed for injection at the site based on potential for clogging the water bearing <br /> zone. A nitrogen and phosphorous injection(Miracle-Gro) is also proposed to aid in the <br /> growth of the microorganisms. <br /> ARCO proposes weekly slug injections of ammonium phosphate, nitrate and sulfate <br /> substrates for three months into three wells. Groundwater samples from 10 downgradient <br /> wells and one upgradient well will be collected weekly during the first month, monthly for the <br /> first six months and quarterly thereafter to evaluate the effectiveness of the injection. <br /> As part of the monitoring,baseline levels will be determined for monitoring well <br /> AR/MW-lA. If concentrations of nitrate, sulfate, nitrogen, or phosphorous increase to 20 <br /> percent or more above the baseline levels,ARCO will cease the injection and collect a <br /> confirmation sample within seven days of receiving results of exceedence. If the exceedence <br /> is confirmed, ARCO will implement a contingency plan within 30 days of sampling <br /> confirmation. <br /> The purpose of the pilot study is to evaluate the effectiveness of the injection of sulfate and <br /> nitrate to enhance anaerobic biodegradation. <br /> DLL 9/24/03 <br />