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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2008-0064 2 BP WEST COAST PRODUCTS ARCO/BP STOCKTON TERMINAL#40T ENHANCED BIOREMEDIATION PILOT STUDY SAN JOAQUIN COUNTY 13,000 pg/I, ethylbenzene up to 3,100 µg/I, xylenes up to 14,000 µg/I, methyl tertiary butyl ether (MTBE) up to 28,000 pg/I, and tertiary butyl alcohol up to 3,000 µg/I. 5. The plume at the site is anaerobic. The Discharger proposes an expanded pilot study to evaluate injection of potassium nitrate, potassium sulfate, and potassium phosphate dibasic to bioremediate the petroleum hydrocarbon pollution. The Discharger will do weekly slug injections of the potassium nitrate/sulfate/phosphate substrate (described further in Finding 8 below) for three months with groundwater monitoring until concentrations of nitrate, sulfate, and any byproducts therefrom return to baseline levels. Each slug injection will be about 18 hours. If analytical data show that the microorganisms have used up the injected nitrate and sulfate before the end of one year, the Discharger has proposed additional injections for up to three months. The pilot study will be concluded when the amendments and byproducts do not exceed baseline levels. 6. The Discharger proposes to inject substrates into a total of seven wells. The substrates will be injected into existing wells IS-1, IS-2, and IS-3, which were previously used for the ISO-GEN pilot study, and into four proposed new wells in the vicinities of existing monitoring wells AR/MW-3A, AR/MW-8A, AR/MW-13A, and AR/MW-24A. The Discharger proposes the injection of the potassium nitrate/sulfate/phosphate solution to stimulate anaerobic biodegradation of the petroleum hydrocarbon pollution. A potassium bromide tracer will be used to assess the rate of transport. The well locations were selected based on location and spacing within the plume, and the injections target the A zone pollution. 7. The remedial process for hydrocarbon plumes depends upon stimulating growth of indigenous microorganisms. The microorganisms obtain energy by oxidizing one compound and reducing another compound. Different amounts of energy can be obtained from different compounds. The first compounds to be utilized are those that provide the most energy. Microorganisms will consume carbon (i.e., petroleum hydrocarbons) first using oxygen as the electron acceptor until it is depleted, since oxygen provides the most energy. After oxygen depletion, a succession of anaerobic microorganisms becomes dominant, oxidizing (consuming) carbon and reducing the specific compounds, such as nitrate and sulfate, upon which their metabolism depends. In general, nitrate and sulfate are the next compounds to be reduced after oxygen. Iron also is reduced, but is not proposed for injection at the site based on potential for clogging the water bearing zone. 8. The Discharger proposes to inject the potassium nitrate, potassium sulfate, and potassium phosphate dibasic solution at concentrations of 140 milligrams per liter (mg/L) of nitrate as NO3, 25 mg/L of phosphate, and 400 mg/L of sulfate. The injection solution will be prepared by mixing nitrate as NO3, phosphate and sulfate