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ATLANTIC RICHFIELD COMPANY, STOCKTON TERMINAL#40T, ENHANCED <br /> BIOREMEDIATION PILOT STUDY, SAN JOAQUIN COUNTY <br /> The Atlantic Richfield Company(Discharger) owns and operates bulk fuel terminal#40T at 2700 <br /> Washington Street in Stockton. Three other bulk fuel terminal companies operate on the same parcel. <br /> Operations at the site have resulted in petroleum hydrocarbon pollution in each of the four identified <br /> groundwater bearing zones. Groundwater contains total petroleum hydrocarbons (TPH) as gasoline up <br /> to 240,000 micrograms per liter(µg/1), TPH as diesel up to 140,000 µg/l, benzene up to 27,000 µg/1, <br /> toluene up to 22,000 4g/1, ethylbenzene up to 3,500 µg/1, xylenes up to 15,000 4g/1,methyl tertiary butyl <br /> ether(MTBE)up to 290,000 µg/1, and tertiary butyl alcohol up to 2,800 µg/1. The Discharger proposes a <br /> one-year pilot study to evaluate injection of nitrate and sulfate to bioremediate petroleum hydrocarbon <br /> pollution. The plume at the site is anaerobic. The Discharger proposes to inject a sodium nitrate <br /> solution at a concentration of 137 milligrams per liter(mg/1) and a sodium sulfate solution at a <br /> concentration of 400 mg/l. A total of about 8,900 gallons of the sodium nitrate and sodium sulfate <br /> solution will be injected into each of the three injection wells at a rate of about 0.22 gallons per minute <br /> during each of the weekly slug injections. It is estimated that there will be no excess of nitrate or sulfate <br /> in the subsurface because the proposed injection volume is set at about half of the calculated uptake rate <br /> by the microorganisms. If results show that the injection of sodium nitrate and sodium sulfate is <br /> effective as a remedial alternative, the WDRs allow the Discharger to propose additional injections <br /> subject to Executive Officer approval. The WDRs require extensive monitoring to evaluate the effects <br /> of the proposed injection. <br /> DLL <br /> 9/24/03 <br />