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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2003-XXXX 3 ATLANTIC RICHFIELD COMPANY STOCKTON TERMINAL#40T ENHANCED BIOREMEDIATION PILOT STUDY SAN JOAQUIN COUNTY 10. Bench-scale testing has not been performed because nitrate and sulfate have both been used at numerous sites and the anaerobic biodegradation process of petroleum hydrocarbons by naturally-occurring microorganisms has been well documented. Microorganisms degrade petroleum hydrocarbons through natural biological processes and do not create reaction products. There is potential for aquifer clogging from the reduction of sulfate to sulfide and nitrate to ammonium. Therefore,the Discharger will monitor for these constituents and total dissolved solids. 11. The Discharger will monitor 10 downgradient monitoring wells (AR/MW-1A, AR/MW-3A, AR/MW-5A, AR/MW-5B, AR/MW-5C,AR/MW-50, AR/MW-8A, AR/MW-10A, AR/MW-11A, and AR/MW-12A) and one upgradient well (PS-P29). Samples will be collected weekly during the first month, monthly during the first six months, and quarterly thereafter during the pilot test for the parameters outlined in the attached MRP No. R5-2003-XXXX. In addition, the Discharger will collect baseline samples from AR/MW-IA to determine natural variation of nitrate, sulfate, sulfide, nitrogen, sodium, ammonium,phosphate, and phosphorous. The Discharger will conduct three sampling events to monitor for these constituents and propose baseline concentrations for Executive Officer approval prior to injection. 12. If the levels of nitrate and sulfate in AR/MW-3A drop below baseline levels and upon written Executive Officer approval, the Discharger may begin another three-month cycle of the injection with up to double the original injection volumes (i.e., the level the Discharger calculated as the actual uptake rate of the microorganisms). 13. In the event that concentrations of nitrate, sulfate,nitrogen, sodium, ammonium, sulfide, phosphate, and/or phosphorous in downgradient well AR/MW-IA exceed approved baseline concentrations by more than 20 percent, injections will cease and the Discharger will collect a confirmation sample. If the exceedance is confirmed, the Discharger will cease the sulfate and nitrate injection and continue monthly monitoring of well AR/MW-1 A. Monthly monitoring will continue for three months so there are enough data to establish a trend. If the levels,based on the concentration trend, are more than 20 percent above baseline levels, the Discharger will install a groundwater extraction and treatment system. The Discharger will extract groundwater from one to three extraction wells, treat it, and then discharge it to the sanitary sewer or haul it off-site for disposal. The Discharger will also monitor well AR/MW-lA every other week until the levels decrease to baseline levels and then monthly for six months to confirm concentrations remain below baseline levels. 14. Groundwater consistently flows in an easterly direction at an average gradient of 0.0064 feet per foot. AR/MW-lA was selected as the well to evaluate for exceedences because it is about 450 east of the proposed injection wells.