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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2008-0064 3
<br /> BP WEST COAST PRODUCTS
<br /> ARCO/BP STOCKTON TERMINAL#40T
<br /> ENHANCED BIOREMEDIATION PILOT STUDY
<br /> SAN JOAQUIN COUNTY
<br /> with potable water. Two hundred and forty gallons of the potassium
<br /> nitrate/sulfate/phosphate solution will be injected into each of the seven injection
<br /> wells at a rate of about 0.074 gpm during each of the 14 weekly applications for a
<br /> total dose of 23,520 gallons in the seven wells.
<br /> 9. The Discharger anticipates nitrogen and phosphorous depletion within the plume
<br /> because the microorganisms will take up these nutrients as the potassium
<br /> nitrate/sulfate/phosphate solution is injected and used by the microorganisms.
<br /> Potassium will replace sodium, which was used in the previous pilot study as the
<br /> counter ion in the nitrate/sulfate/phosphate solution, in order to avoid an
<br /> accumulation of residual sodium. No nutrients are expected to remain in the
<br /> subsurface because the nutrient addition rate is designed to match the
<br /> microorganism nutrient uptake rate.
<br /> 10.Using a pneumatic pump system, the Discharger will inject the nitrate/sulfate/
<br /> ammonium phosphate solution via above ground piping at a rate of 0.074 gpm per
<br /> well. Natural groundwater flow velocity and direction will distribute the solution into
<br /> the plume.
<br /> 11.Bench-scale testing and baseline monitoring has not been performed because the
<br /> effects of nitrate and sulfate application to groundwater, which occurred between
<br /> May and September 2004, are well documented for this site. The Discharger
<br /> conducted periodic sampling from 11 wells to monitor baseline concentrations for
<br /> geochemical parameters during the pilot study and to determine whether baseline
<br /> conditions were re-established after the test concluded. Monitoring during and after
<br /> the test was conducted for dissolved oxygen (DO), ferrous iron, total alkalinity,
<br /> nitrate, sulfate, sulfide, nitrogen, sodium, ammonium, total hardness, ortho-
<br /> phosphate, total dissolved solids, and total phosphorous.
<br /> 12.The results of monitoring, conducted until August 2005, showed brief exceedences
<br /> of nitrate as NO3, sulfate as S03, ortho-phosphate, and ammonium concentrations
<br /> above their respective baseline concentration. All exceedences occurred in
<br /> downgradient monitoring well AR/MW-1 A, but returned to baseline conditions for the
<br /> required constituents including nitrate, sulfate, sulfide, nitrogen, sodium, ammonium,
<br /> phosphate, and total phosphorous by November 2004. The baseline concentrations
<br /> for these eight constituents, as documented in the previous study, will serve as
<br /> baseline conditions for this proposed study.
<br /> 13.For this pilot study, the Discharger will monitor 17 downgradient monitoring wells
<br /> (AR/MW-1A, AR/MW-3A, AR/MW-5A, AR/MW-5B, AR/MW-5C, AR/MW-50,
<br /> AR/MW-8A, AR/MW-8B, AR/MW-8C, AR/MW-10A, AR/MW-11A, AR/MW-12A,
<br /> AR/MW-13A, AR/MW-13B, AR/MW-13C, AR/MW-23A, AR/MW-24A) and one
<br /> upgradient well (PS-P29). Samples will be collected weekly during the first month,
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