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Stantec Work Plan for Amended Bioremediation Pilot Study BP Terminal 40T November 10, 2008 Groundwater samples from AR/MW-5A were first analyzed for methyl tert-butyl ether (MTBE) during the first quarter sampling event in 1999. MTBE maximum concentrations in groundwater samples collected during the quarterly monitoring program have ranged from 290,000 pg/L in November 1999 to 18,000 pg/L in October 2006. Bioremediation treatability studies were conducted by HLA in 1991. The study included the evaluation of existing microbial populations capable of degrading petroleum hydrocarbons, evaluation of soil chemistry factors, evaluation of hydrogen peroxide stability in soil, and evaluation of nutrient supplements to accelerate the degradation of petroleum hydrocarbons. The results of this study indicated that with the addition of proper nutrients and oxygen, biological treatment of impacted soil and groundwater is technically feasible. The results of this study are included in HLAs, Phase / Bioremediation Treatability Studies (HLA, 1991). EMCON conducted a biodegradation evaluation in 1996. The scope included sampling existing wells for biodegradation indicator parameters and evaluating data consistent with the Air Force Center for Environmental Excellence protocols for assessing natural attenuation. The data showed that the plume was stable and aerobic and anaerobic biodegradation processes were removing hydrocarbon mass and had the capacity to continue removing mass. Pilot testing for biodegradation enhancement included subsurface application of oxygen releasing compound installation and biosparging. The results showed that these processes were effective in improving dissolved petroleum hydrocarbons in the A- and B-zones, but the lateral influence was limited to a radius of a few ft from the well casing over the study period (IT, September 2001). Pacific Environmental Group (PEG) incorporated the results of the natural attenuation evaluation into the Corrective Action and Management Plan (1996). The plan recommended setting a trigger boundary at Stork Road, located down-gradient of the terminal lease area and an attenuation zone at the eastern boundary of the Port of Stockton property. Natural attenuation was proposed as the approach for addressing the petroleum hydrocarbon impacts within the attenuation zone. Impacts to groundwater within the terminal lease and up-gradient of the trigger boundary would also be addressed via natural attenuation. The plan proposed maximum contaminant levels (MCLs) as the water quality objectives at the trigger boundary and a monitoring and data evaluation plan was proposed to assess concentration trends (IT, September 2001). Stantec started an Iso-Gen feasibility test at the site on June 20, 2002. Due to safety concerns, Stantec on behalf of STTC, terminated the Iso-Gen feasibility test on July 25, 2002. It was discovered that during several Iso-Gen tests, the integrity of the wires within the wells had become compromised, causing the wires to short circuit, which created a potential explosive hazard. With this new information, the test was deemed unsafe due to the high hydrocarbon concentrations within the wells and the test being performed within an active terminal (SECOR, November 2002). URS conducted an enhanced bioremediation pilot study in 2004 and 2005. Approximately 720 gallons of an aqueous nitrate/sulfate solution were prepared at the site for each injection event. The aqueous solution consisted of 137 milligrams per liter (mg/L) of sodium nitrate, 400 mg/L of sodium sulfate, and approximately 500 grams of Miracle GRO that was added as a nutrient supplement. Once the solution was prepared, the injection system was started and the solution 40T Work Plan for Amended Bioremediation Pilot Study.doc 3