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Stantec Site History and Previous Investigations BP Stockton Terminal No. 40T June 17, 2009 manifolds, and a timer. The East System is capable of delivering 15 scfm of ozone to four or five OS wells simultaneously through piping connected to each individual OS point. The OS system piping is equipped with a manifold that will allow for the adjustment of the individual well injection rates. The West System, which is located at and in the vicinity of the Tesoro Terminal, began operation on November 15, 2004. This system is connected to 31 "A" zone OS wells (OS-1 through OS-31) and 8 "B" zone OS wells (OS-16 through OS-8B). The West System is constructed with the same specifications as described above for the East System. BP Stockton Terminal No. 40T Summary Soil and groundwater investigations, at and in the area of BP Stockton Termianl No. 40T (site), have been conducted by Woodward-Clyde Consultants, Levine and Fricke, Environmental Strategies Corporation, Kleinfelder, Hydro-Search, Inc., Harding Lawson Associates (HLA), Hart Crowser, EMCON, IT Corporation, Stantec, and URS for various site tenants beginning in 1984. Assessment activities conducted specifically on-site include HLA (1990 and 1991), IT Corporation (IT), and URS. Quarterly groundwater monitoring has been conducted since 1993 on selected monitoring wells at the site as part of the overall monitoring program performed for the STTC. Groundwater samples have been collected from groundwater monitoring well AR/MW-5A, located in the area of highest dissolved petroleum hydrocarbon concentration quarterly since 1993. Benzene concentrations in groundwater samples collected from AR/MW-5A during the quarterly monitoring program have ranged from 24,000 micrograms per liter (Ng/L) in September 1993 to 290 pg/L in May 2006. Benzene was detected at a concentration of 720 pg/L during the fourth quarter 2006 sampling event. 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 1 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 0040T Site History and Previous Investigations.doc 2