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Ms. Kasey Foley
<br /> Fuel System Upgrade Report
<br /> September 22, 2003
<br /> Page 6
<br /> Concentrations of MTBE, TBA, and TAME showed noticeable declines during and after tank pit
<br /> dewatering. Concentrations of MTBE, TBA, and TAME in the final Baker tank sample (BT-2) were
<br /> reported at 13,000 ug/L, 1,900 ug/L, and 35 ug/L, respectively. A TPHg concentration of 2,800 ug/L
<br /> was also reported in sample BT-2.
<br /> Between June 2 and June 16, 2003, a total volume of 199,090 gallons of water was extracted from
<br /> the tank pit excavation. Warren E. Gomez Trucking transported the purged groundwater from the
<br /> site to InStrat, Inc. in Rio Vista, California for treatment. Copies of the Non-Hazardous Waste
<br /> Manifests and water treatment certificates are included in Attachment C.
<br /> Mass Removal of MTBE
<br /> Based on analytical results derived from groundwater samples collected prior to UST removal
<br /> activities, during dewatering of the tank pit excavation, and after dewatering of the tank pit
<br /> excavation, an estimated total mass of MTBE removed was calculated. During the two-week period
<br /> of groundwater extraction from the tank pit excavation between June 2 and 16, 2003, an estimated
<br /> 243.8 pounds (39.5 gallons) of MTBE were extracted from the site. Estimated MTBE mass removal
<br /> calculations are included in Table 3.
<br /> SUMMARY AND CONCLUSIONS
<br /> Fuel system upgrade work at the site included the removal of one 15,000-gallon UST and two
<br /> 10,000-gallon USTs; replacement of product line piping, dispenser pans, and turbine sumps; the
<br /> installation of one replacement double-walled, fiberglass 15,000-gallon UST and two replacement
<br /> 10,000-gallon USTs; and the modification of the vent line slope.
<br /> Soil impacts have been observed beneath the site. Soil samples collected beneath the dispenser
<br /> islands and product lines did not contain TPHg or BTEX above laboratory reporting limits; however,
<br /> maximum concentrations of MTBE and TBA were detected at 4.5 mg/kg and 12 mg/kg, respectively
<br /> (D1-4.0'). Soil samples collected from the sidewalls and beneath the USTs contained maximum
<br /> concentrations of TPHg (2.2 mg/kg, T2-10'), benzene (0.007 mg/kg, T8-10'), MTBE (36 mg/kg, 1-
<br /> 10'), TAME (0.11 mg/kg, T1-10'), and TBA (52 mg/kg, T3-10'). Based on soil analytical results, the
<br /> highest concentrations of petroleum hydrocarbons adsorbed to soil appear to be located in the
<br /> northwestern corner of the UST pit.
<br /> Groundwater beneath the site has also been impacted. Concentrations of MTBE, TBA, and TAME
<br /> up to 510,000 micrograms per Liter (ug/L), 79,000 ug/L, and 1,500 ug/L, respectively, were reported
<br /> in grab groundwater sample W1 from tank pit observation well TP-1 prior to UST removal and tank
<br /> pit dewatering activities. During dewatering activities, approximately 199,090 gallons of impacted
<br /> water and a calculated estimate of 243.8 pounds of MTBE were removed from the tank pit
<br /> excavation. Concentrations of MTBE, TBA, and TAME in water samples collected following
<br /> dewatering activities were significantly lower in comparison to initial concentrations detected prior to
<br /> UST removal and tank pit dewatering activities, which suggests that a significant amount of
<br /> petroleum hydrocarbon and fuel oxygenate impacts have been removed.
<br /> Due to the presence of petroleum hydrocarbons and fuel oxygenates in soil and groundwater
<br /> beneath the site, SECOR submitted an Underground Storage Tank Unauthorized Release with the
<br /> 32262 Fuel Line&USTs Upgrade Report.doc SECOR International Incorporated
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