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• 40 CONCLUSIONS AND RECOMMENDATIONS 41 AASF Areas of concern identified at the AASF comprise the condition of gioundwatei in the area of the former 5,000-gallon fuel USTs removed in 1990, and a minor release of fuel to soil occurring rn April 2002 The findings of gioundwatei monitoring identified 0 110 mg/L. of TPH-g in one gioundwater sample This represents the second detection of trace concentrations of TPH-g. the fust having occurred in May 1996 These detections indicate that very little residual contamination is likely present from the former USTs The sporadic detection of trace conceritiations of TPH-g in the gioundwatei, without related aromatic and caicnnogemc compounds does not reflect a significant risk to human health or the environment Therefore, Versar reconnnends no fi.irther action for the unauthorized release fiom the minor fuel spill The piesence of low concentrations (less than 500 mg/kg) of extractable TPH in soils between the surface and five feet bgs at the location of the minor fuel spill does not present a significant threat to human health or the environment The results of soil sampling indicate that the 1111pacted soils are not present at the 10-foot level and below Vertical inigiation of heavy hydrocarbons is typically limited to the soluble fraction, and is generally considered not a concern in shallow soils at concentrations less than 1,000 mg/kg (RWQCB, 2003) Therefoie, Veisar teconunends no fiu-ther action for the unauthorized release fiom the minor fuel spill 42 CSAIS Areas of concent identified at the CSMS aie, petroleum hydiocaibons beneath the vehicle wash rack in the north portion of the building elevated metals and petroleum hydrocarbons along the north facility boundary, petroleum hydiocaibons near the waste storage area, heav} metals near the sandblasting area, and pavement upwelling in the vehicle storage area east of the building Laboratory analysis did not detect concentrations of extractable hydiocarbons or PCBs in any of the samples collected from boring B29, located north of the vehicle wash rack in the CSMS building Previously identified hydraulic oil contamination, detected at 10 feet bgs in born- B7, appears to be limited to shallow soils in the vicinity of that boring No further investigation is recommended fon the vehiclewash rack area A tiace concentiation of hydraulic oil-weight petroleum hydrocarbon pieNiousl5 detected at the former hazai dous material storage shed was not confirmed during follow-up sainpling Two soil samples collected from boring B10b did not contain concentrations of extractable hydrocarbons, and metals concentrations were below regulatory guidelines No further investigation is reconnrnended for the foisnei hazaidous materials storage aiea One soil sample was collected from boring B11, located neat the sandblasting area Laboiatory analysis did not detect actionable concentiations of heavy metals in the sample 104700 4766 230/085EPT2004 11