WORK PLANS - Laserfiche WebLink

Home Browse Search

Page 5 Cabral—Mc Adams Property April 28,2006 Job No. 1828-092.01 RESULTS AND DISCUSSION As shown on the attached Table I and on the laboratory reports, the data suggest that the petroleum hydrocarbon impairment to subsurface soils beneath the tank area is very limited and confined to the immediate vicinity of the former underground tank excavation. The results of the laboratory analysis for soils from Borings B2 showed TPH as gasoline was identified in the samples collected from depths of 15 and 20 feet at concentrations of 4,300 milligrams per kilogram(mg/kg) and 2,100 mg/kg,respectively. Analysis of soil collected from Boring B3 at the 25-foot interval revealed a concentration of 0.5 mg/kg TPH as gasoline. TPH as gasoline was not detected above the laboratory reporting limit of 0.5 mg/kg in any of the other soil samples tested. As shown in the appended laboratory data, the volatile organic compound(VOC)benzene was not detected above the laboratory reporting limit of 0.005 mg/kg in any of the soil samples submitted for analysis. Relatively low concentrations of toluene, ethylbenzene, and total xylenes were identified in the 15- and 20-foot soil samples collected from Boring B2 and the 25-foot soil sample collected from Boring B3. The oxygenate methyl tert-butyl ether (MTBE) was not detected in any of the samples analyzed from Borings B 1 or B2. Because the deeper samples collected from the borings did not contain petroleum hydrocarbons at concentrations above laboratory reporting limits, the likelihood of groundwater impairment attributed to former underground fuel tank is considered low. Because of the elevated concentrations of petroleum hydrocarbons detected in soils in a small area beneath the area of the former underground gasoline storage tank, it would appear that remedial efforts with regulatory agency oversight are warranted. Contaminated soil excavation and off- haul to an appropriate disposal facility would likely be the most feasible and timely remedial approach. Communications with San Joaquin County Environmental Health Service Division (SJCEHD) personnel have indicated that the SJCEHD can act as the lead agency for remedial oversight of petroleum hydrocarbon impacted to soils attributed to leaking underground storage tanks. PRELIMINARY REMEDIATION PLAN General The results of our investigations indicate that the vertical and horizontal extent of significant petroleum hydrocarbon contamination in soils beneath the area of the former underground storage tank is limited. Excavation and proper disposal of the petroleum hydrocarbon-impacted soil is considered the most practical remedial approach. As such we have developed the following preliminary remedial recommendations. Final remedial procedures can be established following discussions with the regulatory agency. Remedial soil excavation and disposal should be performed by a properly licensed hazardous materials contractor. Excavated soils should be properly handled, manifested and disposed in accordance with applicable regulations. The remediation contractor should prepare an Environmental Health and Safety Plan to protect workers from exposure to contaminated soils during site clearance and remediation activities.