Laserfiche WebLink
I <br /> VVAPq& <br /> Working To Restore Nature <br /> December lb, 1992 <br />► Unocal Service Station No 69$1, Stockton, California <br /> Vapor Extraction <br /> Based on the results of the site assessment and vapor-extraction test, vapor extraction of <br /> gasoline hydrocarbons from the sediments underlying the existing fuel UST's and dispensers <br /> appears feasible Implementation of this alternative will require the installation of two <br /> additional shallow vapor-extraction wells, subgrade piping, and installation and operation <br /> of vacuum extraction and abatement system Removal of the existing UST's will not be <br /> required, and the method is less disruptive to business operations at the site than excavation <br /> This method is also not contingent on weather conditions and can be performed at any time <br /> during the year <br /> Ground-Water Monitorm <br /> 1 • <br /> Currently, dissolved gasoline and benzene, toluene, ethylbenzene, and total xylene isomers <br /> (BTEX) concentrations exceed Primary and Secondary maximum contaminant levels <br /> However, the concentrations have shown marked decreases, probably due to the adsorption <br /> of the dissolved compounds associated with the drop in ground water Therefore, at this <br /> time,we recommend that Unocal continue to monitor dissolved hydrocarbon concentrations <br /> and the groundwater gradient periodically until site closure Data obtained during the <br /> 1 monitoring will be used to verify 1) the ground-water gradient, 2) that dissolved gasoline <br /> and BTEX do not migrate farther offsite and 3) that the dissolved gasoline and BTEX <br /> concentrations in ground water decrease with the remediation of the overlying soil <br /> 1 <br /> 1 <br /> 38032 10 � <br />