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CLOSURE REQUEST 5-31-94 <br /> to the high vapor pressure of gasoline (343 mm Hg at 680F) and <br /> high degree of fine sediments vapor extraction was proposed. A <br /> Pilot study was conducted, using vapor phase carbon scrub units <br /> and with a condensation unit, for on site rejuvenation of the <br /> carbon. These studies indicated that the vapor stream had too <br /> low of a BTU value to support thermal oxidation or internal <br /> combustion controls and indicated that the best cost option would <br /> be to use activate carbon vapor scrubs for BACT. The <br /> condensation unit was used during the initial phase of vapor <br /> extraction, as a moisture drop out and to perform on site <br /> rejuvination of the carbon units <br /> Once the vapor steam concentrations became low enough the <br /> condesation unit was no longer used and mobile carbon change-out <br /> services were utilized to change and transport the spent carbon <br /> for rejuvination <br /> As discussed in UPDATE STATUS REPORT #27, the gasoline range <br /> hydrocarbons found in the soil have been dramatically reduced, <br /> removing the lighter fractions of gasoline, ie . benzene has been <br /> removed, and only minor amounts of toluene, and ethylbenzene, see <br /> Tables 3 and 4 <br /> c) Groundwater remediation method(s) (free-product and dissolved <br /> constituents) <br /> No free-product was ever observed at this site . vapor extraction <br /> has reduced the dissolved constituents of gasoline in ground <br /> water from a high of 31, 000 ug/L TPH as gasoline at MW5 to below <br /> detection limits of 50 ug/L Also in MW5 benzene, toluene, <br /> ethylbenzene and xylenes have been removed or reduced from 5, 400 <br /> ug/L to below detection limits of 0 5 ug/L, from 7, 300 ug/L to <br /> less than 0 5 ug/L, from 180 ug/L to less than 0 5 ug/L and from <br /> 7, 800 ug/L to 2 5 ug/L respectively. <br /> d) Interim remediation actions undertaken <br /> Site remediation has consisted of the following <br /> 1) Removal of five 5 , 000--gallon underground storage tanks and <br /> all associated product lanes, <br /> 2) Excavation and on site aeration of approximately 1200 cubic <br /> yards of soil , and <br /> 3) In-Situ vapor extraction removing 18 , 255 pounds of gasoline <br /> and degraded gasoline range hydrocarbons <br /> e) Impact (potential and/or existing) of remedial actions <br /> on beneficial uses <br /> Utilizing vapor extraction technology the impact on potential and <br /> AP or existing beneficial uses was minimized Unlike pump and treat <br /> page24 <br />