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,r <br /> { Project A109.04 30 March 1992 <br /> Ultramar based on groundwater considerations. Hydrocarbon vapor <br /> concentrations at these wells had been only 10 ppm or less. When these <br /> wells were open to the system, the vacuum decreased to about 5" Hg. <br /> Air bag samples of the system influent and effluent were obtained on 19 <br /> March to determine the impact of introducing the two low concentration <br /> wells to the system. The results indicated the ground dilution <br /> produced by these wells reduced the influent loading to about 791 ppm, <br /> or approximately 16 pounds per day. <br /> Following the adjustments on the 19th, the system was again fully <br /> monitored on 24 March 1992. Concentrations at the various extraction <br /> wells were relatively stable compared to the last full monitoring with <br /> the concentration at the single highest well , MW-19, increasing <br /> slightly to 2,250 ppm. <br /> Well MW-10, located near the center of the system, was opened on the <br /> 24th due to an increase in concentration. A slight increase was also <br /> evident at recently opened well MW-35. With the openings made on the <br /> 19th, 6 of the system's 10 extraction wells were open on the 24th. <br /> The increased dilution from the ground caused the influent <br /> concentration to decrease to about 500 ppm and the vacuum to decrease <br /> to 4.1" Hg. Influent benzene was barely above detectable limits. <br /> From 16 August to 24 Mauch, the system operated 176 days extracting <br /> approximately 7,552 pounds (approximately 1,218 gallons) of <br /> hydrocarbons and 23.5 pounds of benzene from the soil . <br /> Please call if you have any questions. <br /> Sincerely, <br /> EVAX Technologies, In/c�. <br /> q�"A <br /> Robert A. Nunes <br /> Project Engineer, REA <br /> Attachments: <br /> 1) Site Plan <br /> 2) Extraction Well Summary <br /> 3) Incinerator System and TVH Summary <br /> 4) Benzene Summary <br /> 5) Influent Chromatogram (EVAX Lab) , 11 March 1992 <br /> 6) Effluent Chromatogram (EVAX Lab) , 11 March 1992 <br /> 7) Influent Chromatogram (EVAX Lab) , 19 March 1992 <br /> 8) Effluent Chromatogram (EVAX Lab) , 19 March 1992 <br /> 9) Influent Chromatogram (EVAX Lab) , 24 March 1992 <br /> 10) Effluent Chromatogram (EVAX Lab) , 24 March 1992 <br /> - 2 - <br /> I <br />