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' Page 3,CAN,ARCO m,mi wan groundwater sample results have been similar to those in late 1993 The absence of contamination in MW-1 may be due to the 1993 rise in groundwater, the top of the screened interval in this well is now more than 10 feet below the soil/water interface ' Most of thepurl,r e and dulling rinseate water was disposed of in the city sewer system in January 1994, but purge water generated in September 1994 is presently stored in 55-gallon drums on site ' 2.4 Vapor Extraction Test An 8-hour vapor extraction test of remedial well VW-1 was conducted in December, 1993 to ' assess the feasibility of vapor extraction technology to remediate soil contamination at this site A Vacleen 1000 internal combustion engine was used in the test A portable flame ionization detector was used to measure the concentration of hydrocarbon vapors at the well head during the test, and three tedlar bag samples were collected for laboratory analysis of TPH-g and BTE&X Vacuum gauges on the well and on monitoring well MW-1 measured the vacuum created by the 100-cfm extraction unit(flow rates were approximately 50% of the rated capacity of the unit) PID readings exceeded 10,000 ppm (molar volume) throughout the test, and laboratory results indicated vapor concentrations ranging from 20,000 to 38,000 ppm (Table 3) Based on these results, Geological Audit Services and EHD concluded that VW-1 is suitable for vapor extraction Vacuum pressure at MW-1 waN less than 0 2 inches of water throughout the test, suggesting that this well is beyond the effective radius of influence of VW-1 2.5 Underground Storage Tank Replacement ' 1n Apnl and May, 1994, six underground storage tanks and related piping were removed from the site and replaced with two 12,000-gallon doubled-walled tanks (Figure 4) One tank is ' divided into three compartments (5,000, 5,000, and 2,000 gallons) Two standpipes were also installed for future use in the installation of vapor extraction wells, should they be necessary Soil samples were collected from beneath the tanks and piping and analyzed for a variety of ' contaminants (Table 4) ' Hydrocarbons were detected in 9 of 15 samples from the tank and piping excavations, but concentrations were generally low The conditions of the tanks were not described in Geological Audit's tank removal report, but these low concentrations could have occurred as a result of ove3Niil during tank filling, ana do not necessarily represent important releases