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Mr. Chuck Carmel February 18, 1992 Page 3 During each test, the vapor flow rate (cubic feet per minute (c£m)] and vacuum (inches HZO) were measured at the extraction well Measurements of vacuum were also recorded from adjacent monitoring wells at the station 1n addition, air samples for hydrocarbons and tetraethyl lead were taken and analyzed by GTEL Environmental Laboratories and Brown and Caldwell Laboratories, respectively In addition, air samples were also analyzed for chlorinated compounds by Air Toxics, Limited. Vapor flow rates versus well vacuum data are presented in Table 1 and are illustrated on Figures 2, 3, 4, and 5 for ATR-2, ATR-3, ATR-4, and ATR-5, respectively During the pilot test, bag samples were collected at wells ATR-2,ATR-3,ATR-4, and ATR-5 The vapor wells were allowed to purge for at least 30 minutes before a bag sample was taken. In addition, testing for tetraethyl lead and chlorinated compounds was performed to determine the lead and chlorinated compound content in the subsurface soils. Results of hydrocarbon, chlorinated compounds, and Iead analysis are presented in Table 2. The pilot test was successful in extracting hydrocarbons from the soil vapors; therefore, in-situ vapor extraction is a viable method of remediating the soil beneath the site. The laboratory reported that the samples contained very low levels of lead [approximately 0.5 microgram ()i) lead, corresponding to 0 016 micrograms per liter (pg/1)] Chlorinated compounds were detected le in ATR-2, but they were at low levels and would not be expected to effect the treatment process that will be used at the site Laboratory reports and cham-of-custody documentation are included in Exhibit A The relatively low concentrations of total petroleum hydrocarbons (TPH) detected during the test, combined with the low TPH concentrations detected in past soil sampling, indicate that this site can be remediated in a relatively short time. Results of the vapor extraction test indicate that soil vapor can be extracted at moderate flow rates and low vacuums from existing morutormg wells. The radius of influence during vapor extraction was not determined due to the long distance between the tested wells In the future, it may be necessary to install one to two additional vapor extraction wells near the underground storage tanks We recommend that these wells be installed after the proposed system is operating, if needed. Three treatment options were considered at the site for soil remediation, including (1) carbon adsorption, (2) catalytic oxidation, and (3) thermal oxidation. Activated carbon treatment is not recommended for soil remediation since the total petroleum hydrocarbon as gasoline (TPH-G)concentrations were high and would result in high operating costs due to the frequent replacement of activated carbon. Thermal oxidation is not recommended at this site because of its operating cost and high visibility Brown and Caldwell 6461\CORRriSP6461-04 GI Consultants