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F . d Beao` Al46. 474„ January 18z 2040 t c n a# s Va orJf;xtachon/,A�r,S ai eTest�vRe°ort aquate tor�e�riEiialEl �drocbon tmpa¢"ted soil beneath and along the north side of the �£.... exist=ing dispenser islazds. AIR SPARGE TEST RESULTS The field data obtained dining the AST is summarized in Table 2. Prior to sparging, dissolved oxygen (DO), measurements were obtained from wells AS-1 and MW-2. An initial AS-1 trajection pressure of 16pounds per square inch (psi)was established to evacuate water from the AS-1 Well casing. The air injection flowrate during the test ranged from 11 to 13.5 actual cubic feet per minute (acfm) at injection pressures ranging from 3 to 7.5 pounds per square inch. The groundwater depth in AS-1 prior to sparging was 57.8 feet bgs, with the AS-1 well screen set at 70.5 to 75.5 feet bgs. Vadose zone gas pressure responses were measured at well VW-1 which is screened from 50—65 feetbgs. Saturated zone pressure responses were monitored in wells MWW 2 and MW-3. The well screens for MW-2 and MW-3 are both fully submerged and exist from 75 to 90 feet bgs. Based on a measured groundwater depth of 57.8 feet bgs, the well screens for MW-2 and MW-3 were approximately 18 to 23 feet below the groundwater surface during the test. Pressure responses ranging from 0.02 to 0.04 inches of water were measured in well MW-2. No pressure responses were observed in well MW-3. The increasing and decreasing trend associated with the pressures measured in well MW-2 appear to be due to sparge-induced fluctuations in the groundwater elevation that may have occurred during the test. Dissolved oxygen (DO) increased in..well MW-2 from 0.9 to 1.6 ppm, a 77% increase during the 8 hour test. Well AS-1 did not r, charge for 45 minutes after the completion of sparging, therefore a groundwater sample codi'd,not be collected for DO measurement. The field data obtained from the AST suggest that airsparging is a feasible remedial alternative from an air flow perspective. Pressure response'and DO data suggests a radius of influence greater than 20 feet. DISTRIBUTION k A copy of this report should be forwarded to: Mr. Michael J. infurna, R.E.H.S. Mr. Mark List Environmental Health Division Regional Water Quality Control Board San Joaquin County Public Health Services - Central Valley Region P.O. Box 388 3443 Routier Road Stockton, California 95201-0388 Sacramento, California 95827-3098 A.\4741221VET AST Rpt.doc Job No. 1474.22 3 HORIZON ENVIRONMENTAL INC.