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i <br /> �ssN� <br /> June 21, 1993 Working To Restore Nature <br /> ARCO Service Station No 2130 <br /> toluene, ethylbenzene, and total xylene isomers (BTEX) using EPA Methods <br /> 5030/8015/8020. Water samples were analyzed for TPHg and BTEX using EPA Methods <br /> 5030/8015/8020 and DO Copies of the laboratory reports and Chain of Custody Records <br /> are in Appendix A <br /> Results of Air Sggrge Pilot Test <br /> Ground-Water Elevation <br /> Changes in ground-water elevation as a result of sparging were recorded at various times <br /> 1 <br /> during testing. A review of data indicates that while sparging only at flow rates of 12 acfm <br /> or less, ground-water elevation rises were observed in all but one monitoring point At 10 <br /> to 12 acfm, ground-water elevation rises ranged from 0 74 to 0 06 feet, and in general <br /> 1 decreased at further distances from the sparge well. At increased flow rates of 18 to 21 <br /> acfm while sparging only, significant overall ground-water decreases were observed that <br /> ranged from 4 62 to 0 93 feet. These data suggest that at the higher flow rates either over- <br /> pressurization of the vadose zone or coalescing of air bubbles occurred, resulting in a <br /> depressed water table surface <br /> Sparge flow rates that ranged from 20 to 27 acfm were achieved during the combination <br /> 1 sparge/vapor-extraction test Test data shows reduced vadose zone pressure (less than 10 <br /> inches of water column) as compared to a maximum of 27 inches observed during the sparge <br /> only test. Ground-water elevation rises ranged from 0 28 to 0 19 feet <br /> 1 <br /> Ground-water elevation data observed during the 3 days of sparge and sparge/vent testing <br /> indicate that ground-water depression occurs at flow rates in the range of 20 acfm while <br /> sparging only Vapor extraction while sparging appears to have decreased the vadose zone <br /> 30003-8 9 <br />