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306620 Project Team March 28, 2007 ' Page 6 Robinhood Drive may be compromised. Tables and trend plots of the field data are included as Attachment A. Conclusions and Recommendations: ' At 40 to 60 psi of pressure, approximately 30 to 50 SCFM is being lost in the conveyance piping. Using the existing compressor, the system pressure is approximately 25 psi with three ' or more wells open on the South side of Robinhood Drive. • Pressure drop between the remediation compound and the wellhead ranges from 2 to 9 psi. Sparge well VEW-8B—where the pressure drop of 9 psi was observed—demonstrated an air flow rate of greater than 40 SCFM during the pressure reading. Pressure drop through the conveyance piping for a normally flowing well (20-30 SCFM) is 2 to 4 ' psi. • Flow rates ranged between 17 SCFM and 43 SCFM for wells located on the south side of Robinhood Drive. ' Using the existing air compressor, air flow was not observed in any wells north of Robinhood Drive. Pressure was measured at 35 psi at the wellhead of MW-23S. Pressure was observed ' in wells MW-19D and MW-25D when the valves were opened, but sparge pressure using the existing compressor was too low to establish flow at these wells. • Air flow can be established in wells on both sides of Robinhood Drive by using a higher- pressure capacity air compressor than is currently being operated at the site. Flow rate differences from the tests on February 1 and February 6, as well as water observed in the lines ' at MW-23S, indicate that a leak exists and that the conveyance line crossing under Robinhood Drive may be compromised. If the existing pipe size is sufficient, installation of an appropriate air pressure hose to MW-23S may be desired as part of the system upgrade. ' • Although the combination air sparge/groundwater monitoring wells MW-19S and MW-25S physically have piping at the wellhead, the wells are not connected to the sparge system. ENSR field personnel confirmed that the wells are not connected to the SVE system, either. • Air sparge wells MW-19D and MW-25D do not have pressure gauges installed at the well head. Space limitations in the well boxes prevent the addition of a rotameter. A larger well box such ' as a Christy Concrete Model B1730 (17 inch by 30 inch inside dimensions) should be installed to properly re-pipe the sparge well with appropriate instrumentation. A Trusted Global Environmental,Health and Safety Partner ' Sparge Flow Rate Summary_Stocklon 306620 Final.doc