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In regard to mounding, a water elevation was taken from each observation ' well at the beginning of the test, during the test, and just prior to turning off the air compressor A slight increase, ranging from 0 01 to 0 03 feet, was observed in each observation well except for piezometer P-4 The groundwater elevation measurements are tabulated as Table Three in the Tables Section ASE also attempted to introduce a helium tracer into t h e air sparge well However, all of the helium was used within the first minute of the test so no useful data was collected from this test The air sparge test was conducted until the positive pressure in each of ' the observation wells stabilized Although this occurred relatively early in the test, with only minor fluctuations as the test went on, the test was ' conducted for a period of 255 minutes The air sparge test showed that the sparging caused significant pressure increase within the vadose zone showing sufficient air flow through both the saturated and vadose zones ' for successful removal of hydrocarbons that may be released due t o sparging In addition, there was a slight mounding effect in monitoring wells as far away as 40-feet from the sparging well, indicating that infected air is moving through the saturated zone a significant distance from the air sparge well These results are surprising since there is a relatively thin saturated thickness beneath the site It is likely that this effect is caused by a coarser sand beneath a finer sand which is allowing air to push outward for a significant distance from the sparging well 5 -4 Dual-Phase Test On August 25, 2000, ASE senior project manager David Allen and Jonathan Walden of Solleco conducted a dual phase test for the site This test measured the influence of vapor extraction, as well as water removal, ' utilizing a liquid-ring pump capable of delivering up to 28 inches mercury of vacuum to a well containing a screened interval above and within the water bearing zone Using the data collected from the step-drawdown and constant rate pumping tests, it was determined that the extraction well would provide a drawdown of 2 8-feet at a pumping rate of approximately 1 65 gallons per minute Therefore, the vacuum hose was installed into the extraction well 4 3-feet below the water surface to allow for the expected drawdown plus a submerged depth of approximately 1 5- feet The test began at 6 00 and continued until 17 30 when it was obvious that stabilization of the observation wells had occurred The following conditions were achieved during the test Prank's One Stop Interim Remediation System Workplan — September 2000 -12-