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Report-Pilot Remedial System Test Page 22 Former Manna Pro Site ' Project No 2011 July 31,2000 ' Based upon the above assumptions and those noted in Table 3, the daily hydrocarbon removal rates were as follows ' Table - Hydrocarbon Removal Rates Date Removal Rate(lbs/day) 5/23/00 2 1 5/24/00 1 1 5/25100 2 3 5/30100 19 5/31/00 47 6/l/00 07 These low removal rates were anticipated due to the 10 feet of water column that currently lies above the zone of intensely gasoline impacted soil (i e 35 to 45 feet bgs) As was noted above, the current depth to groundwater is about 25 feet bgs, an historic high for this site For comparison, at the time of the pilot work completed in 1994 by Groundwater Technologies, the groundwater surface was about 40 bgs, or 15 feet lower than at the present time During the vapor extraction portion of the GTI pilot test, the gasoline concentration in the extracted vapor reportedly was 280 mg/l At the extraction rate of 15 scfm which was used by GTI, these figures convert to a gasoline extraction rate of about 376 lbs/day Applying the same gasoline vapor concentration to an air extraction rate of 45 scfm, the largest sustainable extraction rate for this pilot test, the gasoline removed would be about 1,128 l bs/day It is clear that with the groundwater level at, or near, record highs the vapor extraction alone will not be an effective remedial measure In order for vapor extraction to be effective as a stand-alone remedial measure, it will be necessary to remove hydrocarbons from relatively deeply beneath the groundwater surface This can be accomplished by two methods First, and as previously proposed, air sparging will tend to mobilize ' submerged hydrocarbon molecules and bring them to the surface where they may be captured by vapor extraction Secondly, as groundwater elevation recedes from its current high level, the gasoline vapor concentration in the extracted vapor will increase as more highly contaminated soil is exposed This is clearly demonstrated by the GTI data Ideally, a combination of both of these feature will take place Radius of Influence During the period when the pilot vapor extraction equipment was in operation, nearby observation wells were monitored with magnahelic gauges The field data clearly show that substantial vacuum was measurable in wells OB-4 and OB-5 when vacuum was applied by the ICE to the vapor extraction well, VEW-1 The maximum pressure draw- down on OB-4 was 3 5 inches of water while that in OB-5 was 2 0 inches These test- maximum measured vacuums were plotted on a log-normal scatter chart graph (see figure 8) and the plotted points connected with a projected linear regression line extending to the 1 2937 Veneman Ave ,#13240 Geo-Phase Environmental Inc Phone(209)569-0293 Modesto, CA 95356 Fax(209)569-0295