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PROBLEM ASSESSMENT REPORT Moore Petroleum, Inc. 5941 F Street, Santa, CA NGA project NO, 10-90-481 Page 13 of the relative rate of movement of dissolved petroleum constituents compared to the rate of ground-water movement would r probably be a ratio of about 1.5 to 1,0 (i.e. petroleum constituents will migrate 1.5 times slower than ground water) . A rs-asonable estimate of the total volume of water necessary to remove all dissolved hydrocarbons (assuming that hydrocarbons are not added to the ground-water system) would be on the order of 3- 5 pore volumes of water (1 pore volume equaling the total volume of water contained within the dissolved hydrocarbon plume) . From examination of Figure 9, it is likely that removal of 1 pore volume of water would require about 350 days under Scenario '1. In order to attempt to decrease the length of time needed for -' ground-water cleanup, Scenario 2 (which involves injection of treated ground water from MW-1) was modeled. Figure 10 shows that all ground water within the dissolved plume would still be captured by. MW-1 under this scenario. Figure 11 shows a significant decrease in ground-water travel time from the down-gradient edge of the dissolved plume. Under this scenario, about'l pore volume of :ground:water within the -dissolved hydrocarbon :plume `would''be removed in less than.. 100-days, a significant decrease as compared to Scenario 1< Under Scenario 2 a conservative estimate of the time required for removal of dissolved hydrocarbons would be on the order of 300-500 days (3-5 pore volumes) . Based on a comparison of Scenario 1 and Scenario 2 it is clear that Scenario 2 will significantly decrease the time needed for ground- water remediation at the site. Because of the significant decrease in the amount of time needed to remediate ground-water at the site under Scenario 2, this scenario would likely be three to four times more cost effective than Scenario 1 for ground-water remediation at this site. Treatmentofground water 'extracted'by MW_1 (Scenario 2) would.-be by` aar' stripping: Air stripping would be accomplished by bubbling air via a small blower through e. 350-gallon tank to remove hydrocarbons. The 350-gallon tank would allow about 90 minutes resident time with a punping rate of 4 gpm. Effluent ground water -- from the bubbling tank will be sampled and analyzed for BTEX, EDB, EDC, and TPH prior to commencement of injection via MW-7. Should sampling show that a 90 minute resident time is not sufficient for complete removal of petroleum constituents, a second 350-gallon tank will be connected in series to the first tank to increase the efficiency of the air bubbler :system. Sufficient sLm. pling of the air bubbler system will be accomplished to ensure that ground water containing petroleum constituents will not be injected via 14W-7.