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CHIP Addendum:Former Fu*ig Station, 7500 West Eleventh Street, Tracy, 6MO' Page 21 3.0 CONCLUSIONS Following is a summary of the principal conclusions that have been presented in this Corrective Action Plan Addendum. • The maximum remaining area of the site that is affected by LNAPL is estimated to be 9,200 ft . The area is estimated to extend 115 ft. in the south to north direction from a point down-gradient of Monitoring Well MW-13 to a point up-gradient from Monitoring Well MWFP-3. (The well locations are shown on Figure 1.) In the east to west direction, the affected area is estimated to have a width of some 80 ft. that extends westward from Monitoring Well MWFP-1. • The total mass of contaminants in the subsurface in the area affected by LNAPL is estimated to be 4,625,025 grams. Of that total, 3,179,746 grains (68.75%) are in the form of LNAPL, which has a volume of 1,050 gallons, 2,105,265 grams (45.52%) are adsorbed onto soil and only 54 grams(0.0012%) of the mass are dissolved in groundwater. • It is estimated that the construction of the proposed extraction trench and pumping 10,000 gallons of groundwater from it will remove 138,324 grams of contaminants adsorbed onto soil and 1.81 grams of dissolved contaminants. Due to the substantial lack of available theoretical or empirically derived methods for making a priori estimates of the fraction of LNAPL that may or may not be extractable, it is difficult to assess by analytical procedures the mass or volume of contaminant in the form of LNAPL that can be removed from the subsurface by pumping from the extraction trench.. Our estimates using the available theoretical and empirical methodologies range from 525 gallons to 1,050 gallons, the latter amount being 100% of the LNAPL that is estimated to be floating on the groundwater in the affected area. • Our evaluations have demonstrated that the total mass of contaminants that can be removed from the subsurface by the proposed remediation system is not an effective measure of its ability to achieve its objectives. The principal objective should be to remove all of the LNAPL from the affected areas so that aerobic processes of natural attenuation of contaminant concentrations can be initiated. The anaerobic processes that currently prevail in the area affected by LNAPL are actively remediating the groundwater but the rate of total contaminant load reduction is much slower than the rate that occurs when aerobic conditions prevail. After the groundwater condition passes to an aerobic state, complete remediation of the Navarra Site by natural processes can be expected within a reasonable time.