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I Geological rechnks Inc. Page 5 Groundwater Monitoring Report Project No. 750.2 / April 10,2003 i. • The remaining wells were found to be free of contaminants, which is consistent .with I other events. L • The VETS had removed approximately 700 gallons of gasoline from the subsurface, Table 5 of Appendix A. - When the VETS was shut down on January 31, 2003, extraction rates were down to 3.6 lbs/day, Table 6 of Appendix A. L •'' Vertical groundwater gradient was calculated for the event of December 30, 2002, and f was found to be insignificant. The magnitude of the vertical gradient has been getting I progressively smaller during the last several monitoring events. This may be a result of influence from the vacuum of the vapor extraction system. r • Oxidation-Reduction Potential measurements (Table 4) are positive for all the wells. y. This suggests that the volume of contaminants leaching into groundwater has been stopped and that biodegradation of the contaminants is at a rate sufficient to mitigate the residual BTEX/TPH-G plume in the area around the source without depleting the oxygen. Recommendations: • Continue Quarterly groundwater monitoring at the site. • GTI prepared a work plan to install two soil borings in the area of the foriner tank pits. We are in the process of obtaining bids for this work. It will be performed as soon as possible. This work will indicate how much contamination is still present and at what I horizons. • Bids are being requested from suppliers of Internal Combustion Engines for use with the VETS. The IC that was at the site was not operating properly and controlling emissions. 3.0 LIMITATIONS LThis report was prepared in accordance with the generally accepted standard of care and practice in effect at the time Services were rendered. It should be recognized that definition and evaluation of environmental conditions is an inexact science and that the state or L practice of environmental geology/hydrology is changing and evolving and that standards existing at the present time may change as knowledge increases and the state of the practice r continues to improve. Further, that differing subsurface soil characteristics can be 6a experienced within a small distance and therefore cannot be known in an absolute sense. All conclusions and recommendations are based on the available data and information. L The .tasks proposed and completed during this project were reviewed and approved by the local regulatory agency for compliance-with the law. No warranty, expressed or implied, is made. C