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Geological Technics Inc. Page 6 Groundwater Monitoring Report Project No.425.2 ` November 17,2003 ,., 3. Vertical groundwater gradients have been found to be flowing upward, during winter and early spring, and downward during late spring and summer. Upward vertical gradients dominate over downward gradients by a 4:1 ratio. +.• 4. The dominance of upward vertical flow of groundwater may be the primary reason the contaminants has not impacted the drinking water aquifer. 5. The shallow water table groundwater plume is laterally defined except to the west. M Increases in TPH-G concentration in the western monitoring wells indicate that the plume may be spreading laterally toward the west. 6. Petroleum hydrocarbon concentrations in the groundwater at the site fluctuate with each monitoring event. The residual contamination in soil, up gradient of MW-2, remains a significant source of impact to the groundwater plume. 7. The deeper groundwater plume is defined vertically since MW-102 and MW-202 remain non-detect for contaminants, indicating that the contamination is not moving deeper into the aquifer. $. The three domestic wells sampled for the event remain non-detect, indicating that the drinking water aquifer has not been impacted. Recommendations The following recommendations are made: 1. Incorporate the monitoring or the four new groundwater-monitoring wells into the y. current quarterly groundwater-monitoring schedule. 2. Prepare and submit a monitoring well installation report for work performed at the site in October of 2003. w. 3. Prepare and submit a feasibility study reviewing the best remediation alternatives available to remediate the George's Service Site. 4. After review of the feasibility study by SJC PHS/EHD and CRWQCB-CVR prepare a corrective action plan to implement the selected remediation alternative. `' 4.0 LIMITATIONS A.0 This 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 i, or 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 continues to improve. Further, that differing subsurface soil characteristics �... can be 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.