EFFECTS OF RIVER STAGE AND WASTE-WATER DISCHARGES ON THE UNCONFINED AQUIFER, HANFORD, WASHINGTON

This study examined the effects of river stage and waste water discharge on the unconfined aquifer near the N nuclear reactor on the U.S. Department of Energy-operated Hanford site in Washington State. River levels were statistically correlated with water-level data from 12 wells During the course of this study, water table elevations declined in the study area primarily as a result of a significant decrease in discharge to waste water disposal facilities. A minor contributing factor was the regional decline of the water table caused by decreasing waste water discharges upgradient of the study area. High-frequency river-level fluctuations (e.g., short-term daily fluctuations) had good correlation with water-level variations in a well approximately 750 feet inland. Low-frequency river-level fluctuations (e.g., long-term seasonal fluctuations) had good correlation with water-level variations in a well approximately 1000 feet from the river shore. Time lags and attenuation generally increased with distance from the river as expected, with the exception of two northern wells. These two wells were relatively more responsive to river-level fluctuations at a greater distance inland from the river. This suggests that hydraulic properties (e.g., hydraulic conductivity) are a control on the aquifer reponses. During peak river stage in June, the river level rose above water table elevations in several wells implying a temporary reversal in ground water flow direction near the river.