The project site is located in the Lockport Formation in western New York.  It is hydraulically bound by the Upper Niagara River and the New York Power Authority water conduits, cut 100 feet into the bedrock.  Groundwater was being pumped at approximately 1,000 gallons per minute to intercept a plume of chlorinated solvents.  After several years of monitoring and adjusting pumping rates, hydraulic containment of the plume could not be fully demonstarted based on interpretation of a conventional round of water level measurements.  Two problems existed in the interpretation of hydraulic containment.  First, water levels in the aquifer fluctuated up to three feet over the course of one day in response to water diversions from the Niagara River for hydroelectric power generation.  The result of this fluctuation is a significant uncertainty in the potentiometric surface maps interpretated from a conventional round of hand water level measurements.  Second was the approach to interpreting the data; providing a totally unbiased interpretation of the data, versus interpreting the data beginning with expected conditions based on a conceptual or quantitative model of the aquifer system.  The result of additional data collection, modeling to characterize expectations, and interpretation of the data, was an effective demonstration that the plume was contained at a pumping rate less than 300 gallons per minute.