# Contaminant Arrival Times at Wells G and H

Another major difference in the testimony of the three expert hydrogeologists in the trial was the arrival times of TCE and PCE in wells G and H. The plaintiffs' expert stated that these contaminants would reach wells G and H in less than 3 years. The Beatrice expert claimed that the contaminants would never flow to the municipal wells because the Aberjona was a groundwater divide preventing flow under the river to the wells. The W.R. Grace expert stated that the contaminants could not have reached wells G and H by May of 1979.

Each expert had at his disposal the same water-level, streamflow, and permeability data upon which to make these calculations. Each expert, however, used a different approach to making the calculations. One expert relied on the results of a 1-dimensional model that assumed steady-state conditions within the flow system and spatially uniform values of permeability, porosity, and hydraulic gradient. One expert used the water-level and streamflow data to construct potentiometric surface maps and a potentiometric profile to show that groundwater could not flow under the Aberjona River. The third expert incorporated all the site-specific water-level, streamflow, and permeability data into a 3-dimensional computer model that accounted for the transient character of the flow system due to temporal variations in recharge from precipitation, and changes in the pumping rates of wells G and H and their periodic use (Bair, 2001 (Acrobat (PDF) 4MB Jun18 09)). Excerpts from the trial testimony of these three experts can be found in Resource Collections under the **Trial Testimony** section.

**Learning Modules 3, 5, and 8**involve constructing the maps and performing the calculations to make (simplistic) estimates of contaminant arrival times in wells G and H.