A Civil Action - The Woburn Toxic Trial > Learning Modules > Induced Infiltration

Module 7: Induced River Infiltration to Wells G & H

Module Goal:

Student Assignment

Overview

The plaintiffs expert hydrogeologist, Dr. George Pinder, created a controversy in the courtroom when he described how the Aberjona River interacted with wells G and H when the wells were pumped. The controversy concerned his opinion of the amount of surface water that infiltrated from the Aberjona River into the aquifer that was captured by wells G and H. Excerpts of the testimony (see copies) document the importance of assessing this aspect of the hydrogeologic system at wells G and H. The ambiguity of Dr. Pinder's testimony was identified by several jurors as their reason for skepticism of being able to conclusively identify the source and contribution of contaminants to the wells.

Understanding the effect of induced infiltration to aquifers

Understanding how induced infiltration of surface water has to be considered as part of the value waiting either geologic budgets is an important aspect of understanding the sustainability of the resource. This topic is addressed in the USGS Circular 1186. Pages 30 through 35 illustrate how groundwater flow can converge toward a stream (gaining stream – the stream gains flow from groundwater discharge into it) and how groundwater flow can diverge away from a streambed (losing stream – the stream loses water by infiltration to the groundwater system) and contribute water to an aquifer. Knowing the locations of gaining and losing stream reaches and quantifying the amounts of iinfiltration and discharge are important to computing hydrologic budgets and determining the sustainability of the resource, as described in the section on groundwater budgets.

Profile of the Aberjona River Valley

The geologic data presented in Module 3, which is taken from court records can be used to construct a geologic cross section of the Aberjona River Valley. One of the interpretations based on creating a cross section is consideration of the effects of interbedded peat and fine sands that underlie the river valley. In preparing for a mock trial, a critical question that needs to be considered is the effect of these materials on induced infiltration from the Aberjona River to wells G and H.

More Information

Data Sources

USGS Aberjona River Hydrology website | USGS Real-time water data (more info)

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