Use of Isotopes to Identify Sources of Ground Water, Estimate Ground-Water-Flow Rates, and Assess Aquifer Vulnerability in the Calumet Region of Northwestern Indiana and Northeastern Illinois

摘要

This report describes the results of an investigation designed to characterize ground-water recharge and flow rates and vulnerability of the aquifers to contamination in a heavily industrialized area of northwestern Indiana and northeastern Illinois. Water samples were collected from a well network distributed across northwestern Indiana and northeastern Illinois. Samples were collected from 26 wells during July 1997 and from 21 different wells and Lake Michigan between January 2000 and April 2001. Thirty-six of the sampled wells were screened in unconsolidated deposits and 16 were finished in bedrock. Samples were analyzed for concentrations of tritium and helium and isotopic abundances of oxygen and hydrogen. Absolute and relative ages of ground water, computed from sample results, were used to address project objectives.