Preliminary analysis of the shallow ground-water system in the vicinity of the Grand Calumet River/Indiana Harbor Canal, northwestern Indiana

Abstract

The shallow groundwater system in the vicinity of the Grand Calumet River-Indiana Harbor Canal, Indiana was analyzed from June 1985 to May 1986. This analysis was done to obtain detailed information about the physical characteristics of the Calumet aquifer and the shallow groundwater flow system. 36 shallow wells were installed and sediment samples were collected at 26 sites. Water level measurements were made in 45 wells. Data indicate that the aquifer consists of fine-grained to medium-grained sand, locally overlain by slag fill. Aquifer thickness is 0 to 65 ft. This aquifer is underlain by about 100 ft of glacial till and lacustrine clay that overlies carbonate bedrock of Silurian age. Broad, low-relief water table mounds occur between the major surface water drains. The crests of these mounds form major east-west-trending water table divides. Northwest of the Indiana Harbor Canal (IHC), a narrow water table ridge parallels the Lake Michigan shoreline and connects to a somewhat circular, low mound northwest of the IHC. Shallow groundwater generally flows from these water table mounds to the major streams or to Lake Michigan. Groundwater also flows to small ditches, wetlands, and sewer lines. Stream/aquifer relations along the Grand Calumet River/IHC were quite complex. Digital model simulations of a conceptual north-south section near the middle of the study area indicate that discharge of groundwater to small ditches and leaky sewer lines has lowered the water table by several ft from predevelopment levels. Simulations also indicate that downward leakage to the bedrock may have contributed to the decline in the water table.