A GPR Investigation of Buried Infrastructure at the North Unit of Illinois Beach State Park

Abstract

From the 1920s to the mid‐1970s subdivisions were built along the Illinois shore of Lake Michigan for several miles south of the Wisconsin border. Natural erosional forces hastened the destruction of many of these homes. The state responded with the purchase of the “endangered residences” thus creating the North Unit of the Illinois Beach State Park. The houses were removed but, except in the area now occupied by a marina, the sub‐surface infrastructure remained. Debris spread along the beach by ongoing erosion of the old home sites was thought to pose a health threat to the public. Of particular concern was the expected existence of a relict network of water and/or sewer pipes made of asbestos‐containing concrete. To search for the buried utilities in one abandoned subdivision south of the marina we acquired over 3,500 m of GPR profiles. We detected a network of buried steel pipes, a large currently used raw‐water supply pipe, and small clay tiles, but we could find no evidence in the study area that asbestos‐containing water supply or sewer pipe networks were ever installed in this subdivision. Differences in the signatures of steel and other types of pipes were confirmed by direct observations.