Challenge. Design shoreline structures to meet the level of protection specified by the National Economic Development (NED) plan
Solution. Taking advantage of a large bedrock outcropping (Morgan Shoal) that lies just offshore, the City of Chicago and Chicago Department of Transportation considered an alternative shoreline protection scheme—a series of offshore breakwaters/islands to support ecological functions/habitat in their lee—in lieu of the NED plan’s rubblemound revetment along the 45th Street to 51st Street segment of this federal shore protection project. INTERA defined the appropriate wave climate near the project by employing the United States Army Corps of Engineers’ (USACE) Coastal Modeling System wave model (CMS-Wave) to transform waves from the offshore Wave Information Study station to the site and examined breakwater/island configurations and substrate stability in their lees via empirical formulas and desktop assessment tools. During the course of the design process, the public wanted to preserve the shoal and suggested a scaled back shoreline alternative. The reduced conceptual plan consisted of an onshore rubblemound revetment with an amphitheater area (comprising special placement of cut stone) and a small pebble beach, to mimic the existing pebble beach, in front of the amphitheater toe. INTERA developed typical sections of the rubblemound revetment including areas where the shoreline extended into the lake beyond the existing shoreline and the amphitheater area. We also participated in a meeting with the USACE Chicago District to ensure the design met federal and NED standards.