Combined Active Capping/Wetland Demonstration in the Chicago River

ABSTRACT: Our group is collaborating with the Metropolitan Water Reclamation Dis-trict of Greater Chicago, the Wetlands Initiative, and Patrick Engineering to install field scale active capping demonstration projects in Collateral Channel and “Bubbly Creek ” in the Chicago River. The Collateral Channel site is a channel terminating at a combined sewage outfall dating to the late 1800s. Bubbly Creek is a 6800 ft (2000 m) creek termi-nating at the Racine Avenue pumping station (RAPS), the largest sewage pumping station in the world. During large storm events, the RAPS can discharge up to 6000 ft3/s (175 m3/s) into the creek. These high flow rates result in large shear flows on the sediment. The capping will be carried out in conjunction with overlaying wetlands to remove nutrients from the river and pollutants from combined sewage outflows. Active cap amendments will be evaluated in the one acre Collateral Channel site and the four acre Bubbly Creek site. Amendments will include metal sequestration agents and hydrophobic organic contaminant sequestration agents, as well as nitrate salts (to stimu-late anaerobic oxidation) and a sand reference cap. Extensive sampling of Collateral Channel and the Turning Basin of Bubbly Creek was performed to get a backgroun