The Chicago Area Deep Tunnel Project: A Use of the Underground Storage Resource

The Greater Chicago area is plagued with recurring water pollution and flood problems stemming from three sources-industry, wastewater treatment plant effluent, and combined storm and sanitary sewer overflows. A solution to all three sources is the Deep Tunnel Project. It will capture stormwater overflows from combined sewers, dropping them through vertical shafts to a tunnel network. The polluted water will be conveyed for temporary storage in a large mined underground reservoir 800 ft (242 m) below the surface. Preliminary design studies including project features, feasibility, costs, performance, and benefits, as well as operation, are discussed. Tunneling methods are included.