Are tunnels a proven technology for wastewater and CSO conveyance and storage?
Yes, large underground tunnels are a common and accepted technology for conveyance and storage of wastewater and combined sewer overflows. A recent inventory of tunnel projects in other cities identified more than 47 tunnel projects in the United States and overseas. These projects ranged from 7 feet to 33 feet in diameter and from 2 miles to 33 miles in length. The Chicago Tunnel and Reservoir Plan (TARP) is one of the most successful and large-scale applications of tunnels. This project has 109 miles of 33 feet diameter that have performed excellently in more than two decades of operation. Other large tunnel projects in operation in the U.S. include Austin, Boston, Cleveland, Houston, Detroit, Los Angeles, New York, Minneapolis, and San Francisco.
