10 Billion Gallons More—The Main Tunnel System Linking the TARP Mainstream Tunnel to the McCook Reservoir

摘要

The Metropolitan Water Reclamation District of Greater Chicago’s (MWRDGC) Tunnel andrnReservoir Plan (TARP) and the McCook Reservoir will further reduce flood damages and combined sewerrnoverflows (CSOs) for the city of Chicago and the Cook County, Illinois. The McCook Reservoir will receivernapproximately 10 billion gallons of water via the Main Tunnel System which connects the TARP MainstreamrnTunnel to the McCook Reservoir. The U. S. Army Corps of Engineers (USACE) tasked Black & Veatch torndesign the Main Tunnel System. This paper describes the Main Tunnel System project components and howrnthis final piece fits into the Chicago’s TARP program.rnThe Main Tunnel System design included overall design and constructability considerations for a 27.5-mrn(90-ft diameter and 92-m (300-ft) deep Main Gate and Tunnel Construction access shaft and associated wetwellrnshaft arrangements to house six high-head and large (14.5 ft by 29.5 ft) wheel gates; a 10-m (33-ft) diameterrnand 490-m (1,600-ft) long Main Tunnel in rock including a tunnel bifurcation (with steel and concreternlining) at the Main Gate/Access Shaft; a live tap connection to the existing Mainstream Tunnel; and energyrndissipation and portal structures. Risk management and construction sequencing were included in the effort.rnThe construction of the Main Tunnel System has been divided into the Main Gate/Access Shaft contractrnand the Main Tunnel System contract. Construction of the Main Gate/Access Shaft was completed in Augustrn2011 and Main Tunnel System construction is currently ongoing. Construction progress updates and discussionrnof key construction issues to date are presented in this paper.