Chicago Finishes Deep TunnelAfter 30 years and more than USD3 billion, the 176 km of tunnels were completed recently when the 12.9 km Little Calumet leg near Calumet City, Lansing and South Holland opened on 12th May, 2006 in Chicago. The opening puts the final touch to the first phase of what is formally called the Tunnel and Reservoir Plan (TARP), or Deep Tunnel.The TARP system captures the combined sewer overflow and sends it to a reservoir, where it is pumped to a treatment plant, treated and released after storms. A series of pipes snake underground from Wilmette to the Loop, over to LaGrange and up to Chicago O'Hare Airport, as well as a system in southern Cook County. The goal is to prevent sewage and stormwater from spilling into rivers and canals. In 1972, engineers from the Metropolitan Water Reclamation District of Greater Chicago, the City of Chicago, Cook County and state agencies developed the TARP. The United States Environmental Protection Agency provided nearly 75% of the funding for the project, which broke ground in 1976.Nearly a decade later, in 1985, the first 50 kilometres of tunnel, from Wilmette to south suburban Hodgkins, was completed and put into service. Other tunnel systems were constructed underneath the Des Plaines River, from O'Hare Airport south to LaGrange, and under the Cal-Sag Channel and Little Calumet River.Now that the tunnels are finished, the second phase of the project - the reservoir portion - will take centre stage. Three huge reservoirs - one at O'Hare, another in McCook and one in Thornton - will be able to hold nearly 60 billion litres of wastewater, and are expected to prevent flooding and pollution. The first reservoir was completed at O'Hare in 1998. The McCook reservoir will hopefully be completed by 2015. The Thornton reservoir will likely be completed by 2023. That makes the TARP a 50-year project, from inception to completion. The Little Calumet leg was bored by contractor Affholder with a Robbins TBM MB 1410-251-2. It set three world records there in its size class of 5.01-6 m-diameter TBMs, with a best day of 99.1 m, a best week of 562.2 m and a best month of 2,163 m. Robbins supplied the TBM, a refurbished used machine, upgraded to latest specifications with variable frequency cutterhead drive and 48.3 cm cutters. It also supplied the back-up, horizontal tunnel conveyor, vertical shaft conveyor and overland conveyor. The 250-tonne TBM nicknamed 'Mikaela' cut a 5.56 m-wide tunnel as it moved through limestone 46 to 91 metres below ground. Click us/14. Visit www.robbinstbm.comA recent study shows there were 10 species of fish in the Chicago and Calumet river systems in 1974. By the time the first Deep Tunnel section was opened in 1985, that number had already grown to more than 40. By 2005, there were nearly 70 species of fish in the two rivers' systems.Besides its significant role in reducing Chicago-area flooding, the TARP project is one of the largest public works projects in US history. In 1986, it received the Outstanding Civil Achievement Award from the American Society of Civil Engineers. Visit www.mwrd.org or www.mwrdgc.dst.il.us 28/06.