Tunnel and Reservoir Plan
Adopted in 1972 by the Metropolitan Water Reclamation District of Greater Chicago, the Tunnel and Reservoir Plan (TARP) was established to protect Lake Michigan's drinking water, improve the quality of area waterways and to provide an outlet for area floodwaters to reduced street and basement sewage backup.
Delivering the Final Component
Walsh was hired by the Metropolitan Water Reclamation District to construct the final portion of the concrete lined Deep Tunnel, that connects the existing Calumet Indiana Avenue Leg TARP Tunnel to the Thornton Composite Reservoir.
One of the Largest Civil Engineering Projects
The Deep Tunnel is part of a 100+ mile system of 30-foot diameter tunnels that are 300 feet deep. The tunnel gathers storm and waste water from the South Side of Chicago and delivers it to the 83 acre Thornton Composite Reservoir which has a capacity of holding 7.9 billion gallons of storm and waste water.
Walsh crews installed these 18-ft x 29-ft x 4-ft wheel gates 300 feet below the ground to regulate the flow of storm and waste water. The video below captures the underground environment of the site.
Withstanding the Force of Water
A concrete apron constructed in front of the tunnel is designed to withstand the force of the water coming out of the tunnel, which can be at velocities of up to 30 feet per second, and prevents erosion of the stone reservoir floor.
These aerators were installed in the reservoir and will float up and down with the water elevation, keeping the surface layer of water from going septic and causing odors.
"Chicago's grand canyon"
With nearly 40 years of construction, the Thornton Composite Reservoir put an end to the once-frequent practice of dumping the region's waste into Lake Michigan, the source of drinking water for more than seven million people in the city and suburbs.