Project: Deep Rock Tunnel Connecton - Indianapolis, IN
Customer: Citizens Energy Group - Indianapolis, IN
Contractor: S-K JV: J.F. Shea Construction - Walnut, CA; Kiewit Corp - Omaha, NE
Finisher: Platt Construction - Milwaukee WI
Project obstacles and solutions: The Deep Rock Tunnel Connector is a sewer overflow project designed to solve the combined sewer overflow (CSO) problem the City of Indianapolis has been mandated to fix by the Environmental Protection Agency (EPA). During a rain event, as little of 1/4 inch of precipitation has caused raw sewage to spill into the streams and rivers running through the city, causing health concerns. The Deep Rock Connector is a network of tunnels bored through bedrock 250 feet below the surface. During a rain event, CSO will be collected in the tunnel and moved to the city's wastewater treatment plant. When finished, the tunnel will stretch 28 miles and have a capacity of 54 million gallons.

The contract on this project was awarded to a joint venture of J.F. Shea Construction and Kiewit Corporation (S-K JV). The first phase consists of a nearly 10 mile stretch of tunnel running from near Lucas Oil Stadium in the downtown area to the Southport Wastewater Treatment plant on the south side of Indianapolis. A boring machine was used to cut a 20 foot 2 inch tunnel which was then covered with 13 inches of concrete, making the tunnel 18 feet in diameter. The concrete forms spanned up to 250 feet and required 600 yards of concrete per pour. The forms were broken down and moved every day to set up for the next pour on down the line.

Delivering concrete 250 feet below ground was fairly easy, given that there were 11 shafts along the tunnel route. It took very little pumping to get the concrete down these shafts. However, concrete had to travel by pipeline to the forms, which could be as far as 4,200 feet away from the shaft opening. IMI QC/QA designed a 5,000 psi mix that had a 9 inch slump so it would flow easily through the pipeline. Another key to the success of the tunnel was the ability to keep the wastewater from seeping through the walls and contaminating the area around the tunnel. To decrease the permeability of the concrete, it was mixed with a superplasticizer. This decreased the water-to-cement ratio to produce a denser mix.

The first phase of the Deep Rock Tunnel is scheduled to be completed by the Fall of 2016. IMI is supplying 130,000 yards of concrete for this project.

For more information on pouring concrete to hold water without seepage, contact the sales representative nearest your location. Click here.