Unique underground construction work is taking place at Indianapolis International Airport. In late March, Bowen Engineering Corp., Fishers, Ind., used a mechanical tugger to install a 2,000-foot-long, 24-inch-diameter insulated carbon steel pipe through a tunnel constructed under the north runway. The pipe is one of two in the chilled water system for the midfield passenger terminal of the New Indianapolis Airport.
The tugger, powered by an air compressor providing more than 22,000 pounds of force, pulled the large pipe — manufactured by Perma-Pipe Inc. — through the entrance of the 2,016-foot-long, 106-inch-diameter tunnel at about 20 feet per minute. The tugger was attached to the end of the pipe with a steel cable.
"An installation of this magnitude had never been done before," says Pat Johnston, project superintendent for Bowen Engineering — general contractor for the project. "It was very challenging."
Elizabeth Dwyre, P.E., project manager for design engineer PB (Parsons Brinckerhoff), Indianapolis, adds, "This method of installing pipe inside a casing is not an uncommon thing to do, but usually the lengths are much shorter."
The two pipes installed by Bowen will provide chilled water delivery and return from the airport's Central Energy Plant to the midfield terminal. The chilled water system will supply water at 42 degrees Fahrenheit.
Previously crews had installed two 8-inch-diameter, insulated pipes through the tunnel — one for hot water supply and one for hot water return. The high-temperature hot water system is a conduit/carrier pipe system — 8-inch-diameter carbon steel pipe carries the water, surrounded by mineral wool insulation, with an air gap, inside a steel conduit. The steel conduit is encased in fiberglass to protect the piping system from corrosion.
When the hot water pipe is filled with 325-degree Fahrenheit water, the pipe will expand and the length of the pipe will "grow" by about 4 feet within the tunnel. Ball joints at each end of the tunnel will accommodate this movement.
The $1.1-billion New Indianapolis International Airport is the largest development initiative in the city's history. The centerpiece of the project is the four-level, midfield terminal building located between the two existing main runways. The new terminal building will have two concourses with 40 gates and take up 1.2 million square feet. Construction of the new airport is scheduled for completion in late 2008.