Using Air Caster Technology to Install Large Diameter Pipe in a Tunnel

The Tarrant Regional Water District (TRWD) with the City of Dallas Water Utilities (DWU), are currently engaged in the planning, design, and implementation of a 350 MGD raw water transmission system, which will run across north central Texas from Lake Palestine to Lake Benbrook, with connections to Cedar Creek Reservoir, Richland Chambers Reservoir, and a Dallas delivery point. Collectively, the system consists of approximately 145 miles of 84-inch to 108-inch pipeline, a 5-mile 120-inch diameter tunnel, six 100-350 MGD pump stations, one 450 MG balancing reservoir, and ancillary facilities. The program developed by TRWD to accomplish these improvements is called the Integrated Pipeline Project (IPL). In one of the pipeline sections, PL 14, Garney Construction needed to install 805 linear feet of 108-inch carrier pipe in a tunnel under Interstate 35E located just south of Waxahachie, Texas. For this segment, Garney proposed an innovative method of installation which included the use of air casters. Air casters are a pneumatic device that forms a lubricating film of air between a load and floor surface similar to that of a hovercraft or air hockey table. Air is squeezed between the floor and a diaphragm, creating a thin film of air allowing the load to float nearly friction-free. Air-casters have traditionally been used in the heavy manufacturing industry to move very large or heavy equipment in controlled factory environments. Air caster technology was first developed in the early 1960s by engineers working at General Motors as an alternative to bridge cranes. This paper will discuss the challenges and successes encountered during construction and show that air casters as a highly innovative method for placing large diameter carrier pipe in tunnels.