A Water Transmission Pipeline across the Longest Bridge in Arkansas, Spanning the Arkansas River

The City of Scranton, Arkansas, was in immediate need of a new water source. The existing supplier was unable to convey enough water to meet demand. Rather than develop a new water source and build treatment facilities, the city opted to buy water wholesale from another utility, the Clarksville Light and Water Company (CL&W). In order to convey the water from CL&W, new transmission facilities were required including attaching 8,600 linear feet of ductile iron pipe to the longest bridge in Arkansas spanning the Arkansas River. The project team included the Engineer, McGoodwin, Williams, and Yates, and Contractor, JL-Bryson, Inc., with support from manufacturers, EBAA Iron and US Pipe. Attachment of the waterline to an existing bridge presented design challenges different from buried waterline construction. The owner of the bridge, the Arkansas State Highway and Transportation Department (AHTD), would not allow the bridge to be used for thrust restraint of the pipeline. The AHTD further required that the pipeline could not restrict longitudinal movement of the bridge girders. The design also needed to accommodate changes in length due to thermal expansion and contraction of the waterline and the bridge structure. Over the entire length of the bridge crossing, approximately 4 feet of expansion and contraction was expected from the anticipated range of temperatures. Additionally, restrained joint pipe was selected, and the "slack" or available movement in the pipe joints between fully homed and engagement of joint restraint needed to be removed to prevent deflection or snaking of the waterline. This paper discusses methods used to prevent snaking of the exposed waterline, prevent transfer of thrust forces to the bridge, and the use of force balanced expansion joints to accommodate thermal expansion and contraction.