Contractors in a small Wyoming town surmounted rocky terrain and a short construction season to install a new ductile iron pipe water main.
The town of Pinedale, midway between Rock Springs and Jackson Hole, Wyo., was carved from ranch properties settled in the late 1800s. The Pinedale economy still depends somewhat on ranching, although mineral extraction, tourism and government offices provide the bulk of the jobs in the area. About 1,300 people live within the town limits.
In the early 1970s, a 14-inch asbestos cement line was installed 70 feet below the surface of Fremont Lake, bringing water directly from the lake into the towns distribution system. The town soon outgrew the line, however. It did not provide enough volume to support growth and fire flow, nor to meet the requirements of the Safe Drinking Water Act.
With financial assistance from the Wyoming Water Development Commission, the town of Pinedale set out to build a new ductile iron water line to service the regional water supply. Rio Verde Engineering (RVE) and TST Inc. were selected as the design engineers for the project.
The project included areas of wet unstable soil, very rocky terrain, deeply buried pipe and zigzag paths for the new pipe to follow. The project was sent out for bids on April 15th, 1998. Ten bids were received and SCI Inc. was selected.
The contractor would not be able to start the ductile iron portion of the project until early June 1998. The contractor had to finish laying pipe by the end of the summer or the project could be hampered by bad weather.
Ductile iron pipe from U.S. Pipe and Foundry was chosen for the job.
The contractor selected the companys TR-FLEX? Restrained Joint Ductile Iron pipe for the areas of very wet soil. The restraining system was needed to ensure that the joints would not pull apart in the unstable soils. The pipe also provided the engineer with a 350 psi rating in the 24- inch size, versus other restraining devices which offered a 250 psi rating.
Other areas of the pipeline were in very rocky terrain and deeply buried, up to 20 feet. In these instances, ductile iron was specified as the natural choice per ANSI/AWWA C150/A21.50 Thickness Design of Ductile-Iron Pipe. The pipe material also was chosen because it is resistant to internal deflection and does not need stulling, or internal supports.
The layout of the line included several areas where it was necessary to deflect the joints to traverse radiuses and up-and-down terrain. The 24 through 36-inch U.S. Pipe Tyton Joint? Pipe could be deflected a full 19 inches on each 18-foot length when required.
Although several snowstorms hit the area in June, the ductile iron portion of the project was completed in the fall of 1998. The bad weather, tough terrain and a short construction season made this a challenging project.
