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One hundred years ago, the City of Ogden, Utah, nestled against the rugged Wasatch Mountains, had a population of approximately 25,000. The growing City was thirsty and the nearest large water source was found in the narrow, winding Ogden Canyon. City planners determined that a five mile, 24-inch steel line manufactured on the East Coast would help meet water demand. The line was installed in an era when bedding, minimum bury depth, and environmental concerns were not monitored as carefully as they are today. The original line was installed for approximately $110,000 (including pipe), or less than $5 per foot.
Today, Ogden has a population approaching 100,000 and is a major hub for outdoor recreation equipment companies, along with many other manufacturing entities. Above Ogden Canyon is Snowbasin ski resort, which was one of the host locations for ski events during the 2002 Olympics. Water demand increased dramatically over the last 100 years and the old line began to show its age, ultimately requiring replacement.
Due to the steep and narrow topography of the canyon - which also serves as a major artery for area ski resorts - special construction circumstances were required. Water demand is lowest in the winter and could be satisfied using an adjacent 36-inch line also located in the canyon. Winter construction was also necessary because increased water demand in the summer months required the new 24-inch line to be in operation. At the same time, the heavy winter ski traffic could not be affected and interfere with the important tourist season. The complexity of the project required the City, the design engineer, and the contractor to work closely together. Ultimately, the City and the engineer elected to execute a "Design-Build" contract which would ensure the highest level of teamwork. Whitaker Construction, with a long and successful history in the area, was selected to be the general contractor.
Initially, pipe bursting was chosen as the installation method for the 24-inch Fusible PVC® pipe replacement line. The existing steel pipe burst easily in trials (see photo), but the rugged canyon hampered full expansion. Car sized boulders, vertical rock faces extending into the trench, narrow allowable trenches, and shallow bury depths made it impossible to get the oversized (30-inch) pipe burst expander through the old steel line. The team finally decided that conventional direct-bury at night and in the dead of winter was the only practical solution.
The winding, sloped canyon necessitated that the line be restrained which meant that bell-and-spigot PVC with mega-lugs, HDPE, Fusible PVC® pipe, steel, and restrained ductile iron (DI) were the available piping alternatives. Due to corrosion issues, metal pipes were eliminated from consideration. HDPE was considered, but 30-inch DIPS DR7 was required to match the hydraulic capacity and pressure characteristics of the competitive 24-inch DR18 PVC. The additional outer diameter for HDPE proved impractical and uneconomical given the tight confines of the canyon. Fusible C-905® PVC pipe was selected for the higher pressure, lower-canyon section of the line. Installation began in November of 2012, with the lower section passing pressure testing and back in service by February 2013. The entire line is expected to be back in service by summer. Branson Yantes, Construction Manager for Whitaker Construction, which has completed a half dozen Fusible PVC® pipeline projects, said: "There have been numerous obstacles to overcome on this project, from the abnormally cold temperatures to the unforgiving terrain; then add the factor of performing this work in the absence of light. We were able to adapt and install the waterline via open-cut and still facilitate the outdoor activities for which Ogden is known. Due to the workability and restrained properties of the Fusible PVC® pipe, we were able to eliminate obtrusive fittings and increase production by at least 10 percent."
Horrocks Engineers has designed multiple unique Fusible PVC® pipeline projects in the area, and Design Engineer Jacob O' Bryant commented, "The contractor was able to maintain the critical schedule and stage the necessary materials based upon the design plans and technical specifications prepared by Horrocks Engineers."
This was the City's first opportunity to use Fusible PVC® pipe, and Kenton Moffett, the Water Utility Manager, provided the following insight about the challenging project: "The idea of having no joints is appealing. This is especially true in the rugged terrain of the lower Ogden Canyon. The protection against seismic movement also makes Fusible PVC® pipe appealing. Our hope is that the most important water line in our city will be functioning for at least another 100 years."
|Pipeline Details and Project Summary|
|Project:||Ogden Canyon 24-inch Water Line Replacement Project|
|Owner:||City of Ogden|
|General Contractor:||Whitaker Construction - Brigham City, UT|
|Engineer:||Horrocks Engineers - Pleasant Grove, UT|
|Direct Bury:||6,525 LF 24-inch DR18 Fusible C-905®|