Several years ago, Fort Collins Utilities in Colorado had to find a way to rehabilitate two difficult-to-access water supply pipelines.
The 24-inch reinforced concrete Poudre Canyon Waterline brings half the senior Poudre River water rights (10 mgd) to a treatment plant. Built in the 1920s, the raw water pipeline is in excellent structural condition except for one weakness.
If its lead-packed cast iron bell and spigot joints are at all disturbed, they leak. The 19,000-foot pipeline follows a very serpentine horizontal and vertical alignment and is precariously placed on slopes that have experienced movement over the years.
The 27-inch welded steel Foothills Water Transmission Line is the only finished-water feed to a 1.5-million-gallon reservoir that serves the Foothills pressure zone in the northwest portion of the utility’s service area. Built in the mid-1950s, it suffers from corrosion-related leaks. It’s a straight alignment but lies in residential backyards.
Utility managers considered replacing it with a new line on a different alignment, but for reasons including neighborhood impacts, high groundwater, extensive pavement replacement, and total construction cost, the solution would have to involve in-place rehabilitation.
These two critical waterlines represented two drastically different situations. Both were successfully rehabilitated via Swagelining and are now in service, but their construction experiences varied substantially.
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