The Denver Water Department joined forces with Northwest Pipe and Madison Coatings International to construct a pipeline to bypass Marston Reservoir during periods when the lake was suffering from taste and odor problems due to seasonal turnover.
For construction of the pipe, the Denver Water Board selected Northwest Pipe, a manufacturer of large diameter steel pipe used for water transmission lines. The company supplied 8,000 feet of 108-inch diameter steel pipe for the project.
Northwest Pipe realized that conditions within the pipe would be somewhat harsh, with mud and heavy silt coursing constantly through the pipe. The company chose to line the pipe with Madison's CorroPipe II PW, a two component, quick setting, 100 percent solids polyurethane that meets ANSI/NSF standards for potable water pipelines. The coating is also covered by American Water Works Association Standard ANSI/AWWA C222, Polyurethane Coatings for the Interior and Exterior of Steel Water Pipe and Fittings.
Since the installation of the Marston Reservoir Bypass, the Denver Water Board has inspected the pipeline on three separate occasions. On each occasion, they have been delighted with the performance of the lining.
The most recent inspection took place on Dec. 15, 1999, and brought together engineers and field personnel from the Denver Water Board and Northwest Pipe. Gaining access to the pipeline through a manway at the southeast corner of the reservoir, they walked approximately 1,000 feet to a major dropoff that brings the pipe under the reservoir. No stationing was provided. The pipeline had been de-watered two days before and was coated with a thin film of mud. The bottom of the pipeline also had a few inches of standing water as well as heavier silt. Nevertheless, officials from both organizations were happy to discover that the polyurethane lining remained in excellent condition, and no touchup or repairs were needed to any of the approximately 225,000 square feet of steel surface.
"Visual inspection showed the polyurethane lining to be in extremely good condition," said Neal Kelemen of Northwest Pipe. "The lining still retained a gloss surface when wiped clean. No blisters or obvious defects were observed. Minor field touch-ups to the polyurethane that were made during installation were intact. The field applied joint material also did not show any delaminations; in fact, it was difficult to detect the point of interface between the factory and field applied material."
John Bambie of the Denver Water Board also was present during the inspection and recently commented on the performance of the lining. Noting that the Board has since chosen CorroPipe II PW as an alternate lining for another large project, Bambie said he was "very pleased with the product's performance".
