Southern Nevada receives nearly 90 percent of its water supply from the Colorado River, currently facing the worst drought on record. To ensure a more reliable long term water supply for the Las Vegas Valley, the Southern Nevada Water Authority (SNWA or "Authority") is planning to develop water resources in east-central Nevada. The Groundwater Development (GWD) Project is proposed to ultimately consist of a pipeline and power conveyance system and well fields. The main pipeline system, made up of welded steel pipe ranging in size from 66-inches to 96-inches in diameter, will convey groundwater from well fields to be developed in Lincoln and White Pines Counties, Nevada, over 200 miles into Clark County, Nevada. SNWA enlisted the preliminary design services of HDR Engineering to perform system hydraulic analysis and facility definition of the main pipeline. The preliminary design effort included evaluation of various options for pipe procurement. Any procurement option considered would likely result in the pipe being stored for extended periods of time. The duration and harsh climate where the pipe would be stored caused concern that that the integrity of a mortar lining could be compromised. In addition, SNWA experience caused concern that, because of the water chemistry, leaching of alkalinity from the mortar lining could necessitate extensive flushing of the line. Lastly, due to the magnitude of the project, the use of flexible linings had the potential to reduce the tonnage of steel and thus reduce the overall project cost. These factors contributed to convincing the project team that alternate lining materials should be considered. Investigations showed that flexible linings, specifically polyurethane linings, were gaining more acceptance as an alternative to cement mortar linings. However, experience of flexible linings in water pipelines is limited. Epoxy systems were added to the evaluation after considering that recent developments in the formulation of epoxy systems have resulted in quicker set times. Epoxies, as a family of products, have been available longer than polyurethane systems.
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