Is It a Pipe or a Bridge? Large Diameter Aerial Pipe Design Considerations

Over the past several years, Denver Water has been working to improve the reliability of its northern supply system which makes up large portion of its water portfolio. The Moffat collection system, originally constructed in the 1930s, is the beginning of this system and includes a series of canals, tunnels, and pipelines to collect and convey snowmelt runoff from the Colorado mountains to the Denver area. A critical component of this collection system is a 72-in. diameter aerial pipeline known as the Siphon 1 Fraser River Crossing. The aerial crossing and its approach is located on steep slopes at the base of the Winter Park ski area adjacent to a railroad track and tunnel, and crosses two primary access roads, numerous utilities, and a gold medal trout habitat. Based on assessments of its age and condition, Denver Water determined that this aerial pipeline needed to be replaced for continued, long-term reliability. Due to the site location, conditions and aerial installation, as well as the numerous stakeholders and short construction window, the project was not a straightforward pipeline project. This paper presents the technical and coordination challenges related to the successful design and construction of this critical, high-profile aerial pipeline replacement.