Chimney Hollow Reservoir

Technical Description:

• CON/SPAN^® O-Series^® Bridge System
• Span: 72'
• Rise: 15'-8"
• Length: 39’

Upon completion, the Chimney Hollow Reservoir will be the largest reservoir built in the last 25 years in the United States. It is located along the front range of Colorado near Loveland and required coordination between nine municipalities, two water districts and a power provider to build the $500 million project. The new reservoir is located just west of Carter Lake in southern Larimer County and will store 90,000 acre-feet of water. The project will provide a firm yield of 30,000 acre-feet annually, which will meet a portion of the future demands of the water users along the front range.

As part of the project, a structure was needed to carry a new recreational road to the reservoir while also providing cover for two 72” penstocks which carry water to Colorado's front range from the other side of the Continental Divide near Granby, Colorado. The structure needed to provide a minimum clearance box for the two penstocks as well as maintenance roads along both sides. 

After researching options, Stantec, the project's engineer, decided that a 72' x 15'-8" CON/SPAN® O-Series® Bridge System, 39' in length, was the best solution for its ability to meet the clearance box requirements of the penstocks and the maintenance roads. It also provided Northern Water, the project's owner, with a buried bridge structure that will require no long term maintenance. The end treatment of the structure was a RECO panel wall with concrete collars to provide a transition between the structure and the wall. 

There were many challenging aspects of this project from design constraints, coordination with multiple entities and site access. The new road had to be built along the side of the mountain with grades at more than 30% and building over two active 72" high pressure penstocks which provide water to many customers in Northern Colorado. 

"Project coordination between Contech Engineered Solutions, Northern Water, Stantec, U.S. Bureau of Reclamation and our construction project team helped make this a successful aspect of the large reservoir project," stated Shawn Perrin, Project Manager of Barnard Construction Company, Inc.

In the end, the CON/SPAN was a great solution for the site, and Northern Water and Stantec were pleased with the outcome.

Technical Description:

• CON/SPAN^® O-Series^® Bridge System
• Span: 72'
• Rise: 15'-8"
• Length: 39’