“Chimney Hollow dam will be the tallest one constructed in Colorado in the last 50 years,” said Don Mongomery, the principal engineer who will design the reservoir project, drawing on experience from dams around the globe.
“It will be in the order of 360 feet tall,” he said, with a crest estimated at 3,500 feet long.
Final design of Chimney Hollow will pare down the specific height and construction details for the dam, spillway, pipeline and inlets that will allow Northern Water to store as much as 90,000 acre-feet of Windy Gap Firming Project water.
Northern Water, the agency coordinating the project, recently hired the Broomfield-based MWH Global with an $11.9 million contract for engineering and design. Montgomery, who was raised and went to college in Boulder and Larimer counties, is leading that process.
He said he is excited to use the skills he has honed worldwide, working on projects on the Panama Canal and in Peru among other locations, in his home state to build a reservoir that will provide recreation that he, among many others, enjoys with his family.
“To be able to bring that home is pretty amazing,” said Montgomery. “To be able to help my community is pretty exciting. Once they’re done, they become these great resources to the community.”
Chimney Hollow Reservoir is expected to be completed by 2021 to begin storing water for 13 participants including Loveland, Longmont and the Little Thompson Water District. And it will become a new recreation area managed by the Larimer County Department of Natural Resources.
The reservoir and surrounding park will be located west of Loveland near Carter Lake, Flatiron Reservoir and Pinewood Reservoir, which are all managed by Northern Water for water storage and by Larimer County for recreation.
Specific recreation plans are still in the works, but Larimer County Department of Natural Resources officials are looking at a mix of camping, hiking and non-motorized boating, including paddle boats and sail boats. Campsites reachable only by boat also are in the initial plans.
The design of Chimney Hollow should take about two years and will include determining the best type of structure to be built, whether it will have a clay core made from materials on site, a concrete face or an asphalt core, noted Montgomery. This will be determined by drilling, sampling and studying the area.
The process will fine-tune the construction details and the costs as well as the exact height of the dam at Chimney Hollow. It will, however, be around 360 feet tall, which will make it the tallest in Larimer County,.
Construction of Chimney Hollow will be the biggest reservoir project in Larimer County in about six decades.
Northern Water began applying for permits in 2003, and the federal government approved the project in December 2014. Since then, the water district has been working on the rest of its needed permits. All that is left is a federal wetlands permit, which Werner expects to be approved this year.
“This is the very last piece in the puzzle,” said Werner. “At this point, there’s nothing else. No other permits, no other agreements that we have to do. We’ve done it all.”