Chimney Hollow Reservoir Project

A New and Much Needed Reservoir

As Northeastern Colorado’s population continues to grow, communities across the region need collaborative solutions to meet future water demands while protecting the environment, supporting local agriculture and preserving quality of life. The Chimney Hollow Reservoir is designed to help achieve these goals. Developed in partnership with 12 Northeastern Colorado water providers, the project is designed to improve the reliability of, or make firm, water supplies from the Windy Gap Project. Located just west of Carter Lake in Larimer County, the reservoir will offer dedicated storage to ensure a reliable 30,000 acre-feet of water annually—securing resources for future generations. 

Connect on Facebook
Connect on X
Email the Chimney Hollow Team
A small amount of water in Chimney Hollow Reservoir behind the dam.

Participants

  1. Planning for a Growing Region

    The Chimney Hollow Reservoir Project will benefit nine cities, two water districts and a power provider. By 2050, the combined population served by these providers is expected to grow to approximately 825,000 people—more than double its 2005 population. Water demand projections show a shortage in supply of 64,000 acre-feet in 2030 and 110,000 acre-feet by 2050. To help meet these future needs, participants pursued a comprehensive approach that includes conservation, reuse and additional storage, with Chimney Hollow Reservoir serving as a critical component. 

    • Broomfield – 26,464 acre-feet
    • Platte River Power Authority – 16,000 acre-feet
    • Loveland – 10,000 acre-feet
    • Greeley – 9,189 acre-feet
    • Longmont – 7,500 acre-feet
    • Erie – 6,000 acre-feet
    • Little Thompson Water District – 4,850 acre-feet
    • Superior – 4,726 acre-feet
    • Louisville – 2,835 acre-feet
    • Fort Lupton – 1,190 acre-feet
    • Lafayette – 900 acre-feet
    • Central Weld County Water District – 346 acre-feet

Project Infrastructure and Resource Protection

Brown trout swimming in water.
Onsite quarry at Chimney Hollow with trucks and equipment on various levels.

Construction

Construction of the 90,000-acre-foot-reservoir began in August 2021. Key components included a 350-foot-tall main dam, 40-foot-tall saddle dam, water conveyance system, interconnections to the existing Colorado-Big Thompson (C-BT) Project infrastructure, an on-site quarry and new access roads into the site for the future Larimer County Open Space. Throughout the course of the four-year construction period, the project saw numerous milestones.

14,500,000 cubic yards

quarry material

512 lifts

asphalt

80 cubic yards

concrete produced at the batch plant

500 employees

during peak production
 
Person in kayak padding with sun setting in background.

Recreational Opportunities

Recreation is an important component of the Chimney Hollow Reservoir Project, providing new outdoor opportunities while enhancing quality of life for residents and visitors. Through a partnership with Larimer County, the project will create a new recreation destination with activities to include wakeless boating, fishing, hiking and horseback riding, offering a variety of ways for people to enjoy Northern Colorado's natural landscapes. Recreational amenities will be designed to balance public access with the protection of natural resources. The site will not include camping, marina facilities or nighttime use. Hiking trails will connect with existing trails near Carter Lake, further expanding outdoor recreation opportunities in the area. 

Larimer County Chimney Hollow Open Space