So, what’s the deal with the Chimnney Howlow Open Space and Reservoir?  Here are the high points-

The Chimney Hollow Project will include a 1,800-acre Open Space and a 760 surface-acre reservoir. It is located just west of Carter Lake off the Rattlesnake climb to Pinewood Reservoir. The wakeless reservoir is currently in the construction phase and should be completed in late summer of 2025. The natural area and reservoir will open to the public as a Larimer County Open Space in 2027. The current plan only calls for 10-12 miles of natural surface trails within the entire 1,800-acre open space (If you don’t think that’s enough, please take a second to fill out this survey in support of more singletrack trails).

Chimney Hollow Reservoir is a water storage reservoir that will provide a reliable water supply for Northern Colorado. The project is a collaboration between 12 water providers in the area and is part of a long-term plan to support the region’s growing communities.


  • Management planning | 2024
  • Reservoir construction complete | 2025
  • Construct trails/trailhead | 2025-2026
  • Filling the reservoir | 2025-2027
  • Public opening | 2027-2028

Recreational opportunities will include:
It is currently anticipated that there will be user fees charged to access Chimney Hollow Open Space.

  • Wakeless boating
  • Fishing
  • Hiking
  • Mountain biking
  • Horseback riding
  • A soft surface trail will connect to Carter Lake.

Not allowed:
The following activities and facilities will not be allowed

  • Wakes
  • Camping
  • A marina,
  • Night use
  • Trails on the east side of the reservoir including a trail going all the way around the reservoir

For Comparison:

Open Space

  • Carter Lake Open Space-1000 acres
  • Horsetooth Mountain Open Space- 2,711 acres
  • Chimney Hollow Open Space-1,847 acres

Miles of Trails

  • Carter Lake Open Space-
  • Horsetooth Mountain Open Space- 29 miles
  • Chimney Hollow Open Space- 10-12 miles natural surface trails miles proposed

Reservoir Information

  • Carter Lake- capacity of 112,230 acre-feet, 1,110 surface acres, 12 miles of shoreline and a maximum depth of 180 feet. Miles long- 3. Miles Wide- 1.
  • Horsetooth Reservoir- a capacity of 156,735 acre-feet, 1,900 surface acres, 25 miles of shoreline and a maximum depth of 188 feet. Miles long- 7. Miles Wide- 1/2
  • Chimney Hollow Reservoir- a capacity of 90,000 acre-feet, 760 surface acres, and a maximum depth of 325 feet. Miles of shoreline, width and length TBA

More Information:

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