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Heil Valley Ranch Cal-Wood Fire Recovery
Cal-Wood Fire at Heil Valley Ranch

Heil Valley Ranch Cal-Wood Fire Recovery

Recovery work is underway at Heil Valley Ranch from the devastating Cal-Wood Fire. Recovery operations include hazard tree removal, aerial mulching, erosion mitigation, and replacing damaged visitor amenities and park infrastructure including bridges, fencing, parking stops, and signs.

Cal-Wood Fire

The Cal-Wood Fire started on Oct. 17 and raced downwind and downslope through Heil Valley Ranch. It consumed 5,000 acres in about five hours. In the end, it covered over 10,000 acres with more than half of that on Boulder County owned property (4,400 acres) and conservation easements (1,400 acres).

Portions of Heil Valley Ranch are open to on-trail use only, including the Picture Rock Trail, the Wild Turkey Trail, and the Ponderosa Loop. The south side of the park will remain closed at least through Sept. 30, 2021, so the area can be restored to safe conditions.

Safety Hazards in Closed Areas

We ask that all visitors be respectful of the closures due to safety hazards in the burn areas and the fragile landscape that needs a chance to heal.

Falling Trees

Falling trees are a serious hazard. While hazard trees have been removed from the trail corridors of open trails (see details below), there are still lots of trees in the closed areas that could fall at any time, especially during windy conditions.


Flash floods are a real concern in burn areas. The severely burned landscape is likely to flood all small and large canyons and deposit tons of debris and mud in many areas including the Heil Valley Ranch main trailhead. It is expected that rain events as small as 0.35 inches in 15 minutes or 0.75 inches in one hour could cause a flash flood at Heil Valley Ranch. Because of this, Flash Flood Warnings will be issued when rainfall at these levels are detected by radar or reported by spotters. Small Stream Flood Advisories will be issued for lower rainfall amounts, 0.5 inch in one hour. A Flash Flood Warning means immediate action is needed to protect life and property. An Advisory is issued for minor flooding that is not forecast to be a threat to life or property. However, the Advisory may be upgraded to a Flash Flood Warning if additional rain falls (see below for National Weather Service term definitions). Keep in mind that these rainfall thresholds are commonly seen as frequently as 2-3 times per year. It doesn’t take much rain on a burn scar to cause flash flooding and debris flows.

The risk of flash flooding with associated debris flows and mud flows is increased by soils previously saturated by snow or smaller rain events. The combination of conditions that can trigger a debris flow can make them unpredictable. Saturated soils are more common in the spring, and afternoon thunderstorms are common during the monsoon season (approximately June 1 through Sept. 30).

Flash flooding and debris flows may affect:

  • Marietta and Plumley canyons
  • Fire access road north from Main Trailhead parking lot to Plumley canyon
  • Main Trailhead parking lot
  • Geer Canyon and Geer Canyon Road
  • Corral Trailhead parking lot
  • Lefthand Canyon Drive
  • Lefthand Creek between Geer Canyon Drive and US36 and downstream to Longmont

Flooding is likely to be seen in Lefthand Creek all the way to Longmont and beyond. Discolored, muddy, sediment-laden, and/or ashy water is expected and water may have higher levels of certain contaminants than normal runoff.

Recovery Plan

Steps for Emergency Watershed Protection

  1. Contract out Aerial Mulching (includes hazard tree removal and processing and mastication).
  2. Contract out design and construction of sediment basin and check dams.
  3. Continue to work with stakeholders to identify and fund unmet needs on USFS and private lands.
  4. Get the work done on the ground.
  5. Data collection and adaptive management.

Hazard Tree Removal

Heil Valley Ranch trail and road sections that experienced high/moderate severity require complete removal of burned trees to provide safe work areas and prepare for future safe public access. The following trails and roads will require clearing all trees approximately 60 feet on either side. Some work has and will be done by staff, while the bulk of the work will be contracted out as part of the larger aerial mulching work.

  • Wild Turkey Trail: 1,328 ft. (completed)
  • Wapiti Trail: 5,543 ft.
  • Lichen Loop: 4,609 ft.
  • Overland Loop: 2,251 ft.
  • Grindstone Quarry Trail: 454 ft.
  • Main Access Road: 6,479 ft.
  • Total linear distance: 20,664 ft. (3.19 miles)

Aerial Mulching

Mulching operations began in early May. Contractors are applying approximately five tons of wood shreds per acre, to attain 70% coverage on the ground.

Mulch is used post-fire to replace the cover (vegetation, litter, duff, and even the canopy of trees) that was lost during the fire. Mulching is one of the most effective emergency stabilization techniques to use post fire (Robichaud et al. 2000; Bautista et al. 2009). Mulch stabilizes soil, reduces sediment movement, prevents loss of soil productivity, and reduces risk of flooding (Bautista et al.)

The trees killed by the Cal-Wood fire are processed onsite to create the wood mulch for this effort. This is a win-win, removing hazard trees along trails and roads and reducing the need to import material. Wood shreds also have the benefit of being weed free, when compared to commonly used straw, and are not moved as easily during wind events.

Wildlife Concerns

Staff is working with NRCS and US Fish and Wildlife Service to ensure protection of sensitive species occurring in the project area. Staff follows federal guidance such as the Bald and Golden Eagle Protection Act when planning restoration activities.


Tasks Approx
Start Date
End Date
Access Roads Maintenance & Restoration 3/8/2021 1/6/2022
Bridge Replacement 4/21/2021 2/14/2022
Cultural Resources Survey 11/1/2021 11/2/2022
Culvert Replacement 2/17/2021 9/17/2021
Fencing (Volunteer Project) 4/5/2021 1/4/2022
Forest Disease/Insect Control 1/4/2021 1/4/2024
Hazard Tree Removal 11/2/2020 10/31/2025
Mitigation and Restoration Measures Contract 2/1/2021 9/9/2021
Mulching Contract 1/11/2021 8/31/2021
Park Bench Replacement 3/15/2021 5/31/2021
Temporary Signage, Flash Flood Signage, and Permanent Signage 10/19/2020 3/31/2022
Trail Protection & Restoration 4/1/2021 9/29/2023
Trailheads/Parking Lots & Amenities 3/3/2021 4/7/2022
Tree Planting in Critical Need Areas 9/1/2021 11/17/2023
Vegetation Recovery & Protection 10/19/2020 10/31/2023
Weed Management 5/3/2021 10/3/2022
Wildlife Resources Habitat Restoration 4/5/2021 4/1/2025


Recent Photos

Emergency Alerts

Sign up to receive reverse 911 emergency messages for potential flooding. Messages are generated by the Office of Emergency Management using Everbridge Alerts. To add Heil Valley Ranch trailhead, use the following address:

  • Heil Valley Ranch Main Trailhead – 1188 Geer Canyon Rd.

Sign Up

National Weather Service Term Definitions


A warning is issued when a hazardous weather of hydrologic event is occurring, imminent or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action.

Cal-Wood Rainfall Guidance

  • > ¾ (.75”) of an inch in < 1 hour  > .35 inch in < 15 minutes.

Lefthand Canyon Rainfall Guidance

  • > 1 of an inch in < 1 hour  > ½ (.5”) inch in  < 15 minutes.


A watch is used when the risk of a hazardous weather or hydrologic event has significantly increased, but its occurrence, location or timing is still uncertain. A watch means that the hazardous weather is possible. People should have a plan of action in case a storm threatens, and they should listen for later information and possible warnings especially when planning travel and outdoor activities.


An advisory is used when a hazardous weather or hydrologic event is occurring, imminent or likely. Advisories are for less serious conditions than warnings, which cause significant inconvenience and if caution is not exercised, could lead to situations that may threaten life or property.

Cal-Wood Rainfall Guidance

  • ½ (.5”) inch  in < 1 hour

Lefthand Canyon Rainfall Guidance

  • 3/4 (0.75″)  inch  in < 1 hour

Post-Fire Risk Meetings

Boulder County held two Post-Fire Flood Risk Virtual Meetings in April. The potential for hillslope erosion may cause small or large landslides and debris flows in a flash flood scenario. Post-fire flood risks were discussed at the meetings, including how residents and visitors can prepare, stay alert, and be forewarned of potential risks.

Projected Costs & Funding

  • Boulder County is the local sponsor for USDA Natural Resource Conservation Service Emergency Watershed Protection Program funding for $5.3 million. This program is for post-fire interventions on local, state, and private land aimed at reducing the potential for massive flooding and soil erosion this summer. This funding covers aerial mulching, sediment control, and improved early warning systems. Boulder County, as the local sponsor, will contribute 25% of this amount ($1.2 million) to implement these important emergency actions.
  • The State of Colorado has committed to sharing the non-federal match for the Natural Resource Conservation Service Emergency Watershed Protection Cal-Wood Fire Recovery federal programs. This will cover approximately $660,000 of the county’s 25% match for the aerial mulching and erosion control.
  • The Colorado State Water Board has awarded Boulder County $550,000 for additional aerial mulching on severely burned and highly erodible soils owned by the USFS. This will cover 220 additional acres targeted to reduce soils erosion and establish vegetation.


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Parks & Open Space

Sharla Benjamin