Recovery work is mostly complete at Heil Valley Ranch from the devastating Cal-Wood Fire. Recovery operations included hazard tree removal, aerial mulching, erosion and debris mitigation, and replacing damaged visitor amenities and park infrastructure including bridges, fencing, parking stops, and signs.
Heil Valley Ranch Cal-Wood Fire Recovery
The Cal-Wood Fire started on Oct. 17, 2020, 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).
Safety Hazards in Closed Areas
We ask that all visitors remain on trail and be respectful of the closures due to safety hazards in the burn areas.
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. People also can get injured by stepping into holes left behind after the trees (both trunks and roots) burned and/or fell.
Flash floods are a real concern in burn areas especially after the soil has absorbed as much moisture as possible from previous storms or snow melt events. The severely burned landscape is likely to flood all small and large canyons (depending on where rainfall occurs) and deposit tons of debris and mud in many downstream/downslope areas including the Heil Valley Ranch main trailhead. We have seen rain events as small as 0.35 inches in 15 minutes or 0.75 inches in one hour causing alarming flash floods at Heil Valley Ranch. We have been lucky because so far the rainstorms have been of short duration.
Flash Flood Warnings will be issued when rainfall of concerning intensity and duration 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).
- All severely burned canyons and protected species within.
- Residents within Geer Canyon.
- All access roads downhill from severely burned areas.
- Main Trailhead parking lot.
- Corral Trailhead parking lot and the equestrian parking lot.
- Lefthand Canyon Drive downhill from 1 Geer Canyon Drive.
- Left Hand Creek between Geer Canyon Drive and US36
- Water quality downstream of Geer Canyon Drive (Longmont and other incorporated and unincorporated communities).
Flooding is likely to be seen in Left Hand 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.
|Task||Details||Approx Start Date||Approx End Date|
|Temporary Signage, Flash Flood Signage, & Permanent Signage||Currently all signage is under re-evaluation. Physical signage installation is ongoing as needed for property closure, trail closure, trail rerouting, and burned sign replacement. Flash flood signage installation was completed.||Oct-2020||Temp- April 2022
Permanent – May 2022
|Hazard Tree Removal||Trees will continue to die over the next 10 years. Tree health will continue to be monitored and trees removed if they become a hazard along trails, roads, or parking lots.||Oct-2020||Ongoing|
|Wildlife Resources Habitat Restoration||Continuous coordination with other disciplines to discuss mitigation of potential impacts to wildlife per other project activities. Planning and implementation of habitat enhancement and maintenance opportunities will continue.||Nov-2020||2025|
|Forest Disease/Insect Control||Selective treatments were applied in 2021, will be renewed annually, and forest health will continue to be monitored.||Jan-2021||2024|
|Mulching Contract||Aerial operations complete as of Aug. 9, 2021. Final demobilization of equipment week of Aug. 16, 2021.||Mar-2021||Completed|
|Access Roads Maintenance & Restoration 2021||The access roads were actively maintained in the rainy season of 2021, and will continue to be maintained after rainfall events with high-energy flows. Smaller road drainage culverts installed by BCPOS August through December 2021; Small and large stream crossing culverts were designed by the Design-Build team in 2021 and will complete installation in April 2022.||Mar-2021||TBD (rain event dependent)|
|Weed Management||Weeds are a substantial problem post-fire. While good native growth occurred, weed challenges will continue to be addressed utilizing integrated pest management methods.||Mar-2021||Ongoing|
|Fencing (Staff and Volunteer Projects)||The majority of the burned fence was replaced by staff and volunteers and completed Dec. 2021 before eagle buffer closings.||Apr-2021||Completed|
|Tree and Shrub Planting in Critical Need Areas||Limited planting of locally sourced willows has occurred along Geer Creek and tributaries, and additional riparian planting of shrubs may take place in future years as warranted.
4,000 ponderosa pine tree seedlings are being planted in select areas in the spring of 2022. Staff continues to evaluate the need for additional plantings in strategic locations.
|Vegetation Recovery & Protection||In-house seeding and mulching of three of the four staging areas occurred in the fall and will be monitored and maintained as needed. The fourth staging area will be stabilized in 2022. Revegetation of impacts due to road and culvert work as well as the construction of sediment capture structures will continue in 2022.||2021||Ongoing|
|Trail Protection & Restoration||Flash floods and debris flows will continue to make trail protection and restoration necessary in these first few years after the fire.||Apr-2021||Completed initial clearing, future rain event dependent|
|Flood and Debris Flow Mitigation Construction||Federal and State Cost Assistance: design started in April 2021, construction actively started August 2021, EWP funding agreement extended through April 29, 2022. Funds for on-going adaptive management and floodplain and riparian area enhancement are being sought.||Aug-2021||Apr-2022 and while the risk is high for debris flows|
|Trailheads, Parking Lots, and Amenities||Items burned are being replaced. Stream and floodplain restoration work is underway to prepare for debris flows, flash floods, and protect downstream roads, houses, and the traveling public. The majority of work will be completed by spring 2022 but weather events may trigger more work to repair erosion and the impact of debris flows.||Sept-2021||May-2022 and future rain event dependent|
|Cultural Resources Re-Survey||11 days of fieldwork completed in 2021. Fieldwork data processing and reporting to be completed by March 1, 2022.||Oct-2021||Mar-2022|
|Park Bench Replacement||Two benches were burned and will be replaced.||2021||May-2022|
|Bridge Replacement||Three bridges burned and will follow a design and contracting process to re-install access across the creek at the main trailhead and along the Wapiti trail.||2021||Temporary Bridge: May 2022
Permanent Bridge: Risk-dependent, currently under evaluation
Trails in the closed areas became overgrown with weeds and vegetation. Trail restoration was completed in the fall of 2021. Almost 11 miles are currently open, just over 8 miles are closed. In the closed areas, 5 miles of trail needed and received work by staff and volunteers. Minor touch-ups will need to occur on several miles before opening. Conditions will be monitored after precipitation events for any debris deposition on trails.
Wapiti Trail Detour Due to Wildlife Concerns
Boulder County works with Colorado Parks and Wildlife and the U.S. Fish and Wildlife Service (USFWS) to ensure protection of sensitive species. Staff follows federal guidance, such as the Bald and Golden Eagle Protection Act, when planning restoration and/or recreation activities.
During the 2020/2021 nesting season, one of the golden eagle nesting pairs in the fire area completely rebuilt their burned nest and successfully fledged one young. Boulder County biologists worked with USFWS to develop a strategy to protect the Heil Valley Ranch eagles during many months of intensive recovery operations. Staff and contractors avoided the critical half-mile zone around the nest, and instituted measures effecting the timing and approach to work: No-fly zones for helicopter mulching were delineated to protect the space around the nest, weekly observations documented eagle behavior and chick development, and frequent updates on the status of the nest provided feedback to the team.
The pair returned for the 2021/2022 nesting season and are expected to return annually, necessitating a trail detour away from the nesting site. The detour will be in place year-round for the next several years to allow for monitoring of nest activity.
Hazard Tree Removal
Heil Valley Ranch trail and road sections that experienced high/moderate severity required complete removal of burned trees (also known as hazard trees when in close proximity to public access points) to provide safe work areas and prepare for future safe public access.
The following trails and roads required clearing all burned trees approximately 60 feet on either side.
- Wild Turkey Trail: 1,328 ft.
- 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.
Mulching operations on Heil, private, and USFS lands began in early May and were completed in August. Wood shred mulch was applied over 2,115 acres utilizing 10,870 tons of wood.
Mulch was used 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 were processed onsite to create the wood mulch for this effort. This was 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.
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.
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 is high for hillslope erosion to 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 events.
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, and the State of Colorado through the 2021 Special Release of the Colorado Watershed Restoration Program will contribute 25% of this amount ($1.2 million) to implement these important emergency actions
- The Colorado State Water Board awarded Boulder County $550,000 for additional aerial mulching on severely burned and highly erodible soils owned by the USFS. This covered 272 additional acres targeted to reduce hillslope erosion.
- SER-RM Webinar: Lessons from the Cal-Wood Fire – Staff presentation on the fire and recovery efforts
- Next Steps After Cal-Wood & Lefthand Canyon Fires – Main recovery page for area residents
- Burned Area Emergency Response Report (BAER) – U. S. Forest Service
- FAQs About Soil Erosion and Impacts to Water Resources and Infrastructure – Colorado Water Conservation Board
- Flood After Fire – Burn Scar Flash Flood & Debris Flow Threat – National Weather Service
- Boulder Watershed Collective
- Interview with BCPOS Senior Forester Stefan Reinold – Podcast for our Environment
- Left Hand Creek Watershed Conceptual Model – Left Hand Watershed Center
- Bautista, S.; Robichaud, P.R.; Blade’, C. 2009. Post-fire mulching. Chapter 13. In: Cerda, A; Robichaud, P.R., eds. Fire effects on soils and restoration strategies. Enfield, NH: Science Publishers: 353-372.
- Robichaud, Peter R.; Lewis, S. A.; Wagenbrenner, J.W.; Ashmun, L.E.; Brown, R.E.; 2013a. Post-fire mulching for runoff and erosion mitigation: Part I: Effectiveness at reducing hillslope erosion rates. 105: 75-92.
- Robichaud, Peter R.; Wagenbrenner, J.W.; Lewis, S. A.; Ashmun, L.E.; Brown, R.E.; Wolgemuth, P.M.; 2013b. Post-fire mulching for runoff and erosion mitigation: Part II: Effectiveness in reducing runoff and sediment yields from small catchments. 105: 93-111.
- Robichaud, Peter R.; Ashmun, Louise E.; Foltz, Randy B.; Showers, Charles G.; Groenier J. Scott; Kesler, Jennifer; DeLeo, Claire; Moore, Mary. 2013c. Production and aerial application of wood shreds as a post-fire hillslope erosion mitigation treatment. Tech Rep. RMRS-GTR-307. Fort Collins, CO; U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 31 p.
- Rhoades, Charles; Robichaud, Pete; Ryan, Sandra; et al. 2017. Learn from the Burn: The High Park Fire 5 Years Later. Science You Can Use Bulletin, Issue 25. Fort Collins, CO: Rocky Mountain Research Station. 18 p.