Containment of the Derby Fire nearly quadrupled from Monday to Tuesday as firefighters made gains on the north and south flanks of the blaze burning in northwest Eagle County. Containment as of Tuesday morning is 23%.

According to an update from the Rocky Mountain Area Complex Incident Management Team 3, the wildfire has burned into a steep rock face on its northern edge, which creates a natural barrier to fire spread. Days of dedicated mop-up and cold trailing operations have secured the handline and dozer line on the southern edge, contributing to the rise in containment.

As containment increases on the fire, personnel are being moved out. Total personnel dropped from 574 on Monday to 531 on Tuesday as two hand crews were assigned elsewhere. There are five aircraft, 26 engines and nine pieces of heavy equipment working the fire on Tuesday.

Fire intensity increased on Monday on the southwestern side of the fire in the area of the county line and West Fork Sheep Creek. Helicopter water drops assisted a fire suppression module on the ground that was working to extinguish hot spots.

On Tuesday, firefighters will continue their work in the area. Air resources will have a busy day delivering firefighters, medical, and support personnel to all sides of the fire. A hotshot crew will be moved to the north flank of the fire to work directly on the fire’s edge in the West Fork Sheep Creek drainage in the Flat Tops Wilderness Area.

Firefighters utilize specific tactics when fighting fire in wilderness areas to minimize near and long-term impacts to the natural environment while most effectively engaging the fire. Additional firefighting resources have arrived on the incident and will be flown to the northeastern corner, where they will work south extinguishing hotspots on the fire’s edge. Hand crews spiked near the West Fork Red Dirt Creek will continue to advance handline construction toward crews working north from Poison Creek. Specialized medical personnel will be staged nearby to assist crews in the event of an emergency.  

Fire activity is expected to increase on Tuesday as temperatures will be in the low 70’s. Humidity levels are expected to drop into the teens, with a very low chance of precipitation. Lower humidity levels mean that there’s less moisture in the air and light fuels like grasses, leaves and brush dry out.

Light fuels are more sensitive to changes in moisture and are more conducive to burning. Fire behavior analysts don’t expect a significant increase in fire behavior; however, firefighters will watch for an increase in creeping, smoldering and isolated tree torching.