Fire Behavior Associated with the 1994 South Canyon Fire on Storm King Mountain, Colorado
One of our major objectives was to estimate fire spread rates during the afternoon of July 6. This can be done using fire spread models or by calculating the distance and time separating successive fire perimeters. We chose the latter method; the original accident investigators used fire behavior models. Our method of analysis required that we develop a chronological history of the movement and location of individual firefighters. We used witness statements, followup interviews, onsite reenactment of firefighter movement, and calculations based on known physiological capabilities for hotshots and smokejumpers (Sharkey 1994). From the chronology and witness statements we constructed fire perimeter maps. These maps were then used to estimate fire spread rates.
The following is a narrative of firefighter movements and fire behavior on the South Canyon Fire for July 2 through July 6, 1994. Whenever possible, we describe events in chronological order.
The location names are the same as those in the original fire investigation report with some additional areas identified. Specific locations are identified in figure 17, an oblique photograph, and figure 18, a labeled topographical map. We use surnames when referring to individual firefighters. Some titles are used. Full name and affiliation are available in the South Canyon Fire investigation report.
To make it easier for the reader to follow the chain of events surrounding the fire, we regularly refer to four separate firefighter groups (see table 1). These groups are identified by their general location at approximately 1530 hours on July 6. The groups are: (1) The Main Ridge Group, which consisted of part of the Prineville Interagency Hotshot crew and a Bureau of Land Management (BLM) and U.S. Forest Service crew dispatched from Grand Junction, CO; they all worked primarily along the top of the Main Ridge.
(2) The West Flank Fireline Group consisting of nine Prineville Hotshots, seven Forest Service smokejumpers, and two BLM/USFS firefighters who worked on the West Flank Fireline; three of the smokejumpers moved from the West Flank Fireline to the Main Ridge before the entrapment. (3) The Lunch Spot Ridge Group, nine Forest Service smokejumpers who were working primarily south of the Lunch Spot Ridge in the area of the Double Draws just prior to blowup; eight of this group eventually deployed in fire shelters on the upper portion of the Lunch Spot Ridge, the ninth remained near the Lunch Spot. (4) The two helitack crewmembers (one Forest Service and one BLM) make up the fourth group. A helicopter pilot was over the fire a portion of the time.
Table 1—Personnel roster and position at time of blowup.
Reconstruction of the fire position and spread rates required that we accurately determine each group’s location and activity. Specific times are included in the narrative to indicate the sequence of events and to communicate the speed at which the events occurred. These times were determined by linking elapsed times between events such as helicopter ferry times, reenactment and timing of specific firefighter movements, and human physiological calculations to two known clock times identified in the witness statements. The times presented in the narrative represent a “best fit estimate” and should not be taken as absolute. When estimating fire spread rates, the sequencing and relative time differences between events are of more importance than the absolute times. A great deal of fire and crew activity occurred simultaneously among and between the separate groups making chronological description of both the fire behavior and firefighter positions difficult. We have attempted to divide the narrative into geographical regions and have labeled paragraphs with the central location or group being discussed. We include in the narrative weather and fire behavior as described by firefighters at various locations.
The fire perimeters were developed from witness statements, time and distance measurements and estimates, and topographical, weather, and fuel information. Fire spread rates are estimated from elapsed times and distances between successive fire perimeters. Tables of event times, distances, firefighter travel rates, fire spread rates and reference sources are included in appendix B.
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