24000 



Figure 11. — Rate of energy release at fire front over 

 a 12-hour period on September 1. 



upper limit of 30,000 B.t.u./sec.-ft. for large 

 wUdfires, whereas we derived a value of 

 22,500 B.t.u./sec.-ft. for the Sundance Fire. 



The values given here are only approxima- 

 tions, since the derived residence time is an 

 estimate. Each level of fuel and each size of 

 fuel has its own residence time, which may or 

 may not overlap that of the next size. This 

 means residence time may be underestimated 



1200 1400 1600 . 1800 2000 2200 2400 

 Time ot dav (hours) 



Figure 12. — Fire intensity calculated by Byram's 

 method for a 12-hour period on September 1 . 



because of the sequential ignition and bum- 

 out of fuel sizes in increasing order. This 

 probability seems partially verified by the 

 nature of the flame-depth values, which were 

 determined using the assigned residence time 

 and the deduced rate of spread. Flame depth 

 varied from a minimum of 44.0 ft. to a maxi- 

 mum of 264.0 ft., a range that appears narrow 

 for the existing conditions. 



FIRE LOG FOR SEPTEMBER 1 



0700. Fire area 4,000 acres; fire edge extends from ridge between East River 

 and Lost Creek north around Sundance Mountain and down into 

 Soldier Creek. 



Weather. Free-atmosphere conditions at 5,000 ft.: Winds 14 m.p.h. 

 SW; relative humidity 25 percent; dry-bulb temperature 71° F. 



Up to 1300. No significant increase in fire area. Increased activity in Lost 

 Creek showed the fire front was becoming more active. Weak convec- 



13 



