CHAPTER 7 



FIRE CASE HISTORIES 



Why do fires in Interior Alaska get so large 

 so fast? What is the actual rate of perimeter and 

 forward spread? What weather factors are as- 

 sociated with various rates of spread? And, is 

 the rate of spread significantly different between 

 fuel types? 



Preliminary investigation of research needs 

 showed an almost complete lack of recorded 

 data in the form of weather, fuels, or behavior 

 that would aid in answering these questions. 

 In 1958 a case history study of fires in Interior 

 Alaska was started. During that and the follow- 

 ing year, two 2-man teams, equipped with port- 

 able fire-weather stations (fig. 59), gathered 

 data from 19 fires,- case histories of seven are 

 presented here (fig. 60). 



USPS 



Figure 59. — Portable fire-weather station. 



The most valuable data were collected dur- 

 ing the free-burning period before control action 

 altered the spread rate of the fires. Thus, data 

 for several of the fires cover a period of only a 

 few hours, even though the fires may have 

 spread for a much longer time. Results of this 

 study indicate that nearly all extreme behavior 

 can be explained qualitatively but not quantita- 

 tively. 



HEALY FIRE 



The Healy fire burned 40,320 acres because 

 of continual high winds. Healy is on the lee side 

 of a major pass in the Alaska Range, between 

 the Anchorage-Susitna River area and the Ne- 

 nana River-Fairbanks area. Prevailing winds 

 augment night downslope winds and override 

 daytime upslope wind tendencies. Nonuniform 

 topography downwind may also have caused 

 erratic local winds and eddies. 



The fire originated in a coal seam that had 

 been smouldering for several years. At the time 

 of discovery, midafternoon on July 4, 1958, it 

 covered 50 acres. By 2300 it had increased to 

 100 acres, and was burning on steep, rocky 

 terrain covered with black spruce, brush, and 

 dense grass. 



Excerpts from the narrative report of the fire 

 indicate the influence of the continual high winds 

 in thwarting early control: 



The wind made it almost impos- 

 sible to do anything for about the first 

 two weeks of the fire . . . 3 / 4 of the 

 time men on the ground couldn't keep 

 ahead of the fire . . . 



After five inches of rain and four 

 days since the last smoke, we felt rea- 

 sonably safe and left the Healy wind 

 tunnel. 



Weather and behavior records collected by 

 the team after its arrival on July 8 showed that 

 the major runs occurred on July 9, 10, and 11, 

 although relative humidity was rarely below 50 

 percent and burning index was around 20. The 

 worst burning condition prevailed on July 26 

 (32 percent relative humidity, burning index 44); 



69 



