PERMAFROST — BLACK 293 



types particukrl}^ and cuts down yields. Production difficulties and 

 costs go up (Fagin, 1947). 



Refrigeration and storage. — Natural cold-storage excavations are 

 used widely in areas of permafrost. They are most satisfactory in 

 continuous or discontinuous zones. Permafrost should not be above 

 30° F. ; if it is, extreme care in ventilation and insulation must be 

 used. Properly constructed and ventilated storerooms will keep meat 

 and other products frozen for years. Detailed plans and charac- 

 teristics required for different cold-storage rooms are described by 

 Chekotillo (1946). 



Trafjicability. — In the Arctic and sub-Arctic most travel overland 

 is done in winter, as muskegs, swamps, and hummoclcy tundra make 

 summer travel exceedingly difficult (Navy Department, 1948^9; 

 Fagin, 1947). Tracked vehicles or sleds are the only practical types. 

 Wheeled vehicles are unsatisfactory, as most of the area is without 

 roads. 



Permafrost aids travel when it is within a few inches of the sur- 

 face. It permits travel of D8 caterpillar tractors and heavier equip- 

 ment directly on the permafrost. Sleds weighing many tons can 

 be pulled over the permafrost with ease after the vegetal mat has 

 been removed by an angle-bulldozer. Polygonal ground, frost blisters, 

 pingos, and small, deeply incised thaw streams (commonly called 

 "beaded" streams), rivers, and lakes create natural hazards to travel. 



In areas of discontinuous and sporadic permafrost, seasonal thaw is 

 commonly 6 to 10 feet deep, and overland travel in summer can be 

 accomplished in many places only with amphibious vehicles such as 

 the weasel or LVT. Foot travel and horse travel are very slow and 

 laborious in many places because of swampy land surfaces and neces- 

 sity for making numerous detours around sloughs, rivers, and lakes. 



Military operations. — Permafrost alters military operations 

 through its effects on construction of airbases, roads, railroads, revet- 

 ments, buildings, and other engineering projects; through its effects 

 on trafficability, water supply, sewage disposal, excavations, under- 

 ground storage, camouflage, explosives, planting of mines, and other 

 more indirect ways (Edwards, 1949; Navy Department, 1948-49). 

 Military operations commonly require extreme speed in construction, 

 procuring of water supply, or movement of men and material. Un- 

 fortunately it is not always humanly possible to exercise such speed 

 (Fagin, 1947). Large excavations require natural thawing, aided 

 possibly by sprinkling (Huttl, 1948), to proceed ahead of the earth 

 movers. Conversely, seasonal thaw may be so deep as to prevent the 

 movement of heavy equipment over swampy ground until freeze-up. 

 Or, similarly, it may be necessary in a heavy building to steam-jet 

 piles into permafrost and allow them to freeze in place before loading 



