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Technical Note (National Research Council of Canada. Division of Building Research), 1955-11-01
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Food Storage in Permafrost Dickens, H. B.
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DIVISION OF BUILDING RESEARCH
No.
FOR INTERNAL USE
DATE November
1955
APPROVED BY R.F.Lo 205NOTlE
J.A.P. CHECKED BYFood Storage in Permafrost
'IfE
C
JH[
N ][
(!
AlL
Department of Northern Affairs and National Resources H.B. Dickens
SUBJECT
Individual Storage Pits
The 'aim of even the most primitive permafrost storage pit is to preserve food in a frozen state over at least one
Even in the most northerly regions of Canada there is a need for cold storage facilities for food during ｴｾ･ warm part
of the year. This need has assumed increased importance with recent emphasis on northern development. To meet the demand for such-facilities eCGnomically it has been proposed that the natural cold storage properties of permafrost be utilized. While there is evidence that in some parts of the North,
particularly in Russia, permafrost plays an important part in the food storage methods of the people, little published
ｩｮｦｯｾｭ｡ｴｩｯｮ is available describing the construction and operation of these cold storage pits or cellars.
It is therefore proposed in this note to outline some of the factors which merit conElderation when planning permafrost storage facj.lities. This outline is based on a survey of the limited amount of literature available and on examination of one or two such installations in the field. It is written against a background knowledge of permafrost properties in general.
Food storage places in permafrost may be of two types: small pits intended for individual use and larger storage cellars for industrial or commercial use. The first type is generally only a nole in the ground but the second and larger
ｫｩｾ､ may be a labyrinth of tunnels and vaults in the permafrost
ｷｾｴｨ access by a ｶ･ｾｴｩ｣｡ｬ shaft into the ground or by an excava-tion into the side of a hill.
PREPARED BY
NOT FOR PUBLICATION
'. "
2
｡ｮｾ possibly two summer seasons. This objective should not be confused with normal cool storage for daily use.
1. Size. - The size of individual pits varies with the number of persons served; pits 8 feet square are fairly common. The " depth of the pit must· always be sufficiently below the ｡｣ｴｩｶ･ＭＮｾﾷＧﾷ
layp.r to ensure that the lower part of the pit remains ｦｲｯｺｾｮＮ
This will naturally vary with local factors and conditions
.of
use but rarely should a pit be less than7
feet deep.2. Location. - ｌｾ selecting a site for a storage pit, the
type of s011 and the conditions of drainage must be considered. Although permafrost can provide an excellent temperature
environment for food storage it may also lead to difficult drainage problems which can create a hazard by causing stored food to become contaminated with sewage or other wastes. Good surface drainage is essential.
In
the southerly regions of permafrost, areas that have puddles in the spring, or where there is a bubbling spring nearby, can be free of permafrost and hence these areas should be avoided..
Clay soils are preferred for ttese storage pits because such soils have a low thermal conductiVity and tend to retain the cold longer. Granular materials are the least desirable types of soils in which to place these pits because they have a high thermal conductivity, thus picking up heat more quickly, and they are also more difficult to excavate. Peaty soils
containing large ice laminat.ions withstand thawing the lon.gest but because of their high moisture content they make the
drainage problem potentially more severe .
.
3.
Construction. - A typical permafrost food storage pit is shown in FIg. 1 (1).Such a pit should be excavated in the fall because by that time of the year the ｧｲｯｾｾ､ has thawed to its greatest depth and excavation is more easily carried out. Another advantage of doing this work in the fall is that by then the daily air temperature is usually below 320F so that water seeping into the pit will freeze and keep the pit in a drier condition. Individual pits are generally dug With simple hand tools such as crowbars and shovels. The amount of work
involved in the excavation of an average size pit will depend on the type of soil and the depth of the thawed layer.
The degree of timbering of the finished pit varies with
it9 anticipated use. The simplest form of storage pit
with a minimum of wood framing. , Boarding of the sides is done only where such a lining is essential as with granular materials. The opening at the top is closed off by a wooden cover containing a simple trap door with access to the pit by a wooden ladder. Earth is often placed over the cover as insulation.
Storage places to be used for longer periods are constructed with more care. The sides of these pits are generally lined
with wood and the space between the wall and the permanently fr.ozen ground is sometimes packed with moss as insulation. Occasionally the pit is made deep enough to store food at two levels. The floor of the upper level is framed with wood members and With a trap door providing access to the space ' . below. The opening at the surface of the pit is protected by a small log or insulated wood frame bUilding with a door to the
outside and with a trap door in the floor to the pit below. Even in the most primitive type of pit drainage must be controlled. Some form of raised floor should be provided at the bottom of the pit and food should be carefully placed away from the sides of the excavation to avoid possible contamination by seepage.
4.
Operation. - Corrett operation of the completed storagepit wlll do much to increase its period of useful service. Such operation is very simple. During the winter months all doors should be left open to permit the naturally cold outside air to penetrate the pit and thus lower the temperature of the excavation and of the surrounding soil. In this way the
reserves of cold in the ground can be replenished systematically from year to year.
In the spring when the temperature outside rises above 10°F the top structure should be tightly closed and during the summer it should only be opened when necessary to obtain food and to permit just sufficient ventilation to prevent mould growth,
5.
Performance. - The performance of a permafrost storage pitwill vary with the metho0 of use. One pit examined in Aklavik had a temperature in the pit;of -lOoF early in May and by, September of that year due to normal usage the temperature had risen to 28°F. In some years the temperature had gone above freezing. It has been suggested that by proper ventilation during the Winter months and careful use during the summer season the average
annual temperature in a permafrost storage pit can be maintained at between 150 and 20oF.
4
ｾ Industrial or Commercial Cellars
Permafrost has been utilized for large-sized cold storage cellars only to a very limited degree. There is eVidence, however, based on Russian experience and from installations in Alaska that such large scale storage facilities are practic-able.
-Stefansson reports in his "Arctic Manualll
(2) that meat can be stored in underground chambers for years with only the precaution of avoiding certain moulds which flourish at ground temperatures, at least down to 200 below freezing. If these moulds get into the storehouse the meat must be removed and the mould destroyed either chemically or by peeling an inch or two of earth from floors, walls, and ceiling. This manual also reports that both reindeer meat and domestic beef have been preserved in perfect condition for a period of
!'our years in gal.J..eries utilizing ｴｨｾ natural underground temperatures of Alaska of about 10oF.
An article by A.M. Chekotillo (3) indicates that the
best way to store meat in a permfrost pit or cellar is to pour water over the meat during a very cold spell (quickfreeze it) . and then place it thus frozen in the storage place where it will remain in an excellent state of preservation for at least a year.
In general the large type storage places differ from the small indiVidual pits not only in size but also'by being
placed at greater depth, usually at least '15 to 20 feet from the surface. At this depth 'in the ground the temperature of the frozen soil is not greatly affected by the seasonal changes above. The constant temperature at a depth of 15 to 20 feet varies from only slightly below freezing'in the most southerly limits of permafrost down to 100F in the Arctic regions.
The following interesting description of a large under-ground cold storage place in Alaska has been given by S. Taber in hif'. article on "Perennially Frozen Ground in Alaska: Its Origin and ｈｩｳｴｯｾｹｬｬ (4):
"The underground cold storage vault at Baldwin on Elephant Point was constructed by Lomen Commercial Company for
the storage of reindeer meat until it can be shipped to the United States in refrigerator ships during the summer. The (xcavations were made in frozen-silt containing abundant plant remains. A tunnel 150 feet long was driven horizontally into a hill haVing a slope of about 150 . An anteroom about 14 feet square was constructed a short distance in from the entrance, and four rooms, each 26 feet wirle by
68
feet long and8
feetReferences:
(2) Stefansson, V. Arctic Manual. Published by the Macmillan Company, 1944.
(1) Alter, Amos J. Relationships of Permafrost to
Environmental Sanitation. Paper presented at Alaskan Science Conference held in Washington, November 9-11, 1950.
Perennially Frozen Ground in Alaska: Its History. Bulletin of the Geological
America, Vol. 54, p.1433-1548. October 1st, Chekotillo, A.M. The Underground Storage Places in the
Permafrozen Ground. Privoda, Vol. 11, 1946, ｰｰ［ＲＷｾＳＲＮ
Translated from the Russian by Dr. Eugene ａＮｇｯｬｯｭｳｨｾｯｋ
and published by The Stefansson Library, 67 Morton St., New York 14,
N.Y.
November 1947.high, were opened up, two on each side of the tunnel. They are ｳ･ｰｾｲ｡ｴ･､ from one another and from the ｴｾｾ･ｬ
by walls of frozen silt, about 6 feet thick, left to supfort the overburden. At the far end of the tunnel two ventilation shafts extend to the surface. They are protected on top by ｾｭ｡ｬｬ houses having trap doors in the floors. By regulating doors that connect the rooms with one another and with the tunnel, cold air in
winter can be diverted into any of the rooms or merely circulated through the tunnel. During the summer all doors are kept tightly closed. The two front rooms as well as the entrance to the tunnel and the anteroom are provided with heavy ｣ｯｬ､ｾｾｴｯｲ｡ｧ･ doors of standard make." Taber, Stephan. Origin and Society of 1943. (4)
FOOD STORA(JE
PIT
FOR
USE
IN
FERfV1ANENILY
FROZEN
GROUND
Fig_ I
Reproduced from a Paper on ItRelati h
of Permafrost to E _ ons.ips
