A RCTIC CIRCULA NO. I Notes on a trip in l6-foot ... - The Arctic Circle

VOL, XV No" 4 T F:E,\ IIC TiC CIF.E I]L,T.R 55
Ttt At Thompson, located in the southern
frtnge of r perenniaLLy f,tozen ground occurs fun
scattered patches of varylng thickness and depth below the ground
surface and has a temperature ctose to 32oF, Construction operatlone
in thie area are complicated by d'lfficulty ir predicting the exlstence
of permafrost. ln additi.on, very little disturbance or change ln the
local environmental condittons, such as removal of the insulatfung moss
cover or erectlon of a building, will cause signi.ficant thawing. Larges
cale s ettiements rr)3,1r r esult f rom thawlng b ecaus e of the thic kn es s of
the extensit'e ice lenses ln the soil"
Detailed studies have been carrled out to determlne the
occurrence and distrlbution of permafrost tn the townslte and adjacent
areas. Special emphasis was placed on a study of climatlc factors and
terraln f,eatures , e. g o relief , drainage, and vegetation, ln an attempt
to establi.sh co rrelations between thes e features and the exlstenc e and
location of the permafrost bodies " Ground temperatures are belng
measured at selected locations " Surface and subsurface observatlons
have revealed that perennially frozen ground ts generally found in gently
sloping , moderately drained areas with sphagnum mos s cover.
Permafrost was not encountered in poorly dralned, low, flat ephagnummoss
-cove red areas , or ln ',velt-dralned, high areas free of sphagnum
rrross and adjacent to the sloping areas, Exceptione were noted, however,
that are not easily explained because of the complex lnterrelatlonshlps
between the varlous factors affecting the exlstence of permafrost.
Engineering studies have aiso been lnltiated to follow the
performance of the variou-s types of foundatlons constructed in the
townsite. Reference polnts have been establlshed on a number of
buildLngs so that movements can be followed by means of level surveys r
Several deep bench-marks were placed to depths of 40 to 60 feet to
facllitate these observat:.ons o A number of buitdlngs have experlenced
differential settlemente of as much as 2 feet as thawing of the underlylng
frozen ground occurs "
Pernq?frost dlstrl.Puii.onl The collectton of lnformatlon on the
occurrence and dlsiribution of permafrost in Canada has continued, with
particular emphaeis on tire southern portio:r of the permafrost reglon.
These studies inCicate a lack of informatlon on the more southerly
occurrences of permafrost primarily in the northerrn parts of the
western provinces, and a programrnc of f:.elC inveeilgatloar* ln these areas,
to be carried out over the next fer,',' years, ha,s therefore been planned.