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Permafrost investigations at Thompson, : terrain studies Johnston, G. H.; Brown, R. J. E.; Pickersgill, D. N.

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Frontispiece No. I - International Nickel Company of Canada Plant Site - Thompson, Manitoba.

Frontlspiece No. 2 - Thornpson townsite - view to West.

(Photographs courtesy of Internatlonal Nickel Cornpany of Canada) NAT IONAL RESEARCH COUNCIL

CANADA

DIVISION OF. BUILDING RESEARCH

PERMAFROST INVESTIGATIONS AT THOMPSON, MANITOBA

TERRAIN STUDIES

by

G. H. Johnston, R. J. E. Brown and D. N. Pickersgill

ANALYZED

Technlcal Paper No. 158

of the

Division of Building Research

OTTAWA

October 1963 ACKNOWLEDGEMENTS

The authors wish to acknowledge and record thelr slncere thanks to the many persons who helped ln the gatherlng of the lnforrnatlon contained ln this report. As wlll be noted in the text, much of the infor- mation on soil and perrnafrost conditlons ln the Thompson area was obtalned from personal contacts at the site and from subsurface investigatlon reports made avallable by varlous firms working in the area. Unfortunately 6pace does not permit recordlng the names of all those who so willlngly provided assistance. The auth.ors would ltke to acknowledge, however, the interest shown by and the co-operatlon of the Internatlonal Nickel compa.ny of canada, Ltdi Mr. J. c. partee, vice-president, Mr. R. w. Hawkins, chief Engineer, and Mr. E. Kalrnanovitch, Asslstant chief Englneer. special thanks are due also to Mr. c. A" Nesbitt, Resident Adrnlnistrator for the Local Government Dlstrlct of Mystery Lake, who, because of his intimate connection with and his knowledge of the townslte development, was most helpful in providlng lnformatlon and assistance durlng the course of the studies.

underwood, McLellan and Associates, consulting Englneers, saskatoon; (Mr. T'. B. Hicks, Resldent Engineer (195?-59) and Mr. R.E. Bibeau, Resident superwisor since r9s9), who designed. and supbr- vised the installatlon of sewer and water services ln the townslte and who have been involved with much of the ploneer work lnthe areawere most helpful in providing asslstance and informatlon.

The excellent photographs used as a frontispiece were klndly supplied by the International Nickel company of canada, Ltd" TABLE OT' CONTENTS

PAGE

INTRODUCTION

II DE6GR.IPTION OF' AREA

A. Clirnate 1. Meteorology 3 Z. Climatic type 4 3. Air temperature 5 4. Preclpitation 6 5. Surnrnary 7

B. Geology I l. Bedrock geology 7 Z. Pleistoeene Epoch 9

III TERRAIN OBSERVATIONS LZ

A. Re1lef T2 B. Drainage L3 C. Snow Cover I4. D. Vegetation 15 I. GeneraL description l5 Z. Air photo patterns L7 E. Soils t8 I. Soil pr ofile 1g (a) Surface deposlts I9 (b) Brown varved clay 19 (c) Grey varved clay zo (d) Other deposits z0 Z. Soil properties 20 (a) Grain size ZL (b) Specific gravity and densities zz (c) Natural rnoisture contents zz (d) Atterberg Lirnits and Plasticity z3 (.) Activity z4 (f) Alkali concentration z4 I

(i) PAGE

F. Permafrost z4 1. Permafrost observations 1n origlnal townsite z5 Z. Perrnafrost observations ln Westwood sub- divl sion z7 3. Ice segregation 29 4. Ground temperatures 3l 5. T errninology 3Z

IV. PERMAFROST OCCURRENCE AT THOMPSON . A DISCUSSION 33

A. Historical 33 B. Climate 34 c. Terrain Features 37 l. Snow cover 39 Z. Relief 40 3. Drainage 4L 4. Soils 42 5. Vegetation 42 6. Anomalous permafrost occurrences 43 7. Conclusion 44

v. ENGINEERING IMP LICAT IONS 45

A. Permafrost Conditions 45 B. Slte Investigations 46 C. Design and Construction 47

VL SUMMARY

ACKNOWLEDGEMENTS 49

REFERENCES 49

BIBLIOGRAPHY 5l

(ii ) PERMAFROST INVESTIGATIONS AT THOMPSON, MANITOBA

TERRAIN STUDiES

by

G. H. Johnston, R. J. E. Brown and D. N. Plckersgill

Thornpson, Manitoba, (55" 36rN, 98" 4ZtW) located in the north-central part of the province approxirnately 400 air rniles north of (Figure I), is the site of a large recently developed nickel- rnining operation of The International Nickel Cornpany of Canada, Ltd. (INCO). Construction work and development of the site began early in 1957, and the INCO plant was officially opened on 25 March 1961. It is the second largest nickel-producing operation in the world (exceeded only by the INCO plant at Sudbury, Ontario) and is the only fully fntegrated nickel plant ln the world with rnining, concentrating, smelting and refining being handled at the one site.

Over a l0-year period beginnlng in L946, the International. Nickel Company of Canada, Ltd. carried out an extensive and detailed exploration prograrn in which culminated in February I956 with the discovery of the Thornpson ore body. Previously, in I950, mineralized areas had been discovered at Mystery Lake and Moak Lake in the same area but the ores were not of sufftciently high grade to rnake rnining practicable. The Thornpson ore body, about Z0 miles southwest of Moak Lake, warranted full-scale developrnent, however, and in December I956 tt'te Company decided to proceed without delay.

First supplies were hauled to the site by tractor train over a winter road frorn on the Hudson BayRailway (mile L84.3 frorn ) during the early rnonths of. 1957. By Octob er 1957, a 30.7 mile railway spur had been constructed frorn Sipiwesk (mile I99.61 enabling large quantities of materials and equiprnent to be rnoved in for the constructibn of the plant and townsite.

The developrnent of the Thornpson townsite, located about 2 miles north of the rnine on the south bank of the Burntwood River, a tributary of the (Figure z) has proceeded in conjunction with the construction of the plant. The location and layout of the town were planned by the Province of Manitoba Planning Commission in consultation with the International Nickel Cornpany. The town conslsts of three separate residential areas and an industrial area bullt around a central business district. A fourth residential area (Westwood Subdlvision) is presently under developrnent. Initially, the town was planned for a population of 8000 but it is expected that this will increase substantially, -z-

to posslbly 10r 000 to 121000 by 1970. Shortly after developrnent began, the Province of Manitoba establlshed the Local Government District of Mystery Lake to administer the town of Thompson and the adjacent area. Development of the town has proceeded at a rapld but orderly pace and all areas are now served by sewer, water, roads, Power, schools and fire protection.

Power is supplled to the plant and townsite by the KeIsey Generating Station of the located 53 miles northeast of Thompson at Grand Rapid on the Nelson River. Thls hydro plant wae constructed especlally for the Thompson developrnent and the flrst power was available at the site ln June 1960.

The townn served by a spur line of the Railway, ls about 230 miles northeast of The Pas (or 310 mlles southwest of Churchill) and about ?00 mlles from Winnipeg by rail. An airfield was constructed at Thompson and daily flights have been serving the area slnce April 1960. A hlghway is under construction.to provlde another link with the southern part of the province. It w111connect with the Provlnce of Manitoba Hlghway No. l0 at Simonhouse, approxirnately half way between The Pas and FIin Flon.

Perennialty fr ozer. ground, rnore commonly known as permafrost, was encountered during the early stages of site development. Thornpson is located near the southern boundary of the zone of discontinuous perma- frost where isolated patches of frozen ground occur (Figure 3). Some of the more difficult engineerlng problems occur in the southern boundary region because of the sporadic and irregular distribution of perenntally frozen ground. In addition, the permafrost, which is only a few feet thick and has temperatures close to 32"I', frequently contalns a considerable quantity of moisture in the forrn of lce and rnay, upon thawing, lose rnuch of its supporting strength resulting in large settlernents and even failure of various structures erected upon it.

The development of the Thompson site, therefore, offered a unlque opportunity for the Division of Building Research to lnvestigate the occurrence of permafrost in the southern fringe atea. Brlef exploratory visits were made by members of the Division ln 1959 and detailed studies of perrnafrost and related engineering problerns were begun tn 1960.

The forrnation and existence of perrnafrost is controlled by a number of clirnatic and terrain conditions. The first phase of the studies lnitiated at Thompson, therefore, consisted prirnarily of an appraisal of those factors which appear to affect the occurrence and distribution of perennially frozen ground in this fringe area of Canadars perrnafrost -3-

region. The results of these studies of cllrnatic and terraln features, lncluding alr temperature, precipitatlon, snow cover, vegetation, relief, drainage and soils are presented in this report. Permafrost, a thermal conditlon of the ground, is deflned exclusively on a temperature basis. The measurement of ground ternperatures, therefore, formed part of the initial investigations; a preliminary assessment of the local ground thermal regirne is also included.

II. DESCRIPTION OF AREA

A. Climate

Thompsonrs location in north-central Manitoba places lt in an lnterior contlnental position in North America (Figure 4). Despite the proximlty of Hudson Bay, 250 miles to the east, this large body of water has llttle effect on the climate of the Thompson area because of the prevalling west to east circulation of air masses and disturbances. As a result, the climate is essentially contlnental ln character with long cold winters and short warm sumrrers. Because of the lack. of major relief forms between Hudson Bay and the Cordlllera, the factors affectlng the climate of Thompson prevail throughout the Prairle Provinces with variations caused prlmarily by latitude.

I. Meteorology lL, Z,3l

The large land area west of Hudson Bay is the source of cold polar continental air masses. In winter, these air rnasses are very cold and dry being protected by the Cordillera from modiflcation by mtlj, moist, Pacific polar maritime air rnasses. Preclpitation ls limited because of low alr temperatures which inhibit the presence of rnuch water vapour in the air plus the presence over the interior of the continent of a cold anticyclone wlth subsiding air. Outbreaks of cold polar air often produce severe cold waves (bLizzards) accompanied by snow showers and strong winds. They are preceded by a rapidry moving cold front in the rear of a deep cyclone moving to the northeast. \4rhen the cyclones cross the middle portion of the continent from west to east, the real polar continental air does not penetrate very far south. occasionally, pacific polar maritirne ai'r crosses the Cordillera and penetrates as far east as the Thompson area, producing Chinook winds with relatively mild ternperatures.

In summer, warrn continental air presists to the south whereas polar continental air masses prevail most of the time in the Thompson area and westward. The lower layers of these air masses becorne -4-

somewhat warmed by contact wlth the ground produclng warm dry weather. There is always abundant cooler alr aloft which has a tendency to settle earthward producing lower than average temperatureg and cl.ear skiee. Frequently there are cool outbreaks ln the rear of eastward moving cyclones. These cool invasions result in mean summer temperatures considerably less than the average extrerne maximum. Pronounced diurnal temperature variations occur in surnrner. Maxi.murn precipitation occurs during the surnmer from frontal and convective sources.

Z. Climatic tvpe

The clirnatlc zone in which Thornpson is located has been deflned ln varlous ways by different authors. Generally, all of thern attribute sirnilar characteristics to the zonez interior continental positlon with long cold winters, short warrn sumrners and rrr'axlmum preclpitation in sumrner.

KUppen defines the climatic zone as Dfc with a tendency to Dfwc (2). The symbol rrDrr denotes a cool snow forest clirnate with the mean air ternperature of the cordest month below 26.6"8. Thls temperature is the highest at which snow can persist on the ground for an aPpreclable period during the winter season. The symbol |tfrt denotes the absence of a dry season - the total precipitatlon of the driest month exceeds one tenth the total precipitation of the wettest month, The syrnbol Itwtr denotes maxlmum precipitation ln surnfi)er. The symbol rrclt denotes a relatively cool summer with fewer than four months having a mean alr temperature over 50'F. Throughout the world, the distrlbution of Dc cllrnates is approxirnately coincident wlth the distribution of permafrost; these clirnatic regions are the source regions of polar continental air rnasses. Thompson is located in the south-central portion of the Dfc region in Canada.

Haurwltz and Austin (2) place Thompson ln the Great plains climatic region which includes the whole interior of North Arnerlca west of Hudson Bay and the Great Lakes extending frorn the southern United States to the southern Mackenzie District. The clirnate of the whole region is controlled by polar continental air rnasses with differences in air ternperature being caused prirnarily by latitude.

InrrThe Climate of Canada,tt (l) Thompson is located in the northern or subarctic clirnatic region. Bordered on the north by the arctic tundra, this region consists of a broad band extending frorn the interior northwest, through the area south of Hudson Bay to euebec (lncluding most of this province) and . The region has appreciable snow cover lasting for rnore than half of the year. Extreneely tow air -5-

temperatures occur every winter throughout most of the northwest section and high temperatures may occur in sumrner. Precipitation is light in the northwest; in fact this section is sub-humid but there is ample moisture east of Hudson B"y.

Putnam (3) places Thornpson ln the southeast corner of the Boreal Interior climatic region which has slightly less than 5 months with air temperatures exceeding 43"tr' - the lower lirnlt for vegetatlve growth.

3. Air temperature

' Air temperature observations were begun in 1957 by the Inter- national Nickel Company of Ganada (Figure 5). The nearest Department of Transport meteorological stations are located at and Gillarn where observations have been taken since 1944 and 1943, respectively. Both of these settlernents are situated on the Hudson Bay Railway, the forrner about ?0 rniles southwest of Thompson and the latter about 125 rniles to the northeast. The elevations of the settlements above sea level are: \4rabowden - 786 ft, Thompson - about 7OO ft, Gillam - 454 ft.

Although these three settlements are fairly close together and at approximately similar elevations, the slight differences in latitude are sufficient to give Gillarn the lowest mean monthly and annual air ternper - atures and Wabowden the highest, with the means for Thornpson lying between the two. It is posslble therefore to obtain a reasonably valid picture of '\fabowden the climate at Thompson by using data frorn and Gillarn. Examination of the ternperature records gives the following inforrnation:

Wabowden Thompson Glllam \r944-r961) (r943-196r)

Mean January daily ternperature -10.z"r' -13.3"F -14.3"F Mean January daily minimum -18.7'tr' -23.0'F -zz,g" E temperature Mean January daily maximum - 1.70r' - 3.6"F - 5.7"tr' temper atur e

Mean July daity temperature +62.4"F +60.3"F +59.4" E Mean July daily rnaximurn temperature +73.3"F +71.4"F +70.9'tr' Mean July daily minirnum temperature +51.5.F +49. Z'I' +47.8'tr.

Mean annual ternperature +27.6"F +24.9"8 +23.l'F Mean annual daily maximum +37.Z"E +35.7"F +33.0"tr' temperature Mean annual daily minimum +18.0'3. +14.0"F +13.z'F ternperatur e -6 -

Although ternperature observations have been taken for a longer tirne at Wabowden and Gillam than at Thornpson, examination of the records indicate that the rnonthly and annual air ternperatures at Wabowden are approximately 4to 4.5"F higher than at Glllarn with air temperatures at Thompson lying between the two (Table I (a) ).

Air temperature records are used to cornpute freezing and thawing indices that give an indication of the ameunt of heat added to or extracted frorn the ground at a locality. The freezing lndex (Figure 5) ls the yearly surn of the difference between 32" F and the daily rnean temperature of the days with means below 32"F. The thawlng index (Figure 7) is the yearly surrr of the differences betweer. 32" F and the daily rnean temperature of the days with rneans above 32"F. Air temperature records (1958 to l96l) taken by the International Nlckel Cornpany at Thornpson give an average freezing index of.5535 degree days and an average thawing index of 3149 degree days. Both these values lie between the indices for Wabowden and Gillam - freezine indices, 4872 and 5815 degree days respectively; thawing indices, 3553 and z85o respectively (9 -year averages).

At Thompson, the average frost-free period each surnrner is about 80 days, frorn 15 June to early september. During most of the days in June, JuIy, August and the first half of September, the air temperature remains above freezing, giving an average total of about I l3 days without frost (4 year s of records). on the average, however, only 80 of these would occur without a break.

4. Pr ecipitation

Preclpitation observations were begun in l95Z by the International Nickel Company of Canada. Because the totals are the averages of only 4 years of observations, they are not as reliable as averages for Wabowden and Glllam. Nevertheless, a general cornparison is possible. The average total of 16. 64in. cornpares closely with mean totals for wabowden and Gillam whose totals are 17.93 and 16.44 ir.. respectively. of these, 13.37 in. fall as raln, and 45.6 in. fall as snow at Wabowden and ll.4l in. fall as rain and 50.3 in. fall as snow at Glllarn. Rain has never been recorded in December, January or February and is rare in Novernber and March. Snow has fallen in all months of the year except July and August at Wabowden and Juty at Gillarn but the surrmer months are norrrtally free from snow. The higher snowfall at Glllarn is reflected in the higher average depth of snow on the ground each rnonth durlng the snow cover period. snowfall measurements were begun at Thompson in I961. Monthly precipitation totals at Wabowden (1944-61}, Thompson (1958-5I) and Gillam (r943-61) are presented in Table r. -7 -

5. Summary

Although the Departrnent of Transport does not have a meteorologlcal station at Thornpson, air ternperature and preclpitation observatlons have been recorded by the International Nlckel Company of Canada since 1957. This observatlon period ls rather short but cornputed averages reveal that the air ternperature values lie between those 'Wabowden of and Glllam and the precipitation value.s are approximately the same for the three localities.

A hythergraph provides a convenient rnethod of showing the general character of the climate of a station. This polygonal figure cornbines the air temperature and precipitd.tion on one graph frorn which a aurTtmary staternent of the climate and comparlsons with other stations can be made. Hythergraphs for wabowden, Thompson and Glllam, whlch are presented in Figure 8, show that the cllmates of the thrbe settlements are sirnilar. The continental character of the clirnate is borne out by the large difference between summer and winter air temperatures coupled with the occurrence of most of the precipitation during the summer.

B. Geology (4)

Thompson is located in the Precambrian Shield - the largest and oldest geological region of Canada. After its formation during the Precambrian Era, rnuch of the Shield underwent marine subrnergence during the Palaeozoic Era and Cretaceous period. Following uplift ln late Tertlary tirne, extensive lce sheets advanced over most of the Shield during the Pleistocene Epoch. As they retreated, Iarge areas were inundated by glacial lakes which subsequently drained leaving the land in more or less its present form.

l. Bedrock geologv

The Precambrian Era, consisting of the Archaean and Proterozoic sub-eras, included the first three-quarters of the earthrs geological history. During this long period, sedimentary and igneous rocks were deposited and repeatedly subjected to a cornplex series of rnetamorphic, orogenic and erosional processes. As a result, the now consists predorninantly of granite and granitoid gneiss with remnants of sedimentary and volcanic rocks.

In Manitoba the rocks of the Shield are predominantly igneous and metamorphic. In recent years, geologists have divided the Shield rtprovincest into several sections or having distinct t1ryes of rocks, structures and mineral deposits. The boundary between two of the -8 -

provinces, the Churchill and the Superior, extends in a northeasterly direction across northern Manltoba lying parallel and adjacent to the Nelson River (Figure 9), In the Superior province, which lles south of this boundary, bands of volcanic rocks with intercalcated sedirnentary forrnatlons strike east-west. North of the boundary, the rocks of the Churchill province, which strike generally northeast, are mostly sedimentary with sorne volcanics. J. T. Wilson (5) and Lowdon (6) have shown that the age of the rocks in these two.prowinces differ markedly. Dating techniques indicate that the Superior granitic rocks consolidated about Z40O to 270Q rnillion years ago whereas those of the Churchill region are 1650 to 1850 million years old.

The boundary separating the Superior and Churchill provincee consists of a 50-rnile wide zone of gneissic rocks dipptng steeply to the southeast. The nickel ores of the Thompson-Moak belt tie in an intensively deformed portion of the northwest side of this broad zone. H. D. B. Wllson and W. C. Brisbin (7) postulate that ftthe general structure of the Thornpson- Moak Lake nickel belt is the remnant root of a Precarnbrian mountaln range of the island arc or alpine type that extended as a great arc or double arc rnore than 500 rniles long stretching from near Hudson Bay to the u. s. border. I' The age of the Nelson River gneisslc zone is not yet known.

During the Palaeozoic Era, much of the Shleld, particularly the margins, was covered by the sea.' The sediments that were deposlted on the Precambrian surface have been rernoulded in part by subsequent erosion. There ls no evidence of rnarine submergence in Mesozolc or Tertiary times except the Cretaceous". In late Tertiary time, renewed strearn erosion shaped hills and valleys as the surface was uplifted.

East of the Thornpson area, the Shield is flanked by the Hudson Bay Lowland, a low, flat area of post-glacial marlne sediments overlying alrnost flat-lying strata, mostly of Palaeozoic age - the oldest rocks being ordovician. In the northwest portion of the Lowland, the main body of Ordoviciair limestone outcrops along the Nelson Rlver east of Gillarn on the Hudson Bay Railway. Detailed lnformation on the post- Precarnbrian geology of thls particular section of the Lowland is limited.

West of the Thompson area, the Shietd is flanked by the Interlor Plains which consist mainly of Palaeozoic and younger sedirnentary rocks. The igneous and rnetamorphic rocks of the Precarnbrian slope gently to the west and southwest forming the basernent for the rocks of the Plains. The edge of the Plains either merges lmperceptibly into the Shield or the boundary is rnarked by a sudden drop of a few score feet or less frorn the low hilly shield country to the nearly level plains on the west. Ordovician and Sllurian formations are e>cposed along the eastern border -9 -

of the Plalns and outcrops occur in the area between The pas and a point about 50 miles southwest of Wabowden on the Hudson Bay Railway.

Z. Pleistocene Epoch

During the Pleistocene Epoch, great lce sheets covered most of the Shield and the remainder of the country. They rounded hills, deepened valleys and deposited drift as they advanced and as they retreated deposited a variety of coarse- and fine-grained materials. Throughout Canada, by far the greatest portion of the gnconsolidated deposits overlying the bedrock resulted from the glacial activity of this geological period. Of the four major periods of glacial advance and retreat on a continental scale which are known to have occurred during the pleistocene, the most recent and the one rnost easily studied in Canada is the Wisconsin. At the peak of thls advance, all of Manitoba was covered by lce. The recession of this last major ice sheet began about 20,000 ydars ago but was interrupted by significant re-advances of the lce front ln some areas. It is believed that the ice sheet retreated finally to near Hudson Bay where It dissipated about 5000 years ago.

The slngle large ice sheet which covered all of Canada east of the Rocky Mountains began apparently as several separate rnagses of ice whlch migrated because of climatic conditlons and eventually coalesced to form one continuous expanse. The inland portion of this continental glacler ls known as the Laurentide ice sheet. Evidence that the ice sheet was perhaps as thick as I0r 00o ft is shown by known land subsidence of several hundred feet caused by the weight of the ice and by the occurrence of Shield erratics at altitudes exceeding 5000 ft in the Rocky Mountains. It is generally believed that the Laurentide lce sheet retreated subsequently to two main areas, narnely the rrKeewatlntl rrlabradorrrlce and Centres, one on either side of Hudson B"y. Thls is lndicated by the pattern of ice-flow features, eskers and moraines in the interior parts of Canada. The advance of the ice across Manitoba was extremely complex and is not fully understood but appears to have been generally in'a southwest to west direction (Figure r0)" In the Thornpson area it apparently advanced rnainly in a westward direction. The retreat of the ice from Manitoba was also complexbeing marked by halts and minor re-advances of ice lobes, but appears to have been generally to the northwest, north and northeast.

As the ice retreated, lakes of melt-water formed at its rnargin. Glaclal Lake Agassiz, perhaps the rargest of all these lakes in canada, covered rnost of central and for thousands of years. It began in the upper south of the International Boundary and e>cpanded northward into Manitoba and northeastward into northwestern ontario following the retreating ice front. At one time, when the ice -10-

margin stood apparently at about latitude 50'N, the lake was at its highest leve1 - 1250 ft above present sea level. The lake level dropped as it followed the ice retreating northward in the Lake Winnipeg basin.

The history of the forrnation and existence of Glacial Lake Agassiz ls somewhat obscure particularly in the northernrnost portion. A number of theories have been proposed, the first being upharnrs ln I895 and the latest being Elsonts,in 195?. A brief surnmary of the lake history as suggested by Elson (8,9), who has evaluated the most recent findings, is given in the following paragraphs. He postulates that two Agassiz Lakes (I and II)were formed, separated by an interval durlng whlch the basin was nearly completely drained.

As the Laurentide ice sheet retreated lntermittently northward, glacial melt-water formed Lake Agassiz I whlch discharged. southward through Lake Traverse, Minnesota. The lake level was lowered in this rnanner until further deepening of this outlet was retarded by bedrock. As the ice front receded northward, an eastern outlet opened into the Lake Superior basin allowing further lowering of the lake. A major re-advance of the ice front blocked the eastern outlet allowing Lake Agassiz I to erode its southern outlet further. Imrnediately after the retreat of the ice, eastern outlets were opened again which caused complete or nearly complete drainage of Lake Agasslz I. Alluvlurn was deposlted ln the abandoned southern outlet and erosion of the lake bottorn sedirnents occurred while the lalse basin was dry (about I0r000 years ago - Two Creeks period). Re-advancing lce (Valders) possibly combined wlth crustal uplift, blocked the eastern outlets and caused the formation of Lake Agassiz II. The lake level rose until lt subrnerged and subsequently swept away the alluvium blocking the southern outlet. The lce margln then extended from west of Lake Nipigon north to the Sachlgo moraine on the Manitoba - northwestern Ontario border, west to The Pas moraine and northwest to the Cree Lake moraine ln northern saskatchewan. Discharge of Lake Agassiz II to the south into the Mississippi and Minnesota River systerns, occurred about 9000 to 8000 years ago. East

The absence or scarcity of field observatrons limrts the knowledge of the northern and eastern boundaries of Lake Agassiz. - lI -

The approximate northern extent of the lake is inferred from reports of larninated (varved) silt and clay deposits occurring in several extenslve belts and nurnerous small basins. Although end rnoraines and ground moraine consisting of a sandy till of precambrian origin are known, there is a general lack of shore features, beaches, terraces, and other features because the ice front generally formed the northern margin of the lake. In addltion, wave erosion probably was harnpered greatly by the numerous rocky hills and knolls of the Shield forming islands and archipelagos in the northern reaches of the lake and by substantial seasonal fluctuations in the lake water level.

In the Thornpson area, surficial deposits of stratified lake sediments and till cover the Precambrian bedrock. The dlrectlon of glaclal movernent and the type of underlying bedrock generally determine the characteristics of till whereas lake-deposited rnaterial ls derived frorn lce margins sorne distance'away and differs from the till in composition. A rnajor end moraine is shown on the Glacial Map of Canada north of the . The lithology of this rnoraine systern, called the Burntwood-Etawney, ls unknown. It separates west-trending striations on the east from the southwest striations on the west, the latter apparently representing an earlier ice rnovernent. The large htrls just north of the Thompson townsite and the Burntwood River (from which gravel is presently obtained) are part of this systern.

The varved clays in the northern area were deposited in Lake Agassiz II and it is believed that the ice front may have stood for a long period just east of the Nelson River valley in an irregular llne just lying north of the Churchill River.valley and easterly to the Southern Indlan Lake. The deposits are extensive and continuous - along the Hudson Bay Railway, they occur for about lo0 miles from about mile I30, near the south end of Setting Lake, to the first crossing of the Nelson River (rnile z4r). The distinctly stratified crays rest on bedrock, till or thinly stratified drift deposits overlying the till. The deposltlon of these rnaterials on the hitly and knobby Shield relief has produced an alrnost flat to gently rolling plateaulike surface, the clays varying in thickness frorn about l0 to 50 ft. Boulders and erratics are extrernely rare in varved clays but they have been found in a few rocations. Three have been uncovered by excavation at Thornpson and one was reported by Hardy and Legget (10) at Steep Rock, Ontario, The calcareous content of the clays may provide a clue to their origin. Mclnnes (ll) noted tn I9l3 that the clays along the Burntwood River are highly calcareous while in the valley of the Grass River they tend to be only sllghtly calcareous. He suggests that the more northerly sedirnents were derived predorninantly from the limestones of the Hudson Bay Lowland and those deptsited in the southern portlon of the area exist as a result of the glacilr passing over Precarnbrian rocks. clay sarnples from the wintering Lake area -IZ-

collected by J. F. Wright (I2) were found also to have a high carbonate of lirne content.

Since the close of the Pleistocene Epoch, no changes, sirnilar in magnitude to those caused by the ice sheets, have occurred in the landscape. Elastic rebound of the land surface ls still continuing following the retreat of the ice. The pre-glacial drainage, which was altered radically by the ice, has not yet adjusted.itself to the new conditions as indicated by the disorgar,ized pattern of lakes and strearns. Peat accurnulations of varying thickness cover vast areas. The chlef processes affecting the landscape at present are stream erosion and deposition, weathering and frost action.

I I I. TERRAIN OBSERVATIONS

The terrain of an area ls cornposed of a number of surface and subsurface features, the cornbination of which gives the area its unique character. The terrain features, which can be considered on two scales of magnitude, include relief, drainage, snow cover, vegetation and soils. On the macro-scale, the Thornpson area is located in north- central Manitoba and the terrain is typical of that exlsting throughout this part of the province. On the rnicro-scale, there are signiflcant variations in the terrain features within the Thornpson townsite whlch contribute to variations in permafrost distribution. The rnacro- and micro-aspects of each terrain feature are described in the following sections.

A. Relief

Thompson ls located in the plateau land, which covers an area of about I0r 000 square rniles, extending from the vailey of the Nelson River westward to near Burntwood and Wekusko Lakes (99" 45, W) and northward to beyond latitude 56"N (3). This area was covered by glaclal Lake Agasslz and the consequent deposition of lacustrine varved clays has had the effect of levelling the forrnerly irregular and rolling Precambrlan surface. The lacustrine deposits are shallow on the rocky uplands and deeper ln the valleys (I3)"

The townsite of Thompson ls situated beside the Burntwood River which has a rnean water elevatlon of about 600 ft above sea level at this point. The macro-relief is flat to gently undulating with elevations varying frorn about 650 to 700 ft above see. level (Figure Il). Immediately east of the town there is a sharp ris-e in elevatioh to 725 ft above sea level. North of the Burntwood River, several hllls rise rnore than l0O ft above the level of the townsite (Figur e lZl. - 13 -

The flat to gently undulating relief of the townsite is interrupted by several northward-trending gullies tributary to the Burntwood River. The average distance between gullles is about I000 ft. Most of thern are only about r0o0 ft in length and the difference in elevation between their sources and the river ranges frorn 5C to 7S f.t. Three of the gullies cut back into the townsite for a distance of about 2000 to 5000 ft. Along the first thousand feet frorn their mouths, gradients are similar to those of the shorter gullies, but towards the sources, gradients becorne rrrore gradual.

At the heads of these gullies, there are poorly drained elongated areas extending for distances of several thousand feet. These flat slightly depressed expanses are interspersed with slightly elevated well-drained areas to provide srnall but signiflcant variations in elevation and micro-relief throughout the townsite.

The rrlowrr major boundaries between the "hightt and areas have been delineated by stereoscopic exarnination and have been rnarked on an air photo of the Thompson area (Figure 23). The location and extent of the poorly drained areas are clearly evident. They occur in three roughly parallel groups having generally a northeast-southwest orientation. The two largest areas cornprising the middle group are each about 5000 ft long by z0oo ft wide extending through the centre of the townsite. The northerly one lies at an elevation of 670 ft and the southerly one at 690 ft. The second group, consisting of four separate areas extends across the northwest portion of the townsite. The two largest of these areas' one at each end of this group, are each about 2000 ft long by 1000 ft wide. The northeast area lies at an elevation of 660 f.t and the area ln the southwest at 685 ft. The third and srnallest group extends along the east margin of the townsite. The largest area in this group is about 3000 ft long by 500 ft wide, at an elevation of 6g0 ft.

These poorly drained areas are actually not absolutely flat or uniform in character. Each consists of a large nurnber of small flat depressions of various shapes and are several hundred feet in diameter, solne containing pools of water. Interspersed with these depressions are nurrrerous ltislands, rr small several hundred feet in diarneter, which rlse a few feet above the general revel of the poorly drained expanses.

B. Drainage

Although the relief throughout the Thompson townsite is subdued and differences in elevation are srnall, there are variations in drainage conditions and the existence of water associated with the relief and other terrain features. This situation is characteristic of the -14-

extensive rolling plateau in north-central Manitoba in which Thompson is situated. Drainage is generally fair but over considerable areas of its central portion, sorne distance'frorrr the valleys of larger streams, there are Larger tracts that have insufficient gradients for the proper flow of surface water.

A considerable portion of the surface water on the flat to undulating Thornpson townsite drains through the.north trending gullies into the Burntwood River (Figure 13). These gullies contain srnall rivulets whlch flow throughout the sumrner. It is reported that the water in the rnost westerly of the three rnajor gullies rises gradually in the spring, as the snow rnelts, to a level of I to Z ft above the normal srlrrrlrrer flow and then gradually subsides. Sirnilar conditions apparently prevail in the other gullies.

The relatively elevated areas, situated between the gullies and around the slightly depressed flat areas, are generally well to excessively drained. No standing water has been observed in these areas and the upper layers of soil are dry. Surface and subsurface drainage in the low flat areas is poor and srnall ponds are prevalent. The largest boggy areas, some of them several hundred feet in diameter, occur in the two large poorly drained tracts extending through the centre of the townsite. Similar drainage conditions prevail throughout the other poorly drained tracts (Figure l4). Besides the ponds, srnall hollows a few feet ln diarneter, which are either rnoist or contain water, are prevalent throughout the hummocky sphagnum rnoss-covered areas around the bogs (Figure l5). The sloping areas between the higher well-drained areas and lower poorly drained areas are mo.derately drained.

C. Snow Cover

No regular detailed observations of snow depth or variability of snow cover have been made in the Thompson townsite. An estirnate of the snowfall can be obtained, however, by examining the records of Wabowden and Gillam. The annual snowfall ranges between 45 and 50 ln. (Table I(d) ). The rnaxirnum accurnulation of snow on the ground appears to occur in February and averages about ZZ in.

A few scattered snow depth observations were made during February 1962. The winter of 196I-62 was considered by local residents to be rather exceptional because the snowfall was heavier than usual. The depth of snow in undisturbed areas, i. e. with vegetation cover, was checked at several locations and was found to vary frorn 30 to 36 in., averaging about 32 in. There was no distinct difference in snow depth between heavily wooded locations and areas with sparse vegetation - 15 -

cover (Figures I5, l?). The snow catch ln the trees that are predominantly coniferous, varied considerably frorrr very little where the cover was sparse, to as much as IZ in. on sorne limbs where the growth was quite dense (trre average distance between trees was z to 4ftl . The total amount of snow retained in the trees, however, is negligible cornpared with that on the ground.

D. Vegetation

l. General description

Thornpson is situated in the taiga or boreal forest region which extends east-west across Canada ln a band several hundred miles wide. This vegetation zone has been described byseveral authors but generally all of thern attribute sirnilar characteristics to it. In their vegetation classlfications of canada, D. F. Putna'n (3) and J. s. Rowe (13) provide adequate descriptions that apply to the Thornpson townslte.

According to Putnarn, Thompson is situated in'the northern Coniferous zone which has few broad-leafed trees. The dominant species are white spruce (Picea glauca), balsam fir (Abies balsamea), black spruce (Picea mariana), Iarch or tamarack (Larix laricina), jackpine (Pinus banksiana) and white birch (Betula papyrifera). The trees are mostly srnall and the forest is scrubby. Black spruce and tarnarack predorninate in wet and swarnpy areas and there are also large areas of open bog or rnuskeg. The forest is of little econornic significance except as a habltat for garne and fur -bearing animals.

In Rowers classification, Thornpson is situated in the northern part of the Nelson River section of the Boreal Forest region. This section includes a strip of land lying along the east shore of Lake winnipeg and northward, the clay zone surrounding the upper NeIson River in central Manltoba. It is bounded on the west by the lakes of the palaeozoic Lowlands and on the east and north by abundant Precarnbrian rock outcrops. The northern boundary is rnarked also by a gradual change frorn the southern closed forest to the open subarctic forest within 50 rniles north of Thompson. Stands of black spruce constitute a large part of the forest cover but the proxirnity to nurnerous and extensive swan-ps that lie back from the rivers is reflected in a restriction of growth. Where drainage is better, as along the sides of rivers, on islands, or on row ridges, good stands of white spruce (Picea glauca) with some balsam poplar (Populus balsarnifera), white birch (Betula papyrifera), aspen (Populus trernuloides) and balsam fir (Abies balsamea) are custornary. Extensive and repeated fires have fragrnented all the forest cover, however, and large areas support small aspen, white birch, and scattered white and btack spruce, or jackpine - 15 -

(Pinus banksiana) and aspen. Tarnarack (Larix laricina) and black spruce are present in the swamps.

Variations in the vegetation throughout the Thornpson townsite are related primarily to elevation and relief, drainage and soil conditions. Basically, two fairly distinct associations of vegetation with accornpanying micro-relief and drainage characteristics are evident. The first association occurs on the relatively higher areas.between the gullies, and the second occurs on the lower flat areas at the heads of the gullies. Their distribution coincides roughly with the well-drained and poorly drained areas respectively, which have been described ln the previous sections dealing with relief and drainage. Between these two types of areas are transition zones of varying widths in which the vegetation changes frorn the high area t1rye to the low area t)rpe. Differences in elevation between high and low areas are mostly of the order of only a few feet.

The vegetation association, on the htgh areas, consists of white and black spruce, jackpine, birch, poplar and alder with sorne scattered tarnarack (Figure lB). The rnaxirnurn height of the spruce, jackpine, birch and poplar varies frorn 50 to 60 ft and the rnaxirnum height of the alder varies frorn 6 to t0 ft. Strands of lichen hang from rrany of the spruce. Tree growth is fairly dense, the average distance between trees being about 5 to 10 ft. Ring counts of several trees chosen at randorn are listedinTabIeII.Thegroundcoverconsistsoffeathermosses "' (Hylocorniurn splendens (Hedw. ) BSG and Polytrichum cornrnune Hedw. )r Iichen (Cladonia alpestrls) and grass. The moss predorninates, frequently forrning a continuous carpet either flat or hummocky over large areas, and averages frorn Z to 4 in. in thickness. Occasionally these rnosses grow to 7 in. in thickness.

The vegetation association on the low areas (Ftgure l9) consists of treeless or sparsely wooded swarnpy and boggy areas, inter- spersed with slightly elevated round or elongated dense spruce rrislandsrr several hundred feet in size. The vegetation in the open areas consists of scattered spindly spruce and occasional tamarack Z0 to 30 ft apart, growing to a rnaximurn height of about Z0 f.t. Strands of ltchen hang frorn rrany of the spruce. Ring counts of various trees chosen at random are listed in Table II. Surface vegetation consists of hummocky sphagnurn moss (Sphagnum fuscurn (Schirnp. ) I0inggr. and Sphagnurn recurvum P. -Beauv. ) as thick as Z ft, Labrador tea, sedges (Carex chordorrhiza Ehrh., Carex aqualitis Wahlenb., and Carex restrata) and grass. Tree

*' All ground plants were identified by the Natlonal Herbarium, Department of Northern Affairs and National Resources, Ottawa. -r7 -

growth on the spruce rrislandsrr is very dense, averaging I to Z ft apart, with a maximum height of about 25 to 30 ft. The ground cover consists of humrnocky sphagnurn rnoss, similar in thickness to the tlpe rnentioned previously.

In the transition zones occurring between the high and low areas, the vegetation changes frorn the first association type to the second (Figure 20). These zones vary in width from a few feet to several hundred feet, Sorne of these transition zones cornprise the sides of gullies. On the broad transition zones, the slope is almost irnperceptible and the change in vegetation is gradual. Towards the low areas, the trees become increasingly stunted and such specles as jackpine, birch and poplar, requiring well-drained conditions, give way to black spruce. The ground cover of thin feather rnosses (Figure 2l) and lichens gives way to sphagnurn which becor,nes thicker and more hummocky towards the low areas (Figure 22). On the narrow transition zones, including those around the spruce rrislandsrr in the low areas, the transition ls rather abrupt with a drop in elevation of about 5 ft aceornpanied by a similar abrupt change ln vegetation.

Z. Air photo patterns

The two principal vegetatlon associations have distlnctly different textural and tonal patterns on aerial photographs and can be easily identified and delineated. These patterns are shown on the aerial photograph of the Thompson area (Ftgure 23).

The vegetation association growirtg on the high area presents a fairly uniform but grainy rnedium to dark grey tonal pattern on the aerial photograph. These areas occur on the |tinterfluvesrrbetween stream gullies extending over most of the west half of the townsite and in a strip along the east rnargin parallel to the town lirnit. The fairly dark tone is caused by the predominance of spruce and jackpine, which are conifers with dark green needles. Scattered, slightly lighter blotches coincide with a higher proportion of birch and poplar, which are deciduous with light green leaves, although the conifers are still predorninant. Particularly light grainy areas within this association are evident in the northwest corner of the townsite and to a lesser extent in the centre. These appear to be areas in which birch and poplar predorninate with few conifers. The average distance between trees ls greater than in other high areas and the rnore exposed ground cover consists predominantly of lichen, grass and other light-coloured vegetation with a little moss which is a darker green.

The vegetation association growing in the low areas presents a dlstinctly blotchy pattern consisting mainly of medium to light grey with scattered patches of dark grey tones. These areas occur at the head waters - l8 -

of the streams in the three northeast-southwest oriented bands extending through the townsite. The most predominant band varies in width from several hundred to about 2000 ft extending through the east-central portion of the townsite. The other two bands consist of smaller scattered areas on either slde of the predominating central band. The lightest aknost white areas are sedge and grass covered bogs, sorne containing pools of water. The dark grey areas, which are the darkest of all the patterns on the aerial photograph, are the spruce rrislands. rr Between the lightest areas and the darkest areas, the tone is determined by the proportion of dark-coloured vegetation - spruce, jackplne, rrross- and light-coloured vegetation - treeless sedge and grass areas.

Generally, the low areas are lighter in tone and more varied in texture than the high areas. This is caused prirnarily by the variety of plant groups within the low area associatlon in contrast to the fairly uniforrn predominance of spruce and jackpine ln the high area as sociation.

E. Soils

During the past five years, several agencles and firms have carried out subsurface investigations at various locations in the townsite and adjacent areas to deterrnine soil and foundation condltlons. During the course of this work sorne 300 test holes were bored, the majority less than 20 ft deep with sorne Z0 to 30 ft and a few to 75 ft. Several hundred more holes have been bored to depths of l5 to ZO ft to deterrnine the occurrence of perrnafrost. The results of rnuch of this exploratory work have been rnade available to the authors who have extracted pertinent inforrnation for inclusion in this report. In addition, the authors have carried out exploratory work, primarily in the Westwood subdivision, and information obtained frorn boreholes and examination of the soils in serwice line trenches, excavated to as deep as 30 ft,is also included.

The predominant soils of the Thompson area are stone-free (except as noted below) lacustrine varved rrclaysrrcornposed of the rock floor once held in suspension by glacial streams and deposited by thern as they reached the waters of glacial Lake Agassiz. The well-stratified trclaysrl occur as brown and grey deposits, the grey varved materials underlying the brown. These deposits overlie bedrock or thinly stratified glacial drift. The drift is cornposed predorninantly of a fine sandy gravel or a fine sand. A typical soil profile is shown in Figur e 24. A detailed account of the soils is given in the following sections.

The occurrence of three boulders has been reported during the excavation of service line trenches at Thompson. The locations and - 19 -

descriptions of two of these are noted on Figure 34. The third boulder was of sirnilar size (about 2 by Z by 3 ft) but its exact location in the older section of the townsite is not known.

l. Soil pr ofile

(a) Surface deposits

The following description applies to the area prlor to disturbance by construction activities.

There are no soil e>rposures within the Thompson townsite, as the whole area is covered with an organic mantle which varies considerably in thickness between the high and low areas. On the higher ridges the organic cover consists of forest litter a few inches thick only under which the mineral soil is dry and firrn. tn itte lower boggy areas, organic material, consisting of a living rrross cover over decomposed rnatter, can be 5 ft or rrrore in thickness overlying the wet clay. In the transition zone between the high and low areas, the organic cover can vary appreciably within a relatively short dlstance, being only a few inches thick on the higher ground and Z to 3 ft thick on the lower s ections.

Immediately below the surface organic mantle, a dark, chocolate brown clay is usually encountered. This layer, which is not bedded or varved, ranges in thickness frorn 6 in. to 4 or 5 ft and overlies a brown varved clay. On sorne of the higher ridges, however, a light buff-coloured clay is f6und at the surface. Extrerne distortion of the uPper 2 to 3 ft of the varved material has been observed to occur locally in the area and the dark brown clay has been deposited on the very irregular surface. The upper boundary of the dark brown clay layer generally conforms to the present ground surface.

(b) Brown varved clay

lrnmediately below the organic cover or the dark brown clayey soil lies a brown varved clay consisting of light- and dark-coloured strata. There is no distinct boundary between the two, the upper dark brown layer rnerging into the lower brown varved soil within several inches. The thickness of the brown varved rnaterial varies from 6 to t6 ft (and has been found to extend to zo ft at some locations) with no apparent relation to areal location or surface elevation although no detailed study has been rnade throughout the townsite to note correlations that rnay exist. The tight-coroured clayey silt strata appear light grey when dry but are tan-coloured when fresh. The dark strata are predorninantly clay size and are mediurn to dark brown in colour. The thickness of the -zo -

individual stratifications varies, but generally increases wlth depth. The light silty layers rarrge frorn hairllne to l/4 in. in thickness near the top of the deposit to about I to I t/+ in. at the bottom, while the dark clay layers range from t/Zto Z/+ir-. thick at the top to about 2 in. at the bottom (Flgures 25,26l. Distortion of the strata occurs locally and appears to be rrrore severe in the top of the layer although it may also occur throughout the deposit. The varves appear to retain their original thickness even where they have been severely folded.

(c) Grev varved clay

Below the brown varved material lies a grey varved soil which extends to bedrock or the drift overlying the bedrock. The brown rnerges gradually lnto the grey over a distance of I to 2 ft - the change usually being quite subtle. In sorne cases the grey clay may extend to depths greater than 75 ft although at the greater depths it becomes rnuch mdre silty. Again, the mediurn to dark grey layers consist predominantly of a clay- slzed material and the llght grey-coloured layers are a clayey silt. The thickness of the individual stratifications varies and appears to increase with depth although exceptions do occur,. The light clayey silt layers range in thickness from hairline to Z If Z in. and the dark layers range from tfZto Z in. Distortion of the grey varves has been noted at sorne Iocations.

(d) Other deposits

Although silty sandy rnaterials and a fine sandy gravel have been encountered in a few explorations, little is known abciut their distribution, thickness or properties, as they usually occur well below the depth of most investigations and are dlfficult to sarnple in rnany instances. The silty sand has been found to occur as a discontinuous, lrregularly sloped stratum, in a rnedium dense to dense condition. At the hospital site it underlies the brown varved clay at a depth of l3 ft, but this is unusual for the townsite as a whole"

Bedrock is usually found in the townsite area at depths exceeding 50 ft. It does appear close to the ground surface (Zto 3 ftl, however, ln the southeast section of the townsite where a cut was made on Mystery Lake Road for a dlstance of several hundred feet, and also near the river, west of the Westwood subdivision.

Z. Soil properties

The results of testing carried out on sarnples obtained frorn various depths and locations, prirnarily to identify and classify the soils underlying the Thornpson townsite, are described in this section. The -zr -

predominant soil and therefore the one concentrated upon is, of course, the varved clay. The theories on and the conditions necessary for the forrnation of varved deposits have been reviewed and discussed by a number of authors (I4, I5, l6); they will be noted only briefly here.

The word rrvarvedrt irnplies a distinctly banded deposit, and is usually used to refer to rnaterials deposited in a glacial lake. These rrclays, tt rrsedimentsrl materials are commonly called varved but varved is a preferable terrn because some of the bands or stratifications may contain little or no clay. Each varve consists of a dark-coloured, fine- grained layer and a light-coloured, coarser -grained layer. According tothe classical viewthe couplet so forrned is thoughtto represent I yearrs deposition. During the tirne of retreat of a glacier, suspended sediment is brought into a glacial lake by strearns running off the glacier and the surrounding land during the spring and surnrner rnelt period. The heavier, usually silt-size particles settle out first, forrning'the ltght- coloured larnination but the lighter, clay-size fraction rernains in suspension until the fall and winter periods, when it gradually settles out to form the dark Layer" The sedirnentary year is generally thought to begin with the light-coloured spring-and-surnrner layer.

Many engineering problems arise in connection with glacial lake deposited varved clays. The rernarkably different physical propertles of the individual laminations (and in sorne cases within each lamination) which make up a varve have been recognized but are not always readily deterrnined because the layers are very thin. Although most testing of the Thornpson varved clay has been carried out on cornbined or bulk samples, a limited arnount of inforrnation is available on the properties of the individual layers. An attempt is rnade in the following sections therefore to describe the physical properties of individual layers in addition to the cornbined Iayers.

(a) Grain size

Hydrometer analyses were rnade on sarnples frorn adjacent light and dark layers and on cornbined sarnples of the varved clay obtained frorn depths between 3 and 30 ft. The grain -size accurnulation curves are shown in Figure Z'7" The dark layers contain B0 to 90 per cent of particles less than 0.002 rnm effective diameter. The light layers have 23 to 29 per cent less than 0.002 rrrrn, the rernaining 70 to B0 per cent being of well-graded silt sizes, all less than 0.06 mm. The curves for four combined sarnples fall between the extrernes of the light and dark envelopes. There is no apparent relation between grain size and depth. These values agree with the wide ranges for various Agassiz deposits as surnrnari zed by Elson (9). -22 -

The possibility of variation in grain size from top to bottom of single layers was not investigated. Thus, lt cannot be stated whether - the varves are diatactic or s)trnminct.

Grain-size curves plotted on Figure 27 for four samples of silty sand taken from depths of. Z0 to 30 ft, show this rnaterial to be unlforrn and fine containing l5 to 75 per cent silt-size particles.

(b) Specific gravitv and denslties

Tests on three dark layers at depths of 10, Z0 and 30 ft frorn different locations yielded specific gravities of the partlcles of 2.82, 2.83 and 2.82. Two light layers, adjacent to two of the dark layers, had specific gravities of. ?.78 arrd 2.75.

A sarnple of dark brown clay frorn an unvarved str'aturn overlying the varved clays, with about the same grain -size composltlon as the above mentioned dark layers, had a specific gravity of.2.78, perhaps due to oxidation by weatherlng. A combined varved sarnple (68 per cent clay size), also had a specific gravity of 2.78.

es of varved clay varie,d from 84 to density of. 36 varved clay sarnples frorn ll2 to I25. Average dry deneity ed on 9 sarnples ranglng frorn

(c) Natural rnolsture contents

Results of over 1000 moisture content determlnations from about 250 locations in frozen and unfrozerL areas were anaLyzed. Sarnples were obtained from depths of I to 45 ft, but rnost of thern were between 2 and 25 ft. In sorne cases, where samples were taken frorn trench walls, thicknesses of the ice and soil layers at those sections were carefully measured. A study of this inforrnation lndicated that; (1) The soil is saturated (or 98 to 99 per cent saturated).

)k Fraser (17) deflnes diatactic structurq of a varve as one in which the materials of the varve are sorted accordlngto size and specific gravity of particles, the coarsest at the bottom and the finest at the top. Symminct structure refers to clay deposited under control of an electrolyte in which case particles large and srnall settle together and forrn an unsorted rnass due to flocculatlon of the grains. -23 -

(Z) In the light layers of varved deposits, moisture contents range from ZO to 30 per cent, averaging ?7 per cent. In the dark layers of varved clay and in the dark unvarved clay, rnost values were between 30 and 45 per cent, averaging about 33 per cent. Moisture contents ag high as 107 per cent were reported, but such values were the result of high ice contents (water:soil ratio of nearly 3:I by volume). Generally, any rnoisture contents over about 45 per cent coincided with the high ice segregation in the sarnples. Since the soil ls. saturated, these rnoisture contents reflect the structure of the soil, which can be elcpressed as void ratio. For the light layers, then, the void ratios range from about 0.55 to 0.83, averaging 0.74 and for the darklayers, about 0.85 to I.27, averaging 0.93.

(3) The rnoisture content of the silty sand varied frorn 2l/Z to l9 per cent, averaging about l0 per cent.

(41 There ls no apparent relatlonshlp between moisture content and depth below surface, or between rnoisture content and absolute elevation, over the entire area (Figur es 28,291. Figure 30 shows only those samples which were specified as rrsilt't or I'clayrt (i. e. light or dark), plotted against depth. It suggests the boundary between moisture contents in the light and dark layers to be about 30 per cent.

At particular locations, however, moisture content was constant with depth (within I or ? per cent). This held true in unfrozen holes and in sections with ice lenses, large or small. In the two or three frozen sections examined in detail, moisture contents of samples between ice layers were Z to 4 per cent lower than average values ln unfrozer:. ar-eas.

(d) Atterberg Lirnits and Plasticity

Results of alrnost 100 Atterberg Limit tests are presented on the Plasticity Chart, Figure 31, a plot of plasticity index versus liquid limit" Unfortunately, in rnost cases the actual proportion of light soil to dark soil is unknown.

The results of Atterberg Lirnit and grain -size analyses rnade on individual layers are shown in Table III.

As might be e>cpected, the dark, clayey layers are rnuch rnore plastic than the light, silty layers. The sarnples with liquid limit greater, than 60 can be considered to come frorn dark layers and are hlghly plastlc. The samples having a liquid lirnit below about 45 carr be considered to corne from light layers, and of low plasticity (silty); those between are values for combined sarnples. -24-

The band of values, parallel to the A-Iine, coincides with the band defined by Casagrande for inorganic glacial clays from Boston, Detrolt, Chicago, and northeastern Canada. Both the light and dark deposits fall in the same band.

(.) Activity

Figure 32 Ls a plot of Plasticity Index versus clay fraction. The slope of the straight line through the origin that best fits the points ls known as the lrActivitytr of the rnaterials (18). It is a rneasure of the colloidal properties, i. e. Lf.f.ot a given clay fraction, rnaterial frorn one soil deposit is rnore plastic than that frorn some other deposlt, the former must be rnore colloidally active (since plasticlty characteristics depend upon the colloidal behaviour of the fine particles).

The Thompson varved clays have an activity of. O.'41, classifylng thern as very inactive. It should be noted that the two sarnples frorn light layers are very close to the line best fitting the cornbined and dark samples. Skempton suggests that clays having an activity less than 0. 5 are late glacial materials having a clay fraction consisting predominantly of kaolinite or containing little true clay rnineral. Apart frorn kaolin these are derived largely by mechanical erosion of non-arglllaceous rocks by ice sheets and deposited in lce-darnmed lakes.

(f) Alkali concentration

Samples taken frorn flve widely separated locations in the area were found to have water -soluble. sulphate contents of 30 to 400 parts per rnillion, indicating a very low alkali concentration.

F. Perrnafrost

The first step taken when studies at Thornpson were inltlated, was to determine the general pattern of perrnafrost distribution by rneans of a review of all available site investigation reports noting occurrences reported ln borehole logs. Several hundred logs have been exarnined. In addition, daily construction reports of the excavation of service trenches for sewer and water lines offered a valuable source of inforrnation. These were reviewed and pertinent perrnafrost data extracted. Sorne hand probings were made by the authors, prirnarily to deterrnine variatlons in the depth to perrnafrost under different vegetation, relief and drainage conditions and to substantiate information obtained frorn reports and in discussions with residents. -25 -

A11 this information is shown on Figure 33. Because of the complex distribution pattern and the lack of sufficient information, however, it has not been possible to delineate the exact boundaries of rt any of the permafrost "islands. To do so would require ver)r detailed investigations at each location.

The developrnent of the Westwood subdivision, planned in 1p61, with the actual construction of service lines beginning early it 1962, afforded an excellent opportunity to obtain detailed observations of soil and permafrost conditions and also an assessrnent of the area with regard to general terrain conditions prior to large-scale disturbance by construction. In september 1961, therefore, hand probings were made to determine variations in depth to permafrost and to attempt to delineate the areal extent of permafrost bodies. Hand auger holes were then- put down to a depth of. 25 ft at selected locations to determine subsurface ice and soil conditions, and, if possible, the thickness of the perennialLtj f.rozen ground. Thermocouple cables were fabricated and placed in several of these boreholes so that ground temperatures could be rneasured at various depths to 25 ft.

Arrangements were made with the firm of consulting engineers engaged ln the design and supervision of the construction of the services in the new Westwood subdivision to have detailed observations of perma- frost occurrence made during the excavation of the sewer and water line trenches. The vertical and horizontal extent of perennially frozerr ground encountered in the trenches was thus delineated for much of the area (Flgures 35r361. some areas (noted on Flgur e 34) have not yet been serviced and thus no informatlon is available. soil samples and detailed logs (Figures 37,39,39,401 of soil and ice conditions revealed in the trenches were obtained by the authors during the construction period.

The information presented in the following sectlons of this report, therefore, sumrnarizes aIL available data collected from a revlew of various reports and also that gathered by field observatlons by the authors up to and including October 1962. Additional information on perrnafrost occurrence will be collected as further investigations are carried out.

l. Permafrost observations in original townsite

The locations of all reported permafrost occurrences are shown on a street plan of the Thompson townsite (Flgure 33). These were plotted from information obtained frorn test-hole logs, service-line trenching reports, and excavation for or performance of building foundations. Many test-holes, in which permafrost was not found, are not shown, to avoid confusion. -26 -

These plots point out the irregularity of the areal extent of frozen ground. Along the east side of Copper Road, for example, perrnafrost was encountered for a distance of 50 ft, absent for 45 ft, then struck again for I35 ft. In the corresponding trench on the west side, only 40 ft away, there was no perrnafrost. Yet sorne of the lots on that side were found, on drilling, to be underlain by permafrost. House foundations on the east side have settled and cracked.

A sirnilar situation was found off Cree Road between Selkirk Avenue and Juniper Drive. In the storrn sewer trench on the east side of the road, frozen ground was encountered for a distance of.220 ft. Holes drilled along a parallel line onty 35 ft east showed no permafrost (represented by *ts in Figure 33). Fifty ft beyond that line, however, a perrnafrost area that extended more than 600 ft eastward was encountered. In one of the holes, layers of ice, up to 6 in. thick, were found between 8 and ZZ ft, while in a hole 100 ft away, the ice layers were ho thicker than I /Z in., between the 6- and 13-ft depths.

Irregularities on a much smaller scale also occurred. About 400 f.t west of the Station Road-Nelson Road intersection, for example, holes were drilled l5 to Z0 f.t apart around the perimeter of a proposed building 72by 80 ft. Perrnafrost was found on three sides of the buildlng, in 7 of the l6 holes, but holes at all four corners and along the west side were unfrozen.

Another exarnple of the erratic nature of perrnafrost distribution on a srrlall scale is the west end of Greenway Crescent, where ten unfrozen holes are spotted in oners and twors arnidst ZZ f.rozerLholes and a broken occurrence in the sewer trenches, all at spacings of l5 to 40 ft.

The absence from the rnap of unfrozen test-hole locations can be misleading. For example, beside Mystery Lake Road where it curves close to the town lirnit, one rnight interpret the three frozerr holes as a delineation of a continuous band of perrnafrost. Sorne of the unfrozen holes (shown for this exarnple), however, prove it to be another irregular discontinuous zor,e.

Inforrnation on the vertical distributlon of perrnafrost in the original townsite is scanty. Frozen ground was reported to have been excavated as deep as 34 ft near Selkirk Avenue. At sorne locations it extended only l2 ft below the ground surface. The rninimurn depth to the permafrost table was found to be about lB in.; the rnaximurn depth, although poorly defined, is probably 5 ft or greater. The vertical distribution is probably sirnilar to that in the new Westwood subdivision, described in the following section. -27'

Z. Permafrost observations in Westwood subdivision

In late August and Septernber I961, field investigations were conducted in the Westwood area prior to any construction activity, i. e. in undisturbed terrain. Many hand probings to depths of 4 to 5 ft indicated no frozen ground in the high areas on this site. In the low areas, no frozen ground was encountered in the sedge covered bogs containing open pools of water and the flat, sparsely treed areas with hurnrnocky thick sphagnum containing numerous rnoist to wet hollows during the course of rrrany hand probings to depths o!. 6 ft. Frozen ground, suspected of being perrnafrost becausq of the lateness of the thawing season, was encountered, however, in the wide transition zones separating the high and low areas, and in the narrow transition zones at the rnargins of the spruce trislandsrr in the low areas.

Detailed probings in the transition zones indicated that the depth to the permafrost table increased upslope and downslope away frorn the centres of the perrnafrost bodies. The slope of the permafrost table away frorn the centres varied, the rnaxirnurn encountered being about l0 to l5 deg. The rninirnurrr depth of thaw in the centres of the perrnafrost bodies was found to be about I8 in. At the upslope and downslope edges of the perrnafrost bodies, the depth to the perrnafrost table increased frorn this rninirrrum depth to rnore than 4 f.t in a horizontal distance of about 25 ft. In rnost cases the upslope wedge of the permafrost body extended beyond the upslope lirnit of the thick humrnocky sphagnurn moss. In the transition zorLesthat border on sedge-covered bogs, the downslope edge of the perrnafrost body tapered out at the edge of the bog. The perrnafrost table dipped steeply at the edge of the bog and the underside of the wedge dipped inward very steeply.

Seven holes were hand-augered to a depth of. Z5 ft at locations shown on Figure 34. These holes were designated as TB-1 to TB-? inclusive; the logs for TB -Zto'7 are shown in Figures 44,45,46147,48r49. Boreholes TB-4 and TB-5 were located in high areas, TB-l and TB-Z ln a wide, gently sloping transition zorle, and TB-6 and TB-7 in a narrow transition zone. Borehole TB-3 was located in a low area.

The vegetation at TB -4 and -5 consisted of spruce, jackpine and alder with scattered birch and poplar and ground cover of feather rrross and lichen about 3 in. thick overlying about 3 in. of organic rnaterial. Boreholes TB-l and TB-Z had a tree cover of dense spindly black spruce. The ground cover at TB-l consisted of a continuous carpet of feather lnoss about 3 in. thick overlying 2 in. of organic rnaterial and atTB-Z it consisted of hurnrnocky sphagnum rnoss varying in thickness frorn 6 in. to z ft overlying 6 in. of organic rnaterial. Boreholes TB-6 ancl TB-z had a tree cover of dense spindly black spruce. The ground cover at -28 -

TB-6 consisted of hummocky sphagnum lnoss varying in thickness frorn 6 in. to 2 ft and at TB-7 it consisted of an association of sphagnum and feather rnosses about 6 in. thick. The underlying organic rnaterial at these two locations was about 6 in. thick. The tree cover at TB-3 consisted of scattered black spruce with a ground cover of hurnrnocky sphagnurn rrloss about lB in. thick overlying I8 in. of organic rnaterial.

The soil profile in all boreholes was typical of the sequence previously described. The depth of brown clay varied from about 9 to IZ tt. The grey clays appeared to be wetter and more plastic than the brown clays.

Perrnafrost was not encountered in boreholes TB-3, -4 and -5. Frozen ground and ice were observed in the other holes. In TB-l a few very srnall ice crystals were found at a depth of 4 ft 9 in. Sirnilar rninute ice crystals were scattered through the profile to a deptl'r of about l0 ft. In TB-2, Located in the same gently sloping transition area as TB-1, a few minute ice crystals were visible at depths of. 4 f.t and 5 ft Z in. At a depth of.6 ft, several ice lenses about t/A in. thick were noted in dark brown layers. Between the depths of Ii ft 5 in. and 14 ft, randorn ice layer s t/8 in. thick and srnall ice particles were vlsible. It was not possible tq determine the presence of ice or frozen ground below the 14-ft depth because the hole filted with water during augering.

Boreholes TB-6 and TB-7, located at the edge of a spruce'risland, tl were augered in perrnafrost having a thickness of at least 25 ft. In TB-6, ice occurred throughout in layers frorn t/A to Z/+ in. thick. The thickest ice layers were encountered in the bottorn half of the hole. In TB-7, ice occurred throughout in layers frorn t/t6 to I in. thick. As in TB-6, the thickest ice lavers were encountered in the bottom half of the hole.

The streets in the Westwood subdivision were cleared of tree growth during the winter of l9 6I -62. Excavation of service line trenches began in January 1962, and the work in the areas to be serviced in L96? was cornpleted by October. A11 detailed exarninations of soil and perrna- frost conditions in the excavations were rnade during February and April. Detailed notes of perrnafrost occurrence and distribution in the trenches were kept by construction inspectors throughout the servicesr installation period. Prior to house construction in the new area, test holes were bored on a nurrlber of lots during Septernber and October to deterrnine the existence of perrnafrost. A11 available information with regard to the occurrence of perrnafrost has been plotted on a street plan of the subdivision (Figure 34), and profiles of the trenches showing horizontal and vertical extent of perrnafrost have been prepared. Sorne t1ryical proflles are shown in Figures 35r36. -29 _

The service line trenches (excavated by backhoes) were 3 to 4 ft wide with near vertical walls - no bracing was required when ln perrnafrost. Trench depths varied according to pipe grade requirernents but rnost were l0 to lZ ft deep. Whenever frozen ground extended below the pipe grade, however, the trench was rrundercutftto remove all frozer rnaterial and then backfilled with gravel to the pipe invert. This procedure was followed throughout except on Westwood Drive South, where, through one section, frozen ground extended below the reach of the machinery. Here, it was excavated as deep as possible (about 30 ft) and the trench backfilled to pipe grade with gravel.

The thickness, depth to, and areal extent of frozen ground encountered was found to be extrernely variable. In a trench on Mallard Crescent (Figure 35), for exarnple, the perrnafrost occurred in patches 30 to 100 ft long and 6 to l0 ft thick, starting about 4 ft beLow the ground surface. In contrast, one occurrence on Westwood Drive Souttr (Figure 36) was 650 ft long, and at least 30 ft thick (the deepest excavation was to 33 ft, which was still in permafrost). Farther east on Westwood Drive South, however, patches of the sarrre dirnensions as those on Mallard Crescent were encountered. Most of the occurrences in the Sturgeon - Sauger - Rainbow Crescent area (Figures 34r35,35) were 10 to l2 ft thick (rnaxirnurn thickness I7 ft in Sturgeon sanitary sewer trench), beginning Z Lo 4 ft below the ground surface. The horizontal length of these occurrences was generally 100 to Z5O f.t, with unfrozerl gaps between perrnafrost bodies of 5 to 300 ft or rnore. The greatest thicknesses occurred in the patches of greater length, as the profiles illustrate.

The horizontal dirnensions derived frorn trench observations cannot be used to define the size of perrnafrost bodies accurately, of course, because they are taken in an alrnost randorn pattern with respect to possible orientation of the frozen zones. It has been generally thought, frorn correlating borehole and trench inforrnation, that these zones were irregular in plan but roughly round, as opposed to being long and very narrow. This concept was substantiated when a road cut on Sauger Crescent exposed an ice layer over the full width of the cut (about 50 ft) and at least I00 ft along the road.

3" Ice segregation

When observing and describing the frozen condition of earth rnaterials perhaps the rnost irnportant characteristic that should be noted, besides ground ternperature, is the form of ice segregation. Perennially frozen soils rnay or rnay not contain ice but when present it should be carefully noted because of the serious engineering problerns that will occur upon thawing. -30 -

At Thornpson, ice is found in all perennially frozen soils, generally in the forrn of horizontal lenses. These lenses vary in thickness frorn hairline to 9 in. but the predorninant size range observed was frorn t/t6 to t in. thick. Spacing of lenses varies similarly. Although rnost ice layers were horizontal, many inclined and/or vertical lenses and randorn seams, usually quite thin (hairline to t/+in. ) were also observed. In sorne isolated cases, random srnall ice crystals ( 4 t/+ tn. dia. ) were seen at shallow depths (< I0 ft) below.the ground surface. Sorne soils, fine sands and silts, were bonded by ice not visible to the naked eye. Typical ice segregation is shown in Figures 4I and 42.

I Although no atternpt has been rnade to correlate the thickness and frequency of occurrence of ice Ienses with depth, it is apparent that the size of the ice layers generally increases with depth. As the thickness increases the spacing sirnilarly increases. A nurnber of exceptions to these general observations, however, were noied.

Many of the horizontal lenses seen in the trench walls were continuous for distances exceeding 40 ft. On only one occasion was the horizontal extent away frorn the trench observed and that was in a road cut on Sauger Crescent (Westwood). A thick ice layer uncovered in the excavation extended across the road for at least 40 ft. Sorne verification of this ass'urnption was noted in house connection trenches and at road intersections or manholes, where trenches were enlarged to facilitate joining service lines. Ice lenses were observed to be continuous in these trenches excavated at right angles to one another.

There is no apparent relation between the location of ice lenses and the soil varves. Layers of ice occurred between the light and dark Iayers and within thern, and sornetirnes intersected thern. In rnany cases, where lce lenses in a dark layer (ciay) encountered a light layer (silt), they dispersed into broken threads or non-visible ice at or near the interface, then re-united to forrn a lens again at the interface with the next dark layer. At the edge of a perrnafrost body the ice lenses norrnally ended quite abruptly although sorrre did becorne thinner and tapered out. Srnall inclusions of soil occasionally were found within the ice lenses. A1l lce observed was c1ear, sound and soft - no air bubbles were noted.

Most of the very thick ice layers occurred at depths greater than I5 ft. Heavy concentrations of ice lenses up to 2 in. thick and spaced at about Z in., occurred at depths less than I5 ft, however. In a I0-ft section, a total quantity of I I /Z tt of ice was cornrnonplace. Figure 39 illustrates the most extreme ice segregation observed, showing a total of Z I/Z ft of ice within a I0 -ft depth. Even where the ice segregation consisted of relatively thinner lenses, the quantity of ice was appreciable. In Figure 38 it can be seen that the ice segregation increases with depth - 3I -

frorn non-visible and randorn ice threads to horizontal lenses t/4to t in. thick, then decreases to L/15-in. lenses and hairline threads near the lower boundary of the perrnafrost body. A typical quantity of ice in this case would be about l8 in. in l0 ft. An example of lighter ice concentrations is shown in Figure 37, where in a 7-ft section the total quantity of ice is less than I ft.

4. Ground temperatures

To measure ground t.ernperatures six specially fabricated therrnocouple cables were placed to depths of about 25 ft in the test holes hand augered at various locations in the Westwood subdivision during Septernber 1961. The installations consist of. ZO gauge copper - constantan duplex wire placed inside an oil-fitled plastic pipe. Thermocouple junctions are spaced at depths of 0, I,2,3,4,6,8, 10, lZ, 15, Z0 and 25 f.t below the ground surface. Each cable terrninates at a weather-tight switch box (aIso oil-filled) (Figure l9) where the individual wires are connected to a rotary selector switch. A portable precision potentiorneter, modified for field use under cold weather conditions, is used to measure ground temperatures. It is thought that al1 rneasurernents are reliable to * 0.2"F.

Regular observations were begun on l2 February 1962. Frorn that date, ground ternperature rneasurements have been carried out at about 2-week intervals. Typical plots of ternperature versus depth are shown for the six installations in Figur es 43r 44, 45r 46, 47, 48. Also shown are the depth of frost penetration and the depth of thaw (plotted on a tirne versus depth basis) for non-perrnafrost and perrnafrost areas respectively. A log of the soil and perrnafrost conditions encountered at each hole is included. Cables IT -ZZ, -23 and -24 wer e placed in areas having no perrnafrost while cables IT -Zl, -25 arrd -26 indicate permafrost for the tr full depth of the holes. The location of each cable is shown in Figure 34.

Ground temperature observations have been taken for only nine months, and,'therefore, no rigorous analysis of the results can be rnade at this tlrne. Some pertinent comrnents concerning the local ground therrnal regirne are applicable, however.

Installation IT -23 is located in a high, well-drained area havlng a very thin rnoss cover; rT -ZZ is located in a low, extrernely wet area having a substantial thickness (tZ to tB in. ) of sphagnurrr rnoss. Cable

'l' Cable IT -23 was removed on I September 1962 because of construction activity but was installed at a new location in sirnilar terrain on 9 October 1962. -32 -

IT-24 was placed in an intermediate zone - a relatively high dry area with a ground cover of feather rnoss 5 in. thick but close to a sloping transition area. No frozen ground was encountered in these boreholes and no perrnafrost was indicated by the ground ternperatures. It will be noted that the irnrnediate effect of air temperature, or local climate, is evident to about the sarne depth (15 ft) at all three locations but the time lag with depth is greater at IT -22. la addition, seasonal frost penetrated to the 3-ft depth at IT -24 and -Z3by I.March and 20 April respectively, whereas at IT -ZZ this depth was not reached until l5 May. The rnaximurn frost penetration recorded was 5 ft at IT -24. The seasonal frost retreated very quickly at all locations but more rapidly at IT -23 (the ground at each installation was free of frost by the first week in June). The rnean ground ternperature in the higher area is apparently about 37"F and in the low wet area about 33'F. For the intermediate area, a mean ground ternperature of about 34"8 is indicated.

Cable IT -ZI is located in a gently sloping transitional zone interrnediate between a high and a low area. Cable IT -26 was placed within but near the edge of an rrislandrr of perrnafrost and IT -25 was located at approxirnatety the centre or well within this I'island.rr Each site had a ground cover of sphagnum rrross underlain by up to 2 ft of. decornposed organic rnaterial and each was located near generally lower, pocrly drained areas.

Thawing of the active layer began about the rniddle of May and proceeded at a relatively uniforrn rate at each site but with IT -2I having a somewhat higher rate, so that by the first week of October the rnaximurn thaw of.6 ft had occurred at that location. IT -26 reached its maxirnurn thaw of.3 ft by the rniddle of July but the rnaximurn thaw of 3" 5 ft at IT-25 did not occur until the first week of october. Much lower temperatures occurred at and just below the ground surface during the winter (between l5 and Z5"F) at these locations when cornpared to those observed for the installations located in the non-perrnafrost areas (between 25 ar.d 32"f'). The irnrnediate effect on the local climate is apparently felt to a greater depth at IT -25 and' -26 (apptoxirnately 12 ftl than at IT -21 (about B ft). The mean ground temperature appears to lie between 3l and 32"F with IT -25 having the lower value.

5. T errninology

Frorn reports describing the results of subsurface investigations and in discussions with various people at Thompson it has been noted that I'heavy'r the descriptive terrns "Iight'r and (or I'hardrt) perrnafrost are frequen*"iy used without definition. They apparently were coined to describe: -33-

(l) The relative ease with which the frozen soil could be hand-augered, or

(?) The relative ease with which the frozen soil could be excavated by machinerj; or

(3) Whether the visible ice in the soil was continuous or occurred only in isolated lenses or random crystals, or

(4) The relative thickness or areal extent of the frozen ground occurrence.

The first two rneanings describe the condition of the frozen ground, the third irnplies that permafrost (only) rneans soil with ice ln it, or worse, refers to the ice itself and the last refers to the distribution and occurrence of perrnafrost. Perrnafrost or perennially frozen ground is defined exclusively on the basis of temperature, i. e. refers to the thermal condition, irredpective of texture, degree of induration (hardness), water (lce) content or lithologic character. Loose use of descriptive terms, such as those noted above, can be misleading and should be discouraged unless their meaning is defined and rnade quite clear.

IV. PERMAF'ROST OCCURRENCE AT THOMPSON - A DISCUSSION

A. Historical

The origin of permafrost is hot well understood and has been a subject of rnuch conjecture, although generally of academic lnterest only. More relevant, in this discussion, is the question as to whether it is presently aggrading or degrading, particularly in the southern regions.. Thornpson is located near the southern boundary of perrnafrost. Here, permafrost occurs in scattered patches of lirnited extent both areally and vertically, being only a few feet thick and having ground temperatures close to 32"F.

Following the retreat of the last continental glaciers ('W-isconsin period) a large lake (Agassiz II) covered much of the area in Manitoba north (and south) of Lake Winnipeg for a relatlvely long period of tirne. No frozen ground could exist under this lake during its lifetirne. The effect of the I'heat sinktr created by this large body of water would have certainly thawed any frozen ground present prior to the forrnation of the lake. It is, therefore, evident that the perrnafrost existing in the Thornpson area is of relatively recent origin having forrned since the retreat of the last glacier or, more specifically, since the draining of Lake Agassiz II, believed to have occurred sorne 5000 years ago. -34-

Geologlcal evidence of glacial melt-water erosion and depositlon and rapid differential uplift of the land indicates that at the close of the Wisconsin period, some 7000 years ago, a significant and qulte abrupt warming of the clirnate occurred which caused rapid melting of the continental glaciers. It is believed that this warrning resulted in mean annual air ternperatures that rnay have been as much as 5oF warmer than at present. Further evidence is available to show that a cooling of the clirnate followed this period - perhaps 2500 to 30.00years ago (19)., It is well known that clirnatic fluctuations of large and small rnagnitude have occurred through the ages. The formation and existence of permafrost is closely linked to these fluctuations. At Thornpson, therefore, it is quite possible that the perennialLy frozen ground originated as recently as 2500 years ago. Presurnably it developed continuously, i. e. everywhere at the sarne time. At present it appears that there ls an over-all warming trend in the clirnate that is resulting in the deg.radation of perrnafrost. Local environrnental differences have conditioned this recession such that perrnafrost is discontinuous, i. e. in patches in the southern fringe area.

The forrnation and existence of permafrost are controlled by a nurnber of clirnatic and terrain features. The effects that these have, either indivldually or in combination, &r€ rrrost difficult to analyze and are not, as yet, fully understood (20). At best, in rnost cases, they can be discussed ln a qualitative rnanner only.

B. Clirnate

The clirnate of an area, consisting of a nurnber of cornponents including air ternperature, precipitation, wind, and solar radiation, ls one of the rnost irnportant factors affecting the existence and distributlon of perrnafrost. Previous investigations (Zl) have shown that there is a broad. relationship between air ternperature and perrnafrost distribution. It is of interest therefore to cornpare the mean annual air ternperature observed at Thompson, and the adjacent stations of Wabowden and Gillarn, wlth the perrnafrost conditions existing at these locations and to cornpare the distribution of permafrost at Thorrrpson with other settlerrrents in having similar mean annual air ternperatur es (221.

. Observations at various localities in Canada have shown that the rrrean annual ground temperature is frorn 4to 8"F higher (averaging about 6'F) than the mean annual air ternperature, depending on 1ocal conditions. Therefore, the rnost southerly occurrence of permafrost probably exists where the mean annual air temperature is in the range of about 26 to 28'F. During the construction of the Hudson Bay Railvdy, the rnost southerly occurrence of permafrost was reported at Wabowden where the rrrean anmral -35 -

temperature is 27.6"F. Here, patches of permafrost are scattered and are only a few feet thick. Further north at Thornpson, perrnafrost is rnore widespread and bodies of perrnafrost exceeding 25 ft in thickness have been encountered. At Gillam, where the rnean annual temperature is 23.l" F permafrost is even rnore widespread than at Thornpson and probably thicker.

The mean annual air ternperature of Thornpson 1675 tt above sea level), based on observations taken frorn 1958-61 inclusive, is 24.9"F. It is probably safe to assume that it lies in the neighbourhood of 25"F. The known occurrence of permafrost as reported at a nurnber of stations in northern Canada having mean annual air temperatures (23, 24) similar to Thompson is given in Table IV(a).

An examination of this table shows that the distribution of perrnafrost varies considerably among these stations. The ilifficulty of cornparing these seven locations is that the rnean annual air ternperatures are based on varying periods of time frorn 29 years at Hay River to 4 years at Thompson. Another problem ls that the present distribution of perrna- frost is also affected by past fluctuations in mean annual air ternperature. Despite these difficulties, it is possible to rnake general cornparisons between Thornpson and other stations and it ls useful to see how Thompson fits lnto the country-wide pattern. Paradoxically, the thlckest permafrost occurs at Aishihik although its rnean annual air ternperature of.25.5oF is the highest of the group. On the other hand, no perrnafrost has been reported at Nitchequon althoughits mean annual air ternperatur e of.24.4"F is the lowest of the group. The mean annual air ternperatures and distribution of perrnafrost at Fort Sirnpson, Fort Providence and Hay River are similar to Thompson.

Air temperatures may be used tn another way to cornpare various localities andthat is by rneans of freezing and thawing indices calculated frorn daily air temperature observations. These indices give an indication of the arnount of heat added to or extracted from the ground. The freezing and thawing indices for several northern stations (25) having values sirnilar to those for Thornpson (within 100 degree days) are listed in Table IV(b) and IV(c) together with reported observations on the occurrence of perrnafrost. Again it may be seen that wide variations can occur in the distribution of perrnafrost among stations having sirnilar freezing or thawing indices.

In Table IV(b), perrnafrost is continuous and much thicker at cape Hopes Advance than at Thornpson; this can be e>cplained by the much lower thawing index at Cape Hopes Advance resulting frorn a lower mean annual air temperature. Hay River has freezing and thawing indices sirnilar to Thompson resulting from a similar mean annual air ternperature -36-

and has comparable perrnafrost distribution. Fort Smith has freezing and thawing indices slightly higher than those at Thornpson resulting frorn a slightly higher rnean annual air temperature. No permafrost has been reported at Fort Srnith although a few persistent ice lenses have been encountered at depth, which suggests that this settlement may be near the extrerne southern edge of the perrnafrost region.

In Table IV(c), perrnafrost is rrore wiflespread and rnuch thicker at than at Thornpson; this can be explained by the forrner stationrs rnuch higher freezing index resulting frorn a lower rnean annual' air ternperature. The distribution of perrnafrost at Fort Resolution is sirnilar to Thornpson although it has a slightly higher freezing index which results frorn a lower rnean annual air ternperature.

From the foregoing discussion, it is evident that cornparatively broad or general relationships do exist between the distribution of perrna- frost and clirnate as expressed by rnean annual air ternperatures and freezing and thawing indices. It appears that the mean annual air ternperature of 24.9"F at Thornpson is just low enough to support the existence of perrnafrost although its distribution is patchy. Mean annual ground temperatures in perrnafrost at Thornpson are known to be about 3I'F. A change in the rnean annual air teniperature can result, over a long period of tirne, in a significant change in the areal extent aurd thickness of perrna- frost. A change of l"F, for example, could result in a difference of perhaps I00 to 150 ft of perrnafrost thickness, assuming a geotherrnal gradient of l"F/LOO to i50 ft. At Thompson, a decrease of loF could result in an increase ofperrnafrost thickness by 100 to I50 ft and an increase of loF could cause the perrnafrost to disappear. The rnean annual air ternper- ature of Yellowknife is about Z I/Z"F lower and the perrnafrost about 200 ft thicker than at Thornpson (Table IV(c) ). Fort Smith has a slightly higher mean annual air ternperature and pernrafrost appears to be absent (Table r v(b)).

Although climate controls the broad pattern of permafrost distribution, it does not explain the patchy and varied occurrence of perma- frost at a particular location, such as Thornpson, and other stations having similar rrrean annual air ternperatures, such as Hay River and Fort Sirnpson. Nor does it e>rplain why stations having cornparable mean annual air teniperattrres, such as Aishihik and Fort George, have different permafrost t', conditions. These variations in perniafrost occurrence appear to be governed by local rnicro-clirnatic and terrain features. Provided the clirnate is such that it will support the existence of permafrost, the distribution of individual islands appears to be conditioned by variations in features such as snow cover, relief, drainage and vegetation. The effects of these terrain features are discussed in the following sections in an atternpt to e>rplain the differences in the occurrence of perrnafrost throughout the Thornpson site. -37 -

C. T errain I'eatures

Glven a particular clirnatic regime that is conducive to the existence of perrnafrost, such as in the Thornpson region, it is the therrnal characteristics or properties of the varlous surface and subsurface terrain features operating singly and in combination that control the local variations in perrnafrost conditions. Surface features include snow cover, relief, surface drainage and vegetation; subsurface features include soil and subsurface drainage.

The occurrence of permafrost in the original townsite and the Westwood subdlvision, as deterrnined to October 1962, has been shown on Flgures 33 and 34. The major boundaries of the high and low areas, differentlated on the basis of vegetation and relief and dellneated on the air photo of the townsite area (Figure ?3lrhave been superlmposed on the plot of permafrost occurrences and are shown in Figure 49. In addition, the ground surface contours (Figure I l) have been superirnposed on the plot of permafrost occurrences and are shown in Figure 50. The relation between permafrost occurrences and relief has been indicated, for clarlty, on separate illustrations.

It is apparent from an examination of Flgures 49 and 50 that mo6t of the permafrost encountered at Thornpson occurs ln the sloping transitlon zones between the areas of relatively high elevation and good drainage, and the areas of relatively low elevation and poor drainage. This includes the narrow transition zones at the edges of the spruce rrislandsrrwithln the low areas.

Examples of perrnafrost located between the high and low areas are numerous both in the original townsite and in the new Westwood subdivision. one such exarnple can be noted in the block bounded by Selkirk and Churchill Avenues just west of Mystery Lake Road, where more than a dozen test holes revealed the presence of permafrost. A row of test holes in house lots along the west side of Caribou Drive, just west of Cree Road, anda row on the south side of Greenway Crescent at Thornpson Drive are other examples. In the northern section of the orlginal townsite, test holes along the east side of Silver Crescent and the west side of Cobalt Crescent, and test holes and service line trenches along Riverside Drive substantiate 'W'estwood thls general assurnption. In the subdivision, permafrost was encountered in test-holes along Pike Crescent in the northern section, and the east leg of Mallard Crescent extending south from Westwood Drive North.

Examples of permafrost located around spruce itislandstt include nurnerous occurrences in test-holes and service line trenches in the east-central portion of the original townsite along Ash Street, Juniper Drive -38-

west of Cypress Crescent, and the first block of Deerwood Drive extending west frorn Cree Road. In the southwest portion of the Westwood subdivislon, permafrost was encountered around the edge of spruce Itislandsrt ln test-holes and service line trenches along Westwood Drive South between the two ends of Partridge Crescent.

From information obtained, primarily from observations in the Westwood area, it appears that,the occurrenc.e o{ perrnafrost at Thornpson rrtay be arbitrarily divided into two categories based on the thickness of the perrnafrost bodies - those less than I5 ft and those greater. Most of the permafrost bodies observed falI inthe first category, i. e. less than I5 ft thick. Several greater than I5 ft thlck were encountered, however, some exceedlng 30 ft in thickness (Figure 36). There is no apparent relation between permafrost thickness and existing terrain features. This suggests that the variations are a reflection of previous environrnental conditions not evident at present. The heavier concentrations of ice were noted to occur at the greater depths.

Exarnination of the ground ternperature graphs (Figur es 43r 44 45r46,47,48) shows that a delicate state of thermal equilibrium exists ln the ground at Thornpson - mean ground ternperatures being just slightly below 3Z"F in perennially frozen ground, and just slightly above 32"F in ground having no perrnafrost. The effect through the year of the air temperature regirne on the ground ternperatures varies considerably from one borehole to another. Consideration of this effect in relation to variations in surface cover indicates certain relationships, sorne of which appear paradoxical.

Boreholes IT -ZZ, -23, and -24 are located in non-permafrost areas (see page 3l for description of vegetation and drainage)" Durlng the winter of I96I-62, winter frost penetrated rnore slowl.y in IT -ZZ, as might be expected because of the thick cover of wet sphagnum rnoss, than in IT -23 and -24, reaching a rnaximum depth of.3 ft by l5 May. ComparinglT-?3 ar:d -24, it is curlous to note that the winter frost penetrated to the 3-ft depth by I March in IT-24 although it did not reach the same depth in IT-23 where no rrross exists until Z0 April. The lower rate of frost penetration in lT -ZZ cornpared to IT -23 and -24 is also reflected in the rate of penetration of the effect of the annual air temperature cycle in the three holes. At rT -23 it penetrated to I5 ft much earlier (July) than either IT'ZZ or -24 with IT -ZZ having the greater tirne lag. Presurnably these effects are the results of the high volumetric heat capacity of the saturated sphagnurn moss and underlying soil.

Boreholes IT -2I, -25 and -26 are located in perrnafrost areas in transition zones, each having a surface cover of sphagnum rnoss. Comparing the depth of thaw with the thickness of the moss cover, it is _39 _

interesting to note that the greatest depth of thaw was associated with the thickest living moss cover. On 8 October 1962 t}'e depth of thaw was 6 ft at IT -ZL but was less than 4 ft at IT -25 and -26, the thickness of the rrross cover being 9, 6 and 4 in. at the three hole locations respectively. The underlying decornposed organic rnaterial (peat) however, which was 8, 14 and 8 in. thlck at IT -25, -26 and -ZI respectively, no doubt contributes to this conditlon. The effect of the annual air ternperature cycle appears to be greater in IT -?5 and -26rhaving a thinner nross cover, than in IT-21; it reached a depth of about LZ ft it the first two holes and only B ft in the thir d.

From the foregoing discussion, it appears that the random ice crystals up to t/+ in. dia. that were observed to depths of l0 ft at sorne locations (and at 4 and 5 ft at IT -ZI) could be associated either with seasonal frost or permafrost. Because the effect of the annual air temperature regirne penetrated to depths exceeding I0 ft in sorne areas, lt Is possible that such lce lnclusions could be formed and rnelted in the sarne yeat. On the other hand, they could be formed in I year and persist for several years before being affected by above freezing ternperatures frorn the ground surface.

The general pattern of permafrost distributlon appears to be one of a broad correlation with certain combinations of the terraln features. These are so closely inter-related that it is virtually impossible to assess the contribution of each feature lndividually without including some aspects of another feature. In the following discusslon, the rnain ernphasis ls placed on the particular feature under consideration but aspects of other features are included where they are pertinent.

l. Snow cover

Although snow is basically an elernent of climate, it is considered as a terrain feature in this discussion because snow cover lnfluences heat transfer between the air and the ground and hence affects the distribution of permafrost. The snowfall regirne and duration of snow on the ground are both critical aspects of this terrain feature. A heavy fall of snow in the fall and early winter will inhibit winter frost penetration and the forrnation of permafrost. On the other hand, a thick snow cover thaf persists on the ground in the sprlng will delay the thawing of the underlying frozen ground.

The stations in the , and the , prewiously noted in Table IV(a), having a rrlean annual air temperature sirnilar to Thornpson, have considerable permafrost ln contrast to Fort George and Nitchequon in Quebec, where none has been reported. Hudson Bay seerns to have an appreciable effect on the amount of snowfall over the region irnrnediately to the east, especially in the fall and early winter before this body of water becornes ice covered. Examination of -40 -

the snowfall records reveals that the snowfall for October to Decernber, incluslve, is approximately 47 ftt. at Fort George, 50 in. at Nitchequon, and about 20 in. at the statlons ln northwest Canada. Only a few scattered snow cover observations have been made at Thornpson but the snowfall at nearby Wabowden and Gillarn for the fall-early-winter period, totals l8 and 25 in. respectively (Table I(d) ). It appears, therefore, that the relatively low snowfall ln the fall and early winter, may contribute conslderably to the existence of permafrost at Thompson and that the winter frost penetration and the formation of perrnafrost rnay be greatly lnhiblted by the thicker insulating cover at the Quebec stations.

There may be significant differences ln snow cover between the densely forested areas and the more sparsely treed areas whlch contrlbute to the variable occurrence of perrnafrost. Many addltional and systematlc observatlons of snow cover propertles and depths through the winter are requlred at Thompson however before any speciflc relationsirips can be established between thls feature and the distrlbution of individual perrnafrost islands.

Z. Rellef

The relief appears to be a signiflcant feature affecting the dlstributlon of permafrost. Most of the permafrost bodies are located elther ln broad gently sloping transition zones between high and low areas or in narrow rrtore steeply sloping transition zones around spruce lrislandgll wlthin the low areas. In keeping with the general influence of relief on surface and subsurface drainage, it appears that the transition zones have sufficient slope for rnoderate drainage.of water, Lack of such drainage, e. g. ponding of water, would result in the thawing of the underlying perrna- frost. On the other hand, the slopes are not too steep to be excessively dralned and therefore have sufficlent water for the growth of sphagnum rnoss which appears to be an important feature associated with the presence of perrnafrost (and also ice lensing).

Another irnportant aspect of relief is slope orientation. The fact that a north-facing slope receives less insolation through the year than a nelghbouring south-facing slope can contribute to variations in the ground thermal regirne. For exarnple, perrnafrost was encountered on Sauger Crescent in the northwest corner of the Westwood subdivision on the north-facing slope of the Burntwood River valley. It is quite possible that no Perrnafrost exists at the corresponding location on the south-facing slope of the Burntwood valley although no investigatlons have been carried out to verify this.

The difference between north- and south-faclng slopes is evident throughout the year. During the winter, the snow on north-facing slopes -4t -

recelves less lnsolation and is colder than the snow on south-facing slopes and thus contributes to lower temperatures in the underlying frozen ground. In the spring, the snow lasts longer on the north-facing slopes and delays thawing of the underlying frozen ground. During the surnrner, north-facing slopes receive less insolation than south-facing slopes resulting in less solar energy being absorbed into the ground, provided the surface vegetation is similar on both slopes"

The differences between insolation received at the surface of north- and south-faclng slopes.are caused by the difference in the angle of incldence of the sunrs rays on the two slopes and the variation of albedoo with this angle. During the surnrner when the sun is at a high altitude, the percentage difference between the angle of incidence on each slope is srnall and thus the albedo difference is srnall. In the late fall, when the sun is at a low altitude, the percentage difference between the angle of incidence on each slope is rnuch greater, resulting in the north facing slope having a rnuch higher albedo than the south faclng slope. This means that a rnuch higher percentage of the incorning solar radiation is absorbed on the south facing slope with consequent effects on the therrnal regirne of the ground.

Varlatlons in elevation of even a few feet may cause minute but sufficient differences in air ternperature which would affect the ground temperature regirne. Air movement between high and low areas, such as the drainage of cold air at night frorn a high area downslope to a low area, is,a rnicro-clirnatic feature associated with relief which rnay be slgnificant.

3. Drainage

Another irnportant feature affecting the distribution of perma- frost is surface and subsurface drainage. The occurrence and movement of surface and subsurface water exerts an irnportant influence on the thermal regirne of the ground and is conditioned by the relief, vegetation and soil. Because of the heat storage capacity of water, its movernent frorn one area to another signifies the transfer of thermal energy frorn one point to another and the existence of water at any given location indicates an excess of therrnal energy there. Moving or standing water such as occurs in the low areas below the transition zones, inhibits the forrnation and preservation of perrnafrost. It is probable that in this fringe area a change in drainage conditions in a permafrost area producing an increase of water would, in tirne, no doubt result in thawing of the perrnafrost. Water movernent may be affected also by the sphagnurn moss. It is suspected

'k Albedo is the rneasure of the reflectivity of a surface; an albedo of 60 per cent means that 50 per cent of the incoming solar radiation is r eflected. -42-

that the sphagnum rrloss is able to wick moisture upslope from the low areas and the upper llrnit of the moss on the transition zones rrray rrrark the uppermost elevation to which water can be transported in this rnanner.

4. Soils

The role of the soil, particularly with respect to its effect on rnoisture movernent is not well understood but some aspects are rnentioned here. The rnotsture content is highest in the grey soils that underlie the brown but is fairly high in all soils. The clay stratlficatlons in the varves are rnuch less perrneable than the silt in both the horizontal and vertical directions, and thus rnay have an effect on the occurrence of perrnafrost. Because of the relative irnperviousness of the clay layers, it is possible that vlrtually all of the rnoisture movea horizontally through the rnore perrreable silt layers rather than vertically. It is difficult to assess the relatlve irnportance of these various characteristics in relation to the formation and existence of permafrost. It is known that rnoisture moves towards a freezing plane in the ground in response to negative suctlon pressure created at the plane. Moisture also rnoves along a ternperature gradient frorn a cold area to a warrn area. In the case of the permafrost at Thompson, the rnovernent of ground moisture could be both towards a freezing plane - i. e. seasonal frost or the permafrost table, and towards a relatively warrn body of water at the bottorn of a transition zone in a low area. The relative importance of these t,wo mechanisrns rnay vary frorn one area to another.

5. Vegetation

The vegetation is undoubtedly an extremely significant feature affecting the distribution of perrnafrost and its characteristics are greatly influenced by relief, drainage and soils. A perrnafrost or non-perrnafrost condltion rnay result from the interaction of vegetationrrelief and drainage components of the terrain which produce a certain ground therrnal sltuation.

At Thompson two t1ryes of vegetatlon can generally be used as fairly reliable lndicators of a perrnafrost conditlon. The presence of sphagnurn moss and/or stunted, sparse to rnoderately dense spruce growth has been found to be nearly always associated with permafrost - provided that reasonably well-drained conditlons exist. This qualification is rnost important. The converse is not true, however, because permafrost is also found under other tlpes of moss and tree cover.

The density and height of trees are important aspects of the vegetation lnfluencing the near ground surface wind velocities, Wind speeds are rnuch lower in areas of dense growth than ln areas having stunted scattered trees or no trees. The rnovement of air represents the transfer -43-

of heat from one area to another. In the high areas, tree growth is high and fairly dense and probably results in low wind veloclties. In the low areas and transition zones, the trees are shorter and scattered and there are nutrlerous open areas which perrnit higher wind speeds and thus the rnoverrterrt of rnore heat away frorn these areas per unit tirne than frorn the high areas. Therefore, the possibility of slightty lower air temperatures and ground ternperatures, because of higher wind speeds, is greater than in the high areas.

The inter -relation of. vegetation and permafrost can be surnmed up briefly in a statement for each type of area. In the high areas, there is no sphagnum moss because of the good drainage which allows the growth of birch, poplar, jackpine and large spruce, and there is no perrnafrost. In the low areas, there is thick sphagnurn rnoss and stunted spruce because of the poor drainage but there is no perrnafrost because of the excess water. In the transition zones: sphagnurn moss grows because there is enough water to support it; spruce is the rnain tree species but ls stunted because drainage is only moderate; and perrnafrost can exist because there is not too much water to thaw it. The spruce Itislandsrt are too wet for birch, poplar and jackpine but not as wet as the low areas resulting in dense but stunted spruce growth and permafrost around their edges.

6. Anornalous perrnafrost occurrences

With reference to Figure 33 it will be noted that there are a number of locations where perrnafrost was encountered that do not appear to fit into the general pattern, i. e. do not occur in transition zones. A closer exarninatlon of these areas on the aerial photograph (Ftgure Z3) and contour rnap (Figure 50) suggests that their exlstence can be e>cplained, however, by certain features of the terrain. It appears that the perrna- frost in these areas may be associated with certain transition zone characteristics, slope orientation, moss type, or sofire other feature. From the subsurface information obtained to date frorn test-holes, service line trenches, etc., it is possible to delineate about fifteen separate permafrost areas that lie outside of the transition zones.

About two-thirds of these perrnafrost areas appear to lie on north-facing slopes. The rnaximurn slope is about 5 deg but some are so gentle as to be alrnost irnperceptible, being as low as I deg. The difference between the albedo and the absorption of solar energy on a slope of even this low angle compared to a horizorfial ground surface or a south-facing slope, particularly when the sun is at a low altitude, is sufficient to contribute to significant differences in the ground thermal regime over a very long period of time. As mentioned previously, a perrnafrost area occurs along Sauger Crescent on ground that slopes down about 5 deg to the north. The test-hole put down very close to the Burntwood River -44-

west of Sturgeon Crescent actually appears on the aerial photograph to be on a slight north-facing slope.

Similarly, the area at the corner of Deerwood Drive and Beaver Crescent extends frorn the 700-ft contour to the 690-ft contour in a northward direction (Figure 50). A slight but distinct break frorn the horizontal to a north-faclng slope is evident on Hillside Crescent. In this area the edge of the permafrost appears to coincide with the 665-ft contour and extends northward below the 660-ft contour. The extensive perrnafrost area between the east section of Juniper Drive and Thompsod Drlve South lles on an alrnost imperceptible north-facing slope. The other areas having the same orientation occur on the block bounded by Basswood, Elrn and Blrch, between Nickel Road and Mystery Lake Road just south of Rlverside Drive, around the northeast corner of Rlverside Drive, the west leg of Kelsey Bay, and along the sewer outfall line west of Nelson Road.

The rernainder of the fifteen areas, not rnentioned above, do not appear to be aseociated with a particularly noticeable terraln feature. The area around the west end of Goldeye Crescent slopes very sllghtly down to the southwest to a shallow draw. Although it resembles a high area, there may in fact be sufficient slope coupled with drainage and vegetatlon conditions favourable to the existence of permafrost. The area between the two gullies north of Thompson Drlve North appears to be fla.t or slightly sloping with a vegetative cover of spruce and sphagnurn moss. Along Deerwood Drive and Elk Bay, the perrnafrost occurs in a small hlgh area which may in fact slope sufficiently and have other characterlstics resembling a transition area. The area along Lyr* Crescent is squeezed between a low area and a gully, which llke the previously rnentioned areas, may ln fact have transitiott zorre characteristics. One area in which the cause of the occurrence of permafrost does not seern to be explained by any of the foregoing features is the portlon of the sewer outfall line extending northwest-southeast from Riverside Drive acrosa Mystery Lake Road.

7. Conclusion

It is evident from the foregoing discussion that because the effects or contrlbutions of the varlous terrain features on the existence and distribution of permafrost are so lnterdependent and closely interwoven, it is most difficult to assess the effect of individual features and virtual.ly irnpossible to place quantitative values on them. It appears that different features dominate frorn one permafrost area to another but in every case, a variety of features has to be considered. For exarnple, permafrost may exist ln one particular area because of an insulating cover of sphagnum rnoss, in another because of certain soll and moisture conditions, and ln -45-

another because it is located on a north-facing slope. In all of these cases, the existence of perrnafrost is very precarious as evidenced by the proxirnity of its temperature to 32"F. Over a sufficiently long period of tirne even a very small change in any one terrain feature affecting the occurrence of permafrost can appreciably alter the thermal regime and therefore the permafrost conditions.

V. ENGINEERING IMPLICATIONS

The englneering problerns associated with design and construction in this southern fringe area (of the discontinuous zonel of perrnafrost are sornewhat different and rrrore difficult than those encountered in the northern portlon of the permafrost region, i. e. the continuous zorle. Thawing of the perennially frozen ground is difficult to prevent once the area has been disturbed and rnust therefore be anticipated in any engineering work. If the problems and their causes are not ful1y understood and designed for, the effect that thawing has on various structures can be dramatic and rapid. Substantial settlernent and differential rnovements can and do occur. Although a detailed account is beyond the scope of this paper, sorne general cornrnents regarding engineering problerns in this area are pertinent.

A. Permafrost Conditions

Proper siting of structures is most irnportant in these areas because of the irregular distribution of perrnafrost. The areal extent of the patches of frozen ground encountered can vary considerably - from small islands a few feet in diarneter to larger areas several hundred feet or more in size. These patches of frozen ground can be separated by extensive areas of thawed ground or can occur almost side by side. similarly, the vertical distribution can vary widely, the thickness of the patches of frozen ground ranging from perhaps 6 ft to rrrore than 30 ft. In addition, the depth to the perrnafrost table (1. e. the upper surface) can vary from z to 3 ft to B to l0 ft below the ground surface. Great care must be taken therefore in locating structures under these conditions.

All perennially frozen materlals found in this southern area have a rnean ternperature close to 30'F. A small change only in the local environrnental conditions under which perrnafrost exists is required to change their condition frorn the frozen to the thawed state - with a corresponding change in properties. Once disturbed, the frozen conditlon will probably not recur. Although these rnaterials rnay exhibit considerable strength when frozen, a substantial decrease in strength is evident in rnany soils -46-

when thawing takes place. This is particularly so in soils having high ice contents. Large settlernents and differential movements (measured in feet) can be expected when such soils thaw and the water drains away.

At sorne locations in the southern fringe area the frozen condition rnay have disappeared only recently. Thawing of rnaterials that contalned much ice will result initially in unstable soil conditions if this moisture has not been able to drain or if readjustrnent of the soil water content takes place very slowly. This unconsolidated material may provide foundation difficulties if it is not realized that permafrost, although not presently evident, has thawed only recently.

Thls brief mention of sorne of the rrore important factors to be considered in this area ernphasizes the critical nature of and the irnportance that should be given to a careful investigation of the conditlons exlsting at a site proposed for developrnent.

B. Site Investigations

The need for adequate subsurface investigations to deterrnine soil and permafrost conditions in this region cannot be overernphasized. It is particularly irnportant that the extent of perennially frozen ground, both areally and vertically, and the moisture (lce) content and properties of the frozen soils be determined. Investigatlons are normally carried out in two phases - a prelirninary study of the over -all area under consideratlon followed by rnore detailed investigations on the site.

For a preliminary appraisal of an area, stereoscopic examination of air photos of proposed sites can provi.de much useful information on the terrain and general site conditions. Depending on the experlence of the air photo rrreaderrr or trinterpreterrr it is usually possible to lnfer subsurface conditions. A kno'wledge of the local climate and geological history are a prerequisite. Following this office study, selected areas, subdivlded on the basis of sirnilar terrain characteristics (e. g. relief, dralnage and vegetation), should be examlned in the field to check predictions rnade durlng the air photo study and to gather information on the occurrence and distribution of perrnafrost and other subsurface conditions.

Fie1d work must include a prograrr] to exarnine subsurface materials in situ and to obtaln samples for moisture content deterrnlnations and classification and identification of the soils encountered. The depth of thaw, depth of seasonal frost penetration, depth to the permafrost table, etc. and their variabllity over the site should also be deterrnined during this study. This work can be carried out by probing, hand augerlng and drilling methods andf or the excavation of test pits. A rnuch larger than -47 -

average moisture content of unfrozen rnaterial may indicate whether it has only recently thawed.

Finally, when a suitable site has been selected, more detailed investigations are required at the locations proposed for all rnajor structures and in many cases for all structures, large or srnall. These areas can then be ass€ssed with regard to the effect that permafrost (or rnore specially rtthawedrrpermafrost) will have on the s.tructures. Engineering design can then follow.

C. Design and Construction

Because dlsturbance of local conditions cannot easily be prevented and will ultirnately cau6e thawing of the perennlally frozen ground, foundation design must necessarily neglect the propirties of the ftozen soil and rnust be based on the thawed properties. Although initially the frozen condition provides sorne bearing strength, it is generally assumed that the Irozen ground will thaw during the life of a structure. Artiflcial refrigeration of the ground has been considered and resorted to at some northern locations to maintain the frozen condition.

Both surface and buried foundations have been used in the Thompson area; local conditions rnust be exarnined very critically, however, before selecting a final design. Thawing of soils having high ice contents will result in very unstable subsurface conditions if the resulting water cannot drain away. Drainage rnay be irnpeded by irnpermeable soil or by surroundLng frozen ground. Buried foundations normally extend through the frozen ground to sorne suitable bearing stratum below. Some foundations, both surface and buried, have been designed to allow for remedial maintenance as movements take place during thawing of the frozen ground.

In some cases it rnay be econornical to excavate cornpletely srnall islands of frozen ground underlying a structure and backfill with sultable non-frost-susceptible rnaterial, thus eliminating problerns due to thawing. Sorne Lrozen materials are relatively easy to excavate using normal construction equiprnent and this foundation technique should not be over - Iooked. Thawing of frozen ground can be accelerated by removal of the insulating rrloss cover to expose the underlying material to the natural elernents. This method is very slow and generally not effective to depths exceeding, sdY I0 ft - the rate of thaw decreasing with depth. It has been found at Thornpson that some areas that were underlain by perrnafrost to depths of about l0 ft and were stripped of all surface cover were free of perrnafrost within 2 to 3 years.

Drainage is a rnost irnportant factor to be considered. Surface pools of water and percolating ground water can have a slgnificant effect -48 -

on thawing of frozen ground. They can also result in rnost difficult foundation conditions. As has been indicated previously, perrrrafrost is normally found adjacent to or near low-lying areas usually under a fairly thick rrross cover which has great water retention capability and may be saturated or near saturation. As a rule natural drainage should not be disrupted but in some instances water courses rnay need cleaning or improvernent or even re-alignment. Great care should be taken to ensure adequate drainage of water resulting frorn thawing of permafrost bqdies.

VI. SUMMARY

Thompson, Manitoba, is located in the southern fringe area of the permafrost region. PerenniaLly frozen ground occurs as scattered small patches or islands varying in areal extent frorn about 20 ft to several hundred feet and in thickness from about 3 to 30 ft, or greater (average thickness is between 8 and l5 ft). Perrnafrost is encountered from l8 in. to 7 ft below the ground surface. Much lce, prirnarily in the forrn of horizontal lenses from hairline to 2 or 3 in. in thickness (rnaxirnurn thickness observed is about 9 in. ), is found throughout the frozer. lacustrine soils underlying the area. Ground ternperatures close to thawing (32'f') indicate that the frozen ground is in a delicate state of therrnal equilibriurn.

The existence of perrnafrost in this area is greatly influenced by local climatic and terrain features but because of their complex inter- relationships, the occurrence and distribution of perrnafrost is not readily predictable. The effect that these features have, either lndivldually or in cornbination, can only be evaluated qualitatively. Certain combinations of vegetation, relief and drainage characteristics do provide, however, a fairly reliable rneans of predicting the occurrence of permafrost. Cllmatic factors, e. g. air ternperature and precipitation (snowfall) asslst ln the assessfirent of perrnafrost conditions.

Engineering problems associated with construction in this fringe area of perennially frozen ground arise mainly because of the relatlvely unpredictable distribution of the perrnafrost ttislands,Itthe quantity of ice contained in the soils and the critical, rrnear thawingttcondition of the frozen ground. The need for adequate site investigations cannot be overemphasized. -49 _

RET'ERENCES

i. canada. The cllmate of canada. Meteorological Branch, Dept. of Transport, Ottawa, 1960, T4p.

z. Haurwltz, B. and Austin, J. M. cllrnatology. McGraw-Hill co. rnc. , New York and London, 1944, 410p.

3. Putnam, D. f'. et al. Canadian regions. J. M. Dent and Sons (Canada) Ltd., Toronto and Vancouver, 195?, 60Ip.

4. stockwerl, c. H. , ed. Geology and economlc minerals of canada. Economlc Geology series No. r, Fourth Edition, Geological survey of canada, Dept. of Mines and rechnical surveys, L957, 5I7p.

5. Wllson, J. T. Geophysics and continent"l g"owth. Arnerlcan Sclentist, Vol. 47, 1959, p. I -24.

6. Lowdon, J. A. Age deterrnlnations of the Geological Survey of Canada. G. S. C., 1960, Paper 60-t7.

7. Wilson, H. D.B. and Brlsbin, W. C. Regional structure of the Thompson- Moak Lake Nickel Belt. The Canadlan Mining and Metallurglcal Bulletln, Vol. 54, No. 595, November 1961, p. BL5-BZZ.

8. Elson, J. A. Lake Agasslz and the Mankato-valders problem. Science, Vol. l26, No. 3ZBI, l5 November 1957, p.999-l0OZ.

9. Elson, J. A. solls of the Lake Agassiz region. In soils of canada (Ed. by R" F. Legget). The Royal Societli6f Canada, Speclal Publicatlons No. 3, 196I, p.5l -29.

I0. Hardy, R. M. and Legget, R. F. Boulder in varved clay at steep Rock Lake, Ontario, Canada. Bulletin, Geological Survey of America, Vol. 7I, January 1960, p.93-94.

11. Mclnnes, Wllliarn. The basins of Nelson and Churchill Rivers. Geological survey of canada, Dept. of Mines, Mernoir No. 30, l9r3. lz. wright, J. F. Geology and rnineral deposits of a part of northwest part Manitoba. Summary Report for 1930, C, G. S. C. , Dept. of Mines, l9 3I. -50-

13. Rowe, J. S. Forest regions of Canada. Dept. of Northern Affalre and National Resources, Bull. IZ3, Ottawa, 1959, 7Ip.

14. F1int, R. F. Glacial and pleistocene geology. John lvViley and Sons, Inc. , Copyright, 1957.

I5. Eden, W. J. A laboratory study of varved clay frorn Steep Rock Lake, Ontario. American Journal of Science, Vol. 253, November I955, p.659-674.

16. Deane, R. E. Geology of Lacustrine clays. Proc. l4th Canadian Soil Mechanlcs Conference, October, I960, Natlonal Research Council, Associate Commlttee on Soil and Snow Mechanics, Tech. Memo. No. 69, June 1961.

17. Fraser, H. J. An experimental study of varve deposltion. Trans. Royal Soclety of Canada, 3rd Ser., Vol. 23, Sec. 4, 1929, p.49 -60.

' 18. Skernpton, A.W. The colloidal rActivltyr of clays. Proc. Thlrd International Conference on Soil Mechanics and Foundatlon Engineering, Vol. I, 1953, p. 57 -6 1.

19. Terasmae, J. Notes on Late-Quaternary clirnatic changes ln Canada. Annals of the New York Acaderny of Sciences, Vol. 95, Art. I, October I961, p" 658 -675.

20. Legget, R. F. et al. Permafrost investigatlons ln Canada. Geology of the Arctic, Vol. II, 1961, p.956-969.

ZL. Brown, R. J.E. The distribution of perrnafrost and its relation to air ternperature in Canada and the U. S. S.R" Arctic, Vol. 13, No. 3, September I960, p. 163-I77.

?2. Canada. Clirnatic summaries for selected meteorological stations ln Canada. Addendum to Vol. I, Met. Branch, Dept. of Transport, Toronto, 1954.

23. Canada. Ternperature and precipitation normals for Canadlan weather stations based on the period IgZl-50. C. I, R. 3208, C. L. L 19, Meteorological Branch, Dept. of Transport, June 1959.

24. Thomas, M. K. Clirnatological atlas of Canada. National Research Council and Dept. of Transport, Meteorological Branch, Ottawa, 1953, 253p. NRC 3I5I. -51 -

25. Thompson, H. A. Eteezing and thawing indices in northern Canada. Proc. First Canadian Conference on Perrnafrost, Natlonal Research Councll, Assoclate Comrnittee on Soll and Snow Mechanics. January 1963, TM 76, p. l8-36.

BIBLIOGRAPHY

Antevs, Ernst. Late-glacial correlatlons and tce receseion ln Manitoba. Mernoir 168, G. S. C., Dept. of Mines, Ottawa, 1931.

Johnston, W, A. Reconnaissance soil survey of the area along the Hudson Bay Rallway- Summary Report, 1917, Part D, G. S. C. , Dept. of Mlnes, Ottawa, p.250 -360, I918. 'Ivl/illlam. Mcl:rnes, Explorations along the proposed llne of the Hudson Bay Railway. Summary Report of the Geological Survey Dept. of canada for the calendar Year 1906, sesslonal paper No. 26.

Ritchle, J. c. The vegetation of northern Manitoba - I. studles ln the southern spruce forest zone. Can. Journal of Botany, Vol. 34, p.523-561, 1956.

Ritchie, J. c. The vegetation of northern Manitoba - v, Establlshing the rnajor zonation, Arctic, Vol. 13, No. 4, p.Zll-229, December 1960. TABLE I

CLIMATIC SUMMARIES FOR THOMPSON, I,VAEOWDEN A-i'ID GILLAM, MANITOBA

(a) Moothlv average of dailv mean air lemperatures ("F) (b) Averagc mouthlv plecipitation (in. )

Jan. Feb. Mar, April May June July Aug. Sept. Oct Nov Dec Yeaa

Wabowden 0_65 0. 52 voz 0.8l 1.38 3.05 3.21 2.45 I. 02 0.85 0.61

Thomps on 0. 3l 0.40 0. 89 0.94 t. 43 t. 9'7 2.t0 t. 24 z- 54 r.99 t45 l. 38 l6 64

GilIam o.46 0.39 0. 67 0.60 098 I. ?l 368 2.49 2.45 1.09 105 0.86 t6.44

(c) Ave!age monthlv rainfall (in. ) (d) Average monthlv snowfalL (1n. )

Wabowden 6.6 5.2 o. u (.2 t.4 0,9 0 0 0. I 3.9 6. I 45.6 Gillu 6.6 3.7 u. ) 0 0.03 0.8 5.8 10.5 8.6 50.3

(e) Normal monthly depth of enw on groud (in. )

Wabowden (2) qilldn

SmalleEt l3 l5 0 0 8 Largest 36 45 39 34 8 lo z6 Media zl zz z1 6 IO

Mean zz 25 23 x t t0 I8 TABLE II

AGE OF' TREES AT THOMPSON, MANITOBA

High Areas Low Areas Transition Areas

Specles Trunk Age Species Trunk Agu Species Trunk Age Dia (yr) Dia (yr) Dia. (y") (in. ) (in. ) (tn. )

Spruce 4+ 55 Spruce z 60 Spruce z+ 66

Jackplne I 59 Spruce 2+ 39 Spruce 3* 40

Jackplne T4 62 Spruce zi 42 * Birch 6 54 Spruce 4 50 * Blrch 9 61 * Poplar 6 56 * Poplar lt 6z

* Ring counts by Department of Forestry, Ottawa TABLE III

ATTERBERG LIMITS AND GRAIN SIZE DiSTRIBUTION

FOR NINE SELECTED S.AMPLES

THOMPSON, MANITOBA

Soil Description Depth LL PL PI SL SR lo CIay % silt

Light grey layer z5 28.z 18.3 qa z6 74

Light grey layer z0 32.0 r9.8 LZ.Z 20. 0 t.73 z6 74

Dark grey layer z5 70. 3 zz.6 47.7 90 l0

Dark grey layer z0 63.6 24.3 39.3 17. Z L. 82 80 z0

Dark brown layer ll 6I.I 25. L 36.0 18. I l. 80 9Z 8

Dark brown clay (unvarved) 58.9 20. 3 38.6 83 I7

Dark brown clay (unvarved) 68. 5 z7.7 40.I 19.4 t. 78 87 l3

Combined brown varved II 42. I zL. 0 ZT.T 18.0 l.8t 63 37

Combined brown varved l0 >1. ( zz.7 29.0 I8. I I. 82 58 3Z COMPARISON OF PERMAT'ROST DISTRIBUTION AT THOMPSON AND OTHER CANADIAN STATIONS

(a) PermafroEt DlEtr{bution at Thompson Compared to Other Statioae Having Slmilar Meaa Annual Air Temperatures

Years of Observations P ermafr ost Distributlon

Aishihik, Y. T. 6I'39'N; I37'28'W Wldespread, maximum thickness reported - 90 ft Fort Slmpson, N. W.T. 6I'52'N; I2l'ZltW Patchy, with variable thickness to 40 ft Fort Providence, N. W. T. 61'20'N; ll7'40'W Patchy Hay River, N. W. T. 60'5I'N; lI5'46'w Patchy with variable thickness to 40 ft Thompson, Man. 55'36rN;98"42tW Patchy with variable thickness to about 40 ft Fort George, P. O, 53'50tN;79'05rW No permafroet reported Nitchequon, P. O. 53'l2rN; 70"35rW No permafrost !eported

(b) Permafrost Dietributlon at Thompeon Compared to Other Stations Havlng Slmilar Freezlng Indices

Elevatlon Years of Thawing (ft above Observatlons Index Permafr ost DiEtribution sea level) (degr ee daye)

Cape Hopes Advance, P. Q 6I'05tN;69'33'W Continuous permafroet, several hundred feet thick Thompson, Man. 55'36'N;98"4}w Patchy with variable thicknees to about 40 ft Hay River, N. W. T. 60'5I'N; lI5'46'w Patchy wlth variable thickness to 40 fr Fort Smith, N. W. T. 60'0I'N; Ill'58'w No perrnafrost reported

(c) Permafrost Distributlon at Thompson Compared to Other Statioag

Hawing Slmllar Thawing Indicee

Mean Annual Years of Alr Temp. Observatione Permafrost Distribution (.F)

Yellowknlfe, N. W. T. 62'28fN; Il4'Z?tW )2 q l0 Widespread, maximum thickness about 250 ft Thompson, Man. 55'36f N; 98" 4ZtW 24.9 4 Patchy with variable thicknese to about 40 ft Hay River, N. 1f. T. 50'5I'N; ll5'46rW 24.7 2Q Patchy with variable thicknese to 40 ft Fort Reeolutlon, N. W, T. 6l'l0rNr ll3'4lrW 23.? zz Patchy with variable thickness to 410 ft o T \f :lq s t -\ s J 3J : -l s r o I d Ig I I 2 - I u\ - e t z = I Jo{ o I I a -t z, F o ct) o- = o - F

Lt o z, I t- (J o -.!

lrj E = I lr- o = o =, F AIRSTRIP

D.O.T.NON DIRECTIONAL ,'--'.. BEAcoN ( I SITE t. z - a-r-l \ GRAVELHrLLg,/ j 750 F00T .. \ coNTouR \ -t \ \. - -. t...-. r\ .a --r-^ .-:i

ACCESS ROADTO MOAKLAKE

CEM ETE RY

trA PUMP / MANASAN HousEI RAPIDS(4'} l9,t WESTWOOD SUBDIVISION -€SEWAGE TREAT-/ o-MENT PLANT-/ t,- WATER HYDROLINE IREATMENT '?'iyz PLANT

TROPOSPHERIC -'-'-;I SCATTERRADIO STATION CNRTO HEAVY SIPIWESK IN DUSTRY

INTERNATIONALNICKEL CO.PLANT SITE

THOMPSON,MANITOBA

t/? | SCALE IN MILES

FIGURE2 PLAN OF TOWNSITE AND PLANTSITE,THOMPSON,MAN I TOBA

8P 28/4 - J LEGEND --- APPROXIMATESOUTHERN LTMIT OF CONTINUOUSPERMAFROST - APPROXIMATESOUTHERN LIM]T OF OISCONTINUOUS PERMAFROST

\.+ R =-,\

,,

THOMPSON \ lr \: ..:

r.)_ FIGURE 3 I. DISTR I BUT ION OF PERMAFROST r00 0 r00 200 IN :TE CANADA MILES JUNE1962 DBR,/NRC

8R 28t4-l FIGURE L 4 I MEANANNUAL AIR TEMPERATUREFOR I CANADA( DEGREES FAHRENHE IT) DIVISIONOF BUILDINGRESEARCH, NATIONAL RESEARCH COUNCT/ ANDTHE METEOROLOGICAL BRANCH, DEPARTMENT OF TRANSPORT,CANAOA. I953

8f, 28t4 - 4 at lrJ c60 E :- (J lrj = 5s0 a'2, F o E t^, 40 MEAN ANNUAL AIR o- F = TEMPERATURE 14, g *Jo -c) J TTJ E E a o- 120 J :E F F o F 3ro 2> = J r z. F z, fl0 o = = -t0 .2, l< lrJ ANNUALTOTAL PRECIPITATION = r6.64 TNCHES

-30 JAN FEB MAY JUN JUL AUG SEPT OCT

FIGURE5 MEAN MONTHLYAIR TEMPERATUREAND MEAN MONTHLYTOTALPRECIPITATI ON FOR THOMPSON,MAN rT0BA( t958 - l96t lNCLUStVE

8R 28t4-5 6Jea 8$

;-"J T \ I \. (. I \: - -l FIGURE6 SOMEFREEZ ING INDICESFOR CANADA ( r00 0 t00 200 FAHRENHEIT DEGREE DAYS ) =:r: MILES AFTERH. A. THOMPSON DEPTOF TRANSPORT t962

0R28/4-6 ""*,

\./

\ qil \l: -i .l ; FIGURE7 SOMETHAWING INDICES FOR CANADA t00 0 t00 200 (FAHRENHEIT --E: DEGREEOAVS) MILES AFTERH.A. THOMPSON DEPTOF TRANSPORT t962

8R 28t4 - 7 -7J 't--=.-t |! o <'- --. ft Huo );E F Eqo lrJ c = H30 = I20 4 o Eto z, *r'

14, =0 t LEGEND I WAEOIII'OENMANITOEA il944-6D - )o -10 7t THOMPSONMANITOBA (t958-6tl---- J$, GILLAMMANITOBA (t943-61) ,, -20

12345 MEANMONT.HLY TOTAL PRECIPITATION (INCIIESI

FIGURE8 HYTHERGRAPHSFOR WABOWDEN,THOMPSON ANDGILLAM. MAN ITOBA

8R28t4 -8 BOUNDARYOFCANADIAN SHIELD GNElSSICTRANSITION ZONE DIVIDING CANADIANSHIELD PROVINCES

NORTHWEST TERRITOR IES o --.2 oo-f - HUOSONBAY MANIToBA V CHURCHILL

,".,"^.

ffi^nar*SHIELDPROVII{CES . 2r .- /-l /

%... tilTEnt0R PLA IIIS '(a

SUPERIORPROVINCE SASKATCHEWAN \a ONTARIO WltlllPEG ./ I -"'i-"'Ei

FIGURE 9 SKETCHMAP OF MANITOBA SHOWING MAJOR GEOLOGICAL REGIONS

8naan-9 L EGEND HUDSONBAY EXTENTExrrNcT PLETSToCENE m lillt'" MAxtMUM s EXTENT0F AREASoF HURCHILL MARINESUBMERGENCE \ MAJoRMoRA|NES <- TRENDOF GLACIAL STRIAE MANITOBA DRUMLINGROUPS, GIANT GLACIALGROOVES ETC

s0uT I[0tat{ SASKATCHEWAN \\ N

\\ 2 ?2, t4 '61 \

ONTARI O

\ t\\

rf]xq.h*\D* \qn \I[/

50 0 50 too 2oo u's'A' SCALEIN MILES

FIGURE IO GLACIAL MAP OF MANITOBA SHOW ING PERTINENT FEATURES OF THOMPSONAREA ( Ffl2li,f GLAC|ALtlAP 0F CAA\A7A- /958)

8P 28/4 - /0 LEGEND

:ara-GROUNDSURFACE CONTOUR LtNE Low AREA 0 O W Lor,trwtT AREA - DRAINAGECOURSE

_--- TOWNSITELIMITS

.99______9____-- o SALE IN FEET {)

@l . o Mb @- $"'tuW P>r o *q @

a90--- - f-istAP..\ \ \'' {l 0 \v/-\-J 0 &\_-.--^ I q,,-J s s ,700t G s \3 s t r- st \ N ) F:\'dp ^^

f4ou - pRov 0F uailiaSa pLtililtila SfRytcE oyc ila 67 70 /t2 K

FIGUREI I RELIEFMAP OF THOMPSON.MANITOBA iiiiii 't "t.'. ;'..:.?

Figure l2 - General view of terrain relief - gravel hill in background.

Figure 13 - Large gully crossing Thornpson Drive North near Lyn* Crescent. Figure l4 - Low, very wet grass-covered area between Westwood Drive South and Char Bay. Flgure I5 - Stagnant water lying between sphagnum hurnrnocks.

Figure L6 - Typical snow cover in dense spruce growth. 'i.,:,l ,

Figure l7 - Typical snow cover in open grass area.

- Figure l8 Typical tree growth on high area - predominantly spruce but sorne jackpine, birch and poplar. Figure I9 - Typical vegetation growth on low area - stunted spruce and sphagnum moss. Note ground temperature installation IT -ZZ, Char Bay area.

Figure Z0 - Change in vegetation growth through transition zone frorn high to low areas - sauger crescent, westwood subdivision. Figure 2l - Typical ground cover - trfeatherrrrnosses - on high area.

Figur e ZZ - Typical ground cover of sphagnum rrloss in perrnafrost area. Note thickness (about 14 in. ) of peat and sparse tree cover. SPARTANAIR SERVICES 23il - t30

FIGURE23 A I R PHOTOSHOWINGMAJOR RELIEF AND VEGETATI ON PATTERNS

bat 2at+ - 3, DEPTH DESCRIPTION RANGE

LIVINGMOSS COVIR (FEATHER OR SPHAGNUMI OVEROECOMPOSEO ORGANIC MATTER

DARK BROWNCLAY

BROWNVARVED CLAY SIZERANGE X rN LfGHTBRoWN CLAyEy SILT LAYERS - y8-ty4 OARKBROWN CLAY LAYERS -lz-1"

GREYVARVED CLAY SIZERANGE: LIGHTGREy CLAyEy StLT LAyERS. -vl-Ztti' DARKGREY CLAY LAYERS - I/Z-3"

SILTYSANDY GRAVEL

BED ROCK

FIGURE24 TYPICALSOIL PROFILE,THOMPSON,MAN ITOBA

BR 28t4 - t2 Figure 25 - Soil profile e>ryosed in] excavation. Note 12-in. surface layer of organic rnaterial overlying about 3 ft of dark brown clay, also distorted strata in upper layers of brown varved soil. Grey varved soil occurs in Iower third of e>cposure (large lieht lavers).

Figure 26 - Distorted strata in upper layers of brown varved clay - from 3 to 6 ft below ground surface - Sauger Crescent. MECHANICAI- ANALYSIS OF SOILS

roo

on

ao rF (, 70 UJ SILTYSAND 7 (4 SAMpLES,AFTER MATERTALS TESTTNG LABS) 60 o t l^J z (4 SAMPLES

F z U DESCRIPTION OF SAMPLE U E lrl AND GRAINS:- .L

GRAIN SIZE CLAY rrNe I I S[f I coansel rrre i\SaruO COARSE I FINE GRAVEL I coaFsE

M.I.T. GRAIN SIZE CLASSIFICATTON

FIGURE 27 GRAINSIZE ENVELOPESFOR THOMPSON SOILS

8R 2e4-B r0

A

A^ A 20

F A q A A - AA SAMPLESWITH M,/C AEOVE 45 % t! CONTAINEDMUCH SEGREGATED ICE aa a 30

LEGEND 40 A SAND SILT&,/OR CLAY- I SAMPLE a s ILT 8,/0RCLAY-2-3 SAMPLES o SILT8,/OR CLAY 4-7 SAMPLES

50 r0 20 30 40 RN OU 70 MOISTURECONTENT, %

FIGURE28 MOISTURECONTENT VS DEPTHAT THOMPSON,MANITOBA 7t0

700

690

680

A A A 670 a^ F AA AA u AA -A z. A -A A 9 660 A tt F . A A lrJ t' J o Ld -a 650 A

t A 640 A

AA LEGEND 630 A SAND . SILT8,/0R CLAY- | SAMPLE . SILT8/OR CLAY- 2 SAMPLES 620

6r0 0 r0 20 30 40 50 60 70 MOISTURECONTENT, %

FIGURE29 MOISTURECONTENT VS ELEVATIONAT THOMPSON,MANITOBA

8P 28tr -/5 SF trsF o F oSt o oo g I oF o I F ot oo E'l o to l4J o lrJ E - - t5 ogF F sF CL tr F UJ LEGENO oF o o tr DARK o O r Jo LIGHT oF OF o F FROZEN SF SEASONALFROST z5 F F II o

30 r0 MOISTURECONTENT, % FIGURE30 MOISTURECONTENT VS DEPTHOF SELECTEDSAMPLES FROM IND IV I DUAL LAYERS ,THOMPSON, MAN. 60

ol

a a rE tr.: LEGEN D o.' h tr CLAY .' trt 40 O SILT >< A- LINE lrJ . UNSPECIFIED o z,

= I U' a .tt J 4 .2' 20 '. t6.

a 'dc a 'o8 ( 92 SAMPLES)

0 100 LIQUIDLIMIT

FIGURE3I PLASTICITYCHART,THOMPSON SOILS

aR 2tt4-t7 7A

LEGEND 60 DARKLAYERS o LIGHTLAYERS o COMBINED tr BROWNCLAY A s.O o Q'2

>< trj 2+o o't'

: I bso ts7 J o- tr tr tr rt$!P tr

I t0

0 0 r0 20 30 40 50 60 70 80 90 loo PERCENT CLAY (<.002 MM)

FIGURE32 ACTIVITYCHART,THOMPSON SOILS (oAI o,

o

F

a

LrJ F a z. = o F z. o a o- = - F -lrJ F z.

LI O z. I t! z *", E o E .. U J = & (J =z= () E 1=- o =c; z = l! z JF il = sO oE :l ,=E _L E E= t! q== UE -o @U ; zo<= ZL ^-E oz ro - ;t: < Pl ro G;= tz Od-c dou t! F u=c E tq --i I = FFF FY oo= LL E Eli <

3?i'fii;fG

BOULDER 2V;xzv; \3t/;

@rez LEGEND rT-21

PERMAFROSTIN SERVICE- LINE TRENCHES o PERMAFROSTIN BORE-HOLE @ THERMOCOUPLECABLE IN BORE_HOLE Tx-t\ SECTIONIN TRENCHWALL WHICH FACES ARROW GROUPSOF LOTSON EACHOF WHICH5 HOLESWERE AUGEREDTO 20 FEET- NOPERMAFROST .. SHADEDSTREETS TO BE SERVICEDIN FUT URE

FIGURE34 PERMAFROST OCCURRENCE IN WESTWOOD SUBDIVISION ( T0 0cr0BER26, t962 )

aR 28/4-20 STURGEONCRES. -STORM SEWER

670

?.) -.i - -/> -., - - - -,. 7 -. :/-,7 > 7 7 / :

o LEGEND ilH 0-354= MANHoLEtlo D-354 PERilAFROST- ACTUAL --- APpRoxTMATEI h 650 L

9L-^ =v 400 DISTANCE,FT STURGEON.CRES.- SANITARY SEWER

670

- 660 z LEGE I{O il H S-359 =MANHoLE No 5-359 PERilAFROST- ACTUAL .-- APPROXITATE oESEFVATroNs-JULY t-5, t962 VERTTCAL (.r, r_ - rn.l- "---' HoRtzoNTAL

400 DISTANCE, FT MALLARDCRES.- SANITARY SEWER 670 ,,t% 3

F '- seo z

LEGEND MH S-404' MAilHoLENo 5-404 PERMAFROST- ACTUAL --- aPPR0XtMATE | * = oBsERvalroNs-FEBts. t96z I g S s g ,carr-fffiffi.=ro,, * | ' | , L | , | | l= 400 DISTANCE, FT

FIGURE35 PROFILEOF PERMAFROSTOCCURRENCE: WESTWOOD SUBDIVISION, THOMPSON,MANITOBA GROUNDSURFACE

LOGTX 16 GROUNOSURFACT o s6o

%@q )2)':,, i 6s0 n s-364T0 S-363-ilAY16-t7,t962 s-350T0 s-36r- JUNE29-30, t962 s-36r T0 s-363-AUG2t-25, t962 ^^.._ VERTtCAL.^ .

ilH S-360 MH 5-361 MH 5-362 MH 5-363 MH S-364 il H 5-365 til H.S- 3?0 I lr

SAUGERCRESCENT _ STORM SEWER L€GEXO r H 0-$5 ilAXHoL€to D-365 PERXAFROST- ACTUAL FIGURE36 .--. APPROXIXATE oESERVATrots- 0-t62 T0 D-57-ApRtL 9-t2, t962 PROFILEOF PERMAFROSTOCCURRENCE 0-362T0 0-359-ttY t-a, t962 vERTtCAL c.^rF_-'--- -,6.,- ' WESTWOODSUBDIVISION HoRtzotTAL THOMPSON.MANITOBA

MHD-359 MHD-360 ilH0-362 [f H D-363 l' H 0-365 U/)]tN D-366 tH D-367 Ll | , | , t | | , | , ! 500 400 300 200 t00 0 r00 200 300 400 500 600

GROUNOSURFACT

680

E szo (O)LOG TX 14 (b)LoG TX t5 TESCqIPTtON vLSCAtfitOrl 610.1 J9Z 50tL

WELLBON9EP 3"LrvlNG Moss NO VISI6LE 3 LrVrN6 MoSS r LC>5 ILL covEq ovE4 ICL sEGqLG. covEg ovLB ?ECOMPoSEV ATION DECoM?OSE9 oB64N tC oq6ANrc MATTEB ('EPT'1 GENEBALLY APP4OXIMATEI VE!L 6ON'L' MATTEB

F SMALL CBYSTAL5 AN' THIN COATINGS ON I rA5 | lerrt - ! VELL 6ONPE9 F z 6 0 (

a I z o

BROVNCLAY I v ITHOrt I INCLUSIONOF o86ANrC (\ M ATE4IAL IN I TOP 2' I

I8qE6ULABLY I OBILNTATEP VeqY rtue- (u t. to t/zz") 'qBE6ULABLY ,/a' IVU LLN5C5 OBIENTATEP gBoVN t/e,,, HOqTzoNTAL HAIBLINL ICL vaP,vLa LEN6E6 t/4 A5 SHOVN CLAY t/a Vs '/8 soNvou )1i

v; HORIZONTAL LENSES t/e A3 SHOVN VB yi' ,/z

:/A

t/+ r/+ BROVN '/a" ^,^, VARVEP CLAY r+ l/2 rcL vrTu o0? cL l INCLUSTON /+ 3h' /; V+' -/a t/4',,, '/2 t/^"

i'/a t/+ >Y+' ,,,

-/4 ,A ,d, t" ,14 goffoM - 't/a' SECTtON EI{,

ife GBEY VAqVE' 9!4Y VEqY MoIf LLe APPEAq,ANCL goTroM 0F SECTtOr.l-EN7 !FqozEilMATL

MALLARDCRESCENT SANITARY SEWERTRENCH MALLAROCRESCEI'IT SAN ITARY SEWER TRENCH ( STATt0N2 + 03 ) FEBt5, t962 (STATr0l{5+00 1 FEBt6.t962

F]GURE37 LOGOF SOlLSAND PERMAFROST, WESTWOOD SUBDIVISION THOMPSON,MAN ITOBA tol Luu lx 5 (0t LOGrx t6 vLscgtPftof ?EScBtP'rtoN br4G 662.O I ct- 50tr- LrvrNGMoss covES LIVINGMOSS ovEBtEcoMPoset covLB ovlq oecoMPosL9 OqCANICMATIEq NOT oq6AN r c MATTLB

WELL gON'E' d OBSEBVEP ?AR( BBOVN L . BANDOMHAIqLINE qlAY J ICL LENSLS THqOU6HOUT DAR( BROVN o CLAY ql VELL 6ON9E", MAINLY INVISIgLE TO EYL- RAN'OM $ H L ICLTHqEADS

LIGHTLAYEBS NUMSER./ H L. N ?OZLN th" -t" THBEA9S4 VELL AON'E9-ICE NOT rNcLustoNs 'AB( LAYEqS INCBEA9EVtTH D!PTJ,I '/t - MoqL rcE vtSrSLE vz" IN LIGHTLAYEBS THAiI rrl rA96 48. LTGHI_ 3i _tye" t/d i*,r-'/a'-'/z^ ueut - t4^- t" ICL VITH SOIL TNcLUSTONS ?E?TH- y2"

fgouNDAq,rEs"/ LI6HT eAB( .{ 4 LIGHT t/a i LAYEqs,vEqY -arqr % \ IBBE6U LAB /2. Yi d %e BBOVN VAqVED q.!:.AY LtcHr 4. IN OAA( LAYEBS 'AqK LAYEBs yi INCBE46LIN ICE SEGBEGATION t/d THrC{NESsWrTH A6 SHO\r'N PEPTq BANTOMH L ICL 2/6 LEN5E5 THqOU6HOU] tc.L l5 SoFTtSoDNO t/a",, ' CLLAD, t/a' 1 '/a I t/2;' I t/+ I y4,,, I -/E ALL rCL LENSES 14 I Yei 1/4 I IN DA4( LAYEqS t/a

V4' va t/4' va", t/8 '/+ t/a' - /a tteut l'- lt/2 LIGHT 4 - t/2" OAqN . 3/i '/8 D^qt< v; r/,' €oML iloqnolITAL . ICE- LENSE€ 3,/" .soeup 1o tVi' 3/a LICHT LAYEq€. e/i,,, , tcY[ \ HA9,0 Fq,OZeN, / sorL 6TRA1A\ 'AB4 LAYEBS I TTSTOq,TEPAT ' '/4 ?EpTH5l/ SOFTLq \soML

t/a borTou '7 ECT I ON

Tqozzu 1o 14

SAUGERCRESCENT SANITARYSEWER TRENCH ( ilANHoLES - 365I APRrL5. 1962

SAUGER-RAINBOWCRESCENT EASEMENT STORM SEWERTRENCH (I2.NORTHOF MANHOLEO-365} APRIL7. 1962

FIGURE38 LOGOF SOILSAND PERMAFROST, WESTWOOD SUBDIVISION THOMPSON,MANITOBA LIV'NG MOSS covEB ovEB t/tk ?ELO\4PO3!-0 /+,: -'"-^ Oq6ANIC MATTEq - vr:" rq=t. ,1, ;,i# t,2 .4 ,. , 2V; s vl . "14 v2n \VELL gOI.IVEP EY rce NoT ?)l4_,. VISIELL TOTI{E ,/A ,r' t6 o99 H.L. Tq,EEGULABtCL l\ %,;: LENS. v;..16 '/b' ' l/+ l'/+ B lr; th h '/z

NO. OF FINE /,T LENFE5 INCREASES i "rf,;;fiz7 2/a TVITH PEPTH | t4: V2" ,n ,,{n 26 1/a ', -/8 a5 aoove BUT S|ZL.f cLAy NO?ULE6 INCQTASES , 214" to,t/i-t/A x I t"27- yt' 7 eePTrl. I z2f"r -^'r2'ir- bollott / .t/. PEqMAtq0sTSEcTroN *- To 29 rl.

GqAP!AL C{A[GL LEGEilD TO BBO$/N VAAVF-O CLA! DARKLAYERS -tz t-otar Yoi:Vi s^qA rt-f LIGHTLAYERS rcE -r BBOVN VABVE? CLAY

LIGHT LAYEB€ Yi'-Y+'

trr'*r- td ?AR4- 3/4"-t"

BANTOM tcE- gqovil vAqvEt LLNsE-€ - ye,t CLAY CHANGES THIcI,{. MAINLY 5U8TLY 6BEY vzqliLa,t 3"-j" TO LON6-SOME- VAqVEP CLAY nqe z'cor.ta

GBEY VAqVE? CLAY

VELL PEFINeT VABVEg

eofiou "f

WESTW00D0RIVE S0UTH WATER Ltt'tE TRENCH (STATt0Nr8+70 I aPRtL3, t962

FIGURE39 LOGOF SOILSAND PERMAFROST,WESTWOOD SUBDIVISION THOMPSON,MANITOBA LOGTX 4 DESC 0 0 I JCE- SatL- LIVING MO6S covER oveq v; oz.otlposLv o46AN'C MATEB'AL 4

NOT t/+ ,F-P GBEY VABVE' 4 OgSLB /2 g.!_AJ

/venu ./'uNe a,sor..t,a.r-\ EqTAIN \ Fnosr J LIGHT I ?AqK LAYEBSABOUT EqUALTHICgNESS - up 1o 1,, y;' v; t4 4 MEDIIJM 3A BEOVN OLAY A5 ABOVL 9UT HAIBLINg ICL LEN5E5 - vrTH ?ABl,( FEVEB H L. -rENseLY 6RouPet BBovN cLAY z"(>tr' LEN€E6 -BANTOM pr5T- N O' ULLS v;' - B | 9uTroN (srzt ll,-'/i ) swttt y4" LtcAI lt/z" -soML THIN tCL PED'LEg vsn4 - t/2,' COATING€ ON vEq& FouNt sAMPLE PABK BBOWN IN ICL LENsLs LII

tcE sE6qE6ATtON A5 SHOVN - BAN'OM H L ,/f'*l/2" LENSES uoq tq,EE6ULAqLY %r2" vEAl. OEILNTATET l0 O-t/+"cIAs. l|,e (BETVEeNk'qcs. ICL LENsEs pAB|() ABL SOUNP -tAt 50FT CIEAB - t/+" + )/)/ fr v;' v; BBOVN VAqVED t2 1 CLAY CHANGES yi str.us GBEY VABVEP ? g.!AY

-L+_ 4 _ _ trcfi 4 onq4-2" - '/E SEAM5 CqEY VABVEP ZTE___ 'AB( LAYEB9 ABL SECTION Yi GENEBAILYTHICSES '10 THAN!t68T, AS NoTE' ?LP,M^FqoST > 30 FT. abovL - To 16

LOG CO INUEP ABOVE. WESTWOODORIVE SOUTH TVATER LINE TRENCH (STATt0r{19+40 I APRTL4,t962

FIGURE40 LOGOF SOILS ANDPERMAFROST,WESTWOOD SUBDIV ISION THOMPSON,MANITOBA

BP 28t4 - 26 SECTION OESCR IBED

- ICEWITH SOIL INCLUSIONS

rll ICELENS

- y;' rcELENS t FIGURE4I ICE SEGREGATIONIN VARVED CLAY. PARTIALSECTION - LOGTX 16, SAUGERCRESCENT - MANHOLE s-365 Bq 2at+ - ?6 Figure 42 - Permafrost exposed in water line trench on'W'estwood Drive South. Note nurnber and thickness of ice Iens es. IC MAT1ER

LIGHT EROWNCLAY

SROWN VARVEO CLAY

bt0 U G IRANSITION.SROWil TO GREY VARVEDCLAY F c Hrs

GREYVARVEO CLAY APRIL 23

H0LE BORED: 5 - 9- 6l THERNOCOUPLEINSTALLEO: 5-9-6I NO FROZENMATERIAL

FIGURE43 SOILPROFILE ANDTYPICAL GROUNDTEMPERATURES BOREHOLETB 4 (cA8LEtr-23 )

TEMP (oFl --r 30 t96 JUNETJULY

O ORGAilICilATERIAL ilEDTUMr0 oaR|(8Ro{ril CLAY

_8ROWN VARVEDCLAY

i! l0 U u -- GREYVARVED CLAY F c Hrs

EOTTOMOF HOLE

HoLE80RE0 5-9-61 THERMOCOUPLEINSTALLEO 6-9 -6I NO FROZENIJ|ATERIAL

FIGURE44 SOILPROFILE ANDTYPICAL GROUND TEMPERATURES BOREHOLETB 5 ( CABLEIT -241 TTMP (OF} 30 40

I Jr[l rre I uln llpntl uavl,ruHel,rulv I aue lsrprl ocr I lov I oecI Jl[ | Fto I GROUiIOSURFACE - - SPHAGflUil MOSS LIVII.IG 14 /.4/rtrf:, ||0 JUlY5 - 0EcoilPosEDoRGAr{|C ,t,$ : HATERIAL T8 I I ! ,b I Y ,, - BRoWt'rv^RvE0 cLAY CD ocT25 {- 1 bro I U r -GR€Y 827 VARVEOCLAY aI - F c Hrs VARVES.LIGHT-A8OUT I" THICK I OARX-A80Ur 7r' IHICx F 2f MA 7 B JULY\l

BOTTOMOF HOLE 2t HOLEBORED 2-9-5I THERMOCOUPLEINSIALLED 2-9-6I I{O FROZENMATERIAL

FIGURE45 SOILPROFILE ANDTYPICAL GROUND TEMPERATURES BOREHOLETB 3 (CABLEIT-221

IEMP (OFI 30 40

rrl I rrg I manlrpntl uaylluHEl"rurv I auo lsEprl ocr I HovI oecI JANI FEBI

SPHAGNUMMOSS. LIVING DECOiIPOSEOSPHAGNUM AND ORGAiIICMAIERIAL \MEOIUM TOOARX SROWt.I CLAY A FEYVSMALL ICE CRYSTALS AI 4 AND5 FEEI SROIVI{VARVEO CLAY rcELENSEs -up ro 7i rrrcx EEGINAT 6 FEET Ero FEB27, trlAY7 I oCT I B _GRTY VARVEOCLAY r' F RAIIOOMICE LEt{SES c rHRouGHouT-up ro d rxrcx Hrs

EOTTOiIOF HOLE

HoLEB0RE0! t-9-61 THERMOCOUPLEINSTALLEO: I -9 - 6I |Im FROZET'IMATERIAL

FIGURE 46 SOILPROFILE ANDTYPICAL GROUND TEMPERATURES BOREHOLETB 2 ( CABLEIT.2I } TEUP (OF} 50 40

|,nil | reg I Nanlapnrr-l ilAy I JuilEllulv I lue lseprI ocr I rov I orc | ,ranI ree I Nov5 /nAY7 GROUiIOSURFACE o Moss- LtvtilG E8 ORGAiIICTITERIAI. JULY3 FROZEN

tcE LENSESFRoM %; T0 7r' rHtCx RANOOiILYSPACED

GREYVARVED CLAY

rc€ LEilSESrROM zc' TO t" lNtcx

EOTTOTOF HOLC

HOLEBOREO: 7-9-6I THERMOCOUPLEINSTALLEO: 8-9 -6I 0lnmFRoZEfl MATERTaL

FIGURE47 SOILPROFILE ANDTYPICAL GROUND TEMPERATURES BOREHOLETB 7 (CABLEIT-26 )

TEMP {OFI 30 40 t962 llallFEBluanlapRrr-lurvl,rurirl,ruuylauclseprlocrlHovloecl.ratliEel

SPHAGNUMMOSS - LIVING DECOMPOSEDORGANIC TIATERIAL RANDOiltCE LENS€SUP rO d FROMI FI OEPTH

BROWNVARVED CLAY rcELENsEs upro 7i rxrcx

ru1'- rcE LENSESUn r.O %' THtcx SPACEDABOUT I" APARTBEGII{ AT t0 Ft GRIYVARVEO CLAY

rcE LEirsEsFRoM l/ro' - lri rxrcx WITHRAiIDOM LENSES AEOUI % THICX- SPACEOABOUT I" APART

VARVES- LIGHI - AEOUTI,. oaax- reourli

SOTTOMOF HOLE

HOLEEORED: 7-9-6I THERMOCOUPLETNSTALLEO: 7-9 -6I m FRozENMATERTAL

FIGURE48 SOILPROFILE ANDTYPICAL GROUND TEMPERATURES BOREHOLETB 6 ( CABLEIT.25 ) LEGENO

. PERMAFROST-TEST-HOLELOGEXAMINED O PERMAFROSTREPORTED ON LOT- LOGNOT AVAILABLE ^ PERMAFROSTSUSPECTEO FROM BUILDING PERFORMANCE \\\\\\\APPROX IMATE PERMAFROST DISTRIBUTION UNDER BUILDING PERMAFROSTREPORTED IN SERVICE.LINETRE X BOREHOLELOCATION - NO PERMAFROST VEGETATIONAND REL IEF

,.,../... MAJORBOUNDARY BETWEEN DIFFERENT VEGETATION COVER- HIGH ! LOW t ALSoHrGH AND LoW AREAS (AppRoXtMATE oNLy) /,

I ,,'' J

I I

I L--

Ti\-

1 \ s ; --l = L

FIGURE49 PERMAFROSTOCCURRENCE AND GENERAL RELIEF AND VEGETATION FEATURES, THOMPSONTOWNSITE LEGEND

O PERMAFROST-TEST-HOLELOGEXAMINED O PERMAFROSTREPORTED ON LOT- LOGNOT AVAILABLE ^ PERMAFR0STSUSPECTED FR0M BUlLDll'lG PERF0RMANCE \\\\\\ APPROXIMATEPERMAFROST DISTRIBUTION UNDER BUILDING PERMAFROSTREPORTED IN SERVICE-LINETRENCHES X BOREHOLELOCATION - NO PERMAFROST *4'a_ GROUNDSURFACE C0NTOUR LtNE

' ^irRN

I

.a5

.q0

.q5

I noo

FIGURE50 PERMAFROSTOCCURRENCE AND GROUND SURFACE CONTOURS, THOMPSON TOWNSITE