Inuvik, N.W.T. engineering site information

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Inuvik, N.W.T. engineering site information

Ser TEl . N2Lt2 nr. L35 e . 2 BI,DG

NAT IONAL RESEAR CH COUNCIL CANADA

DIVISION OF' BUILDING RESEARCH

T e c h n i c a l P a p e r N o . 1 3 5 o f the D i v i s i o n o f B u i l d i n g R e s e a r c h OTTAWA A u g u s t 1 9 6 2 I N U V I K , N . W . T .

ENGINEERING SITE INFORMATION b y

J . A . P i h l a i n e n

(with a supplernent by D. W. Boyd)

P R E F A C E

M e m b e r s o f t h e D i v i s i o n w e r e p r i v i l e g e d t o s e r v e o n t h e s i t e s u r v e y t e a r n w h i c h c a r r i e d o u t e x t e n s i v e i n v e s t i g a t i o n s i n 1 9 5 4 i n the M a c k e n z i e R i v e r d e l t a a r e a i n t h e s e a r c h f o r a n e w s i t e f o r the settle-r n e n t of Aklavik, N . W . T. M u c h information o n site conditions and terrain f e a t u r e s a t E a s t T h r e e ( a s i t w a s t h e n r e f e r r e d t o ) w a s c o l l e c t e d p r i o r t o a n d following the selection of the present townsite of Inuvik in August

1 9 5 4 . T h e r e s u l t s o f t h e s e i n v e s t i g a t i o n s , w h i c h a r e o f i n t e r e s t t o e n g i n e e r s , a r e s u m r n a r i z e d i n t h i s p a p e r a n d i n c l u d e o b s e r v a t i o n s on s o i l a n d p e r m a f r o s t _{c o n d i t i o n s , d e p t h o f t h a w , g r o u n d t e m p e r a t u r e s a n d} g e n e r a l t e r r a i n f e a t u r e s . _{I t i s h o p e d t h a t i t w i l l b e o f u s e i n f u t u r e} p l a n n i n g f o r a n y p r o p o s e d e x p a n s i o n a t t h e s i t e . O n e o f t h e r e s p o n s i b i l i t i e s _{u n d e r t a k e n b y t h e D i v i s i o n a s a} c o n t r i b u t i o n to northern developrnent has been the collection and publi-c a t i o n of engineering site inforrnation on northern settlements as the o p p o r t u n i t i e s a r i s e . _{T h i s r e p o r t s e r v e s t o h e l p f i l l a n o t h e r g a p i n t h e} l i r n i t e d amount of information a v a i l a b l e on northern site conditions.

T h e a u t h o r , n o w i n p r i v a t e p r a c t i c e , w a s f o r t e n y e a r s a

r e s e a r c h o f f i c e r w i t h t h e D i v i s i o n , e n g a g e d o n studies of northern terrain a n d a s s o c i a t e d e n g i n e e r i n g p r o b l e m s .

Ottawa

A u g u s t 1 9 6 2

. R . o b e r t F . L e g g e t , D i r e c t o r .

TABI,,E OF' CONTENTS LOCATION. . . . H I S T O R Y . . . G E O L O G Y . . . CLIMATE RELIEF. VEGETATION SOILS P e a t ; Or ganlc Material.

B r o w n Gravel with Sand, Sllt or CLay G r e y Gravel F i n e Gralned I c e . S o i l s . L a y e r ) L a y e r ) P a g e l 3 L 4

r 5

t 5

r 6

1 8 1 8 I

t

z

3

6

6

7 I

9

l t

L Z

DEPTH OF THAW (ACTTVE 1954 Inuvik Depth 1957 Inuvik Depth LAYER). of Thaw (Active of Thaw {Active SOIL TEMPERATURES. A T X - I 5 A T X - I 2 A i r s t r i p B o x N o . i ( G r e e n ) REF'ERENCES.

Thermo couple I-n stallation T h e r m o c o u p l e L r s t a l l a t l o n T h e r m ocouple trstallation,

I 6

I N U V I K , N . W . T .

ENGINEERING SITE INFORMATION b y J. A. Pihlainen LOCATION I n u v i k i s l o c a t e d a t l a t i t u d e 6 8 " z l r N , l o n g i t u d e L33"441 w, a p p r o x i m a t e l y _{I , 2 0 0 m i l e s n o r t h o f E d r n o n t o n a n d 1 2 0 r n i l e s n o r t h of} t h e A r c t i c C i r c l e . _{I t i s l o c a t e d o n a n u p l a n d a d j a c e n t t o t h e e a s t e r n} e d g e o f t h e M a c k e n z i e D e l t a a p p r o x i m a t e l y ?5 miles south of the B e a u f o r t s e a a n d 3 5 r n i l e s e a s t o f t h e delta town of Aklavik (Fig. 1).

HIST OR Y

T h e o l d e s t s e t t l e m e n t i n t h e r e g i o n i s F o r t M c p h e r s o n , e s -t a b l i s h e d b y -t h e H u d s o n r s B a y c o r n p a n y during -the rniddle of -the

n i n e t e e n t h c e n t u r y o n t h e P e e l River Z5 rniles upstream of its junction w i t h t h e M a c k e n z i e R i v e r . _{I t w a s t h e r n a i n p o s t f o r t h e A r c t i c coast} u n t i l l 9 l 2 w h e n f u r t r a d e c o m p e t i t i o n by the Northern Traders Cornpany f o r c e d t h e e s t a b l i s h m e n t o f a p o s t in the delta. This was the beginning o f A k l a v i k , w h e r e t h e A n g l i c a n Church established a mission in t9I9 a n d t h e R o m a n c a t h o l i c church one in 1926. The fur trade and

m i s s i o n s , _{w i t h s c h o o l s a n d h o s p i t a l s , s o o n e s t a b l i s h e d Aklavik as the} m a i n c e n t r e f o r t h e w e s t e r n A r c t i c .

I n c r e a s e d government activity in the Mackenzie Delta and t h e d i f f i c u l t i e s o f l a r g e s c a l e construction in its principal settlernent, A k l a v i k , p r o m p t e d a g o v e r n r n e n t decision in Decernber 1953 to investigate

t h e p o s s i b i l i t y _{o f relocating governrnent facilities at Aklavik in a better}

l o c a t i o n . _{A survey party, with members frorn variotrs government}

d e p a r t m e n t s h a v i n g i n t e r e s t s in the region, was assernbled to carry o u t t h e s e i n v e s t i g a t i o n s . _{D e t a i l e d f i e l d i n v e s t i g a t i o n s w e r e carried out} f r o m April to August 1954 at four potential sites. In August, on the b a s i s of this inforrnation and after a field review of the potential sltes, t h a t k n o w n a s E a s t T h r e e w a s selected by the governrnent as the new A k l a v i k t o w n s i t e ( l ) .

D u r i n g t h e s u m m e r o f 1 9 5 5 d e t a i l e d site investigations were c a r r i e d o u t a t t r E a s t T h r e e t f o r the Department of public works by

F o u n d a t i o n of canada Engineering corporation Lirnited. I n additlon,

z

-o n w a r e h -o u s e s and c-onstructi-on quarters. D u r i n g 1956 this type of

w o r k was continued, as well as the construction of the airstrip about Z

r n i l e s south of the townsite. _{D u r i n g 195? the i.nstallation of piling was}

i n i t i a t e d on a large scale for the foundations of perrnanent structures a n d c o n s t r u c t i o n o f h o s t e l s w a s b e g u n . E x t e n s i v e pile operations were c o n t i n u e d d u r i n g 1 9 5 8 , a n d c o n s t r u c t i o n o f t h e p o w e r h o u s e , utilidors a n d h o s p i t a l w a s b e g u n . B y p r o c l a m a t i o n i n Jury (I95g) the area k n o w n s i n c e 1 9 5 4 a s t r E a s t T h r e e r r w a s n a m e d I I I N U V I K , n E s k i m o

f o r t t t h e place of 'man. r' (see Fig. z for plan of principal B u i l d i n g s ,

1 9 5 9 . )

G E O L O G Y

T h e r n o d e r n M a c k e n z i e D e l t a , l 0 O r n i l e s l o n g a n d 50

m i l e s w i d e , i s a n e s t u a r i n e t y p e , h a v i n g p a r t i a l l y filled in the trough b e t w e e n t h e R i c h a r d s o n M o u n t a i n s o n the west and the Cariboo Hills o n t h e e a s t ( s e e F i g . l ) . A l t h o u g h the trough may be structurally c o n t r o l l e d , i t i s a r i v e r e r o d e d a n d a g r a c i e r - m o d i f i e d valley (z). T h e R i c h a r d s o n M o u n t a i n s , w h i c h confine the delta on the west, are c o m p o s e d o f s h a l e s , s a n d s t o n e s a n d conglomerates of cretaceous

a g e a n d r i s e t o h e i g h t s o f 2 a n d 3 t h o u s a n d feet above the delta. Between t h e edge of the mountains and the delta is a belt of coalescing alluvial f a n s i n w h i c h r n a t e r i a l r e s e r n b l i n g glacial drift has been observed.

T h e cariboo Hills form the rnost striking feature on the e a s t s i d e o f t h e d e l t a a n d a r e r e p o r t e d t o r e s e m b l e T e r t i a r y l i g n i t e -b e a r i n g f o r m a t i o n s d e s c r i -b e d f r o m other parts of northern Canada and A l a s k a ( 3 ) . N o r t h o f t h e c a r i b o o Hills one or more old Mackenzie R i v e r d e l t a s , a l o n g w i t h a v e n e e r o f post-glacial sediments, are

s u g g e s t e d ( z ) . I n a d d i t i o n , s o r r e o f t h e deposits may be fluviatile, l a c r u s t r i n e , o r m a r i n e . _{I n g e n e r a l , t h e f o r m l e s s a n d u n d u l a t i n g} c h a r a c t e r o f t h e g r o u n d s o u t h o f t h e c a r i b o o Hills suggests glacial d r i f t through which Palaeozoic dolornite, limestone and slaty shale are e > c p o s e d near Inuvik and farther south.

T h e origin of the soils at Leuvik has not been established a n d r e q u i r e s f u r t h e r f i e l d s t u d y . It has been suggested that the terrace o n w h i c h a l a r g e p o r t i o n o f t h e town is located ls a kame terrace, but a n o t h e r t h e o r y s u g g e s t s t h a t the granular deposits were 1aid down in a p r e g l a c i a l l a k e b y B o o t C r e e k .

3

-CLIMATE b y D . W . B o y d ' W ' e a t h e r

r e c o r d s at lrruvik cover only a few years, but o b s e r v a t i o n s , r n o s t l y t e m p e r a t u r e a n d p r e c i p i t a t i o n , have been

r e c o r d e d f o r o v e r 3 0 y e a r s a t A k l a v i k , 35 air rniles to the west. Ary p r e s e n t s t a t e m e n t o f t h e c l i r n a t e a t I n u v i k rnust be based on the

as-s u m p t i o n that it ias-s not greatly different from that at Aklavik. T e m p e r a t u r e

T h e mean annual ternperature at Aklavik and Lruvik is the s a m e , l 6 ' F ( T a b l e I ) . _{A l t h o u g h o b s e r v a t i o n s a t I n u v i k a r e limited,} s o r n e seasonal ternperature variatlons between Aklavik and Inuvik are s u g g e s t e d . _{D a i l y m a x i m u r n t e m p e r a t u r e s a t the two locations are} a b o u t the sarne in winter but are about 4 deg higher at Inuvik durlng t h e summer. _{D a i l y minimum temperatures o n the other hand average} a b o u t 2 deg lower at Inuvik throughout the year. Thus the average d a l l y range of temperature _{i s greater at Inuvik by about Z deg in wlnter} a n d by about 6 deg in surnrner.

T h e l o w e s t t e m p e r a t u r e r e c o r d e d a t A k l a v i k ( i n 32 years of o b s e r v a t i o n s ) w a s - 6 2 d e g . T h e average of the lowest ternperaiures in e a c h year is -51 deg. A comparison of monthly rninirna indlcates that a b o u t the sarne record low temperattrres could be e>cpected at Lruvik. T h e r e c o r d h i g h t e r n p e r a t u r e at Aklavik was 93 deg and the average o f t h e h i g h e s t t e r n p e r a t u r e s in each year is g3 deg. The comparison o f rnonthly maxima suggests that record high temperatures at huvik c a n be e>cpected to be z or 3 deg higher than at Aklavik.

P r ecipitati on

T a b l e II shows the norrnal rainfall, s n o w f a l l and total p r e c i p i t a t i o n _{a t A k l a v l k ( t o in. of snow equivalent to I in. of rain).} C o r r e s p o n d i n g _{v a l u e s for Lruvik are based on a comparison of rnonthly} t o t a l s for only two years. _{T h e results suggest that rainfall at Inuvik} i s slightly less than at Aklavik, but that Inuvik snowfall is greater. I t * D . W . B o y d is a mernber of the o f t h e D e p a r t r n e n t o f T r a n s p o r t C l i r n a t o l o g l s t _{w i t h the Division} s t a f f o f t h e M e t e o r o l o g i c a l _{B r a n c h} s e c o n d e d t o w o r k f u l l t i m e a s o f B u i l d i n g R e s e a r c h .

4

-s h o u l d b e empha-sized that the uncertainty in the value-s for Inuvik m a y b e almost as great as the difference between the two stations.

W i n d

T e n y e a r s of wind records are avallable from Aklavik, but t h e I n u v i k r e c o r d s a r e t o o s h o r t t o m a k e a n y c o m p a r i e o n s . A b r i e f s t a t e r n e n t of Aklavik winds however, is useful for som€ appreciation o f p r o b a b l e wind conditions at Inuvik.

A t A k l a v i k , _{t h e strongest winds occur in June wlth an} a v e r a g e o f o n l y I m l l e s p e r h o u r ; i n N o v e m b e r a n d D e c e m b e r the a v e r a g e i s l e s s t h a n 5 m i l e s p e r h o u r . F o r a l r n o s t h a l f t h e t l m e t h e w l n d is from the north or northwest, a n d for about one-third of the t i m e from the south or southeast.

O n l y the average wind speed and direction for each hour are r e c o r d e d a t A k l a v i k a n d t h e g r e a t e s t o f t h e s e h o u r l y w i n d e in the l0-y e a r r e c o r d i s 5 l m i l e s p e r h o u r . A n a n a l l0-y s i s o f extreme wlnds i n d i c a t e s that an hourly wind speed of.64 miles per hour should be e > c p e c t e d once in 30 years and that gust speeds should be e>cpected to r e a c h o r e x c e e d 8 8 r n i l e s p e r h o u r .

5

-T A B L E I

MEAN DAILY TEMPERATURES, AKLAVIK AND INUVIK, N. W. T.

M o n t h AKLAYIK INUVIK M e a n D a i l y T e m p e r a t u r e M e a n D a i l y Temperature Min M a x A v e r a g e Min M a x A v e r a g e J a n u a r y F e b r u a r y M a r c h A p r i l M " y June J u l y A u g u s t S e p t e r n b e r O c t o b e r N o v e r n b e r D e c e m b e r - 2 6 - 2 4 - I B

- z

z 3

40 47 4 Z 3 Z I 5 - 9 - 2 3

- t 0

- 9

0

r 9

4 0 5 8 6 6 5 8 4 4

z 5

3 - 1 0 - 1 8 - L 7 - 9 9

3 r

49

5 6 5 0 3 B

z 0

- 3 - 1 7 -28 - 2 6 -20 - 4 Z T 3 8 4 5 40 3 0 l 3 - l I -25

- I 0

- 9

I

z t

4 3 6 2 7 0

6 z

4 7

z 7

4 - 1 0 - t g - 1 8 - 1 0 9 3 Z 5 0 5 B 5 I 3 9

z 0

- 4 - I 8 Y e a r l y A v e r a g e I

2 4

L 6 6

z 6

l 6 T A B L E I I

PRECIPITATION AT AKLAVIK AND INUVIK, N. W. T.

Month

AKLAVIK INUVIK

P r e c i p l t a t i o n ( i n . P r eclpitatlon (in.

Rain Snow T o t a l R a i n Snow T o t a l

J a n u a r y F e b r u a r y M a r i h A p r i l M a y June July A u g u s t S e p t e r n b e r O c t o b e r N o v e m b e r D e c e m b e r 0 0 ,k 0 . 2 5 0 . 6 3 l . 3 9 L . 3 2 0 . 6 0 0 . 0 7 0 0 6 . 6 5 . 9 4 . 4 6 . 0 3 . 0

z . l

t . z

3 . 4 9 . 0 8 . 7 4 . 8 0 . 6 6 0 . . 5 9 0 . 4 4 0 . 6 0 0 . 5 5 0 . 8 4 l . 3 9 t . 4 4 0 . 9 4 0 . 9 7 0 . 8 7 0 . 4 8 0 0 0 . 1 6 0 . 4 2 0 . 9 2 0 . 8 7 0 . 4 0 0 . 0 5 0 0 7 . 6 5 . 8 5 . 0 6 . 9 3 . 4 2 . 4 1 . 4 3 . 9 1 0 . 3 1 0 . 0 5 - 5 0 . 7 6 0 . 6 8 0 . 5 0 0 . 6 9 0 . 5 0 0 . 6 6

0 . g z

t . 0 1 o . 7 9 I . 0 8 l . 0 0 0 . 5 5 Y e a r l y T o t a l 4 . 2 6 5 5 . 1 9 . 7 7 2 . 8 2 6 3 . Z

9 .

L 4

6

-R E L I E F

t e t h e I n u v i k r e g l o n , t h e u p l a n d a d j a c e n t t o t h e d e l t a r i s e s g e n t l y f o r I t o t l / 2 m i l e s a n d i s b o u n d e d o n t h e e a s t b y a h l g h l n t e r l o r

u p l a n d rislng over 150 feet. I n u v i k is located on the lower level

a d j a c e n t t o t h e d e l t a . _{I t s e a s t e r n b o u n d a r y i s d e l i n e a t e d b y t h e s t e e p} s l o p e t o t h e h i g h e r l a n d , w h i c h r o u g h l y p a r a l l e l s t h e e d g e o f t h e d e l t a . T h e I n u v i k r e g i o n e x t e n d s g e n e r a l l y i n a n o r t h - w e s t t o s o u t h - e a s t d i r e c t i o n i n w h i c h t h e l a n d f o r m s a r e s i m i l a r l y o r i e n t e d ; t h e g e n e r a l w e s t t o e a s t o r i e n t a t l o n o f t h e l a k e s e m p h a s l z e s t h i s c o n d l t i o n . T h e r e l l e f o f t h e r e g i o n i s o n e o f f l a t s a t v a r y i n g e l e v a t l o n s , g e n t l e u n d u l a t l o n s s e p a r a t e d b y s h a l l o w s w a l e s , r o u n d e d k n o l l s ,

h u m r n o c k y hills and ridges of varying helghts. D r a i n a g e is to the

w e s t o r n o r t h - w e s t b y s t r e a m s r l s i n g l n s t e e p g u l l l e s i n t h e h i g h t n t e r l o r u p l a n d . _{D r a i n a g e i s c o n t r o l l e d b y t h e r e l i e f , e s p e c l a l l y t n t h e s o u t h e r n} p a r t w h e r e t h e s t r e a m s f l o w i n p a r a l l e l c o u r s e s b e t w e e n t h e r i d g e s . A s a r u l e , t h e r i d g e s , k n o l l s a n d u n d u l a t i o n s are well drained, but

s o m e o f t h e l o w e r f l a t s a r e n o t .

V E G E T A T I O N

S p r u c e a n d b l r c h a r e t h e d o r n i n a n t t r e e t y p e s , w i t h s e c o n d a r y s t a n d s o f w i l l o w a n d a l d e r . _{T h e g r o u n d l s g e n e r a l l y h u m m o c k y , w i t h a} v e g e t a t i v e ground cover of ground birch, relndeer and sphagnurrr rnoss, g r a s s t u s s o c k s , L a b r a d o r T e a a n d b e r r y p l a n t s . B i r c h predominates o n t h e south-facing slopes of the landforrns and on the well drained a r e a s i s p r u c e o n t h e n o r t h - f a c i n g s l o p e s ; s t u n t e d s p r u c e , willow and a l d e r a r e f o u n d o n r n o r e p o o r l y d r a l n e d a r e a s . F e w t r e e s g r o w o n l o w f l a t a r e a s e x c e p t a l o n g s t r e a r n c o u r s e s w h e r e there are dense t h i c k e t s of wlllow and alder.

O n t h e t o w n s l t e f l a t a n d i t s a s s o c i a t e d k n o l l s a n d r i d g e s t o t h e west (between the flat and the East Channel) the trees are rnixed s p r u c e a n d b i r c h i n o p e n s t a n d s i n t e r s p e r s e d with scattered willow and

a l d e r . _{T h e spruce reach a maxirnurn diarneter of 9 in. at breast helght;}

t h e blrch, with average trunk diarneters of 6 in., reach a rnaximurn height o f a p p r o x i m a t e l y 3 5 f t . T h e r e a r e s e v e r a l c h a r r e d sturnps indicative

o f f o r r n e r burns. _{D u r l n g the sumrners of L954 and 1955 rnuch of the town}

a t e a w a s c l e a r e d o f b r u s h a n d s r n a l l e r t r e e s a s well as larger trees that c o n f l i c t e d w i t h r o a d o r b u l l d i n g s i t e s . B r u s h and tree clearing ln the h o s p i t a l a r e a w a s c a r r i e d o u t d u r i n g I 9 5 5 a n d 1957,

7

-W i l l o w thicket up to l? teet hlgh grows on the lower elope

f r o m Boot Lake to the townsite flat. F u r t h e r up, mixed spruce and

b i r c h m e r g e w i t h t h e t r e e v e g e t a t i o n o n t h e t o w n s i t e f l a t . D e n s e w i l l o w t h i c k e t a p p r o x i m a t e l y l 0 f e e t h i g h g r o w s i n a d e p r e s s i o n e x t e n d i n g south-east frorn the south half of Twin Lake and extends n o r t h a l o n g t h e e a s t s h o r e o f t h e l a k e w h e r e t h e r e i s a s m a l l s t a n d o f s p r u c e 6 0 f e e t h i g h .

T h e natural vegetatlon in the Inuvik area, before any

con-s t r u c t i o n , h a s b e e n summarlzed f r o r n aerial photographs taken in

S e p t e m b e r 1 9 5 5 i n t h e f o r r n o f a r n a p ( F i g . 3 ) . T h i s m a p s h o w s t h e d i s t r i b u t i o n o f t r e e s , s h r u b s a n d m o s s o n t h e b a s i s o f h e i g h t .

SOILS

A typlcal sequence of subsurface materials a t t h e Inuvik

t o w n s i t e l s s h o w n i n F i g . 4 . A l l v l n g c o v e r o f v e g e t a t i o n , m o s t l y m o s s , i s f o u n d e v e r y w h e r e , o v e r b r o w n t o b l a c k p e a t , w h l c h can be as d e e p a s 1 3 f e e t . _{P u r e i c e f o r m a t l o n s u p t o l f o o t t h l c k a r e o c c a s l o n a l l y}

f o u n d ln the peat. U n d e r l y i n g t h e p e a t there is usually a brown gravel

w i t h s a n d o r s i l t w h i c h v a r l e s i n t h l c k n e s s f r o m I t o l4 feet. This m a t e r i a l i s , i n t u r n , u n d e r l a i n b y a g r e y g r a v e l w l t h s a n d , silt or c l a y u p t o a t h l c k n e s s o f 9 f e e t . O n a g r a i n s i z e d i s t r i b u t i o n b a s t s t h e b r o w n a n d g r e y g r a v e l s a r e s i r d i l a r . G r a n u l a r d e p o s i t s a r e u n d e r l a l n b y v a r l o u s c o m b i n a t i o n s o f g r e y f i n e g r a i n e d s o l l s , mostly sllt sized. I c e l e n s c o n c e n t r a t i o n s a r e h i g h a n d o f t e n t h e r n a t e r l a l c a n b e described a s i c e w l t h s i l t i n c l u s l o n s a s w e l l a s l a y e r s o f c l e a r i c e .

T h e areal dlstribution _{o f soils in the bruvik townsite area}

i - s shown in Fig. 5. In general, brown or grey gravel wlth sand or silt i s u s u a l l y found throughout the site under peat ,up to a depth of- L3 feet. A c c o r d i n g l y , _{t h e d e p t h o f p e a t a b o v e t h e c o a r s e g r a i n e d s o i l s c o n s t i t u t e s}

a major subdivision of the soil distribution mapping. I s o l a t e d areas

o f f i n e g r a i n e d s o i l s f o r m t h e r e m a i n i n g s u b d i v i s i o n s "

T h e p r e d o m i n a n t s u b s u r f a c e r n a t e r i a l s o b s e r v e d a t hruvlk are a s f o l l o w s :

P e a t o r o r g a n l c r n a t e r i a l

B r o w n gravel with sand or silt G r e y gravel with sand, silt or clay F i n e g r a i n e d s o i l s

B

-T h e s e s u b s u r f a c e r n a t e r i a l s a r e m o r e v a r i a b l e t h a n t h e d i s c u s s i o n t o t h i s p o i n t w o u l d i n d i c a t e , a n d r n o r e d e t a i l e d n o t e s o n t h e i r o c c u r r e n c e a r e r e p o r t e d i n t h e f o l l o w i n g s e c t i o n s .

P e a t ; O r g a n i c M a t e r i a l

T h e organic material o r p e a t found at the Inuvik townsite

v a r i e s i n c o l o u r f r o m b r o w n t o b l a c k . I t s s t r u c t u r e i s p r e d o m i n a n t l y o n e o f n o n - w o o d y , f i n e f i b r e s i n t e r s p e r s e d w i t h v a r y i n g a m o u n t s o f s m a l l a n d l a r g e w o o d y a n d n o n - w o o d y p a r t i c l e s . T h e r e i s u s u a l t y a d i s t i n c t s e p a r a t i o n b e t w e e n t h e p e a t d e p o s i t a n d t h e m i n e r a l s o i l b u t i n s o m e c a s e s t h e o r g a n i c m a t e r i a l g r a d e s i n t o t h e m i n e r a l s o i l . O n e o f t h e m o s t s i g n i f i c a n t p r o p e r t i e s o f t h i s p e a t i s i t s r n o i s t u r e c o n t e n t . I t s p r e d o r n i n a n t l y f i b r o u s s t r u c t u r e h o l d s l a r g e

q u a n t i t i e s of water like a sponge. T h i s w a t e r retention ability is

e m p h a s i z e d b y t h e t e s t r e s u l t s o f r n o i s t u r e c o n t e n t d e t e r r n i n a t i o n s w h i c h , f o r c o n v e n i e n c e , a r e c a r r i e d o u t o n a w e i g h t b a s i s , ( m o i s t u r e c o n t e n t p e r c e n t a g e e q u a l s t h e w e i g h t o f p e a t s a m p l e w a t e r d i v i d e d b y t h e d r y w e i g h t o f t h e p e a t s a r n p l e m u l t i p l i e d b y 1 0 0 ) . s i n c e t h e s p e c i f i c g r a v i t y o f p e a t i s a p p r o x i r n a t e l y 1 . 5 ( n o r r n a l l y r n i n e r a l s o i l s h a v e a s p e c i f i c g r a v i t y o f a p p r o x i m a t e l y 2 . 7 ) r n o i s t u r e c o n t e n t s i n h u n d r e d s a n d o c c a s i o n a l l y t h o u s a n d s o f p e r c e n t a r e o b t a i n e d . T h e m o i s t u r e c o n t e n t o f 1 1 2 t h a w e d a n d 3 2 f r o z e n p e a t s a m p l e s f r o m the active layer at Inuvik were det'errnined frorn June to September

1 9 5 8 . T h e a v e r a g e f o r t h e t h a w e d s a m p l e s w a s f o u n d t o b e 3 4 7 p e r c e n t . w h e n t h e s e r e s u l t s w e r e a n a l y s e d s t a t i s t i c a l l y , t h e a v e r a g e v a l u e s o f m o i s t u r e ( o r i c e ) c o n t e n t i n t h e t h a w e d a n d f r o z e n p e a t w e r e f o u n d t o b e e q u a l f o r a 9 9 p e r c e n t s i g n i f i c a n c e l e v e l . M o i s t u r e content d i f f e r e n c e s between frozen and thawed peat rnay be different in certain f u r t h e r s u b d i v i s i o n s o f t h e s e r n a t e r i a l s , b u t o n a n o v e r - a l l basis the d i f f e r e n c e s c o u l d n o t b e d e t e c t e d b y t h e s e o b s e r v a t i o n s . O n a c o m b i n e d b a s i s , t h e a v e r a g e r n o i s t u r e c o n t e n t o f p e a t ( f r o z e n o r t h a w e d ) w a s f o u n d t o b e 3 6 9 p e r c e n t .

T h e l a r g e v a r i a n c e s f o r b o t h f r o z e n a n d t h a w e d p e a t s u g g e s t

t h a t for critical _{c a l c u l a t i o n s rnoisture content should not be estimated}

o n t h e b a s i s o f a v e r a g e f i e l d o b s e r v a t i o n s . I n s u c h c a s e s , t h e s e v a l u e s a r e best obtained by sarnples taken at the location for which the

c a l c u l a t i o n s a r e t o b e r n a d e .

T h e high rnoisture content of Inuvik frozen peat cements the p e a t f i b r e s a n d p a r t i c l e s i n t o a s o l i d , w o o d - l i k e m a s s . T h i s i c e i s n o t

9 -g e n e r a l l y v i s i b l e b y e y e , a l t h o u -g h s o r n e i c e s e -g r e -g a t i o n i n t h e f o r m o f t h i n , h a i r l i n e i c e l e n s e s d o e s o c c u r . R e l a t i v e l y t h i c k i c e m a s s e s a r e a l s o a s s o c i a t e d w i t h p e a t ; t h e s e m a y o c c u r n e a r t h e s u r f a c e , i n w h i c h c a s e t h e i c e m a y b e I i g h t b r o w n a n d a p p e a r c l o u d y b e c a u s e o f v e r t i c a l l y o r i e n t e d a i r b u b b l e s t r e a k s . M o r e o f t e n , i c e i s f o u n d i n t h e p e a t a t d e p t h s g r e a t e r t h a n t h e a c t i v e l a y e r ; i t r n a y b e a s t h i c k a s Z f e e t a n d c l e a r e x c e p t f o r a c l o u d i n e s s p r o d u c e d b y a i r b u b b l e s . A t t i m e s , f l a k e s , g l o b u l e s o r l e n s e s o f p e a t m a y b e f o u n d i n t h e i c e a n d t h e m a t e r l a l c o u l d b e d e s c r i b e d a s i c e w i t h p e a t I e n s e s . T h e s e l a r g e i c e r n a s s e g a r e g e n e r a l l y p a r a l l e l t o t h e g r o u n d s u r f a c e , a l t h o u g h s o m e i r r e g u l a r l y o r i e n t e d i c e t r d y k e s r r h a v e b e e n o b s e r v e d . I t h a s n o t b e e n p o s s i b l e t o d e t e r r n i n e t h e a r e a l e x t e n t o f a n y i n d i v i d u a l i c e m a s s , b u t o b s e r v a t i o n s s u g g e s t t h a t s o r n e o f t h e s e a r e a s w o u l d b e r n e a s u r e d i n h u n d r e d s o f s q u a r e f e e t .

B r o w n Gravel wlth Sand, Silt or Clay

T h e m o s t p r o m i n e n t s o i l a t I n u v i k i s a b r o w n g r a v e l w i t h s a n d , silt or clay. I t i s f o u n d t h r o u g h o u t rnost of the townsite in a l a y e r f r o r n 5 t o l 4 f e e t t h i c k u n d e r a v a r y i n g r n a n t l e o f o r g a n i c m a t e r i a l . A l l o f t h e r o a d s a n d t h e g r a v e l p a d s f o r r n o s t o f t h e b u i l d i n g s i n t h e t o w n h a v e u t i l i z e d t h i s m a t e r i a l f r o r n b o r r o w p i t s a t T w l n L a k e o r n e a r B o o t C r e e k . T h e r a n g e o f I 7 g r a i n s i z e d i s t r i b u t i o n s f o r t h e t o w n s i t e b r o w n g r a v e l i s s h o w n i n F i g . 6 . A g r a i n s i z e d i s t r i b u t i o n f o r a t 1 r y i c a l g o o d b o r r o w p i t m a t e r i a l i s a l s o i n c l u d e d . I t s h o u l d b e n o t e d t h a t t h e g r a v e l i s g e n e r a l l y w e l l g r a d e d i n a l l s i z e s f r o r n s i l t t o c o b b l e s ( s t o n e s g r e a t e r t h a n 3 i n c h e s r e r n o v e d f o r g r a i n s i z e t e s t s ) . T h e m a x i m u m b o u l d e r e n c o u n t e r e d i n t e s t p i t s w a s 2 z i n c h e s , a l t h o u g h s i z e s o v e r 8 i n c h e s were not corrrrrlon.

T h e rnaterial contains a considerable arnount of poor igneous r o c k f r a g m e n t s w h i c h a r e s u b j e c t t o r a p i d d e c o r n p o s i t i o n . A s m a l l s u r f a c e s a r n p l e w a s e x a m i n e d b y t h e B u i l d i n g M a t e r i a l s S e c t i o n o f t h e D i v i s i o n o f B u i l d i n g R e s e a r c h a s p o s s i b l e c o n c r e t e a g g r e g a t e . T h e f o l l o w i n g c o r n r n e n t s w e r e r n a d e : l . _{N o r r n a l s p r a y w a s h i n g i s a d e q u a t e f o r t h i s r n a t e r i a l .} Z . A c c o r d i n g t o A S T M a n d C S A g r a d i n g r e q u i r e r n e n t s f o r f i n e a g g r e g a t e i n c o n c r e t e , t h e s a n d p o r t i o n o f t h i s r n a t e r i a l i s u n s a t i s f a c t o r i l y g r a d e d a f t e r w a s h i n g , b e i n g s e r i o u s l y d e f i c i e n t i n t h e 3 0 - 5 0 a n d 5 0 - r 0 0 f r action s .

l 0 -3 . A c c o r d i n g t o A S T M a n d C S A s p e c i f i c a t i o n s , t h e l o s s e s i n t h e m a g n e s i u m s u l p h a t e s o u n d n e s s t e s t a r e m u c h t o o h t g h , i n d i c a t i n g a n u n s o u n d r n a t e r i a l . I t s h o u l d b e n o t e d t h a t t h i s t e s t b y i t s e l f i s n o t g e n e r a l l y c o n s i d e r e d r e l i a b l e . I t d o e s s u g g e s t t h e d a n g e r o f u s i n g t h i s m a t e r i a l w i t h o u t e > d r a u s t i v e t e s t i n g . 4 . M l c r o s c o p i c _{e x a m l n a t i o n b y a t r a i n e d p e t r o g r a p h e r c l a s s i f l e s t h i s} m a t e r i a l a s a n r r i n d u r a t e d s e d i m e n t r r w h i c h h a s b e e n t r a n s p o r t e d a c o n s i d e r a b l e d i s t a n c e b y w a t e r . S u c h m a t e r l a l c a n b e v e r y r r t o u g h l r b u t i t s d u r a b i l i t y w o u l d d e p e n d o n p o r e s l z e a n d t o t a l p o r o s i t y . F i e l d d e n s i t y d e t e r m i n a t i o n s o f . 3 6 f r o z e n b r o w n g r a v e l s a r n p l e s w e r e c a r r l e d o u t i n 1 9 5 5 ; t h e s e a v e r a g e d L 3 4 L b / e u f t . F o r 5 l s a m p l e s t h e a v e r a g e m o i s t u r e o r l c e c o n t e n t w a s f o u n d t o b e l 8 p e r c e n t . _{I t i s l n t e r e s t i n g t o n o t e t h a t a s t a t i s t l c a l a n a l y s i s o f t h e f i e l d} d e n s i t i e s o f b r o w n , g r e y - b r o w n o r g r e y g r a v e l s h o w e d t h a t t h e s e d e n s i t i e s w e r e n o t d i f f e r e n t f o r a 9 5 p e r c e n t s l g n i f l c a n c e l e v e l ( ? l s a r n p l e s ) . A c c o r d i n g l y , _{t h e f i e l d d e n s i t y o f I n u v i k g r a v e l c a n b e t a k e n a s} 1 3 6 I b / cu ft. T h e i c e l n t h e g r a v e l c e m e n t s t h e p a r t i c l e s i n t o a w e l l -b o n d e d a l r n o s t r o c k - l t k e r n a s s . T h e i c e i s u s u a l l y v i s i -b l e o n l a r g e r

p a r t i c l e s _{s u c h as pebbles as a thln filrn or a coating up to l/z indn}

t h i c k . _{O c c a s i o n a l l y , t h i n h a i r l i n e i c e l e n s e s h o r i z o n t a l l y o r i e n t e d} h a v e b e e n o b s e r v e d i n t h e g r a v e l f i n e s . o n l y o n e o c c u r r e n c e o f ice i n t h e g r a v e l ( 6 i n c h e s t h i c k a t a d e p t h o f . L 4 . 3 f e e t , T p z 9 ) h a s b e e n o b s e r v e d . A b r o w n s i l t y g r a v e l h a s b e e n o b s e r v e d a t t h e a i r s t r i p i g r a i n s i z e d i s t r i b u t i o n s o f t h r e e s a r n p l e s a r e s h o w n i n F t g . 6 . T h e materlal

h a s a significantly _{h i g h e r silt and clay content than the townsite gravels,}

a n d i n r r r a n y c a s e s r n a y b e d e s c r i b e d a s a s i l t c l a y w i t h s t o n e s and sand. W i t h stones larger than I/2 inch rernoved, the liquid limit ranges frorn 2 6 t o 3 6 p e r c e n t a n d a v e r a g e s z r p e r c e n t ; t h e p l a s t i c i t y i n d e x ranges f r o r n 9 t o I 6 p e r c e n t a n d a v e r a g e s l l p e r c e n t .

T h i s rnatrix of silt with sand and stones is well bonded with i c e n o t u s u a l l y d i s c e r n i b l e b y e y e . A t t h e t o p o f t h e d e p o s i t the well b o n d e d f r o z e n s o i l r n a t r i x l s i n t e r r u p t e d b y h o r i z o n t a l layers of ice up t o I i n c h t h i c k ; t h e s e d e c r e a s e i n s i z e a n d f r e q u e n c y w i t h d e p t h and a l r n o s t d i s a p p e a r a t t h e b o t t o m o f t h e d e p o s i t . I c e w i t h silt inclusions h a s a l s o b e e n o b s e r v e d i n t h e r n a t e r i a l ( s e e r r l c e t f ) . T h e i c e c o n t e n t t h r o u g h o u t t h e m a t e r i a l r a n g e d f r o m t 9 t o 92 per cent and averaged 3 4 p e r c e n t .

I l -G r e y -G r a v e l A g r e y g r a v e l w i t h s a n d o r s i l t h a s b e e n o b s e r v e d i n a r e a s m a p p e d a s b r o w n g r a v e l s o r d e e p p e a t d e p o s i t s ( F i g . 5 ) . A t t h e s e l o c a t i o n s , t h e g r e y g r a v e l l i e s u n d e r n e a t h e i t h e r b r o w n s a n d y g r a v e l o r g r e y f i n e g r a i n e d r n a t e r i a l s . T h e d e p o s i t s u s u a l l y o c c u r n e a r t h e e n d o f t e s t p i t p e n e t r a t i o n s , a n d v a r y i n t h i c k n e s s f r o r n z t o 5 f e e t a l t h o u g h o n e d e p o s i t i s k n o w n t o b e a t l e a s t 9 feet thick. Grey gravel i s f o u n d a t d e p t h s e x c e e d i n g 7 f . e e t a n d f o r t h a t r e a s o n h a s n o t b e e n u t i l i z e d a s e x t e n s i v e l y a s t h e b r o w n g r a v e l e v e n t h o u g h i t i s a s u p e r i o r m a t e r i a l p e t r o g r a p h i c a l l y . T h e g r a i n s i z e d i s t r i b u t i o n s o f t h r e e g r e y g r a v e l s a r n p l e s f r o r n t h e t o w n s i t e a r e a a r e s h o w n i n F i g . 7 . o n a g r a i n size basis, i t i s s i m i l a r t o t h e b r o w n g r a v e l . F i e l d d e n s i t y d e t e r r n i n a t l o n s o f 1 3 f r o z e n g r e y g r a v e l s a m p l e s c a r r i e d o u t i n r 9 5 5 e r n p h a s i z e t h e s i r n i l a r i t y . _{T h e s e a v e r a g e d 1 3 9 I b / c u f t .} I c e s e g r e g a t i o n i n t h e g r e y g r a v e l i s u s u a l l y s i r n i l a r t o t h a t i n b r o w n g r a v e l , b e i n g i n d i s c e r n i b l e b y e y e b u t cernenting the r n a t e r l a l i n t o a h a r d m a s s . I n s o r n e c a s e s , h o w e v e r , t h e g r e y g r a v e l b l e n d s i n t o a p r e d o r n i n a n t l y f i n e g r a i n e d r n a t e r i a l rnixed with stones. H e r e t h e i c e c o n c e n t r a t i o n s c a n b e s i g n i f i c a n t l y h i g h e r . F o r I 7 s a r n p l e s w i t h n o r m a l l y o n l y r a n d o r n t h i n h o r i z o n t a l ice lenses, the a v e r a g e i c e c o n t e n t w a s o b s e r v e d t o b e l ? p e r c e n t . A g r e y s i l t t o c l a y g r a v e l h a s a l s o b e e n o b s e r v e d a t the a i r s t r i p w h e r e i t i s o v e r l a i n b y a b r o w n s i l t y g r a v e l . T h e g r a i n s i z e d i s t r i b u t i o n s o f t h r e e s a r n p l e s a r e s h o w n i n F i g . 7 . As is found w i t h t h e b r o w n g r a v e l s , t h e g r e y a i r s t r i p g r a v e l s h a v e higher concen-t r a concen-t i o n s o f f i n e g r a i n e d p a r concen-t i c l e s concen-t h a n concen-t h e concen-t o w n s i concen-t e gravels. T h e l i q u i d l i m i t s o f f i n e s p a s s i n g a N o . 6 0 s i e v e r a n g e d f r o r n z0 to 52 per cent a n d a v e r a g e d 3 5 p e r c e n t . T h e p l a s t i c i t y i n d e x i n t h e s e t e s t s r a n g e d f r o m 7 t o Z Z p e r c e n t a n d a v e r a g e d l 5 p e r c e n t . T h e g r e y r n a t r i x o f s i l t y g r a v e l a t t h e a i r s t r i p w a s w e l l b o n d e d b y i c e a l t h o u g h i t w a s n o t u s u a l l y v i s i b l e by eye. Random fine h o r i z o n t a l i c e l e n s e s u p t o t / B i n c h t h i c k w e r e a l s o o b s e r v e d . I c e c o n t e n t s w e r e g e n e r a l l y l o w a n d f o r f i v e s a r n p l e s ranged from z to 2 3 p e r c e n t a n d a v e r a g e d l 6 p e r c e n t . S u b - r o u n d e d a n d a n g u l a r t o 3 i n c h e s i n d i a r n e t e r w e r e f o u n d T h e s e w o u l d h a v e p a s s e d u n n o t i c e d s u l p h u r o d o u r i n t h e t e s t p i t a s t h e p e b b l e s o f a r s e n o - p y r i t e f . r o r n | / 4 t h r o u g h o u t t h e d e p o s i t i n 1 9 5 7 . e x c e p t f o r t h e u n u s u a l g a r l i c o r r a n d o r n l y l o c a t e d p e b b l e s w e r e b r o k e n

b y t h e pneumatic hamrner s u b s e q u e n t l y o b s e r v e d i n B o o t C r e e k . F i n e G r a i n e d S o i l s I Z -. P e b b l e s o f a r s e r l o - p y r i t e h a v e b e e n t h e g r e y g r a v e l b o r r o w p i t m a t e r i a l n e a r

F i n e grained soils in the Inuvik townsite area are difficult t o d e s c r i b e b e c a u s e o f t h e i r w i d e v a r i a t i o n a n d o c c u r r e n c e . L e g e n e r a l , t h e y r n a y b e s e p a r a t e d i n t o t w o b r o a d s u b d l v i s i o n s o n t h e b a s i s o f

o c c u r r e n c e a n d g r a i n s i z e d i s t r i b u t i o n a s f o l l o w s :

( a ) p r e d o r n i n a n t l y s i l t s i z e d g r e y soils which usually occur below the b r o w n o r g r e y t o w n s i t e g r a v e l s , a n d

( b ) y e l l o w t o g r e y b r o w n silt clays with sand or stones which are f o u n d n e a r t h e g r o u n d s u r f a c e .

P r e d o m l n a n t l y _{s l l t s i z e d g r e y s o i l s h a v e b e e n o b s e r v e d u n d e r} b r o w n o r g r e y g r a v e l t h r o u g h o u t t h e t o w n s i t e area. The thickness of t h e s e d e p o s i t s a t t i r n e s e x c e e d s z 0 f e e t , a l t h o u g h fortunately, they o c c u r i n o n l y o n e o r t w o a r e a s i m r n e d i a t e l y u n d e r the rnoss and peat r n a n t ' l e . A t t l r n e s , t h e d e p o s i t s , c o n t a i n s t o n e s . a n d sands but the s i g n i f i c a n t f e a t u r e i s t h e l a r g e l c e c o n c e n t r a t i o n s .

T h e i c e i n t h e s e f i n e g r a i n e d s o i l s i s u s u a l l y i n t h e f o r r n of c l o s e l y s p a c e d h o r i z o n t a l l a y e r s o r l e n s e s varying ln thickness from t / 1 6 t o 3 f 4 i n c ? - . I n m a n y c a s e s t h e a r n o u n t o f i c e i n c r e a s e s to such a n e x t e n t t h a t t h e r n a t e r i a l r e s e r n b l e s l c e w i t h silt inclusions (see rrlcetl).

T h e g r a i n s l z e d i s t r i b u t i o n o f f o u r t y p i c a r s a r n p r e s of grey s i l t i s s h o w n i n F i g . 8 . F i e l d d e n s l t y determinations of l3 samples s h o w e d a n a v e r a g e d e n s i t y o f t I 6 \ b / c u ft (standard deviation 9 7b/cu ftl, a n d t h e a v e r a g e i c e c o n t e n t o f 2 7 s a r n p r e s was 4l per cent (standard d e v i a t i o n 2 4 p e r c e n t ) .

T h e s e c o n d b r o a d s u b d i v i s i o n o f f i n e g r a i n e d s o i l in the L n u v i k r e g l o n i s a g r e y t o y e l l o w i s h b r o w n sitt clay with some sand or s t o n e s . _{I t o c c u r s c l o s e t o t h e s u r f a c e c h i e f l y i n t h e upper flat, above} o r n o r t h o f t h e t o w n s i t e . _{T h e g r a i n s l z e d i s t r i b u t i o n o f f o u r s a m p l e s} i s s h o w n i n F i g . 9 . I c e s e g r e g a t i o n in the rnaterial is high and varles f r o r n h o r i z o n t a l o r i r r e g u l a r l y _{o r i e n t e d i c e l a y e r s u p t o 3 / 4 i n c h t h i c k} t o l a r g e i c e l a y e r s f r o r n L t o Z f e e t thick.

S i l t c l a y s with sorne sand and stone, sirnilar to the Inuvik upper f l a t f i n e g r a i n e d s o i l s , h a v e b e e n observed south-east of Long Lake.

1 3

-a s t h -a t o f t w o s -a m p l e s f r o m t h e d r u r n l i n s n o r t h - w e s t o f L o n g L a k e .

T h e l o w f l a t r e l i e f a n d t h e s t u n t e d t o s p a r s e v e g e t a t i o n n o r t h o f t h e t o w n s i t e , t h r o u g h w h i c h t h e r r N a v y R o a d r has been built, h a s s o m e i n t e r e s t i n g g r o u n d p h e n o r n e n a . F r o s t r n o u n d s 4 to 5 feet in d i a r n e t e r a n d u p t o Z f e e t h i g h a r e f r e q u e n t . I n m a n y l o c a t i o n e t h e y h a v e r u p t u r e d i n t o s o i l e x p o s u r e s k n o w n a s c l a y boils. A grain size d i s t r i b u t i o n o f t h e r n a t e r i a l i s s h o w n i n F i g . l l . T h e c l a y s i z e d f r a c t i o n i s t h e h i g h e s t o b s e r v e d a t I n u v i k . T h e liquid lirnit of the r n a t e r i a l i s 5 2 p e r c e n t a n d t h e p l a s t i c i t y i n d e x l 8 p e r c e n t .

I c e

I c e r n a s s e s , o r s o i l w i t h s o r n u c h i c e t h a t i t may be considered i c e , h a v e b e e n o b s e r v e d a t v a r y i n g d e p t h s throughout the townsite area ( F i g . L z \ . T h i s i c e i s chiefly associated with fine grained soils or p e a t , a l t h o u g h o n e o r t w o i c e r r r a s s e s h a v e been observed in brown or

g r e y g r a v e l .

c l e a r i c e t h i c k n e s s e s r a n g e f r o r n r t o 2 4 i n c h e s . T h e y a r e r n o s t often found in peat and to a lesser extent in the grey fine grai,ned s o i l s . _{I n t h e p e a t i n t h e t o w n s i t e a r e a d e p t h s t o ice range from 6 inches} t o 6 f e e t , w i t h a n a v e r a g e o f 3 f e e t .

I c e w l t h soil inclusions is rnost cornrnonry found in fine g r a i n e d s o i l s . T h e s e d e p o s i t s r a n g e i n t h i c k n e s s f r o r n 6 i n c h e s t o l Z f e e t , b u t o n t h e a v e r a g e t h e y a r e a p p r o x i r n a t e r y 5 feet thick. They are f o u n d o n t h e t o w n s i t e f l a t a t d e p t h s ranglng frorn lz to l5 feet; In the r r i n d u s t r i a l t r area, and particularly in the wharf knoll area, ice wlth s o i l i n c l u s i o n s i s f o u n d a t s h a l l o w e r depths frorn 6.5 to l6 feet.

T h e u p p e r t o w n s i t e f l a t , o n w h i c h n o rnajor construction is p l a n n e d a t p r e s e n t , h a s c l e a r i c e masses averaging I foot thlck ln a f i n e g r a i n e d s o i l w i t h s t o n e s at depths ranging onty fto- l5 to 30 inches.

E x t e n s i v e r r r a s s e s o f i c e a n d ice with soil inclusions have b e e n o b s e r v e d i n t h e b o r r o w p l t s south of Boot Creek. One 3-foot thick m a s s o f i c e , u n d e r l a i n b y b r o w n g r a v e l , was uncovered below 3 feet o f r n o s s a n d p e a t . A t a n o t h e r l o c a t i o n nearby (known as rllce Hilltt), a t e s t p i t 1 2 f e e t d e e p r e v e a l e d z f e e t of brown gravel underlain by i c e a n d i c e w i t h s i l t i n c l u s i o n s to the depth at which the test pit was a b a n d o n e d .

1 4

-N o i c e m a s s e s h a v e b e e n o b s e r v e d l n t h e d r u m l i n - l i k e

h t u s ln the vlcinity of Long Lake. _{o n e test pit tn the low flats on the} n o r t h - e a s t e n d o f t h e l a k e , h o w e v e r , d l d r e v e a l t w o i c e m a s s e s 6 i n c h e s thick at depths of t8 and 30 lnches in a grey sandy gravel mlxed with gilt and clay.

I n t h e a i r s t r i p a r e a o n e t e s t p l t i n a n 8 - f o o t d e e p p e a t d e p o s l t revealed only one Large lce lens 2 inches thick at a depth of 2 l l n c h e s . _{I c e w i t h s i l t i n c l u s i o n s w a s r h o w e v e r , o b s e r v e d i n a l l f o u r} t e s t p i t s ( F i g . l 3 ) . T h i s f o r m o f l c e s e g r e g a t l o n s t a r t e d i n o r j u s t u n d e r the organic material and contlnued for 4 feet ln two test plts a n d ln I foot In one test plt. L r the fourth test pit, with relatlvely l l t t l e o r g a n i c o r p e a t c o v e r , t h e l c e w i t h s i l t i n c l u s i o n s a p p e a r e d 3 f e e t below the ground surface and continued for only I foot.

p E P T H OF THAW (ACTTVE LAYER)

T h e s e a s o n a l d e p t h o f t h a w i n p e r m a f r o s t a r e a s , i n w h a t r s c o m m o n l y k n o w n a s t h e r r a c t i v e l a y e r , I t h a s l o n g b e e n r e c o g n l z e d . A l t h o u g h its variability _{h a s a l s o been known, there is stl1l a tendency} f o r e n g l n e e r s t o r e g a r d i t a s a d e f i n i t e t h i c k n e s s f o r a l o c a l i t y .

I n f a c t it is sorne reflectlon of the energy available in a

l o c a l i t y to thaw frozen ground. P r e d i c t i o n o f t h e energy change between t h e t e r r a l n s u r f a c e a n d t h e a t m o s p h e r e c a n n o t b e r e a d i l y r e d u c e d to a

s i m p l e b a s i s , h o w e v e r , e v e n t h o u g h t h e r e s u l t i s a s l m p l e concept s u c h as the depth of thaw. _{T h e dorninant weather elements that affect} t h i s e n e r g y c h a n g e a r e s u n s h i n e , a i r t e m p e r a t u r e a n d w i n d . In addltlon, r e l i e f , o r i e n t a t i o n a n d t h e p r e s e n c e o f n e a r b y o b j e c t s , as well as the a b s o r p t i v l t y a n d e m i s s l v i t y c h a r a c t e r i s t i c s o f t h e s u r f a c e l n v o l v e d , e n t e r into the problem. _{A d d i t i o n a l cornplication is provided by the} e f f e c t s of precipitation, c o n d e n s a t i o n , e v a p o r a t i o n , p l a n t transpiration a n d t h e t h e r m a l c h a r a c t e r i s t i c s o f t h e s o i l . E v e n i f a I I o f t h e s e i n d i v i d u a l factors could be rneasured, there remains the problem of r e c o m b i n i n g t h e s e v a r i a b l e s i n t h e calculations.

E n g i n e e r l n g planning and design in the north require some k n o w l e d g e of the seasonal depth of thaw for a locality. I n particular, t h e range of depths of thaw under orlginal terrain conditions and some i n d l c a t i o n of the increase in the depth of thaw frorn the disturbance

c a u s e d b y c o n s t r u c t i o n a r e r e q u i r e d . _{T h e f o l l o w i n g o b s e r v a t i o n s a t t e m p t} a f i r s t approximation _{o f these questions for Lruvik. T h e 1954 Inuvtk} d e p t h o f t h a w o b s e r v a t l o n s r e f l e c t original terrain conditlons. Those for

1 5

-1 9 5 7 s e r v e a s a n i n d i c a t i o n o f t h e i m m e d i a t e c h a n g e s i n d e p t h o f thaw t h a t can be anticipated during initial disturbance of an area.

1 9 5 4 Inuvik Depth of Thaw (Active Layer)

D u r i n g J u l y a n d A u g u s t , 1 9 5 4 , b e f o r e o c c u p a t i o n a n d b e f o r e a n y c o n s t r u c t i o n i n t h e I n u v i k r e g i o n , 2 5 t e s t p i t s w e r e excavated f o r p r e l i m i n a r y s o i l s a n d p e r m a f r o s t i n v e s t i g a t l o n . T h e d e p t h o f t h a w w a s r e c o r d e d w h e n e a c h t e s t p i t w a s s t a r t e d a n d i s s h o w n in Fig. L4. t r s t e a d of plotting the date on which the depth of thaw was observed, t h e r r t h a w i n g i n d e x r r f o r t h e d a t e h a s b e e n u s e d ( t h e t h a w i n g index is a

c u m u l a t i v e t o t a l o f t h e n u m b e r o f d e g r e e s a b o v e 3 2 " F o f the average a i r t e m p e r a t u r e f o r e a c h d a y u p t o t h e d a t e o f o b s e r v a t l o n ) . T h e t h a w i n g i n d e x i s u s e d a s a f l r s t a p p r o x i m a t i o n o f t h e energy expended i n t h a w i n g f r o z e n s o i l . _{T h e r n a n y l i m i t a t i o n s o f a c c e p t i n g a m e a s u r e o f} a i r t e m p e r a t u r e t o r e f l e c t e n e r g y c h a n g e s a r e appreclated but are

c o n s i d e r ed justifiable _{i n this pr elirninary qualitative engineering} a p p r a i s a l . _{I t s u s e a l l o w s a m o r e c o n v e n i e n t c o m p a r i s o n o f s i m l l a r} r e c o r d s f o r d i f f e r e n t y e a r s a n d l o c a t i o n s . _{A l s o i n c l u d e d i n F i g . 1 4} i s a brief notatlon of the thawed rnaterial.

D e p t h of thaw observations rnade late durlng the 1954 t h a w l n g s e a s o n a r e o f i n t e r e s t s i n c e t h e y offer some indlcation of the a c t i v e layer at Inuvik before occupation. A s would be expected, the t h l c k n e s s of the moss and peat mantle has a significant effect on the d e p t h of thaw. O b s e r v a t l o n s _{o n tlne ZZnd of August (thawing index 1938} d e g r e e d a y s ) r e c o r d a r a n g e o f t h a w f r o m r z i n c h e s i n p e a t t o 5 l l n c h e s i n g r a v e l w l t h a 4 - i n c h c o v e r of moss and peat.

D u r i n g t h e s u r n r n e r o f 1 9 5 7 , n i n e areas in the immediate

v l c i n i t y of the Inuvik townsite were chosen for depth of thaw observations t o g i v e r e p r e s e n t a t i v e s e a s o n a l thaw information on undisturbed terrain w i t h v a r y i n g c o v e r o f t r e e s , shrubs and rnoss; on disturbed areas where t r e e s a n d s h r u b s h a d b e e n r e r r l o v e d ; and on stripped areas rrrihere all t h e l i v i n g o r g a n i c c o v e r h a d b e e n rernoved. Thaw measurements were r n a d e b y p r o b i n g a n d w i t h t e s t p i t s . Three to six thaw depths were

r n a d e a t e a c h l o c a t i o n a n d t h e a v e r a g e value recorded. T h e o b s e r v a t i o n s w e r e c a r r i e d o u t r n o n t h l y or twice rnonthly as the season progressed.

F i g u r e 1 5 r e c o r d s t h e e x t r e r n e l i r n i t s of the depth of thaw

1 6

-t e r r a i n a-t huvlk durlng 1957. As expec-ted, significan-t dlfferences i n the depths of thaw for stripped and undistrubed areas are very

e v i d e n t , and sorne indication of the variabtltty w i t h i n these two terraln

g r o u p s l s a l s o o b t a l n e d "

I n n e i t h e r u n d i s t u r b e d n o r d i s t u r b e d a r e a s ( w h e r e t h e m o s s h a s b e e n l e f t i n t a c t ) c o u l d t h e o b s e r v a t i o n s d e t e c t d i f f e r e n c e s i n d e p t h o f

t h a w that would be significant frorn a construction point of view. T h u s the

d o m l n a n t f a c t o r i s t h e m o s s c o v e r ; t h e p r e s e n c e o r a b s e n c e o f t r e e s a n d shrubs does not appear to affect depth of thaw appreciabLy.

I n a r e a s stripped of vegetation the domlnant factor appear6 t o b e t h e u n d e r l y i n g s o i l t 1 4 p e . F i n e g r a i n e d s o l l s s h o w l e s s t h a w

t h a n c o a r s e grained soils. A t Inuvlk the flne gralned solls usually

c o n t a l n more ice than the coarse gralned soils so that a dlstlnction b a s e d s o l e l y o n g r a i n s i z e l s n o t g e n e r a l l y i n o r d e r "

T h u s the maxlrnurn observed depths of thaw experienced

a t I n u v i k j u s t three years after occupation are approximately Z f . e e t

l n e l t h e r u n d l s t r u b e d o r d l s t u r b e d a r e a s w h e r e t h e r n o s s cover is left

i n t a c t ; approximately _{5 f e e t i n areas stripped of rnoss and underlaln}

b y f i n e g r a i n e d s o l l s ; a n d 8 f e e t i n a r e a s s t r l p p e d o f m o s s and underlaln

b y coarse grained soils. _{T h e volurne changes or the terraln elevation}

c h a n g e s assoclated with these thaws have not been recorded but do forrn

a part of future studies. T h e lmplications o f such terrain s e t t l e m e n t s

s h o u l d be consldered in any englneering planning and desrgn.

SOIL TEMPERATURES

S o l l ternperature o b s e r v a t i o n s a t t h e townsite reflecting

o r i g l n a l condltions have not been obtained. S o m e lndication of these,

t e r n p e r a t u r e s l s p o s s i b l e , h o w e v e r , f r o m records of two thermocouple

l n s t a l l a t i o n s _{m a d e t h e r e in August 1955 as well as frorn one at the}

a l r s t r i p i n M a r c h 1 9 5 7 . T h e r e h a v e b e e n many difficultles with field

i n s t a l l a t i o n s _{a n d the probabllity o f o b s e r v e r error in some instances}

i s considerable. _{I t is evldent that the results can be questioned for both}

o f t h e s e r e a s o n s . _{T h e o b s e r v a t i o n s , h o w e v e r , a r e i n c l u d e d w i t h t h e} t h o u g h t that sorne qualitative appraisal of orlginal soil ternperatures is p o s s i b l e .

T h e r m o c o u p l e I n s t a l l a t i o n A T X - I5

- \ 7 -a t -a d e p t h o f . 4 7 f e e t , -a t e m p e r -a t u r e o f . 2 9 . 3 " t r ' w -a s r e c o r d e d . B y t h e Z Z n d o f S e p t e r n b e r , w h e n o b s e r v a t i o n s f o r t h e y e a r e n d e d , t h e t e r n p e r a t u r e h a d d e c r e a s e d t o 2 7 . 4 o F . O b s e r v a t i o n s f o r t h e y e a r 1 9 5 6 w e r e r e s u r n e d l n J u n e a n d c o n t i n u e d interrnittentl.y o n a p p r o x i r n a t e l y a w e e k l y b a s i s u n t i l S e p t e r n b e r 2 2 . F o r t h i s i n t e r v a l t h e o b s e r v e d t e r n p e r a t u r e s r a n g e d f r o m 2 4 . 5 t o 2 6 . 5 " F . T h e a v e r a g e s o l l t e r n p e r a t u r e f o r e l e v e n o b s e r v a t i o n s i n t h i s i n t e r v a l w a s 2 5 . 7 " F ( s t a n d a r d d e v l a t i o n 0 . 5 ' F ) . M u c h o f t h e d e v i a t i o n c a n b e a t t r i b u t e d t o o b s e r v e r e r r o r .

O b s e r v a t i o n s for 1957 began on 25 June and ended on 6

O c t o b e r . T h e a v e r a g e o f e i g h t t w i c e - r n o n t h l y o b s e r v a t i o n s w a s 2 6 . L " F ( w i t h n o s i g n l f l c a n t s t a n d a r d d e w i a t i o n ) . O b s e r v a t i o n s f o r 1 9 5 8 b e g a n o n I 6 J u n e a n d e n d e d o n I 4 S e p t e r n b e r , w i t h o b s e r v a t i o n s a g a i n o n a t w i c e - m o n t h l y b a s i s . T h e a v e r a g e s o i l t e r n p e r a t u r e f o r s e v e n s u c h o b s e r v a t i o n s w a s 2 5 . 9 " F ( w i t h a s t a n d a r d d e v i a t i o n o f 0 . 3 " F ) . I n s u m m a r y , a t e r n p e r a t u r e a f . 2 5 . p " F a t a d e p t h o f - 4 7 f e e t h a s b e e n o b s e r v e d a t I n u v l k . T h i s t e r n p e r a t u r e h a s n o t c h a n g e d a p p r e c i a b l y i n t h e y e a r s 1 9 5 6 t o 1 9 5 8 . T h e r m o c o u p l e I n s t a l l a t i o n ATX -1 2 T h e i n s t a l l a t i o n i s l o c a t e d i n B l o c k 2 8 , s o u t h o f D l s t r i b u t o r S t r e e t a n d s o u t h - e a s t o f t h e f i r e h a l l . O r i g i n a l l y , n o c o n s t r u c t i o n w a s c o n t e m p l a t e d in the area but the construction of the nearby utilidor h a s n o w d i s t u r b e d i t . T h e i n s t a l l a t i o n h a s t h e r r n o c o u p l e s l , Z , 3 , 4 , 5 , 7 . 5 , 1 0 , L 2 . 5 , 1 5 , I 7 . 5 a n d 2 0 f . e e t b e l o w t h e g r o u n d s u r f a c e a t t a c h e d t o a p i l e . T h e l o c a t i o n w a s s t e a r n e d a n d t h e p i l e d r i v e n t o d e p t h o n A u g u s t 1 3 , 1 9 5 5 . S o i l t e r n p e r a t u r e o b s e r v a t i o n s f o r t l n e Z - , 5 - , l 0 - , 1 5 - a n d Z 0 - f . o o t d e p t h s f . o r 1 9 5 6 a r e s h o w n i n F i g . L 6 . O b s e r v a t i o n s c o n t i n u e d a t t h e i n s t a l l a t i o n a n d t h e r e c o r d s f o r 1 9 5 7 a r e s h o w n i n F i g . 1 7 . T h e o b s e r v a t i o n s f o r 1 9 5 8 a r e n o t i n c l u d e d i n t h i s p o r t i o n o f t h e r e p o r t , s i n c e a considerable arnount of construction activity has taken place in t h e a r e a .

U n f o r t u n a t e l y , i t w a s not possible in 1956 and 1957 to make

c o n t i n u o u s observations throughout the years and comrnents on the results a r e a c c o r d i n g l y d i f f i c u l t . I n g e n e r a l , s e a s o n a l t e r n p e r a t u r e c h a n g e s a r e d e t e c t e d a s d e e p a s 2 0 f e e t . T h e o b s e r v a t i o n s f o r 1 9 5 6 a r e r a t h e r

e r r a t i c l _{t h i s r n a y be due to the fact that the installation had still not}

r e t u r n e d t o t h e o r i g i n a l g r o u n d t e r n p e r a t u r e s a f t e r t h e s t e a m i n g , a l t h o u g h r r l o r e p r o b a b l y i t i s t h e r e s u l t o f o b s e r v e r e r r o r . T h e 1 9 5 ?

l B -o b s e r v a t i -o n s a p p e a r t -o b e m -o r e c -o n s i s t e n t a n d a r e i n g e n e r a l a g r e e m e n t w i t h t h e 1 9 5 6 o b s e r v a t i o n s . T h e r m o c o u p l e L r s t a l l a t i o n , A i r s t r i p B o x N o . I ( G r e e n ) T h e a l r s t r l p t h e r m o c o u p l e l n s t a l l a t i o n B o x N o . I ( G r e e n ) i s l o c a t e d a p p r o x i m a t e l y 1 , 0 0 0 f e e t n o r t h o f t h e a i r s t r i p a n d a p p r o x i m a t e l y _{2 0 0 f e e t e a s t o f t h e a l r s t r i p r o a d i n r e l a t i v e l y u n d i s} -t u r b e d -t e r r a l n -t h a -t i s c o n s i d e r e d r e p r e s e n -t a -t i v e o f -t h e a r e a . T h e i n s t a l l a t i o n c o n s l s t s o f t h r e e t h e r m o c o u p l e s e a c h a t 0 , 0 . 5 - , l -, Z - , 3 - , 4 - , 5 - , l 0 - a n d l 5 - f o o t d e p t h s . T h e i n s t a l l a t i o n w a s m a d e i n a t e s t p i t d u r l n g r z t o l 5 M a r c h , 1 9 5 2 . s o i l t e m p e r a t u r e o b s e r -v a t l o n s a t d e p t h s o f 2 , 5 , l 0 a n d l 5 f e e t a r e s h o w n t n F i g . lB. I n g e n e r a l , t w o c h a r a c t e r i s t i c s o f s o l l t e m p e r a t u r e s a r e w e l l i l l u s t r a t e d . _{T h e r a n g e ( o r a m p l i t u d e ) o f g r o u n d t e m p e r a t u r e s a s} t h e y a r e a f f e c t e d b y s e a s o n a l a i r t e r n p e r a t u r e s d e c r e a s e s w i t h depth. F o r example, at a depth af" 2 feet the range of soll ternperatures is

f r o m approxirnately _{l 3 t o 3 9 " F , while at a depth of I5 feet the range}

i e only from 22 to 29"F. _{T h e r e is also a time lag during which rnlnlrnum}

a n d r n a x i r n u m s o i l t e m p e r a t u r e s a r e r e c o r d e d a n d w h i c h increaseg

w i t h d e p t h . _{A t 2 feet, the mlnirnum soil temperature o c c u r s in March}

a n d the rnaxirnum in August. A t l5 feet the minirnurn soil temperature

o c c u r s in June and the maxlrnum ln January, or approximately s l x

m o n t h s after the air ternperature extrefites.

R E F E R E N C E S

( l ) M e r r i l l , _{C . L . , P i h l a i n e n , J . A . , a n d R . F . L e g g e t . T h e N e w}

A k l a v i k _{- search for the slte. The Engineerlng Journar,}

v o l . 4 3 , N o . l , J a n . 1 9 6 0 , p . 5 2 - 5 7 . ( r e p r i n t e d a s N R c 5 5 2 3 1 ( z \ M a c k a y , J . R o s s . M a c k e n z i e D e l t a - A p r o g r e s s R e p o r t . T h e

c a n a d i a n G e o g r a p h e r , N o . 7 , T h e c a n a d i a n A s s o c i a t i o n of G e o g r a p h e r s , O t t a w a , 1 9 5 6 .

( 3 ) Kellaway, G . A . _{N o t e s o n the Georogy of the Mackenzie Delta}

-A b s t r a c t . _{T h e c a n a d i a n G e o g r a p h e r , N o . 7 , T h e c a n a d l a n} A s s o c i a t i o n o f G e o g r a p h e r s , O t t a w a , 1 9 5 6 .

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