DRAFT

MANUAL ON SOIL CONSERVATION

AND PIPELINE CONSTRUCTION

Based on a Report

Prepared by

TERA ENVIRONMENTAL CONSULTANTS (ALTA.) LTD.

and

PEDOLOGY CONSULTANTS

ENVIRONMENT

F Land Reclamation Division u Regulated Operations Division

.F October, 1995

DRAFT

MANUAL ON SOIL CONSERVATION AND PIPELINE CONSTRUCTION

Based on a Report

Prepared by

TERA ENVIRONMENTAL CONSUL TANTS (AL TA. ) L TD.

and

PEDOL OGY CONSULTANTS

ENVIRONMENT

Land Reclamation Division

Regulated Operations Branch

Ortober, 1985

A l b e r t a Environment. Regu la ted Operat ions Branch. Land Reclamat ion D i v i s i o n . Manual on S o i l Conservat ion and P i p e l i n e Cons t ruc t i on . Edmonton. 1985. 82p.

1 .0 INTRODUCTION

MANUAL ON SOIL CONSERVATION AND

PIPELINE CONSTRUCTION

Page

2.0 IMPACT OF PIPEL INE CONSTRUCTION ON AGRICULTURAL LAND

2.1 S o i l M i x i n g

2.2 S o i l Compaction

2.3 Topso i l Loss

3.0 AGRICULTURAL SOILS

3.1 Parent M a t e r i a l s

3.2 S o i l Zones o f A l b e r t a

3.3 S o i l Orders o f A lbe r ta

4.0 PIPELINE CONSTRUCTION

4.1 P i p e S ize

4.2 R igh t o f Way Width

4.3 Cons t ruc t i on Operat ions

4.31 R igh t o f Way Prepara t ion

4.32 I n s t a l l a t i o n

4.33 Cleanup and Res to ra t i on

4.34 R igh t o f Way T r a f f i c

4.4 Equipment

4.41 Convent ional Equipment

4.42 Spec ia l i zed Equipment

Page

5.0 PLANNING FOR SOIL CONSERVATION

5.1 Calcula t ion of Right of Way Width

5.2 So i l Conservation Procedures

5.21 No Topsoil S t r ipp ing

5.22 Trench Width Topsoil S t r ipp ing

5.23 Blade Width Topsoil S t r ipp ing

5.24 Trench and Spoi l Area Topsoil S t r ipp ing

5.25 Trench, Spoi l and Work Area Topsoil S t r i p p i n g

5.3 Procedures fo r Spec ia l F ie ld S i t u a t i o n s

5.31 Road, Rail and Canal Crossings

5.32 Foreign Line Crossings and Test S i t e s

5.33 Grading

5.4 Extraordinary Conditions

5.41 Wet S o i l Condit ions

5.42 Frozen S o i l Conditions

5.43 I r r i g a t e d Lands

5.44 Three Phase S o i l Handling

TABLES AND FIGURES

TABLES

3.1 Parent Ma te r i a l C h a r a c t e r i s t i c s

Page

8

Cl imat ic Fea tures of t h e S o i l Zones and Their Imp l i ca t ions t o P ipe l ine Construct ion 15

Fea tures of the S o i l Orders of Alberta 16

Associated Impacts t o t h e S o i l Orders of Alberta 17

Ground P res su res For Typical P i p e l i n e Equipment 73

Subsoi l C r i t e r i a 80

FIGURES

3.1 S o i l Zones of Alberta

4.1 P ipe l ine Right of Way

5.1 Typical S t r i p p i n g and Storage Requirements

5.2 No Topsoil S t r i p p i n g

5.3 Trench Width Topsoil S t r i p p i n g

5.4 Blade Width Topsoi l S t r ipp ing

5.5 Trench and Spo i l Area Topsoil S t r i p p i n g

5.6 Trench, Spoi l and Work Area Topsoil S t r i p p i n g

5.7a S o i l Handling a t Road, Rai l and Canal Crossings (Cu l t i va t ed Lands)

5.7b S o i l Handling a t Road, Rai l and Canal Crossings (Pas ture Lands)

5.8 S o i l Handling a t Foreign Line Crossings and Test S i t e s

5.9 Three Phase S o i l Handling 78

PREFACE

This manual d i s c u s s e s t h e impact of p i p e l i n e c o n s t r u c t i o n on a g r i c u l t u r a l

land, i nc lud ing l and with p o t e n t i a l f o r a g r i c u l t u r e . The document

add re s se s reasons why c e r t a i n s o i l s a r e more s e n s i t i v e t o impact than

o the r s and h i g h l i g h t s s p e c i f i c a c t i v i t i e s of p i p e l i n e c o n s t r u c t i o n which

c r e a t e t hose impacts. Based on t h i s d i s cus s ion , f i v e common soil handl ing

procedures f o r conse rva t i on of a g r i c u l t u r a l l ands du r ing p i p e l i n e

c o n s t r u c t i o n a r e d i scussed i n terms of their r e l a t i v e e f f e c t i v e n e s s f o r

d i f f e r e n t s o i l types .

This manual has been designed t o a s s i s t p i p e l i n e p l anne r s i n determining

opt imal soil handl ing procedures based on mi 1 type , seasona l cond i t i ons

and equipment a v a i l a b i l i t y . The manual is n e i t h e r a r e g u l a t i o n , nor a

s t anda rd ; i t s in tended use is a s a r e f e r ence document f o r t hose involved

i n p i p e l i n e planning.

1 -0 INTRODUCTION

A g r i c u l t u r a l s o i l s a r e one of A l b e r t a ' s most v a l u a b l e r e s o u r c e s ; mainten-

ance of s o i l c a p a b i l i t y is e s s e n t i a l t o suppor t t h e a g r i c u l t u r e i n d u s t r y

i n t h e p rov ince . The pet roleum i n d u s t r y is a l s o a major c o n t r i b u t o r t o

t h e p r o v i n c e ls economic h e a l t h through employment, t a x a t i o n , and t h e pur-

c h a s i n g of l o c a l goods and s e r v i c e s . C o n f l i c t s do, however, occur between

t h e s e two i n d u s t r i e s . One of t h e major concerns h a s been t h e impact o f

p i p e l i n e c o n s t r u c t i o n on t h e p r o d u c t i v e c a p a b i l i t y of a g r i c u l t u r a l soils.

The long-term g o a l of m a i n t a i n i n g so i l q u a l i t y can and shou ld c o i n c i d e

wi th t h e more immediate g o a l s of t h e p i p e l i n e owner and c o n t r a c t o r . Th i s

manual has been des igned t o f a c i l i t a t e t h e p i p e l i n e owner i n t h e p l a n n i n g

and c o n s t r u c t i o n of p i p e l i n e s a c r o s s a g r i c u l t u r a l l a n d s wi thou t compromis-

i n g t h e s o i l q u a l i t y r equ i rements of t h e province .

The o b j e c t i v e of t h e s t u d y is t o review c u r r e n t methods of s o i l h a n d l i n g

d u r i n g p i p e l i n e c o n s t r u c t i o n and t o a s s e s s p rocedures most s u i t e d t o

s p e c i f i c s o i l and a g r i c u l t u r a l l and uses . The document is i n t e n d e d f o r

u s e by p i p e l i n e p l a n n e r s i n d e s i g n i n g soil hand l ing p rocedures f o r pipe-

l i n e s which c r o s s a g r i c u l t u r a l l ands . l lAgr icu l t u r a l l ands" means a l l

l a n d s i n t h e p rov ince used, o r capab le of being used, f o r annual f i e l d

c rops , f o r a g e c r o p s o r g raz ing .

The purpose o f t h i s r e p o r t is t o d i s c u s s t h e i n t e r r e l a t i o n s h i p s between

s o i l p r o p e r t i e s , p i p e l i n e c o n s t r u c t i o n p r a c t i c e s and soil impacts ; t o

document c u r r e n t p i p e l i n e s o i l hand l ing p rocedures , and t o de te rmine which

p r o c e d u r e s a r e b e s t s u i t e d t o s p e c i f i c s o i l and l a n d use c o n d i t i o n s .

Three major impac t s t o a g r i c u l t u r a l s o i l from p i p e l i n e c o n s t r u c t i o n a r e :

1. S o i l mixing.

2. Compaction o f t o p s o i l o r s u b s o i l .

3 . Loss of t o p s o i l .

These impacts may vary i n type and magnitude depending on s o i l type ,

weather, pipe s i z e , equipment a v a i l a b i l i t y , and s o on.

The cons t ruc t ion ope ra t i ons which c o n t r i b u t e most t o s o i l impact include:

1. grading,

2. t renching ,

3. b a c k f i l l i n g ,

4. r i g h t of way t r a f f i c , and

5. clean-up

These ope ra t i ons a r e discussed i n subsequent s e c t i o n s and i n d i c a t e how

they e f f e c t s o i l s and how t h a t e f f e c t can be avoided o r reduced.

There a r e a number of methods used for s o i l handling and reclamation dur-

ing p i p e l i n e cons t ruc t ion . Although s u b t l e v a r i a t i o n s occur , t h e f i v e

common procedures assessed i n t h i s repor t are:

1. No t o p s o i l s t r i p p i n g ,

2. Trench width t o p s o i l s t r i p p i n g ,

3. Blade width t o p s o i l s t r i p p i n g ,

4. Trench and s p o i l a r e a t o p s o i l s t r i p p i n g , and

5. Trench, s p o i l and work a r ea t o p s o i l s t r i p p i n g .

S e l e c t i o n of the most approp r i a t e soil handling method t o s u i t a s p e c i f i c

p ro jec t should be based on s o i l data c o l l e c t e d during p ro j ec t planning,

land uses , farming p r a c t i c e s and o ther f a c t o r s such a s p ro j ec t t iming and

a n t i c i p a t e d weather cond i t i ons . This r epo r t de sc r ibes the r a t i o n a l e f o r

t h e app l i ca t i on of s p e c i f i c s o i l handling procedures t o given f i e l d s i t u a -

t ions. While except i o n s occur , t he most common a p p l i c a t i o n s of each pro-

cedure a r e addressed.

2.0 IMPACT OF PIPELINE CONSTRUCTION ON AGRICULTURAL LAND

P i p e l i n e cons t ruc t i on equipment opera ted on a g r i c u l t u r a l land can a f f e c t

the p r o p e r t i e s of t h e s o i l . A l t e r a t i o n of s o i l p r o p e r t i e s may change t h e

c a p a b i l i t y of t he s o i l t o s u s t a i n a p a r t i c u l a r land use, thereby, changing

land use c a p a b i l i t y .

Three primary impacts t o a g r i c u l t u r a l s o i l from p i p e l i n e c o n s t r u c t i o n have

been noted. They a r e s o i l mixing, s o i l compaction and s o i l l o s s . No

i n t e n t i o n is made t o q u a n t i f y t h e s e impacts , r a t h e r each is q u a l i t a t i v e l y

d i s cus sed a s a p o t e n t i a l problem.

2.1 SOIL MIXING

The most v i s i b l e impact a s s o c i a t e d with p i p e l i n e cons t ruc t i on on ag r i cu l -

t u r a l l and is the mixing of o rgan ic and n u t r i e n t r i c h t o p s o i l wi th mineral

s u b s o i l which is l e s s f e r t i l e and sometimes t ox i c . Mixing of s o i l s is

u s u a l l y cons idered de t r imen t a l i f t he c a p a b i l i t y of t h e s o i l has been

apprec iab ly lowered.

The d i l u t i o n o r l o s s of o rgan i c s and n u t r i e n t s from t h e roo t zone is a

major e f f e c t of mixing. This d i l u t i o n can a f f e c t p l an t growth t o varying

deg ree s , depending on t h e type of vege ta t ion . Colour comparison of t h e

r ep l aced t o p s o i l with the undis turbed t o p s o i l w i l l g ive a good i n d i c a t i o n

of t h e degree of mixing i n some s o i l s , however, f u r t h e r a n a l y s i s is usua l -

l y r equ i r ed t o s u b s t a n t i a t e t h e problem. For example, while s o i l mixing

might appear t o be ev iden t , t e x t u r e and chemical a n a l y s i s may determine

t h a t l i t t l e or no change i n s o i l c a p a b i l i t y has occurred. Conversely,

some s o i l s e x h i b i t l i t t l e d i f f e r ence i n co lou r between t o p s o i l and sub-

s o i l , l e ad ing one t o conclude t h a t no mixing has occurred. However,

a n a l y s i s may r evea l t h a t , i n f a c t , t h e r e ha s been a chemical change i n

t h e roo t zone m a t e r i a l and a d e f i n i t e reduc t ion i n s o i l c a p a b i l i t y .

Changes i n s o i l chemist ry from mixing poor q u a l i t y s u b s o i l or pa ren t

m a t e r i a l with t o p s o i l , can a l s o nega t i ve ly a l t e r t h e q u a l i t y of t h e r o o t

- 3 -

zone. The i n c o r p o r a t i o n and p e r s i s t e n c e of t o x i c e lements , such a s sod-

ium, i n t h e t o p s o i l , has been shown t o s e v e r e l y restrict p l a n t growth. A s

well, c e r e a l c rops a r e o f t e n t he most s e n s i t i v e t o changes i n t o p s o i l

chemist ry . This e f f e c t can be measured by comparing crop y i e l d s on and

o f f r i g h t of way. L

A t h i r d e f f e c t of mixing is t e x t u r a l change i n t h e rep laced t o p s o i l . *v.

Changes i n t e x t u r e c r e a t e d i f f i c u l t i e s i n seed es tab l i shment and i n devel-

oping good roo t systems, and may cause problems i n seed bed prepara t ion .

For example, mixing c l a y r i c h s u b s o i l s with loamy t o p s o i l not only a l t e r s - t e x t u r a l composi t ion, but may de s t roy s o i l s t r u c t u r e and make t h e t o p s o i l

more d i f f i c u l t t o "work" because of t h e p resence of hard lumps o r c l ods . F - 7

S o i l mixing g e n e r a l l y occu r s when: L

1. no t o p s o i l is s t r i p p e d p r i o r t o t r ench excava t ion , .r I

2. s t r i p p i n g goes beyond t h e t o p s o i l i n t o t h e s u b s o i l hor izons ,

3. s u b s o i l s t o r e d on c u l t i v a t e d o r r e c e n t l y worked t o p s o i l is rep laced ,

4 . r ep l aced s u b s o i l o v e r f l o b s t h e t r ench onto undis tu rbed t o p s o i l , o r

5 . t h e movement and t u r n i n g of c o n s t r u c t i o n equipment d i s p l a c e s top-

s o i l s , mixing t o p s o i l and s u b s o i l t oge the r .

The e f f e c t of mixing on a p a r t i c u l a r s o i l is dependant upon t h e q u a l i t y

and q u a n t i t y of t h e s o i l involved. For example, deep o rgan i c r i c h

Chernozemic t o p s o i l w i l l not be much a f f e c t e d when mixed wi th a smal l

amount of good q u a l i t y s u b s o i l . However, t h i n n e r , poorer q u a l i t y t o p s o i l s

may be g r e a t l y changed i n n u t r i e n t and o rgan i c con t en t , a s well a s i n tex-

t u r a l and chemical composi t ion, when a s i m i l i a r amount of s u b s o i l is mixed

with i t .

Working with s o i l under wet cond i t i ons can a l s o a l t e r s o i l s t r u c t u r e .

When combined with mixing, t h e a s s o c i a t e d problems a r e u sua l l y even more

severe .

2.2 SOIL UIMPACTION

Agricul tura l s o i l s have a c a p a b i l i t y t o support plant growth due t o t h e i r

chemical and physical makeup. I f the physical makeup is a l t e r e d , the cap-

a b i l i t y may a l s o change. So i l compaction is evident i n a number of ways,

such a s poor root pene t r a t ion , d i f f i c u l t c u l t i v a t i o n , and r e s t r i c t e d water

movement through the s o i l . Most important ly, compaction a f f e c t s s o i l

a e r a t i o n by decreasing s o i l poros i ty , lowering oxygen l e v e l s and oxygen

renewal and d i f f u s i o n r a t e s . Lower oxygen l e v e l s i n t he s o i l can:

1. r e s t r i c t p l an t root growth,

2. decrease n u t r i e n t uptake by p l an t s ,

3. decrease absorp t ion of water by p l an t s , and

4. encourage formation of compounds t o x i c t o p lan t growth.

Vegetation is a f a c t o r i n determining the r e l a t i v e s e v e r i t y of s o i l com-

pact ion. For example, some p l an t s , such a s grasses , a r e more t o l e r a n t t o

low oxygen d i f f u s i o n r a t e s . than legume crops and a r e t h e r e f o r e more t o l e r -

ant of compaction.

Severe compaction may cause ponding of water and increased eros ion poten-

t i a l by lowering the s o i l ' s i n f i l t r a t i o n capaci ty. Impeded drainage may

lower s o i l temperature enough t o a f f e c t its a b i l i t y t o provide f o r a s u i t -

a b l e b i o t i c h a b i t a t .

S o i l compaction is highly va r i ab l e and depends on moisture content , par-

t i c l e s i z e d i s t r i b u t i o n ( t e x t u r e ) , compactive e f f o r t , and organic matter

content . For a s p e c i f i c s o i l , there is a maximum dry dens i ty which can be

obtained with a given compactive e f f o r t . A t low moisture content , t h e

i nd iv idua l s o i l p a r t i c l e s r e s i s t compaction. Moisture content of 10% t o

20% w i l l genera l ly allow maximum compaction. Water l u b r i c a t e s t he part-

i c l e s and f a c i l i t a t e s re -sor t ing t o a maximum dens i ty by decreasing t h e

shear ing s t r e n g t h of s o i l s . A t higher moisture contents , t h e s o i l w i l l

not compact, but flow away from s t r e s s . When s o i l s become over s a tu ra t ed ,

deep r u t t i n g usua l ly occurs because the s o i l mater ia l flows r a t h e r than

compacts . - 5 -

Compaction occurs i n both topso i l and subso i l . Topsoil compaction is

e a s i l y remedied through c u l t i v a t i o n . Subsoi l compaction, however, is d i f -

f i c u l t t o overcome, and may p e r s i s t for f i v e o r more years u n t i l the nat-

u ra l f reeze thaw process loosens the s o i l . When subso i l compaction per-

sists or is p a r t i c u l a r i l y severe , deep t i l l a g e may be requi red , however,

success may be l i m i t e d because deep t i l l a g e usual ly br ings some subso i l up

i n t o the topso i l . The most successfu l t reatment of compacted subso i l is

c u l t i v a t i o n before t h e t o p s o i l is replaced.

2.3 TOPSOIL LOSS

The physical l o s s of t o p s o i l w i l l lower the c a p a b i l i t y of the land by

decreasing the amount of a v a i l a b l e n u t r i e n t s and organics i n the root

zone. The severity of the problem is d i r e c t l y r e l a t e d to t h e proport ion

of t opso i l l o s t . I n deep t o p s o i l s of 30 cm, the l o s s of 2 cm is not a

major problem, however, i n t h i n t o p s o i l s o f 6 cm or less, the l o s s of 2 cm

is s i g n i f i c a n t . I n add i t i on , s o i l l o s s may make c u l t i v a t i o n more d i f f i -

c u l t by causing d i f f e r e n t i a l r e s i s t a n c e s i n t h e s o i l t o t he movement o f

farm implements.

~ o ~ s o i l - can be l o s t by wind o r water erosion; subsidence of the t r ench l ine

a f t e r t o p s o i l replacement ; incorpora t ion of undisturbed topso i l i n t o sub-

s o i l mater ia l dur ing b a c k f i l l opera t ions ; and by poor reclamation prac-

t ices .

Construction a c t i v i t i e s causing impeded su r f ace and subsurface dra inage

can acce l e ra t e water e ros ion . The consequence of water e ros ion is s e r i o u s

s ince i t is usua l ly t he f i n e r , more f e r t i l e , s o i l p a r t i c l e s which wash

away f i r s t .

Wind eros ion is a func t ion of wind ve loc i ty , soil c h a r a c t e r i s t i c s , and

s o i l su r f ace condi t ion . So i l handling procedures which r equ i r e excessive

removal of t h e vege ta t ive cover or the e x t r a movement of soil ma te r i a l s

w i l l i nc rease t h e p o t e n t i a l fo r wind eros ion , p a r t i c u l a r i l y i n high wind

a r e a s or with f i n e p a r t i c l e d s o i l s .

3.0 AGRICULTURAL SOILS

'4

S o i l s capable of support ing a g r i c u l t u r e cover 31% of A lbe r t a ' s land area.

. I The s o i l s vary g r e a t l y i n t h e i r physical , chemical and b io log ica l makeup. A l l s o i l s a r e s u s c e p t i b l e t o impact, t he re fo re , handling procedures t o

ensure minimum dis turbance and maximum conservat ion must be designed i n

accordance with the soil's s e n s i t i v i t y . Fac tors which con t r ibu te t o s o i l

s e n s i t i v i t y during p ipe l ine cons t ruc t ion inc lude parent ma te r i a l s , b io t a ,

c l ima te , topography, and the phys ica l and chemical p r o p e r t i e s of the s o i l

i t s e l f . This s e c t i o n addresses t he inf luences of parent mater ia l and s o i l

p r o p e r t i e s , s ince they determine impact which in tu rn determines appro-

p r i a t e s o i l handling procedures.

3.1 PARENT MATERIALS

Most of A lbe r t a ' s s o i l s have formed on s u r f i c i a l ma te r i a l s deposi ted dur-

i n g the l a s t g l a c i a t i o n . Other s o i l s have formed on reworked g l a c i a l

depos i t s o r d i r e c t l y on bedrock.

Parent mater ia l l a r g e l y determines the physical p rope r t i e s of t h e s o i l

formed and i n some cases , such a s marine bedrock, in f luences chemical pro-

p e r t i e s . C h a r a c t e r i s t i c s such a s t ex tu re , s ton ines s , and s t r a t i f i c a t i o n

a r e a l l dependant on parent mater ia l . These c h a r a c t e r i s t i c s in f luence

s o i l c a p a b i l i t y and r e l a t i v e s u s c e p t i b i l i t y t o impact by p ipe l ine con-

s t r u c t i o n . Table 3.1 summarizes t he main f e a t u r e s of t he parent ma te r i a l s

of a g r i c u l t u r a l l ands i n Alberta.

Aeolian ma te r i a l s have been t ranspor ted and deposi ted by wind

a c t ion. Associated landforms a r e dunes and gent1 y m d u l a t ing p l a ins .

Mater ia l s c o n s i s t of medium t o very f i n e sand and a r e well sor ted and

poorly compacted. Low moisture holding capac i ty , low f e r t i l i t y and wind

eros ion hazard preclude a r a b l e a g r i c u l t u r e and make re-establishment of

n a t i v e vegeta t ion or seeded forages d i f f i c u l t .

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F l u v i a l m a t e r i a l s have been t ranspor ted and deposi ted by s t reams and

r i v e r s i n recent o r past times. They conta in grave l , sand, silt and a

minor f r a c t i o n of c lay . Moderately t o well so r t ed , s t r a t i f i e d depos i t s

a r e most common but massive, non-sorted d e p o s i t s a l s o occur. F l u v i a l

landforms inc lude f l oodp la in s , t e r r a c e s , upland p l a i n s and occas iona l ro l -

l i n g t e r r a i n . Low moisture holding capac i ty , low f e r t i l i t y and subsur face

g r a v e l s make the sandy or g rave l ly f l u v i a l depos i t s unsu i t ab l e f o r a r a b l e

a g r i c u l t u r e and make vege ta t ion re-est ablishment d i f f i c u l t . However, sil-

t y and very f i ne sandy loam sediments have developed i n t o prime ag r i cu l -

t u r a l l ands t ha t a r e easy t o reclaim. On a c t i v e f loodpla ins , f looding and

water e ros ion can be a problem.

Fluvial-Aeol ian sediments o r i g i n a t e from stream d e p o s i t s which have

been p a r t i a l l y reworked by wind. These depos i t s occur a s gent ly undulat-

ing p l a i n s with s l o p e s i n t h e 2 t o 5% range. Loamy sand t o sandy loam

t e x t u r e s a r e most common, c o n t r i b u t i n g t o droughty cond i t i ons and low f e r -

t i l i t y , but l e s s s eve re ly than i n aeo l i an depos i t s .

Lacus t r i ne m a t e r i a l s have s e t t l e d from suspension i n s t and ing f r e s h

water. They a r e gene ra l l y f i n e t ex tu red , however, s t r a t i f i e d sands, silts

and c l a y s a l s o occur. Topography is usua l ly l e v e l t o m d u l a t i n g . The

f i n e t e x t u r e d s o i l s a r e well s u i t e d t o a r a b l e ag r i cu l tu re . These s o i l s

tend t o be highly s u s c e p t i b l e t o e ros ion from running water and t o compac-

t i on . Care must be taken when d i s tu rb ing and reclaiming these s o i l s .

Another common problem of these soils is t h a t low permeabi l i ty r a t e s l i m i t

i n t e r n a l d ra inage , making s o i l s d i f f i c u l t t o dry and become workable a f t e r

r a in .

F luv i a l -Lacus t r i ne sediments have been deposi ted by slow moving

water. These d e p o s i t s a r e i n t e r g r a d e s between t h e f i n e sandy t o . s i l t y

f l u v i a l depos i t s and clayey l a c u s t r i n e sediments. Slopes less than 5% a r e

most common. S o i l s developed on these m a t e r i a l s a r e among t h e best i n

Alberta f o r a g r i c u l t u r e , although erosion by su r f ace runoff can be a major

problem.

T i l l (Morainal) d e p o s i t s a r e commonly medium t o f i n e t ex tu red , ston-

ey, n o n - s t r a t i f i e d and well compacted. They were depos i ted by g l a c i e r s

and not modified by water o r wind ac t i on . Topography is usua l ly undulat-

ing t o h i l l y and, i n p l aces , hummocky. Wetlands a r e common i n depres-

s i o n a l a reas . T i l l d e p o s i t s unde r l i e t he l a r g e s t por t ion of the ag r i cu l -

t u r a l a r ea i n t h e province. S ton ines s is a problem, a s well a s s t e e p

s lopes , e ro s ion , and wet lands i n h i l l y and hummocky areas .

Res idua l m a t e r i a l s o r unconsol idated and p a r t i a l l y weathered min-

e r a l s , a r e r a r e l y c u l t i v a t e d . Where they occur they a r e genera l ly covered

with l a c u s t r i n e or t i l l ma te r i a l . Residual m a t e r i a l s a r e predominantly

s i l t y t o c layey and occas iona l ly sandy i n t h e a g r i c u l t u r a l regions. Where

bedrock is of marine o r i g i n , s o d i c i t y , s a l i n i t y or high s a t u r a t i o n percen-

t ages ' a r e t y p i c a l . In most r e s i d u a l m a t e r i a l s permeabi l i ty is r e s t r i c t e d ,

causing shal low l a t e r a l groundwater flow and d i f f i c u l t i e s fo r cons t ruc t ion

and reclamation.

3 -2 SOIL ZONES OF ALBERTA

Albe r t a ' s a g r i c u l t u r a l l ands a r e pr imar i ly d iv ided up i n t o f i v e s o i l

zones, Brown, Dark Brown, Black, Dark Gray and Gray (F igure 3.1 ). Speci-

f i c s o i l o r d e r s predominate i n each zone, fo r example, t h e Chernozems i n

t h e Black s o i l zone. Within each zone, however, l o c a l condi t ions can

cause t he development of s o i l s belonging t o o r d e r s o the r than t h a t of t h e

predominant one. In a d d i t i o n , depending upon paren t mater ia l s , vegeta-

t i o n , c l ima te , and topography, s e v e r a l v a r i a n t s wi th in each order occur

within t h e zonal d i v i s i o n s . The fol lowing s e c t i o n s provide f u r t h e r

d e t a i l s on t he c h a r a c t e r i s t i c s of each zone found i n Alberta and t h e i r

s i g n i f i c a n c e t o p i p e l i n e cons t ruc t ion .

Brown Soil Zone

The Brown S o i l Zone f e a t u r e s a semi-ar id c l ima te and sho r t g rass p r a i r i e

n a t u r a l vege ta t ion . S o i l development is slow with a very t h i n brown s o i l

horizon development o f 5-15 cm t h i c k , con ta in ing l i t t l e organic mat ter

- BROWN SOILS

n .:.:.:.:.:.: ....... - DARK BROWN SOILS

- BLACK SOILS

- DARK GRAY SOILS

( - GRAY SOILS

UNDIFFERENTIATED - MOUNTAIN COMPLEX

FIGURE 3.1

SOIL ZONES OF ALBERTA

(2%). Since annual p r e c i p i t a t i o n is about 300 mm, moisture is a l i m i t i n g

f a c t o r t o crop growth and, because of prolonged droughts, only a few s o i l

types a r e considered a r ab l e . There is l i t t l e o r no colour d i f f e r e n c e bet-

ween the A and B horizons, so i d e n t i f i c a t i o n of t o p s o i l depths by analy-

t i c a l means is c r i t i c a l f o r proper t o p s o i l s t r i p p i n g . High winds, coarse

tex tured s o i l s and the presence of so luab le s a l t s f u r t h e r l i m i t t he capa-

b i l i t y fo r c u l t i v a t i o n and c o n t r i b u t e t o the high s u s c e p t i b i l i t y of these

s o i l s t o impact by p i p e l i n e cons t ruc t ion.

Much of the Brown S o i l Zone is used for l i v e s t o c k range on improved o r

n a t i v e rangeland of mixed-grass-prairie dominated by the Bouteloua-Stipa-

Agropyron community. Bout eloua g r a c i l i s (b lue gramma) and Agropyron

s m i t h i i (western wheat g r a s s ) reproduce vege t a t i ve ly h i l e S t ipa comata

(needle and thread) reproduces pr imar i ly from seed. Consequently, d i s t ur-

bance during t h e dormant pe r iods August t o May, w i l l have a minimal e f f e c t

on the vege ta t ion .

Reclamation of n a t i v e pas tu re is more complex where poorer s o i l s a r e

i n t e r s p e r s e d with t he more f e r t i l e s o i l s . F i e l d s under c u l t i v a t i o n w i l l

be dominated by Chernozems while most n a t i v e range w i l l be Solone tz ic .

Topsoil depth on n a t i v e range w i l l g ene ra l l y be l e s s than i n c u l t i v a t e d

a reas . For most n a t i v e range t h e r e w i l l be l i t t l e t o p s o i l development

below t h e sod l aye r .

I r r i g a t i o n , which is employed on the b e t t e r q u a l i t y brown s o i l s i n t he

Taber, Brooks, and Medicine Hat a r ea s , poses s p e c i a l problems fo r p i p e l i n e

cons t ruc t ion . Imp l i ca t i ons of p i p e l i n e cons t ruc t ion on i r r i g a t i o n is

discussed f u r t h e r i n s e c t i o n 5.44.

Dark Brown Soi l Zone

The Dark Brown S o i l Zone is s l i g h t l y less a r i d than the Brown S o i l Zone.

Annual p r e c i p i t a t i o n r a t e s of about 350 mm with wide v a r i a b i l i t y from year

t o year is the main l i m i t a t i o n t o crop production and t o p i p e l i n e reclama-

t i o n . S o i l s of t h i s zone have 10-20 cm of su r f ace horizon t h a t is dark

brown and con ta in s about 4% organic mat ter . A s l i g h t colour d i f f e r e n c e

- 12 -

can e x i s t between t h e A and B horizons and can be used t o i d e n t i f y top-

s o i l . Where t h i s co lour d i f f e r ence does not e x i s t , i d e n t i f i c a t i o n of top-

s o i l by a n a l y t i c methods may be required.

Black Soil Zone

The Black S o i l Zone occurs i n a r e a s with a dry-subhumid c l ima te ; i n gen-

e r a l the parkland por t ion of t he province. R a i n f a l l v a r i e s from an annual

average o f 380 m along the southeas te rn edge inc reas ing t o 460 mm on t h e

nor thern and western ex t r emi t i e s . A band of Black s o i l s with t h i n (15 cm)

s u r f a c e horizons occur along t h e boundary t o t h e Dark Brown s o i l s . The

- remainder of the zone con ta in s s o i l s t h a t have a deeper black s u r f a c e hor-

i zon (25-30 cm). Organic mat ter content of t h e su r f ace horizons averages

, 4 about 8%. A wide range of c rops can be grown on the Black soils and pro-

duct i v i ty is gene ra l l y high.

I Dark Gray Soil Zone

North and west of the Black S o i l Zone l ies a narrow s t r i p of s o i l s c l a s s i -

f i e d i n t o t he Dark Gray S o i l Zone. Dark Gray S o i l s a l s o predominate t he

Peace River a rea of t he province. These have t h i n , dark gray t o p s o i l s

with a l i g h t g ray ish brown l a y e r below.

Gray Soil Zone

Gray s o i l s which comprise t he rest of t he a g r i c u l t u r a l s o i l s i n t h e pro-

v ince occur i n a r e a s of subhumid c l imate and usua l ly have a continuous

tree cover. Ra in fa l l v a r i e s from 480 t o 560 mm i n t h e southwestern por-

t i o n of the province t o 300 t o 350 mm i n t h e northern por t ion . S o i l s a r e

cha rac t e r i zed by a l e a f mat, a t h i n dark s u r f a c e horizon less than 5 cm i n

t h i cknes s , a l i g h t gray p l a ty s t r u c t u r e d subsur face horizon and a s t r o n g l y

s t r u c t u r e d subso i l . Low i n n a t u r a l f e r t i l i t y , coarse g r a i n s and forages

a r e t he p r i n c i p a l c rops grown on these soils. Careful s o i l management is

requi red t o achieve good product iv i ty .

h ' Although not s p e c i f i c a l l y addressed i n t h i s document, c l imate p lays a s ig-

n i f i c a n t r o l e i n t h e formation of s o i l s and has d i r e c t imp l i ca t i ons t o

p i p e l i n e cons t ruc t ion . Import ant c l i m a t i c f e a t u r e s of t he s o i l zones and C

t h e i r imp l i ca t i ons t o p i p e l i n e cons t ruc t ion a r e presented i n Table 3.2.

h

3.3 SOIL ORDERS OF ALBERTA

b f

Arable a g r i c u l t u r e i n Alberta i s concent ra ted on a l l t h e g rea t groups o f

t h e Chernozemic and So lone t z i c o rde r s a s well a s on the Gray Luvisol g r ea t

group of t h e Luv i so l i c order . The d i agnos t i c f e a t u r e s and c h a r a c t e r i s t i c s

o f each of t h e s o i l o rde r s and t h e i r imp l i ca t i ons t o p i p e l i n i n g a r e

d i scussed i n t h e fol lowing s e c t i o n s . However, a s d i scussed i n Sec t ion

3.1, the type of , paren t ma te r i a l on which each s o i l o rder is developed

g r e a t l y a f f e c t s t h e s o i l ' s c h a r a c t e r i s t i c s .

Chernozemic S o i l s

Chernozemic s o i l s (Tables 3.3 and 3.4) a r e well t o imper fec t ly drained

s o i l s having s u r f a c e horizons darkened by organic matter from decomposed

g ra s se s and f o r b s r e p r e s e n t a t i v e of g rass land communities o r grassland-

f o r e s t communities with assoc ia ted shrubs and forbs . Their A and B hori-

zons a r e p e r i o d i c a l l y dry each summer. Chernozemic s o i l s have an A hori-

zon i n which organic mat ter has accumulated (Ah, Ahe, Ap), which meets the

requirements of a chernozemic A horizon ( i e . a t l e a s t 10 cm th i ck , con-

t a i n i n g 1 t o 17% o rgan ic carbon e t c . ).

Luviso l ic S o i l s

S o i l s of t h e Luv i so l i c order (Tables 3.3 and 3.4) have l igh t -co loured ,

e l u v i a l hor izons (Ae) and i l l u v i a l B horizons (Bt ) i n which s i l i c a t e c lay

has accumulated. Only t h e Gray Luvisol g r ea t group of t h e Luv i so l i c o rde r

i s recognized i n Alber ta . The Gray Luviso ls usua l ly have s u r f a c e L , F,

and H horizons and may have a degraded Ah o r Ahe horizon t h a t resembles

t h e upper A horizon of Dark Gray Chernozemic s o i l s . The underlying Ae

horizon is well developed, f r i a b l e and p l a t y i n s t r u c t u r e . The Gray

Luviso ls commonly have an AB o r BA horizon below the Ae horizon i n which

- 14 -

TABLE 3.2

CLIMATIC FEATURES OF THE SOIL ZONES AND THEIR

IMPLICATIONS TO PIPELINE CONSTRUCTION

S o i l Zone Summer Winter

Brown Low r a i n f a l l , very warm Cold temperatures , winds and temperatures , f requent snow storms with apprec iab le high winds. Wind e ros ion snow accumulation a t t imes. hazard; d i f f i c u l t t o Pe r iod i c warm Chinook winds. e s t a b l i s h vegetat ion. Al te rna t ing co ld and warm

temperatures cause wet s l i ppe ry cond i t i ons and v a r i a b l e f r o s t depth. Deep snow hampers a c c e s s i b i l i t y .

Dark Brown - Same a s Brown Zone

Black Ample r a i n f a l l , except i n Cold temperatures, s o i l s Ft. Vermilion a r ea , warm frozen to grea t depth (1 t o t o cool temperatures , 2 m) most winters . occas iona l heavy and pro- Occasional thaws r e s u l t i.n longed r a i n f a l l . s l i p p e r y condi t ions . Deep

snow and pe r iod i c b l i z z a r d s hamper access . "Cloddy" frozen ma te r i a l s make reclamation and clean-up d i f f i c u l t , o f t en r equ i r ing a f i n a l grooming i n spr ing .

Gray and - Same a s Black Zone Dark Gray

TABLE 3.3 FEATURES OF THE SOIL ORDERS OF ALBERTA

Horizon Sequence

Average Depth of Topsoi 1

Average Depth From Surface t o Bottom o f B Horizon

Colour o f Topsoi l

Colour o f B hor izon

S a l i n i t y and Sod ic i t y

L UVISOL I C ORDER

L-H, Ah, Ae, AB, Bt, Ck

0- 5 cm i f not c u l t i v a t e d 0-15 cm i f c u l t i v a t e d

70-80 cm

Gray t o Dark Grayish Brown

Brown t o Very Dark Grayish Brown

Low

CHERNOZEMIC ORDER

Ah(p), om, Ck

10-15 cm i n Brown S o i l Zone 15-20 cm i n Dark Brown S o i l Zone 30 cm i n Black S o i l Zone

35-50 cm i n Brown S o i l Zone 50-60 cm i n Dark Brown S o i l Zone 70-100 crn i n Black S o i l Zone

Brown, Dark Brown, Black (depends on s o i l zone)

Brown i n Brown S o i l Zone (no co lou r change Brown t o Dark Brown i n Dark Brown S o i l Zone ( l i t t l e t o no co lou r change) Ye l lowish Brown i n Black S o i l Zone (colour change)

Low t o moderate i n Brown and Dark Brown S o i l Zones Low i n Black S o i l Zone

SOL ONETZ I C ORDER

Ah(p), Bn( t ) , Csk - (Solonetz) Ah, Ae, (Ap), Bn( t ) , Csk - (Solodized Solonetz) Ah, Ae, (Ap), AB, Bn(t) , Csk - (Solod)

0- 5 cm i n Gray S o i l Zone 5-10 cm i n Brown S o i l Zone

15 cm i n Dark Brown S o i l Zone 15-20 cm i n Dark Gray S o i l Zone

20 cm i n Black S o i l Zone

25-40 cm i n Brown S o i l Zone 40-50 cm i n Gray S o i l Zone 40-60 cm i n Dark Brown S o i l Zone 50-60 cm i n Black and Dark Gray S o i l Zones

Brown, Dark Brown, Black, Dark Gray, Gray (depends on s o i l zone)

Brown t o Dark Brown i n Brown S o i l Zone Dark Brown i n Dark Brown S o i l Zone Very Dark Grayish Brown i n Black S o i l Zone Dark Brown t o Very Dark Grayish Brown i n Gray and Dark Gray S o i l Zones

Moderate i n Gray S o i l Zone Moderate t o High i n Dark Gray and Black S o i l Zones High i n Brown and Dark Brown S o i l Zones

TABLE 3.4 ASSOCIATED IMPACTS TO THE SOIL ORDERS OF ALBERTA

SOLONETZIC ORDER

- d i l u t i o n of organics and n u t r i e n t s where t o p s o i l depths are l e s s than 20 cm. Change i n t e x t u r a l and chemical composi- t i o n o f t opso i l i f mixed w i t h Bnt horizon.

- t e x t u r a l d i f f e rence between A and B horizons makes t o p s o i l suscept ib le t o eros ion by running water. D i f f i c u l t t o rees tab l i sh vegetat ion t o c o n t r o l erosion.

-B hor izon i s subject t o compact i o n when moist.

(1) The 'hard' nature o f the Bnt hor izon can be used t o c o n t r o l the s t r i p p i n g depth when the s o i l i s dry.

( 2 ) High s a l i n i t y and s o d i c i t y values may make vegetat ion establ ishment d i f f i c u l t .

LUVISOLIC ORDER ,

- d i l u t i o n o f organics and n u t r i e n t s , a problem because o f shal low t o p s o i l depths i f Ae hor izon i s incorporated i n t o topso i l . Incorpora t ion o f c lay enr iched B t horizon i n t o t o p s o i l w i l l change t e x t u r a l composit ion o f the topso i l .

- t e x t u r e o f Ae, i f incorporated i n t o topso i l , w i l l r e s u l t i n h igh r i s k o f erosion by wind and water. Textural change between A and B horizons makes d is tu rbed areas suscept ib le t o erosion, p a r t i c u l a r l y by running water.

- B t hor izon i s subject t o compact i o n when m i s t .

(1) Tex tura l change between the Ae and B t horizons can a s s i s t when s t r i p p i n g topso i l .

(2) Low n a t u r a l f e r t i l i t y o f these s o i l s may make vegeta t ion establishment d i f f i c u l t .

S u s c e p t i b i l i t y t o : Mix ing

Loss

Compaction

Imp l i ca t i ons t o P ipe l i ne Construct ion

CHERNOZEMIC ORDER

- d i l u t i o n o f organics and n u t r i e n t s , a problem where t o p s o i l depths are l ess than 20 cm. Lack o f co lour change between A and B horizons may r e s u l t i n poor d e f i n i t i o n o f t o p s o i l dur ing t o p s o i l s t r i p p i n g .

- l o s s o f t o p s o i l i s c r i t i c a l where t o p s o i l depths are l ess than 15 cm.

(1 ) Usua l l y l i t t l e t e x t u r a l change between A and B horizons, therefore, s t r i p p i n g should be based on co lou r change when i t occurs o r by set depth.

(2) Because o f the low s a l i n i t y and s o d i c i t y associated w i t h these s o i l s and the minor t e x t u r a l d i f fe rences between t h e A and B horizons, mix ing of the A and B horizons t o accommodate s o i l handl ing i n adverse cond i t ions w i l l u s u a l l y not r e s u l t i n a major change i n c a p a b i l i t y .

t h e ped* s u r f a c e s a r e grayer than t h e i r i n t e r i o r . The underlying B t hor i -

zons have moderate t o s t r o n g pr i smat ic or blocky s t r u c t u r e s . The C hor i -

zon is gene ra l l y ca lcareous . The solum* of Gray Luviso ls is gene ra l l y

s l i g h t l y t o moderately ac id but may be s t rong ly a c i d i c . The degree o f

base s a t u r a t i o n is gene ra l l y high.

In the Gray Luviso ls , t he colour change between the Ae and B t is moderate-

l y good and can be used along with s o i l s t r u c t u r e a s a c r i t e r i a fo r top-

s o i l salvage. The ash coloured Ae horizon is a leached horizon, p l a ty i n

s t r u c t u r e , a c i d i c i n na tu re and d e f i c i e n t i n n u t r i e n t s .

- Gray Luviso ls occur t y p i c a l l y under boreal o r mixed f o r e s t vege ta t ion and

i n fores t -grass land t r a n s i t i o n zones i n a wide range of c l i m a t i c a reas .

They a r e l i m i t e d fo r a g r i c u l t u r a l use by a sho r t growing per iod , low na t -

u r a l f e r t i l i t y and organic mat ter conten t , and r equ i r e c a r e f u l management

p rac t i ce s . Supplement a1 f e r t i l i z a t i o n is requi red fo r good y i e ld s . About

10% of the Gray Luvisols a r e p re sen t ly c u l t i v a t e d , however, a s farming

expands i n t h e Peace River District, more of t he se s o i l s may come under

c u l t i v a t i o n .

Solonetzic Soils

S o i l s of t h e So lone t z i c o rde r (Tables 3.3 and 3.4) have B horizons t h a t

a r e very hard when dry and swell t o a s t i c k y mass of low permeabi l i ty when

wet. Typica l ly the s o l o n e t z i c B horizon has p r i sma t i c o r columnar

macros t ruc ture t h a t breaks i n t o hard or extremely hard, blocky peds with

dark coa t ings . They have developed on s a l i n e parent m a t e r i a l s i n some

a r e a s of t he semiar id t o subhumid I n t e r i o r P l a i n s i n a s s o c i a t i o n with

Chernozemic s o i l s , and t o a lesser ex ten t with Luv i so l i c and Gleysol ic

s o i l s .

* peds - t he m i c r o s t r u c t u r a l u n i t s i n t o which a s o i l w i l l e a s i l y break up.

* solum - t h e a c t i v e soil forming s e c t i o n of the upper s o i l p r o f i l e .

Solonetz ic soils a re thought t o have developed from parent ma te r i a l s t h a t

were more or less uniformly s a l i n i z e d with s a l t s high i n sodium. Leaching

o f s a l t s by water percola t ion r e s u l t s i n de f loccu la t ion of t he sodium-

sa tu ra t ed co l lo ids . The c o l l o i d s a r e c a r r i e d downward and deposi ted i n

t he B horizon. Fur ther leaching deple tes t he a l k a l i c a t i o n s i n t h e A

horizon, which becomes a c i d i c and usual ly develops a p l a t y Ae horizon.

The underlying B horizon normally c o n s i s t s of darkly s t a ined , fused,

i n t a c t columnar peds.

The 'hard ' nature of the so lone tz i c B horizon provides a sharp c o n t r a s t

between t o p s o i l and subso i l even though colour d i f f e r ences may not e x i s t .

When s t r i p p i n g dry t o p s o i l by grader, the blade has a tendency t o r i d e on

t h e top of the s o l o n e t z i c B r e s u l t i n g i n good sepa ra t ion of t opso i l from

subsoi l .

The Solonetzic order inc ludes th ree grea t groups: Solonetz, Solodized

Solonetz , and Solod. They a re separated on the bas i s of the degree of

expression of the Ae horizon and the breakdown of t he upper pa r t of t h e B

horizon :

Solonet z

No continuous Ae horizon. An i n t a c t , columnar Bnt o r Bn horizon.

Solodized Solonetz

An Ae horizon a t l e a s t 2 cm th ick . An i n t a c t , columnar Bnt or Bn

horizon.

Solod

An Ae horizon a t l e a s t 2 cm thick. A d i s t i n c t AB o r BA horizon

( d i s i n t e g r a t i n g Bnt).

Gleysolic Soils

S o i l s of t h e Gleysol ic Order a r e c u l t i v a t e d to some exten t i n t h e c e n t r a l

and northern por t ions of the province. These soils have f e a t u r e s indica-

t i v e of per iodic or prolonged s a t u r a t i o n with water and chemical reducing

- 19 -

condi t ions . They commonly occur i n a s soc i a t i on with o the r s o i l s i n t h e

landscape. In a r e a s of subhumid c l imate , Gleysol ic s o i l s a r e found i n

shallow depress ions and on l e v e l lowlands s a tu ra t ed with water every

spr ing. Gleyso l ic s o i l s a r e usua l ly a s soc i a t ed with e i t h e r a high ground-

water t a b l e a t some per iod of the year o r temporary s a t u r a t i o n above a

r e l a t i v e l y impermeable layer . Some Gleysol ic s o i l s may be submerged under

shal low water throughout the year.

Gleyso l ic s o i l s a r e divided i n t o t h r ee g rea t groups; Humic Gleysol ,

Gleysol and Luvic Gleysol, which a r e separa ted on the b a s i s of t he devel-

opment of the Ah horizon and the presence o r absence of a B t . horizon:

Humic Gleysol

Ah is a t l e a s t 10 crn th ick : no B t horizon.

Gleysol

No Ah o r Ah is <I0 cm th ick : no B t horizon.

L uvic Gleysol

Btg horizon is presen t , an Ahe o r an Aeg horizon may be presen t .

Since g l e y s o l i c s o i l s a r e wet and poorly drained for a l a r g e par t of t h e

year , p i p e l i n e cons t ruc t ion may c r e a t e major impacts. Some of t he major

imp l i ca t i ons a re :

(1) Standard p i p e l i n i n g machinery cannot be used and a backhoe is o f t e n

used f o r t renching r e s u l t i n g i n l a r g e r volumes of subso i l being

excavated.

(2) Topsoil may be d i f f i c u l t t o s t r i p under wet condi t ions .

(3) Pipe l in ing on wet s o i l s w i l l r e s u l t i n s o i l s t r u c t u r e degrada t ion ,

c lodding of m a t e r i a l s and g r e a t e r compact ion.

( 4 ) F i n a l c l ean up and grooming is d i f f i c u l t due t o clodding and s o i l

s t r u c t u r e degradat ion.

- 20 -

( 5 ) Water accumulation from heavy r a i n s w i l l cause longer cons t ruc t ion

de lays i n Gleysol ic s o i l a r eas than i n t h e b e t t e r drained adjacent

s o i l s .

( 6 ) These s o i l s f r eeze harder and to g rea t e r depths than ad jacent b e t t e r

drained s o i l s .

(7) Revegetation w i l l r equ i r e wetland t o l e r a n t spec ies .

4.0 PIPELINE CONSTRUCTION

The movement of ma te r i a l s and equipment required t o cons t ruc t a p ipe l ine

has a d i r e c t a f f e c t on a g r i c u l t u r a l s o i l s . Impacts w i l l vary according t o

type of soil , time of year , type of equipment used and methods of equip-

ment operat ion. The primary impacts t o t h e s o i l from p i p e l i n e construc-

t i o n on a g r i c u l t u r a l lands, a s discussed i n Sec t ion 2, include:

( a ) s o i l mixing,

(b ) s o i l compaction, and

( c ) s o i l l o s s .

Conservation of a g r i c u l t u r a l s o i l s can be achieved by recogni t ion of t h e s e

problems, how they a r e caused by p i p e l i n e cons t ruc t ion , and t h e implemen-

t a t i o n of procedures t o minimize them. The following s e c t i o n s d i scuss t h e

e f f e c t of p i p e l i n e cons t ruc t ion on s o i l conservat ion.

4.1 , PIPE SIZE

One var iab le which determines the impact of p i p e l i n e cons t ruc t ion on s o i l s

is the diameter of t he pipe. Right of way widths, grading requirements,

t rench s i z e and a s soc i a t ed mater ia l s to rage requirements a r e a l l d i c t a t e d

by the s i z e of the pipe. Although most p ipe l ine cons t ruc t ion causes some

a g r i c u l t u r a l impact, the "big inch" p i p e l i n e s of diametres 406.4 mm (16")

o r more genera l ly c r e a t e t h e most su r face dis turbance. They a r e r e l a t i v e -

l y i n f l e x i b l e , r equ i r ing more grading and more su r f ace dis turbance.

Trenches a re wide and n e c e s s i t a t e t h e handling of l a r g e r volumes of sub-

s o i l ma te r i a l s , i nc reas ing the p o s s i b i l i t i e s fo r s o i l mixing and lo s s .

Larger and heavier equipment is requi red i n big inch p i p e l i n e construc-

t i o n , increas ing the poten t i a1 for s o i l compaction. Small inch pipe, l e s s

than 406.4 mm i n diameter, is more f l e x i b l e , r e q u i r e s less grading and can

be placed i n narrower t renches.

4.2 RIGHT OF WAY WIDTH

For most r i g h t s of way, common p r a c t i c e is t o l o c a t e t he t rench one t h i r d

from the s p o i l s ide , giving t h e cont rac tor two t h i r d s of t h e r i g h t of way

on the work s ide . Storage requirements for small inch l i n e s a r e i n t h e

order of 6.5 m to 9.0 m on the s p o i l s i d e t o accommodate t h e s p o i l and

topso i l p i l e s i n a t y p i c a l s i t u a t i o n (Sec t ion 5.1). This l eaves approxi-

mately 6.0 m - 8.5 m ava i l ab l e t o t h e con t r ac to r for a l l h i s a c t i v i t i e s on

a s t anda rd 15 m r i g h t of way. Most con t r ac to r s f e e l t h a t 10 m is requi red

t o do a proper job a s a narrow, confining work space may inc rease con-

s t r u c t ion c o s t s by reducing cons t ruc t ion e f f i c i ency . F igu re 4.1 o u t l i n e s

t y p i c a l r i g h t of way width cons idera t ions fo r big and small inch s i t u a -

t ions.

The work s i d e of the r i g h t of way c o n s i s t s of t he pipe lay-up a rea , t h e

work a rea , and t r a v e l area. Typical work widths for small inch l i n e s

include:

a. The lay-up area, which provides space fo r welding and coa t ing ,

r e q u i r e s 1.5 m;

b. The work area , where t h e sidebooms and welders opera te ,

r e q u i r e s 4.5 m; and

c. A t r a v e l area of 4 m allows access of s e r v i c e veh ic l e s along

the r i g h t of way.

There has been pressure on and within the indus t ry t o reduce r i g h t of way

widths i n order to minimize land d is turbance and reduce land a c q u i s i t i o n

cos t s . With requirements for t o p s o i l salvage, and sepa ra t ion of t o p s o i l

and s p o i l windrows, t h e work space a v a i l a b l e t o t he c o n t r a c t o r has

decreased. It is usua l ly t he conservat ion of s o i l s and not t he a c t u a l

cons t ruc t ion of the p ipe l ine which is jeopardized when r i g h t of way widths

a r e r e s t r i c t e d .

Although cos t cons idera t ions a r e important, t h e width of t h e r i g h t of way

should be appropr ia te t o the s c a l e of t he p ipe l ine p ro j ec t ; i n s u f f i c i e n t

r i g h t of way can inc rease c o s t s and su r f ace damage. This is p a r t i c u l a r i l y

t r u e where e x t r a grading is required, a t a r eas of wide o r deep t rench ,

- 23 -

R/W BDY.

I

I S P O I L S I D E WORKING S I D E I - I RIGHT OF WAY I

( S e e N o t e I Re: R/W W i d t h )

PROFILE N.T. S.

1. PRIOR TO CONSTRUCTION, DETERMINE STANDARD RIGHT OF WAY WIDTH AND LOCATIONS REQUIRING A D D I T I O N A L RIGHT OF WAY* MERCHANTABLE TIMBER CAN THEN BE CLEARED AND SALVAGED, AND TOPS0 I L CAN BE STRIPPED AND STOCKPILED SEPARATELY FROM SPOIL .

RIGHT OF WAY WIDTH CONSIDERATIONS I A) NO- OF P I P E L I N E S

- SINGLE - M U L T I P L E

B) P I P E DIAMETER - SMALL INCH - B I G INCH

C ) WORKING SPACE - CROSS 1 NGS - EXPANSION LOOPS - PASSING LANE

L E S S -MORE R / W R / W

F ) GRADING - NONE - EXTENSIVE

G ) TRENCH MATERIAL - CLAY - SAND - R O C K (BLASTING)

H) DEPTH O F COVER - I n - 3 H

D ) SLASH DISPOSAL I) WATER TABLE - BURNING X - LOW - TOTAL ROLLBACK X - H I G H

LESS MORE R / W R / W

E ) TOPSOIL S T R I P P l NG J ) TRENCHING E Q U l PMENT - WIDTH - NONE X ' - WHEEL X - FULL R / W x - HOE x

- DEPTH - 6 CM x - 30 CM x

FIGURE 4.1

PIPELINE RIGHT OF WAY

f o r e i g n l i n e c r o s s i n g s , road c r o s s i n g s and a t p i p e l i n e t i e - i n s . For exam-

p l e , it is still a predominant p r a c t i c e not t o t a k e e x t r a r i g h t of way a t

road c r o s s i n g s d e s p i t e t h e n e c e s s i t y f o r e x t r a equipment and excess sub-

s o i l excava t ion fo r road bor ing. I n v a r i a b l y , s u b s o i l p i l e s a r e placed t o o

c l o s e o r on top of t o p s o i l p i l e s caus ing mixing o r l o s s of t o p s o i l . Poor

a l l e v i a t i o n of compaction and t r e s p a s s of c o n s t r u c t i o n equipment o f f r i g h t

o f way a r e a l s o common r e s u l t s of i n s u f f i c i e n t r i g h t of way.

Righ t of way and e x t r a work space requirements should be c a l c u l a t e d on a

s i t e s p e c i f i c b a s i s , t a k i n g equipment, procedures and s o i l s i n t o cons ider -

a t i o n . A method f o r c a l c u l a t i n g r i g h t of way width requirements based on

t o p s o i l and s u b s o i l s t o r a g e requ i rements is o u t l i n e d i n t h e fo l lowing

c h a p t e r i n s e c t i o n 5.1.

4.3 CONSTRUCTION OPERATIONS

P i p e l i n e c o n s t r u c t i o n is t y p i c a l l y broken down i n t o a s e r i e s of o p e r a t i o n s

beginning with r i g h t of way p r e p a r a t i o n and ending with f i n a l c l e a n up.

Although each o p e r a t i o n h a s t h e p o t e n t i a l t o impact a g r i c u l t u r a l land, t h e

major s u r f a c e d i s t u r b i n g a c t i v i t i e s a r e g rad ing , t r ench ing , b a c k f i l l i n g ,

r i g h t of way t r a f f i c and c l e a n up.

4.31 Right o f Way Preparat ion

P r e p a r a t i o n of t h e p i p e l i n e r i g h t o f way c o n s i s t s of s e v e r a l a c t i v i t i e s :

f ence opening or b u i l d i n g , c l e a r i n g and g rad ing ( i n c l u d i n g t o p s o i l s t r i p -

p i n g ) , and s t r i n g i n g p i p e j o i n t s . Of t h e s e a c t i v i t i e s , grading is t h e

most important i n terms of p o t e n t i a l s o i l damage.

The g rad ing crew performs two o p e r a t i o n s ; ( 1 ) r i g h t of way grading and

l e v e l l i n g , t o a l low f o r t h e passage of c o n s t r u c t i o n equipment and t o meet

t h e bending l i m i t a t i o n s of t h e p ipe , and (2) t o p s o i l sa lvage .

Topso i l s a l v a g e is normally c a r r i e d out with a motor-grader s i n c e i t can

a c c u r a t e l y s e p a r a t e t o p s o i l from s u b s o i l . This o p e r a t ion may be a s s i s t e d

by dozers when t h e windrows become t o o l a r g e t o be e f f e c t i v e l y handled by

- 25 -

t h e grader . I t is common p r a c t i c e fo r t h e c o n t r a c t o r t o employ a combina-

t i o n of g r a d e r s and dozers depending on t h e equipment a v a i l a b l e t o him on

t h e s p r e a d , t h e depth of t o p s o i l , and t h e procedure used t o remove t h e

t o p s o i l . Land use may a l s o determine t h e c h o i c e of equipment. For exam-

p l e , s t r i p p i n g t o p s o i l on t r e e d a g r i c u l t u r a l l and might be mare e f f e c t i v e -

l y done by dozer which can more r e a d i l y move r o o t masses.

D e s c r i p t i o n s of equipment used f o r g rad ing and s t r i p p i n g a r e i n c l u d e d i n

S e c t i o n 4.4.

4.32 Installation

While i n s t a l l a t i o n of t h e p i p e l i n e i n v o l v e s a number of s p e c i a l i z e d opera-

t i o n s , i t is t h e excava t ion o f t h e t r e n c h which most a f f e c t s s o i l conser-

va t ion .

Trenching

In good ground c o n d i t i o n s t h e t r e n c h is t y p i c a l l y excavated with a wheel

t r e n c h e r which has a r a t e of excava t ion i n t h e range of 0.1 t o 0.4 kph.

Backhoes a r e used i n main l ine t r e n c h i n g where wheel t r e n c h e r s a r e i n e f f e c -

t i v e , such a s wet ground c o n d i t i o n s and a t t i e - i n s , road c r o s s i n g s , l o c a l

wet a r e a s and f o r e i g n l i n e c r o s s i n g s . The r a t e of p r o g r e s s f o r a backhoe

i n main l ine t r e n c h i n g is approx imate ly 0.1 kph, (one-four th t h e bes t r a t e

o f a t r e n c h e r ) .

The p o t e n t i a l f o r s u r f a c e d i s t u r b a n c e is d i r e c t l y r e l a t e d t o t h e width of

t h e t r ench . The wider t h e t r e n c h , t h e more r i g h t of way r e q u i r e d f o r t h e

t r e n c h i t s e l f and s t o r a g e of s p o i l genera ted from t h e t r e n c h . The depth

of t r e n c h is governed by t h e diameter of t h e p i p e and t h e minimum cover

over t h e pipe. Energy Resources Conservat ion Board r e g u l a t i o n s s t a t e t h a t

a minimum o f 80 cm of cover is r e q u i r e d over a l l p i p e l i n e s . I n s p e c i f i c

a r e a s t h e p ipe may be b u r i e d even deeper s o a s not t o i n t e r f e r e with irri-

g a t i o n and l and d ra inage systems. Apart from p i p e diameter , t h e width of

t h e t r e n c h is g e n e r a l l y determined by t h e type o f machine used t o excava te

t h e t r ench . - 26 -

Protec t ion of the pipe wal l s and i n p a r t i c u l a r , t he p r o t e c t i v e pipe coat-

i ng is a major concern when the pipe is lowered i n t o the t rench. I f t h e

t rench wal l s a r e smooth, s o f t , and f r e e of sharp s tones , t he pipe can be

lowered i n t o the t rench with no damage to t h e p r o t e c t i v e coa t ing even i f

t h e pipe contac ts the t rench walls. Some companies be l i eve t h a t for safe-

t y , the trench should be s i zed so t h a t a space equivalent t o t he diameter

o f the pipe is l e f t on each s i d e of the pipe. Others be l i eve t h a t a mini-

mum o f 30 cm should be l e f t on each s i d e of t he pipe r ega rd l e s s of p ipe

s i z e t o minimize the r i s k of damaging the p r o t e c t i v e coa t ing and t o al low

b a c k f i l l mater ia l to flow under t he pipe.

Standard widths of small inch t renchers a r e i n t he order o f 80 cm t o

90 cm. In good s o i l condi t ions pipe diameters up t o 610 mm (24") can

e a s i l y be accommodated. These same t r enche r s a r e commonly used for s t a n -

dard small inch pipe s i z e s of only 60.3 mm or 114.3 mm i n diameter. I n

such cases l e s s than 1/8 of the t rench width is taken up by the pipe.

A l a r g e percentage of the pipe i n s t a l l e d i n a g r i c u l t u r a l a r e a s is

168.3 mm, 114.3 mm, 88.9 mm and 60.3 mm i n diameter. Trenches excavated

any wider than 30 cm, which provides an adequate width fo r these pipes, is

o f no addi t iona l bene f i t . The e x t r a trench width r e q u i r e s more r i g h t of

way to accornodate the t rench i t s e l f and s to rage of t he t rench s p o i l . A

wider t rench and l a r g e r s p o i l s to rage a rea r equ i r e s a wider a rea t o be

s t r i p p e d of t opso i l and more r i g h t of way fo r t opso i l s torage . The con-

s e r v a t i o n of s o i l s can be more r ead i ly achieved i f t h e t rench width and

diameter of pipe t o be i n s t a l l e d a r e more c l o s e l y matched.

Backfillinq

After t h e pipe has been welded, and lowered i n t o t h e t rench , t h e t rench is

b a c k f i l l e d , and the r i g h t of way reclaimed. The replacement of excavated

s p o i l back i n t o the t rench is a c r u c i a l operat ion i n t h e conserva t ion of

a g r i c u l t u r a l s o i l . Proper s t r i p p i n g , s torage , and sepa ra t ion of t he s p o i l

from the topso i l he lps prevent mixing during b a c k f i l l i n g . Separa te s t o r -

age of s p o i l from t o p s o i l f a c i l i t a t e s the ease and e f f i c i e n c y of b a c k f i l l -

ing. I f s p o i l is s to red on t o p s o i l i t w i l l be d i f f i c u l t , i f not

- 27 -

imposs ib le , t o s e p a r a t e t h e s p o i l wi thout mixing i t and t h e under ly ing

t o p s o i l .

Machinery used f o r b a c k f i l l i n g i n c l u d e s conven t iona l equipment ( d o z e r s and

g r a d e r s ) a s wel l a s power augers , power d o z e r s , mormon boards , and back-

hoes ( S e c t i o n 4.4).

Excavated t rench s p o i l n a t u r a l l y i n c r e a s e s i n volume ( b u l k s ) by approxi-

mately 20% when d i s t u r b e d , and with t h e p ipe i n t h e t r e n c h , r e t u r n e d s p o i l

volumes o f t e n exceed t h e o r i g i n a l t r e n c h volume. The amount of expansion

depends on t h e m a t e r i a l . For example, bedrock c l a y s expand more than

l a c u s t r i n e c l a y s . S tandard p r a c t i c e is t o compact t h e r e t u r n e d t r e n c h

s p o i l wi th g rader tires or a dozer t r e a d . Excess s p o i l is mounded over

t h e t r e n c h l i n e t o a l low f o r subs idence and f e a t h e r e d out over t h e s t r i p p e d

a r e a .

A mound over t h e t r e n c h l i n e can a f f e c t farming a c t i v i t i e s i n a number of

ways; i n t e r f e r e n c e wi th farm equipment o p e r a t i o n s , t h i n n e r t o p s o i l

replacement , and d i s r u p t i o n of s u r f a c e d ra inage . Normal c u l t i v a t i o n w i l l

g r a d u a l l y r e s t o r e t h e f i e l d c o n t o u r s but t h i s u s u a l l y r e s u l t s i n mixing

t h e t h i n n e r t o p s o i l s wi th t h e roached t r e n c h s p o i l . Subsidence of t h e

t r e n c h l i n e may r e q u i r e h a u l i n g i n of s p o i l o r t o p s o i l . Drainage problems

and d i s r u p t i o n t o normal c u l t i v a t i o n p r a c t i c e s can occur i f t h e mound o r

t h e sunken t rench p e r s i s t s over a number of years . In d ry land farming,

t h e consequences o f mounding and subs idence a r e r e l a t i v e l y minor, but t h e y

a r e c r i t i c a l i n i r r i g a t e d a r e a s where s u r f a c e i r r e g u l a r i t i e s may impede

g r a v i t y f lows o r t h e movement of wheel s p r i n k l e r s . I n i t i a l compaction and

mounding o f t h e t r e n c h l i n e is important and whi le s h o r t t e n l o s s e s t o

p r o d u c t i v i t y can r e s u l t , long term s u c c e s s of rec lamat ion is achieved.

4.33 Cleanup and R e s t o r a t i o n

Cleanup i n c l u d e s llmachine" o r "roughll c leanup and f i n a l c leanup. Rough

c leanup is r i g h t of way r e c o n t o u r i n g and t o p s o i l replacement . F i n a l

c leanup i n c l u d e s c u l t i v a t i o n , rock p i c k i n g , fence r e p a i r s and r e s e e d i n g .

Topsoil replacement is usua l ly done by convent iona l equipment, such a s

dozers a'nd g r ade r s , a s well a s by mormon boards, power dozers and power

augers . Graders , i f a v a i l a b l e , a r e o f t e n used fo r t he f i n a l pa s s s i n c e

they produce t he smoothest and most level s u r f a c e and can r e e s t a b l i s h most

a ccu ra t e1 y t h e o r i g i n a l t o p s o i l depths .

F i n a l c leanup is the l a s t a c t i v i t y of t he p i p e l i n e spread. On c u l t i v a t e d

land, t h e r i g h t of way is c u l t i v a t e d t o r e l i e v e compaction of t o p s o i l and

t o r e s t o r e r i g h t of way appearance. T i l l a g e can be accomplished with con-

vent i o n a l farm implement s, such a s moldboard ploughs, d i s k ploughs and

d i s k harrows. Ch i s e l ploughs may be requ i red t o break up 'severe compac-

t i o n over t h e work and t r a v e l a r ea s . Compacted s u b s o i l should be c u l t i v a -

t ed and l e v e l l e d p r i o r t o t o p s o i l replacement when t h e soil is dry enough

t o s h a t t e r proper ly . "Deep r i pp ing t t may be r equ i r ed fo r compacted s u b s o i l

where t he t o p s o i l is i n place.

4-34 Right o f Way Traff ic

The c o n s t r u c t i o n of a p i p e l i n e i nvo lve s t h e ope ra t i on of much equipment

which must r epea t ed ly t r a v e r s e a narrow path on t h e r i g h t of way. Compac-

t i o n , c r u s t i n g , and r u t t i n g of a g r i c u l t u r a l s o i l s can occur , u sua l l y on

t h e work a r ea and a long the pass ing lane . Turning of c o n s t r u c t i o n vehi-

c l e s on t h e r i g h t of way, p a r t i c u l a r l y a t road c ro s s ings , t i e - i n s and fo r -

e i g n l i n e c r o s s i n g s can a l s o produce mixing of s o i l s .

Rubber t i r e d and t racked veh i c l e s used f o r cons t ruc t i on vary widely i n

t h e i r p o t e n t i a l t o compact a g r i c u l t u r a l s o i l s (Tab le 5.1 ). Ground pres-

s u r e s f o r t racked v e h i c l e s a r e determined by d iv id ing t h e ope ra t i ng weight

by t h e ground con t ac t a rea . Vibra t ion i n c r e a s e s t h e e f f e c t i v e compact i o n

and t h e r e is stress concen t r a t i on around t h e l u g s of t racked veh i c l e s .

Lugged t r a c k s can cause mixing when t u rn ing due t o t h e pene t r a t i on of t h e

l u g s i n t o and, a t times, through t h e t o p s o i l .

Rubber t i r e d v e h i c l e s g e n e r a l l y have g r e a t e r ground p r e s s u r e s than t r a cked

veh i c l e s . Average ground p r e s su re for a t i re is roughly equal t o i n f l a -

t i o n p r e s su re , however because t he load is t r ansmi t t ed through t h e s ide-

- 29 -

wal l s , t h e edges can e x e r t p r e s su re up t o 5 times t h e average. Table 5.1

g ive s ground p r e s s u r e s f o r t y p i c a l p i p e l i n e equipment.

4.41 Conventional Equipment

Bulldozer - T r a c k - t v ~ e Tractors

Bul ldozers and t h e i r a t t achments a r e used fo r a number of jobs on t h e

p i p e l i n e p r o j e c t , p r i m a r i l y f o r r i .ght of way p r epa ra t i on ' and cleanup.

Bul ldozers equipped with r i p p e r s can r i p and move e a r t h i n r i g h t of way

p r epa ra t i on where e x t e n s i v e earthwork is r equ i r ed . Bul ldozers perform

e f f i c i e n t l y i n moving l a r g e volumes of s o i l s h o r t d i s t ance s . During t h e

f i n a l s t a g e s of p i p e l i n e c o n s t r u c t i o n , they a r e used i n rough cleanup f o r

i n i t i a l r i g h t of way recontour ing and f o r moving l a r g e windrows of s p o i l

and t o p s o i l . Bul ldozers can a l s o be used f o r windrowing m a t e r i a l and

b a c k f i l l i n g i f f i t t e d wi th an ang le blade.

Product ion dozers i n t h e D6 - Dl0 range a r e f i t t e d with e i t h e r a univer-

s a l , a s t r a i g h t o r an angled blade. The un ive r s a l b lade has l a r g e wings

which a r e e f f i c i e n t f o r moving b ig loads . The angled blade is s m a l l e r

than t he u n i v e r s a l , e a s i e r to maneuver and is b e t t e r ab l e t o pene t r a t e .

The angled blade can be ad ju s t ed t o 250 t o e i t h e r s i d e f o r use i n windrow-

ing, s i d e c a s t i n g and b a c k f i l l i n g . Since , b lade s p e c i a l i z a t i o n reduces

v e r s a t i l i t y , most c o n t r a c t o r s employ angled blades .

Graders

The motor grader has a wider blade, o p e r a t e s a t a h igher speed, and is

l e s s expensive t o o p e r a t e than a dozer. The grader is used p r ima r i l y

where t h i n l a y e r s of m a t e r i a l have t o be windrowed o r s i d e c a s t , o r f o r

producing a smooth su r f ace . Unlike t h e dozer , t h e v e r t i c a l movement of

t h e b lade is h y d r a u l i c a l l y c o n t r o l l e d from above, a l lowing more a c c u r a t e

depth c o n t r o l , i n t h e o rde r of +2 cm. This p r e c i s e c o n t r o l makes t he - - 30 -

motor grader the p re fe r r ed convent ional machine for t o p s o i l s t r i p p i n g and

f i n a l clean-up.

The lower cos t and high production r a t e s make t h e grader t he p re fe r r ed

machine from the c o n t r a c t o r ' s viewpoint. Where l a r g e r volumes of t opso i l

must be moved, however, the dozer is gene ra l l y used t o move t h e bulk o f

t h e t opso i l . The grader is then used t o " f i n i s h off1' t h e t o p s o i l s t r i p -

ping when s t r i p p i n g approaches t he subso i l .

Trenchers

The s tandard machine used for p i p e l i n e t renching is the wheel t rencher .

I t c u t s a s t r a i g h t , smooth walled t rench with a s l i g h t l y curved bottom

which c r a d l e s the lowered-in pipe. The s i z e of t h e wheel and, t h e r e f o r e ,

t h e s i z e of the t rench w i l l vary with t he s i z e of t h e machine. Most

machines can accommodate a number of wheel s i z e s .

Since wheels a r e expensive t o buy and change, most c o n t r a c t o r s have

t r e n c h e r s with wheels t ha t allow work fo r a wide range of p ro j ec t s . Small

inch c o n t r a c t o r s w i l l run 80 cm t o 90 cm wheels which al lcw them t o work

on p i p e l i n e s up t o 406.4 mm. Big inch c o n t r a c t o r s w i l l have a t l e a s t one

l a r g e t rencher . With smaller t r enche r s , s p o i l can be placed on e i t h e r t h e

work or s p o i l s i d e by changing the d i r e c t i o n of the s p o i l conveyor. On

l a r g e r machines, s p o i l can only be placed on t h e s p o i l s i d e .

The wheel t rencher can be used t o s t r i p t o p s o i l and can do an adequate job

given the r i g h t s o i l and land use condi t ions .

A t p resen t the wheel t rencher is the only machine widely a v a i l a b l e fo r

s t r i p p i n g frozen t o p s o i l ; however, t h e r e a r e l i m i t a t i o n s t o its use. Min-

imum depth of excavation is approximately 25 cm. S t r i p p i n g shal lower

depths c r e a t e s excess ive stress on the machine and l o s s of up t o 50% of

t h e t o p s o i l through s i d e s p i l l from the buckets. P r e s e n t l y t h e r e a r e a

few machinery s u p p l i e r s and c o n t r a c t o r s experimenting with modified con-

vent iona l machinery o r developing new machinery t o handle t o p s o i l i n

frozen condi t ions .

- 31 -

Backhoes

Extensive use of backhoes for t renching through a g r i c u l t u r a l land is not

p re fe r r ed because of increased cos t and increased s u r f a c e dis turbance.

Trench mater ia l excavated by backhoe is usua l ly deposi ted i n l a r g e c lods ,

consequently t h e windrows r equ i r e more s to rage a rea s i n c e the bulking fac-

t o r is g rea t e r . Generally, economics d i c t a t e t h e choice between a backhoe

and a t rencher . Since the t rencher minimizes su r f ace d is turbance and

c o s t s , t he con t r ac to r w i l l use t he t rencher wherever poss ib le .

4.42 Specia l ized Equipment

Power Dozers and Auaer Backf i l l e r s

These machines combine the power of a bul ldozer with t h e a b i l i t y of t h e

motor grader t o s idecas t l a r g e windrows of ma te r i a l i n a s i n g l e pass.

Although o r i g i n a l l y developed for b a c k f i l l i n g and rough cleanup, t h e power

dozer can a l s o be used fo r t o p s o i l s t r i p p i n g . ~ e ~ t h c o n t r o l is s i m i l a r t o

a dozer, t h e r e f o r e its use is bes t s u i t e d t o s t r i p p i n g deep topso i l s .

General ly , these machines a r e more expensive t o ope ra t e than convent ional

equipment.

Stepblades

"Stepblades" have been used for t o p s o i l sa lvage over t h e t r e n c h l i n e i n

pas ture and rangeland.

Typica l ly a narrow one metre wide blade is welded or bo l ted t o t h e bottom

edge of a dozer or grader blade. A narrow width of t o p s o i l is removed and

s i d e cas t by the main blade away from t h e s t r i p p e d area. The add i t i on o f

f l o a t s t o t he ou t s ide of the main b lade allows i t t o be dropped onto t h e

su r f ace without sca lp ing the vegetat ion. A disadvantage of t he s tepblade

is t h e lack of depth cont ro l a s the "step" p ro j ec t ion is assembled t o a

set depth. S e t t i n g d i f f e r e n t depths r equ i r e s reassembling the s t epb lade

onto the main blade. Some prel iminary success has been achieved w i t h t h e

development of an ad jus t ab le s t e p blade t o overcome t h i s problem.

- 32 -

Varia t ions i n t o p s o i l depths can be accomodated by mounting the s tepblade

t o t he s c a r i f i e r mechanism on graders where the s c a r i f i e r is loca ted i n

f r o n t of the main blade. The s tepblade and main blade can be ad jus ted

independently al lowing va r i ab l e depths t o be s t r i pped . An add i t i ona l

advantage is tha t the operator can r ead i ly see the depth being s t r i p p e d , a

disadvantage of t he s t a t i o n a r y s tepblade.

NOVA'S Winter To~soiler

NOVA, An Alberta Corporation has developed a machine which under winter

cond i t i ons , is ab le t o s t r i p a 1 m width of topsoi l to' a con t ro l l ed

depth. The winter t o p s o i l e r is a hydraul ica l ly driven "Roc-Saw Trencher"

mounted on a D9 t r a c t o r . The c u t t e r has been modified t o make i t wider

and s h o r t e r and more s u i t a b l e for t opso i l s t r i p p i n g . A conveyor system

al lows placement of t opso i l i n a windrow beside the t renchl ine . Cutt ing

depths a r e hydrau l i ca l ly c o n t r o l l e d frun the cab on the i n s t r u c t i o n s of a

swamper and can be quickly adjusted. The c u t t i n g s produced by t h e machine

a r e frozen ch ips which can be moved e a s i l y by a dozer o r grader.

The machine has s t r i p p e d up t o 6 km per day, a r a t e g rea t e r than conven-

t i o n a l t renching. Because of its s i z e , i t must be t ranspor ted t o t he job

s i t e on a modified low boy. A s e rv i ce t ruck and welding r i g a r e main-

t a ined on stand-by t o provide immediate r e p a i r se rv ice . The NOVA winter

t o p s o i l e r s t r i p s t o p s o i l with accura te depth con t ro l , but is repor ted t o

be expensive t o operate .

A l o c a l Edmonton con t r ac to r has developed a machine which e f f e c t i v e l y

s e p a r a t e s t opso i l from subso i l under frozen condit ions. The machine is a

modified Barber Greene TA-77 t rencher . The wheel diameter has been

reduced by 30X, the buckets made wider (1.6 m) and more square, and the

d r ive t r a i n has been modified so t h a t the optimum c u t t i n g depth is 15 cm

t o 20 cm.

The design of t h e bucke t s and t h e i n c r e a s e d speed of t h e wheel produces

c o a r s e g r a n u l a r ' s t r i p p i n g s which can be n e a t l y and a c c u r a t e l y p i l e d on t h e

r i g h t of way. Guides mounted on t h e wheel e l i m i n a t e s p i l l o v e r of t o p s o i l ,

a common problem when wheel type machines a r e used t o s t r i p t o p s o i l .

S ince t h e bucket assembly is c o n t r o l l e d by two h y d r a u l i c c y l i n d e r s , i t can

be t i l t e d a few degrees t o t h e l e f t o r r i g h t . Th i s f e a t u r e pe rmi t s good

t o p s o i l recovery where m u l t i p l e , ad jacen t st r i p p i n g passes r e q u i r e one

t r a c k t o be on s t r i p p e d ground and the o t h e r on t h e m d i s t u r b e d s u r f a c e ;

i . e . , one t r a c k lower than t h e o t h e r . This shou ld be p a r t i c u l a r i l y u s e f u l

a t road c r o s s i n g s , bends i n t h e p i p e , t i e - i n s , o r f o r l a r g e diameter p ipe

where a wider s t r i p p e d a r e a is requ i red .

Ditch Witch

An R l O O "Ditch Witch1! has been used f o r p i p e l i n e s up t o 168.3 mm. Th i s

machine can excava te a narrow (30.0 cm) t r e n c h t o a dep th of 1.5 m. The

narrow t r e n c h width reduces t h e o v e r a l l d i s t u r b a n c e and s p o i l q u a n t i t y is

r e l a t i v e l y smal l . The D i t c h Witch is t h e r e f o r e p r e f e r r e d from a s o i l con-

s e r v a t i o n po in t of view, f o r l i n e s 168.3 mm o r l e s s .

The Rotor Ripper

The r o t o r r i p p e r can excava te a narrow t r e n c h (30.0 cm) up t o 2.0 m deep.

The excava t ing wheel is f i t t e d with a s e r i e s of c u t t i n g t e e t h which can

c u t through most s o i l t e x t u r e s , both f rozen and dry. A s with a r e g u l a r

bucket wheel t r e n c h e r , i t s use i n wet s o i l s is l i m i t e d .

The machine's t e e t h p u l v e r i z e t h e s o i l and move it on to t h e m d i s t u r b e d

s u r f a c e on each s i d e of t h e t r ench . The width r e q u i r e d f o r t h e s p o i l p i l e

and the t r e n c h is 2.5 m t o 3.0 m. Th i s is a narrower d i s t u r b a n c e than i f

conven t iona l t r e n c h i n g equipment were used. These smal l s p o i l p i l e s

reduce t h e width of r i g h t o f way r e q u i r e d and a l low t h e c o n t r a c t o r t o use

t h e b l a d e width t o p s o i l s t r i p p i n g procedure on a l l l ands , i n c l u d i n g c u l t i -

va ted , f o r a g e and p a s t u r e land. I n a d d i t i o n , t h e s e p a r a t i o n d i s t a n c e

r e q u i r e d between t h e s p o i l and t o p s o i l is reduced because t h e p i l e s a r e

- 34 -

smaller . This makes b a c k f i l l i n g e a s i e r and minimizes the r i s k of mixing

topsoi l and subsoi l .

The Plough

Another technique which is employed for small p i p e l i n e s up t o 114.3 mm i s

"ploughing" in. . There is no open excavat ion, only some v e r t i c a l displace-

ment during pipe i n s t a l l a t i o n . Ploughing-in minimizes mixing and d i s t u r -

bance, p a r t i c u l a r l y i n sandy s o i l s where i t can be operated most e f f i c -

i e n t l y . As with t h e Ditch Witch and Rotor Ripper, ove ra l l d i s turbance is

normally much l e s s than with a conventional wheel t rencher . One lirnita-

t i on t o ploughing i n is tha t i n some in s t ances , undesireable o r t o x i c sub-

s o i l is brought t o t he sur face , thereby degrading the q u a l i t y of the top-

s o i l .

5.0 PLANNING FOR SOIL CONSERVATION

This chap te r a s s e s s e s soil handl ing p rocedures used i n p i p e l i n e const ruc-

t i o n on a g r i c u l t u r a l l and and e v a l u a t e s t h e i n t e r r e l a t i o n s h i p s of s o i l s

and p i p e l i n e c o n s t r u c t i o n t o determine op t imal s o i l hand l ing p rocedures

f o r s p e c i f i c s o i l c o n d i t i o n s .

Included i n t h i s s e c t i o n is a procedure f o r c a l c u l a t i n g p i p e l i n e r i g h t o f

way width t o a l l o w t h e p roper handl ing and s t o r a g e of s o i l m a t e r i a l s dur-

i n g p i p e l i n e c o n s t r u c t i o n . Many of t h e s o i l problems a s s o c i a t e d wi th

p i p e l i n e c o n s t r u c t i o n , such a s s o i l mixing and l o s s , occur because t h e r e

is i n s u f f i c i e n t r i g h t of way t o p rov ide e f f e c t i v e s t o r a g e and s e p a r a t i o n

o f s o i l m a t e r i a l s .

F i v e major hand l ing p rocedures a r e d i s c u s s e d , a s well a s p rocedures f o r

road and f o r e i g n l i n e c r o s s i n g s , and f o r f r o z e n , wet o r o t h e r s o i l condi-

t i o n s . Although s u b t l e v a r i a t i o n s occur , t h e f i v e p rocedures a r e :

1. No t o p s o i l s t r i p p i n g ,

2 . Trench width t o p s o i l s t r i p p i n g ,

3. Blade width t o p s o i l s t r i p p i n g ,

4. Trench and s p o i l a r e a t o p s o i l s t r i p p i n g , and

5. Trench, s p o i l and work a r e a s t r i p p i n g .

Each of t h e procedures is d i s c u s s e d accord ing t o a p p l i c a t i o n , v a r i a t i o n ,

and implementation. The Appl ica t ion s e c t i o n o u t l i n e s s p e c i f i c p rocedures

based on s o i l q u a l i t y and q u a n t i t y pa ramete rs , l a n d use and weather condi-

t i o n s which shou ld r e s u l t i n t h e l e a s t a g r i c u l t u r a l impact. To dec ide

which procedure w i l l work b e s t , i t is n e c e s s a r y t o c o l l e c t and e v a l u a t e

t h e r e l e v a n t soils, land use and, i f a p p l i c a b l e , c l i m a t i c i n f o r m a t i o n f o r

t h e area .

The V a r i a t i o n s e c t i o n d i s c u s s e s how t h e s t a n d a r d s o i l hand l ing p rocedures

can be modified t o s u i t s p e c i a l s o i l c o n d i t i o n s o r r i g h t of way r e s t r i c -

t i o n s . Topso i l , f o r example, may need t o be s t o r e d i n a s p e c i a l a r e a

because of r i g h t of way r e s t r i c t i o n s o r t o minimize o t h e r impacts.

- 36 -

The Implementation s e c t i o n addresses the type and use of equipment best

s u i t e d to var ious s o i l , land use and weather condi t ions , and s o i l handl ing

procedures. The success of the procedure o f t en depends on how i t is

executed i n the f i e l d .

5 1 CALCULATION CF RIGHT OF WAY WIDTH

Calcula t ing t o p s o i l s t r i p p i n g widths, and s to rage requirements f o r s t r i p p -

ed topso i l and excavated trench s p o i l on the r i g h t of way is required t o

determine tha t s u f f i c i e n t space is ava i l ab l e for proper ma te r i a l s t o r a g e

and for e f f i c i e n t cons t ruc t ion operat ions.

Ca lcu la t ing the width required for s torage of t rench s p o i l and t o p s o i l

s t r i p p i n g r e q u i r e s knowledge of the dimensions of t h e t rench and t h e

method of excavation. (Figure 5.1 1. Average t rench depths w i l l be i n t h e

order of 1.2 m t o 1.5 m and widths 0.7 m t o 1.0 m for small inch l i n e s .

The bulking f a c t o r s for subsoi l a r e assumed t o be 20% f o r wheel t r enche r s

and 30% fo r backhoes. Frozen s p o i l w i l l bulk more i f excavated by

backhoe. The angle of repose for s p o i l is 300 - 38O o r approximately

1.5:l.

The following s t e p s w i l l provide t h e width of t h e r i g h t of way requi red :

1. Determine width of s p o i l p i l e ,

2. Determine width of t opso i l s t r i p p i n g ,

3. Determine width of t opso i l p i l e , and

4. Add width of work and t r a v e l a reas , t rench , and sepa ra t ion d i s t a n c e s

between s p o i l and topso i l p i l e s and between s p o i l p i l e and t rench.

Width o f S~oil Pile

Assuming a uniform s p o i l p i l e* with 1,5:1 s ides lopes (34O) formed by a

wheel t rencher:

Width of s p o i l p i l e base W = &i-

Where A = c ros s - sec t iona l area of s p o i l p i l e (x- t ) yob

x = depth of t r ench

t = depth of t o p s o i l

y = width of t r ench

b = bulking f a c t o r (1.2 f o r t renchers ; 1.3 f o r backhoes)

Example using Figure 5.1.

Cross-sect ional area of s p o i l p i l e A = (x- t ) -yob

= (1.2~1-0.2m) l.Omxl.2m

1.2m2

Width of s p o i l p i l e base

Width o f Topsoil Strippinq

To determine t h e width of t o p s o i l t o be s t r i pped , assuming a t rench and

s p o i l a r ea t o p s o i l s t r i p p i n g procedure (Sect ion 5.24) and r e f e r r i n g t o

F igure 5.1.

One ha l f t he width of t h e t rencher on t h e

work s i d e , so the t rencher w i l l sit l e v e l

during excavation (assuming a Barber-Green TA-77) = .5 x 3.5171 = 1.75rn

One ha l f of the t rench width = .5 x 1.0m = 0.5m

Separat ion of t rench from s p o i l p i l e = 0.5m

Width of s p o i l p i l e = 2.7m

Separat ion of s p o i l p i l e from t o p s o i l p i l e = 1.0m

Total width of t o p s o i l t o be s t r i pped .= 6.45m

* I n p ipe l ine cons t ruc t ion , a uniform s p o i l p i l e is formed only when f ine-grained ma te r i a l is deposi ted from a conveyor be l t . I f formed by a backhoe, dozer, or grader , t he p i l e w i l l be approximately 40 percent wider.

TRACK WIDTH O F

R/w TRENCHER 1 ~ 1 R/W

BDY. BDY.

I I I SPOIL SIDE

'& WORK SlDE I

I I

6.45

- NOTES

1. B A S E D ON TRENCH AND SPOIL AREA T O P S O I L S T R I P P I N G PROCEDURE ( S E C T I O N 5.24.)

2. ASSUMES TOPSOIL I S STRIPPED WITH A BLADE.

5. ASSUMES TRENCH I S EXCAVATED AND S P O I L STORED WITH A WHEEL TRENCHER.

FIGURE 5.1

TYPICAL STRIPPING AND STORAGE REQUIREMENTS

Width o f Topsoil P i l e

Assuming t h a t t h e width of a t o p s o i l p i l e pushed with a dozer is 1.4 times

t h e width of the same p i l e i f depos i ted by conveyor:

Width of t opso i l p i l e base = W = 1 . 4 p

Where A = c ros s - sec t iona l a rea of t o p s o i l p i l e = z . t c b

z = width s t r i p p e d of t o p s o i l

t = depth of t o p s o i l

b = bulking f a c t o r (1.1 for c u l t i v a t e d land; 1.2 fo r p a s t u r e )

Example us ing F igure 5.1.

Cross-sect ional a r ea of t o p s o i l p i l e A = 2 . t - b

= 6.45m x 0.2m x 1.1

= 1.42m2

Width of t o p s o i l p i l e base.

Total Width o f Riqht o f Way

Using F igure 5.1 again.

Spoi l p i l e width = 2.7m

Topsoil p i l e width = 4.lm

Separat ion between s p o i l p i l e and t r ench = 0.5m

Separa t ion between s p o i l p i l e and t o p s o i l p i l e = 1 .Om

Trench width = 1.0m

Work & t r a v e l space (See Sec t ion 4.2) = 10.0m

Total width of r i g h t of way r equ i r ed = 19.3m

5.2 SOIL UINSERVATION PROCEDURES

5.21 No Topsoi l S t r i p p i n g

No topso i l is s t r i p p e d or salvaged on t h e r i g h t of way p r i o r t o t rench

excavation. (Figure 5.2) . Topsoil and subsoi l a r e excavated toget her a s

a s i n g l e l i f t . The replaced s p o i l ma te r i a l , which w i l l form the roo t zone

w i l l be a mixture of any e x i s t i n g t o p s o i l and subso i l .

No topso i l s t r i p p i n g should be considered where:

a ) The t o p s o i l , inc lud ing the sod l a y e r , is less than 5 cm on pas-

t u r e land t h a t is not used i n a crop r o t a t i o n b a s i s for g r a s se s

and c e r e a l crops.

b ) The t o p s o i l is l e s s than 10 cm and the land has a s t o n i n e s s r a t -

i ng g r e a t e r than or equal t o S3 on pas tu re land.

c ) The s o i l is poorly dra ined , is sub jec t t o prolonged per iods o f

high water t a b l e and has not been r ecen t ly c u l t i v a t e d .

Var ia t ion

Trench s p o i l is usua l ly s t o r e d on t h e s p o i l s i d e of t h e t rench , however,

i n poorly drained a r ea s i t may be advantageous t o s t o r e it on the work

s i d e fo r use dur ing pipe makeup.

Implementation

A wheel t rencher is p r e f e r r e d for excavat ion s i n c e t he pu lver ized s p o i l

can be back f i l l ed without c r e a t i n g an excessive roach. In s tony or poorly

drained a r ea s , a backhoe is usua l ly used. Compaction of t h e b a c k f i l l

ma te r i a l is recommended immedi a t e 1 y following s p o i l replacement t o reduce

t he height of the roach and t o not impede s u r f a c e drainage.

R/W BOY. SPOIL S l D E

I I EXCAVATED

WORK S l D E R / W BDY.

I I

UNDISTURBED TOPSOIL

PROF1 LE N.T.S.

NOTES

I 1- EXCAVATE T O P S O I L AND S U B S O I L AS A S I N G L E L I F T PLACE TRENCH S P O I L ON S P O I L S I D E ADJACENT TO TRENCH-

I 2 * RETURN TRENCH S P O I L TO TRENCH AND COMPACT* M I N I M I Z E S C A L P I N G OF U N D I S T U R B E D SOD LAYER I N GRASSED L A N D S * L E A V E A ROACH OVER T H E TRENCH TO ALLOW FOR S U B S I D E N C E .

I 3. RESEED W I T H A C O M P A T I B L E SEED M I X AND F E R T I L I Z E *

FIGURE 5.2

NO TOPSOIL STRIPPING

AUG, 1984

5.22 Trench Width Topso i l S t r i p p i n g

Trench width t o p s o i l s t r i p p i n g i n v o l v e s t h e s t r i p p i n g and s a l v a g e of a 0.8

t o 1.2 m width of t o p s o i l over t h e t r e n c h l i n e ( F i g u r e 5.3). The purpose

of t h i s procedure is t o i n c u r t h e l e a s t d i s t u r b a n c e and c o s t . Compaction

o f t h e s u b s o i l is kept t o a minimum s i n c e t o p s o i l is undis tu rbed on t h e

s p o i l and work s i d e s . S p o i l can be s t o r e d on und is tu rbed t o p s o i l and

r e t u r n e d t o t h e t r e n c h wi thou t i n c o r p o r a t i n g a h igh p e r c e n t a g e of undis-

tu rbed t o p s o i l . I n a t y p i c a l s i t u a t i o n , b a c k f i l l m a t e r i a l w i l l u s u a l l y

no t overf low t h e t r ench . A s u f f i c i e n t volume of t o p s o i l w i l l have been

sa lvaged t o r e p l a c e t h e o r i g i n a l depth o f t o p s o i l s t r i p p e d over t h e

t r e n c h l i n e .

The maximum width s t r i p p e d should not exceed t h e i n s i d e t r e a d t o t r e a d

dimensions of t h e t r e n c h e r . For an average s i z e t r e n c h e r (Barber Greene

TA-65) t h i s dimension is approximately 1.8 m. In s o f t m a t e r i a l s t h e

s t r i p p e d width shou ld be approx imate ly 1.3 rn t o prevent t h e t r a c k s from

c o l l a p s i n g t o p s o i l i n t o t h e excava t ion .

S t r i p p e d t o p s o i l is s t o r e d on t h e work s i d e approx imate ly 1.3 m from t h e

edge of t h e t r e n c h . The t r e n c h is excavated and t h e s p o i l is s t o r e d on

u n d i s t u r b e d t o p s o i l on t h e s p o i l s i d e and a d j a c e n t t o t h e t r ench .

A p p l i c a t i o n

Trench width t o p s o i l s t r i p p i n g i s b e s t s u i t e d where s p o i l can be s t o r e d on

u n d i s t u r b e d t o p s o i l and s e p a r a t e d wi thou t s i g n i f i c a n t mixing, and where

rep laced s p o i l can be c o n f i n e d t o t h e t r e n c h . The s o i l and l and use

s i t u a t i o n s where t h i s procedure is b e s t s u i t e d inc lude :

a ) S o i l s where:

- t o p s o i l d e p t h s exceed 40 cm

- dry c o n d i t i o n s e x i s t f o r most o f t h e year

i t WIDTH OF TOPSOIL STRIPPING

R/W BOY. SPOIL SlDE

Q TRENCH I I I I

EXCAVATED @nn'L I STRIPPED

WORK SlDE R/ W BOY.

I I I I

EXCAVATED STRIPPED

1 I

NOTES

1- REMOVE T o P s o r L FROM THE TRENCH LINE AND S T O R E ON WORK SIDE ADJACENT TO THE TRENCH S T R I P P E D W I D T H WILL BE A P P R O X I M A T E L Y 0.8-1 - 2 M. S T O R E D T O P S O I L SHOULD BE APPROXIMATELY 1.3 M FROM THE TRENCH TO ALLOW FOR SUBSEQUENT P A S S OF TRENCHER TO E X C A V A T E S U B S O I L M A T E R I A L .

2. E X C A V A T E S U B S O I L AND STORE ON S P O I L S I D E A D J A C E N T TO T H E T R E N C H *

3. RETURN TRENCH SPOIL TO TRENCH AND COMPACT. MINIMIZE SCALPING OF UNDISTURBED SOD L A Y E R ON GRASSED L A N D S -

4. RETURN T O P S O I L E V E N L Y OVER THE TRENCH L I N E .

5. A L L E V I A T E C O M P A C T I O N OF T O P S O I L OVER E N T I R E R I G H T OF WAY ON C U L T I V A T E D L A N D S * R E S E E D W I T H A C O M P A T I B L E S E E D M I X AND F E R T I L I Z E ON G R A S S E D L A N D S -

FIGURE 5.3

TRENCH WIDTH TOPSOIL STRIPPING

AUG. ,1984

In such cases , replaced s p o i l can be confined t o t he t rench and min-

or amounts of t opso i l can be mixed with s u b s o i l without apprec iab ly

a l t e r i n g topso i l capab i l i t y . S u f f i c i e n t volumes of salvaged t o p s o i l

w i l l be a v a i l a b l e t o r e s t o r e t o p s o i l depth over t he t rench.

b) S o i l s where:

- t o p s o i l depths exceed 30 cm

- subso i l q u a l i t i e s a r e good t o f a i r

- t h e land is i n forage crop

Under these circumstances, replaced s p o i l can usua l ly .be confined t o

t h e t rench and s u f f i c i e n t volumes of t o p s o i l a r e a v a i l a b l e t o

r e s t o r e t opso i l depths over t h e trench. Separa t ion of s p o i l during

replacement is aided by the e s t ab l i shed roo t mat of t he forage crop,

t h e r e f o r e , l i t t l e t o p s o i l w i l l be incorporated w i t h t h e s p o i l and

l o s t i n the t rench.

c ) S o i l s where:

- t o p s o i l depths exceed 20 cm

- subso i l q u a l i t i e s a r e good t o f a i r

- t h e land is i n e s t ab l i shed pas ture

Given t h i s c r i t e r i a , replaced s p o i l w i l l completely f i l l t h e t rench

or over flow it only s l i g h t l y . Adequate volumes of t o p s o i l and sod

should be a v a i l a b l e for reclamation over t h e t rench and because of

the e s t ab l i shed root mat, s p o i l can be e a s i l y separa ted without dis-

tu rb ing the underlying topso i l .

d) S o i l s where:

- t o p s o i l depths exceed 20 cm

- frozen condi t ions p reva i l

- subso i l q u a l i t i e s a r e good t o f a i r

Generally, rep laced s p o i l w i l l completely f i l l t h e t rench o r over-

flow i t s l i g h t l y and topso i l can be adequately separa ted from sub-

s o i l i n t hese circumstances.

- 46 -

Spo i l can usua l ly be separa ted from the f rozen t o p s o i l su r f ace with-

out d i s t u r b i n g the t o p s o i l , a l s o adequate volumes of t o p s o i l w i l l be

a v a i l a b l e t o r ep l ace t h e o r i g i n a l depth. I f subso i l q u a l i t i e s a r e

poor t o unsu i tab le , t o p s o i l depths should exceed 30 cm so t h a t top-

s o i l can be understr ipped and yet be i n s u f f i c i e n t quan t i t y fo r

replacement

e ) S o i l s where:

- t o p s o i l depths a r e l e s s than 15 cm

- the p r o b a b i l i t y of s o i l e ros ion by wind is high

- t h e land is i n forage , pas ture o r s t u b b l e

S o i l s i n t h i s type of environment a r e u sua l ly coarse tex tured and

dry. Reducing the r i s k of wind e ros ion by minimizing d is turbance t o

t h e vege t a t i ve cover, should be weighed aga ins t the r i s k of mixing.

Variation

Topsoil i.s usua l ly s t r i p p e d t o t he El horizon. In s o i l s with good q u a l i t y

I3 mate r i a l and poor q u a l i t y C ma te r i a l , s t r i p p i n g can inco rpo ra t e some I3

horizon i n t o the organic A mate r i a l t o i nc rease t he volume of t o p s o i l and

t o ensure t h a t t h e r e is room i n t he t rench f o r a l l of the poorer q u a l i t y C

ma te r i a l . This v a r i a t i o n is app l i cab l e t o s o i l s with t o p s o i l depths o f 20

t o 30 cm. In frozen condi t ions t h i s v a r i a t i o n a p p l i e s t o a l l s o i l s with

t o p s o i l depths o f 10 t o 30 cm.

Implementation

Trench width t o p s o i l s t r i p p i n g can be performed with e i t h e r a bucket wheel

t r enche r o r a s t e p blade. A s t e p blade is usua l ly used where t o p s o i l

depths a r e l e s s t han 20 cm. The s t e p blade w i l l s t r i p t he t o p s o i l and

move i t onto t he undis turbed t o p s o i l su r f ace ad jacent t o t he t rench. The

main blade w i l l l a t e r a l l y d i sp l ace t h i s ma te r i a l away from the t rench t o

a l low the t r enche r t o follow. To avoid l o s s of t o p s o i l during l a t e r a l

t r a n s p o r t a t i o n , t h e undis turbed su r f ace should be frozen o r covered with

an e s t a b l i s h e d vege t a t i ve mat.

- 47 -

The bucket wheel t r e n c h e r is more e f f e c t i v e when s a l v a g i n g t o p s o i l s deeper

than 20 cm. Topso i l w i l l s p i l l o f f t h e bucke t s d u r i n g excava t ion and end

up a s smal l p i l e s on both s i d e s of the t r e n c h . The remainder of t h e top-

s o i l w i l l be c a r r i e d by t h e bucke t s , dumped on t h e conveyor and d e p o s i t e d

away from t h e t r e n c h on t h e work s i d e . With s h a l l o w dep ths , less than

20 cm, t h e sa lvaged volume of t o p s o i l w i l l be s i m i l a r t o t h a t s p i l l e d from

t h e buckets. S p i l l can be reduced o r avoided by mounting a smal l llshoe"

or guide on each s i d e of t h e wheel t o push t h e t o p s o i l back i n t o t h e

t r e n c h f o r e x c a v a t i o n by subsequent buckets .

When r e p l a c i n g s p o i l , c a r e shou ld be taken t o e n s u r e t h e s p d i l is r e t u r n e d

t o t h e t r e n c h and not e x c e s s i v e l y roached over t h e t r e n c h o r al lowed t o

overf low t h e t r e n c h on t o u n d i s t u r b e d t o p s o i l . T h i s is p a r t i c u l a r i l y

important when working with sha l low t o p s o i l s t o avoid gouging and i n c o r -

p o r a t i o n of s p o i l i n t o t o p s o i l dur ing subsequent c u l t i v a t i o n by t h e land-

owner. This can be avoided by s u c c e s s i v e l y "shading inv1 p o r t i o n s of t h e

s p o i l and compacting, r a t h e r than r e t u r n i n g a l l t h e s p o i l i n one p a s s and

then compacting. The compactive e f f o r t of one p a s s o f a dozer o r g r a d e r

is u s u a l l y not enough . to p r o p e r l y compact a metre of s p o i l . However, a

grader t ire does compact b e t t e r than a dozer t r a c k .

Shallow t o p s o i l shou ld be r e p l a c e d with a grader because of i ts g r e a t e r

accuracy i n hand l ing smal l volumes of m a t e r i a l s . On p a s t u r e l a n d s where

s c a l p i n g of t h e sod l a y e r must be avoided, t h e g rader h a s t h e p r e c i s i o n t o

do t h e job p roper ly .

I n f rozen c o n d i t i o n s t o p s o i l shou ld not be r e p l a c e d u n t i l t h e t r e n c h s p o i l

has thawed, subs ided and has been mechan ica l ly compacted and con toured .

5.23 Blade Width Topsoil Stripping

Topsoil is s t r i pped and salvaged over a t h ree t o four metre s t r i p cen t r ed

over the t r ench l ine (Figure 5.4). This procedure produces t h e l e a s t mix-

i ng of t o p s o i l and subso i l by accommodating t h e b a c k f i l l and replacement

o f trench s p o i l without a f f e c t i n g adjacent undisturbed t o p s o i l . Trench

s p o i l w i l l bulk when excavated and with the pipe i n place, w i l l occupy a

g rea t e r volume than is ava i l ab l e i n the trench. By removing a blade width

of t opso i l , the excavated s p o i l can be replaced and allowed t o overflow

t h e trench. Overflow s p o i l can be fea thered over t h e blade width, rework-

ed and recontoured without s e r i o u s l y a f f e c t i n g e i t h e r t h e s t r i p p e d o r

undisturbed topso i l . S t r ipped topso i l is then replaced over t h e o r i g i n a l

s t r i pped area.

The width s t r i p p e d w i l l vary according t o the type and angle of t he b lade

used. Both graders and dozers a r e used. The minimum width s t r i pped

should accommodate the ou t s ide t r ead to t r ead dimensions of t h e t rencher .

For an average s i z e t rencher (Barber Greene TA-65) t h i s dimension is 3 m.

An add i t i ona l 0.5 m should be allowed, making t h e s t r i p p e d width. 3.5 m.

Larger t r enche r s w i l l r equ i r e add i t i ona l width.

S t r ipped t o p s o i l is s to red on the work s i d e immediately ad jacent t o t he

s t r i pped area. The t rench is excavated and the s p o i l s t o r e d on t h e s p o i l

s i d e p a r t i a l l y on subso i l and undisturbed topso i l .

Application.

Blade width topso i l s t r i p p i n g is best s u i t e d where t rench s p o i l can be

s to red on and separated from undisturbed t o p s o i l without r i s k of mixing,

and where the replaced t rench s p o i l cannot be completely confined t o t h e

o r i g i n a l t rench and must be l a t e r a l l y fea thered t o avoid high roaching.

The s o i l and land use s i t u a t i o n s where t h i s procedure is bes t s u i t e d

include:

a ) S o i l s where:

- the land is i n e s t ab l i shed forage c rops

- 50 -

WIDTH OF TOPSOIL STRIPPING k

WORK SIDE R / W BOY.

EXCAVATED I

STRIPPED

NOTES

1. REMOVE T O P S O I L FROM AN AREA CENTRED OVER THE TRENCH L I N E . S T R I P P E D W I D T H W I L L B E A P P R O X I M A T E L Y 3 T O 3.5 M a STORE T O P S O I L ON WORK S I D E A D J A C E N T TO S T R I P P E D AREA. T O P S O I L CAN B E S T O R E D I N A P I L E OR S P R E A D OUT OVER THE WORK S I D E .

2. E X C A V A T E TRENCH S U B S O I L AND STORE ON S P O I L S I D E A D J A C E N T TO T R E N C H *

3 . R E T U R N TRENCH S P O I L TO TRENCH A N D C O M P A C T - F E A T H E R OUT E X C E S S S P O I L OVER S T H I P P E D AREA L E A V I N G A LOW ROACH C E N T N E U O V E N T H E T R E N C H -

4. R E T U R N T O P S O I L E V E N L Y OVEN THE S T R I P P E D A R E A -

5 . A L L E V I A T E C O M P A C T I O N OF T O P S O I L OVER 6 N T I R E R I G H T OF WAY ON C U L T I V A T E D L A N D S * R E S E E D WITH A COMPATIBLE SEED MIX AND FERTILIZE ON GRASSED LANDS.

FIGURE 5.4

BLADE WIDTH TOPSOIL STRIPPING

AUG., 1984

- t o p s o i l is less than 30 cm

- subso i l q u a l i t i e s a r e good to f a i r

Es tab l i shed vegeta t ion cover allows subso i l t o be p a r t i a l l y placed

on the undisturbed t o p s o i l and e a s i l y separa ted during replacement.

Shallow t o p s o i l depths of l e s s than 30 cm may not allow replacement

o f a l l t he s p o i l i n t h e t rench, t h e r e f o r e , excess s p o i l must be dis-

placed over s u b s o i l t o avoid impacting undisturbed topso i l . Mixing

o f t opso i l and subso i l w i l l occur during post cons t ruc t ion a c t i v i -

ties i f the excess s p o i l is not l a t e r a l l y d isp laced t o reduce t h e

roach he ight .

b) S o i l s where:

- the land is improved pas tu re

- t o p s o i l depth is less than 20 cm

A s with a ) above, s p o i l can be placed p a r t i a l l y on t h e undisturbed

t o p s o i l s u r f a c e because of t he e x i s t i n g vegeta t ion mat. With sha l -

low t o p s o i l depths, replaced s p o i l w i l l overflow t h e t rench and

a f f e c t the undisturbed t o p s o i l , forming a high roach i f not l a t e r -

a l l y d isp laced on the subso i l sur face . Mixing t o p s o i l and subso i l

is a major concern.

c ) S o i l s where:

- a t o p s o i l depth of 30 t o 40 cm e x i s t s

- the land is c u l t i v a t e d

- s u b s o i l q u a l i t i e s a r e good t o f a i r

Trench s p o i l , when rep laced , w i l l l i k e l y exceed t h e o r i g i n a l t rench

volume and must be l a t e r a l l y d isp laced . Because of t he l a r g e vol-

umes of t o p s o i l , ma te r i a l s to rage w i l l be a problem i f t h e s p o i l

s t o r a g e a rea is completely s t r i pped . Replacement of s p o i l dur ing

b a c k f i l l can cause some l o s s of undisturbed t o p s o i l , but its conse-

quences t o s o i l c a p a b i l i t y a r e not major due t o t h e l a r g e amounts o f

a v a i l a b l e t o p s o i l .

d ) S o i l s h e r e :

- t o p s o i l dep ths a r e between 10 and 20 cm

- f rozen condi t ions exist

- subso i l q u a l i t i e s a r e good t o f a i r

In t h i s i n s t ance , t o p s o i l can be adequately separa ted from s u b s o i l .

However, f rozen s p o i l w i l l be d i f f i c u l t t o handle and may not be

e f f e c t i v e l y rep laced i n t h e t rench u n t i l thawed. Replaced s p o i l

w i l l overflow t h e t rench and should be allowed t o thaw before i t is

reworked with a blade.

e ) S o i l s where:

- t o p s o i l depth is between 10 and 30 cm

- frozen cond i t i ons exist

- s u b s o i l q u a l i t i e s a r e poor t o unsu i t ab l e

The same cond i t i ons i n d) above w i l l apply. Even with 30 cm of top-

s o i l , the rep laced frozen s p o i l w i l l completely f i l l t h e t rench .

Because of t he poor q u a l i t y ' subso i l , s p o i l must be confined t o a

pos i t i on below t h e t o p s o i l t o avoid major impacts t o undis turbed a s

wel l a s replaced t o p s o i l .

This procedure can a l s o be app l i ed where t renching equipment d e p o s i t s

s p o i l on both s i d e s of t h e t r ench ; for example, t h e "Ditch Witch" and some

narrow wheel t renchers . The o u t s i d e dimensions of the s p o i l p i l e s adja-

cent t o t he t rench w i l l be 2.5 m t o 3.0 m. With t he b lade width t o p s o i l

s t r i p p i n g procedure, excavated t rench s p o i l rests on undis turbed subso i l .

This s t r i p p i n g procedure, i n conjunct ion with narrow t renching equipment,

can be used for s o i l s on c u l t i v a t e d , forage and improved pas tu re land. I n

these s i t u a t i o n s , s p o i l is not s t o r e d on t o p s o i l and the r i s k of mixing

during b a c k f i l l i n g is decreased.

Variations

It is p re fe rab l e t o s t o r e t he s t r i p p e d t o p s o i l on t he work s i d e ad jacent

t o t he s t r i p p e d area. (Figure 5.4). Topsoil may be spread out over t he

- 53 -

work s i d e t o reduce subso i l compaction and r u t t i n g of t h i n t o p s o i l s o r i f

t he t o p s o i l p i l e becomes an o b s t a c l e t o t h e c o n s t r u c t i o n crew.

In some cases , p l ac ing t o p s o i l on t h e s p o i l s i d e between t h e s p o i l p i l e

and the r i g h t of way boundary can be done a s a l a s t r e s o r t . General ly ,

t h i s is not d e s i r e d due t o t o p s o i l l o s s from movement back and f o r t h

ac ros s the vegetat ion mat. In add i t i on , damage t o t h e vege ta t ion mat may

occur during t h e process of recovering t h e t o p s o i l .

Implementation

Topsoil is s t r i p p e d by e i t h e r a dozer o r grader . Due t o t he r i s k of mix-

ing , r ipping i n f rozen condi t ions p r i o r t o s t r i p p i n g is not recommended.

S t r i pp ing should be t o a uniform depth t o ensure t h a t a l l of t he t o p s o i l

is removed p r i o r t o t renching and b a c k f i l l i n g . This a l s o al lows t h e

t rencher t o sit l e v e l t o avoid excessive equipment s t r a i n .

A grader is recommended, because of its b e t t e r depth c o n t r o l , f o r

Solone tz ic soils which exh ib i t poor t o m s u i t a b l e phys ica l and chemical

subso i l q u a l i t i e s and fo r s o i l s with less than 15 cm of t opso i l . Mixing

with subso i l can be a major problem i f t o p s o i l is not a c c u r a t e l y sepa-

r a t ed , p a r t i c u l a r i l y i n Solone tz ic s o i l s . S o i l s with t o p s o i l dep ths

g r e a t e r than 15 cm may be succes s fu l ly s t r i p p e d by dozer.

I f frozen, replaced s p o i l must thaw before f i n a l compaction and d e f i n i t e l y

before t opso i l replacement. Topsoil can be l o s t i f i t is rep laced p r i o r

t o t rench se t t l ement . I f cons t ruc t ing i n w in t e r , t h e t rench should be

llroughed i n " with s p o i l t o pro tec t t he pipe a d t h e t o p s o i l rep laced t h e

following spr ing . Trench mater ia l excavated with a t r enche r p u l v e r i z e s

b e t t e r and can be more e a s i l y compacted than ma te r i a l dug up with a back-

hoe.

5.24 Trench and Spoil Area Topsoil Stripping

This procedure provides a s t r i p p e d width wide enough t o accommodate the

trencher, the s p o i l and a one metre separat ion between the s p o i l p i l e and

topso i l . (F igure 5.5). Mix ing i s avoided s ince t o p s o i l i s s tored on top-

s o i l and s p o i l i s s to red on subsoi l . Movement o f the s p o i l should not

a f f e c t any t o p s o i l . Replaced s p o i l should be compacted i n the trench,

reworked w i th a blade and feathered over the s t r i pped area p r i o r t o top-

s o i l replacement.

Str ipped widths are t y p i c a l l y 6 t o 8 m, depending on the s i z e o f trencher,

the w i d t h o f trench and the amount o f spoi.1 generated. Str ipped t o p s o i l

i s usua l ly s to red on the s p o i l s i d e adjacent to the r i g h t o f way bound-

ary. The t rench s p o i l i s placed on a subso i l sur face near the trench and

one metre from the t o p s o i l p i l e o r one metre from the undisturbed topso i l ,

whichever i s nearer.

Application

Trench and s p o i l area t o p s o i l s t r i p p i n g i s the most widely used proce-

dure f o r p i p e l i n e cons t ruc t i on on a g r i c u l t u r a l lands. I t i s p r a c t i c a l

where t rench s p o i l cannot be s tored on t o p s o i l without mix ing dur ing back-

f i l l operations. The s o i l and land use s i t u a t i o n s where t h i s procedure i s

best s u i t e d inc lude:

a) S o i l s where:

- t o p s o i l depths range from 10 t o 30 cm

- the land i s c u l t i v a t e d

- s u b s o i l q u a l i t i e s are good t o f a i r

Because of the moderate t o p s o i l depths and the "loose" nature o f the

topso i l , s p o i l cannot be s tored on i t wi thout s i g n i f i c a n t mixing.

b) S o i l s where:

- t o p s o i l depths are l ess than 30 cm

- the land i s i n forage crop

- 56 -

WIDTH OF TOPSOIL STRIPPING G R'W SPOIL SlDE BDY.

I Q TRENCH I

WORK SlDE

I STRIPPED I

PROFILE N.T. S.

NOTES . .

1. REMOVE T O P S O I L FROM OVER THE TRENCH AND UNDER THE S P O I L P I L E - S T R I P P E D W I D T H WILL BE APPROXIMATELY 6-8 M. S T O R E TOPSOIL ON SPOIL SIDE ADJACENT TO STRIPPED AREA.

2. E X C A V A T E TRENCH S U B S O I L AND STORE ON S P O I L S I D E A D J A C E N T TO TRENCH. ALLOW A 1 M S E P A R A T I O N BETWEEN THE T O P S O I L P I L E AND THE TRENCH S P O I L *

3. RETURN TRENCH S P O I L TO TRENCH AND COMPACT- F E A T H E R OUT EXCESS S P O I L OVER S T R I P P E D AREA L E A V I N G A LOW ROACH CENTRED OVER THE T R E N C H - A L L E V I A T E C O M P A C T I O N OF C L A Y R I C H S U B S O I L S OVER THE S T R I P P E D A R E A -

4. RETURN T O P S O I L E V E N L Y OVER THE S T R I P P E D AREA.

5 - A L L E V I A T E C O M P A C T I O N OF T O P S O I L OVER E N T I R E R I G H T OF N A Y -

FIGURE 5.5

TRENCH AND SPOIL AREA TOPSOIL STRIPPING

AUG. , 1 9 8 4

- s u b s o i l q u a l i t y is poor t o unsu i t ab l e

The poor q u a l i t y s p o i l should not be i n contac t with e i t h e r s t o r e d

o r undis turbed t o p s o i l because of its p o t e n t i a l t o a l t e r t o p s o i l

qua l i t y .

Variation

To prevent mixing, t o p s o i l is usua l ly s t r i p p e d only t o t h e B horizon. For

c u l t i v a t e d f i e l d s with poor or unsu i t ab l e B horizons, t he t o p s o i l should

be understr ipped so t h a t poorer q u a l i t y B mate r i a l is not mixed with t h e

s t r i p p e d t o p s o i l . This is f a i r l y e a s i l y done i f t h e r e is a colour d i f f e r -

ence between the t o p s o i l and B horizons. Where a co lour change is not

ev ident , i t is important t o con t ro l s t r i p p i n g t o a predetermined depth

j u s t above the B horizon.

Where the s u b s o i l is f i n e t ex tu red and the moisture conten t is favourable

f o r compaction, t he s t r i p p e d t o p s o i l may be spread on t h e work s i d e of the

r i g h t of way. The i n c r e a s e i n t he t o p s o i l depth w i l l decrease the compac-

t i o n t o the subso i l . Compacted s u b s o i l i n t h e s t r i p p e d a r e a can be

"worked up" p r i o r t o t o p s o i l replacement.

Implementation

Topsoil can be s t r i p p e d with e i t h e r a dozer o r a grader . The grader is

p re fe r r ed i n a r e a s of t h i n t o p s o i l and on soils with poorer q u a l i t y sub-

s o i l where depth c o n t r o l is c r i t i c a l . With r e l a t i v e l y deep t o p s o i l

(> I5 cm), a dozer can be used t o remove the bulk of t he mater ia l . A

grader should then be used t o s e p a r a t e t he remaining t o p s o i l f r an t h e B

horizon.

A t rencher is p re fe r r ed for t rench excavat ion s i n c e t h e ma te r i a l can be

deposi ted accu ra t e ly on the r i g h t of way, a l lowing cons tan t s epa ra t i on o f

s p o i l and t o p s o i l .

J I n i t i a l b a c k f i l l i n g can be done by e i t h e r dozer or mormon board, although

the l a t t e r performs t h i s t a sk bes t . F ina l b a c k f i l l i n g is f in i shed o f f

, - with a grader t o r e s t o r e t h e o r i g i n a l s u b s o i l grade. The s p o i l p i l e

t should be shaded i n t o t h e t rench i n por t ions and each por t ion of t he s p o i l

d compacted a s i t is replaced. This w i l l a s s i s t i n r e tu rn ing t h e s p o i l t o the t rench without major overflow.

d

Subsoi l compaction i n t he s t r i p p e d a r ea should be c u l t i v a t e d p r i o r t o top-

s o i l replacement. 4

5.25 Trench, Spoil and Work Area Topsoil Stripping

The primary purpose of t rench , s p o i l and work a r e a t o p s o i l s t r i p p i n g

(Figure 5.6) is to reduce mixing and compaction of s o i l s . S torage of

s p o i l and movement of equipment occurs on s u b s o i l and away f ran t h e top-

s o i l p i l e s and undis turbed topso i l . Mixing is minimized s i n c e t o p s o i l is

not f u r t h e r d i s t u r b e d during ac tua l p i p e l i n e cons t ruc t ion . While compac-

t i o n may occur on t h e work s i d e and on t h e s p o i l s t o r a g e a r ea , i t w i l l be

confined to t h e s u b s o i l and can be a l l e v i a t e d through c u l t i v a t i o n p r io r t o

t o p s o i l replacement. Rut t ing and mixing of t h i n t o p s o i l s by r i g h t of way

t r a f f i c w i l l not occur s i n c e the t o p s o i l has been removed.

The only par t of t he r i g h t of way not s t r i p p e d is t h a t requi red for top-

s o i l s to rage . S t r i p p e d widths w i l l vary from 12 t o 25 m depending on t h e

depth of t o p s o i l , t he s i z e of t he r i g h t of way and e x t r a working space

required.

S t r i pped t o p s o i l is s t o r e d e i t h e r on one or both s i d e s of t h e r i g h t of

way, Trench s p o i l is s t o r e d on s u b s o i l , s e p a r a t e from the t o p s o i l p i l e .

Construct ion equipment t r a v e l on t h e graded s u b s o i l su r f ace . Care should

be taken not t o d i s t u r b o r compact the s t o r e d t o p s o i l by r i g h t of way

t r a f f i c ; nor should t o p s o i l be used t o l e v e l low o r wet areas .

Application

Trench, s p o i l and work a r ea t o p s o i l s t r i p p i n g is s u i t e d where t h e r e is a

high p o t e n t i a l for t o p s o i l r u t t i n g or compaction of subso i l on t h e work

s i d e , The s o i l and land use where t h i s procedure is app l i cab l e inc ludes :

a ) S o i l s where:

- t o p s o i l depths a r e less than 10 cm

- s u b s o i l q u a l i t i e s a r e good t o f a i r

- t h e land is under c u l t i v a t i o n

- parent m a t e r i a l s a r e f i n e t ex tu red , such a s l a c u s t r i n e c l a y s

WIDTH OF TOPSOIL STRIPPING - w

R/W BOY. SPOIL SIDE

I TRENCH

I WORK SIDE R/W

BDY. I

I STRIPPED I

TOPSOIL

PROFILE N.T. S.

NOTES

1- REMOVE T O P S O I L FROM THE TRENCH, S P O I L STORAGE AlJD WORK A R E A S . STORE T O P S O I L Old B O T H S I D E S OF THE R I G H T OF WAY A D J A C E N T TO THE S T R I P P E D A R E A .

2. E X C A V A T E TRENCH S U B S O I L AND STORE ON S P O I L S I D E A D J A C E N T TO T t i E TRENCH. A L L O W FOR A 1 M S E P A H A T I O r J B E T N E E N THE T O P S O I L P I L E ANL) THE THENCH S P O I L -

3- R E T U R N TRENCH S P O I L TO TRENCH AND COMPACT. F E A T H E R OUT E X C E S S S P O I L OVER S T R I P P E D AREA L E A V I N G A LOW ROACH C E N T R E D OVER THE TRENCH. A L L E V I A T E C O M P A C T I O N OF C L A Y R I C H S U B S O I L S OVER THE S T R I P P E U A R E A -

4. R E T U R N T O P S O I L E V E N L Y OVER THE S T R I P P E D A R E A -

5. A L L E V I A T E C O M P A C T I O N OF T O P S O I L OVER E N T I R E R I G H T OF WAY-

F I G U R E 5.6

TRENCH , SPOIL , AND WORK AREA TOPSOIL STRIPPING

I AUG., 1984 1

The r i s k of r u t t i n g t h i n t o p s o i l s is e l imina ted by its removal

from t h e work s i d e . With t h i n t o p s o i l s developed on l a c u s t r i n e

c l a y s , compaction of t h e B horizon would probably occur even i f

t o p s o i l is not s t r i p p e d . Removing t h e t o p s o i l p r i o r t o

cons t ruc t ion permits reworking of t h e s u b s o i l t o a l l e v i a t e

compaction.

b) S o i l s where:

- t h e land is p re sen t ly under c u l t i v a t i o n or i n r e c e n t l y es tab-

l i s h e d forage

- t o p s o i l depth is less than 20 cm

- wet weather may p r e v a i l throughout c o n s t r u c t ion.

Topsoil is removed from t h e work s i d e p r i o r t o cons t ruc t ion t o avoid

r u t t i n g and mixing during wet weather. Rut t ing and subso i l compac-

t i on can be remedied p r i o r t o t o p s o i l replacement.

Variation

Preference is t o s t o r e t he s t r i p p e d t o p s o i l on both s i d e s of t he r i g h t o f

way a s i l l u s t r a t e d i n Figure 5.6. This reduces t h e d i s t a n c e t o p s o i l must

be moved t o and from the s t o r a g e a r ea s . The p i l e s a l s o ac t a s a con-

s t r a i n t t o off r i g h t of way t r a f f i c . I f necessary, t o p s o i l can a l s o be

s t o r e d on only one s i d e of t he r i g h t of way.

With t h i n t o p s o i l s ( l e s s t han 10 cm) or with poor t o unsu i t ab l e s u b s o i l s ,

depth cont ro l is c r i t i c a l ; t h e r e f o r e , a grader is t h e p r e f e r r e d s t r i p p i n g

equipment. Where t he t o p s o i l is g r e a t e r t han 10 cm a dozer can be used t o

remove the bulk of t he t o p s o i l . A g rader should then be used t o s e p a r a t e

t he remaining t o p s o i l from t h e B horizon, e s p e c i a l l y i f t h e s u b s o i l qual-

i t y is poor t o unsu i tab le .

During replacement of t h i n t o p s o i l s , a grader is p re fe r r ed because of i ts

cont ro l i n r e s t o r i n g o r i g i n a l t o p s o i l depths. Larger volumes of t o p s o i l

- 62 -

can be i n i t i a l l y pushed by dozer back over t h e s t r i p p e d a r e a but a g r a d e r

can do a more e f f i c i e n t job i n f i n i s h i n g o f f and e s t a b l i s h i n g uniform top-

s o i l depths .

C u l t i v a t i o n s h o u l d be done t o a l l e v i a t e compaction over t h e e n t i r e

s t r i p p e d a r e a p r i o r t o t o p s o i l replacement .

5.3 PROCEDURES FOR SPECIAL FIELD SITUATIONS

The main s p r e a d of a p i p e l i n e p r o j e c t is i n t e r u p t e d by roads , r a i l w a y s ,

i r r i g a t i o n and d r a i n a g e c a n a l s , and f o r e i g n p i p e l i n e s . A t each o f t h e s e

l o c a t i o n s , a c t i v i t i e s a r e c o n c e n t r a t e d and prolonged, c r e a t i n g more d i s -

tu rbance . M o d i f i c a t i o n s must be made t o normal c o n s t r u c t i o n p rocedures t o

accommodate t h e s e c o n s t r u c t i . o n a c t i v i t i e s and t o reduce t h e i r e f f e c t on

t h e s o i l .

The fo l lowing sect i o n s d i s c u s s recommendat i o n s t o reduce s o i l d i s t u r b a n c e

a t each of t h e s e s i t e s .

5.31 Road, Rail and Canal Crossings

Roads, r a i l w a y s and c a n a l s a r e u s u a l l y bored t o avoid damage and i n t e r -

f e r e n c e t o t h e s e f a c i l i t i e s . A s well, t h e p ipe is u s u a l l y bur ied a t

g r e a t e r depth t o p r o t e c t i t from damage.

Because l a r g e , e x c a v a t i o n s a r e r e q u i r e d on both s i d e s of t h e c r o s s i n g t o

p rov ide a c c e s s f o r bor ing and p ipe t i e - i n s , e x t e n s i v e mixing and l o s s of

t o p s o i l can occur . Topso i l should be removed f r a n t h e excava t ion and

s p o i l s t o r a g e a r e a s and, i f used a s a ramp over t h e ba r d i t c h , should be

p roper ly r e p l a c e d . Poor rec lamat ion a t t h e s e c r o s s i n g s may no t be repre -

s e n t a t i v e of r e c l a m a t i o n on t h e r i g h t of way; n e v e r t h e l e s s , they a r e

h i g h l y v i s i b l e .

Road c r o s s i n g s a r e conven ien t a c c e s s p o i n t s t o and f r m t h e r i g h t o f way.

The c o n c e n t r a t e d a c t i v i t y a t t h e s e p o i n t s i n c r e a s e s t h e p o t e n t i a l f o r

impact t o t h e s o i l .

A t c r o s s i n g s on c u l t i v a t e d l a n d s , t o p s o i l should be s a l v a g e d from t h e

t r e n c h , s p o i l s t o r a g e and work a r e a s and back approx imate ly 30 m depending

on t h e extent of t h e b e l l ho le r e q u i r e d . ( F i g u r e 5.7A). Access ramps

a c r o s s t h e bar d i t c h s h o u l d be c o n s t r u c t e d with s u b s o i l graded from a r e a s

where t o p s o i l h a s been s t r i p p e d . Topsoi l can be s t o c k p i l e d on e i t h e r o r

both s i d e s of t h e r i g h t of way. I f s t o c k p i l e d on t h e s p o i l s i d e , t o p s o i l

- 64 -

I I APPROX. 3 0 m

S P O I L FROM B E L L H O L E

RAMP OVER

. . , . 7 T O P S O l L . . . . (Y.

. - I I PLAN VIEW

N.T.S.

1. REMOVE T O P S O I L FROM THE TRENCH, B E L L HOLE, S P O I L STORAGE AND WORK AREAS ON C U L T I V A T E D L A N D S * STRIPPED T O P S O I L BACK FROM ROAD W I L L BE APPROXIMATELY 30 Me STORE T O P S O I L ON S P O I L OR WORK S I D E S BOTH ADJACENT TO S T R I P P E D AREA* I

1 2. GRADE S T R I P P E D AREA AND USE GRADED M A T E R I A L TO RAMP BAR D I T C H AS R E Q U I R E D * I 3- EXCAVATE TRENCH AND B E L L HOLE AND STORE ON S P O I L S I D E ADJACENT TO THE

E X C A V A T I O N * ALLOW FOR AT L E A S T 1 M SEPARATION BETWEEN THE T O P S O I L BERM AND THE EXCAVATED S P O I L -

I 4- RETURN S P O I L TO EXCAVATION AND COMPACT* L E A V E A ROACH OVER EXCAVATED AREAS TO ALLOW FOR SUBS I DENCE*

5. RETURN S U B S O I L M A T E R I A L FROM BAR D I T C H AND SPREAD EVENLY OVER THE S T R I P P E D AREA TO E S T A B L I S H OR I G I NAL COIVTOUR A L L E V I A T E COMPACT I ON OF CLAY R 1 CH SUBS0 I LS OVER THE S T R I P P E D A R E A * I

I 6. RETUHM T O P S O I L EVENLY OVER THE S T R I P P E D AREA- I 1 7 -

A L L E V I A T E COMPACTION OF T O P S O I L OVER E N T I R E R I G H T OF WAY AND STORAGE AREAS- I

FIGURE 5.7A

1 SOIL HANDLING AT ROAD, R A I L AND I I CANAL CROSSINGS (CULTIVATED LANDS ) I

should be placed f a r enough from t h e b e l l hole t o accommodate s to rage of

a l l of t he t rench s p o i l with a one metre s epa ra t ion between i t and t h e

s p o i l p i l e . Since r i s k of mixing is minimized by s t o c k p i l i n g t o p s o i l on

the work s ide , t h i s procedure is prefer red .

Acquisit ion of ex t r a working space a t road and o ther c ros s ings is essen-

t i a l t o accomodate e x t r a ma te r i a l s generated and t o proper ly conserve top-

s o i l . I n s u f f i c i e n t working space and r e s u l t i n g overlap of s t o r a g e p i l e s

is still the major cause of poor reclamation a t such loca t ions .

On pasture land t o p s o i l should be salvaged from any excavated or graded

a rea and a t l e a s t 1 m on each s i d e of t h e b e l l hole excavation.

(Figure 5.78). Topsoil should be p i l ed or spread over t h e work s i d e t o

keep it away from the excavated s p o i l . P i l i n g t o p s o i l is p re fe r r ed unless

compaction of t he s u b s o i l is determined t o be a problem, then spreading on

the work s i d e is more appropr ia te .

5.32 Foreign Line Crossings and Test S i t e s

A t foreign p ipe l ine c ros s ings the fore ign l i n e is exposed p r i o r t o main-

l i n e cons t ruc t ion and t h e new pipe i n s t a l l e d underneath t h e e x i s t i n g

foreign l i n e . Excavation of s i t e s for fore ign p i p e l i n e c ross ings and

p i p e l i n e t e s t i n g is i n i t i a l l y done by hand t o l1daylightl1 t he pipe and then

completed with a backhoe. The excavation is usua l ly wider and deeper than

t h e adjacent mainline t rench, genera t ing a l a r g e r s p o i l p i l e and s to rage

area.

On c u l t i v a t e d land, t o p s o i l should be salvaged from the b e l l h o l e and s p o i l

s to rage a reas with allowance for a one metre s epa ra t ion of t h e spo i l and

be l lho le f r m any s t o r e d or undisturbed t o p s o i l (F igure 5.8). Topsoil is

s to red on the work s i d e by c r e a t i n g a ramp over t h e fore ign "hot" pipe-

l i n e to pro tec t it from cons t ruc t ion equipment.

In pas ture land, t o p s o i l salvaged from the be l lho le a r ea and from a t l e a s t

one metre on both s i d e s of t h e excavation w i l l minimize mixing of t o p s o i l

and subso i l during b a c k f i l l and cleanup. As with c u l t i v a t e d lands, top-

- 66 -

I UNSTRIPPED TOPSOIL I ? t & -SPOIL FROM BELLHOLE

RAMP OV -- , ,

BAR DITCH \TOPSOIL FROM *.

. . &, . . ( SPOIL OVER BELLHOLE ' . ', u. . . . . . .

P L A N V IEW N.T.S.

NOTES

1. REMOVE T O P S O I L FROM THE TRENCH, AND B E L L HOLE AREAS, AND 1 M ON BOTH S I D E S O F E X C A V A T E D A R E A S - STORE T O P S O I L Oti WORK S I D E A D J A C E N T TO S T R I P P E D AREA BY P L A C I A G I N A P I L E , OR S P R E A D I N G OVER THE WORK AREA.

2. E X C A V A T E B E L L HOLE. USE E X C A V A T E D S P O I L TO RAMP BAR D I T C H - STORE R E M A I N I N G E X C A V A T E D S P O I L ON S P O I L S I D E A D J A C E N T TO B E L L HOLE.

3 . R E T U R N S P O I L TO B E L L HOLE AND COMPACT- REMOVE RAMP, RETURN F I A T E R I A L TO B E L L HOLE AREA AN11 COMPACT. FEATHER OUT EXCESS S P O I L OVER S T R I P P E D AREA L E A V I N G A HOACH C E N T R E D OVER THE B E L L HOLE.

4 - R E T U R N T O P S O I L E V E N L Y OVER THE S T R I P P E D AREA.

5 . R E S E E D W I T H A C O M P A T I B L E SEED M I X AND F E R T I L I Z E .

FIGURE 5 . 7 8

S O I L HANDLING AT R O A D , RA IL AND

CANAL CROSSlNGS ( PASTURE LANDS

AUG.. 1 9 8 4

>

I& FOREIGN

, . . , . .

. :.. . . . . . . . .

UNSTRIPPED T OPSOlL

PLAN VIEW N.T.S.

NOTES

1- REMOVE T O P S O I L FROM OVER THE EXCAVATION AND UNDER THE S P O I L STORAGE AREAS ON C U L T I V A T E D LAND FROM OVER THE EXCAVATION AND 1 M ON BOTH S I D E S OF THE EXCAVATED AREA ON PASTURE L A N D * STORE T O P S O I L AS A RAMP ON THE WORK S I D E ADJACENT TO THE S T R I P P E D AREA*

29 EXCAVATE TRENCH AND STORE M A T E R I A L ON S P O I L S I D E *

3 . RETURN S P O I L TO TRENCH AREA AND COMPACT* L E A V E A ROACH CENTERED OVER THE E X C A V A T I O N TO ALLOW FOR S U B S I D E N C E *

4- RETURN T O P S O I L EVENLY OVER THE S T R I P P E D AREA*

5 - A L L E V I A T E COMPACTION OF T O P S O I L OVER THE E N T I R E R I G H T OF WAY AND GROOM I N ACCORDANCE W I T H THE REST OF THE R I G H T OF WAY ON C U L T I V A T E D L A N D * RESEED W l T H A C O M P A T I B L E SEED M I X AND F E R T I L I Z E I N ACCORDANCE W l T H THE REST OF THE R I G H T OF WAY OH PASTURE L A N D *

FIGURE 5.8

SOIL HANDLING AT FOREIGN LINE

CROSSINGS AND TEST SITES

AUG., 1984

s o i l is ramped on the work s ide . In pas ture o r forage land, s p o i l can be

s t o r e d on a s t a b l e vege ta t ive mat.

5.33 Grading

Where grading is requi red for r i g h t of way preparat ion or t o accommodate

bending requirements of t he pipe, t o p s o i l should be salvaged from t h e

e n t i r e graded area and the graded and t rench s p o i l s to rage a reas . Extra

working space is usua l ly required t o accommodate both s to rage of t he grade

s p o i l and the e x t r a s t r i p p e d topso i l .

In pas ture , t o p s o i l is only removed f ran the a rea t o be graded. Topsoil

and s p o i l a r e both placed on the undisturbed vegetat ion mat.

On c u l t i v a t e d lands, t o p s o i l is removed from t h e a rea where t h e grade

s p o i l p i l e w i l l be placed. A s with t h e t rench s p o i l p i l e , t h e grade s p o i l

p i l e r equ i r e s a s epa ra t ion of one metre from any topso i l .

The l i m i t a t i o n s of t h i s procedure occur where t o p s o i l is not placed u p h i l l

for easy recovery, on t h i n t o p s o i l s , o r where working space is r e s t r i c t e d

by topography.

5.4 EXTRAORDINARY CONDITIONS

5.41 Wet Soil Conditions

Working i n wet cond i t i ons when t h e s o i l is near o r beyond s a t u r a t i o n , can

have l a s t i n g negat ive e f f e c t s on s o i l p r o p e r t i e s and capab i l i t y . Wet con-

d i t i o n s usua l ly occur during summer cons t ruc t ion under heavy r a i n f a l l , o r

i n winter during pe r iods of thaw. Wet work may a f f e c t s o i l c a p a b i l i t y

by compaction of c l ay s o i l s , by mixing of t o p s o i l with subsoi l through

r u t t i n g and by s t r u c t u r a l changes t o the t o p s o i l . More clean-up e f f o r t is

of ten requi red t o amend the e f f e c t s of compaction and mixing;

Measures fo r reducing s o i l damage under wet weather cond i t i ons a re :

( a ) Shut-down or Avoidance

( b ) S o i l Handling Procedures

( c ) Construct ion Procedures

( d ) Reclamation Procedures

Shut-down or Avoidance

The simplest approach t o wet weather is t o s t o p cons t ruc t ion when s o i l s

become s u s c e p t i b l e t o deformation or a l t e r a t i o n . I f poss ib le , construc-

t i o n opera t ions should be timed t o co inc ide with dry periods when damage

t o s o i l s t r u c t u r e can be minimized. Since i t is not always p r a c t i c a l to

schedule cons t ruc t ion ope ra t ions fo r dry per iods , cons t ruc t ion and r ec l a -

mation procedures t o reduce and recondi t ion s o i l compaction a re required.

Damage t o s o i l s , p a r t i c u l a r l y during wet cond i t i ons , is very d i f f i c u l t t o

de t ec t during cons t ruc t ion , and usua l ly can only be assessed once con-

s t r u c t i o n is complete. Few c r i t e r i a e x i s t f o r determining when s o i l

damage w i l l occur and when t o shut a p ro j ec t down. One method used by

some companies is t o shut down when r u t t i n g s t a r t s t o br ing up subso i l .

Some c o n t r a c t o r s work a s long a s they can get crew buses onto the r i g h t of

way. Others shut down when cons t ruc t ion p roduc t iv i ty drops. In most

ca ses , t h e ope ra t ions which shut down f i r s t involve earthmoving o r s t r i n g -

- 70 -

ing. These are a lso the operations which have the greatest impact on the

s o i l . Welding, the prime determinant o f construct ion progress, i s nor-

mal ly shut down l a s t . On a l a rge job wi th automatic welding ca r r ied out

under weatherproof covers, welding can proceed under almost any cond i t ions

prov id ing the crews can gain access t o the r i g h t o f way.

Soil Handlinq Procedures

Topsoi l may be removed from the trench, s p o i l and work areas t o avoid r u t -

t i n g and mixing o f t o p s o i l w i th subsoi l , and to accomodate the c u l t i v a t i o n

o f compacted B horizons. A disadvantage i s ponding o f water on the r i g h t

o f way from disrupted cross drainage and a compacted impermeable c lay r i c h

subso i l a t the surface. D i f f i c u l t i e s i n c u l t i v a t i n g compacted subsoi l may

occur i f the subso i l does not dry enough t o shat ter when cu l t i va ted .

The unstable nature o f wet s o i l may requ i re changes t o t o p s o i l handling

procedures. I f the s o i l i s already saturated and construct ion must

proceed, s t r i p p i n g t o p s o i l w i th a wide blade may r e s u l t i n poor separat ion

o f the topso i l , l o s s of t r a c t i o n and spinning causing mixing, compaction,

and a l t e r a t i o n o f the s t ruc ture o f the I3 horizon. Trench width s t r i p p i n g

wi th a wide pad machine i s requ i red t o prevent compaction adjacent t o the

trench. Trench width s t r i p p i n g i n t h i s s i t u a t i o n i s sometimes best accom-

p l i shed w i t h a backhoe. Using a wheel trencher i s l i k e l y t o c log up the

buckets and a dozer or grader f i t t e d w i th a stepblade w i l l probably sp in

out.

Construction Procedures

Three methods which may reduce s o i l damage dur ing wet s o i l condi t ions are:

a) r e s t r i c t e d t r a f f i c lanes

b) surface p ro tec t i o n

c ) low ground pressure vehic les

The concept o f r e s t r i c t i n g t r a f f i c t o s p e c i f i c paths ar ises from research

on compact i on i n a g r i c u l t u r a l operations. The greatest degree o f compac-

t i o n occurs from the reduct ion o f la rge pore space i n the s o i l on the

- 71 -

f i r s t pass . Subsequent passes then inc rease compaction t o its maximum fo r

t he weight of t he machinery employed. I f t r a f f i c is r e s t r i c t e d t o spec i -

f i c d r iv ing pa ths , compaction w i l l occur only on those a r ea s and w i l l be

minimal elsewhere.

The t y p i c a l r i g h t of way con f igu ra t i on used i n p i p e l i n e cons t ruc t ion

f a c i l i t a t e s easy implementation of t h i s procedure. A s i n g l e lane t r a c k

could be used on the bypass a r e a with a second t r a c k developed fo r welding

t rucks and t racked veh ic l e s along the work a rea .

Sur face p ro t ec t i on has l im i t ed usefu lness due t o the high cos t . Methods

inc lude swamp mats, g r a v e l l i n g with g e o t e x t i l e underlays, and po r t ab l e

roads. While p o t e n t i a l l y app l i cab l e to a g r i c u l t u r e lands , t h e i r use l i e s

p r imar i ly i n s p e c i a l t y app l i ca t i ons such a s i n muskeg.

Low ground pressure veh ic l e s have been used i n moderately wet cond i t i ons

without s i g n i f i c a n t damage t o t he s o i l . Major r e s t r i c t i o n s on these

vehic les a r e t h e t r a n s p o r t a t i o n c o s t s and t h e i r u n s u i t a b i l i t y on paved

roads. Table 5.1 lists typi.ca1 p ipe l ine equipment and ground pressures .

Reclamation Procedures

Measures used t o remedy s o i l impacts caused by wet weather work inc lude :

a ) t i l l a g e and subso i l i ng t o a l l e v i a t e compaction, and

b) the add i t i on of s o i l amendments t o i nc rease organic mat ter .

Natural forces , such a s freeze-thaw a r e a c t i v e i n t he upper soi.1 l a y e r s

and can slowly a l l e v i a t e some compaction. Usually more a c t i v e measures

a r e requi red t o loosen compacted s o i l s . Conventional t i l l a g e can be used

i f compaction is within 20 cm of the sur face . Chise l ploughs should be

used i f compaction occurs between 20 - 30 cm. When compacted s u b s o i l is

covered with t o p s o i l , deep plowing may be used i n some s i t u a t i o n s without

s i g n i f i c a n t l y mixing the two hor izons ; although, i t is e a s i e r t o remedy

compaction i n s u b s o i l i f the t o p s o i l has been removed. Addit ions of

organic mat ter i n combination with t i l l a g e and f e r t i l i z a t i o n can be bene-

f i c i a l i n a l l e v i a t i n g compaction i n o ther s i t u a t i o n s .

- 72 -

TABLE 5.1

GROUND PRESSURES FOR T Y P I C A L PIPELINE EQUIPMENT

+

Ground Pressure ( p s i ) Ki lopascals

DOZERS D6 7.1 - 9.4 49-65

D 7 8.6 - 10.3 59-71

D9 13.6 - 17.1 94-1 18

GRADERS 225 4 5 310

BACKHOES 225 7 48

23 5 8 5 5

245 12 83

SIDEBOOMS 561 11 76

(unloaded) 583 12 83

5 91 15 103

(rnax. load) 561 24 165

583 3 2 220

591 4 1 280

STRINGING TRUCKS 70 480

(loaded)

Where c o n s t r u c t i o n i n wet c o n d i t i o n s causes mixing of s u b s o i l and t o p s o i l ,

o rgan ic amendments, such a s manure, a r e u s e f u l i n i n c r e a s i n g t h e o rgan i c

ma t t e r con ten t o f t h e roo t zone. Also, fo rage c rops and o t h e r s o i l bu i ld -

i n g vege ta t ion can be p l a n t e d t o i n c r e a s e t h e o rgan i c con ten t . F e r t i l i z a -

t i o n can s t i m u l a t e p l a n t growth and he lp t o r e s t o r e l o s t p r o d u c t i v i t y pro-

duced by l o s s o f o rgan i c mat te r .

5.42 Frozen S o i l Conditions

There a r e advantages and d i sadvantages t o i n s t a l l i n g p i p e l i n e s i n f rozen

s o i l . On a g r i c u l t u r a l l a n d , t h e d i sadvantages gene ra l l y - outweigh t h e

advantages.

One advantage is t h a t compaction is g r e a t l y reduced s i n c e t h e ground i s

f rozen . S i m i l a r i l y , weather and s o i l cond i t i ons a r e more p r e d i c t a b l e

throughout t h e c o n s t r u c t i o n per iod.

A major problem is t h e d i f f i c u l t y of s e p a r a t i n g f rozen t o p s o i l from sub-

s o i l . S t r i p p i n g f rozen t o p s o i l wi th convent iona l equipment u s u a l l y

r e s u l t s i n mixing because o f poor depth c o n t r o l . Ripping t o p s o i l is some-

times done but because of "lumpinessll o f t h e excavated m a t e r i a l and poor

depth c o n t r o l , i t is not recommended. A s t anda rd b l ade on a dozer o r

g r ade r is not e f f e c t i v e i f t he f r o s t has pene t r a t ed i n t o t h e subso i l .

However, i f f r o s t p e n e t r a t i o n is only t o t h e t o p s o i l depth and t h e s u b s o i l

is r e l a t i v e l y dry, a b lade can be very e f f e c t i v e f o r t o p s o i l s t r i p p i n g .

Double o r p i l o t t r ench ing with a wheel t r e n c h e r is t h e most common proce-

dure for main l ine t o p s o i l s a lvage i n f rozen s o i l cond i t i ons . There a r e ,

however, two drawbacks t o t h e use of a wheel t r enche r . F i r s t , i t was not

designed t o s t r i p sha l low l i f t s , consequent ly t h e r e is g r e a t e r s t r a i n on

t h e d r i v e t r a i n . I n a d d i t i o n , t h e r e is a s p i l l o v e r of t o p s o i l from t h e

bucke ts which reduces t h e amount of t o p s o i l sa lvaged. With s u i t a b l e

equipment mod i f i c a t i ons t h e s e problems can be p a r t i a l l y overcome.

The major problem with f rozen s o i l s t r i p p i n g ope ra t i ons is depth con t ro l .

With a convent iona l wheel t r e n c h e r , t h e minimum depth of s t r i p p i n g is i n

- 74 -

t h e o r d e r of 25 cm, a l though t o produce enough volume t o handle e f f i c i e n t -

l y , a s t r i p p i n g depth o f 30 cm o r more may be r e q u i r e d . This depth w i l l

u s u a l l y c o n t a i n t o p s o i l and s u b s o i l m a t e r i a l .

Sa lvag ing f rozen t o p s o i l a t road c r o s s i n g s , f o r e i g n l i n e c r o s s i n g s , graded

a r e a s and t i e - i n s is a g r e a t e r problem than mainl ine t o p s o i l sa lvage .

These s i t u a t i o n s r e q u i r e t h a t t o p s o i l be removed over widths g r e a t e r than

a s t a n d a r d t r e n c h width. Wheel t r e n c h e r s a r e slow and c o s t l y and, whi le a

b l a d e i n con junc t ion with r i p p i n g performs better, it is still i n e f f e c t i v e

f o r s a l v a g i n g f rozen t o p s o i l .

Another d i sadvan tage of win te r c o n s t r u c t i o n is t h a t f rozen s o i l bu lks more

t h a n dry s o i l , caus ing o v e r f i l l i n g of the t r e n c h and e x t e n s i v e roaching.

The s i z e of t h e roach w i l l vary but i n most c a s e s w i l l u s u a l l y ex tend

beyond t h e t r e n c h a s replacement of s p o i l r e s u l t s i n some of t h e s p o i l

being f e a t h e r e d over a width of up t o 3 m. If t o p s o i l has not been s a l -

vaged over t h i s width , s u b s o i l w i l l be l e f t on t o p of t o p s o i l and w i l l be

mixed when t h e a r e a i s c u l t i v a t e d . To minimize mixing, a b lade width o f

t o p s o i l should be sa lvaged t o accomodate replacement of s p o i l . I f a b lade

width of t o p s o i l cannot be sa lvaged , t h e s p o i l should be p laced and com-

pac ted i n t h e t r e n c h i n m u l t i p l e l i f t s . The c o m p a c t a b i l i t y of t h e s p o i l

w i l l depend on t h e amount of f r o s t and t h e t e x t u r e of t h e s p o i l .

Frozen s p o i l is not e a s i l y compacted and sunken t rench may r e s u l t upon

thawing. If r e p l a c e d p r i o r t o t r ench subs idence , t o p s o i l m a t e r i a l may be

l o s t and a d d i t i o n a l t o p s o i l placement requ i red . I f t o p s o i l h a s not been

r e p l a c e d p r i o r t o subs idence , t h e t r e n c h l i n e can be reworked with s u b s o i l

m a t e r i a l s p r i o r t o t o p s o i l replacement.

If only a t r e n c h width of t o p s o i l has been sa lvaged , r e c o n t o u r i n g t h e

sunken t r e n c h l i n e wi th a b lade may be imposs ib le without a f f e c t i n g t h e

u n d i s t u r b e d t o p s o i l a d j a c e n t t o t h e t r ench . Recontouring with a b l a d e i n

t h i s s i t u a t i o n w i l l i n e v i t a b l y mix und is tu rbed t o p s o i l wi th b a c k f i l l

m a t e r i a l .

Working with frozen s o i l s can, i n a v a r i e t y of ways, l ead t o poor clean up

and ex tens ive mixing of t o p s o i l and subso i l . F i r s t l y , s o i l ma te r i a l s a r e

very d i f f i c u l t t o properly l eve l and recontour under frozen condit ions,

o f ten n e c e s s i t a t i n g a r e t u r n v i s i t for f i n a l reclamation during t h e

following spr ing . It is during t h i s f i n a l v i s i t , while reworking pre-

viously excavated ma te r i a l s , t h a t compaction and s o i l mixing can become a

major problem. Secondly, t opso i l and subso i l p i l e s a r e of ten covered by

snow, making t h e i r recovery more d i f f i c u l t . Excessive snow mixed with

t o p s o i l and subso i l can a l so inc rease t h e amount of roach over t h e d i t ch

l i n e and the depth of sunken t rench. A t h i r d problem encountered when

working with frozen s o i l s is tha t colour d i f f e r ences between topso i l and

subso i l a r e l e s s de t ec t ab le , making proper s epa ra t ion of s o i l s more

d i f f i c u l t .

F ina l clean-up of a winter p ipe l ine opera t ion should not be done u n t i l

spr ing. Backf i l l i ng i n t h e winter is done t o r e f i l l and compact t h e

t rench , with excess t rench s p o i l mounded over the t renchl ine . In the

spring, s p o i l is f u r t h e r compacted i n t o the t rench and the t rench a r e a

l eve l l ed . Topsoil is then replaced over t h e d is turbed area.

Ear ly consu l t a t i on with the landowner is c r i t i c a l i f clean-up is to be

l e f t u n t i l sp r ing or l a t e r . Often, t he farmer has a very sho r t period i n

sp r ing t o work the land and get h i s crop in . A p a r t i a l l y completed r i g h t

of way can be a hindrance t o h i s opera t ions . In some in s t ances t h e land-

owner w i l l c u l t i v a t e over a p a r t i a l l y reclaimed r i g h t of way and t o p s o i l

w i l l be p a r t i a l l y or completely l o s t . This s i t u a t i o n should be avoided.

5.43 Irrigated Lands

The most common i r r i g a t i o n systems i n Alberta a r e flood and s p r i n k l e r sys-

tems. Flood systems r equ i r e l e v e l f i e l d s while s p r i n k l e r systems a r e

of ten used on the more undulat ing t e r r a i n . During flood i r r i g a t i o n , water

is re leased onto the f i e l d and flows by g r a v i t y t o cover t h e e n t i r e

f i e l d . Any i r r e g u l a r i t y i n t he topography w i l l i n t e r r u p t t h i s flow.

Sp r ink le r systems move on l a r g e wheels across t h e f i e l d and a r e not a s

a f f ec t ed by topographic i r r e g u l a r i t i e s . However, t h e wheels can get s tuck

- 76 -

on mounds or i n depressions. The p ipe l ine t rench , i f more permeable than

the surrounding s o i l can a l s o ac t a s a condui t fo r drainage, eroding o r

s ink ing and causing damage t o s p r i n k l e r systems.

S o i l handling procedures on i r r i g a t e d lands should ensure t h a t t he trench-

l i n e and r i g h t of way a r e reclaimed t o a s o l i d l e v e l s u r f a c e and should be

. t a i l o r e d t o the a g r i c u l t u r a l p r a c t i c e s used. Compaction of subso i l i n t he

t rench during b a c k f i l l i n g is recommended. Mounding t o a1 1 ow for subse-

quent subsidence of dry s o i l s a f t e r i r r i g a t i o n is important. I f s p r i n k l e r

systems are used, wheel paths across t rench mounds should be provided.

Trench plugs should be considered t o i n h i b i t drainage alorig t h e trench-

l i n e .

Construct ion timing may a l s o be a c r i t i c a l f a c t o r and w i l l r e q u i r e consul-

t a t i o n with the landowner, o r fo r a l a r g e p r o j e c t , the I r r i g a t i o n D i s t r i c t

Manager. I f pos s ib l e , cons t ruc t ion should be scheduled during a dry

period.

Pos t -cons t ruc t ion monitoring i n i r r i g a t i o n a r e a s is required. Despi te a l l

reasonable measures, t h e r e w i l l be a r e a s of excess mounding o r sunken

t rench which w i l l r e q u i r e r epa i r .

5.44 Three Phase Soil Handling

Three phase s o i l handl ing is a procedure i n which ma te r i a l s handling is

done i n t h r e e phases; t o p s o i l s t r i p p i n g , excavat ion of b e t t e r q u a l i t y sub-

s o i l , and f i n a l l y , removal of undes i reab le q u a l i t y s u b s o i l t o t rench

depth. (Figure 5.9). This procedure is used t o prevent lowering of t he

root zone q u a l i t y caused by mixing with poorer q u a l i t y ma te r i a l . Separa te

removal of t h i s undes i reab le mater ia l permits its replacement i n t h e

t r e n d a t depths removed from the roo t zone.

Topsoil is s t r i p p e d over a width adequate t o s t o r e and s e p a r a t e the two

subso i l p i l e s from the t o p s o i l . This width w i l l vary from 7 t o 9 m f o r a

t y p i c a l s i t u a t i o n . Larger t renches w i l l genera te more s p o i l and t h e r e f o r e

more requi red s t o r a g e space.

R/ W TRENCH R/W BDY. SPOIL S IDE WORK SIDE BDY.

I I

UND TOP

N .T.S.

R/ W SPOIL SIDE TRENCH WORK SIDE R/W BDY. BDY.

UNDISTURB

UNDESIREABLE S

WIDTH OF TOPSOIL STRIPPING - PROFILE 8

N.T.S.

NOTES

1- REMOVE T O P S O I L FROM OVER THE TRENCH AND UNDER T I i E S P O I L P I L E S - S T R I P P E D W I D T H W I L L BE 7 TO 9 11. STURE T O P S O I L ON S P O I L S I D E ADJACENT TO S T R I P P E D A R E A -

2 - E X C A V A T E F I R S T LIFT OF THENCH SUBSOIL AND S T O R E ON SPOIL SIDE EITHER A D J A C E N T 'ro THE TRENCH ( A ) OR BACK FAR ENOUGH TO ACCOMIIODATE STORAGE OF SECOND S U B S O I L L I F ' r ( B ) . ALLOW FOR A 1 M S E P A R A T I O N BETWEEN THE T O P S O I L P I L E AIJD THE TRENCH S P O I L *

3 - E X C A V A T E SECOND L I F T UF TRENCH S U B S O I L AND STORE ADJACENT TO THE TRENCH E I T H E R ON THE WORK S I D E ( A ) OR THE S P O I L S l D E ( B ) . ALLOW FOR A 1 M S E P A R A T I O N BETWEEN T i i E TWU THEl lCH S P O I L P I L E S (B) THE SECOIJD L I F T S P O I L P I L E AND THE U N D I S T U H B E D T O P S O I L ON THE WORK S I DE ( A ) .

4 - RETURN SECOND L l F T TRENCH S P O I L TO THE THENCH AND COMPACT-

5. RETURN F I R S T L l F T THENCH S P O I L TO THE TREIJCH AND COMPACT. FEATHER EXCESS S P O I L OVER THE S T R I P P E D A R E A - A L L E V I A T E COt. lPACTlON OF CLAY R I C H S U B S O I L S OVEH THE S T R I P P E D A R E A *

6 . RETURN T O P S O I L EVErJLY OVER THE S T R I P P E D AREA.

7 . A L L E V I A T E COMPACTIU lJ OF T O P S O I L OVER E N T I R E R I G I i T OF WAY ON C U L T I V A T E D LANDS.

FIGURE 5.9

THREE PHASE SOIL HANDLING

AUG., 1 9 8 4

Once t o p s o i l has been removed, t he f i r s t l i f t of t he d e s i r a b l e subsoi l is

' excavated, p r e f e r r ab ly with a wheel t rencher . Minimum r a t e d depths for

wheel t r enche r s a r e i n t h e range of .6 m t o 1 m. Due t o excess s t r a i n on

the d r ive t r a i n , modif icat ions t o the t rencher a r e normally required i f

shal lower depths a r e excavated over long d is tances . However, s i nce dual

l i f t s a r e normally only s p e c i f i e d for r e l a t i v e l y sho r t d i s t a n c e s ((1 km)

t h e requirement fo r shallow digging can usua l ly be accommodated without

major equipment modif icat ion. To f a c i l i t a t e handl ing, 30 cm of f i r s t l i f t

ma te r i a l is suggested a s a minimum which the t rencher can handle e f f ec -

t i v e l y .

The f i r s t l i f t of b e t t e r q u a l i t y subso i l is placed e i t h e r adjacent t o t h e

t rench on the s p o i l s i d e ( P r o f i l e A, Figure 5.9) o r next t o t he t o p s o i l

p i l e ( P r o f i l e B, Figure 5.9). The second l i f t of undes i rab le mater ia l is

then excavated and placed adjacent t o t he t rench on e i t h e r t he work or t h e

s p o i l s i d e . The minimum amount of ma te r i a l t h a t can be excavated i n t h e

f i n a l l i f t w i l l depend on ground condi t ions . Since two passes with t he

t rencher a r e requi red , t h e t rench wal ls have to be s t a b l e enough t o

support t h e second pass. In good ground condi t ions , t he minimum second

l i f t would be 40 cm, or from .8 m t o 1.2 m below o r i g i n a l grade for small

inch pipe. In poor condi t ions t h i s may not be poss ib le due t o i n s t a b i l i t y

of t rench wal ls .

On c u l t i v a t e d and forage lands both s u b s o i l p i l e s should be s t o r e d on sub-

s o i l . In pas tu re lands t he f i r s t l i f t can be s to red on t h e sod layer but

the second l i f t of undes i rab le s u b s o i l should be s t o r e d on s u b s o i l .

For big inch p ipe l in ing , both bulking and pipe s i z e w i l l s i g n i f i c a n t l y

a f f e c t t he height of the replaced s p o i l i n t h e trench. In most cases s ig -

n i f i c a n t o v e r f i l l i n g w i l l r e s u l t which w i l l r equ i r e mounding over t h e

t rench and f ea the r ing of ma te r i a l s on t h e r i g h t of way. O v e r f i l l i n g w i l l

r e s u l t i n some mixing of poorer and b e t t e r q u a l i t y subso i l s . However, i t is b e t t e r t o have good q u a l i t y subso i l near the su r f ace r a t h e r than an

ove ra l l mixture of both ma te r i a l s t o t rench depth. Depth and q u a l i t y o f

t he two s u b s o i l ma te r i a l s should be i nves t i ga t ed thoroughly p r io r t o

t renching opera t ions.

- 79 -

Application

This procedure would on ly be under taken where a t l e a s t 4 0 cm of poor qua l -

i t y s u b s o i l is encoun te red w i t h i n t r e n c h depth and is s e p a r a t e d from t h e

t o p s o i l by a t l e a s t 30 cm of d e s i r a b l e s u b s o i l . P r i o r t o de te rmin ing t h e

p r a c t i c a l i t y o f a t h r e e phase hand l ing o p e r a t i o n , chemical a n a l y s e s a r e

r e q u i r e d t o a s s e s s whether mixing of t h e two s u b s o i l s would s i g n i f i c a n t l y

degrade t h e b e t t e r q u a l i t y s u b s o i l . I f n o t , a t h r e e phase o p e r a t i o n may

not be war ran ted . Chemical a n a l y s e s shou ld i n c l u d e a mass ba lance ca lcu-

l a t i o n of both s u b s o i l s , e v a l u a t i o n of mixed and unmixed c h a r a c t e r i s t i c s

( i e . s a t u r a t i o n p e r c e n t a g e , e l e c t r i c a l c o n d u c t i v i t y o r SAR).

The s o i l and l a n d u s e s i t u a t i o n s where t h i s procedure is b e s t s u i t e d

inc lude :

a ) S o i l s under c u l t i v a t i o n , f o r a g e and p a s t u r e where poor q u a l i t y

m a t e r i a l o c c u r s w i t h i n t h e t r e n c h depth . The fo l lowing c r i t e r i a

shou ld be used t o de te rmine t h e a p p l i c a t i o n of t h i s procedure .

( i ) M a t e r i a l t o be t a k e n a s a f i r s t l i f t is g r e a t e r than

30 cm t h i c k .

( i i ) A t l e a s t 40 cm of u n d e s i r a b l e m a t e r i a l is a v a i l a b l e a s a

second l i f t .

( i i i ) A t l e a s t one of t h e c r i t e r i a i n d i c a t e d i n Table 5.2

shou ld e x i s t .

T a b l e 5.2 S u b s o i l C r i t e r i a

D e s i r a b l e M a t e r i a l Undes i rab le M a t e r i a l ( f i r s t l i f t ) (second l i f t )

E l e c t r i c a l C o n d u c t i v i t y < 5 a t l e a s t 4 u n i t s h i g h e r (EC) 5- 10 a t l e a s t 6 u n i t s h igher

> 70 N.A.

Sodium Absorpt ion Rat io* < 8 a t l e a s t 6 u n i t s h i g h e r (SAR) 8-12 a t l e a s t 8 u n i t s h i g h e r

> 12 N.A.

S a t u r a t i o n Percentage*" - - a t l e a s t 4096 h i g h e r t h a n d e s i r a b l e m a t e r i a l

S tone Content < 3 > 25 (% Val) 3-25 > 50

25-50 N.A. - 80 -

* SAR c r i t e r i a apply only t o ma te r i a l s t h a t a r e loam t o heavy c lay i n

t ex tu re . C r i t e r i a may be a l t e r e d by the presence of hi* l e v e l s o f

e i t h e r lime (CaC03) or gypsum (CaS04) i n excess of o the r so lub le

s a l t s .

** Sa tu ra t ion percentage c r i t e r i a apply only t o weathered bedrock

mater ia l s .

NA - Not Applicable -- mul t ip l e l i f t of the subso i l is not required.

Variation

The two most common v a r i a t i o n s of t h i s procedure a r e i l l u s t r a t e d i n

Figure 5.9. Both produce s i m i l a r r e s u l t s . I f t o p s o i l s a r e t h in and com-

pact ion of t he B horizon is a problem o r i f r i g h t of way widths a r e

r e s t r i c t e d , i t may be adviseable t o s t o r e and spread the s t r i p p e d t o p s o i l

over the work area . This e f f e c t i v e l y inc reases the organic buffer on

which cons t ruc t ion equipment t r a v e l s and reduces the compaction of t he B

horizon. I f t o p s o i l s to rage on the work s i d e is not a p r a c t i c a l s o l u t i o n

t o compaction, the work s ide should be s t r i p p e d so t h a t any compaction can

be worked up without a f f e c t i n g the t o p s o i l .

In pas ture land a b lade width s t r i p of t o p s o i l should be removed p r io r t o

t rench excavation. Topsoil is s to red on the work s i d e a s i n blade width

t o p s o i l s t r i p p i n g (F igure 5.3). The first l i f t of subso i l is depos i ted on

the s p o i l s i d e on the sod l aye r immediately adjacent t o t h e s t r i p p e d

area . Since t h i s l i f t is of r e l a t i v e l y good q u a l i t y mater ia l , i t can be

s a f e l y s to red on t h e sod layer . The f i n a l l i f t is then excavated and

s to red on subso i l a s c l o s e a s poss ib le t o t h e t rench to avoid contamina-

t i o n of adjacent s o i l s .

Sa l ine seepage a r e a s o f t en have b e t t e r q u a l i t y ma te r i a l s a t depth (higher

EC o r SAR values i n t he upper mater ia l r e l a t i v e t o the lower ma te r i a l ) .

Separa te removal of ma te r i a l s i n such a reas is not recommended.

Thin t o p s o i l s should be s t r i p p e d with a grader because of t h e g r e a t e r

depth c o n t r o l . Excavat ion of the two s u b s o i l l i f t s should be performed

with a bucket wheel t r enche r r a t h e r than by backhoe s i n c e i t is more

capab le of excava t i ng m a t e r i a l s t o a predetermined depth.

Ma te r i a l excavated and p u l v e r i s e d with a t r enche r can be a c c u r a t e l y placed

i n a uniform p i l e which prov ides b e t t e r s e p a r a t i o n from t o p s o i l dur ing

excava t ion , and a l lows b e t t e r compaction i n t he t rench dur ing b a c k f i l l i n g .

B a c k f i l l i n g of t h e two s u b s o i l p i l e s should be done with a g rader because

of t h e smal l volumes of ma t e r i a1 invo lved and t h e p r e c i s e n e s s r equ i r ed .

The t r ench should be compacted by g r ade r t i r e s a f t e r each of t he s u b s o i l

p i l e s has been rep laced . Th is wi.11 con f ine t h e undes i r ab l e ma t e r i a l t o

t h e t rench a s f a r from t h e t o p s o i l a s pos s ib l e .

The b e t t e r q u a 1 i . t ~ s u b s o i l should then be rep laced i n t h e t rench , com-

pacted and reworked t o r e s t o r e a uniform s u b s o i l s u r f a c e p r i o r t o t o p s o i l

replacement . Topsoi l should be r ep l aced with a g rader t o a uniform depth

over the d i s t u r b e d a rea .