Oil Spill Countermeasures for the Southern Beaufort Sea

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control l i ng and cleaning up of oi l spi l l s i n the offshore Beaufort Sea . ... bel i eved that , because of the short dri l l i ng season that shou l d a bl owout.
Oil Spill Countermeasures for the Southern Beaufort Sea W.J. LOGAN, D.E. THORNTON and S.l. ROSS Technical Report No.31a

OIL SPILL COUNTERMEASURES FOR THE SOUTHERN BEAUFORT SEA

W.J.

Logan, D. E.

Thornton and S. L.

Ross

Research and Development Division Environmental Emergency Branch Environmental Protection Service Department of the Environment Burlington, Ontario L7R 4A6

Beaufort Sea Technical Report #31a

Beaufort Sea Project Dept. of the Environment 512 Federal Building 1230 Government Street Victoria, B.C. V8W lY 4

December 1975

ACKNOWLEDGEMENTS

The authors wish to acknowledge the assistance of four companies whose studies formed the foundation of this report. PHILIP A. LAPP LIMITED MINING RESOURCES ENGINEERING LIMITED MONTREAL ENGINEERING COMPANY LIMITED NORCOR ENGINEERING AND RESEARCH LIMITED The authors would especially like to thank Mr. R. Brown of NORCOR for his direct assistance in the preparation of this report. Finally, the authors wish to acknowledge the advice and assistance received throughout the period of this study from colleagues in government and industry.

- i ABSTRACT

This report discusses the feasibilities of controlling and cleaning up an oil spill in the Beaufort Sea as a result of an exploratory It is likely that, in waters with up to 1 0% ice concentrations, well blowout. currently available oil spill countermeasures equipment and techniques No equipment is could be employed in sea conditions up to Beaufort 3 . available for use in higher sea conditions. If the blowout were to occur in the landfast ice zone, oil that would accumulate at the under-ice surface during winter could be incinerated in place when the oil migrates to the ice surface in the springtime. No viable techniques or proven countermeasures equipment are available for use in the seasonal pack, shear zone and the The cleanup and restoration of oil contaminated shorelines polar pack zone. would be limited to sand beaches and to a lesser extent, shingle beaches, which together comprise 37% of the Beaufort Sea shoreline. Remote sensing of oil spills, although untried in the arctic environment, would be limited to periods of good visibility. In general, the logistical base required to support an effective oil spill countermeasures operation is not available in the areas adjoining the Beaufort Sea.

- ii RESUME Le prese n t rapport tra i te des pos s i bli tes de con tr61 er et de nettoyer un deversement de petrole dans la mer de Beaufort engendre par 1 ' erupti on d ' un p u i ts d ' explora ti on . 11 e s t p robable q u e , dans des eaux dont 1 0% de la s u rface peut-etre couverte de glace , les techn i q u es et 1 ' eq u i pement a ctuellemen t u t i li ses d a n s la lu tte c�ntre les deversemen ts de petrole pourra i en t etre employes a 1 ' et a t de mer bas s e j us q u ' au nombre 3 de Beaufort . On ne d i s pose a c tuellement d ' a u c u n eq u i pmen t pou r le s eta ts d e mer s u per i eure . S i 1 ' erupti on deva i t s e produ i re dans u n e zone de glace fi xe , l e petrole accumule en des sous a u c ours de 1 ' hi ver pourra i t etre b rule sur place apres s ' etre i nfi ltre a la s u rface , a u pri n temp s . On ne p e u t a c tuellemen t recou ri r a d e s tec h n i q u es valables n i a des mes u res prouvees dans des zones de pack s a i s o nn i er , de c i sa i llemen t et de p a c k arcti q u e . Le nettoyag e e t la rem i s e en eta t des ri ves s ou i llees ne s ' a ppli q u era i en t q u ' au x plages s a blon neuses et , a u n degre moi ndre , aux plages de galet , representant en tout 37% de la li g n e de r i vage de la mer de Beaufort . La teledetecti on des deversemen ts d e petrole , encore i ned i te d a n s 1 ' Arcti q u e , s e ra i t l i mi tee a u x peri odes de bonne v i s i bi li te . E n general , il n ' ex i s te , dans les reg i ons con ti gUes de la mer de Beaufort , aucune i n s talla ti on pour a s s u re r un appu i log i s ti q ue a la lu tte c�n tre les deversements d e petrole.

- iii TABL E O F CONTENTS PAGE ABSTRACT

i

RESUME

ii

TABL E O F CONTENTS

iii

L I ST OF F I GURES

vi i

L I ST OF TAB L ES

vi i i

1

I n trod ucti on

1

2

Beaufort Sea P hys i ca l Envi ronment

3

2. 1

C l i matol ogy

3

2. 1 . 1 2. 1 . 2 2. 1 . 3 2. 1 . 4

3 5 5 5

2.2

2.3

Oceanogra phy

6

2. 2. 1 2. 2 . 2 2 . 2. 3

6 6 9

Currents T i des Waves

I ce Zones 2.3.1 2. 3 . 2 2.3.3

2.4

Ai r Tempera tures W i nd Day- n i g ht Reg i mes Prec i p i tati o n

9 Landfa s t I ce Zone Tra n s i t i on - i ce Zone Pol ar Pack Zone

11

S horel i ne 2.4.1 2 . 4. 2 2. 4 . 3 2. 4 . 4 2. 4 . 5 2. 4 . 6 2. 4. 7 2. 4 . 8 2.4.9 2. 4 . 1 0

9 10 11

Reg i on 1 - Y u kon-Al a s ka Border to Koma k u k Beach and Herschel I s l and Reg i on 2 - Koma k u k Beach to Ro l and Bay Reg i on 3 - Rol and Bay to Tre n t Bay Reg i on 4 - Trent Bay to Lower O l i ver I s l and and S h a l l ow Bay Reg i on 5 - Lower O l i ve r I s l and to P u l l en I s l and Reg i on 6 - P u l l en I s l and to Toker Poi n t and Kugma l 1 i t a n d Ki tti g a zu i t Bays Reg i on 7 - Toker P o i nt to Cape Dal hous i e Reg i on 8 - Cape Da l ho u s i e to N i c h o l son Poi n t and L i verpoo l Bay Reg i on 9 - E s k i mo ( H u s ky ) L a kes Reg i on 1 0 - N i c h o l son Poi n t to C a p e Bathurst and Wood Bay

13 14 15 16 17 18 19 20 21 22

- iv PAGE 3

4

Behav i ou r of a B l owo u t i n the Beaufort Sea

24

3. 1

Open Water

24

3. 2

I ce I nfes ted Waters

27

3.3

Landfas t- I ce Zone

28

3. 4

Seasonal Pac k - I ce

30

3. 5

Pol ar-Pack I ce

32

Oi l S p i l l Counte rmeas u res Techn i q ues

34

4. 1

S u rve i l l an c e and Mon i tori ng

35

4. 1 . 1 4. 1 . 1 . 1 4. 1 . 1 . 2 4. 1 .2

35 35 38

4. 1 . 3 4. 1 . 4 4. 1 . 4. 1 4. 1 . 4. 2 4. 1 . 4. 3 4. 1 . 4. 4 4. 1 . 4. 5 4. 1 . 5 4. 2

Remote Sens i ng Technol ogy Rad i o Frequenc i es Opti cal Freq u e n c i es Weather and F l y i n g L i mi tati o n s on A i rborne Remote Sen s i ng Other O i l Detec t i on Tec h n i ques Sys tems for O i l S p i l l S u rvei l l ance and Mon i tori ng F i rs t S tage S urve i l l ance Sys tems Second S tage S u rv e i l l an c e Sys tems F i r s t S tage Mon i to r i ng Second S tage Mon i tor i ng Remote S en s i ng P l atforms Concl u s i on s

40 44 46 46 48 48 48 48 49

O i l Contai nment and Removal

50

4. 2. 1 4. 2. 1 . 1 4. 2. 1 . 2 (a)

50 51 56 56 57 60 60 62 62 62 63

(b) 4. 2. 1 . 3 4. 2. 1 . 4 4. 2. 2. 4. 2. 3 4. 2. 4 4. 2. 5 4. 2. 6 4. 2. 7

Open Water O i l Contai nmen t i n Open Water O i l Removal i n O p e n Water Mechan i cal Recovery Wei r Dev i ces S u ct i on Dev i ces Sorbent Surface Dev i ce s Vortex Dev i ce s S u bmers i on Dev i ces Screw Conveyor Dev i ces O i l S p i l l Treati n g Agen ts Trans ferral , S to rage , Separat i on and D i sposal of Recovered O i l Open Water wi th S ome I ce ( u p to 1 0% I ce Cover ) I ce- I nfes ted Water ( 1 0- 1 00% I ce Cover ) Fast- I ce Zone Trans i t i on Zone Pol ar Pac k I ce Zone Sys tem Con s i derati o n s S ummary

65 68 72 73 76 78 80 80

- v PAGE 4.3

S horel i ne Protect i on and C l eanup 4.3.1 4.3.1 . 1 4.3. 1 .2 4.3.2 4.3.2.1 4.3.2.2

4.3.2.3 4.3.2.4 4.3.2.5

4.3.3 4.3.3.1 4.3.3.2 4.3.3.3 4. 3 . 3 . 4 4.3.3.5 4.3.4 4.3.4.1 4. 3.4.2 4.3.4.2 4.3.4.4 4.3.5 4. 3 . 5 . 1 4.3.5.2 4. 3. 5 . 3 4.3.5.4 4.3.6 4.4

Erod i ng C l i ffs On-shore Protec t i on Tec h n i ques C l ean u p Techn i ques Sand Beach On-Shore Protec t i on Techn i qu e s W i ndrowi ng Sorbents Cl ean u p Tech n i ques Compl ete Bea c h Cover Sma l l Areas of Con tami n a ted Beach Tarry L umps Tra n s ferra l of Contam i n a ted Materi a l Separa t i on of Con tami n a ted Materi a l Phys i ca l Separa t i on Chemi ca l Separa t i on Di s p o s a l of O i l - Contam i n a ted Sand In S i tu Burn i ng Inc i n era ti on P l ou g h i ng Buri a l I n S i tu Bu r i a l under Beach B a c k s hore Landfi l l i ng S h i ngl e Beac h On-S hore Protecti on Techn i ques Cl eanup Tec h n i ques Tra n s ferra l of Contami n a ted Mater i a l Separa t i on o f Con tami n a ted Materi a l Di s po s a l of O i l - Contami n ated Materi a l Tundra On-S hore Pro tect i on Techn i ques C l ean u p Tec h n i q ues Tra n s ferra l of Contami n a ted Materi a l Di s p o s a l of Con tami n a ted Materi a l Mudfl ats On-S hore P ro te c t i on Tech n i q ue s C l ean u p Tec hn i ques Tra n s ferra l of Contam i n a ted Mater i a l D i s p o s a l o f Contami nated Materi a l S umma ry

82 82 82 82 83 83 83 84 84 84 85 85 90 92 92 92 92 94 94 95 95 95 96 98 98 98 99 99 99 1 01 1 01 1 01 1 01 1 01 1 02 1 02 1 02 1 03 1 03 1 03

Opera t i onal Con s i dera t i ons

1 06

4.4. 1 4.4. 1 . 1

1 06

4. 4. 1 . 2 ·4 . 4 . 1 . 3

Tran s port Ava i l a b i l i ty of Fi xed W i ng and Rotary W i ng Ai rcraft Ava i l a b i l i ty of Mari n e Eq u i pment Surface Tra n s port

1 07 1 08 1 08

- vi PAGE 4.4. 2 4.4.3 4 . 4. 4 4.4.5 5

6

Commu n i cati ons a n d Nav i g a t i on Surface Opera ti ons La bou r Force C l eanup Equi pmen t

1 09 110 111 112

Conceptua l Tec h n i ques

114

5. 1

The Recovery Barge

114

5.2

The I ce - Retenti on Boom

115

5.3

The Conta i nment Dome

116

5. 3. 1 5.3.2 5.3.3 5.3.4

116 117 117 118

Fast I ce Zone Transi ti on Zone Pol a r Pack Zone S ummary

5.4

Trenc h i ng

1 18

5.5

F l ari ng the B l owo u t Gas

119

S ummary and Genera l Conc l usi on

REFERENCES

1 21 1 24

- vi i L I ST O F F I GURES F I GURE

PAG E

2.1

O i l Permi t

2.2.1

E s t i ma ted S urfa ce Ci rc u l a t i on i n the Southern Beau fort Sea duri ng S teady East W i nds

7

2.2.2

E s t i ma ted S u rface C i rc u l a t i on i n the Southern Beaufort Sea duri ng Northwe s t W i nds

8

2.4.1

S horel i ne Del i nea t i o n Reg i o n s

12

4.1 .1

Asses sment o f Remote Sen s i ng Technol og i e s

41

4. 1 . 2

S ummary of Sensor Performance wi th Envi ronmental Con s t ra i n t s

42

4. 1 . 3

Asses smen t of O t h e r Techno l o g i es

45

4. 1 . 4

Pos s i b l e F i rst S tage and Second S tage Sen s i ng Techn i qu es

47

4.2.1

E s t i ma tor for O i l S l i c k Thi c kn e s s

52

4.2.2

Behav i our of an Oi l S l i c k Conta i ned Beh i nd a Boom

54

4.2.3

Typ i c a l Boom De s i gns

55

4.2.4

Mec han i c a l Systems for Oi l Remova l

58

4 . 2. 5

I l l u strat i on of Severa l Oi l Recovery Methods

59

&

Study Area Bea ufort Sea

4

- vi i i L I ST O F TABL E S PAGE

TABLE

9

2.2.1

Ti da l Data

4.2.1

Performance Eva l uati o n s - - O i l S p i ll Recovery Dev i ces

71

4. 3 . 1

Eva l u a t i on of Earth-Mov i ng Equ i pme n t to Form W i ndrows and Other Ta s ks

85

4.3.2

Eva l u a t i on of Snowbl owers to S pread Pea t Mos s Over Beac h

86

4.3.3

C l eanup Procedures for Remov i ng Tarry Lumps from Sand Beaches

88

4.3.4

Met hods and E q u i pmen t for C l eanup of San d and Gravel Beaches

88

4.3.5

Eva l u a t i o n o f C l eanu p Techn i ques a n d Equ i pmen t for Beach C l ean i ng

89

4.3.6

Cyc l e T i me for 20-M Ton Tra c ked Gravel Carri er . A s s um i ng 4 - KM H a u l

91

4.3.7

Eva l u a t i on o f Vari o u s Veh i c l es for Earth Mov i ng Dut i e s i n the Arct i c Envi ronme n t

93

4. 3.8

Eva l u a t i on of Tec h n i ques for t h e Di s posa l of O i l ­ Contami nated Beach Materi a l

97

4.3.9

S ummary of C l eanup Tech n i ques that App l y t o S h i n g l e Beaches

1 00

4.3.10

Beaufort Sea Coa s t l i ne - - O n - S hore Protecti on and Cl eanup Matri x

1 05

4.4.1

Ava i l ab i l i ty of Ai rcraft i n the Beau fort S ea Area

1 07

- 1 -

1

I NTRODUCT I O N

A l mo s t t h e who l e o f t h e Cana d i an porti on o f t h e con t i nen ta l s h e l f o f the Beaufort Sea has been s u bject t o permi ts by oi l compan i e s for a number of years and i s reg arded as promi s i n g wi th respect to g a s and oi l res erves . T o d a te t h e on l y dri l l i n g wh i ch has taken p l ace offs hore i n the Beau fort Sea h a s been from a rti f i c i a l i s l ands constructed i n the s h a l l ow water c l ose to the Mac kenzi e Del ta . Some sectors of the i nd u s try a re n ow p l an n i n g expl oratory dri l l i ng from s h i ps i n deeper waters farther offs hore . The purpose of th i s s tudy i s to i n ves ti gate the fea s i b i l i ty of contro l l i ng and c l ea n i n g up of oi l s p i l l s i n the off s h ore Beaufort Sea . Parti cu l a r emph as i s i s p l aced on l a rge s p i l l s that wou l d res u l t from oi l bl owou ts . Of i mmed i ate i n tere s t i s the p roposed Arc t i c opera ti on of the o i l i n dus try for the s ummer of 1 9 76 . P l a n s a re bei ng made to d ri l l two wi l dcat we l l s a t s i tes i n the s o u thern Bea u fort Sea s tarti ng August 1 , 1 976 . One i s l oca ted i n a water depth of 26 meters , 46 k i l ometers s eaward of Tu ktoya ktu k Pen i n s u l a ; the other i s i n a depth of 58 meters , 80 k i l ometers offs hore of Pu l l en I s l a nd . Both these s i tes are s i tuated i n the tra ns i t i on zone wh i ch i n the wi n ter mon ths i s a reg i on of s porad i ca l l y-mov i ng sea i ce be tween the l andfa s t i ce and the conti n u a l ly­ movi ng po l a r pack i ce . I n a l i g h t - i ce year th i s zone i n the s ummer i s re l a ti ve l y i ce- free . I n a bl owo u t s i tuati on , o i l and gas wi l l ri se to open water s u rface to form an o i l s l i c k. As wi n ter s e ts i n and i ce moves over the s i te of the b l owo u t the u pward r i s i ng o i l wi l l move not on l y i n to a reas of open wa ter but a l s o to u nder- i ce s u rfaces . I t i s be l i eved tha t , beca u s e of the s hort d r i l l i ng s e a s on that s h ou l d a b l owou t occur i n t h e s ummer o f 1 9 76 i t wou l d n o t b e pos s i b l e t o d r i l l a rel i ef we l l u n t i l a t l ea s t the s ummer of 1 9 77 , or even l a ter . Thi s s i tuati on wou l d l ead to the d i s charge of a t l ea s t 50 , 000 tons of oi l i n to the Beau fort Sea . Th i s th rea t to the envi ronment wou l d be con s i dera bl e . There a re , however , other poten ti a l oi l s p i l l p rob l ems i n the Arc ti c . The d i s covery of o i l i n the offs hore Arc ti c wi l l l ead to i n tens i ve deve l opmen t i n the Coa s t a l Beau fort Sea and s u rrou nd i ng l and wi th new we l l s , col l ector p i p e l i nes , s torage fa c i l i ti e s , major p i p e l i nes , new harbours , etc . Thi s i n creased human acti v i ty wi l l i ne v i ta b l y i ncrease the pos s i b i l i ty of oi l s pi l l s . I t i s beca u s e of th i s general and l on g - term prob l em i n the North that we have chosen not j u s t to i nvesti gate the prob l em of bl owouts a t one or two s pe c i fi c s i tes i n the Beau fort Sea , but a l s o to l ook a t s evera l repres e n ta ti ve offs hore s p i l l poss i b i l i ti es i n the Arc t i c and a n a l ys e the feas i bi l i ti e s of dea l i ng wi th a l l of the s e . Thus , coun ter­ mea s u res for s p i l l s i n the l an d fa s t i ce zone and the permanent pol ar pac k zone , i n add i t i on to the s hear zone where the o i l i n d u s try i s p ropo s i ng to dri l l i n the s ummer of 1 976 , are con s i dered i n th i s s tudy . Except for the case of open water s i tua ti ons i n the s ummer , the s t a te-of-the-technol ogy for con trol l i ng s p i l l s i n the Arc ti c i s presen t l y i n an embryo n i c s tage . The l ac k of ba s i c knowl edge , expe rti se and tec h n o l ogy i n th i s a rea i s con s i dera b l e , and wi l l be c l earl y evi dent

- 2 to the reader of th i s report . The devel opmen t of s a t i s fac tory coun ter­ meas ures sys tems for o i l s p i l l s i n the Arc ti c wi l l req u i re a l arge- s ca l e techno l o g i c a l effort . Thi s s tu dy , a s a fi rs t s te p , a n a l yses the pre s e n t s ta te of k n owl edge and technol ogy and i denti fi es gaps where work i s req u i red .

- 3 2

B EAU FORT SEA PHYS I CAL ENV I RONMENT .

The present o i l - permi t area i n the s o u thern Beaufort Sea i s s h own on F i gure 2 . 1 . The reg i on i s a n i rreg u l ar- s ha ped pol ygon extend i ng from the en tra nce of the Amu ndsen G u l f and B a n k s I s l and on the e a s t to the Al a s ka - Y u kon border on the wes t . The mo s t norther l y boundary of the area rou g h l y fol l ows the 920 meters bathymetri c c on tour , wh i c h vari e s between 5 0 k i l ometers and 1 30 k i l ometers offs hore . T h e en ti re o i l permi t area encompasses a p prox i ma te l y 1 65 , 00 0 s q uare k i l ometers . 2.1

C l i ma to l ogy. The c l i mate of the permi t area i s not wel l known . Unti l 1 974 , mo s t of the c l imatol ogy parameters had been recorded and meas ured o n l y a l ong t h e c o a s t a n d w i t h i n t h e del ta area of t h e Mac ke n z i e R i ver . Temper­ a ture and prec i p i ta t i on meas urements have been recorded a t Akl a v i k s i nce 1 926 , a t Atk i n son Po i n t s i nce 1 959 , at Cape Parry and I nu v i k s i nce 1 958 , and a t Tu ktoya ktu k s i nce 1 948 ( Anon , 1 97 0 ) . Res ource Expl ora t i on and s h i p- borne res earc h carri ed o u t i n the southern Beaufort Sea duri n g the l a s t few years has produced some meteorol og i ca l d a ta c o l l ected over re l a t i ve l y s hort peri ods of t i me . The fo l l owi ng sect i on s pre s e n t bri ef s ummar i e s of the c l i ma t i c i nforma ti on ava i l ab l e to d a te . 2.1 .1

A i r Tempera tures . The wi n ter tempera tures a l ong the southern coa s t of the Bea ufort Sea have been s ummar i zed by the Canad i a n Department of Publ i c Works ( Anon , 1 97 0 ) . I n the \'I i n ter per i od from January throu g h Apri l , a i r tempera tures i n t h i s reg i on hav 8 reported l y fa l l en bel ow - 3 0 C for 90 perce n t of the days and bel ow -40 C for 33 percent 0 6 the t i me . Mea n month l y tempera ture s 0 i n January vary between - 2 6 C and - 2 9 C a l ong the coa s t . Extre� es of s ummer tempera ture s i n J u l y a nd Aug u s t are reported t s rea c h 6 6 C and the mean mon th l y a i r tempera ture i n J u l y vari es between 6 C and 8 C . No i nforma t i o n i s presentl y avai l a b l e on a i r tempera ture over offs hore areas of the reg i on . However , beca u s e of the d i fferences i n refl ec ti ve c h arac teri s t i c s of wa ter a nd l and a nd the prox i m i ty of the pol ar pac k , the a i r tempera tures i n s ummer wou l d genera l l y be l es s offs hore t h a n over l a nd a n d da i l y tempera ture fl uctuati o n s wou l d be s omewha t smal l er . S i n c e most of the offshore area i s i ce - covered d uri ng wi n ter , the temperatures throughout the s tudy area c a n be expec ted to be about the s ame a s those g i ven for the c oa s t a l areas a t th i s t i me of the year . 0 Wa ter tempera tures i n l ea d s or po1 ynyi wi l l be _2 C duri n g t h e wi n ter mon th s . T h e s ea s urface temperatures i n t h e Beaufort Sea have been s ummar i zed by the U . S . Navy for the s ummer peri od . D i s co n ­ ti nuous record s are ava i l a bl e for the years 1 95 4- 1 9 7 0 ( B urns 6 974 ) . Data i nd i c a te t s a t the mean J u l y sea s urface tempera ture i s 2 C near the coast and 0 C at the northern ext sem i ty of the s tudy are s . S i mi ­ l arl y , for Augu s t , tempera tures are 4 C near the coa s t an a 1 C a t the o northern extremi ty of the s tudy area and for September , 1 C and 0 C , res pecti vel y .

-

STUDY AREA -,

I ( I

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I

I I

I

I f

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o F

0AKI.AVIK 50 L

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FIG

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PERMIT & STUDY AREA BEAUFORT SE � _J _._

- 5 2.1 . 2

W i nd . The average and maxi mum wi n d v e l oci t i es encou n te red i n the Beaufort Sea wi l l i nfl uence the a i r access i b i l i ty of an oi l s p i l l s i te and the performance of men and e q u i pme n t engaged i n c l ea n u p operati ons . The d i rec t i on and i n tens i ty of the w i nd w i l l a l s o have a d i rect beari ng on the types , s tructu res and extent of the i ce i n the s tudy a rea . The average wi nd s peed a t Akl avi k on the Macken zi e Ri ver Del ta i s reported to be 1 0 . 5 ki l ometers per hour . S i m i l ar l y , the mean mon th l y wi n d s peeds determi ned from d a ta c o l l ec ted a l ong the coast are s h own to be re l a ti vely constant throughout the year , averag i ng between 1 1 and 1 8 k i l ometers per hou r . The months of September and October were reported ( Kovacs and Me l l or 1 974 ) to have the h i ghes t wi nds , wi th averages a l ong the coast of 1 9 k i l ometers per hou r . In genera l , areas beyond the Conti ne nta l S he l f reported ve l oc i t i es o f 40% l es s th an coa s t a l areas . The au tumn mon ths a re c ha ra c teri zed by s evere s torm a c ti v i ty . I n 1 97 0 , for exam p l e , one parti c u l ar s torm was reported by Kovacs and Mel l or to have wi nd s peeds averag i ng 1 0 5 k i l ometers per hour wi th g u s t s to 1 40 k i l ometers per hour . Wi nd d i rec ti ons i n the Beaufort Sea reg i on v a ry con s i derab l y wi th the season . Prev a i l i ng wi nds du r i ng the wi n ter a re genera l l y from the n orth and wes t . Duri ng the a u tumn , s torm wi nds from the northwe s t may p u s h the pol a r pack on to t h e Di s tri c t o f Mackenzi e s hore . Duri ng the wi n ter the p o l a r pack i s genera l l y pus hed agai n s t the newly formed l a ndfa s t i ce caus i ng ex ten s i ve r i dg i n g i n the tran s i t i onal and s hear zones . U s u a l l y , i n January , a c e l l of h i g h a tmos pher i c p res s u re mov es acros s the Arc ti c Bas i n caus i ng the preva i l i ng wi nds i n the oi l - permi t a rea to veer to the e a s t and s o u theast by Apri l . Thi s s omet i mes res u l ts i n the forma ti on of a l a rge l ead or p o l ynya north of Cape Bathu r s t , wh i ch may ex tend 240 k i l ometers offs hore a l ong the wes t coa s t of Ban ks I s l and , and ex ten s i ve l eads para l l e l wi th the s hore i n s i de th e s h ear zone . 2.1 .3

Day- n i g h t reg i mes . From May throug h to e a r l y Aug u s t the Beau fort Sea reg i on experi ences day l i g ht or twi l i g h t throu ghout the e n ti re 24- hour day . Conversel y , from mi d - November u n t i l the end of January , vi rtu a l l y 24- hour darknes s preva i l s . 2.1 .4

Prec i pi tati on . L i t t l e l on g - term p rec i p i ta t i on data have been col l ected for the Beaufort Sea area es peci a l l y i n offs h ore reg i ons . Some i nforma ti on h owever , has been p u b l i s hed ( B u rns ) on prec i p i tati on d a ta for the peri od 1 941 - 1 970 . The mean annu a l preci p i ­ ta ti on for the a rea i s reported to be l es s than 1 3 centi meters wi th a coeffi c i e n t of vari a ti on of a l mo s t 50 percen t . The a n n u a l s n owfa l l a l ong the coa s t i s reported to average 64 centi meters . New s n ow i s genera l l y heavy i n wa ter conte n t h av i ng a dens i ty of 0 . 2 gm/cc , about twi ce as h i g h a s i n other areas of North Amer i ca . The mean n umber of days wi th mea s u ra b l e preci p i tati on ( 0 . 25 mi l l i meter ) i s reported ( B u rns ) to be 60 a l ong the coa s t and 30 a l on g t h e northern ex tremi ty of the s tudy area . The mean number o f days o f mea s u red s n owfa l l i s 30 a l ong t h e coas t ; there h a v e been no data reported fo r offs hore reg i on s .

- 6 -

2.2

Oceanography . The s a l i en t oceanograp h i c pa rameters i n the s ou thern Beaufort Sea a re s u rface currents , ti des , s torm s u rges and water tempera tures . Very l i tt l e i s known about s ome of these pa rameters ( Kovacs and Mel l o r 1 974 ) , and what i s known i s i n s ome cases con trad i c tory . A bri ef descri pti on of the s ta te of knowl edge i s g i ven bel ow . 2.2.1

C u rren ts . The wa ter c u rren ts n orth of the con ti nenta l s he l f i n the s o u thern Beaufort Sea f l ow wes tward wi th the c l ockwi s e moti on of the Beaufort Gyre . The i r s u rface ve l oc i ti es have been reported to vary between 0 . 04 and 0 . 1 knot ( Anon , 1 970 ) . Other i nves t i g a ti ons reported resu l ts i nd i cati ng s u rface ve l oc i ti es i n the order of 0 . 5 knot ( H na t i u k , pers onal c ommu n i cati on , 1 9 74 ) and the U . S . N avy Hydrog raph i c Offi ce have reported average va l u e s of 0 . 06 knot ( B urns 1 974 ) . On the con t i nen t a l s he l f , the s u rface c urrents a re more va r i ed and l es s pred i ctabl e than i n offs hore area s . There i s a we s tward s u rface fl ow a l ong the Y u kon-A l a s k a s hore s tarti ng i n the Mac kenzi e Ri ver Del ta . East of the del ta the fl ow i s i n to the Amu ndsen Gul f . However , duri ng J u l y a l arge porti on of c u rren t moves northward i n to the Beaufort Gyre . Duri ng the s ummer of 1 974 open water s u rface cu rren ts were mea s u red i n the s tudy area as part of one of the fi e l d prog rams of the Beaufort Sea p roject ( MacNei l l ahd Garrett 1 9 76 ) . Obs erva ti ons tended to be s ca tte red but s uggested two d i s ti n c t c i rc u l a t i on patterns under two d i fferen t wi n d condi ti ons . Northwe s t wi nds tended to p i l e up water a l ong the De l ta , i n to Kugma l l i t B ay and up a l ong the Tuktoya ktuk Peni n s u l a . S trong , s teady easterly wi nds c a u sed a wes ter l y cu rrent to fl ow nex t to the s hore wi th water movemen t at q u i te h i gh s peeds ( 0 . 05 to 1 . 0 knot ) to the northwe s t offs h ore . The s peed of the c u rrent was reported to i n crease to the north . F i g u res 2 . 2 . 1 and 2 . 2 . 2 s how the e s t i ma ted a pprox i ma te c i rcu l a t i on pattern d u r i ng s t eady e a s t and northwe s t wi nds , respecti v e l y , as i nd i cated by MacNei l l and Garrett . Curren t s peeds are not s hown . Ti des . Permanent t i de g auge s ta t i ons have been i n opera t i on a t Tuktoya ktuk s i nce 1 9 58 , Cape Parry s i nce 1 96 6 , and Sachs Harbou r s i n c e 1 97 1 . I nterru pti on s ex i s t i n t h e water l ev e l record s from e a c h of these s tati o n s , and the Tu k toya ktuk gauge has twi ce been moved to new s i tes . Obs e rved water l evel s are referen ced to bench marks a t each stati on . Land i n s ta b i l i ty and change of s ta t i on s i te l i mi t the rel i ab i l i ty of l ong term reference e l eva ti ons , b u t do not affect the knowl edge of ti d a l c ha ra c teri s t i c s . Pri or to the B ea u fort Sea Proje c t , n i n e temporary ti de gauge s ta t i ons were occu p i ed i n Es k i mo Lakes and v i c i n i ty duri ng a ti d a l s u rvey i n J u l y-Augu s t 1 97 1 . Seven s ta t i on s were occu p i ed i n L i v erpool Bay and v i c i n i ty du r i ng a s i mi l a r s u rvey i n 1 97 2 . Ti d a l obs erva ti o n s h a v e a l s o been obta i n ed a t Atk i n s o n Poi n t , i n conju n c ti on wi th hydro­ graph i c charti ng i n the Beaufort Sea . The Canad i a n Departmen t of P ub l i c Works meas u red ti d a l s tati s t i c s f o r one month a t three l oc a ti o n s a l ong t h e sou thern B eaufort Sea i n a s s oc i a t i on wi th a feas i b i l i ty s tudy for a ma ri ne termi n a l . 2.2.2

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- 46 I n the l onger term , there a re theoreti c a l reasons for bel i ev i ng that acou s ti c a l or res i s t i v i ty tech n i ques , whi ch are c u rren t l y u s ed for geophys i ca l purposes , may s how promi s e for detec t i ng o i l under i ce . Sys tems for Oi l Spi l l S u rvei l l ance and Mon � tor i n g . . Two s tages of sys tem devel o pment for s u rvell l ance and mom ton ng are c on s i dered . The fi rs t - s tage sys tems on l y i n c l ude e q u i pment wh i ch i s read i l y avai l abl e . The s econd s tage i nc orporates i mp rovements to fi r s t­ s tage sys tems where i n each case s ome l evel of dev e l opmen ta l effort wou l d be nece s s a ry . S ome changes wou l d req u i re on l y f i el d tes t i n g , other changes wou l d requ i re a s i g n i fi cant research and deve l opment effort , and s t i l l others wou l d benefi t from on l y a prel i m i n a ry tech n i c a l a s s es smen t . Some o f the remote s en s i ng equ i pmen t cons idered for a p p l i cati on i n the Beaufort Sea req u i res l arge a i rcraft for depl oymen t because of s i ze , we i gh t or p ower con s tra i n ts ; whi l e other devi ces may be mou n ted on l i g h t a i rcraft . Because of the d i fferences i n c os t and a i rcraft ava i l ­ a bi l i ty between thes e l a tter two a l terna t i ves , remote sens i ng pac kages fa l l i nto two groups : heavy and l i g h t . Furthe r , the devi ces or methods wh i ch c ompri s e pos s i b l e remote s en s i ng sys tems a re , i n s ome cases , separated i n to two groups , where primary devi ces or methods a re the mos t i mporta n t el ements of the remote s ens i ng sys tems , whi l e s econdary devi ces o r methods p rov i de on l y s u pp l e ­ mentary i nforma t i on . A s ummary of pos s i bl e tech n i ques for i ncorporati on i nt o sys tems for u nderta k i ng the s u rvei l l ance and mon i tori n g ro l e i n th� s hort and l ong terms i s presen ted i n F i g u re 4 . 1 . 4 . 4.1 .4.1 F i rs t S tage Survei l l a n ce Sys tems For s u rve i l l ance duri n g the freeze-up and brea k - u p peri ods , T I RLS and L 3TV , opera ted from a l i g h t a i rcraft , cou l d be u s ed i n a reas of open w a te r . These devi ces cou l d b e opera ted over any of the three i ce zones . The sys tem wou l d not have a l l -weather capab i l i ty , b u t the condi t i on tha t , i n s trumen ts mus t be ava i l ab l e " off- thes he l f " prec l udes the add i t i on of a ny m i crowave devi ces to the fi r s t- s tage sys tem . W i t h the onset of a l mo s t compl ete i ce cover , these s ensors wou l d on l y operate over i ce open i ng s s u c h as l eads and pol yny i . Because of the l ow probabi l i ty of VFR cond i t i ons d u r i n g th i s per i od , the add i t i on of a S LAR dev i ce wou l d be des i ra b l e to prov i de s ome a l l -weather capabi l i ty to detec t o i l i n l arge l eads or p o l yny i ; thereby u pg rad i ng the sys tem to a " heavy " remote s en s i ng package . Neverthe l es s , the opera t i on of remote s en s i ng i n s truments wou l d be s evere l y l i m i ted d u r i ng the peri od of v i rtua l l y tota l i ce c over . Duri ng th i s per i od , the manua l tech n i q u e of i ce cor i ng wou l d l i ke l y be the pri mary o i l detecti on sys tem . Crews c ou l d be d i s pa tched to the s i te , or s i tes , a t reg u l ar i n terva l s to remove i ce c ores a n d check for o i l . The c ori n g pattern cou l d b e establ i s hed a s a res u l t of an a n a l ys i s o f expec ted o i l - p l ume chara c ter i s t i c s , c u rrents , and u nders i de profi l e of the i ce . I n open water i n the Beaufort Sea , the pri mary s u rvei l l ance ro l e wou l d be f i l l ed by the c rew on the dri l l i n g s h i p . Occa s i on a l fl i g hts u s i ng S LAR , o r a remote s en s i ng package from a l i g h t 4.1 .4

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- 48 -

a i rcraft ( T I RLS and L 3TV ) cou l d prov i de add i ti ona l or secondary s u rvei l l an c e coverage . Second S tage Survei l l a n ce Sys tems 4.1 .4.2 A poss i b l e l ong term s urvei l l ance sys tem cou l d i n corp o rate a l i g h t we i gh t remote s en s i ng pac kage con s i dered for s u rvei l l an c e i n the s hort term , b u t wi th a FL I R rep l ac i ng the TI RLS . and a ugmen ted by a M I R . Th i s wou l d i ncrea s e the a l l -weather capabi l i ty of the sys tem . As a second pri ori ty , on- i ce acou s t i c a l or resi s ti v i ty techn i ques c ou l d be exami ned for poss i b l e a p p l i cati on i n the trans i t i on and p o l ar-pacK zones . 4. 1 .4.3 F i rs t S tage Mon i tori ng A primary sys tem for a l l cond i ti ons except 9/ 1 0 - 1 0/ 1 0 i ce c over c ou l d i nc orpora te a T I RLS and L 3TV i n a l i g h t a i rcraft . Add i ti on of a S LAR wou l d p rov i de s ome a l l -weath er , open-water o i l detec ti on capabi l i ty , b u t wou l d nece s s i tate the depl oyment of a 1 a rge a i rcraft . For exten s i ve i ce cover i n the l andfa s t- i ce zone , a prog ram of i ce- core s amp l i ng i s the onl y v i a b l e method . Gas ana l yzers c ou l d be i n troduced to s u pport and pos s i b l y d i rec t the cori ng program . The effec ti venes s of g a s a n a l yzers i n the trans i t i on or po l a r pack zones rema i n s unknown . Radar trans ponders or rad i o beacons dep l oyed on the mov i ng i ce over the dri l l s i te wou l d as s i s t i n the tra c k i ng of o i l contam i na t i on by i nferen ce . 4. 1 .4.4 Second S tage Moni tor i ng A s i g n i fi cant p roporti on of a ny c l eanup operati on cou l d take p l ace d u r i ng the open water s ea s on , s o a capabi l i ty to moni tor o i l movement at t h i s t i me i s des i rabl e . For examp l e , a heavy­ we i g h t sys tem i ncorpora t i ng a t l ea s t a SLAR , M I R and FL I R cou l d prov i de a n overv i ew of the a rea and a c t a s a primary tra c k i ng sys tem . A l i gh ter package , perhaps i nc orpora t i ng a F L I R , L 3TV and M I R , i de a l l y mou n ted i n a h e l i copter , cou l d p rov i de more l oc a l i nforma ti on to c l ean- u p c rews . The heavy sys tem c ou l d be emp l oyed for mos t of the year throu g ho u t the v a ri ous i ce zones and p rov i de s ome capabi l i ty to dete c t oi l i n l arge l eads or p o l ynyi . Agai n , radar trans ponders or rad i o beacons c ou l d a c t as foc i for trac k i ng the oi l i n the tran s i t i on and p o l a r pack zones d u r i ng the wi nter . Pos s i b l y , on - i ce acous t i cal or res i s t i v i ty tech n i ques cou l d be u t i l i zed to l oc a te more accurate l y t h e extent o f o i l contami nati on wi t h i n and u nder i ce . A pri mary sys tem i n the l andfa s t i ce zone c ou l d u ti l i ze a M I R opera t i ng between 400 to 2000 MH z wh i ch mi g h t be deve l oped to g enerate i nforma ti on about the d i s tri b u t i on of o i l under the i ce . As a s econd pri ori ty , th i s dev i ce cou l d be repl a ced or s u pported by . an i mpul s e rada r operat ing from 1 00 MHz to 1 GH z . 4.1 .4.5 Remote Sens i ng P l a tforms C l earl y , not a l l the e l ements of a s u rvei l l ance and moni tor i ng sys tem a re req u i red on a c on ti nu ou s ba s i s : some may be req u i red peri od i ca l ly , and others on l y on an emergency ba s i s . For examp l e , beca u s e of the h i g h cos t and heavy a i rcra ft req u i remen ts

- 49 of S LAR , i t wou l d be i mpracti c a l to con s i der a dedi ca ted sys tem for th i s rol e . Ai rcraft from the Department of Na ti onal Defence eq u i p ped wi th SLAR c ou l d be tas ked i n the Beaufort Sea . At p resen t , DND i s fl i g h t tes ti ng a SLAR aboard a n Arg u s a i rcraft , and has g i ven seri ous c on s i dera t i on to c i v i l i an ta s k i ng of the new l on g ­ range p a trol a i rcraft ( LRPA ) . The LRPA wou l d not req u i re a i rstri p s adjacent t o t h e Beaufort Sea . The Department of the Env i ronmen t a l s o i s ex pected to acqu i re a SLAR i n the near future , mou n ted on a Loc k heed E l ectra . The E l e ctra , wi th a payl oad of 1 2 ,000 kg , req u i res a ru nway of at l ea s t 1 , 500 m for ta keoff . Ru nways capa b l e of h a nd l i ng the E l ectra exi s t at I nu v i k and Cape Parry . I n s umma ry , then , for the rol es i n whi c h a SLAR i s c on s i dered effec ti ve ( es senti a l l y the open water cas e ) , a heavy a i rcraft wou l d be depl oyed , augmented by other s u i ta b l e s e n s ors . L i g h ter i ns trumen ts may be dep l oyed i n l i g h ter a i rcraft s uc h a s the C47 ( Da ko ta ) and Fa l con ( opera ted by the Canada Cen tre for Remote Sen s i ng , CCRS ) . The Dakota carri es , among other s en s ors , TI RLS and L 3TV . Th i s a i rcraft cou l d be tas ked wi th the ro l es s u i ta b l e for these i n s truments . The F a l con i s e q u i p ped wi th a TI RLS , but not wi th L 3TV . The Fal con i s prefera b l e to the Dakota beca u s e of i ts h i g he r s peed and , therefore , better f l i gh t ti me to the ta s k . Both of these a i rcraft c ou l d operate from the a i rstri p a t I nu v i k . 4. 1 . 5

Conc l u s i ons It i s c o n c l uded that conven ti onal a i rborne remote s en s i ng provi des v i rtua l ly n o capabi l i ty for o i l s p i l l s urvei l l ance and mon i tori ng duri ng the i ce- covered parts of the year i n the B eaufort S ea . A l though i t i s l i k e l y that an a i rborne mul ti - s en s or sys tem wou l d exh i b i t s ome effecti venes s duri ng the s hort open -wa ter peri od , and perhaps even the peri od wi th l i mi ted i ce- cover , to d a te none of the dev i ces wh i ch mi g h t b e i nc l uded i n s u c h a sys tem have been tes ted t o detect o i l i n the a rea . Some of the devi ces a re c u rren t l y mou n ted on a i rcraft i n Canada , b u t not i n the o p t i mum confi gura t i on for the pre s e n t purpos e . To produce a c u s t om-des i g ned a i rborne sys tem , u s i ng " s ta te-of-the- a r t " equ i pmen t , wou l d take a n e s t i ma ted 2 years and c o s t more than $ 1 , 00 0 , 00 0 i n equi pmen t a l one . Radar trans ponders or rad i o beacons may be depl oyed to tra c k mov i ng i ce contami n a ted b y oi l u s i ng rece i vers mou n ted i n a i rcraft or s a te l l i te s . Gas a n l ysers to detect o i l fumes through fl aws i n the i ce s h eet , and tri a l and error i ce penetra t i on u s i ng i ce aug ers cou l d be u s ed on - s i te to l oc a te o i l trapped u nder or w i th i n the i ce s h eet . Res i s t i v i ty and acous ti ca l dev i ces s i m i l ar to thos e u s ed i n geophy s i c a l s u rvey i ng , and VHF pu l s e radar equ i pment devel oped for meas u r i ng i ce th i c knes s , theoret i c a l l y cou l d a l so p rov ide l oca l i sed detec ti on capabi l i t i es .

- 50 4.2

O i l Con ta i nmen t and Remova l When the u pward r i s i ng o i l a n d g a s p l ume from an expl oratory o i l we l l b l owo u t arri ves a t the water s u rface and es capes from the wave r i ng , i t i s s u bj e c ted to the s ame envi ronme n ta l i nfl uences a s a ny other o i l s p i l l rega rd l e s s of the s ource of the s pi l l . In chapter 3 . 0 , fi ve envi ronmental cond i t i ons ( open wate r , i ce i nfes ted , f a s t i ce , s ea s ona l pack i ce and pol ar p a c k i ce ) were i den t i fi ed and the p os s i b l e behav i o u r of oi l i n each cond i ti on des cri bed . T h e contai nme n t and remova l opera ti ons wou l d have to be tai l ored to each of those f i ve cond i ti ons . A b l owou t i n the s ummer wou l d resu l t i n o i l o n water i n a s i tua ti on s i mi l ar to o i l s pi l l s i n more tempera te reg i ons . I n res pon s e to th i s s pi l l , a t tempts wou l d be made to depl oy conven t i onal open wa ter contai nmen t a n d remo v a l devi ces . Open Water The f i rs t obs ervab l e fea ture after o i l h a s es caped from the wave r i ng wou l d be i ts tendency to s pread on the water s u rface . On c l ean s ea wa ter u n i nfl u en ced by wi n d , waves or c u rrents , o i l wi l l s pread i n to a c i rc u l ar s l i c k q u i te q u i c k l y . For examp l e , 1 00 0 m 3 of an average c rude wi l l s pread i n to a s l i c k of 600 m i n d i ameter wi th an average t h i c kn e s s of about 3 . 5 mm wi t h i n one h ou r . Genera l l y � the s pread i n g rate o f o i l o n wa ter i s governed by the effects of g rav i ty � s u rface ten s i on a n d v i s c os i ty . The s pread i n g i s a i ded by s u rfactants wh i ch many o i l s conta i n . The moveme n t of the o i l i s c a u s ed by the res u l tan t of the gravi tati o n a l force and the vari ous i nterfa c i a l ten s i o n s ; genera l l y � the i n terfac i a l ten s i ons a c t to enhance s pread i ng . As the s l i ck s preads a nd t h i n s , the g rav i ta t i o n a l force l es s e n s . H owever , the tendency to s p read d u e to s u rface tens i on d i fferenti a l s does n o t depend on s l i ck t h i c kn es s , a s does grav i ty , s o s u rface ten s i on wi l l p reva i l a s the s pread i ng forc e . The forces tend i ng to i nh i b i t s prea d i ng a re those a s soci a ted w i th v i s cos i ty and i nerti a . The i n terfaci a l ten s i on s a re q u i te s trong func t i ons of tempera tu re a n d there i s s ome evi dence that the d i recti on of the res u l tan t force at the s l i c k edges may be s u c h to i nh i bi t the s prea d i ng of o i l at l ow wa ter tempera tures . Th i s pos s i b i l i ty d epends u pon the parti c u l a r crude o i l i nvol ved , and c ou l d occur a s certa i n o i l s wea ther a n d the i r chemi c a l compos i ti ons a l te r , thereby c h a ng i ng the mag n i tude of the o i l i n terfaci a l ten s i on s . The actual s preadi ng of o i l does not a l ways fol l ow the genera l pa ttern , and i t i s p os s i b l e that a more v i s cous water- i n - o i l emu l s i on may form . Recen t work s uggests that t h i s emu l s i on ( often c a l l ed ' chocol a te mou s s e ' ) i s on l y formed when there i s s u ff i c i e n t wave moti on , when the o i l i s of a parti cu l ar type and when the s l i ck i s t h i c k . The c hance of s u c h a n emu l s i on bei n g formed i s g re a tes t wi th crude o i l s that d o not s o l i d i fy a fter s ome weather i n g . I t wou l d appear tha t i n a concen tra ted s p i l l , o i l at the cen tre of the s p i l l wou l d rema i n i n a rel ati v e l y th i ck l ayer l on g enough for the a g i ta t i on by wave moti on to p roduce a water­ i n - o i l emu l s i on . Th i s wou l d resu l t i n a rap i d i ncrea s e i n v i s c os i ty and a red u c ti on i n the s pread i ng r a te . Oi l i n t h i s state i s l i ke l y to be b roken up by the wi n d and waves i n to l arge i s l ands and wi n d rows separated by o i l - free wa te r . Sprea d i ng i s a l s o s e l f-retard i ng because the i ncreased a re a wi l l e n h a n c e evapora t i on caus i ng a further i ncrease i n vi s cos i ty . 4. 2 . 1

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I f the pou r - p o i n t i s , or becomes h i gher th an the water tempera ture , s pread i ng wi l l be h i ndered . The t h i c k n e s s of a rel a t i vely th i n o i l l ayer can be j udged a pprox i ma te l y from the c o l our and a ppearance of the s l i c k , deta i l s of wh i ch are set out i n F i g u re 4 . 2 . 1 . Waves do not contri b u te s i gn i f i ca n t l y to the s pread i ng of a s l i c k , bu t rather reduce the s pread i ng rate by crea t i n g an emu l s i on , as noted a bove . The movemen t of a th i n l ayer of o i l i s , i n open wa ter , l argely affected by the wi n d . The exac t dependence i s u n known bu t the s peed of moveme n t i s between 3 to 4 percen t of the wi nd s peed ( say 1 / 30 ) i n the d i rec t i on of the wi n d . The s l i ck movemen t i n the Northern H emi s ph e re i s s l i g h t l y to the r i g h t of the wi n d d i recti on . I n the a b sence of wi n d , o i l on the s u rface i s moved , together wi th the water by c u rren ts . I t wi l l be apprec i a ted that accura te pred i c t i on of the behav i ou r a n d movement of a n o i l s l i ck i s n o t easy . W h i l e ti d a l c u rren ts a re g i ven on hydrogra ph i c c h a rts , res i du a l c u rrents are not u s ua l l y avai l ab l e . Al s o , wi n d v e l oc i ti es are u s ua l l y on l y mea s u red at a few s ta t i ons , wh i ch may be fa r away from the o i l s l i ck . L oc a l wi nds may d i ffer from those mea s u red and pred i c ted . Neverthe l e s s , to fac i l i tate the p l ann i ng of countermeas u res , the best d a ta a v a i l ab l e wou l d have to be u s ed to e s ti ma te the moveme n t of an o i l s l i ck . O i l Con ta i nment i n Open W a ter Once o i l e s capes from the wave ri ng , the mos t p os i ti ve a pp roach to p rotect the envi ronme n t i s to a ttempt to l i m i t i ts s preadi ng . To l i mi t the s pread i ng of o i l , retenti on barri e rs or o i l booms have been deve l oped . An o i l c on ta i nme n t boom i s s u pposed to be capab l e of : reta i n i ng o i l s l i c ks and preven t i n g further movemen t ; concen trati ng o i l s l i c ks s o a s to i ncrease thei r th i c knes s ; a c t i ng as a dev i ce to move o i l across the s urface of the water from poi n t to poi n t ; a nd serv i ng a s a d i vers i onary or prote cti on barri e r to keep o i l ou t of an a rea . I n a l mo s t a l l cases there i s a reg retta b l e tendency to overrate these capabi l i t i es rather than u nderra te them . The mos t s a t i s fa ctory way of dea l i ng wi th a n o i l s p i l l i s to con ta i n the oi l a n d then p hys i ca l l y remov e i t a s rap i d l y a s pos s i b l e . The freq uent fa i l u re of the contai nmen t sys tem g re a t l y comp l i cates the phys i ca l remova l effort . When a barr i er i s p l aced i n t h e p a th of an o i l s l i ck , the s pread i ng effect i s mod i fi ed a n d a pool of o i l , genera l l y much deeper than that wh i ch wou l d res u l t from a n u nd i s tu rbed s l i c k , i s formed . The boom ' s performance i s a ffec ted by wi n d , waves , currents and f l oati ng i ce i n the case of a n orthern envi ronmen t . I t mu s t be capa b l e of conform i ng to the wave p rofi l e s o a s to mai n ta i n i ts freeboard and have s u ffi c i e n t s tructural s trength to wi t h s tand the s tresses s et up by wave and wi n d acti on . Suffi c i e n t verti c a l s ta b i l i ty i s req u i red to overcome the r o l l - effect forces set u p by the water current on the keel a n d wi n d on the s a i l to keep the boom from be i ng fl a ttened onto the water s u rfac e . Freeboard ( sa i l ) mus t be" a d eq u a te t o prevent o i l from bei ng carri ed over the top o f the boom by w i n d a c ti on and c h oppy wave moti o n s . 4.2. 1 . 1

- 52 -

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- 53 -

Al though water c u rren ts a re the u s u a l reason for boom fa i l u re , w i n d and wave acti on a re i mporta n t i n boom des i g n . W i n d i s often the control l i ng fa c tor i n mov i ng a s l i c k a bo u t o n the s u rface of the wate r , and wave moti on often con tri b u tes to brea ki ng up a n i n teg ral s l i ck i n to many sma l l er patches . The rel a t i ve c u rren t , the resu l ta n t of that genera ted by the water curren t i n the a rea , and the moti on of the boom i ts e l f , however , wi l l often be the con trol l i ng fac tor i n boom fa i l u re . Boom fa i l ure i s defi ned a s a l os s of i ts c a pab i l i ty to reta i n the o i l s l i c k . Exper imental work has s hown that an o i l s l i c k bei n g conta i ned by a mech a n i cal barri e r wi l l exhi b i t a s h ape l i ke tha t s h own i n F i g u re 4 . 2 . 2 . I n i ti a l fa i l u re wi l l occur when o i l d rop l e ts b rea k away from the l ee s i de of the head wave . After a cri ti c a l ve l oc i ty ( v ) c i s exceeded , o i l dropl ets wi l l be entra i ned i n the fl owi ng water s tream . U n l es s the drop l ets have s uffi c i en t t i me to ri s e through the wa ter and rej oi n the s l i ck i n Reg i on s 1 or 2 , they wi l l be swe p t u nder the barri er . Reg i on 1 i s the cri ti c a l area for defi n i n g the l i m i ts for o i l b rea kway . The type of c onfi g u ra t i on whi ch the o i l mas s a s s umes i n th i s reg i on i s s i mi l a r to a g ra v i ty wave . For c r i ti c a l cond i ti ons v c wi l l equa l 2 1 . 3 cm per second . B e l ow th i s vel o c i ty n o d rop l ets wi l l be r e l eased from the head wave . Exceed i ng th i s v e l oci ty does not neces s ari l y mean tha t o i l wi l l be l os t u nder the barri e r . I t may be re-depos i ted on the s l i c k i n Reg i ons 2 or 3 . There wi l l be c i rc u l a ti on and d rag phenomena work i ng i n Reg i on 2 a s we l l a s the genera t i on of waves a t the o i l -wa ter i n terface . The s e wi l l affe c t the l ocati on of the poi n t of reattachmen t . I n Reg i on 3 wh i ch runs from the boom to a poi n t equa l to approx i ma te l y f i v e t i mes the boom s k i rt depth , any o i l d rop l et enteri ng the water s tream wi l l be swept u nder the boom . Booms a l s o fa i l when waves s p l a s h over the freeboard . Labora tory experiments have s hown th a t s p 1 a s hover wi l l occur i f the wave s teepne s s rati o i s g re a ter than 0 . 08 and the waves are h i g her than the freeboard . The s teepness ra ti o i s defi ned as wave hei g h t to w a v e l en g th . I f the wave acti on c omb i n e s wi th cu rren t or towi ng , s p 1 a s hover wi l l occur i f the s teepness ra t i o i s l es s than 0 . 08. The thought s hou l d be kept i n m i n d that a mechan i ca l barri er does n o t have t o rema i n s ta t i onary . The rel a t i ve ve l oc i ty profi l e c a n be c hanged by a l l owi ng the barri er to d r i ft wi th the o i l mas s . The fa i l u re mecha n i sm c a n a l s o be mod i f i ed by i ns t i tuti ng s k i mmi ng acti on a s s oon a s pos s i b l e a fter the s l i c k i s boomed . Qui te often , h owever , the amo u n t of s k i mmi ng capabi l i ty avai l ab l e wi l l n o t be adeq u a te to preven t fai l u re . Nei ther anchored nor free fl oa t i n g booms of any type s o f a r d es i g ned h a v e a ny c h a n c e of conta i n i ng s p i l l ed oi l u nder the w i nd and wave cond i ti on s norma l l y encou n tered i n open sea cond i ti on s . There a re occa s i on s of near fl a t- c a l m c on d i ti on s when a n c hored or free fl oati ng booms can p l ay a rol e . However , to be of any va l u e i n a n offs hore s i tu a t i on , booms of adequ a te freeboard s hou l d be emp l oyed . The types of contai nme n t booms avai l ab l e may be gen eral l y categori zed i n to th ree des i g n s . The genera l chara c teri s t i cs of the s e des i g n s a re s h own i n F i g ure 4 . 2 . 3

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