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UBC Theses and Dissertations

Dispersal of recent sediments and mine tailing in a shallow-silled fjord, Rupert Inlet, British Columbia Johnson, Ronald Dwight 1974

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DISPERSAL OF RECENT SEDIMENTS AND MINE TAILING IN A SHALLOW-SILLED FJORD, RUPERT INLET, BRITISH COLUMBIA by RONALD DWIGHT JOHNSON B.A. (Hons) University of B r i t i s h Columbia, 1952 M.Sc. University of B r i t i s h Columbia, 1956 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Geological Sciences We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June, 1974 In p r e s e n t i n g t h i s t h e s i s i n partial f u l f i l m e n t o f t h e requirements f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h Columbia, I agree that t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s thesis f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t copying or publication of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, C a n a d a D a t e <7su£j /£ i ABSTRACT" Rupert I n l e t ( f jord) i s the s i t e of l a r g e - s c a l e sub-marine d i s p o s a l of mine t a i l i n g and waste rock. This t h e s i s considers the p r e - o p e r a t i o n a l c o n d i t i o n and the i n i t i a l two years of o p e r a t i o n . R e p e t i t i v e seismic surveys, g r a i n s i z e a n a l y s i s from cores and samples, bottom curre n t measurements together w i t h g e o l o g i c , topographic and oceanographic c o n s i d e r a t i o n s are used to e s t a b l i s h the n a t u r a l e r o s i o n a l - d e p o s i t i o n a l p a t t e r n and i t s e f f e c t on t a i l i n g d i s t r i b u t i o n . Connection of Quatsino Sound to the Holberg-Rupert bas i n v i a Quatsino Narrows i s a p o s t - g l a c i a l feature which i n i t i -ated the present sedimentation regime. P r i o r d e p o s i t s , f l a t -l y i n g clayey s i l t , were eroded by bottom currents o r i g i n a t i n g at the Narrows, moved up i n l e t then re-deposited, g e n e r a l l y i n Hol-berg I n l e t above Coal Harbour and i n Rupert I n l e t o f f the pre-sent Mine s i t e . Bottom currents r e s u l t from the i n c u r s i o n of f l o o d t i d e water through Quatsino Narrows i n t o the ba s i n . Density d i c t a t e s the i n t r u s i o n l e v e l i n t o the indigenous water column, w h i l e t i d e height and range c o n t r i b u t e to the v e l o c i t y of r e s u l t i n g c u r r e n t s . Water above the i n t r u s i o n l e v e l moves headward, while water below th a t l e v e l forms counter-currents i n Rupert and Holberg i n l e t s which are convergent below the Narrows. Release of pressures b u i l t up during f l o o d t i d e causes strong u p - i n l e t bottom currents on e a r l y ebb t i d e . Maximum bottom currents are t h e o r i z e d as oc c u r r i n g when the f l o o d t i d e water i s denser than a l l the basin water. Currents are more p e r s i s t e n t up i n l e t , but both up and down i n l e t commonly exceed 50 cm/sec and occas iona l ly 100 cm/sec The t h e o r e t i c a l maximum u p - i n l e t current may approach 300 cm/sec Sediment gra in s ize and sort ing indicate that maximum currents below the Quatsino Narrows extend more strongly up Rupert I n l e t . While t a i l i n g deposi t ion i s widespread throughout the basin and occas iona l ly observed being entrained out Quatsino Narrows on ebb t i d e , greater than 90% i s r e s t r i c t e d to Rupert In l e t . Below the o u t f a l l pipe t a i l i n g have caused s l ides dam-ming the bottom of the i n l e t and use fu l ly ponding t a i l i n g . T a i l -ing are at uniform grade from the fan to Quatsino Narrows, with maximum winnowing by currents i n the lower reach. Natural sedimentation attempts to confine the t a i l i n g to Rupert In l e t . This des ired e f fec t i s thwarted by too much f ine t a i l i n g being allowed to enter the water column. Further study of current s tructure of the water column and of density r e l a t i o n s h i p on e i ther side of the s i l l i s necessary. Modi f i ca -t i o n of engineering design may accomplish lower t u r b i d i t y l eve l s The monitoring program has provided the type of m u l t i -d i s c i p l i n a r y data required for environmental evaluat ion of i n -l e t s . i i i TABLE OF CONTENTS PAGE ABSTRACT i TABLE OF CONTENTS i i i LIST OF TABLES V LIST OF FIGURES -"vi ACKNOWLEDGMENTS x CHAPTER I INTRODUCTION 1 II PHYSICAL SETTING 7 Topography 7 Geology 11 P r e c i p i t a t i o n and Drainage 14 Oceanography 16 III BOTTOM CURRENT STUDIES 2 4 Instrumentation and Operation 25 Current Observations 30 Runs 1, 2 and 3 33 Runs 4 and 5 38 Runs 6 and 7 42 Runs 8 and 9 52 Runs 10 and 11 62 Observations of Other Workers 72 Discussion 76 IV SEISMIC SURVEYS 84 Procedure 84 Interpretat ion and Discussion 86 i v CHAPTER PAGE V SEDIMENTS 106 Cores and Samples 110 Laboratory 113 Interpretat ion 116 Unit B 117 Unit A 120 D i s t r i b u t i o n of Sand, S i l t and Clay 123 Mean Grain Size and Sort ing 133 T a i l i n g 136 D i s t r i b u t i o n and Structure 139 Mean Grain Size and Sort ing 147 Tracer Study 154 T u r b i d i t y 155 T a i l i n g Studies 156 Monitoring Program 158 Surface Observations 164 Summary 166 VI CONCLUSIONS 170 BIBLIOGPAPHY 177 V LIST OF TABLES TABLE PAGE I : DATA FOR CURRENT METER RUNS 31 I I : GRAIN SIZE DATA FOR UNIT B 119 I I I : GRAIN SIZE DATA FOR SELECTED UNIT A CORES FOR COMPARISON WITH TOP OF UNIT A 121 IV: GRAIN SIZE DATA FOR TOP OF UNIT A FROM ADDITIONAL CORES AND SAMPLES 122 V: GRAIN SIZE DATA FOR TAILING SEDIMENTATION 141 v i LIST OF FIGURES FIGURE PAGE 1. Index Map 3 2. Project Base Map 9 3. Index Map of Oceanographic Stations B and D 17 4. Monthly Values of Temperature, S a l i n i t y and Dissolved Oxygen Content at Stat ion B i n Holberg In le t 18 5. Monthly Values of Temperature, S a l i n i t y and Dissolved Oxygen Content at Stat ion D i n Quatsino Sound 19 6. Locat ion Map of Current Meter Runs 26 7. Current Meter Package. External and Internal Arrangement (A), F i lm Record (B) and Mounting Frame (C) 27 8. RUN 2: D i r e c t i o n a l Frequency of Bottom Currents 35 9. RUN 2: Maximum V e l o c i t y by D i r e c t i o n of Bottom Currents 36 10. RUN 2: V e l o c i t y - Time - Tide Comparison 37 11. RUN 4: D i r e c t i o n a l Frequency of Bottom Currents 39 12. RUN 4: Maximum V e l o c i t y by D i r e c t i o n of Bottom Currents 4 0 13. RUN 4: V e l o c i t y - Time - Tide Comparison 41 14. RUN 6: D i r e c t i o n Frequency of Bottom Currents 4 5 15. RUN 6: Maximum V e l o c i t y by D irec t ion of Bottom Currents 4 6 16. RUN 6: V e l o c i t y - Time - Tide Comparison 47 17. RUN' 7: D i r e c t i o n a l Frequency of Bottom Currents 48 18. RUN 7: Maximum V e l o c i t y by D i r e c t i o n of Bottom Currents 49 19. RUN 7: V e l o c i t y - Time - Tide Comparison 50 v i i FIGURE PAGE 20. RUN 8: D i r e c t i o n a l Frequency of Bottom Currents 54 21. RUN 8: Maximum V e l o c i t y by D irec t ion of Bottom Currents 55 22. RUN 8: V e l o c i t y - Time - Tide Comparison 56 23. RUN 9: D i r e c t i o n a l Frequency of Bottom Currents 57 24. RUN 9: Maximum V e l o c i t y by D i r e c t i o n of Bottom Currents 58 25. RUN 9: V e l o c i t y - Time - Tide Comparison 59 26. RUN l O : D i r e c t i o n a l Frequency of Bottom Currents 64 27. RUN 10: Maximum V e l o c i t y by D irec t ion of Bottom Currents 65 28. RUN 10: V e l o c i t y - Time - Tide Comparison 66 29. RUN 11: D i r e c t i o n a l Frequency of Bottom Currents 67 30. RUN 11: Maximum V e l o c i t y by D irec t ion of Bottom Currents 6 8 31. RUN 11: V e l o c i t y - Time - Tide Comparison 69 32. Schematic Diagram Showing Flow Conditions Between Quatsino Sound and the Rupert-Holberg Basin During (a) Flood Tides and (b) Ebb Tides 75 33. Schematic Diagram Showing Flood Tide Condit ion 79 34. Schematic Diagram Showing Ebb Tide Condit ion 80 35. Schematic Diagram for Maximum Density Flood Tide 81 36. Locat ion Map Seismic Sections 1971-1972-1973 87 37. Continuous Seismic Ref lec t ion P r o f i l e s of Rupert I n l e t , March 1971 88 38. Continuous Seismic Ref lec t ion P r o f i l e s of Rupert I n l e t , September 1972 89 39. Continuous Seismic Ref lec t ion P r o f i l e s of Rupert I n l e t , September 197 3 90 40A. Continuous Seismic Ref lec t ion Longi tudina l P r o f i l e of Rupert I n l e t , March 1971 91 v i i i FIGURE PAGE 40B. Continuous Seismic Ref lec t ion Longi tudinal P r o f i l e of Rupert I n l e t , September 1973 91 41. Continuous Seismic Ref lec t ion P r o f i l e s of Holberg I n l e t , September 1972 92 42 42. The Interpretat ionoof Continuous Seismic P r o f i l e Line 9 of Rupert In le t from September 1973 Survey 9 3 43. V e l o c i t y and Grain Size Relat ionship for E r o s i o n , Transportat ion and Deposi t ion. Hjulstrom's diagram with modif icat ions 107 44. S e t t l i n g Time i n 10 cm/sec Current 108 45. Relat ionship of T i d a l Current V e l o c i t y to Suspended Sediment Concentration 10 8 46. Sample Location Map 112 47. Unit B Locations 118 48. Top Unit A Percent Sand Map 126 49. Top Unit A Percent S i l t Map 127 50. Top Unit A Percent Clay Map 128 51. Top Unit A Sediment Type Map 129 52. Top Unit A Mean Grain Size Map 134 53. Top Unit A Sort ing (Standard Deviation) Map 135 54. Graphic Presentat ion of Grain Size D i s t r i b u t i o n and Sort ing of Top of Unit A Sediments about Quatsino Narrows 137 55. T a i l i n g D i s t r i b u t i o n Map September 1973 Af ter F i r s t Two Years of Production 142 56. T a i l i n g Mean Grain Size Map 14 8 57. T a i l i n g Sort ing (Standard Deviation) Map 149 58. Graphic Presentat ion of Grain Size D i s t r i b u t i o n and Sort ing of T a i l i n g about Rupert Gap 151 59. Ternary P lo t I l l u s t r a t i n g Modi f i ca t ion of T a i l i n g Texture from T a i l i n g O u t f a l l Pipe to Holberg I n l e t . . . 1 5 2 i x FIGURE PAGE 60. T e r n a r y P l o t I l l u s t r a t i n g M o d i f i c a t i o n o f T a i l i n g T e x t u r e from O u t f a l l P i p e P r o g r e s s i n g up Rupert I n l e t 152 61. Index Map t o T u r b i d i t y S t a t i o n s 160 62. T u r b i d i t y Bottom 200' 161 63. T u r b i d i t y - S t a t i o n E ....162 64. T u r b i d i t y - S t a t i o n B 163 X ACKNOWLEDGEMENTS The wr i ter i s s incere ly gra te fu l to Dr. J.W. Murray, i n h i s capaci ty as thes is supervisor , for p i l o t i n g t h i s diverse p r o j e c t . My thanks to the Committee members for t h e i r cont inu-ing a v a i l a b i l i t y for d iscuss ion and c r i t i c a l reading of the manuscript: Professor J . B . Evans, Department of Mineral Engin-eer ing; Dr. W.C. Barnes and Dr. R . L . Chase, Department of Geo-l o g i c a l Sciences; Dr. P . H . LeBlond and Dr. T .R . Osborn of the Ins t i tu te of Oceanography. Many facu l ty members have been he lp-f u l , p a r t i c u l a r l y Dr. L . M . Lavkul ich (Soils) and Dr. A . G . Lewis (Oceanography). The t echn ica l s t a f f of Mineral Engineering fab-r i c a t e d the current meter mountings, Geologica l Sciences expedi-ted the f i e l d program while Miss L e s l i e Simpson, of S o i l Sciences, ass i s ted the laboratory work. Dr. John Lutenauer and David Johnson gave shipboard assistance under d i f f i c u l t condi t ions . Professor J . B . Evans, Head of the Environmental Con-t r o l Group, provided mater ia l and establ ished l i a i s o n with Mine personnel . The Management of the Utah Mining C o . , i n p a r t i c u l a r Mr. M. Prat t and Mr. Glen Andrews, speeded the project with many courtes ies inc lud ing release of data , use of camp f a c i l i t i e s , i n -strument shop and boat time. My s incerest thanks to Mr. C A . P e l l e t i e r of the Utah Environmental Group for his interested p a r t i c i p a t i o n and for the cooperation of h is capable s t a f f . Outside the U n i v e r s i t y , Dr. M. Aydin , Consult ing Geo-p h y s i c i s t , Calgary, c r i t i c a l l y reviewed the seismic i n t e r p r e t a t i o n and offered h e l p f u l comments, while Dr. D .V. E l l i s and Dr. J . L . L i t t l epage of the Univers i ty of V i c t o r i a gave guidance on other associated aspects. To these and many others I extend my thanks. CHAPTER I INTRODUCTION This thes is considers the sedimentation regime of Rupert I n l e t , B r i t i s h Columbia, i n which large volumes of mine d e t r i t u s are being deposited. The thes is maintains that natura l sedimentation i s dominated i n t h i s s h a l l o w - s i l l e d i n l e t by bot-tom currents which have a net e f fec t of moving sediment up i n -l e t away from the mouth. This propos i t ion i s supported by oceanographic, seismic and sediment observations. The projec t u t i l i z e s data being produced by the monitoring program respons-i b l e for environmental q u a l i t y surve i l lance which produces com-parat ive sequential data i n a manner and amount not previous ly a v a i l a b l e . The s ign i f i cance of the thes is i s that i t points to p o t e n t i a l geo log ica l categor iz ing of i n l e t s based on sedimenta-t i o n regime. Together with other d i s c i p l i n e s , such work may lead to p r e d i c t i v e r e s u l t s for proposed u t i l i z a t i o n of t h i s type of coas ta l environment. In October 1971 the Is land Copper Mine, second larges t copper mine and m i l l complex i n Canada (Mamen, 1973), was placed i n product ion. The mine i s located near tidewater on the north shore of Rupert I n l e t , part of the Quatsino Sound system of northern Vancouver Island (Figure 1) . The m i l l has a capacity of 33,000 tons/day. Following a p p l i c a t i o n to the B r i t i s h Colum-b i a P o l l u t i o n Control Branch and due process of pub l i c enquiry, a P o l l u t i o n Control Permit was issued to allow the mine to pro-2 ceed with the approved plan to premix the m i l l t a i l i n g with sea water and dispose of them through an o u t f a l l pipe 148 feet be-low the surface . The l i m i t a t i o n s of phys ica l and chemical para-meters of the m i l l e f f luent were determined, and an independent agency es tabl i shed to ensure q u a l i t y contro l and evaluat ion of environmental impact. The Univers i ty of B r i t i s h Columbia was appointed the independent agency with members from the Ins t i tu te of Oceanography, the Departments of Geologica l Sciences and C i v i Engineering, co-ordinated by the Head of Mineral Engineering (Evans, et al_ 1973). In i t s submittal to the P o l l u t i o n Contro l Branch Utah Construct ion & Mining C o . , owners of the Is land Copper Mine, maintained i n i t s b r i e f (Utah, 1971) that the estimated area of t a i l i n g cover would be some 1600 acres , about one-tenth of the i n l e t . The t a i l i n g depos i t iona l s i t e would cons is t of an area extending down slope from the d i sposa l pipe with the f ine f r a c -t i o n moving g r a v i t a t i o n a l l y , i n part as turb id flow, to l i e be-low 400 feet i n the deepest part of the basin below Quatsino Narrows. The b r i e f submits that the t a i l i n g so ponded w i l l be e f f e c t i v e l y below the zone of s i g n i f i c a n t inf luence of t i d a l e f fects from the Narrows. Examination of sediment and seismic data which had been c o l l e c t e d during the pre-operat ion phase led the author to question the i n i t i a l conclusions and present a t h e o r e t i c a l o r a l argument to the Department of Geologica l Sciences i n June 1972 that "up- in le t grav i ty currents may be a major factor i n s e d i -3 4 ment d i s t r i b u t i o n i n s h a l l o w - s i l l e d f j o r d s w i t h low sediment i n -put: Rupert I n l e t i s an example". In p a r t i c u l a r , the presence of coarse e l a s t i c s below the Narrows and the i n t e r p r e t a t i o n of a t h i c k wedge of f i n e e l a s t i c s on the north c e n t r a l f l a n k of Rupert b a s i n provided a b a s i s on which to examine the a l t e r n a t e pro-p o s a l . The a l t e r n a t e proposal suggests t h a t w h i l e s i g n i f i c a n t c u r r ents e x i s t i n the lower reaches of Rupert I n l e t , t h e i r end e f f e c t i s to remove sediments from the lower reaches and deposit them on the northern f l a n k near the mine s i t e . Documentation of t h i s t h e o r i z e d regime and discovery of i t s e f f e c t on t a i l i n g d i s -p e r s a l and sedimentation i s the c e n t r a l o b j e c t i v e of the study. The purpose of the study was to determine the c o n t r o l s on n a t u r a l sedimentation i n Rupert I n l e t . The immediate r e s u l t would be a b e t t e r understanding of the s h o r t - and long-term sedimentation of t a i l i n g d e p o s i t i o n . The long-term r e s u l t would be an improved understanding of the sedimentation regime i n t h i s and s i m i l a r h i g h - s i l l e d f j o r d s . The eventual c o n t r i b u t i o n i s t h a t i t may lead to a c l a s s i f i c a t i o n of f j o r d s on a b a s i s of energy inp u t as r e f l e c t e d i n sedimentation p a t t e r n s . The scope of the p r o j e c t r e q u i r e s i n t e r p r e t a t i o n of the n a t u r a l sediments from cores and samples and seismic data to e s t a b l i s h the c o n t r o l s of the sedimentation regime. Sediments are the only record which show the long-term e f f e c t together w i t h major changes and m o d i f i c a t i o n s to the regime. In conjunction w i t h oceanographic observations, sediment records may i n d i c a t e whether the dominant c o n t r o l i s an o r d e r l y seasonal sequence or 5 the r e s u l t of abrupt or catastrophic events at i r r e g u l a r per iods . The upper few centimetres of natura l sediments should accurately portray the e x i s t i n g sedimentation regime. T a i l i n g depos i t ion requires separate examination because i t or ig inates i n large volumeeat a point source, perhaps overloading or modifying the pattern of natura l sedimentation. The r e s u l t may be at variance with the i n t e r p r e t a t i o n of the sediment regime as provided by the natura l sediments. The study goes further i n a c t u a l l y measuring e x i s t i n g bottom currents to e s t a b l i s h t h e i r order and magnitude and i n attempting to re la t e them to the sedimentation pat tern . I t points to the need of d e t a i l e d study of the dynamics of the ent i re water column on both sides of the s i l l . The methods used i n th i s study are i n three main areas: bottom current observat ion, seismic i n t e r p r e t a t i o n and sediment a n a l y s i s . The phys i ca l s e t t ing i s presented i n Chapter II and includes pert inent background on a e r i a l and marine topography, reg ional and mine geology, and an in troduct ion to the oceano-graphic parameters l o c a l i z i n g the s p e c i f i c problems. Chapter III discusses the bottom current s tudies . This work includes se lec-t i o n of an instrument and designing of a su i tab le instrument-mounting to record current v e l o c i t i e s immediately above the s e d i -ment-water in ter face for prolonged per iods . The bottom-current program consisted of several cruises co inc id ing with spring t ides i n the second h a l f of 1973 r e s u l t i n g i n e ight successful current meter runs which produced about 1500 hours of bottom data. The data c l e a r l y e s t a b l i s h the presence of s i g n i f i c a n t bottom c u r -rents and a s s i s t i n understanding t h e i r organizat ion and in ten-6 s i t y i n the lower reaches of Rupert and Holberg i n l e t s . Chapter IV in terpre t s the three annual seismic surveys (1971, 1972 and 1973) performed under the P o l l u t i o n Control Permit. These i n t e r -pretat ions c l e a r l y indicate eros iona l and depos i t iona l s i t e s of the natura l sediments as we l l as submarine s l i d e and slump structures r e s u l t i n g from mine dumping. Chapter V considers the sediment d i s t r i b u t i o n as deduced from gra in s ize a n a l y s i s . I t includes evaluations of the natura l sediments and the t a i l i n g , u t i l i z i n g cores and samples from the p o l l u t i o n contro l program. The need for a d d i t i o n a l sediment data required organizat ion of an independent coring and sampling cruise i n A p r i l 1973. T u r b i d i t y i s included as part of the d i scuss ion of sediments. Beyond the primary c r u i s e s , the author was a f i e l d observer b r i e f l y for the seismic and t u r b i d i t y studies as we l l as on numerous mine surveys which included geo log ica l and b i o l o g i c a l i n v e s t i g a t i o n s . The thes is covers pre -operat iona l condit ions and the f i r s t two years of operation to September 1973, with the bottom-current studies continuing to December 197 3. A l l shipboard work u t i l i z e d l o c a l f i s h i n g boats with support from the Mine outboard runabout. The most useful vesse l was the "WALTER M", a s i x t y - f i v e foot drum se iner . The seaman-ship and l o c a l knowledge of the capta ins , mainly Kwakiutl Indians, was of great he lp . The complete co-operation of the Univers i ty contro l agency and the Mine personnel , with free access to Mine f a c i l i t i e s and data , was u n s t i n t i n g l y provided for th i s r e - e v a l u a t i o n . 7 CHAPTER II PHYSICAL SETTING The phys i ca l se t t ing of the Holberg-Rupert basin and i t s environs i s b r i e f l y discussed inc lud ing topography, geology, p r e c i p i t a t i o n and oceanography. This d i scuss ion introduces factors which d i r e c t l y and i n d i r e c t l y exert s i g n i f i c a n t contro l on the sedimentation regime of the bas in . Topography Northernmost Vancouver Island (Figure 1) i s a region of general ly rounded mountains with hummocky l o c a l topography densely treed by coniferous west coast r a i n fore s t . The mount-ains r i s e to 2000 feet both north and south of the area of de-t a i l e d i n t e r e s t (Figure 2) . The area i s d issected by Quatsino Sound and i t s branching system of i n l e t s ( f jords ) . Holberg and Rupert i n l e t s occupy the over-deepened middle sect ion of a g l a c i a l l y scoured topographic trough which extends across the i s l a n d . The head of Rupert In le t i s separated from Queen Char lot te S t r a i t by a broad low area 9 miles wide i n which the height of the land barely exceeds 300 feet . Westward, where the head of Holberg i s 12 miles from the P a c i f i c along a v a l l e y , the height of land i s only about 100 feet . Considering the eus tat ic and i s o s t a t i c v a r i a t i o n s , i t seems l i k e l y that the Holberg-Rupert basin which has a maximum depth of 56 5 feet had 8 connection to the sea at various times v i a any or a l l of Holberg I n l e t , Rupert In le t or Quatsino Sound. Rupert In le t has a length and mean width of 6.3 and 1.1 mi l e s , r e s p e c t i v e l y , while Holberg has a length and mean width of 21.3 and 0.8 mi l e s , re spec t ive ly (Pickard, 1963). Drinkwater (1973) gives the volumes as 2,000 x 10 m for Rupert and 3,400 x 6 3 10 m for Holberg, the Holberg-Rupert basin t o t a l l i n g 5400 x 6 3 10 m . Drinkwater notes the average t i d a l prism inflow as 170 x 6 3 6 3 10 m with a maximum of 260 x 10 m . Figure 2 i s the base map for the study area and i s used i n whole or i n part repeatedly at varying sca les . Numerical / a lphabet i ca l coordinates a s s i s t l oca t ion reference (e.g. Hankin Po int , 33/1) . In subsequent chapters, several terms are used which have been selected s p e c i f i c a l l y for t h e i r topographic con-notat ion; i n p a r t i c u l a r : Quatsino Narrows o u t f a l l , Rupert gap, Holberg gap, Rupert trough and Holberg trough. The reason for topographic descr ip t ives i s that t h i s study i s concerned with the movement and l o c a l i z a t i o n of sediment i n r e l a t i o n to the topo-graphy. The Narrows o u t f a l l i s the vent to the f lood t ide and, as w i l l be developed, the s ing le most important inf luence of sedimentation i n the bas in . The term 'Holberg-Rupert bas in ' i s used but i n t h i s study i t general ly excludes the narrow, western h a l f of Holberg In le t (beyond 3 /B) . There i s no bottom topo-graphy separating Rupert from Holberg, however the Y-shaped junc-t i o n of the i n l e t s with Quatsino Narrows places Hankin Point i n p o s i t i o n to d i v i d e the in-pouring f lood t i d e . The deepest part 9 + I A + -B + -C + -D + -E + -F + -6 + -H 4: -I + -J + -K + -L + -M + -+ 2 i + -+ -i + -i + -i + -l + -i + -i + -i + — i + -i + -I + -+ -+ 2 4 + 2 5 + 2 6 + 2 7 + 2 3 + 2 9 + 3 0 + 31 i I I i i I I I • t s=t • r t .+ - + - ' 3 2 + 3 3 + 3 4 + 3 5 + 3 6 + 3 7 + 3 8 + 3 9 + 4 0 ^ 4 1 + 4 2 + 4 3 + 4 4 + 4 5 + 4 6 + R U P E R T " B A- s I N • * - • - * I I i r i i i i i i i + - + -+ - + - + -1 V « V J I 4 7 + 4 8 + 4 9 + 5 0 4 i i - + - + - + - + - + - - + -* + - + - +• ^ + -r 1 1 1 1 + 1 + 1 — + 1 - + 1 - + - + - + - + - -h 1 l 1 1 1 1 4- - + - + - + • —" + - + 1 I I 1 1 1 + - + - + - + — + - .+ 1 1 1 1 1 1 4- - + - + - + — + - + 1 1 1 1 1 1 4- - + - + - + - + - + 1 1 1 1 1 1 + - + - + - + — + - . + + + + + A - + B - 4 c - + D - + E - + "F - + G - + H - + I - + J - + K - + L - 4 M - + - 4- - + -Figure 2. 10 of the basin i s a narrow topographic notch extending from below the Narrows 1.5 miles up Rupert In le t and 2 miles up Holberg I n l e t . About 1 mile wide at sea l e v e l and 500 feet deep, t h i s notch forms the Rupert and Holberg gaps. Up both i n l e t s beyond the gap, the term 'trough' has been appl ied s ince the topography i s e s s e n t i a l l y long, narrow and r e l a t i v e l y deep. Topographic data i n Rupert In le t are from a commercial survey for the Mine based on echograms with radar l o c a t i o n , supplemented i n Holberg In le t and i n Quatsino Narrows by Canadian Hydrographic Service charts (1972a, 1973a). For Rupert In le t and lower Holberg gap a 100-foot contour i n t e r v a l i s presented. Up Holberg In le t the 300-foot contour i s shown for the main trough, with the 150-foot contour indicated above the Straggl ing Islands where the trough becomes shallower. The outer s i l l of Quatsino Sound i s offshore from the mouth where the passage of bottom waters must cross over a thres -hold of 270 feet (82m). The f i r s t r i s e wi th in the mouth of the Sound (Pickard, 1962) i s 468 feet (143m). The shallow outer s i l l of the Sound controls the entrance of co ld dense waters which have upwelled o f f the she l f . Pickard includes Quatsino Sound proper and Neroutsos In le t as one un i t as there i s no separating inner s i l l , and gives a mean width of 1.4 mi l e s , mean m i d - i n l e t depth of 490 feet (150m) and a maximum depth of 800 feet (245m) for the complex. At the approach to Quatsino Narrows, the Sound turns eastward becoming shallower to about 100 feet (30m) before 11 turning abruptly north to j o i n Quatsino Narrows. Quatsino Narrows proper i s a spec ia l topographic case. Recent mapping (Can.Hyd.Serv. , 1973a) shows the Narrows to be e s s e n t i a l l y a n e a r - v e r t i c a l , walled canyon 200 feet deep with one-half below sea l e v e l . A narrow s i l l at the north end r i s e s to wi th in 60 feet of sea l e v e l . Flood t ides passing through the system are forced along a route invo lv ing several sharp changes i n d i r e c t i o n , then over a narrow, abrupt s i l l before being je t ted at up to 6 knots (Can.Hyd.Serv. , 1972b) into the basin to be d iv ided by Hankin Po int . The thorough mixing process caused by Quatsino Narrows i s discussed by Drinkwater (1973). With the present topographic r e l a t i o n s h i p s , i f Quatsino Narrows was blocked then the Marble River drainage would flow into Holberg-Rupert basin and dra in westward to San Josef Bay. Quatsino Narrows i s a f a u l t zone (Muller , 1971) and as shown i n l a t e r d i scuss ion was not always open, being e i ther non-existent , above a lowered sea l e v e l , or i ce choked. I t i s i n t e r e s t i n g to note that the headwater quarrying of the f a u l t zone by the t ides of Quatsino Sound may have resu l ted i n drainage p i racy by t i d a l a c t i o n . Geology The f i r s t geo log ica l report on northern Vancouver Island was by Dawson (1886) with the most recent mapping done by Mul ler (1971). The l a t t e r maps a major f a u l t zone, sometimes d i s l o c a t e d , extending i n a gentle arc across Vancouver Island 12 from San Josef Bay on the west coast through Holberg and Rupert i n l e t s to near Suquash on the east coast . The l i n e a t i o n i n v i t e s speculat ion that i t may extend across the south end of Queen Charlot te S t r a i t to the mainland and provide s t r u c t u r a l contro l for the lower reach of Knight I n l e t . The s trat igraphy of the area (Young and Rugg, 1970) i s dominated by Lower T r i a s s i c to Lower Juras s i c sequence comprising the Karmusten Formation, dominantly vo lcanic flows; the Quatsino Formation, mainly l ime-stone with minor vo lcan ic s ; and the Bonanza Subgroup of pyro-c l a s t i c s , a r g i l l i t e s and l imestone. The sequence i s l a r g e l y competent rock and ranges from 10,000 to 20,000 feet . L o c a l l y , as at Port Hardy, Cretaceous e l a s t i c s with impure coals reach 1000 feet i n th ickness . The f a u l t contro l which Mul ler indicates for Quatsino Narrows c a r r i e s through Rupert gap. The r igh t -ang le bend at the south end of the Narrows i s c o n t r o l l e d by another f a u l t . Mul ler avoids p lac ing a f a u l t a c t u a l l y through Rupert In le t as he does through Holberg I n l e t . Along Quatsino Sound Mul ler i s able to t i e s t r u c t u r a l contro l across t h i s major physiographic feature and therefore indicates no dominant s t r u c t u r a l or s t r a t i g r a p h i c c o n t r o l . The area i s poor i n outcrops, being covered by g l a c i a l overburden and dense fore s t s . Vancouver Island was heavi ly g l a -c ia ted by at l east two C o r d i l l e r a n ice sheets, Vashon and Sumas, that extended westward from the coast range onto the cont inenta l 13 she l f west of the i s l a n d (Mathews, e t a l , 1970). The thickness of the sheet i s shown as d iminishing r a p i d l y i n the west coasta l area. Carter (197 3) places commencement of normal sedimentation i n Barkley Sound between 7000 to 3000 years B . P . with r e l a t i v e sea l e v e l about 10 metres below the present stand. Since the Holberg-Rupert basin i s in land from the sea near the centre of the i s l a n d , the end of g l a c i a t i o n might be expected to approxi -mate more c lo se ly the l a t t e r date. Both the west and east coasts may have been free of i ce around the north end of the i s l a n d before the ice disappeared from the i n t e r i o r v a l l e y s . Sedimentation studies i n the i n l e t s of B r i t i s h Columbia have been l i m i t e d . Some sampling was done by Pickard (19 56) as part of a reg ional oceanographic study. Of the d e e p - s i l l e d i n l e t s , Toombs (1956) studied Bute In le t ; MacDonald & Murray (1973) studied J e r v i s In le t ; and Murray and Ricker (in prepara-t ion) studied Howe Sound, a l l mainland i n l e t s . On Vancouver Is land the euxinic Saanich In le t has been studied by Gucleur & Gross (1964), while Carter (1973) recent ly studied the coas ta l and semi-sheltered waters of Barclay Sound. The present work i s the f i r s t sedimentological study of a s h a l l o w - s i l l e d B r i t i s h Columbia i n l e t with non-euxinic bottom condi t ions . The mine geology i s described by Young and Rugg (19 70). The ore body, which does not outcrop, i s about 1200 feet wide and extends for a m i l e . A d i k e - l i k e quartz-monzanite body of Jurass ic age intrudes the Bonanza tuf f s of T r i a s s i c age. 14 M i n e r a l i z a t i o n i s p y r i t e , magnetite, c h a l c o p y r i t e , borni te and molybdenite i n descending order . The ore i s estimated at 28 m i l l i o n tons averaging 0.52% copper and 0.029% MoS 2 . An estima-ted 25% of the ore i s i n the dike while 75% i s i n associated a l t ered zones and the brecciated country vo lcanics (Mamen, 1973). Af ter 25 years the f i n a l p i t (Pratt , 1970) w i l l occupy 490 acres , being 7,500 feet long by 3,500 feet wide and 1000 feet deep, 800 feet below sea l e v e l . The p i t w i l l form a 380-acre lake and cause some 700 acres of new shorel ine to be constructed of waste rock. The mine w i l l produce about 230,000 tons of copper concen-trate and 1,800 tons of molybdenum concentrate/year (Utah, 1971). The ore i s ground to about 0.07mm (4tj)) then treated . The t a i l i n g from the m i l l , about 33,000 tons/day (12 x 10 6 tons/ year ) , are discharged at about 50% so l id s by weight. The l i q u i d e f f luent i s about 1 part fresh water to 1 part sea water. The discharge i s 148 feet below sea l e v e l , about 9 feet above the o r i g i n a l topography. An i n t e r e s t i n g comparison i s that the 6 3 Fraser River annual discharge i s i n the order of 2 8 x 10 yds (Mathews and Shepard, 1962) which approximates 20 to 25 x 10^ tons /yr of sediments, dependent on gra in s ize and compaction. 6 The t a i l i n g d i sposa l of the Mine i s about 12 x 10 t o n s / y r , 50% of the Fraser River i n sediment volume. P r e c i p i t a t i o n and Drainage P r e c i p i t a t i o n var ies s i g n i f i c a n t l y from i t s long-term average for any given month, both seasonally and l o c a l l y . The ten-year average for Port Hardy has been used as a standard 15 (Utah 1972/73) with p r e c i p i t a t i o n in land at Holberg-Rupert prob-ably higher. The average indicates that heavy p r e c i p i t a t i o n of 10.5 inches/month occurs i n the period October through January, October having the heaviest with 12.34 inches. The highest ten-year monthly maximum was 19.16 inches i n October 1967. Moderate p r e c i p i t a t i o n of about s ix inches/month occurs i n February, March and A p r i l and again i n September. Low p r e c i p i t a t i o n averaging 2.4 inches/month occurs from May through August with August having the lowest average of 1.97 inches/month. On occasion June, Ju ly and August have each recorded less than one inch of p r e c i p i t a t i o n . Drinkwater (19 73) notes a lag of one to two days between p r e c i p i t a t i o n and r i v e r discharge. Coote (1964) notes that Tofino I n l e t , which has many s i m i l a r i t i e s to the Holberg-Rupert basin (Drinkwater, 1973), suffers incurs ion of i t s bottom water only i n the summers of dry years . Observers often point to the unusual drainage arrange-ment at Rupert I n l e t , where the only s i g n i f i c a n t r i v e r enters the i n l e t c lose to the out l e t rather than at the head of the i n l e t . There are incomplete data for fresh water entering the basin but 6 3 Drinkwater (1973) estimates average inflow to be 12 x 10 m and 6 3 about 40 x 10 m under maximum condi t ions , ha l f of which i s from the Marble R iver . The input of the Marble River i s r e l a t i v e l y minor in volume perhaps 5% of the t i d a l input through the Narrows. Further , i t i s not an important sediment-carrying r i v e r . The main e f fec t of the Marble inflow i s probably to produce a l o c a l l o w - s a l i n i t y upper water anomaly i n Rupert gap which may increase 16 the depth of i n t r u s i o n of density-dependent currents . In terms of fresh water and sediment c o n t r i b u t i o n , other streams are con-s idered of only l o c a l s i g n i f i c a n c e . Oceanography The oceanographic parameters of the Quatsino system drew ear ly at tent ion because of the e f f luent from the pulp m i l l at Port A l i c e on Neroutsos I n l e t . The work of Hutchinson and Lucas (1927) and Waldichuk (195'8) was d irec ted to t h i s problem. Pickard (1963) reported on the area as part of a reg iona l study: In Holberg and Rupert i.t had been ant i c ipated that the shallow s i l l of Quatsino Narrows separating them from Neroutsos would r e s u l t i n stagnation and low disso lved oxygen v a l u e s . . . . t h i s was not the case. In f a c t , apart from the deepest sample at the head of Holberg, the water i n the two i n l e t s was remarkably uniform from top to bottom with the highest oxygen values at 100m of a l l Vancouver Island i n l e t s [with minor except ions] . Drinkwater (1973) whose at tent ion was centred on the Holberg-Rupert rather than the Neroutsos basin had i n addi t ion to the p r i o r work, access to data from the r e p e t i t i v e , systematic Mine surveys from March 1971 to June 1972. The diagrams of Drinkwater have been updated to September 197 3 and cause some r e v i s i o n to e a r l i e r genera l i za t ions . The two s tat ions B and D are located on Figure 3 with t h e i r temperature, s a l i n i t y and d isso lved oxygen content for the period March 1971 to September 1973 i l l u s t r a t e d i n Figures 4 and 5, r e s p e c t i v e l y . Within the Holberg-Rupert bas in , Drinkwater (19 73) con-firmed e a r l i e r observations that temperature, s a l i n i t y and 18 o o STATION B 30 ft. ( 9m) 100 ft (30m) 550 ft. (167m) M J S o l M J ^ 0| M J 3 J97I 1972 1973 F i g u r e 4 . M o n t h l y V a l u e s o f Temperature, S a l i n i t y and D i s s o l v e d Oxygen C o n t e n t a t S t a t i o n B i n Holb e r g . I n l e t . E x t e n s i o n o f D r i n k w a t e r (1973) u s i n g Mine D a t a . 19 STATION D Figure 5. Monthly Values of Temperature, S a l i n i t y and Dissolved Oxygen Content at Station D i n Quatsino Sound. Extension of Drinkwater (1973) Using Mine Data. 20 d i s so lved oxygen, with allowance for surface e f f e c t s , fo l low seasonal trends but remain s i m i l a r for a l l horizons i n the water column. He noted a tendency for s l i g h t l y greater uniformity i n front of the Narrows. Temperature has a minimum i n ear ly spring and a maximum i n la te summer or ear ly f a l l . S a l i n i t y below-surface e f fec ts (100 feet) can general ly vary with in a monthly range of l ° / 0 0 and an annual range of 3 ° / 0 0 for any given hor izon . S a l i n i t i e s are larges t i n summer to ear ly autumn, and lowest i n ear ly s p r i n g . Dissolved oxygen l eve l s exh ib i t greater v a r i a t i o n than prev ious ly ant ic ipated with an annual range of nearly 5 ml/1 but r a r e l y varying more than 1 ml/1 wi th in the water column. The lowest value of 3 ml/1 occurred i n October 1971 and the highest value of 7.7 ml/1 i n March 1973. Outside the Narrows i n Quatsino Sound (Drinkwater, 1973) , the upper 200 feet (60m) are very s i m i l a r to the Holberg-Rupert bas in . Temperatures at various l eve l s are less uniform and s l i g h t l y colder than ins ide the bas in . The upper water s a l i n i t i e s of the Sound are s i m i l a r to the deep water s a l i n i t i e s i n the bas in . Dissolved oxygen i n the Sound compares with that i n the basin but i s general ly about one ml/1 greater for respec-t i v e horizons . The bottom water below 200 feet (60m) outside the Narrows has d i f f e r e n t c h a r a c t e r i s t i c s to the upper water of the Sound or the water i n the bas in . Temperatures of bottom water remain low,between 6 and 8°C with the maximum temperature of 9°C 21 i n midwinter. Dissolved oxygen content of the bottom waters i s low from ear ly summer u n t i l mid-autumn and i s high i n s p r i n g , varying less than 3 ml/1 i n summer 1971 and over 8 ml/1 i n la te winter 1973. The c o l d , h i g h - s a l i n i t y , low-oxygen water i s a t -t r ibuted to the advance of water that upwells o f f the coast of Vancouver Island s p i l l i n g into the i n l e t i n summer (Lane, 1962). Pickard (1963) found there i s no c l ear seasonal cyc le to the up-wel l ing and observes that the densi ty of upwelling water i s always less i n the i n l e t than the maxima of the water outs ide . He recognized that upwell ing water probably enters Quatsino Sound, but may not do so every year. This observation of the v a r i a t i o n i n the amount of incurs ion i s supported by Figure 5. Dense, low-oxygen water dominates summer 1971 but while the s a l i n i t y reaches s i m i l a r values i n la te summer 1972 and 1973, the combined oxygen and s a l i n i t y data i n f e r less incurs ion of "up-welled" water i n those years . As recognized by Pickard (1963), the uniformity of temperature and s a l i n i t y wi th in the basin plus the consistent presence of d i sso lved oxygen c l e a r l y indicate that c i r c u l a t i o n ex i s t s i n the Holberg-Rupert bas in . This thes is draws at tent ion to the d i s t r i b u t i o n and v e l o c i t y of th i s c i r c u l a t i o n at bottom and therefore i t s capacity to move sediments. As subsequently developed, density i s the factor which together with f l o o d - t i d e v e l o c i t y and volume, controls the nature and d i s t r i b u t i o n of currents i n the bas in . 22 Data from the monitoring program suggest that spent su lphi te concentrations may prove a usefu l t racer to the c i r c u l a -t i o n i n the bas in . The spent su lphi te or ig inates i n Neroutsos In le t at the Port A l i c e pulp m i l l and i s often but not always present i n amounts commonly i n excess of 40 ppm and recorded as high as 640 ppm (Utah, 1972/73) i n the surface and upper waters of Quatsino Sound at the entrance to Quatsino Narrows. This water moves into the Holberg-Rupert basin on the f lood t ide and seeks i t s own density l e v e l i n the water column, carry ing with i t the spent-sulphite s ignature. Within the b a s i n , spent su lphi te l eve l s have been recorded during the Mine surveys as high as 40 ppm i n the bottom water. While present data c o l l e c t i o n i s not su i tab le for mapping the currents , seasonal v a r i a t i o n i n values and v a r i a t i o n s wi th in the water column suggest that a program could be designed to use the spent su lphi te as a t r a c e r . The present data suggest deeper i n t r u s i o n of f lood water i n the autumn. September, 1972 ,was the only month for which data were ava i lab le that ind icate i n t r u s i o n to near-bottom below the Narrows i n the deepest part of the bas in . This study does not resolve the problem of the density r e l a t i o n s h i p on e i ther side of Quatsino Narrows. Drinkwater (1973) bel ieves the increase i n density i n the basin i s most probably gradual and re la ted to run-o f f l eve l s but he does not discount the p o s s i b i l i t y of sudden i n t r u s i o n of dense water from depth. G e o l o g i c a l l y , the question remains as to how much of the erosion below the Narrows i s caused by seasonally vary ing , r e p e t i -23 t i v e in trus ions and how much by unpredictable abrupt or catas-trophic events such as high storm t ides and tsunamis which may represent the combined maximum-density maximum-volume input , thereby prov id ing extraordinary eros iona l and carry ing capac i ty . By analogy, the comparison may be as to the geo log ica l impact of seasonal f l u c t u a t i o n i n r i v e r flow as compared with the e f fec t of an exceptional f l o o d . CHAPTER III 24 BOTTOM CURRENT STUDIES Two bas ic methods of determining the f i n a l d i s p o s i t i o n of sediment into the system are: (a) to examine the d i s t r i b u t i o n of the p r e - e x i s t i n g sediments on the assumption that the regime responsible for that d i s t r i b u t i o n w i l l eventual ly govern the d i s t r i b u t i o n of the induced sediment ( ta i l ing ) and (b) to examine the present bottom pattern of currents on the basis that these currents w i l l govern sediment d i s t r i b u t i o n . Chapters IV and V concern themselves large ly with the f i r s t method. Current studies are requ ired , however, s ince t a i l i n g d i s p e r s a l may not fol low analogously the d i s t r i b u t i o n of natura l sediments, being very d i s s i m i l a r i n that a great volume i s de l ivered from a point source — the o u t f a l l p ipe . There i s also the question as to whether the current regime which determined the natura l sediment d i s t r i b u t i o n i s the one i n e f fec t at present , s ince the phys i ca l condit ions of the coasta l water have var ied and continue to change as a r e s u l t of g l a c i a l withdrawal, both as to abundance of supply of sediment and as to topographic r e l a t i o n to sea l e v e l . This chapter out l ines experimental work which attempts to measure the currents near the sediment-water i n t e r f a c e . The work i s one of the f i r s t attempts to measure bottom currents of B r i t i s h Columbia i n l e t s and i s the most extensive study to date as to "time on bottom". Locations of the current meter runs are 25 shown on Figure 6. While the studies are l i m i t e d , they y i e l d s u f f i c i e n t data to e s tab l i sh that g e o l o g i c a l l y s i g n i f i c a n t bottom currents do occur i n Rupert In le t and to give some measure of t h e i r d i r e c t i o n and i n t e n s i t y . Instrumentation and Operation The Department of Geologica l Sciences purchased a very simple butTsuitable current meter f i l m recording instrument, General Oceanics Model 2011. Af ter producing some 28 days of data (Run 2) the instrument was l o s t on bottom (Run 3) , probably buried i n t a i l i n g . The data , however, were judged s u f f i c i e n t l y encouraging that two i d e n t i c a l instruments were purchased j o i n t l y by the Departments of Geologica l Sciences and Mineral Engineering. Figure 7 presents the external and i n t e r n a l arrange-ment of the instrument, the r e s u l t i n g f i l m s t r i p and a sketch of the mounting. The General Oceanics Model 2011 F i l m Recording Current Meter operates on the p r i n c i p l e of a negat ively buoyant wand tethered by a swivel at the top so that i t w i l l de f l ec t into the current i n a stable manner and at an angle and d i r e c t i o n that are a funct ion of current speed and d i r e c t i o n . The housing contains a d i r e c t i o n a l incl inometer at the top and a movie camera at the base which photographs a target recording i n c l i n a t i o n and compass bearing together with a calendar watch reading time and date. An adjustable t iming device contro l s the advance rate of the 3600-frame f i l m . The device i s c a l i b r a t e d using the U.S . Geolog ica l 28+ 29+ 30+ 31 + 32+ 33+ 34+ 35 + 36 + 37 + 38 + 39+ 40+ 41 + 42+ 43+ 44 + 27 Figure 7. Current Meter Package. External View and Internal Arrangement (A) F i lm Record (B) and Mounting Frame (C) 28 Survey f a c i l i t i e s at Baton Rouge, La. (Casagrandes, 1974). The "gallows" frame designed for t h i s study was f a b r i -cated of aluminum to avoid compass problems. The base of the instrument i s suspended 30 inches above the cross legs of the frame. The e f f e c t i v e height of the instrument w i l l vary with the current and the amount of s e t t l i n g or b u r i a l of the base but w i l l be measuring currents 1 to 1 1/2 metres above bottom. The 18-inch diameter pads carry a 22-25 l b . weight, usually bagged gravel, and are secured to each drop leg by a 50-lb. capacity shear pin. The four i n d i v i d u a l foot pads avoid the "swimming" problem inherent i n lowering a large f l a t sheet. A further shear pin with a 750-lb. capacity located near the base of the upright enables the upper stand to break free i f the base becomes buried. The stand i s lowered by a polypropylene rope which f l o a t s free of the equipment and to ensure t h i s a f l o a t i s fastened to the l i n e about 50 feet above the stand. The descent of the package to bottom can be followed on an echo-sounder. Line i s played out with weights added at i n t e r v a l s and the sunken l i n e l a i d to shore. A black-coated e l e c t r i c a l wire i s used i n the t i d a l zone as a lead to shore to prevent v i s u a l detection and tampering. The instrument and i t s support frame show l i t t l e tendency to become fouled. At low v e l o c i t i e s the instrument has two problems. In operation, the swivel and shackling device with which the i n s t r u -ment i s suspended from i t s support frame has design l i m i t a t i o n s 29 which under quiescent condit ions may cause the instrument to hang up at various angles less than 5° (7.5 cm/sec) and return to v e r t -i c a l p o s i t i o n . The problem does not apply to nor a f fec t v e l o c i -t i e s greater than 7.5 cm/sec. In reading , for v e l o c i t i e s below 13 cm/sec (10° i n c l i n a t i o n ) the convergence of longitude and lack of l a t i t u d e l ine s r e s u l t i n a marked tendency to group d i r e c t i o n i n th i s range at 30° mult ip les ( i . e . 025, 055, 085, e t c . ) . This tendency w i l l be noted i n regard to d i r e c t i o n a l frequency (e.g. Figure 14). However, there i s l i t t l e d i f f i c u l t y with i n c l i n a -t ions over 10° i n reading the d i r e c t i o n to ±5° and estimating i n c l i n a t i o n to the nearest degree. The p r a c t i c a l l i m i t a t i o n of the instrument i s that the f i l m must be labor ious ly read. These readings must then be con-verted": time to s iderea l time, magnetic azimuth to true azimuth, and i n c l i n a t i o n i n degrees to v e l o c i t i e s i n cm/sec. Data r e -corded during t h i s thes is comprise more than 15,000 frames g iv ing 60,000 values , each requ ir ing conversions. Most conventional oceanographic methods measure current "near" bottom but general ly considerably further of f bottom than des irable for geo log ica l study of sediment transport . Geologica l workers (Schubel, 1971; Sternberg et a l , 1973) seek a distance o f f bottom of one or two metres as c lose enough to appraise the ve lo -c i t y at the sediment in ter face without becoming d i r e c t l y involved i n the in t er face . The instrument package succeeds i n t h i s objec-t i v e . For geo log ica l purposes the low-ve loc i ty currents are 30 often of l ess concern than the advantage that the instrument per-forms we l l while unattended for long periods at the sediment-water in ter face and again i n th i s respect the instrument package performed most s a t i s f a c t o r i l y . Current Observations Current observations were attempted at or near spring t ides for the six-month period mid-June to mid-December, 1973, with data c o l l e c t e d from J u l y 12 to August 9 and i n t e r m i t t e n t l y between October 24 and December 13. In t o t a l , 1485 hours of data have been c o l l e c t e d from eight l oca t ions . Table I presents a summation of s t a t i s t i c s for each current meter run . Runs 6 and 7, 8 and 9, 10 and 11 are pa ir s that were recorded simultaneously. The runs are discussed separately then re la ted to the poss ib le general current pat tern , as evidenced by the bottom currents . This approach provides the basis for d i scuss ion of the s i g n i f i -cance of the bottom current pattern to sedimentation i n the i n l e t and the e f fec t upon t a i l i n g d i s p e r s a l . Correc t ion factors for magnetic d e c l i n a t i o n and for t ide time and range have been a r b i t r a r i l y but cons i s t ent ly app l i ed . Correc t ion for magnetic d e c l i n a t i o n has been used i n ca l cu la t ions as 2 5 ° which i s wi th in 1° of the true d e c l i n a t i o n and consistent with the inaccuracies inherent i n reading the instrument. Tide times are cons i s tent ly accepted as plus one hour on Tofino time, the Reference Port (Can. Hyd. S e r v . , 1973b), and given i n P a c i f i c Standard time. Tide height arid range for Tofino are used and have not been computed separately for Rupert 31 RUN LOCATION DEPTH DATES (1973) LENGTH EXPOSURE OUTCOME AXIS 11 Rupert 1/35 475" June 24-July 12 No data. E l e c t r i c a l Failure 12 Rupert 1/35 354" July Aug • 12 8 2300 9 8 1000 659:30 hrs 13 min Good Data 160-340 13 Rupert 1/35 495' Aug 9-Sept 7 No Data Instrument Lost »4 Rupert F/39 258' Oct Oct 24 8 1136 27 8 0832 68:56 hrs 4 min Good Data 160-340 #5 Rupert 372' Oct 24 No Data. G/39 Oct 27 Mechanical Instrument Failure 16 Holberg J/31 510' Nov NOV 6 8 1140 13 8 1115 167:35 hrs 4 min Good Data 010-190 #7 Rupert J/34 516' Nov Nov 6 8 1225 13 8 1012 165:47 hrs 4 min Instrument Damage. Good Data for >13 cm/sec 350-170 18 Rupert H/39 378' Nov Nov 26 8 1031 29 8 1149 73:18 hrs 4 min Good Data 350-170 *9 Rupert 1/36 465' Nov Nov 26 8 1127 29 8 1445 75:18 hrs 4 min Good Data 330-150 tio Rupert 1/36 501' Dec Dec 7 8 1530 13 8 0910 137:40 hrs 4 min Data F a i r . P a r t i a l E l e c t r i c a l Failure 330 - 150 #11 Rupert 1/35 510" Dec Dec 7 8 1611 13 8 1030 138:17 hrs 4 min 3 weights. Good Data for High Velocity 330 - 150 TABLE I: DATA FOR CURRENT METER RUNS. 32 I n l e t . At Coal Harbour the large t i d e d i f ferences for higher high water and lower low water are i n the order of ± 0 . 3 feet and -0.6 feet , r e s p e c t i v e l y , on Tofino values . Coal Harbour has a mean t ide range of 9.0 feet and large t ide range of 13.8 feet with a mean water l e v e l of 7.0. The recorded extremes of high and low water at Tofino are 19.3 feet and -0.3 feet and are pre -sumed to be of the same magnitude for Rupert I n l e t . The t ides are of a mixed, mainly semi-diurnal type. Current data for each run are presented i n three d i a -grams: frequency of occurrence by true d i r e c t i o n , maximum v e l o -c i t y for each 1 0 ° azimuth, and u p - i n l e t down-inlet v e l o c i t y p lo t ted against time and t ides with t i d a l height and range i n d i -cated. Together the diagrams provide ins ight in to the speed of onset, maximum development, durat ion , and the rate of dec l ine of maximum currents , both up i n l e t and down i n l e t . These factors l a r g e l y govern sediment eros ion , transport and depos i t ion . The d i r e c t i o n a l frequency diagrams and the maximum v e l o c i t y diagrams are based where poss ib le on a number of complete t i d a l o s c i l l a -t ions . The d i r e c t i o n a l frequency and maximum v e l o c i t y diagrams are considered i n r e l a t i o n to the topography of the s i t e . Reas-onable harmony i s found between these three factors and leads to s e l ec t ion of a major axis general ly n e a r - p a r a l l e l to the topo-graphic s t r i k e , and assignment of a minor perpendicular a x i s . The axes are f i n a l i z e d on a b e s t - f i t b a s i s . The minor axis i s 33 then the datum l i n e for d i v i d i n g the data into u p - i n l e t and down-i n l e t components. Runs 1, 2 and 3 The o r i g i n a l instrument was used for Runs 1, 2 and 3. The f i r s t run was l o s t by e l e c t r i c a l instrument f a i l u r e . Run 2 functioned proper ly . Run 3 was l o s t when the instrument be-came lodged on bottom/ This loss i s s i g n i f i c a n t for reasons de-veloped elsewhere i n the t h e s i s , as i t occurred at a p o s i t i o n known for extensive f i l l i n g and reworking of sediments and during the predicted period of maximum bottom currents . I t i s bel ieved the instrument package was knocked or pu l l ed over by the current or a t a i l i n g s l i d e , then bur i ed . Run 2 was the f i r s t successful use of the current meter and produced perhaps the longest continuous record of bot-tom currents recorded to date i n a B r i t i s h Columbia i n l e t . The magnitude of the current and the t i d a l - r e l a t e d rhythm of the v e l o c i t i e s are establ i shed beyond question i n th i s record . Run 2 was located at a depth of 354 feet on a topo-graphic nose along the south flank of the Rupert gap. Since the bottom of the gap at t h i s l o c a t i o n i s over 500 feet deep, the currents observed may not be the same at the two l e v e l s . Data were recorded at thirteen-minute i n t e r v a l s over a twenty-eight day p e r i o d , Ju ly 12 to August 9, 197 3, with the f i r s t three days l arge ly unproductive because the instrument was obstructed. 34 Figure 8, the d i r e c t i o n a l frequency, and Figure 9, the maximum v e l o c i t i e s , are based on nine t i d a l o s c i l l a t i o n s over the period of maximum v e l o c i t i e s both up and down i n l e t (Figure 10) from low t ide at 1805 hours, J u l y 29, to low t i d e at 0930 hours, August 3. Figure 8 shows the dominance of occurrence of u p - i n l e t movement. In f a c t , Figure 10 shows a "base l eve l" for the ent i re survey to be about 10 cm/sec up i n l e t . Down-inlet currents are seen to develop and diminish i n order ly progression with the spring t i d e (Figure 10), reaching maximums i n the order of 4 0 cm/ sec (Figures99 and 10). P a r t i c u l a r l y during spring t i d e s , the i n d i v i d u a l down-inlet currents develop during the second ha l f of the f lood t i d e , then give way abrupt ly near high s lack to the maximum u p - i n l e t current of that t i d a l o s c i l l a t i o n . The intense u p - i n l e t motion i s often stronger but s h o r t e r - l i v e d than the down-i n l e t current (Figure 10). The u p - i n l e t currents reach v e l o c i -t i e s i n the order of 90 cm/sec, double those down i n l e t (Figures 9 and 10). While the down-inlet currents are quite symmetrical •with the spring t ide (Figure 10), the strong u p - i n l e t currents seem to be a funct ion of the d e c l i n i n g spring t i d e s . The e f fects of topography can be seen i n Figures 8 and 9. While the d i r e c t i o n a l frequency maxima are c lose to the topo-graphic s t r i k e , the maximum v e l o c i t y currents for both down and u p - i n l e t sweep up slope about the topographic nose on which Run 2 i s s i tua ted . In terms of sediment movement, Run 2 suggests that RUN 2: F i g u r e 8. D i r e c t i o n a l Frequency of Bottom C u r r e n t s 36 Figure 9 . RUN" 2: Maximum V e l o c i t y by D i r e c t i o n of Bottom Currents 37 — 70 cm/tec — 60 em/tec. — 30 cm/tec — 40 cm/sec 30 cm /tec — 20 cm/tec 10 cm/tec 10 cm / tec. — 20 cm/tec. — 30 cm/tec. — 40 cm/tec. — 50 cm/tec • July 13 1973 | July 14 1973 | July 15 1973 ; July 16 1973 i July 17 1973 i July 18 1973 i July 19 1973 i July 20 1973 i July 21 1973 | July 22 1973 i July 23 1973 o'o 06 12 18 00 06 J2 18 Ob 06 £ 18 o b 06 £ 18 00 06 12 18 o b 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 ob 0 6 1 2 18 o b 06 12 18 I July 24 1973 1 July 25 1973 1 July 26 1973 1 July 27 1973 | July 28 1973 | July 29 1973 1 July 30 1973 1 July 31 1973 1 August I 1973 1 August 2 1973 , August 3 1973 1 August 4 1973 1 August 5 1973 1 August 6 1973 , August 7 1973 1 August 8 1973 1 Aug. 9 > o b 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 o b 06 12 18 o b 06 12 18 o b 06 12 18 o b 06 12 18 Ob 06 12 18 O b 06 12 18 Ob 06 12 18 o b 06 12 18 Ob 06 12 18 o b 06 12 18 o b 06 12 18 o b 06 12 - 15 tt. 10 tt — 5 t l RUN 2: V e l o c i t y - Time - Tide Comparison Figure 1 0 . 38 mater ia l i n suspension at 10 cm/sec w i l l be under a long-term up-i n l e t motion. Down-inlet currents occur with increas ing v e l o c i t y re la ted to the spring t ide and move sediments of increased gra in s i z e . As the spring t ides wane, the down-inlet currents d iminish but s trong, s h o r t - l i v e d , u p - i n l e t currents move even coarser mater ia l upstream. Runs 4 and 5 Runs 4 and 5 c lose to the mine area were designed to l earn something of the l a t e r a l symmetry of the c i r c u l a t i o n . Run 5 suffered instrument f a i l u r e and while Run 8, nearby, was l a t e r success fu l , a second opportunity for a paired c r o s s - i n l e t study was not found. Runs 4 and 8 are both as far towards the head of the i n l e t as p r a c t i c a l because of i n s t a b i l i t y of the bottom due to ponding of t a i l i n g and danger of marine slumps o f f the waste rock dump. Run 4 at 258 feet , about one-half mile west and 100 feet down-slope from the t a i l i n g o u t f a l l , i s thought to be r e -presentat ive of bottom current condit ions at the o u t f a l l . I t i s also very close and about 50 feet down slope from Howard's (1970) Stat ion B which i s discussed l a t e r . Run 4 data represent nearly three days of continuous recording immediately of f bottom. The d i r e c t i o n a l frequencies (Figure 11) and the maximum v e l o c i t i e s (Figure 12) are based on data from f ive t i d a l o s c i l l a t i o n s , from high t ide at 1155 hours, 39 RUN 4: F i g u r e 1 2 . Maximum V e l o c i t y by D i r e c t i o n o f Bottom C u r r e n t s 41 20 cm/tec 15 cm/t«c 10 em/iec 5 cm/sec lOcm/uc. 13cm/tec 20cm/sec O c t o b e r 24 1973 1 October 25 1973 I October 26 1973 1 October 27 1973 i 1 : 1 : : 1 ; 1 1 1 , " H 1 i i i i . i . . . . 12 18 - . 1 : o'o 06 ; l . . . . . . . 12 • i • • 18 o'o 06 12 • i . > 18 ' * I ' 1 ' ' ' 1 ' ' 1 O'O 06 15 ft 10 (t 5 f l RUN 4: V e l o c i t y - Time - Tide Comparison Figure 13 42 October 24, to 0205 hours, October 27. The d i r e c t i o n a l f r e -quency (Figure 11) of up- and down-inlet movement i s nearly balanced, with up-slope currents more common than down-slope currents . Maximum v e l o c i t i e s (Figure 12) reach 17.7 cm/sec up i n l e t compared with 13.0 cm/sec down i n l e t . Figure 13 presents the v e l o c i t y - t i m e - t i d e data at twice the scale used for Run 2 data and at an expanded scale which i l l u s t r a t e s the previous ly discussed l i m i t a t i o n of the instrument for v e l o c i t i e s less than 7.5 cm/sec but shows that above 10 cm/sec the instrument appears to be very responsive. The net u p - i n l e t movement i s confirmed by the r e p e t i t i v e occurrence of r e l a t i v e l y stronger v e l o c i t i e s i n that d i r e c t i o n . A key observation re levant to future d i scuss ion i s tha t , while not exc lus ive , u p - i n l e t motion occurs during the f lood t ide and s i m i l a r l y down-inlet motion occurs during ebb t i d e . Net sediment motion seems l imi ted to mater ia l that can be moved by modest currents , perhaps to ha l f a knot (24 cm/sec). The net movement of the sediment w i l l be headward i n response to the d i r e c t i o n of strongest currents . Runs 6 and 7 Runs 6 and 7 are c loses t to the f lood t ide flow through Quatsino Narrows. The surface waters between the Narrows and Hankin Point are often turbulent , r e la ted to t i d a l v e l o c i t i e s at the surface over the s i l l of 6.0 knots (approximately 300 cm/ sec) on the f lood and an even greater 6.8 knots on the ebb (Can. 43 Hyd. S e r v . , 1972b). Howard (1970) attempted bottom current readings at Stat ion A (see Figure 6) d i r e c t l y o f f Hankin Point and encountered many d i f f i c u l t i e s i n pos i t i on ing the meter and i n i n t e r p r e t i n g his d i r e c t i o n a l r e s u l t . For these reasons, Runs 6 and 7 were taken as paired runs near to the mouth of the Narrows but r e l a t e c l e a r l y to Holberg and Rupert i n l e t s , r e -spec t ive ly . As w i l l be shown, unl ike the r e l a t i o n at Run 4 where the dominant motion of bottom currents i s up i n l e t , the dominant motion observed at bottom on e i ther side of the Narrows i s down i n l e t and therefore convergent. Run 6 i s the only current data co l l ec t ed from Holberg In le t s ince the incept ion of the Utah t a i l i n g d i sposa l p r o j e c t . Considerably more work i n Holberg would be usefu l i n under-standing the current regimes as they re la t e between Rupert and Holberg and would be recommended as part of any on-going study. Both the d i r e c t i o n frequency, Figure 14, and the maxi-mum v e l o c i t i e s , Figure 15, are strongly al igned down i n l e t . These f igures are based on 13 t i d a l o s c i l l a t i o n s , from low t i d e at 1630 hours, November 6, to low t ide at 0830 hours, November 13. The "spoked" e f fec t on the u p - i n l e t side of Figure 14 i s the r e s u l t of the 3 0 ° , 60° problem inherent i n reading low values , as prev ious ly discussed. Figure 15 shows the d i r e c t i o n of dominant maximum v e l o c i t i e s from 0 50° to 1 5 0 ° ; however, when 44 considered i n conjunction with Figure 14 the most consistent strong currents are demonstrably between 0 8 0 ° and 1 3 0 ° . Figure 16 emphasizes an almost t o t a l absence of any s i g n i f i c a n t up-i n l e t current while recording that gentle r e p e t i t i v e u p - i n l e t motion often occurs about low slack water. Conversely, r e p e t i -t i v e down-inlet currents occas iona l ly approaching 3/4 knot (37 cm/ sec) often tend to develop during la te f lood t i d e and p e r s i s t through high water to la te i n the ebb t i d e . Run 7 i s the c loses t s ta t ion i n Rupert In le t to Quatsino Narrows. In th i s run the d i r e c t i o n a l incl inometer was p a r t i a l l y obscured i n the photographs so that only v e l o c i t i e s greater than 13.0 cm/sec (10° i n c l i n a t i o n ) have been accepted as accurate . Values above 82 cm/sec are beyond the data contro l curve and r e -present estimates of v e l o c i t y based- on pro jec t ion of the curve. A l l three Run 7 diagrams (Figures 17, 18 and 19) are dominated by two very strong down-inlet currents both bearing about 2 2 0 ° . These two currents , c l e a r l y depicted on Figure 19, are considered separately . Since the loss of lesser v e l o c i t i e s l i m i t e d the data a v a i l a b l e , a l l observations are included i n the preparat ion of Figures 17 and 18 rather than a l i m i t e d number of t i d a l o s c i l l a t i o n s . Figures 17 and 19 i l l u s t r a t e that currents over 13 cm/sec occur more frequently down i n l e t . Figures 18 and 19 show, with the two exceptions noted, that v e l o c i t i e s i n both d i rec t ions r e g u l a r l y reach maximum i n the order of 50 cm/sec with u p - i n l e t motion s l i g h t l y stronger but of less durat ion . 46 N RUN 6 s Figure 15. • Maximum V e l o c i t y by D i r e c t i p n of Bottom Currents TO r-h 1,1 H ii n JM TO cm/sec. — 60 cm/sec. — 5 0 cm /sec. — 4 0 em/sec — 30 cm /sec — 20 cm/sec 10 cm/sec 5 0 L 15 r-V 10 cm / sec — 30cm/sec . — 4 0 cm/sec. — 50 cm/sec Nov. 6 1973 1 N o v e m b e r 7 1973 N o v e m b e r 8 1973 I N o v e m b e r 9 1973 • N o v e m b e r 10 1973 N o v e m b e r II 1973 N o v e m b e r 12 1973 . . 1 , Nov. 13 19 7 3 12 18 OX) • T I . T | 1 1 1 1 . | . 06 12 .8 0 0 06 • • ' * i i 12 18 ' o'o • 1 1 i 1 • • • • i 06 12 I'B • : o'o • 06 12 18 o'o ' 0 ' 6 . l ' 2 18 o'o 06 12 18 o'o 06 12 - 15 f t — 10 ft. - 5 f t RUN 6: V e l o c i t y - Time - Tide Comparison Figure 16. 48 49 RUN 7: F i g u r e 18. Maximum V e l o c i t y by D i r e c t i o n o f Bottom C u r r e n t s 50 r-O O _ l UJ > 111 _ J z 0. 3 70 60 SO 40 30 20 10 — 70 cm/tot — 60 cm/tec. — 50cm/MC — 40 cm/tec. — 30cm/«t — 20 c m / K C 13 cm/sec DATA ENDS K> 13 Hn. 1 o DATA STARTS 12 23 bra. Ul -I Z z * o o 10 20 30 40 30 13 cm/sec-Ul UJ Q ~1 1 1 r- - | — i 1 1 i 1 — | — r ~1 1 1 1 1 1 1 r-November 6 1973 | N o v e m b e r 7 1 9 7 3 1 November 1 12 18 O'O ' • i 06 ' ' ' ' .'2 1 t t 1 1 1 L 18 I I . . 00 06 i 12 13 cm/»ec — 20 cm/»et — 30 cm/sec — 40 cm/sec — 13 fl — K> ft 5 ft RUN 7: V e l o c i t y - time - Tide Comparison Figure 19. 51 The r e l a t i o n to t i d a l height and range i s unclear; how-ever, increase i n v e l o c i t i e s appears re la ted to substant ia l high t ide heights and/or large f lood t ide range. An examination of Figure 19 i l l u s t r a t e s that while a combination of both encourages higher v e l o c i t i e s , i t does not necessar i ly produce them, e i ther j o i n t l y or separate ly . The e f fec t of storm t ides could be an un-predic tab le but important v a r i a b l e . The rhythm of occurrence of the higher v e l o c i t i e s ( i . e . Figure 19, November 13) seems to be dominated by down-inlet motion commencing ear ly i n the onset of the f l o o d , d iminishing or absent at high s lack , then dominantly up i n l e t for the f i r s t part of the ebb t i d e . Unlike most other runs, the maximum down-i n l e t v e l o c i t i e s tend to occur at mid-f lood i n Run 7 rather than at high t ide as w i l l be shown for Runs 9 and 10. Another fea-ture of p a r t i c u l a r l y c h a r a c t e r i s t i c note i s the repeated abrupt change of d i r e c t i o n noted on Figure 19 where currents of apprec i -able v e l o c i t i e s are suddenly and repeatedly reversed, an observa-t ion which may suggest turbulence. The two strong down-inlet currents on November 8 (A) and November 11 (B) are not only the strongest currents observed i n any run but each pers i s ted for two hours. Both develop ve lo -c i t i e s i n excess of 70 cm/sec within eight minutes, with current A reaching estimated maximum v e l o c i t y of 120 cm/sec within f i f -teen minutes and current B reaching estimated maximum v e l o c i t y of 102 cm/sec i n f o r t y - f i v e minutes. However, while B occurred 52 during f lood t i d e , a time associated i n Run 7 with strong down-i n l e t currents , A occurred during ebb t i d e , a time normally of u p - i n l e t currents . Therefore, currents A and B may be of non-t i d a l o r i g i n , perhaps t u r b i d i t y currents re la ted to mine a c t i v i t y . Against a t u r b i d i t y current o r i g i n for A or B i s the fact that neither have a counterpart i n the paired Run 6 only one mile downstream. The tentat ive conclusion i s that the currents r e -f l e c t e i ther i r r e g u l a r l o c a l turbulence, l o c a l i z e d currents , or that the currents d id not go near the second meter. Runs 8 and 9 Run 8 i s paired with Run 9 (Figure 6) and i s across and s l i g h t l y down i n l e t from the t a i l i n g o u t f a l l p ipe . I t i s low on the south flank close to the axis of the trough. The d i r e c t i o n a l frequency and maximum v e l o c i t y data for f ive t i d a l o s c i l l a t i o n s , from high t ide at 1345 hours, November 26, to high t ide at 0425 hours on November 29, are summarized i n Figure 20 and 21 with the v e l o c i t y - t i m e - t i d e comparison depicted i n Figure 22. The most s t r i k i n g aspect of Run 8 i s the lack of any subs tant ia l currents (see Figure 22). No u p - i n l e t currents ex-ceed 10 cm/sec (Figure 21) although almost 50 per cent of the s l i g h t current motion i s up i n l e t (Figure 20). The down-inlet motion i s dominated by three rather s h o r t - l i v e d currents designa-ted A, B and C on Figure 22. Three minor down-inlet currents of add i t i ona l i n t e r e s t are designated a, b and c. Currents A, B and C , are a l l i n the order of 25 to 35 cm/sec and a l l have a strong i n i t i a l onset and then slacken abrupt ly . A and B occur 53 at varying pos i t ions i n the ebb, but C occurs la te i n mid- f lood . The shape of the v e l o c i t y p lo t and apparent lack of coordinat ion with t ides suggest that these features may represent small t u r -b i d i t y flows. The d i r e c t i o n of A, B and C i s s trongly oriented about 2 3 0 ° which i s ob l ique ly across the s t r i k e , but l o g i c a l for a t u r b i d i t y movement o r i g i n a t i n g on the north f lank of the i n l e t . Currents A , B and C are 30 to 45 minutes i n advance of t h e i r counterparts A", B' and C' at Run 9 (Figure 25) and are of the same general i n t e n s i t y , with A 1 and B 1 s l i g h t l y diminished. How-ever, i n Run 9 (Figure 25) these currents appear more l i k e l y to be part of the broader c i r c u l a t i o n . The evidence i s inconc lus ive . These three currents could be e i ther rather minor t u r b i d i t y currents or broader c i r c u l a t i o n currents which only touch Run 8, perhaps a marginal area , for b r i e f per iods . The three other currents , noted as a, b and c, occur at or near high t ide (Figure 22). Currents a and b have d i r e c -t ion of about 300° while c i s at 2 4 5 ° . I t i s suggested that a and b i n p a r t i c u l a r may re la t e to a tendency, discussed l a t e r , to develop down-inlet currents at bottom during f lood t i d e . I f A, B and C are el iminated as part of the general c i r c u l a t i o n by reason of t h e i r being t u r b i d i t y movements re la ted to mine a c t i -v i t y , then the maximum normal current observed i n Run 8 i s 13 cm/ sec. Unlike the d i r e c t i o n a l frequency and maximum v e l o c i t y diagrams for other runs which tend to be oriented p a r a l l e l to RUN 82 F i g u r e 20. D i r e c t i o n a l Frequency of Bottom C u r r e n t s 55 56 70 60 50 40 30 20 — 70 cm/tec. 60 cm/tec — 50 cm /tec. — 40 cm/tec — 30 cm /tec 20 cm /tec. 10 cm/sec. < 0 E o 10 20 H -i o »U|» w4IUIk jl U U I 1 / V4L 10 cm/sec 30 40 50 — 20 cm /sec. 30 cm/sec — 40 cm/tec 50 cm / sec. Nov. 26 1973 1 N o v e m b e r 27 1973 I N o v e m b e r 28 1973 1 Nov. 29 19 73 ' l i 18 o'o 0 6 l i IB o'o ' 0'6 ' ' ' ' ' l i I B ob I i T - - T " i r 1 1 r-06 ' l i 15 10 — 15 ft — 10 fl. 5 ft 2.2 2.4 2.7 RUN 8: V e l o c i t y - Time - Tide Comparison Figure 22. RUN 9 : F i g u r e 23. D i r e c t i o n a l Frequency o f Bottom C u r r e n t s RUN 9 : F i g u r e 2 4 . Maximum V e l o c i t y by D i r e c t i o n o f Bottom C u r r e n t s 59 — 70 cm/sec. — 60 em/set 50 cm/tec — 4 0 cm/tec — 30 cm/set — 20 cm/sec. 10 cm/sec. 20cm/sec. — 30 cm/sec. 40 cm/sec. - 50 cm/set Nov. 26 1973 1 November 27 1 9 7 3 I N o v e m b e r 28 1973 , , 1 , , Nov. 29 1973 "2 1 ! I i 1 I 1 1 r 18 • ' J o ' ' 1 ' i i • -06 12 18 ' • o'o ' ' 06 12 18 • o'o 06 12 15 K) — 15 ft RUN 9: V e l o c i t y - Time - Tide Comparison Figure 25. 60 the topography, i n Run 8 d i r e c t i o n a l frequency (Figure 20) i s perpendicular to topographic s t r i k e i n d i c a t i n g down-slope move-ment towards the base of the trough. This movement represents the low v e l o c i t y background of Figure 2 2 with maximum v e l o c i t i e s less than 10 cm/sec. In Figure 21 the asymmetrically oblique down-inlet v e l o c i t i e s r e l a t e to features A, B and C of Figure 22, centred about 235° with the maximum v e l o c i t i e s of 34.5 cm/sec. Bearings between 255° and 335° are assigned to a, b and related movements of Figure 22 which show r e l a t i v e l y consistent maximum v e l o c i t i e s about 12 cm/sec. The l a t t e r are the down-inlet force suggested as being related to flood t i d e s . Run 9, paired with Run 8, i s very near but s l i g h t l y up the south flank from Run 10. Similar but changing current re-lationships observed i n Runs 8 and 9 can be related to Run 10 and projected to Run 11 s t i l l further down Rupert gap. The d i r e c t i o n a l frequency and maximum v e l o c i t i e s for Run 9 are pre-sented i n Figures 23 and 24, respectively, based on the same f i v e t i d a l cycles as Run 8. Figure 25 presents the velocity-time-tide r e l a t i o n s h i p . Comparison of Figures 23 and 24 shows both f r e -quency and v e l o c i t y demonstrate strong alignment with topo-graphic s t r i k e . While the greatest d i r e c t i o n a l frequency con-centration of Figure 2 3 i s down i n l e t , the maximum v e l o c i t i e s of Figure 2 4 are strongly concentrated up i n l e t . Maximum v e l o c i t i e s up i n l e t are more than double the down-inlet v e l o c i t i e s , 70 cm/ sec compared with 30 cm/sec. In Figure 25 the maximum v e l o c i -t i e s are seen r e p e t i t i v e l y to approach 30 cm/sec down i n l e t and, 61 conversely , r e p e t i t i v e l y approach and exceed 50 cm/sec up i n l e t . While the d i r e c t i o n a l frequency i s greater down i n l e t , the strength and durat ion of u p - i n l e t currents dominate Figure 25. This i s p a r t i c u l a r l y true i f minor v e l o c i t i e s of less than 10 cm/ sec are ignored. In terms of sediment movement, the u p - i n l e t currents i n Run 9 are both stronger and of longer durat ion than the down-inlet currents and therefore the net sediment t rans -port of near-bed and bed-load mater ia l must be up i n l e t . At the same time i t must be noted that the strong u p - i n l e t motion occurs not on the f lood t ide but on the ear ly ebb t i d e , s t a r t i n g abrupt-l y at or jus t preceding the turn of the high t i d e . Using Figure 25, a general case can be developed for the observed bottom currents of the Rupert gap. As with most general izat ions there i s a notable exception: the period about high t ide at 1500 hours on November 28, marked c 1 , shows no assoc ia t ion with the predicted currents . Figure 25 i s dominated by the sudden break from near-maximum down-inlet currents , marked X, to near-maximum u p - i n l e t currents , marked Y. This occurrence s l i g h t l y precedes a high t i d e , with the v e l o c i t i e s up i n l e t about double the v e l o c i t i e s down i n l e t . Examining bottom currents i n r e l a t i o n to a t i d a l o s c i l l a t i o n s t a r t i n g at the ebb t i d e , i t i s found that the ear ly f lood i s often associated with a gentle u p - i n l e t current of long durat ion , marked d , which has often been preceded by a gentle l o n g - l a s t i n g down-inlet current la te i n the f lood t i d e , marked f_. Occas iona l ly , although the current d i r e c t i o n has not reversed from f_ to d the tendency to 62 do so can be noted by a decrease i n v e l o c i t y , with examples noted respec t ive ly as f_' and d 1 . As the f lood continues from d , s l i g h t u p - i n l e t current i s reversed to down-inlet then increas ing and culminating at X. Features a, b and poss ib ly c of Figure 22 would be re la ted to th i s down-inlet v e l o c i t y bu i ld -up but never reach anrt X-Y s i t u a t i o n at Run 8. In Run 9, t h e i r equivalents a' and b' are intercepted by the strong X-Y movement. The current sequence for Run 9 s t a r t i n g at ebb t ide i s : gentle up i n l e t '(d) revers ing to down i n l e t , then increas ing (X), sudden r e v e r s a l to u p - i n l e t maximum v e l o c i t y (Y), then diminishing on the ebb u n t i l i t becomes a gentle down-inlet current (f_) . Three values S, T and U which appear on Figure 24 as strong up-f lank currents might be held suspect as being spurious while Figure 23 would e s t a b l i s h currents i n these d i rec t i ons as seldom occurr ing . However, Figure 25 re la tes these as short -l i v e d precursors to the abrupt onset of maximum u p - i n l e t current as high s lack t ide i s approached. The r e l a t i o n s h i p suggests that as X i s approached considerable "pressure" i s b u i l t up to reverse the motion from down i n l e t to up i n l e t as the t ide s lackens. Runs 10 and 11 Runs 10 and 11 are p a i r e d , with Run 10 c lose to Run 9 and Run 11 about h a l f a mile further down i n l e t . These runs i n -clude the maximum year ly high t ide of 13.4 feet and a minimum ebb t ide of 0.3 feet , with a t i d a l range of 13.1 feet on ebb and 63 11.1 on flood. If volume of water i n the t i d a l prism i s the dominant c r i t e r i o n governing the bottom current, then maximum currents should occur i n t h i s period. For t h i s reason Utah Mine scheduled a dye experiment as an aid to t u r b i d i t y studies, discussed i n Chapter V. While Run 10 i s marred by p a r t i a l f a i l u r e of the i n -strument, the gross features of the current are well established by the intermittent data c o l l e c t e d over the entire period. Although down-inlet motion i s appreciable, the domi-nance of the up-inlet motion i s c l e a r l y i l l u s t r a t e d i n Figures 26, 27 and 28. The same organization, order and magnitude noted for the loc a t i o n by Run 9 ten days e a r l i e r i s evidenced by Run 10 with the exception that the down-inlet current of flood tides reaches maximum v e l o c i t i e s nearly double those of Run 9. This increase i n v e l o c i t i e s i s thought attributable to the increased t i d a l height and range. The up-inlet currents again dominate as they did i n Run 9. While the v e l o c i t i e s of the up-inlet currents are s l i g h t l y stronger, they have not increased i n proportion to the down-inlet currents, but appear to be more sustained than i n November. An unusual event i s depicted (Figure 28) on December 8, at 0600 hours c l o s e l y following a low t i d e . The entire event was b r i e f , l a s t i n g between 16 and 20 minutes. While a maximum down-inlet v e l o c i t y of 55.7 cm/sec i s similar to other maximum 64 RUN 10: F i g u r e 27. Maximum V e l o c i t y by D i r e c t i o n o f Bottom C u r r e n t s 66 kl 6 0 r TO 60 50 40 30 20 10 • BO cm/see. — TO cm/tec — 60 em/tec — 50 cm/tec — 40 cm/tec — 30 cm /sec 20cm/tec 10 cm/tec. a o _ i Ul r -> 3 z $ o o -t • i -i 1 1 1 1 1 0 Ul I -Ul o 10 20 30 40 50 vU 1/ U L_J ~l " ' r -i rt—i 1 1 r- -i j i 1 1 r i I 1 1 r - I i i 1 r •'• i j "" 'T i i 10 cm / sec — 20 cm/sec. 30 cm /sec — 40 cm/ sec. 50 cm / sec D e c . 7 1973 i D e c e m b e r 8 1 9 7 3 D e c e m b e r 9 19 7 3 D e c e m b e r 10 1 9 7 3 D e c e m b e r II 1 9 7 3 I D e c e m b e r 12 1 9 7 3 , , , ! • D e c . 13 1 9 7 3 18 a o 0 6 12 is d 0 0 6 12 : 1 1 | 1 1 18 < > . i o'o 0 6 12 18 i ' I t i 0 0 ' ' d e . ' 2 i 18 o 'o i i | i i i i i i 0 6 12 18 i i i . o'o j i i i i 0 6 ' 12 15 ft — 10 ft. — 5 fl. RUN 10: V e l o c i t y - Time - Tide Comparison Figure 28. 67 6 8 RUN 1 1 : F i g u r e 30. Maximum V e l o c i t y by D i r e c t i o n o f Bottom C u r r e n t s 6 9 70 i — 70 cm/see. 60 I — 60 cm/tec 50 I — 50 cm/tec 40 30 I 30 cm/tec 20 20 cm/tec a. >- => 10 10 cm/tec o o 1 1 r • • r UJ r-> 3 10 • 10 cm / tec o o U J I — 20 30 40 50 Dec. 7 1973 D e c e m b e r 8 1973 D e c e m b e r 9 1 9 7 3 D e c e m b e r 10 1973 i ! <~ 18 -DT-r-D e c e m b e r II 1973 D e c e m b e r 12 1973 20cm/tec . 30cm/tec . 4 0 cm/tec. — 5 0 cm/sec Dec. 13 1973 - T 1 n — i 1 1 1 — i — t — 18 O'O I — ' — 1 — i -06 12 18 00 06 12 00 06 12 18 00 06 12 18 06 i r-12 18 O'O - T 1 1 I 06 Ul Q 15 r~ 10 h 12.6 13.1 13.4 13.3 130 — 15 f t RUN 11: V e l o c i t y - Time - Tide Comparison Figure 3 1 . 70 down-inlet c u r r e n t s , i t appears out of phase being u s u a l l y r e -l a t e d to the t u r n of the high t i d e . Before and a f t e r the event the currents were r e l a t i v e l y n e g l i g i b l e . F i r s t the meter sprang dr a m a t i c a l l y _ a n d r e g i s t e r e d 35.5 cm/sec bearing 105°, a bearing s t r o n g l y o b l i q u e to the s t r i k e and u p - i n l e t , then i n successive four-minute stages i t read 17.7 cm/sec at 195°, down i n l e t but s t i l l s t r o n g l y o b l i q u e , then 35.2 em/sec and 55 cm/sec at 215°, then diminished to 21.6 cm/sec along s t r i k e at 235°. Despite the r e p r e s e n t a t i o n of Figure 28, the event i s e s s e n t i a l l y a down-i n l e t movement w i t h the i n i t i a l sway of the instrument up i n l e t to 105° taken as a momentary o v e r - r e a c t i o n . The cu r r e n t develop-ed i n c r e a s i n g v e l o c i t y to at l e a s t 55.7 cm/sec and g r a d u a l l y assumed a near-normal down-inlet course, then d i s s i p a t e d r a t h e r q u i c k l y . The most obvious explanation i s a t u r b i d i t y c u r r e n t and i f only one instrument was i n s t a l l e d t h i s would s u r e l y be the co n c l u s i o n . However, Run 11, only h a l f a m i l e down i n l e t and i n the narrow confines of Rupert gap, does not record even a t r a c e of the event. The o r i g i n of the event remains i n question; e i t h e r i t i s spurious at Run 10 r e l a t e d to unknown causes, or the t u r b i d i t y c u r r e n t d i d not reach or bypassed Run 11. Run 11 was an attempt to measure any strong c u r r e n t s which might occur during the period of maximum annual t i d e s . Un-f o r t u n a t e l y , none occurred. The instrument had been f i t t e d w i t h e x t r a weights to extend i t s range to three knots. Data f o r l e s s than 10° d e f l e c t i o n (23.5 cm/sec) were discarded s i n c e they are not i n the designed range f o r the modified instrument. A l l 71 values i n excess of 23.5 cm/sec ( 1 0 ° ) were used i n Figures 29, 30 and 31. The dominance of the down-inlet c u r r e n t i n Run 11 i s w e l l i l l u s t r a t e d i n a l l three diagrams. The eastern o r i e n t a t i o n of the u p - i n l e t c u r r e n t (Figure 30) i s thought t o r e f l e c t the d i r e c t i o n of the cu r r e n t as i t d e f l e c t s o f f Hankin P o i n t . Run 11 c o r r e l a t e s w e l l w i t h p o i n t s of maximum v e l o c i t i e s i n Run 10 and bears strong resemblance to Run 7 i n the r e l a t i o n s h i p of up-i n l e t to down-inlet c u r r e n t s . In summary, i t appears t h a t a l l runs w i t h the excep-t i o n of Run 4 belong to the same sector of the cu r r e n t regime of Rupert I n l e t . The currents i n Run 4 are i n phase w i t h the t i d a l prism moving up i n l e t on f l o o d t i d e and down i n l e t on ebb t i d e . The other s t a t i o n s are t o va r y i n g degrees i n counter phase w i t h the t i d a l prism, w i t h maximum down-inlet c u r r e n t s preceding the high t i d e and s h i f t i n g r a t h e r a b r u p t l y to maximum u p - i n l e t currents at high s l a c k or e a r l y ebb t i d e . Maximum u p - i n l e t currents are best developed i n the upper p a r t of Rupert gap i n Runs 2, 9 and 10 where they reach v e l o c i t i e s i n excess of 1.5 knots. Maximum down-inlet c u r r e n t s are best developed i n the lower p a r t of Rupert gap i n Runs 7 and 11, o f t e n reaching one knot and near the Narrows l o c a l l y exceeding two knots. The i n -t e n s i t y of the currents i s gr e a t e s t during s p r i n g t i d e s . Several p o s s i b l e events are observed t h a t may be t u r b i d i t y cur-r e n t s , but none can be v e r i f i e d . Indeed, the weight of evidence i s a gainst a t u r b i d i t y o r i g i n f o r most of the f e a t u r e s . 72 Observations of Other Workers Two other studies r e l a t e d to current movement i n Rupert In le t have been made since a t tent ion has been focussed on that i n l e t by the mine t a i l i n g d i s p o s a l program. Howard (1970) made d i r e c t current measurements as part of a B r i t i s h Columbia Re-search p r o j e c t . Drinkwater (1973), c o l l e c t e d f i e l d data using thermal microstructure observations as evidence of currents , then made a t h e o r e t i c a l model of the movement of water bodies during t i d a l exchange between Quatsino Sound and Holberg-Rupert i n l e t s . Both these works are supportive of the present study which adds d i r e c t observation of bottom current v e l o c i t i e s but leaves to continuing conjecture the s tructure and extent of currents within the water column. The main object of Howard (1970) was to measure cur -rents at two l o c a t i o n s , marked A and B on Figure 6, with p a r t i c u -l a r emphasis on the bottom currents . At Stat ion A, depth 520 feet , he made readings at the 30, 100, 200, 350 and 490 foot l e v e l s . Because he was working from shipboard with the meter sus-pended on a weighted l i n e which was observed to de f l ec t i n the current as much as 2 0 ° , Howard noted h is depths as nominal. Howard's v e l o c i t i e s at S tat ion A are not less than 30 feet o f f bottom and may be considerably more, quite far removed for use i n the study of sediment t ransport . Howard measured maximum v e l o -c i t i e s , f ind ing v e l o c i t i e s between 1.0 and 1.4 knots at various l e v e l s . The maximum v e l o c i t y at 490 feet was 1 knot recorded one hour before high t i d e . Perhaps s i g n i f i c a n t are the mean current 73 values which increase from 0.18 knots at 350 feet to 0.22 knots at 490 feet as bottom i s approached. At the 490 foot l e v e l , Howard's data were taken i n seven 30-minute i n t e r v a l s over a twenty-four hour per iod . Examination of Figure 19 from the nearest run of the present study indicates that a one-knot cur-rent as observed by Howard i s a sporadic but normal occurrence during spring t i d e s . Howard could not resolve current d i r e c t i o n . He found the currents unsteady i n v e l o c i t y and h igh ly v a r i a b l e i n d i r e c -t i o n and concluded that bottom-mounted current meters operating over longer periods and with an intermediate s t a t i o n between A and B were necessary to unravel the problem of current d i r e c t i o n . For the bottom currents th i s has l a r g e l y been done during the present study. Re-examination of Howard's d i r e c t i o n a l data for the 4 90 foot l e v e l at Stat ion A, indeed, indicates that the d i r e c t i o n swings both abruptly and widely , but there i s a de-f i n i t e preference for southerly and westerly o r i e n t a t i o n . This type of motion confirms the observations of Run 7 (Figures 17, 18 and 19). At Stat ion B with a depth of 204 feet and very c lose to Run 4, Howard co l l ec t ed data at 20, 90 and 190 feet . He r e -corded 130 minutes of data i n 16 sets over 24 hours from the 190 foot l e v e l . Again , he found the d i r e c t i o n of current movement too var iab l e to warrant i n t e r p r e t a t i o n . Current v e l o c i t i e s were less than at Stat ion A and also general ly lower at depth than at 74 the surface l a y e r . However, h i s data indicate that for ten of the s ixteen time in terva l s the maximum bottom current v e l o c i t i e s were greater than those i n mid-column, exceeding 0.20 knots i n 11 i n t e r v a l s and recording a 0.41 knot maximum. This maximum bottom v e l o c i t y compares with maximums 0.35 knots i n mid-column and 0.58 knots for surface currents . S i g n i f i c a n t l y , the 0.41 knot current was a northward current occurr ing i n mid-f lood t ide and compares with a 0.35 knot northwesterly maximum current i n the present study. Drinkwater (1973) through an examination of the r e l a -t i v e water propert ies both ins ide and outside the Quatsino Narrows presents t h e o r e t i c a l grounds for t i d a l mixing i n Rupert and Holberg i n l e t s , makes mathematical cons iderat ion of the energy requirements, then establ ishes f i e l d evidence of the process through observation of the patterns of minute thermal contrasts found i n the water column. In h i s synthesis of oceanographic data he u t i l i z e s a l l p r i o r data inc lud ing the monthly surveys of s a l i n i t y and temperature by Mine personnel to June, 197 2. Drinkwater i l l u s t r a t e s that there i s a s u f f i c i e n t l y large water volume exchange and su i table turbulence i n the Quatsino Narrows to ensure exce l lent mixing of waters entering on the f lood and leaving on the ebb (Figure 32). The f lood t ide mixing produces water denser than the surface water of Holberg-Rupert i n l e t s . The f lood water sinks to i t s density l e v e l upon entering Holberg-Rupert while the less dense ebb-t ide water moves 75 After Drinkwater (1973) Order of Increasing Density E, A, D, F, B, C Figure 32. Schematic Diagram Showing Flow Conditions Between Quatsino Sound and the Rupert-Holberg Basin During (a) Flood Tides and (b) Ebb Tides 76 down Quatsino Sound at or near the surface . Drinkwater suggests that the low d isso lved oxygen l eve l s i n the water coming i n on the f lood during the summer and f a l l of September 1972 may i n -dicate the in troduct ion of dense water o r i g i n a t i n g from upwell ing along the cont inenta l she l f . The r e l a t i o n s h i p i s perhaps more complicated as discussed i n Chapters II and V. Drinkwater's thermal microstructure observations sup-port the bottom current data of the present study even though his are at times of intermediate t i d e . Opposite the Narrows he found zones of intense s t i r r i n g extending to 90 metres, the maximum depth inves t igated . Up both Holberg and Rupert i n l e t s , he noted s t i r r i n g below the thermocline at about depths of 7 metres and 30 metres which diminished up i n l e t . U p - i n l e t motion i n th i s zone extended i n Rupert In le t to at l eas t o f f the mine s i t e and s i m i l a r l y proceeded up Holberg In le t to the Straggl ing Is lands . Deep s t i r r i n g was noted at 90 metres i n Rupert gap near Runs 9 and 10, and at 57 metres i n m i d - i n l e t between Runs 4 and 5. The s t i r r i n g was found to vary hourly as wel l as d a i l y . The data co l l ec ted i n March 1971 ind icate r e l a t i v e l y shallow u p - i n l e t i n -trus ions with further thermal interfaces at depth. Drinkwater speculates that away from the immediate area of turbulent t i d a l mixing, mixing proceeds by "pressure gradient currents". Discussion Intrus ion of f l o o d - t i d e water at various depths be-neath the surface water has been discussed by many workers p r i o r 77 to Drinkwater for both deep and s h a l l o w - s i l l e d B r i t i s h Columbia i n l e t s . Pickard and Giovando (1960) use the term "advection current" for the i n t r u s i o n of water which r e s u l t s i n the rep lace -ment of 'deep water ' , not neces sar i ly 'bottom water 1 , i n a gen-e r a l estuarine fashion for d e e p - s i l l e d i n l e t s . Davis (1960) r e -cognized the modified je t nature of the f lood t ide even over the r e l a t i v e l y deep (63m) inner s i l l of Knight In le t which with maxi-mum v e l o c i t i e s at the s i l l of 120 cm/sec (compared with 300 cm/ sec at Quatsino Narrows) c a r r i e s f l ood- t ide water wel l up the i n l e t . Pickard and Rodgers (1959) measured t i d e - r e l a t e d o s c i l -l a tory near-bottom currents behind the inner s i l l at Knight In le t which diminish i n magnitude progress ive ly up i n l e t but continued a net u p - i n l e t motion. L a s i e r ' s (1963) work on the s h a l l o w - s i l l e d i n l e t s of the J e r v i s In le t system, i s p a r t i c u l a r l y pert inent to the present study as he appears to be the f i r s t to theorize the down-inlet counter motion at depth which must accompany the i n t r u s i o n of the f lood t ide water i n mid-column. He theorizes that the depth of i n t r u s i o n of the flood-water i s contro l l ed not only by r e l a t i v e density but also by the nature of the t i d a l j e t . Indigenous water above the i n t r u s i o n w i l l be c a r r i e d headward while water below the i n t r u s i o n w i l l be forced down i n l e t . The down-inlet motion described by Las i er character ized a l l but Run 4 of the current meter observations. The present work may be the f i r s t to gather s t a t i s t i c a l information on the bottom water motion since a l l but Run 4 f i t th i s case. Not discussed by Las ier i s 78 the fac t that the bottom down-inlet current must eventual ly mount the ins ide of the s i l l and oppose the t i d a l j e t ' s tendency to "hug" the bottom. This i s a p a r t i c u l a r l y important aspect of the present study since i t sets the stage for s t i r r i n g t u r b i d i t y from the bottom and lower water column upwards into the f lood water, r e s u l t i n g i n occas ional surface observation of mine-originated d e t r i t u s i n the Hankin Point area on f lood t i d e . A genera l i za t ion of the current regime of the Holberg-Rupert basin can be made from the present data . However, since the balance of the system changes d a i l y and monthly and since the data are based on a ser ies of spring t ides during part of the year , the general ized case may be appl icab le only to spring t i d e s . Figures 33 and 34 present the genera l i za t ion for the f lood and ebb t i d e s . The i n t r u s i o n of the f lood water prism "D" drives the surface water "E" headward together with that part of "F" less dense than "D". Below the i n t r u s i o n , the bottom water moves mouthward and up the s i l l but stays i n the i n l e t . On ebb t ide the surface water moves mouthward, the i n t r u s i o n loses i t s d r i v e , but the bottom water moves r a p i d l y up i n l e t dr iven by pressure gradients r e s u l t i n g from the termination of the i n -t r u s i o n . Under the bottom current regime, sediments are moved down i n l e t on the f lood t ide but the persistence of gentle up-i n l e t motion plus strong u p - i n l e t currents on ebb t ide ind icate most of the natura l sediment i s reta ined with in the Rupert basin above Rupert gap. However, because of t h e i r abundance, sub-s t a n t i a l amounts of t a i l i n g may s l i p through during lesser t ides Order of Increasing Density E , A , F ' , D, F " , B, C Figure 33. Schematic Diagram Showing Flood Tide C o n d i t i o n . Modif ied a f t er Drinkwater (1973) Figure 3 4 . Schematic Diagram Showing Ebb Tide Condit ions 00 o r Order of Increas ing Density E , A , F , D, B , C Figure 35. Schematic Diagram for Maximum Density Flood Tide 00 82 or i n t u r b i d i t y c u r r e n t s . The p e r i o d of g r e a t e s t sediment t r a n s p o r t i s b e l i e v e d to occur when the d e n s i t y of the f l o o d - t i d e water approximates or exceeds the d e n s i t y of the indigenous water. This s i t u a t i o n i s hypothesized and presented i n Figure 35 but so f a r has not been observed. Under these c o n d i t i o n s the t i d a l j e t f o l l o w i n g i t s n a t u r a l p r e d i l i c t i o n t o hug the bottom i n t e r f a c e , w i l l d i s p l a c e a l l the indigenous water headward so t h a t no u n d e r l y i n g down-i n l e t c u r r e n t can develop. The combination of improved condi-t i o n s f o r maintenance of the j e t , g r a v i t a t i o n a l b e n e f i t of greater d e n s i t y , and the f u l l f a l l over the s i l l suggest maximum v e l o c i t y f o r the i n t r u d i n g f l o o d water. F u r t h e r , as t h i s bottom-t r a v e l l i n g i n t r u s i o n moves up i n l e t i t s t i l l has r e s i d u a l turbu-l e n t motion. These f a c t o r s of v e l o c i t y and turbulence g r e a t l y enhance i t s e r o s i o n a l c a p a c i t y . The occurrence and time of bottom-flushing d e n s i t y cur-rents are unknown but Drinkwater (197 3) reasons them to c o i n c i d e w i t h a time of decreased run-off which would r e s u l t i n denser waters running through Quatsino Narrows. As p r e v i o u s l y d i s -cussed (Chapter I I ) , t h i s would agree w i t h s t u d i e s of Tofino I n l e t where Coote (1964) found t h a t i n t r u s i o n of dense water occurred i n August or September of dry years only. Drinkwater suggests t h a t the process of i n c r e a s i n g the d e n s i t y of the bottom water i n Holberg-Rupert i s probably gradual, o c c u r r i n g through a s e r i e s of t i d e s . G e o l o g i c a l l y , t h i s r e s u l t s i n the optimum con-83 d i t i o n s of a ser ies of u p - i n l e t bottom currents o r i g i n a t i n g at Quatsino Narrows, u n t i l the bottom density f i n a l l y exceeds the in truding water. The v e l o c i t y of the maximum-density in truding currents would be greater than any resu l tant pressure gradient current be-cause the volume of water i n the i n l e t i s greater than the volume of in t rud ing water. Since the greatest current v e l o c i t i e s meas-ured i n Rupert In le t to date are 1.4 knots by Howard (1970) from surface to 350 feet at Stat ion A and an estimated 2.5 knots on bottom i n Run 7 and since the in truding water passes over the s i l l at a maximum v e l o c i t y of 6 knots, turbulent u p - i n l e t bottom cur-rents i n excess of 2 knots but less than 6 knots can be predicted to sweep up Rupert In le t during spring t ides i n la te summer, p a r t i c u l a r l y i n dry years . While the frequency, v e l o c i t y and durat ion of these bottom-flushing currents remain unobserved, aspects of t u r b i d i t y , sedimentation and the seismic p r o f i l e s give evidence of t h e i r presence. Even the b u r i a l and loss of Run 3 during ear ly September spring t ides may we l l be a t t r ibuted to these currents . Davis (1960) observes that : "the e f f ec t of t i d a l v a r i a t i o n s are on occasion greater i n a few hours than the sea-sonal ones i n a whole year". This may be p a r t i c u l a r l y true from a sedimentation point of view for s h a l l o w - s i l l e d i n l e t s . 84 CHAPTER IV SEISMIC SURVEYS In a marine i n l e t , the d i s p o s i t i o n of sediments i n r e l a t i o n to topography r e f l e c t s the net r e s u l t of the several processes c o n t r o l l i n g erosion and sedimentation. Continuous seismic r e f l e c t i o n p r o f i l i n g (C.S .P . ) provides a v i s u a l means of r e l a t i n g surface and subsurface geology to topography, making i t a most e f f ec t ive t o o l i n the present p r o j e c t . P r o f i l e s r e -corded p r i o r to mine a c t i v i t y r e f l e c t the long-term e f fec t of the oceanographic regime upon natura l sedimentation. P r o f i l e s recorded subsequent to mine a c t i v i t y show changes i n topo-graphy and sedimentation r e f l e c t i n g the short-term r e l a t i o n s h i p between supply of t a i l i n g , topography and bottom currents . Fut -ure seismic surveys at regular i n t e r v a l s , part of the continuing monitoring program, w i l l become an increas ing ly e f f ec t ive too l to evaluate these r e l a t i o n s h i p s , measure the changing d i s t r i b u -t i o n and pred ic t f i n a l d i s p o s i t i o n of the mine-originated s e d i -ments . Procedure To date, three seismic surveys have been run. The f i r s t survey i n March 1971 preceded mine production which s tarted i n October 1971. The second survey during September 1972 showed r e -su l t s of the f i r s t year's dumping of about 6,500,000 tons (Evans, 1973) of t a i l i n g and a l i m i t e d amount of waste rock. By the time 85 of the t h i r d survey i n September 1973, mine depos i t ion i s e s t i -6 6 mated at 16.8 x 10 tons of t a i l i n g and 48 x 10 tons of waste rock ( P e l l e t i e r , 1974a). The o r i g i n a l seismic survey was so arranged that i t could be r e a d i l y repeated by reference to recognizable features on shore. The survey (Figure 36) included an a x i a l p r o f i l e (Section 1) extending from the head of Rupert In le t past Hankin Point to Norton Po int , about halfway'up Holberg I n l e t . Another a x i a l p r o f i l e (Section 18) ran from Hankin Point through Quatsino Narrows into Quatsino Sound. Transverse sections across Rupert In le t s t a r t i n g at the head, were taken down i n l e t i n the fo l low-ing order: 2 ,3 ,4 ,5 ,6 ,8 ,9 ,11 ,13 ,12 ,14 . In the lower reach of Holberg In le t transverse Sections.16 and 17 were taken during the f i r s t survey, with transverse Sections 19 and 20 added during the second survey. An a d d i t i o n a l transverse s ec t ion , Section 21, of f the t a i l i n g o u t f a l l between Sections 8 and 9, was taken during the second and t h i r d surveys. The median sect ion (Section 1) , not performed i n the second survey, was repeated i n 1973 from the head of Rupert In le t to of f Coal Harbour. Although not t o t a l l y repeated by each subsequent survey, the basic g r i d represents some 35 l i n e miles of seismic c o n t r o l . The equipment (Evans, 1972) owned by the Univers i ty of B r i t i s h Columbia and operated by technicians and s ta f f of the Department of Geologica l Sciences, cons is ts of an EGG Power Supply Model 2 32A, an EG&G Trigger Capacitor Model 231-H, an 86 EG&G Boomer Model 2 36, a B o l t Hydrophone A r r a y Model 7xMP-4, a B o l t A m p l i f i e r F i l t e r Model PA-7, and a G i f f t Graphic Recorder Model GRD-19-C. For the second and t h i r d surveys a c u s t o m - b u i l t hydrophone a r r a y , c u s t o m - b u i l t a m p l i f i e r and EPC Graphic Recorder Model 4100 r e p l a c e d the r e s p e c t i v e i n i t i a l equipment (MacDonald, 197 4). The depth of p e n e t r a t i o n and r e s o l u t i o n improved wi t h each succeeding survey. U n f o r t u n a t e l y , the s c a l e s , both v e r t i c a l and h o r i z o n t a l , were not i d e n t i c a l f o r each survey, making com-p a r i s o n d i f f i c u l t . T h i s r e s u l t e d from the change from G i f f t to EPC r e c o r d e r s , made p a r t l y t o improve the q u a l i t y of the r e c o r d s . I n t e r p r e t a t i o n and D i s c u s s i o n The t r a n s v e r s e s e i s m i c s e c t i o n s of the 1971 survey of Rupert I n l e t are assembled as F i g u r e 37, of the 1972 survey as F i g u r e 38, and of the 1973 survey as F i g u r e 39. The l o n g i t u d i n a l s e c t i o n s from the head of Rupert I n l e t t o o f f Coal Harbour taken d u r i n g the 1971 and 1973 surveys are presented as F i g u r e 40A and 40B, r e s p e c t i v e l y . Transverse s e c t i o n s of Holberg I n l e t taken i n 1972 are presented as F i g u r e 41. While the l o n g i t u d i n a l and t r a n s v e r s e s e c t i o n s show v a r i a t i o n s caused by p o s i t i o n i n g and s c a l e d i f f e r e n c e s , comparisons from s e c t i o n t o s e c t i o n and survey to survey can r e a d i l y be made. The asymmetry of the upper Rupert b a s i n i s s t r i k i n g l y e v i d e n t i n F i g u r e s 37, 38 and 39. T h i s asymmetry, as i n i t i a l l y p resented i n F i g u r e 37, was a s c r i b e d by Evans (1972) as evidence of a s o u t h - t i l t e d h o r s t running p a r a l l e l to the a x i s of the i n -8 7 + 1 + 2 + 3 + 4 + A i i 1 i + - + - + - 4 '— + B • i + - + - 4 - 4- \. + C i 1 + - + - 4 - 4-D i 1 1 i + - + - 4 ~ '+. - 4-E 1 1 1 + - + - 4 - + — + F i 1 1 1 + . - 4 - 4 - + - 4-6 i 1 1 1 + - + - 4- > + - 4-H i 1 1 1 + - 4 - 4- - 4- - 4-1 1 1 1 1 + . - 4 - + - + - 4-1 l 1 1 + - + - 4- - 4- - 4-K 1 1 1 1 + - 4 - + - + - + L 1 1 1 i + - + - + - + - + M 1 1 1 i + - 4 - 4- - + - + 49 + 5 0 + A + B 4-c 4-. D 4-E + F + G + H + I + J + K + L 4. M 4 Figure 36. HEAD RUPERT ' IN LET Continuous Seismic Ref lec t ion Prof i l e s , March 1971 Figure 37. HANKIN PT. HEAD RUPERT ' IISSLET Continuous Seismic. Ref lec t ion P r o f i l e s • September 1972 ' Figure. 38 . HANKIN PT. HEAD R U P E R T I N L E T Continuous Seismic Ref lec t ion September 1973 Figure 39. P r o f i l e s r- Sea Level 300 Ft. H O L B E R G I N L E T QUATSINO NARROWS R U P E R T I N L E T u (rj Sea Level -i ro r-CTl U 0) Xi (U - P Cu 0) cn to <u r H •H in o C O •H -p O a) •H IH <D IX o - H e to •H (1) W cn o c - P C . O Longitudinal P r o f i l e s of Rupert Inlet 92 HANKIN PT. F i g u r e 41 H O L B E R G I N L E T C o n t i n u o u s S e i s m i c R e f l e c t i o n P r o f i l e s . September 1972 Figure 42. Interpretat ion of C . S . P . Line 9 from September 1973 Survey U l 94 l e t . The transparent zone against the north flank and apparent draping of sediments on the proposed south f a u l t near the bottom of the trough seemed to support the str u c t u r a l argument. Evans (1972) noted that the i n c l i n e d sediments "could possibly be the r e s u l t of a peculiar t i d a l exchange" but opted for the s t r u c t u r a l int e r p r e t a t i o n . The alternate i n t e r p r e t a t i o n — t h a t the sediment d i s t r i b u t i o n as depicted i n Figure 37 was the r e s u l t of controls of sedimentation—was t h e d i n i t i a l s t a r t i n g point of t h i s project. The second and t h i r d seismic surveys have removed many of the uncertainties a r i s i n g from the i n i t i a l survey. The g l a c i a l l y scoured U-shape of the basement t e r r a i n i s apparent i n Figures 37, 38 and 39. Three d i s t i n c t sedimentary units, d i s -cernible overlying seismic basement, are defined i n Figure 42 (transverse Section 9 of Figure 39). Seismic basement, well de-fined on the awalls of the i n l e t (Figure 42), becomes less c e r t a i n in the trough as spurious parabolic r e f r a c t i o n s mask r e f l e c t i o n s and the l i m i t of resolution i s approached (Tucker and Yorston, 1973). In the a x i a l area f l a t - l y i n g strata with a d i s t i n c t i v e uniform thin-layered signal are r e a d i l y i d e n t i f i e d and defined as Unit B. Above the f l a t - l y i n g Unit B a wedge-shaped section of i n c l i n e d sediments defined as Unit A extends from the axis of the trough to well up the northern slope of the i n l e t . Unit A appears to have been progressively deposited against the northern flank. Within Unit A at the base of the north wall i s a dark patchiness, believed due to d i s t o r t i o n of the bedding planes by i n c i p i e n t slumping which pre-dates mine a c t i v i t y as evidenced by 95 undisturbed over ly ing upper Unit A beds. T a i l i n g from the nearby o u t f a l l l i e conformably and l a r g e l y ind i s t ingu i shab ly on the t i l -ted Unit A. However, i n the axis of the trough the t a i l i n g can be seen p i l i n g up as the toe of the t a i l i n g wedge. At the base of the sect ion there i s a suggestion of an a d d i t i o n a l but poorly defined sedimentary u n i t , Unit C, which over l i e s basement and underl ies the f l a t - l y i n g Unit B. This u n i t , which r e f l e c t s a strong d i s j o i n t e d s u b p a r a l l e l s i g n a l , may comprise i n f i l l i n g gravels of ear ly p o s t - g l a c i a l depos i ts . It appears to dominate the lower trough i n Section 2 but elsewhere i s observed only s p o r a d i c a l l y . Unit C may not be a def inable u n i t , can be d i f f i -c u l t to d i s t i n g u i s h from basement and adds l i t t l e to the present study. Unit B, the "thin-bedded" s i g n a l , extends almost con-t inuous ly from Section 3 to near Section 17 (Figures 39 and 40B). While e s s e n t i a l l y f l a t - l y i n g i n transverse s ec t ion , i n l o n g i t u d i -nal p r o f i l e (Figure 40B) the s t r a t i f i c a t i o n i n Unit B dips gently and evenly westward from the upper part of Rupert In le t to the lower reach of Holberg I n l e t . I t i s bel ieved that Unit B i s the "gray clay" (Chapter V) recovered i n cores along the axis of the trough from midway between Hankin Point and Coal Harbour i n Holberg In le t to opposite the mine s i t e i n Rupert I n l e t . The l o n g i t u d i n a l sections of Figure 40A and 40B are h e l p f u l i n i n t e r p r e t i n g the d i s t r i b u t i o n and r e l a t i o n s h i p of Units A and B. Figure 40A shows that the topographic p r o f i l e near the head of Rupert In le t from transverse Sections 2 to 9 dips u n i -96 formly and gently westward down the i n l e t . The uppermost s t ra ta i n th i s area are Unit A , over ly ing intermit tent Unit B. Pro-ceeding down i n l e t , the dip of the p r o f i l e steepens from Section 21 to 13. This steepening may be p a r t i a l l y apparent but also p a r t l y r e a l and d i r e c t l y re la ted to the depos i t ion of Unit A. Up i n l e t from Section 13 Unit A i s wel l developed, while down i n l e t past Section 12 Unit A i s far less developed and may be at most a veneer on Units B, C or basement. From Section 12 to Section 18 at the Narrows and up Holberg In le t to near Section 17, the sea f l oor i s i r r e g u l a r and rather hummocky. This i s an area of p a r t i a l erosion of Unit B. The l o n g i t u d i n a l p r o f i l e for Holberg In le t not presented here beyond Section 17 grades u n i -formly headward s i m i l a r to the upper part of Rupert In le t p r i o r to mine a c t i v i t y . Lack of cover over the eroded surface of Unit B i n the deepest part of the Holberg-Rupert trough i s very s i g n i f i c a n t . The i n f i l l i n g east of Section 15 and the h i l l s west of Section 18 give Unit B a present s t r a t i g r a p h i c thickness of 170 feet . By p r o j e c t i o n , the o r i g i n a l thickness may have approached 200 feet . In the depression below the Narrows on the Rupert In le t s ide , about 100 feet of Unit B have been eroded. Unit A i s the term appl ied to a l l mater ia l o v e r - l y i n g the gray clays of Unit B. Where cored and sampled, i t i s c h a r a c t e r i s t i c a l l y o l ive -gray mud with a wide range of grain s ize and includes s h e l l fragments. However, the ent i re sect ion 97 i n areas of good development has not been cored. U n i t A i s up t o 75 f e e t t h i c k i n Rupert I n l e t (Figure 37, S e c t i o n 9) and more than 50 f e e t i n Holberg I n l e t (Figure 41, S e c t i o n 20). The e r o s i o n of U n i t B i n Rupert gap and the d e p o s i t i o n of U n i t A i n the upper reaches of Rupert I n l e t were contemporary events which s t a r t e d when the p r e s e n t oceanographic regime was e s t a b l i s h e d . When c l e a r i n g of i c e or rock b a r r i e r s took p l a c e t i d e s of Quatsino Sound f i n a l l y surmounted the s i l l i n Quatsino Narrows and e s t a b l i s h e d the p r e s e n t bottom c u r r e n t regime i n the i n l e t s . The presence of a t h i n mantle of U n i t A below the Narrows suggests t h a t the e r o s i o n of U n i t B, which must have been very r a p i d i n i t i a l l y , i s now almost stopped. D e p o s i t i o n of U n i t A appears c o n t r o l l e d by bottom c u r r e n t s which attempted to m a i n t a i n a passage along the base of the south w a l l of Rupert I n l e t . Very l i t t l e s edimentation of s o f t U n i t A has been allowed along the e n t i r e l e n g t h of the i n l e t . S e v e r a l of the t r a n s v e r s e s e c t i o n s (e.g. F i g u r e s 38 and 39, Sec-t i o n s 3,4,6,9., and 11) suggest t h a t the d e p o s i t i o n of the wedge of U n i t A has p e r s i s t e d s i n c e U n i t B time but t h a t on o c c a s i o n the toe edge of these beds was eroded by a long-term i n c r e a s e i n speed of the bottom c u r r e n t s . M o d i f i c a t i o n of bottom c u r r e n t s might be r e l a t e d to a long-term c l i m a t i c v a r i a t i o n , a change i n sea l e v e l r e l a t i v e t o the depth of the s i l l o r even an o f f s h o r e or outer s i l l change which allowed f r e e r access of o f f s h o r e up-w e l l i n g water to Quatsino Narrows. The t r u n c a t e d toe of U n i t A 98 has more recent ly been covered by subsequent beds, suggesting return to e q u i l i b r i u m . There i s no seismic evidence to ind icate whether the beds were constructed by down-slope migration of d e t r i t u s or up-slope currents . However, the even thickness of i n d i v i d u a l beds suggests depos i t ion was dominated h y d r a u l i c a l l y rather than by mantle creep. Construct ion of Unit A was l a r g e l y through ero-s ion and deposi t ion of Unit B; transport of mater ia l which had moved down the south f lank onto the north f lank; and the r e -tent ion of north flank down-slope m a t e r i a l . Slow growth of Unit A p r i o r to mine a c t i v i t y was caused by l o c a l l y o r i g i n a t i n g f l u -v i a l and marine d e t r i t u s . In Holberg I n l e t , bedded deposits (Figure 40B) with a seismic s igna l s i m i l a r to Unit A p e r s i s t from Section 17 up i n -l e t at l east to Norton Po int , but Unit B i s not observed from Section 17 westward. At m i d - i n l e t (Section 20) sedimentation appears uniform with the gentle concavity the probable r e s u l t of compaction of the th icker sect ion towards the ax i s . Section 19 shows uniform bedding with a d i s t i n c t but s l i g h t slope to -wards the south w a l l . This slope suggests gentle bottom currents , stronger along the south side of the bas in . Down i n l e t beyond Coal Harbour, the th ick Unit A sect ion noted on the l o n g i t u d i n a l p r o f i l e (Figure 40B, Section 17) i s seen not only to r i s e head-ward but also to have a s trongly wedge-shaped asymmetry, p i l i n g against the south bank (Figure 41, Section 17). The sect ion i s 99 reminiscent of those i n Rupert I n l e t (e.g. Figure 39, Se c t i o n 9) only reversed, w i t h p i l i n g a gainst the opposite w a l l . Both show greater current motion along the l e f t - h a n d w a l l l o o k i n g down i n l e t i n agreement w i t h C o r i o l i s e f f e c t . The i n l e t bottom at Section 16 i s dominated by i r r e g u l a r rock outcrops at the base of the north w a l l , which appears to be swept c l e a r of sediment (also F i g u r e 40A). At Se c t i o n 18, sediments of U n i t A r i s e a gainst the south w a l l unconformably o v e r l y i n g U n i t B s t r a t a and emphasizing the markedly deeper eros i o n of Un i t B on the south w a l l , d i r e c t l y below the narrows as compared wi t h the north w a l l . P r i o r to mine a c t i v i t y , the Holberg-Rupert trough was a U-shaped g l a c i a l l y scoured v a l l e y deepening from the head of Rupert I n l e t to Hanking P o i n t , then becoming p r o g r e s s i v e l y s h a l l -ower up Holberg I n l e t . Coarse g l a c i a l d e b r i s (Unit C) formed poorly bedded deposits p a r t i a l l y f i l l i n g l o c a l i r r e g u l a r i t i e s i n the trough. Fine g l a c i a l d e b r i s and rock f l o u r formed uniform s t r a t a d i p p i n g very g e n t l y westward (Unit B). I n i t i a t i o n of the present h y d r a u l i c regime caused e r o s i o n of Unit B below the Narrows, w i t h u p - i n l e t movement of eroded m a t e r i a l and redeposi-t i o n as Un i t A. Erosion of Un i t B had ceased and n e a r - e q u i l i -brium e x i s t e d p r i o r to mine a c t i v i t y . The s e t t i n g having been e s t a b l i s h e d , i t i s p o s s i b l e to i d e n t i f y and i n t e r p r e t the gross features r e s u l t i n g from mine a c t i v i t y . Two major sources of sediment o r i g i n a t i n g from the 100 mine p r o v i d e g r e a t amounts o f sediment i n a s m a l l a r e a about one m i l e i n l e n g t h a l o n g t h e c e n t r a l n o r t h shore o f Rupert I n l e t . The s o u r c e s a r e t h e t a i l i n g o u t f a l l o f f t h e m i l l s i t e and t h e waste r o c k dump o f f the mine s i t e ( F i g u r e 36). The t a i l i n g o u t f a l l i s a p i n p o i n t s o u r c e 148 f e e t below t h e s u r f a c e ; t h e waste r o c k dump i s a l s o a r e s t r i c t e d s o u r c e a r e a but a t t h e s u r f a c e . A t h i r d s o u r c e o f sediments c a r r i e d by r u n o f f from t h e denuded s l o p e s i s n o t c o n s i d e r e d i n t h i s d i s c u s s i o n b u t may be i m p o r t a n t t o l o c a l t u r b i d i t y o f t h e upper water column. W h i l e i t i s known (Chapter V, Sediments) t h a t t h e mine d e t r i t u s extends t h r o u g h o u t R u p e r t I n l e t and up the a x i a l a r e a o f H o l b e r g I n l e t t o N o r t o n P o i n t , i t i s o n l y where t h e s e sediments a r e d i s c o r d a n t w i t h t h e p r e c e d i n g sediments and have s u f f i c i e n t t h i c k n e s s t o p r e s e n t a d i s t i n c t i v e s i g n a l t h a t t h e y a r e v i s i b l e on s e i s m i c p r o f i l e s . I n many a r e a s where t a i l i n g d e p o s i t s a r e t h i n o r con f o r m a b l e w i t h e x i s t i n g s t r a t a , t h e y cannot be d i s -t i n g u i s h e d from t h e s t r a t a below. However, s e i s m i c d a t a i s p a r t i c u l a r l y h e l p f u l i n o b s e r v i n g and i n t e r p r e t i n g major changes r e s u l t i n g from mine a c t i v i t y and w i l l become an i n c r e a s i n g l y use-f u l t o o l i n t h e m o n i t o r i n g program as t h e amount o f mine d e b r i s i n c r e a s e s . Comparisons o f t h e e q u i v a l e n t t r a n s v e r s e s e c t i o n s be-tween F i g u r e s 37, 38 and 39 r e v e a l changes t h a t have o c c u r r e d as mine a c t i v i t y has proceeded. U n i t A, which i n 1971 ( F i g u r e 37) showed no s i g n o f r e c e n t d i s t u r b a n c e , a f t e r one y e a r o f produc-t i o n ( F i g u r e 38) showed l a r g e submarine slumps o r s l i d e s i n two 101 areas. These massive disruptions can be seen i n Section 8 off the t a i l i n g o u t f a l l and i n Section 5 o f f the waste rock dump. Unit A i n adjacent Sections 4, 6 and 9 shows no slumping despite i t s extremely close proximity to the disturbed sections. However, Sections 6, 9, 11, 13 and 12 a l l show modification i n the a x i a l area. The f l a t beds i n the trough of Section 6 are sediment ponded behind a "dam" created below the t a i l i n g o u t f a l l by the slumping and related fan development. Down**inlet from Section 8, the toe of the t a i l i n g slump or fan can be seen i n the axis of Section 9, while further down i n l e t the t a i l i n g modify Sections 12 and 13 but conform to the general configuration of the equiva-lent sections i n Figure 37. Sections 14, 15 and 16 (Figure 38) are not sub s t a n t i a l l y changed although t a i l i n g are evident i n bottom samples from th i s area. Here either the t a i l i n g are thin or the bottom current i s s u f f i c i e n t to maintain the bottom con-f i g u r a t i o n . Comparison on Figure 38 of Sections 5 and 8 i s of inte r e s t because i t i l l u s t r a t e s that the manner of f a i l u r e of Unit A varied under d i f f e r i n g types of load. The load at Section 5 was large l y heavy rock debris from b l a s t i n g , trucked to the edge of the dump and bulldozed into the i n l e t . The f a i l u r e of the soft s t rata was complete, with general displacement outwards to the centre of the i n l e t . Bedding was nearly t o t a l l y destroyed. A li n e a r depression p a r a l l e l to and against the seismic basement of the north flank was formed. Under normal sedimentation t h i s depression would be f i l l e d with soft sediment. This condition, 102 occurr ing n a t u r a l l y i n the past , i s suggested (Aydin, 1974) as the cause of the nearly transparent wedge-shaped zone often ob-served against the north f lank i n the o r i g i n a l survey (e.g. F i g -ure 37, Sections 4, 5, 6, 8 and 9) where e a r l i e r slumping occur-red and the depression l a t e r f i l l e d with soft sediment. Slumping due to loading by t a i l i n g .as seen i n Section 9 (Figure 38) appears to have caused only s l i g h t down-slope motion i n the upper slope but with a cumulative e f fec t of massive buck-l i n g and des truct ion of the bedding i n the lower s lope. The 1973 survey (Figure 39) shows further slumping. As the waste rock dump extended along the shore, the depression at Section 5 was p a r t i a l l y i n f i l l e d by new dumping but Unit A f a i l e d at Section 4 i n a manner s i m i l a r to that of Section 5. In the t a i l i n g o u t f a l l area , Unit A at Section 8 appears to have under-gone f a i l u r e but now mainly i n i t s upper s lope. T h e . i r r e g u l a r p r o f i l e of the lower slope i s mantled by t a i l i n g , and perhaps a lso through erosion by bottom currents as supported by the return of the onlap against the south wal l to a smooth arcuate shape. Ponding of sediments behind the t a i l i n g fan now extends up i n l e t past Section 5. The remainder of the transverse sect ion of 19 7 3 pre-serves the character developed i n 1972, with one notable excep-t i o n : Section 14 (Figure 39) shows deep i n f i l l of the trough by t a i l i n g which are f l a t - l y i n g . When viewed i n l o n g i t u d i n a l 103 section (Figure 4OB) the t a i l i n g can be seen to extend down i n -l e t from the t a i l i n g fan f i l l i n g the topographic i r r e g u l a r i t i e s and creating a uniform slope nearly to Section 15. Section 14 i n Rupert gap i s close to the positions of current meter Runs 9 and 10, where strong bottom currents sweep the bottom alternately down, then up i n l e t . Between Section 14 and 15, the t a i l i n g appear to have a maximum thickness of 45 feet, accomplished through i n f i l l i n g to achieve grade. Figure 40B affords further comparison between the waste rock s l i d e s and the t a i l i n g fan. The fan was b u i l t without major d i s l o c a t i o n of underlying Unit A and B strata i n the trough where-as the waste rock s l i d e s have dislocated and jumbled the section to basement. The ponding of mine-derived soft sediments behind the t a i l i n g fan i s well i l l u s t r a t e d . The fan i s now about 40 feet thick. Although by 19 73 t a i l i n g are known to extend beyond Section 15 well up Holberg Inlet, the o r i g i n a l i r r e g u l a r topo-graphy beneath the Narrows between Sections 15 and 17 p e r s i s t s with only minor i n f i l l i n g (Figure 40B). Whether t h i s topo-graphy has persisted due to lack of s u f f i c i e n t t a i l i n g reaching the area, or whether i t manages to p e r s i s t through cleansing by bottom currents, i s a matter of conjecture. If s i g n i f i c a n t bottom, currents did not e x i s t , t h i s area should have been i n -f i l l e d quite early by down-slope migration of sediment from s l i d e and slump a c t i v i t i e s . The longitudinal section, Figure 40B, gives evidence that currents move sediments up both Rupert 104 and Holberg i n l e t s away from the Narrows. The i n f l e c t i o n Point A (Figure 40B) i s the eastern termination of a thick section of Unit A type beds. After a rather abrupt convex r i s e , the slope maintains grade for many miles up Holberg Inlet. The i n f l e c t i o n point marks beds prograding slowly eastward, not by down-inlet movement but rather by up-inlet currents carrying material away from the Narrows. A similar i n f l e c t i o n point exists at Point B (Figure 40B) near Section 15, which marks the present toe of the major t a i l i n g body i n Rupert Inlet. At present Point B appears protected by topography. The fact that Point A i s at the base of a far greater r i s e than Point B does not necessarily mean that B w i l l develop or even p e r s i s t , since i t may be overwhelmed by the t a i l i n g supply. The two i n f l e c t i o n points do support the inference that currents clear sediments from below the Narrows. Observations of currents (Chapter III) indicate that bottom currents regularly occur and are convergent beneath the Narrows. This would suggest that while fine material might be l i f t e d from the bottom and swept up i n l e t i n upper currents, the winnowed coarser material would tend to p i l e up or at least be swept about the bottom below the Narrows. Perhaps t h i s p i l i n g w i l l ensue when enough of the coarser f r a c t i o n of the t a i l i n g has accumulated. However, Section 18 shows Unit B erosion (Figure 39, Section 18) greater below the Narrows than below Hankin Point. The seismic data i l l u s t r a t e rather conclusively that, 105 over a period of time, the dominant bottom currents i n terms of erosion and transport of sediment were from the Narrows moving headward up both i n l e t s . This i s i n d i r e c t support for the hypothesis of dominance of the sporadic maximum density current . 106 CHAPTER V SEDIMENTS Sediments a r e a r e c o r d o f t h e p a s t d e p o s i t i o n a l regime, r e f l e c t i n g i n t h e s t r a t i g r a p h i c sequence p a s t changes i n t h e regime. The uppermost sediments s h o u l d t h e r e f o r e be t h e b e s t e v i d e n c e o f p r e s e n t d e p o s i t i o n . The sediments i n t h e H o l b e r g -Rupert system, p a r t i c u l a r l y t h e upper few c e n t i m e t r e s , a r e ex-amined f o r c o r r o b o r a t i o n and r e f i n e m e n t o f i d e a s c o n c e r n i n g de-p o s i t i o n a l r e a d y f o r m u l a t e d from s t u d y o f c u r r e n t d a t a and s e i s -mic p r o f i l e s . I n Chapter I I I i t was shown t h a t t i d a l bottom c u r r e n t s o f s u f f i c i e n t magnitude t o faffffierc't s e d i m e n t a t i o n do e x i s t a t l e a s t s p o r a d i c a l l y a t t h e sediment-water i n t e r f a c e . The s e i s -mic s t u d i e s o f Chapter IV suggest t h e s e c u r r e n t s have eroded a n e a r l y f l a t - l y i n g f o r m a t i o n , U n i t B, i n t h e a r e a beneath and near t h e o u t f a l l o f Q u a t s i n o Narrows, and have e i t h e r s i m u l t a n -e o u s l y o r s u b s e q u e n t l y c o n t r o l l e d d e p o s i t i o n o f t h e o v e r l y i n g sediment, U n i t A, p r e d o m i n a n t l y headward i n b o t h Rupert and H o l b e r g i n l e t s . The p r e s e n t c h a p t e r examines t h e n a t u r e and d i s -t r i b u t i o n o f U n i t B and U n i t A, and t h e t a i l i n g d e p o s i t s from t h e f i r s t two y e a r s o f mine p r o d u c t i o n f o r i n d i c a t i o n s of t h e f i n a l d i s t r i b u t i o n upon c o m p l e t i o n o f m i n i n g . The, e f f e c t o f d e n s i t y c u r r e n t s r e s u l t i n g from i n f l o w o f t a i l i n g upon t h e s e d i m e n t a t i o n p a t t e r n i s c o n s i d e r e d . Three well-known diagrams a r e i n t r o d u c e d as i l l u s t r a -107 <_> o UJ > 100.0 10.0 c o o S o 0 6 0 S £ ^ P Q O O O P O P P P - CVJ u» o GRAIN SIZE (millimeters) o p o 9 U J > Figure 43. V e l o c i t y and Grain Size Relat ionship to Eros ion , Transportat ion and Depo-s i t i o n . Hjulstrom's (1955) diagram, af ter B l a t t , Middleton and Murray (1972) with addit ions from Garrels and MacKenzie (1971). t i ve of sedimentation p r i n c i p l e s c e n t r a l to the ensuing d i scus -s ion . Figure 43 i s a modi f icat ion of Hjulstrom's (1955) diagram r e l a t i n g eros ion , transportat ion and depos i t ion af ter B l a t t , Middleton and Murray (1972) but with further modi f icat ion as presented by Garrels and MacKenzie (1971). The e f fec t of current on s e t t l i n g rate i s presented i n Figure 44, from Garrels and MacKenzie (1971). This diagram, while mainly subjec t ive , indicates the dramatic pro trac t ion of s e t t l i n g time of f ine mater ia l effected by even a s l i g h t current . Figure 45, from Schubel (1971), although based on measurements i n a shallow estu-ary i l l u s t r a t e s the e f fect on sediment suspension of t i d a l cur -rents , and i s s i m i l a r to diagrams of Potsma (1967). Such mech-1 0 8 Distance (km) Time (hr) 1 0 0 0 10.000 100.000 ri ,• A A (22 years) F i g u r e 4 4 . S e t t l i n g Time i n 1 0 cm/sec C u r r e n t . F r o i t i-Garrel.fi and M a c k e n z i e , 1 9 7 1 ( a f t e r Amer . G e o l , I n s t . , , 1 9 6 7 ) 280 260 5 m above Bottom (-8m) \ f-05m above Bottom (-9m) F i g u r e 4 5 . R e l a t i o n s h i p o f T i d a l C u r r e n t V e l o c i t y t o Suspended Sediment C o n c e n t r a t i o n . ( A f t e r S c h u b e l , 1 9 7 1 ) 109 anisms must be at l east sporad ica l ly operative i n parts of the Holberg-Rupert basin at water depths of 500 feet . E s s e n t i a l l y , Figure 45 shows two f a c t o r s , a long-term background l e v e l of t u r -b i d i t y and a short-term load. The p o t e n t i a l for a background l e v e l of t u r b i d i t y i s a key point portrayed by Figure 44 for the slow s e t t l i n g of f ine-gra ined m a t e r i a l . Above t h i s background l e v e l the concentration of suspended so l ids i s increased i n phase with current v e l o c i t y . In Figure 45, while the amount of mater-i a l i n suspension has increased with v e l o c i t y four times at 1.5 metres'' o f f bottom, i t has been increased ten times at 0.5 metres o f f bottom. E s s e n t i a l l y the ent ire load above background l e v e l i s dropped at each s lack t i d e . S i m i l a r l y , a corresponding i n -crease i n gra in s ize occurs towards the base of the suspended load as i t merges with the sediment load i n motion by s a l t a t i o n and t r a c t i o n (Potsma, 1967). As a sediment catchment, the Holberg-Rupert basin i s very e f f e c t i v e . Only sediment f ine enough to be i n suspension i n the upper part of the water column can become entrained i n the ebb flow through Quatsino Narrows and escape. Sources of s e d i -ment within the basin are very l i m i t e d . I n i t i a l washing of the surrounding slopes fol lowing g l a c i a t i o n must have provided much of the sediment now present i n the scoured trough. Continued erosion of the g l a c i a l t i l l s on surrounding h i l l s and erosion of bed rock by t i d a l scour plus pe lagic and hemipelagic mater ia l have contr ibuted . The major flow of water into the bas in i s not from r i v e r s but through Quatsino Narrows, however since ebb 110 v e l o c i t i e s are greater than f lood v e l o c i t i e s , bottom sediment mater ia l from Quatsino Sound i s prevented from entering the bas in . Only very f ine d e t r i t u s , mainly pe lagic and hemipelagic m a t e r i a l , can enter from th i s source. While numerous minor streams rim the bas in , t h e i r e f fect i s very l o c a l . Only the Marble River whose flow i s only about 5% of Quatsino Narrows i s large enough to be a s i g n i f i c a n t sediment contr ibutor . The Marble 6 3 River has an average flow of 2,235 cu f t / s e c (5.5 x 10 m /day) as compared with the next larges t t r i b u t a r y Wawkwaas Creek, at the head of Rupert I n l e t , with an average flow (Drake, 1973) of 457 cu f t / s ec (1.1 x 10 m / d a y ) . As a sediment contr ibutor , the Marble River i s even less s i g n i f i c a n t than i t s volume would sug-gest, s ince i t i s a short r i v e r dra in ing a ser ies of large lakes which must already have captured much of the sediment load . Well sorted, medium-grained sand from the Marble River estuary i n Varney Bay suffers gradual a t t r i t i o n and enters the bottom regime of the bas in . Very f i n e l y suspended m a t e r i a l , which w i l l be f l o c c u l a t e d , enters the basin so close to the Narrows that i t i s l i k e l y to be swept u p - i n l e t when introduced during f lood t ide o r , conversely , drawn out through the Narrows when introduced on the ebb t i d e . Cores and Samples This study u t i l i z e s cores and grab samples obtained during the Univers i ty of B r i t i s h Columbia survey conducted before t a i l i n g were introduced, as wel l as mater ia l c o l l e c t e d subsequent-ly by the wr i ter and samples obtained quarter ly by personnel of I l l Island Copper. A l l sample s i t e s are indicated on Figure 46; only pert inent s i t e s are shown on subsequent maps. The geo log i -c a l survey by the Univers i ty of B r i t i s h Columbia i n March 1971 preceding in troduct ion of t a i l i n g resul ted i n 13 cores and 29 grab samples annotated as the "U" s e r i e s , UC (cores) and UG (samples). A further 13 cores and 8 samples were c o l l e c t e d by the wr i ter i n A p r i l 1973 at locat ions annotated as the " J " ser i e s . The quarter ly survey by Island Copper includes c o l l e c t i o n of cores at 21 s tat ions i n the bas in; t h i s mater ia l i s i d e n t i f i e d by s ta t ion number followed by a l e t t e r designating the s er i e s : "L" s e r i e s , June 1971; "M" s e r i e s , September 1971; "N" s e r i e s , December 1972; "F" s e r i e s , March 1973; "P" s e r i e s , June 1973; "Q" s e r i e s , September 1973. Cores and samples include t a i l i n g from the f i r s t two years of product ion, October 1971 to September 1973. The U ser ies and J ser ies s tat ions were located by sex-tant t r i a n g u l a t i o n to shore features . The r e p e t i t i v e Mine ser ies were c o l l e c t e d by Mine personnel systemat ica l ly reoccupying s tat ions based on shore and depth i d e n t i f i c a t i o n . The wr i ter frequently accompanied these mine surveys and during the Septem-ber 1973 "Q" cruise used the Ponar grab sampler to c o l l e c t s u f f i c i e n t mater ia l for t a i l i n g studies from areas of t h i n deposi -t i o n , p a r t i c u l a r l y i n Holberg I n l e t . The U ser ies and J ser ies used a 2.5 inch Phleger core with 50 to 150 l b s . while the Mine ser ies used a small 1.25 inch 112 + I A + -B + -C + -D F + 6 +• -H + -I + -+ -K + -. L + -M + -+ i + i + i + i 2 + 3 + 4 + 5 • i - + - + -+ 7 + 8 + 9 + 10 + II + 12 + 13 + 14 +15 + 16 + 17 + 18 +- 19 + 20+ 21 + 22 + 23+ 24+ 25+ 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33+ 34+ 35 + 36 + 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48+ 49 + 50 + + - + -E • + - + i +• 4-+ + A + B 4 c + D + E + F + G + H + I + J + K +_ L -t M + Figure 46, 113 Phleger core with less weight. The U ser ies used a Petersen grab sampler, the J ser ies used a Shipek sampler while the Mine used a Ponar sampler. The Shipek sampler has the advantage that i t brings the sediment in ter face on deck often undisturbed where i t can be examined, scrap®dd or "cored" for comparative study. Laboratory The samples and cores were co l l ec t ed p r i m a r i l y for evaluat ion of s t ruc ture , texture and g r a i n - s i z e . The soft uncon-so l idated t a i l i n g were p a r t i c u l a r l y d i f f i c u l t to handle. The best method found i s to dra in each core , al lowing i t to set by s l i g h t l y d r y i n g , then extrude i t onto a bed of absorbent towel-l i n g , smoothly withdrawing the p l a s t i c l i n e r down the core while holding the core s tat ionary with a wooden p i s t o n . The core i s allowed to dry s l i g h t l y longer on the bench and can then be cut v e r t i c a l l y with a long s c a l p e l . Measurement can be made and both the core and underlying paper marked against shrinkage by dry ing . When d r i e d , the s p l i t surface can be shaved to reveal s t ruc ture . Cores were examined both wet and dry , described as to s tructure and colour (Geol. Soc. Am., 1963) then d iv ided into 10cm i n t e r v a l s , each i n t e r v a l becoming a separate sample for gra in s ize a n a l y s i s . A l l samples, both core and grab, were gently r o l l - c r u s h e d and, where necessary, d i s in tegrated by soak-ing , then dry sieved through 2mm (-1(J>) . The U and J ser ies cores are s u f f i c i e n t l y large to allow preservat ion of one-half for reference. 114 The less than 2mm f r a c t i o n was progress ive ly s p l i t to a repre-sentat ive 80 gram sample. The mater ia l was then handled i n accordance with the "Part i c l e Size Analys i s Hydrometry Method Using Computer Program" of Harr i s and Lavkul ich (1972). Folk (1968) and Royse (1970) were used as laboratory guides. Essen-t i a l l y , the method employs a standard hydrometry program i n which the sample was s p l i t into two 40 gram p a r t s . Each cut was washed i n deionized water and centri fuged twice to remove s a l t s , then treated with 30% and gentle heat to remove organic matter. One cut was oven-dried to obtain a dry weight. The second cut was dispersed with 10% sodium hexametaphosphate (Calgon), mixed, transferred to a o n e - l i t r e c y l i n d e r , and made up to one l i t r e with deionized water. Hydrometry readings were taken at 1/3, 1, 2, 4, 8, 15, 30 minutes and 1, 2, 3, 6 and 24 hours. Temperature c o n t r o l and c a l i b r a t i o n were maintained. The data were then com-puterized i n the re la ted Univers i ty of B r i t i s h Columbia So i l s Department program. The computer output tabulated the re la ted time against per cent so l ids remaining i n suspension, p a r t i c l e diameter i n mm., the logarithm of the p a r t i c l e diameter and the percentages of sand, s i l t and c lay i n the sample. A graphic computer p lo t of the data was produced on f i v e - c y c l e semi-loga-r i thmic base with the log of the diameter along the abscissa against cumulative percentage on the ordinate . Selected mater ia l underwent further s i z i n g . The greater than 2mm (-lcj)) f r a c t i o n was wet-screened into ten f r a c t i o n s . Mat-e r i a l from hydrometry was allowed to s e t t l e then decanted and wet-115 screened through #230 mesh (U.S. Std.) or 4cJ>. (62.5y) . The larger than 4tJ> mater ia l was then dry-screened through 1/2 (j) i n t e r v a l s from -0.5 to 4tj). The smaller than 4cJ) f r a c t i o n was again decanted and, using a Warman C y c l o s i z e r , separated into f ive f rac t ions down to approximately 6.5<J>. M a t e r i a l smaller than 6.5<j) (15.6y) was l o s t . A l l remaining m a t e r i a l , inc lud ing core s p l i t s and s ized f rac t ions was l a b e l l e d and stored. I t should be noted that i n th i s study, which i s con-cerned i n part with t a i l i n g sedimentation, the s a n d - s i l t boundary i s taken as 50y (4.25<j>) and the s i l t - c l a y boundary as 2y (9cJ)) . While sedimentologists general ly use the Wentworth c l a s s i f i c a t i o n of 62.5y (4<j)) as the s a n d - s i l t d i v i s i o n , mineral engineers and an increas ing number of s u r f i c i a l and engineering geo log ica l workers now use the a l ternate c l a s s i f i c a t i o n . P r a c t i c a l l y , while the smaller value (50y) does not s er ious ly af fect the geo log ica l evaluat ion i t proves more appropriate for mapping the very f i n e -grained materials which dominate the study. Potsma (1967) study-ing sediment movement i n shallow t i d a l waters found 50y to be the convenient boundary between sand and s i l t . In th i s study gra in s izes are given as the hydraul ic equivalent i n a s e t t l i n g tube as compared with the true s i z e . M a t e r i a l was c o l l e c t e d from 92 locat ions from which 260 samples underwent hydrometry a n a l y s i s . The resu l t s are presented i n Tables II to V , i n part summarized as out l ined i n subsequent d i scuss ion . 116 Interpretat ion The cumulative percentage curve r e s u l t i n g from the Harr i s and Lavkul ich (19 72) program i s very d i s c r i m i n a t i n g i n the 3.5<J> (88u) to 9.5<j> (1.99u) range. For f iner m a t e r i a l , the convention of Folk and Ward (1957) of a s t ra ight l i n e pro jec t ion to 14(f) (0.06u) at 0% i s used. Unless other data were a v a i l a b l e , a s i m i l a r s t r a i g h t l i n e method was used to complete the curve to 100% since the maximum s ize of the m i l l t a i l i n g (2(f>) and the natura l sediments (-l(f>) i s known. Both procedures tend to m i n i -mize the degree of s o r t i n g . For the very f ine sand-to-c lay s ize mater ia l which i s the nature of the t a i l i n g and main s ize range i n t e r e s t to th i s study, the contro l i s exce l l en t . Since the lack of contro l i s l arge ly i n the " ta i l s" of the cumulative curve, Graphic Standard Deviat ion (^Q) of Inman (19 52) i s p lo t t ed on maps with the more comprehensive Inclus ive Graphic Standard Deviat ion (ox) (Folk and Ward, 1957) given i n table form(Tables II to V ) . In i n t e r p r e t i n g the computer-prepared cumulative curve, an overlay of o) values was appl ied to the abscissa p lo t ted to l o g j Q & s c a l e . Phi values were then read from the curve for com-putat ion of the des ired graphic s t a t i s t i c a l parameters: median, mean and standard dev ia t ion . The mean determined.; was the Graphic Mean (M ) (Folk and Ward, 1957) $16 + cj)50 + C)J84. Dispers ion or Z 3 sor t ing i s ca lcu la ted by the Graphic Standard Deviat ion (a_) (In-' G man, 1952) as (j)84 - (ft 16 with the Inclus ive Graphic Standard Devia-2 t i on (a ) (Folk and Ward, 19 57) as (cj)84 - <j)16) + cf>95 - j>16 and 4 6.6 l i s t e d i n Tables I I , III and IV. Data presented i n the tables 117 form the basis for d iscuss ion of three s t r a t i g r a p h i c u n i t s : Unit B (the lowermost penetrated natura l sediments), Unit A (the most recent natura l sediments) and mine t a i l i n g . Unit B Unit B i s a gray p l a s t i c clayey s i l t which has been sampled at e ight locat ions along the deep a x i a l part of the H o l -berg-Rupert trough (Figure 47). The un i t i s r e a d i l y d i s t i n g u i s h -able from the over ly ing Unit A which i s dark o l i v e - g r a y i n co lour , less p l a s t i c and more var iab le i n texture . Comparative data for Unit B samples are presented i n Table I I . The maximum thickness cored i s about 60 cm at UC 17 and UC 20 i n mid-Rupert I n l e t . The average median and mean gra in s ize i s 3]i (8.4$), very near the c l a y - s i l t boundary. Sort ing i s very poor (Std. Dev. 3.4(f)) with approximately 10% sand present i n nearly equal parts of s i l t and c l a y . The un i t i s u n s t r a t i -f i e d and uniform, with only the occas ional large clam s h e l l and pebble i n c l u s i o n and i s thought to cons i s t of g l a c i a l rock f l our deposited i n the present basin p r i o r to revegetation of the adja-cent s lope, before the opening of Quatsino Narrows, which was e i ther not then formed or blocked by i c e . The very f ine -gra ined , homogeneous, p l a s t i c nature of Unit B suggests that current v e l o c i t i e s i n excess of 50 cm/sec and more probably 100 cm/sec were required to so deeply erode th i s un i t (Figure 43). Such v e l o c i t i e s are i n keeping with 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33+ 34+ 35+ 36+ 37 + 38+ 39+ 40+ 41 + 42+ 43 + 44 HOLBERG RU P E RT BASIN • • ' I I I i i i I I I i i i i i , SPECIMEN • NUMBER LOCATION WATER DEPTH % WT. OP » WT. OP -2MM FRACTION MEDIAN M2 ai TEXTURE• +2M.M 4SAND »SILT SCLAV * $ 9.2 $ JC3Z 30/H 591 0.0 6.4 49.6 44.0 8.4 2.6 V 2.8 clayey s i l t JG8Y 32/J 462 0.7 10.9 46.2 42.9 8.5 8.5 3.4 3.4 clayey s i l t JC8Z 0.0 5.1 49.8 45.1 8.6 9.0 2.9 2.8 clayey s i l t JB9/24-36 34/J 496 0.0 9.1 24.9 66.0 10.3 9.8 3.2 3.4 s i l t y clay JB9/36-46 15.4 24.0 23.8 52.2 9.2 7.9 5.2 4.6 sa n d - s i l t - c l a y JB9/46-58 0.8 0.2 30.3 69.5 10.4 10.5 2.3 2.3 s i l t y clay JB 13Z 36/1 450 15.7 16.8 31.2 53.0 9.2 8.4 4.4 4.2 s i l t y clay J4Z 38/H 384 13.0 18.1 47.75 34.2 7.3 7.7 3.8 3.7 clayey s i l t J6Z 37/G 414 5.0 24.5 32.8 42.6 8.4 7.6 4.8 4.4 sa n d - s i l t - c l a y UC17/35-45 39/G 402 0.4 8.7 55.1 36.2 7.6 8.1 3.4 3.1 s i l t y clay /45-5S 0.1 9.0 53.3 37.6 7.8 8.2 3.4 3.1 s i l t y clay /S5-65 0.0 5.7 55.6 38.7 8.0 8.4 3.2 3.0 clayey s i l t /6S-75 0.0 8.6 51.6 39.8 8.1 8.5 3.3 3.2 clayey s i l t /7S-82 .Rase 'Core 0.0 11.3 50.8 37.9 7.6 8.3 3.5 3.4 slayey s i l t 0.2 7.1 55.3 37.6 8.2 8.5 3.1 3.1 clayey s i l t OC20/32-42 40/G 384 0.5 9.7 72.8 17.5 8.2 7.5 1.9 2.2 clayey s i l t /42-S2 0.1 10.9 53.2 35.9 7.8 8.0 3.2 3.1 clayey s i l t /S2-62 0.0 10.9 56.0 33.1 7.3 8.0 3.5 3.3 clayey s i l t /62-72 0.4 14.6 52.9 32.5 7.4 7.8 3.5 3.2 clayey s i l t /72-86 .Base 'Core 0.3 9.6 54.4 36.0 7.7 8.1 3.5 3.2 clayey s i l t 2.1 4.5 54.5 40.9 8.0 8.6 3.3 3.0 clayey s i l t Average 439 2.6 10. 47. 43. 8.3 8.4 3.4 3.3 clayey s i l t TABLE I I : GRAIN SIZE DATA FOR UNIT B. I« z (Mean) and Oj (Inclusive Graphic Std. Dev.) follow Folic and Ward (1957), while o„ G (Graphic Std. Dev.) follows Inman (1952)J 120 observations of bottom currents reported i n Chapter I I I . The end of Unit B and the commencement of Unit A sedimentation appear?' coincident with the e f f ec t ive opening of Quatsino Narrows as a t i d a l channel capable of exchanging ma-jor volumes of water with Quatsino Sound. This event changed the sedimentation regime i n the Holberg-Rupert basin to essen-t i a l l y the one which now p r e v a i l s . Unit A Unit A i s a dark o l i ve -gray to o l i v e - b l a c k sediment which formed the sedimentary cover throughout the Holberg-Rupert basin immediately p r i o r to mine a c t i v i t y . In th i s study emphasis i s placed on the character of the upper few centimetres of Unit A because t h i s i s the surface on which the t a i l i n g are deposited and as such, i s the best ind ica tor of the sedimentation regime before input of t a i l i n g . Grain s ize data for the upper 10 cm of Unit A are presented i n Tables III and IV. Some knowledge of the v e r t i c a l development of Unit A i s ava i lab le from the o r i g i n a l th i r t een U ser ies cores and from four a d d i t i o n a l J ser ies cores . These cores were analyzed i n 10 cm i n t e r v a l s and the data averaged i n Table I I I . The nature of the upper 10 cm of the core can be compared with the average character of Unit A penetrated at each core l o c a t i o n . The base of Unit A i s often dominated by a zone containing abundant, often unbroken clam s h e l l s . This zone i s best developed i n Rupert 121 SPECIMEN NUHBER LOCATION WATER DEPTH % NT. OP +2MM 1 WT. OP -2HM ISILT PRACTION tCLAV MEDIAN A • 0 G A °I ' TEXTURE SHEPARD (1954) ' ^ • UC3/0-10 30/H 540 0.1 18.5 44.8 36.7 7.6 7.7 4 .1 4.0 C l a y e y s i l t UC3/0-35 0.4 25.0 35.8 39.2 7.8 7.5 .5 4.2 s a n d - s i l t - c l a y UC6/0-10 16/B 320 2.9 16.3 41.3 42.4 8.2 8.3 .8 3.8 • l l t y c l a y UC6/0-47 10.0 37.1 34.0 28.9 6.0 6.3 .6 4.3 s a n d - s i l t - c l a y UC15/0-10 36/H 366 9.3 76.3 13.8 9.9 2.1 2.8 .1 3.4 aand OC15/0-50 14.1 84.2 10.3 5.5 1.8 2.0 .3 2.7 sand DC16/0-10 36/H 486 5.1 87.6 9.9 2.5 1.7 1.7 .8 2.1 sand OC16/0-30 4.1 88.6 8.0 3.4 1.6 1.6 8 2.2 • and UC17/0-10 39/0 402 0.6 57.8 27.3 14.9 3.6 4.3 4 3 4.0 a i l t y aand UC17/0-35 2.1 56.0 25.9 18.1 3.7 4.6 4 6 4.3 a l l t y sand UC19/0-10 40/E 243 0.1 39.5 34.2 26.3 5.4 5.6 5 7 4.7 a a n d - s l l t - c l a y UC19/0-73 4.0 43.6 36.1 20.3 5.1 5.2 4 8 4.3 a a n d - s l l t - c l a y UC20/0-U 40/Q 384 2.4 52.7 32.0 15.3 6.7 7.3 3 5 3.5 s i l t y sand UC20/0-32 10.1 51.5 30.9 17.5 6.7 7.3 3 5 3.5 s i l t y sand UC23/0-10 44/P 309 0.2 34.3 41.9 23.6 5.5 6.1 4 1 4.0 s a n d - s i l t - c l a y UC23/0-50, 0.4 26.6 45.3 28.1 6.1 7.0 3 8 3.7 s a n d - s i l t - c l a y UC24/0-10 43/E 234 0.1 18.1 52.5 29.4 6.7 7.4 3 6 3.5 c l a y e y s i l t UC24/0-73 .0.1 15.0 51.8 33.2 6.8 7.6 3. 3.4 c l a y e y s i l t UC27/0-10 46/P 210 0.8 64.2 24.2 11.6 3.8 4.0 3. 3.5 s i l t y aand UC27/0-42 9.6 63.9 25.9 10.2 3.7 3.8 3. 3.4 s i l t y sand UC28/0-10 46/K 174 0.1 31.3 47.9 20.8 5.2 6.4 3. 3.5 s a n d - s i l t - c l a y UC28/0-60 0.3 28.2 49.1 22.7 5.4 6.6 3. 3.4 s a n d - s i l t UC29/0-10 48/E 66 0.8 55.6 40.6 3.8 4.2 3.7 2. 2.5 s i l t y sand OC29/0-43 1.1 64.8 31.8 3.4 4.0 3.4 2. 2.3 s i l t y aand UC30/0-10 l i / T 0.0 2.1 48.0 49.9 9.1 9.2 3.' 2.9 c l a y e y s i l t UC30/0-46 0.0 6.9 53.2 39.9 8.7 8.6 2. 2.4 c l a y e y s i l t JS /0-10 37/J 240 24.3 76.8 14.7 8.5 2.1 2.9 3. 3.4 aand J5 /0-23 28.8 77.1 13.6 9.3 2.1 3.0 3. 3.5 sand JB9/1-16 34/J 496 23.2 68.5 20.0 11.5 2.4 3.4 3. 3.8 s i l t y sand JB9/1-24 25.6 49.2 28.8 22.0 4.7 5.0 4. 4.3 s a n d - s i l t - c l a y JC27/0-18 46// 222 19.6 56.3 28.7 15.0 4.1 4.5 3. 3.8 a i l t y sand JC27/0-27 11.8 45.2 38.4 16.4 4.9 5.2 3. 3.7 s i l t y sand JC8/0-10 32/J 4(2 8.3 58.9 21.1 20.0 3.0 4.5 4. 4.5 s a n d - s i l t - c l a y JC8/0-24 7.1 63.8 18.2 18.0 2.6 4.2 4. 4.4 s i l t y sand T A B L E m i GRAIN SIZE DATA POR SELECTED UNIT A CORES POR COMPARISON WITH TOP OP UNIT A . [ H ( (Mean) and °I ( I n d u s f o l l o w Polk and Ward (19 ve G r a p h i c S t d . Dev.) 7 ) , w h i l e °G (Graphic S t d . Dev.) f o l l o w s Inman (1952)) 1 2 2 SPECIMEN NUMBER LOCATION WATER DEPTH % WT. OP +2HM »WT. OF -2MM 5—xs ra FRACTION F tCLAY MEDIAN • " a 4 * °I 4. TEXTURE SHEPARD (19541 UG) 29/H 540 0. 20.0 41.7 38.3 8.1 7.9 4.1 4.0 c l a y e y ( l i t UG4 9/D 126 2.9 81.7 12.9 5.4 2.1 2.3 2.4 2.7 aand UG6 14/D 306 0. 1.8 47.2 51.0 9.2 9.4 1.3 2.9 • l l t y c l a y UGC 16/1 320 0. 16.5 4 4 . 1 39.2 7 . 8 8.0 1 . 8 1 . 8 c l a y e y a i l t UG7 32/J 480 5 2 . 8 76.2 12.7 11.1 2.1 3.1 3.6 1.7 • and UG8 32/J 540 8.7 71.1 17.9 11.0 2.2 3.2 1.7 1.7 • i l t y (and UG9 32/J 330 51.2 67.1 19.1 13.2 2.6 1.4 1.9 1.9 • i l t y aand _ UG10 •33/K 150 100 g r a v e l UG11 33/1 222 100 g r a v e l UG12 34/J 552 100 g r a v a l UG13 34/K 91 100 g r a v a l UG14 34/J 510 45.1 83.0 11.4 5.6 1 . 8 2.2 2.5 2 . 8 aand UG15 36/H 378 6.5 77.0 14.6 8.4 2.0 2.7 3.1 1.8 aand UG16 37/H 492 4.7 85.8 7.5 6.6 1.2 1.5 1.8 1.0 aand UG17 39/G 420 3.0 61.5 24.0 14.5 2.9 3.8 4.1 4.0 • l l t y aand UG18 40/E 175 16.9 71.7 19.3 9.0 2.3 3.1 3.5 1.5 a l l t y aand UG19 40/r 256 0.1 9.8 54.2 36.0 6.8 7.1 2.5 3.0 c l a y e y a l l t UG20 40/G 370 0.2 28.3 43.8 27.9 6.1 7.0 3.8 3.8 e a n d - a i l t - c l a y UG21 41/G 258 45.6 . 86.6 8.5 4.9 1 . 8 1.8 2.0 2.3 aand UG22 43/G 292 1.8 72.1 16.6 11.3 2.5 3.1 3.3 3.6 a i l t y aand UG23 43/P 324 0.8 39.4 31.8 28.8 5.2 6.1 4.7 4.3 s a n d - e l l t - c l a y UG24 4 3/E 240 0.1 9.9 60.3 29.8 6.6 7.5 3.3 3.0 c l a y e y a l l t UG2S 43/E 90 24.1 76.1 19.3 4.6 2.4 2.5 2.5 2.6 aand UG26 ' 46/F 162 4.6 68.8 19.2 12.0 3.5 3.5 3.2 3.5 a l l t y aand UG27 46/E 210 12.7 70.0 18.7 11.3 2.9 3.3 3.3 3.6 a i l t y aand UG2B 46/E 182 0.5 23.3 49.4 27.3 5.6 7.0 3.6 3.4 a a n d - e i l t - c l a y UG29 47/E 66 0.6 59.8 33.6 6.6 4.2 4.2 1.8 2.4 a i l t y aand J2SX 47/F 66 0.8 64.6 28.1 7.3 3.7 3.5 2.7 3.0 • i l t y sand J3SK 43/G 175 14.7 81.2 10.1 8.7 2.0 2.4 2.6. 3.1 aand J6X 37/G 414 1.7 70.6 18.1 11.3 2.4 1 . 3 3.6 3.7 • l l t y aand JA1 21/E 357 0.0 6.1 41. 52.9 9.4 JG3B 29/G 447 1.4 8.6 40.2 51.2 9.2 JG4SK 9/D 222 5.3 69.7 20.3 10.0 2.8 JG26 46/G 144 28.3 81.1 12.6 6.1 1.8 JC3/0-14 30/H 591 16.7 50.7 27.6 21.7 4.3 5L 0-10 2 6/H 417 0.0 16.7 40.8 42.5 8.3 6L 0-10 28/G 434 0.0 22.9 38.5 28.6 7.8 7L 0-10 29/F 93 22.7 71.2 17.6 11.2 2.7 8L 0-10 30/D 76 1.1 49.9 44.4 5.7 4.S 10L0-10 35/L 81 0.4 76.0 17.4 6.6 3.7 11L0-10 36/L 52 1.1 60.5 26.5 13.0 3.6 12L0-10 35/G 95 11.8 83.8 11.7 4.5 1.8 13L0-10 36/H SIS 16.2 88.1 7.1 4.8 1.4 14L0-10 36/1 258 25.9 72.9 16.8 10.3 2.8 18L0-10 46/D 80 22.6 83.0 15.5 1.5 2.4 19L0-10 45/F 252 0.9 35.0 45.3 19.7 5.1 20LO-10 45/G 139 4.3 76.0 2 0 . 2 3.8 2.6 21L0-10 49/F 48 0.8 59.0 13.0 6.0 4.1 250 10/D 265 2.0 37.1 17.3 25.2 5.6 26Q 4/C 242 2 2 . 1 6 7 .S 21.1 1 1 . 4 2 . 6 9.4 8.9 3.5 2.3 5.1 8.3 7.8 3.5 4.2 3.9 4.4 2.0 . !•< 3.7 2.4 6.2 2.7 3.7 6.0 1.2 3.2 3.6 3.6 2.7 4.6 4-0 4.2 3.4 1.3 0.9 2.4 2.3 1.5 3.1 2.1 3.0 2.5 2.2 4.7 GRAIN SIZE DATA FOR TOP OF UNIT A FROM ADDITIONAL CORES AND SAMPLES. and (Mean) and °I ( I n c l u a i v e G r a p h i c Std. Hard (1957), w h i l e °G (Graphic S t d . 3.0 a i l t y c l a y 3.3 a l l t y c l a y 2.0 a i l t y aand 2.9 Band 4.4 B a n d - a i l t - c l a y 3.7 a i l t y c l a y 4.0 a a n d - a l l t - c l a y 3.5 a i l t y aand 2.0 B i l t y Band 1.6 sand 2.9 s i l t y Band 2.4 Band 2.1 Band 1 . 3 B i l t y aand 2.1 Band 3.0 aandy a l l t 2.6 aand 2.6 a i l t y aand 4 . 3 a a n d - a l l t - c l a y 3.6 a l l t y c l a y Dev.) f o l l o w F o l k Dev.) f o l l o w s Inman ( 1 9 5 2 ) ) 123 trough o p p o s i t e the mine where i t reaches about 20 cm t h i c k n e s s a t UC 17 (39/G) and UC 20 (40/G). Minor development of t h i s clam s h e l l zone i s found at a l l l o c a t i o n s where c o r i n g p e n e t r a t e d to the top of U n i t B except d i r e c t l y below the Narrows where i t i s m i s s i n g a t JG8 (32/J) and o n l y p o o r l y developed at JB9 (34/J). The o r i g i n of the clam s h e l l bed at the base of U n i t A i s sugges-ted t o be the d i s t u r b a n c e or d e s t r u c t i o n of e x i s t i n g clam beds as the t i d a l exchange through the Narrows i n c r e a s e d . The e f f e c t of the r e c e n t and p r e s e n t h y d r a u l i c regime on the upper 10 cm of U n i t A sediments i s c l e a r l y d e p i c t e d through a s e r i e s of maps i n d i c a t i n g the d i s t r i b u t i o n of g r a i n s i z e f r a c t i o n s and t h e i r s o r t i n g . F i g u r e s 48, 49 and 50 show the r e l a t i v e d i s t r i b u t i o n of the sand, s i l t and c l a y f r a c t i o n s . F i g u r e 51 d e p i c t s the d i s t r i b u t i o n of sediment types based on the nomenclature of Shepard (1954). F i g u r e s 52 and 53 p r e s e n t the mean g r a i n s i z e d i s t r i b u t i o n (Folk and Ward, 1957) and the de-gree of s o r t i n g (Inman, 1952), r e s p e c t i v e l y . D i s t r i b u t i o n of Sand, S i l t and C l a y The most s i g n i f i c a n t sand area (Figure 48) i s from Quatsino Narrows up Rupert I n l e t . Areas where g r a v e l s r e p r e s e n t 10% or more of the sample are p a r t i c u l a r l y s i g n i f i c a n t below the Narrows and i n Rupert gap and range from angular b o u l d e r s to rounded cobbles and subangular pebbles and g r a n u l e s . Surface g r a v e l i s s u f f i c i e n t l y abundant near the Narrows t h a t i t was not u n t i l the A p r i l 1973 survey t h a t cores of sediments were recove-red i n t h i s area, with p e n e t r a t i o n of both u n i t s A and B. The 124 s ize and amount o f gravel m a t e r i a l decreases r a p i d l y away from the Narrows, where i t can be greater than 50%, to about 15% near the upper end of Rupert gap. The sand and gravels of th i s area are i n part the coarse r e s i d u a l f r a c t i o n of the deeply eroded Unit B (see Chapter IV) and i n part coarse d e t r i t u s from the shorel ine inc lud ing the estuary of the Marble R iver . The sediments suggest that strong bottom currents o r i g i n a t i n g at the Narrows move up both i n l e t s . Sand d i s t r i b u -t i o n suggests that the bottom currents are strongest up Rupert gap. As i n the case of the erosion of the very f ine s i l t s of Unit B, the depos i t ion and erosion thresholds for the sand-to-gravel s ize as shown i n Figure 43 are in the order of 50 to 100 cm/sec and greater , again i n keeping with the v e l o c i t i e s observed and predicted for th i s area i n Chapter I I I . The ent i re south side of Rupert In le t i s more than 50% sand. There i s no l o c a l drainage to contribute th i s sand and the inference i s that the bottom current that scours Rupert gap con-tinues along the south flank due to the C o r i o l i s e f f ec t . Areas of sand dominate the north side of Holberg gap but less strongly than i n Rupert gap. Strong currents along th i s northern flank would also be deduced because of C o r i o l i s e f f e c t . These deduc-t ions are supported by the seismic p r o f i l e s . Sand also dominates the shorel ine areas but should not be confused with nor obscure the more important aspect of sand 125 i n the deeps. The manner i n which the percentage sand diminishes along a north-south front of the Unit A bui ld -up of f the mine-s i t e i s a pattern repeated throughout the study. I t seems to mark a balance between the headward thrust of the t i d a l bottom currents with some sort of opposite e f f e c t . The r e s u l t i s the depos i t ion of f iner -gra ined mater ia l east of the l i n e . Streams i n th i s area probably contribute sediment to the bui ld-up of Unit A on the north f lank but are not a major f a c t o r . Figure 49, the Percentage S i l t map, supports the main features of the Percentage Sand map but with inverse proport ions: areas of low sand content are the areas of high s i l t content. While the northern f lank of Rupert In le t and up i n l e t from H o l -berg gap are the main areas of s i l t accumulation, the s i l t d i s t r i -bution about the Narrows o u t f a l l i s of p a r t i c u l a r i n t e r e s t . Rupert gap and the north side of Holberg gap are areas of moder-ate - to -h igh sand concentrations with very l i t t l e s i l t and the impl i ca t ion i s that the s i l t has been borne i n suspension up both i n l e t s away from the Narrows. However, s i l t accumulation i n the 20 - 40 percentage range i s noted along the south side of Holberg gap and also on the south side of Rupert gap near the Narrows. This d i s t r i b u t i o n i s s i g n i f i c a n t as an i n d i c a t o r of less energy along these areas, and may represent s i l t accumulated by the down-inlet currents noted i n Chapter III which has not been e n t i r e l y removed during periods of major f l u s h i n g . Low s i l t percentage along the ent i re south flank of Rupert basin again i s suggestive of higher energy along t h i s area than the northern 126 + I A +' -B + 10 + II + 12 + 13 + 14 +.15 + 16 + 17 + 18 + 19 + 20+ 21+ 22+ 23 + 24+ 25+ 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33+ 34 + 35+ 36+ 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48+ 49 + 50 + A + B + C + D + E + F + 6 + H + I +• J + K + L -r M + Figure 48. 127 + " I A i + - + B i + - + C • + - + D i + - + E i + - + F i + - + 6 i + - + H • + -1 i + .-- + J i + - + K +' - + L i + - + M i + - 4-+ 35+ 36+ 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48+ 49 + 50 + A + B 4 C ' + D + E + F + 6 + H + I + J K 4-L 4 M 4 Figure 49 . 128 + 1 2 + 3 + A i i i + - ' + - 4- - + B 1 + - + - 4 - 4^  C i 1 + - + - 4- - 4-D 1 1 + - + - 4- - 4-E i 1 1 + - + • - 4- - 4-F i 1 1 + - + - 4- - 4-6 1 1 + - 4- - 4-H i 1 1 + - 4- - 4- - 4-1 i 1 1 + - + - 4- - 4-J i 1 1 + - + - 4- ' - 4-K 1 r + - + - 4- - 4-L l 1 1 + - + - 4- - 4-M i 1 1 + - 4 - + - 4-14+15 + 16 + 17 + 18 +• 19 + 21 + 22+ 23 + 24+ 25+ 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33 + 34 +• 35 + 36 + 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48+49 + 50 + A + B 4-c 4-D 4-E. 4-F + G 4-H .4-I 4-J + K 4-L 4 M 4 Figure 50. 129 + I A + -B + -C + -0 + -E 4 -F + -G + -H 4 -I + -J + -K + -L + -M + -+ i • + i + i + + i + i + i 4 i +• + • i + • 4 i + -i + -8+ 29+ 30+ 31 + 32+ 33+ 34+ 35+ 36+ 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48+ 49 + 50 + A + B + C + D + E + F + G + H + I + J 4 K 4 L 4 M 4 Figure 51. 130 f l a n k . The r e a s o n f o r t h e s l i g h t l y s i l t i e r d e p o s i t s i n Rupert I n l e t t h a n i n H o l b e r g i s a m a t t e r f o r s p e c u l a t i o n . U n i t A de-velopment on t h e n o r t h f l a n k o f Rupert I n l e t has become s l i g h t l y more s i l t y i n i t s upper development as can be noted i n T a b l e I I I . T h i s i s i n g e n e r a l c o n t r a s t w i t h o t h e r a r e a s w h i c h e i t h e r have remained q u i t e c o n s t a n t o r have become f i n e r - g r a i n e d w i t h up-ward development. The s l i g h t i n c r e a s e i n g r a i n s i z e i n t h i s a r e a o f Rupert I n l e t may be r e l a t e d t o t h e i n t r o d u c t i o n o f mat-e r i a l from minor streams i n t h e v i c i n i t y . However, a more l i k e l y e x p l a n a t i o n appears t o be r e l a t e d t o the d i s t r i b u t i o n o f bottom-c u r r e n t energy g e n e r a t e d i n Q u a t s i n o Narrows. S i n c e t h e map s e -quence appears t o s t r e s s g r e a t e r energy d i r e c t e d up Rup e r t gap than up H o l b e r g gap, presumably i t i s n a t u r a l t o f i n d f i r s t t h e c l a y d e p o s i t s r e s u l t i n g from t h e e a r l y s t a g e s o f U n i t B e r o s i o n i n c r e a s i n g i n c o n t e n t o f s i l t upwards i n r e l a t i o n t o t h e p r e -s e n t energy l e v e l . H o l b e r g I n l e t e x h i b i t s f i n e r m a t e r i a l c a r r i e d headward by g e n t l e r c u r r e n t s . R e f e r e n c e t o F i g u r e s 43 and 44 i n d i c a t e s t h a t the s i l t r e moval from t h e Narrows o u t f a l l a r e a p r o b a b l y r e q u i r e d v e l o c i -t i e s i n e x c e s s o f 50 cm/sec, perhaps c o n s i d e r a b l y i n e x c e s s , b u t once t h e m a t e r i a l was eroded from U n i t B and i n s u s p e n s i o n i t c o u l d r e a d i l y be t r a n s p o r t e d t o t h e ob s e r v e d a r e a s o f maximum d e p o s i t i o n . 131 The Percentage C l a y map (Figure 50) i s i n g e n e r a l harmony wi t h the p r e c e d i n g maps. Areas of maximum c l a y accumu-l a t i o n are s i m i l a r to those of s i l t but whereas maximum s i l t c o n c e n t r a t i o n occurs i n Rupert I n l e t , maximum c l a y c o n c e n t r a t i o n i s i n the Holberg trough above Coal Harbour. Again, as w i t h s i l t , percentage of c l a y i s s m a l l i n Rupert gap and the n o r t h f l a n k of Holberg gap. A c l a y accumulation along the south s i d e of Holberg gap may again r e f l e c t the remnant d e p o s i t of the down-i n l e t c u r r e n t d i s c u s s e d i n Chapter I I I . There i s a s u g g e s t i o n t h a t a s l i g h t i n c r e a s e i n energy occurs a t the c o n s t r i c t i o n be-tween Mi c h e l s e n P o i n t and the S t r a g g l i n g I s l a n d s w i t h l e s s c l a y d e p o s i t e d than on e i t h e r s i d e . The i n f e r e n c e i s t h a t t i d a l - r e -l a t e d bottom c u r r e n t s may s t i l l be i n e f f e c t even a t t h i s d i s -tance up i n l e t from Quatsino Narrows. I f the bottom c u r r e n t s are s t i l l i n e f f e c t s i x m i l e s up Holberg I n l e t , then by analogy they should be i n e f f e c t through Rupert I n l e t which i s o n l y s i x m i l e s l ong and a p p a r e n t l y r e c e i v e d more of the i n i t i a l energy. F i g u r e 51 shows the d i s t r i b u t i o n of sediment types based on the c l a s s i f i c a t i o n of Shepard (1954) and i s a summation i n k i n d of F i g u r e s 48, 49 and 50. Areas of sand development i n the b a s i n are c e n t r e d about.Quatsino Narrows, Varney Bay and Hankin P o i n t and spread u n e q u a l l y up both i n l e t s . Sand develop-ments are n o t a b l y more e x t e n s i v e i n Rupert I n l e t than i n Holberg I n l e t . In f a c t , a l l of Rupert I n l e t with the e x c e p t i o n of the n o r t h - c e n t r a l f l a n k i s dominantly a sandy f a c i e s . While t h i s i s i n p a r t a t t r i b u t e d t o g r e a t e r providence of sandy m a t e r i a l from 132 the Marble River and other minor streams, the sediment d i s t r i -bution i n Rupert gap and along the south side of Rupert Inlet to i t s head supports the contention that more energy i n the form of bottom currents i s present i n Rupert than i n Holberg. Even on the north-central flank, the sediments never develop as high a: percentage of clay as i n Holberg. In Holberg gap as i n Rupert gap the main sand development i s along the north flank. On the south side of both Rupert and Holberg gaps f i n e r material sug-gests either lesser up-inlet currents or that the down-inlet currents noted i n Chapter III influence the long-term sedimenta-tion pattern along t h i s flank. Beyond Coal Harbour, Rupert trough i s dominated by very fine clayey sediments. Sediment patterns at the Michelsen-Straggling Islands c o n s t r i c t i o n and at the Dahlstrom-Norton narrows suggest that bottom-current energy af f e c t s sediment d i s t r i b u t i o n . The sediment type d i s t r i b u t i o n i n the Quatsino Narrows-Hankin Point area, when viewed i n r e l a t i o n to the observations of Chapter I I I , supports and perhaps better defines the d i s t r i b u -t i o n of bottom currents. Sediment types imply stronger up-inlet currents i n Rupert than i n Holberg Inlet but t h i s r e l a t i o n s h i p i s exaggerated by the supply of sand from the Marble River being much more available to Rupert In l e t . These currents appear to dominate the north rather than the south flank of both gaps. The dominant currents i n terms of long-term e f f e c t on sedimentation are related to dense water intrusions that follow the bottom, flowing up-inlet and displacing the resident water column. 133 Mean G r a i n S i z e and S o r t i n g F i g u r e 52 maps t h e d i s t r i b u t i o n o f G r a p h i c Mean g r a i n s i z e (M ) i n t o t h r e e broad g r o u p s : c o a r s e r t h a n 2cj) (250]i) , i n -e l u d i n g medium and c o a r s e r sand; 2<f> - 6(f), f i n e sand t o c o a r s e s i l t ; and f i n e r t h a n 6(f) (15.6u), medium s i l t and c l a y . A g a i n , the d i s t r i b u t i o n s u p p o r t s t h e p r e c e d i n g maps. F i n e m a t e r i a l i s l i m i t e d t o t h e no r t h w e s t f l a n k o f Rupert I n l e t and t o th e H o l b e r g t r o u g h above C o a l Harbour. The medium range m a t e r i a l dominates H o l b e r g gap and Rupe r t I n l e t . The c o a r s e m a t e r i a l i s r e s t r i c t e d t o R u p e r t gap and t h e so u t h f l a n k o f Rupert I n l e t . F i g u r e 53 i n d i c a t e s t h e degree o f s o r t i n g o r d i s p e r s i o n o f t h e s e d i m e n t s , u s i n g t h e G r a p h i c S t a n d a r d D e v i a t i o n ( a „ ) . I n g e n e r a l , t h e degree o f s o r t i n g i s i n d i r e c t r e l a t i o n s h i p t o t h e co a r s e n e s s o f t h e g r a i n s i z e , t h e f i n e r t h e m a t e r i a l t h e p o o r e r t h e s o r t i n g . The o r d e r o f s o r t i n g i s v e r y p o o r , g e n e r a l l y 3 - 4<f>, w i t h R u p e r t gap showing improved s o r t i n g between 1 and 2 <j>. An anomaly o f t h e s o r t i n g p a t t e r n i s t h e v e r y p o o r l y s o r t e d n a t u r e o f the s o u t h s i d e o f Rupert gap as compared w i t h t h e s l i g h t l y b e t t e r s o r t i n g on t h e n o r t h s i d e . By an a l o g y w i t h R u p e r t I n l e t , i t c o u l d be a n t i c i p a t e d t h a t t h i s v e r y p o o r l y s o r t e d a r e a would ex-tend f u r t h e r up t h e Holberg t r o u g h . The p r e s e n t d i s t r i b u t i o n s u g g e s t s t h a t o n l y v e r y f i n e m a t e r i a l e a s i l y m a i n t a i n e d i n suspen-s i o n manages t o be c a r r i e d up t h e t r o u g h . The p o o r e r s o r t i n g on the s o u t h s i d e o f H o l b e r g gap r e l a t e s t o dominant u p - i n l e t c u r -r e n t s on t h e n o r t h s i d e . 134 Figure 52. 135 + ' I A + -B + -C + -0 + -E + -F + . -6 + -H + - ' I + -J + -K . + -L + . -M + -+ - + + + + + + + ' +• + • + + -+ -+ 4-+ + + + 4-' 3 + 4 + i i - • + • - ' + 5 + 6 + 7 + 8 + 9 + i i i i i - + - + - + - + - + 10 + II + 12 + 13 + 14 + 15 + 16+17 + 18 + 19 + 20+21 + 22+ 23 + 24+ 25+ 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33 + 34+ 35 + 36 + 37 + 38+ 39+ 40+ 41 + 42 + 43 + 44+ 45+ 46+ 47+ 48+ 49 + 50 + A + B + C + 0 + E + F + G + H + I + J + K + L -* M + 136 Figure 54 plots grain size against cumulative percent-age for representative samples located -on Figure 53 from data l i s t e d i n Tables III and IV. The coarsest mean grain s i z e , 1.6<f> (0.34mm), and the best sorting, 1.5(f), occur at 13/L i n Rupert gap. Up i n l e t from the gap, material becomes progressively f i n e r and more poorly sorted. It i s in t e r e s t i n g to note that values just above the gap at J6 and just below the gap at JB9 are nearly i d e n t i c a l and very s i m i l a r to UG9 on the Holberg side of the Narrows o u t f a l l . Representative curves for locations i n Holberg Inlet show the same orderly decrease i n mean grain size with de-crease i n degree of sorting as i s apparent i n Rupert In l e t . The diagram indicates the dominant e f f e c t of the energy input of the flood tide at Quatsino Narrows on sediment dispersion i n the Holberg-Rupert basin. T a i l i n g The term t a i l i n g i s used loosely i n t h i s study to i n -clude a l l detrit u s o r i g i n a t i n g from mine a c t i v i t y which i s fine sand size (0.25 mm, 2(f>) or smaller. While concerning mainly the t a i l i n g proper from the m i l l v i a the o u t f a l l pipe, i t includes debris of similar grain size from the waste rock dump. The l a t t e r i s mainly material from b l a s t i n g , with minor sand, s i l t and clay materials from overburden s t r i p p i n g . No attempt has been made to separate material from the t a i l i n g o u t f a l l and rock dump. However, some effects of the rock dump on the t a i l i n g deposition are noted i n the discussion. 138 Walden and Duncan (1970) reviewed i n d e t a i l the pro-blems associated with underwater d i sposa l of mining and m i l l i n g wastes and general ly concluded that given appropriate chemical and phys ica l condi t ions , t a i l i n g d i sposa l i n s h a l l o w - s i l l e d fjords i s more des irable than land d i s p o s a l . They recommended that where t a i l i n g are disposed underwater, the o u t f a l l be "well below the thermocline and below the zone of trophic a c t i v i t y " where s e t t l i n g c h a r a c t e r i s t i c s of the t a i l i n g and underwater currents permit "rapid and complete settlement". The main b i o -l o g i c a l problems associated with underwater d i sposa l of non-tox ic p a r t i c u l a t e mater ia l are that i t reduces penetrat ion of sun-l i g h t , and through s i l t a t i o n buries bottom l i f e . They opposed the dumping of s tr ipped waste and overburden because i t often contains oxidized minera l i za t ion and also increases shallow t u r b i d i t y with f ine c lay mater ia l s . Pol ing (1973) i l l u s t r a t e d the capacity of sea water over fresh water to improve the sedimentation rate of t a i l i n g . He concluded that t a i l i n g emerging from the o u t f a l l at concen-tra t ions i n the order of 50% s o l i d s , as at Is land Copper, are at t h e i r maximum concentration and minimum s e t t l i n g volume. The plume forms a t u r b i d i t y current i n which the s e t t l i n g rate i s enhanced as the current i s d i l u t e d by sea water. As the t a i l i n g are d ispersed , sea water speeds the rate of sedimentation and helps prevent t u r b i d i t y . The s ize and extent of the waste rock dump over 25 years 139 was estimated by P r a t t (1970) to r e s u l t i n the formation of 700 acres of new s h o r e l i n e . The s t r i p p i n g r a t i o i s expected t o be l e s s than 3 tons of waste rock per ton of ore (Evans, 1972). Since the ore r e s e r v e s are estimated a t 280 x 10^ tons over the l i f e of the mine approximately 1,000 x 10 tons of m a t e r i a l w i l l be p l a c e d i n Rupert I n l e t , one-quarter t o o n e - t h i r d of which i s c a t e g o r i z e d h e r e i n as t a i l i n g . The broken rock w i l l occupy 6 3 about 25 to 30 x 10 yds r e t a i n e d i n a l i m i t e d area w h i l e the 6 3 t a i l i n g w i l l form 15 t o 20 x 10 yds of sediment d i s t r i b u t e d unevenly through the Holberg-Rupert b a s i n . The waste rock dump area presumably w i l l develop eastward along the shore and i n t o p r o g r e s s i v e l y deeper waters. Submarine slumps r e s u l t i n g from t h i s dumping are observed i n the s e i s m i c r e c o r d s . The geometry of the waste rock dump may a f f e c t t a i l i n g movement. G r a i n s i z e s o f d e p o s i t e d t a i l i n g are l i s t e d i n Table V. The "samples" column r e f e r s to the number of 10cm s e c t i o n s of core o r core samples i n c l u d e d i n the averaging w h i l e the "samp-l i n g s " column r e f e r s t o the number of dates from which samples are i n c l u d e d . " J " S e r i e s v a l u e s r e p r e s e n t one sampling but sometimes s e v e r a l 10cm i n t e r v a l s from the one co r e . The remain-i n g v a l u e s are f o r specimens gathered a t the Mine q u a r t e r l y survey l o c a t i o n s . "Q" s i g n i f i e s the September 1973 survey w h i l e "T" r e p r e s e n t s the t a i l i n g p o r t i o n of the specimen. D i s t r i b u t i o n and S t r u c t u r e F i g u r e 55 prese n t s an isopachous map of s e t t l e d t a i l i n g 140 d i s t r i b u t i o n i n the Holberg-Rupert bas in . The d i v i s i o n s of less than 3 cm, 3 - 25 cm and greater than 25 cm are grouped in to l i g h t , medium and heavy t a i l i n g concentrations as at September 1973. Maximum cored thickness i s 119 cm at JC20 (40/G) cored i n A p r i l 197 3. Although i n general the amount of t a i l i n g i s too small to be evaluated by seismic data , eventual ly s e i s m i c - r e f l e c -t i o n p r o f i l e s w i l l prove the best t o o l for t h i s purpose. The p r o f i l e s ind icate that the combination s l i d e and fan at the base of the trough at the o u t f a l l ponds t a i l i n g behind i t to at l eas t 7.5 metres (25 f ee t ) . The seismic sect ion (Chapter IV, Figure 40B) indicates the i n f i l l i n g and br ing ing to grade the bottom of Rupert In le t gap and the termination of th i s condi t ion below Quatsino Narrows o u t f a l l . I n f i l l i n g i n Rupert gap by t a i l -ing i s approximately 12 metres (40 f e e t ) . S i g n i f i c a n t l y , areas of th ick t a i l i n g are l i m i t e d to Rupert I n l e t . However, ear ly and continuing occurrence of traces of t a i l i n g i s recognized i n Holberg In le t jus t beyond the Straggl ing Is lands . Traces of t a i l i n g also occur i n shallow areas of Rupert In le t at depths of less than 100 feet on the north f lank and at the head of the i n l e t at the base of the t i d a l f l a t dropoff . Minor amounts of t a i l i n g are also mixed i n the sands i n Varney Bay and at the entrance to Coal Harbour but are not observed i n the inner harbour area. No i n d i c a t i o n of t a i l -ing has been noted i n numerous sampling attempts through Quatsino Narrows and down Quatsino Sound to the entrance of Neroutsos I n l e t . West of the Straggl ing Is lands , where the layer of t a i l -141 SPECIMEN LOCATION WATER SAMPLES % WT. OF -2MM FRACTION MEDIAN °G °I TEXTUR NUMBER DEPTH SAMPLING %SAND »SILT %CLAY • fl fl SHEPARD (19 Out f a l l Pipe 40/E 150 3 j 44 41 15 4.9 5.4 2.7 2.8 S i l t y Sand JC 30T 27/G 462 1 1 ' 2.0 56.8 41.2 8.45 8.9 2.8 2.6 clayey s i l t JB 5T 29/H 354 1 1 2.5 61.1 36.4 7.85 8.5 2.9 2.7 clayey s i l t JG 3T 29/G 447 1 1 10.3 61.7 28.0 7.25 7.8 2.9 3.0 clayey s i l t JG 8T 32/J 462 1 1 2.2 72.2 25.6 7.1 7.6 2.4 2.3 clayey s i l t JB 13T 36/1 450 4 19.8 65.3 14.9 5.9 6.4 2.4 2.4 sandy s i l t JC 15T 36/H 452 9 1 24.6 64.2 11.2 5.4 5.8 2.1 2.2 sandy s i l t J6T 37/G 414 5 •1 47.9 45.9 6.2 4.6 4.8 1.8 1.9 s i l t y sand J4T 38/H 384 2 1 1.1 74.8 24.1 7.4 7.8 2.3 2.3 clayey s i l t JC 19T 40/E 222 7 1 44.4 48.3 7.3 4.7 5.1 1.8 2.0 sandy s i l t JC 20T 40/G 318 12 1 • 15.0 68.0 17.0 6.3 6.7 2.4 2.5 clayey s i l t JC 23T 44/F 312 2 1 10.6 71.5 17.9 6.6 6.9 2.4 2.5 clayey s i l t JC 23SKT 44/F 312 1 10.3 73.4 16.3 6.3 6.7 2.2 2.4 clayey s i l t J3 SKT 43/G 175 1 1 14.1 60.6 25.3 7.3 7.4 2.8 2.9 clayey s i l t JC 27SKT 46/F 222 1 6.2 62.1 31.7 7.8 8.2 2.9 2.8 clayey s i l t 25 Q T 10/D 280 1 1 19.2 47.2 33.6 7.7 7.5 3.6 3.4 clayey s i l t 2 Q T 14/D 320 1 3.0 46.1 50.9 9.1 9.2 3.1 2.9 s i l t y clay 3 Q T 14/E 243 . i 1 1.4 52.6 • 46.0 8.7 9.1 3.1 2.8 clayey s i l t t 0 1 25/F 387 l 4.2 55.1 40.7 8.4 8.9 2.7 2.9 clayey s i l t 5 Q T 28/H 409 l 1 4.5 62.9 32.6 7.4 8.1 2.8 2.7 clayey s i l t 6 Q T 29/G 442 l 1 1.9 67.7 • 30.4 7.6 8.0 2.7 2.5 clayey s i l t 7 Q T 29/F 99 i 1 60.3 26.7 13.0 3.4 4.7 2.8 2.9 s i l t y sand 9 - T 34/J 525 16 5 9.9 71.6 18.5 6.3 6.9 2.4 2.4 clayey s i l t 13 - T 36/H 500 12 6 28.5 58.7 12.7 5.6 5.9 1.9 2.1 sandy s i l t 14 - T 36/1 260 2 2 5.8 63.9 20.3 6.7 6.8 2.7 2.8 clayey s i l t 15 - T 40/E 170 4 3 11.0 68.3 20.7 6.3 6.9 2.6 2.6 clayey s i l t 16 - T 40/F 325 9 5 16.7 67.1 16.2 6.1 6.7 2.4 2.5 sandy s i l t 17 - T 40/G 340 11 5 5.9 70.4 23.7 7.0 7.3 2.6 2.6 clayey s i l t 19 Q T 45/F 228 1 1 14.4 57.0 28.6 7.1 7.6 3.4 3.1 clayey s i l t GRAIN SIZE DATA FOR TAILING SEDIMENTATION. (M^ (Mean) and 0 j (Inclusive Graphic Std. Dev.) follow Folk and Ward (1957), whila o G (Graphic Std. Dev.) follows Inman (1952)] 142 + 1 + 2 + A i r + - + - + B i i + - + - 4-C i 1 + - + - + D 1 + - + - 4-E . i 1 + - + - 4-F i l + - + - 4-i 1 4 - + - 4 H • 1 + - + - 4-1 i 1 + - + - + J i l + - + - 4-K i 1 + + - 4-L i I + - +' - + M i 1 + - + - 4 5 + 6 + 7 + 8+ . 9 + i i I I i - + - + - 4- - 4- - 4-10 + || 4 |2 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20+ 21 + 22+ 23 + 24+ 25+ 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33 + 34+ 35 + 36 + 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48+ 49 + 50 + TAILING DISTRIBUTION September 1973 AFTER FIRST TWO YEARS OF PRODUCTION HEAVY p l i >25 cm. MEDIUM 3 to 25 cm. Trace to 3 cm. - 4 - 4 - — 4 - 4 . -A 4 B 4 c 4 D 4 E 4 F 4 G 4 H 4 I 4 J 4 K 4 L 4 M 4 Figure 55. 143 i n g i s very t h i n , i t e x h i b i t s a c o l o u r change, perhaps due to o x i d a t i o n , t o a dusky yellow-brown when wet, d r y i n g t o yel l o w -brown. T a i l i n g p e r s i s t as f a r as S t a t i o n 25 (10/D) a t the Dahlstrom-Norton narrows but cannot be d e f i n e d w i t h c e r t a i n t y at S t a t i o n 26 (4/C). Evans (1973) estimates 75 x 10^ c u b i c f e e t of p a r t i c u -l a t e t a i l i n g were d i s c h a r g e d d u r i n g the f i r s t p r o d u c t i o n year. Assuming approximately 150 x 10 c u b i c f e e t of t a i l i n g d i s c h a r g e s to September 1973, Holberg I n l e t appears to have r e c e i v e d a p p r o x i -mately 11.5 x 10 6 c u b i c f e e t or about 7.5% of very f i n e t a i l i n g w i t h an average mean g r a i n s i z e of 4u.(8<f>). There i s c o n s i d e r a b l e d i f f e r e n c e between t a i l i n g de-p o s i t i o n i n Rupert I n l e t and i n Holberg. In Rupert I n l e t below the Narrows a t S t a t i o n 9 (34/J), there were 2.5 cm of t a i l i n g i n June 1972, but by December 1972 there were 47 cm and t h i s r e -mained between 40 and 50 cm to September 1973. At t h i s l o c a t i o n there i s very l i t t l e i n t e r m i x i n g of n a t u r a l sediments and t a i l i n g . The c o l o u r i s medium gray when wet to l i g h t gray when dry, w i t h a tr a c e of br a s s y m e t a l l i c f l e c k s . There are weak rhythmic sandy p a r t i n g s a t about 1 to 2-cm i n t e r v a l s but t h i s i s more pronounced up i n l e t a t S t a t i o n s 15, 16 and 17. Up i n l e t i n Rupert gap a t S t a t i o n 13 (36/H), the c y c l i c , t h i n , sandy s t r e a k s are not observed but there are zones of i n -c r e a s i n g sandiness towards the base. Here the wet c o l o u r i s 144 o l ive -gray and the dry colour l i g h t o l ive -gray suggesting i n t e r -mixing of natura l dark o l i ve -gray sediments. The bottom at Stat ion 13 has on several occasions been too hard for the Mine Survey to core. Grab samples taken at two such times, June 1973 and September 1973, show the t a i l i n g to have been strongly win-nowed to a coarser s i l t with median and mean gra in s ize of 44u and the best sor t ing observed i n the study at 0.8(f) (°Q) to 1.0(f) (a .^) . I t i s i n t e r e s t i n g to note that the current meter which was l o s t , presumed bur ied , i n September 1973 was very near to Stat ion 13. Near the t a i l i n g o u t f a l l at Stat ion 15 (40/E), t h i c k -ness increased from 0 cm i n June 1972 to 42+cm i n June 1973. C y c l i c sedimentation i s ind icated by t h i n and th ick interbeds , but less r e g u l a r l y than at other s ta t ions . There are l o c a l marked amounts of sulphide ore f lakes . Down slope from the o u t f a l l p ipe , Stat ion 16 (40/F) has had i n excess of 45 cm of t a i l i n g present since before June 1972. Rhythmic sand partings are more regular than at Stat ion 15 but the e f fec t i s not as developed as at Stat ion 17 further down s lope. At Stat ion 17 (40/G) rhythmic sandy par t ings , approximately 8 per 10 cm, are common throughout the cored sec-t i o n . Thickness of sandy interbeds ranges from 1 mm to 1 cm. Eastward at Stat ion 19 (45/F) t a i l i n g thickened from 2 cm i n June 1972 to 6 cm i n September 197 3. Mixing with natura l 145 sediments i s common, wit h b i o t u r b a t i o n a l s o observed. The t a i l -i n g are o l i v e - g r a y when wet to l i g h t o l i v e - g r a y when dry. At S t a t i o n 20 (45/G) t r a c e s of t a i l i n g were f i r s t observed i n June 1972, and by 1973 had i n c r e a s e d i n t h i c k n e s s to 3 cm i n c l u d i n g i n t e r m i x e d n a t u r a l sediments. No graded bedding has been observed, d e s p i t e the prob-a b i l i t y t h a t a t l e a s t one or two t u r b i d i t y c u r r e n t s o c c u r r e d . I f not a continuous f e a t u r e of sedimentation, these c u r r e n t s would be a n t i c i p a t e d a t the time of the major submarine slumps and s l i d e s o f f the t a i l i n g f an and waste rock dump. Perhaps these events are masked because the m a t e r i a l i s very f i n e - g r a i n e d and of uniform c o l o u r . Perhaps they never o c c u r r e d e x t e n s i v e l y . The rhythmic nature of the very t h i n sand i n t e r b e d s i s sug-g e s t i v e of o r d e r l y winnowing by i n t e r m i t t e n t c u r r e n t s . These f e a t u r e s are a s c r i b e d t o the t i d a l - o r i g i n a t e d bottom c u r r e n t s which f l u c t u a t e i n energy with water d e n s i t y and f l o o d t i d e h e i g h t . T a i l i n g are observed i n Varney Bay a t S t a t i o n 10 (35/L) mixed wi t h n a t u r a l sands of the es t u a r y of the Marble R i v e r , i n -f i l l i n g the sands to 3 or 4 cm. There i s some p o s s i b i l i t y of minor i n f i l l i n g o f sands with t a i l i n g upstream a t S t a t i o n 11 (3 6/L). The t a i l i n g i n Varney Bay are presumably drawn from the main b a s i n as m a t e r i a l i n suspension by the e s t u a r i n e c i r c u l a -t i o n of the Marble R i v e r . 146 Elsewhere along the shore l ine , at Stat ion 12 (35/G) t a i l i n g have been increas ing ly mixed with the sandy, bottom since December 1972. At Stat ion 18 (46/D) t a i l i n g form a very t h i n topping on the natura l sediments. T a i l i n g do not reach Stat ion 21 (49/F). At Stat ion 14 (36/1) on the south wal l of Rupert gap t a i l i n g have gradual ly increased to 6 cm by September 1973 but are intermixed i n part with natura l sediments as evidenced by the greenish co loura t ion . T a i l i n g i n Holberg In le t trough opposite Coal Harbour were 1 cm thick i n June 1972 af ter s ix months' dumping. By September 197 2 they had reached up i n l e t beyond the Straggl ing Islands with thicknesses of about 1 cm at Stat ion 2 (14/D) and Stat ion 4 (25/F), and 3 cm at Stat ion 6 (29/G). No appreciable increase i n thickness was noted u n t i l June 1973. Meanwhile the sediments i n the Holberg trough became increas ing ly bioturbated and mixed with natura l sediments. By June 1973 the amount of t a i l i n g at Stat ion 6 increased to 4.5 cm and at S tat ion 4 to 3 cm. By September 1973 there were 7 cm at Stat ion 6, 6 cm at Stat ion 5 (28/H) and 1.5 cm at Stat ion 2. T a i l i n g mixed with sandy bottom have been noted since March 1973 at Stat ion 7 (29/F), c lose to the entrance to Coal Harbour. T a i l i n g i n Holberg In le t are very f ine grained and without any rhythmic part ings as i s sometimes observed i n Rupert I n l e t . From the scant data at hand the main period of growth i n t a i l i n g sedimentation i n Holberg Inlet appears to be la te spring and summer. There i s strong b i o -turbat ion , mainly by worms, as evidenced by burrows and f e c a l 147 p e l l e t s of n a t u r a l sediments i n t o the t a i l i n g zone. The t a i l i n g are i n many p l a c e s t i n t e d o l i v e - g r a y . Mean G r a i n S i z e and S o r t i n g The g r a p h i c mean s i z e (Mz) of the t a i l i n g i s presented i n F i g u r e 56 and ranges from medium s i l t (6<j)) to c l a y (9cj>) . De-s p i t e the marked d i f f e r e n c e i n source l o c a t i o n f o r the t a i l i n g as compared with U n i t A, except f o r the area c l o s e t o the mine there i s a s t r i k i n g s i m i l a r i t y i n d i s t r i b u t i o n p a t t e r n between F i g u r e 56 and F i g u r e 52. Immediately down slope from the o u t f a l l p i p e t h e r e i s an area of c o a r s e r m a t e r i a l from e a r l y dropout as would be a n t i c i p a t e d . The area of bottom c u r r e n t winnowing i n Rupert §ap seen through the U n i t A s e r i e s maps again p e r s i s t s i n the t a i l i n g d i s t r i b u t i o n ; the unique c o n d i t i o n s a t S t a t i o n 13 (36/H) have a l r e a d y been d i s c u s s e d . Headward up both Rupert and Holberg i n l e t s , the mean g r a i n s i z e of the m a t e r i a l becomes i n -c r e a s i n g l y f i n e r e a c h i n g i t s f i n e s t c o n s i s t e n c y between the S t r a g g l i n g I s l a n d s and the Dahlstrom-Norton a x i s . The coarsen-i n g noted on t h i s a x i s (10/D) i s thought due to winnowing, but s i n c e i t i s a t the d i s t a l end of 'sedimentation i t may be the r e -s u l t o f contamination by n a t u r a l sediments. F i g u r e 57 presents the Graphic Standard D e v i a t i o n ( a G ) f o r the t a i l i n g . Again, as seen i n F i g u r e 53 f o r U n i t A, the degree of s o r t i n g of the t a i l i n g i s bes t where the mean g r a i n s i z e i s c o a r s e s t but d i m i n i s h e s w i t h g r a i n s i z e . The bes t s o r t -i n g occurs i n areas of c o a r s e s t t a i l i n g (Figure 56) immediately 148 + I A + -B 4 -C + -D + -E + -2 + 3 + 4 + 5 + ' I I - + - + - + 6 + 7 + 8 + 9 + 1 ' • ' - + - + - + - + 10 + || + V 3 ; H r , 5 ; , V 7 ; l v ' ' H I • | • • . . . - 49 + 50 + A + B + C + D + E + F + ' G + H + f + J 4 K 4 L 4 M 4 Figure 56. 149 + "I + 2 + A , + - + 3 + 4 + i i - •+ - + 5 + 6 + 7 + 8 + 9 • + • ' > i , - + - + - + • • - + - + 10 + If + 12 + 13 + 14 +.15 + 16 + 17 +18 + 19 + 20+ 21 + 22 + 23 + 24+ 25+ 26+ 27+ 28+ 29+ 30+ 31 + 32+ 33+ 34+ 35+ 36+ 37 + 38+ 39+ 40+ 41 + 42+ 43+ 44+ 45+ 46+ 47+ 48 + + - + - + -49 + 50 + A + B + C + 0 + E + F" + G + H + I + + K + L 4 M + Figure 57 . 150 at the o u t f a l l pipe and at Rupert gap, while the poorest sort ing occurs i n Holberg i n the deeper trough above the Straggl ing Islands and i n Rupert near the head of the i n l e t . Size d i s t r i b u t i o n and sor t ing of the t a i l i n g are i l l u s -trated i n graph form by Figure 58 which uses representat ive sam-ples from the September 1973 survey, as indicated on Figure 57, to compare mean gra in s ize and sort ing of the sediments i n Rupert In le t and i n Holberg In le t i n the same fashion used i n Figure 54. Figure 58 i s centred about Rupert gap as the l o c a -t i o n of maximum bottom energy. The r ight-hand side presents the curves for the t a i l i n g taken d i r e c t l y from the o u t f a l l pipe and those for 16Q, 17Q and 19Q down s lope, then up i n l e t . This com-parison i l l u s t r a t e s f i r s t the reduct ion i n gra in s ize accompanied by improved sort ing then by poorer sor t ing towards the head of Rupert I n l e t . Down i n l e t towards the Narrows, Q13 i n Rupert gap shows the marked improvement i n sor t ing with the accompanying increase i n diameter. The le f t -hand side of Figure 58 repeats 13Q for comparative purposes. Then through a sequence 9Q, 6Q, 4Q and 2Q the order ly progression up Holberg In le t of the decrease of s ize with accompanying decrease i n sor t ing i s unmistakable. Another approach to the data i s presented i n Figures 59 and 60 i n s a n d - s i l t - c l a y ternary diagrams with locat ions on Figure 46. In Figure 59 t a i l i n g at the o u t f a l l are seen-to"lose part of t h e i r c lay f r a c t i o n i n the upper s lope, then progress-i v e l y lose sand and gain c lay approaching the south side of 151 F i g u r e 58. G r a p h i c P r e s e n t a t i o n o f G r a i n S i z e D i s t r i b u t i o n and S o r t i n g o f T a i l i n g About Rupert Gap. 152 CLAY F i g u r e 60 F i g u r e 59. F i g u r e 60. SAND so* SILT T e r n a r y P l o t I l l u s t r a t i n g M o d i f i c a t i o n o f T a i l i n g T e x t u r e from T a i l i n g O u t f a l l P i p e t o H o l b e r g I n l e t . T e r n a r y P l o t I l l u s t r a t i n g M o d i f i c a t i o n o f T a i l i n g T e x t u r e f r o m O u t f a l l P i p e P r o g r e s s i n g up R u p e r t I n l e t . 153 Rupert trough where the sand f r a c t i o n has diminished to about 5%. Moving down i n l e t , the t a i l i n g i n Rupert gap become nearly equal parts sand and s ' i l t with about 5% c l a y . However, below Quatsino Narrows the mater ia l i s again very s i m i l a r to mater ia l at the base of the slope of f the mine s i t e , being b a s i c a l l y a s i l t with less than 5% sand and 25% c l a y . Westward up Holberg gap, a s ign-i f i c a n t feature not seen i n the other maps i s represented by an increase i n sandy mater ia l up to about 15% at JC 3 (30/H) at the expense of the s i l t f r a c t i o n . This coarsening i s in terpreted as representat ive of an increase i n bottom energy i n Holberg gap. While the lesser magnitude of the percentage of sand may be suggestive of less energy i n Holberg than i n Rupert I n l e t , the two s i tuat ions may not be comparable because the percentage of coarser mater ia l a v a i l a b l e i n the t a i l i n g of Holberg In le t i s less than i n Rupert. Above Holberg gap the mater ia l returns to less than 5% sand and further up the trough the s i l t f r a c t i o n i s progress ive ly replaced by the c lay f r a c t i o n u n t i l above the Straggl ing Islands the c lay f r a c t i o n (<2u) represents over 50% of the t a i l i n g . From the t a i l i n g o u t f a l l to the base of the Rupert trough Figure 60 i s the same as Figure 59. However, proceeding headward up Rupert there i s an increase i n s i l t and sand, then a loss of s i l t but an increase i n sand to about 15%. This i n -crease of coarser mater ia l may be re la ted to improved winnowing but more probably i s re la ted to in troduct ion of a d d i t i o n a l t a i l -ing - s i zed mater ia l from the waste rock dump. Closer to the head 154 of Rupert Inlet the t a i l i n g become almost free of sand u n t i l at JC 27 (46/F) they are very similar to those i n Holberg trough opposite Coal Harbour. Tracer Study Mine personnel car r i e d out a tracer study of bottom sediment movement during a period of maximum spring tide i n mid-December 1973 (see Chapter I I I , Figures 28 and 31) i n which the author was an observer. Rhodamine B, which fluorescently coats p a r t i c l e s on contact, was mixed with sea water to a density s l i g h t l y greater than the bottom water. The material was re-leased on bottom at 525 feet d i r e c t l y between Quatsino Narrows and Hankin Point. Release was coincident with ebb slack water at 2000 hours on December 10. Current meter Runs 10 and 11 were simultaneously i n operation i n Rupert gap. The area about the release s i t e was sampled throughout the flood t i d e by Niskin samplers at 4 to 8 feet off bottom. Dur-ing t h i s period only two showings of the tracer were found: one d i r e c t l y up slope towards the Narrows at 425 feet while the second was d i r e c t l y towards Hankin Point at 4 35 feet. Both ob-servations were i n the f i r s t half of the flood period. Both sug-gest l o c a l turbulence but not movement up i n l e t . This i s i n keeping with the observation of Chapter I I I , recognizing that down-inlet bottom currents during flood tide are convergent be-low the Narrows. 155 On December 12, a day and a h a l f l a t e r , t h e Mine p e r -s o n n e l took grab samples from t h e t r a c e r drop a r e a up b o t h R u p e r t and H o l b e r g gaps. Sampling was l i m i t e d t o t h e base o f t h e t r o u g h . These samples i n d i c a t e d d i s p e r s i o n o f sediments from the p o i n t • o f s t a i n i n g l e s s t han one m i l e up Rupert I n l e t and s l i g h t l y more t h a n one m i l e up H o l b e r g . T u r b i d i t y M i n e - o r i g i n a t e d t u r b i d i t y i s p r e s e n t t h r o u g h much o f t h e water column and over the major p a r t o f t h e b a s i n . P r e s e n t d a t a on t u r b i d i t y from v a r i o u s s o u r c e s a r e r e p o r t e d w i t h o b s e r v a -t i o n s on t h e i r r e l a t i o n s h i p t o c i r c u l a t i o n s e d i m e n t a t i o n . The w r i t e r spent a week i n t h e f i e l d a s s i s t i n g i n i n i t i a l t u r b i d i t y s t u d i e s u s i n g t r a n s m i s s o m e t r y . I n even g e n t l e c u r r e n t s , v e r y f i n e t a i l i n g m a t e r i a l may remain suspended f o r l o n g p e r i o d s o f t i m e as i n d i c a t e d i n F i g u r e 44. The w i d e s p r e a d d i s t r i b u t i o n o f t a i l i n g t h r o u g h o u t t h e H o l -b e r g - R u p e r t b a s i n , documented i n F i g u r e s 55, 56 and 57, r e f l e c t s t h e d i s p e r s i o n o f f i n e m a t e r i a l s headwards i n b o t h i n l e t s . The l e a d edge of t a i l i n g d i s t r i b u t i o n i n H o l b e r g I n l e t i s a t l e a s t 13 m i l e s from t h e s o u r c e a t t h e o u t f a l l p i p e . The sediments a r e e v i d e n c e o f t h e t u r b i d i t y . Because o f t h e manner of c o l l e c t i o n o f a v a i l a b l e d a t a , i n t h i s d i s c u s s i o n t h e term, " t u r b i d i t y " , e x c l u d e s m a t e r i a l w i t h i n one o r two metres o f the sediment i n t e r -f a c e w h i c h , as seen i n F i g u r e 45, i s t h e v e r y zone i n w h i c h t h e most s i g n i f i c a n t sediment l o a d o c c u r s . T u r b i d i t y i n t h i s d i s -156 cussion relates to the background l e v e l of t u r b i d i t y of Figure 45 and excludes the load picked up and dropped with each t i d e . T a i l i n g Studies E l l i s (197 2) reviewed various t u r b i d i t y surveys to A p r i l 1972, the f i r s t six months of operation. The f i r s t month of operation (October 1971) showed the t a i l i n g f i e l d to have spread about one and one-quarter miles headward and two miles mouthward from the t a i l i n g o u t f a l l and to be consistently be-low 200 feet. By A p r i l 1972 the main t a i l i n g f i e l d had spread generally throughout Rupert Inlet below 120 feet, being shallow-est near the o u t f a l l and dropping below 200 feet both headward and mouthward i n less than a mile from the o u t f a l l . In the v i c i n i t y of the junction of Rupert and Holberg i n l e t s with Quatsino Narrows and Varney Bay, the t a i l i n g f i e l d was often diffused, with the diffused material extending upwards to 30 feet from the surface. E l l i s noted that "low t u r b i d i t y clouds of t a i l i n g d r i f t i n the depth range of 30 - 100 feet i n Rupert In l e t " . These early observations are i n t e r e s t i n g as the t a i l i n g concentrations did not as yet mask the separate elements of the d i s t r i b u t i o n system. In review, i t seems l i k e l y that the i n i t i a l t a i l i n g t u r b i d i t y f i e l d was spread both headward and mouthward rather quickly by currents. When the low-lying t u r b i d i t y f i e l d reached the v i c i n i t y of Quatsino Narrows, i t was p a r t i a l l y d i s -persed by t i d a l currents so that the dispersed f i e l d nearly 157 reached the surface . A poss ib le explanation for the " turb id i ty clouds" above the main f i e l d i s that they are "batches" of sus-pended t a i l i n g moved to a high l e v e l i n the water column by currents of one f lood t ide then progress ive ly moved up i n l e t i n response to i n t r u s i o n of subsequent f lood t i d e s . The i n t r u s i o n of the f lood t ide at various l eve l s i n the water column of the basin must l i f t that part of the turb id layer above the i n t r u -s ion even higher i n the column. This r e p e t i t i v e i n t r u s i o n with the r e l a t e d , layered , current s tructure i s p a r t i c u l a r l y conducive to maintaining very f ine mater ia l i n suspension. Experimental studies of the t u r b i d i t y have been per-formed, notably those reported by L i t t l epage et aJL (197 2) and L i t t l epage (1974). L i t t l epage e t al^ (1972) noted t u r b i d i t y r e -la ted to s t r a t i f i e d pos i t ions i n the water column but found l i t t l e s ize d i f f e r e n t i a t i o n of the suspended mater ia l with s p e c i -f i c turb id s t r a t a . A Rhodamine B dye tes t at the o u t f a l l i n d i -cated movement of the mater ia l i n the order of 1000 f t / h r (approximately 8.5 cm/sec) over the f i r s t e ight hours, with the d i s t r i b u t i o n down slope and both s l i g h t l y u p - i n l e t and down-inlet . The east-west d i s t r i b u t i o n i s i n keeping with the bottom current observations of Chapter III (Run 4) with the down-slope move-ment ass i s ted by the higher density of the o u t f a l l plume. At the o u t f a l l , between 55 and 60% of the t a i l i n g by weight are medium s i l t s i z e , 23.3u (5.5$) and f i n e r (Vreudge, 1971; Present Study). Of th i s f r a c t i o n more than 50% of the 158 p a r t i c l e s by number are l e s s than 2u (9$) w i t h an a d d i t i o n a l 45% between 2 and 4u (8<j)) ( L i t t l e p a g e , 1974) . While i t r e p r e s e n t s a s m a l l p a r t of the t a i l i n g by weight, the v ery f i n e s i l t and c l a y f r a c t i o n which i s so mobile r e p r e s e n t s a l a r g e f r a c t i o n of the t a i l i n g by number of p a r t i c l e s . Samples of the t u r b i d i t y f i e l d a t v a r i o u s l e v e l s from f i v e s t a t i o n s along the a x i s of Rupert I n l e t ( l i t t l e p a g e , 1974) noted a r e d u c t i o n of the 9a) m a t e r i a l to as low as 30% w i t h a r e l a t i v e g a i n i n the 8(J> s i z e . T h i s v a r i a -t i o n may be due l a r g e l y to f l o c c u l a t i o n of the c l a y s i z e m a t e r i a l . M o n i t o r i n g Program The most comprehensive t u r b i d i t y data r e s u l t from a monthly m o n i t o r i n g program of the mine at s i x l o c a t i o n s , S t a t i o n s A t o F (Figure 61). However, these data w i l l remain of l i m i t e d use u n t i l they can be r e l a t e d to t i d e - o r i g i n a t e d c u r r e n t p a t t e r n s w i t h i n the water column. P e l l e t i e r (1974b) summarized the t u r b i d i t y data on graphs f o r v a r i o u s water column i n t e r v a l s , ex-c l u d i n g v a l u e s near the sediment i n t e r f a c e . P e l l e t i e r ' s graphs, which show e r r a t i c d i s t r i b u t i o n d i f f i c u l t t o c o r r e l a t e between s t a t i o n s or w i t h seasonal v a r i a t i o n s , have been f u r t h e r reduced by t a k i n g median val u e s of the s l o p e s through two stages, then c r e a t i n g a smooth curve. F i g u r e 62 p r e s e n t s t u r b i d i t y i n the lower 200 f e e t of water column at f o u r s t a t i o n s A,.-7F, C and D. The e f f e c t on t u r b i d i t y of the s t a r t of mine p r o d u c t i o n i n Octo-ber 1971 can be seen immediately at S t a t i o n A, p r o g r e s s i v e l y l a t e r a t S t a t i o n s F and C, and i s probably not observed at S t a t i o n D. S t a t i o n A shows a c y c l i c a l p a t t e r n of i r r e g u l a r 159-length but i n d i c a t i n g r e p e t i t i v e minima and maxima median values . Headward i n Rupert In le t at Stat ion F , the t u r b i d i t y shows a sub-dued but re la ted c y c l i c a l e f f ec t with increas ing t u r b i d i t y reach-ing l eve l s i n the same order as minima of the cycles at Stat ion A. T u r b i d i t y at Stat ion C i s much more subdued than at A or F . While the curve for Stat ion C does suggest an increased back-ground t u r b i d i t y re la ted to mine a c t i v i t y , the year ly low which occurs about September i s not appreciably higher i n 1972 and 1973 than i n the pre-product ion year 1971. A high value i n ear ly summer 19 71 indicates that under even normal condit ions apprec i -able t u r b i d i t y can be present i n the lower water column. None-the less , the e f fec t of mine a c t i v i t y i s c l e a r l y d i s c e r n i b l e at Stat ion C. P r o f i l e s from Stations E and B i n deep water close to the Narrows are presented i n greater d e t a i l i n Figures 63 and 64, r e s p e c t i v e l y , with the i n t e r v a l s summarized i n the same manner. Stat ion E between Kenny and Hankin Point i s i n the area where E l l i s (1972) ear ly noted d i spers ion of the deep t a i l i n g f i e l d . While the record i s as yet too b r i e f , Stat ion E appears to have an unsymmetrical cyc le with an abrupt r i s e i n t u r b i d i t y i n the l a s t quarter of the year reaching a peak i n January, followed by an uneven lowering of t u r b i d i t y l e v e l to September-October the fo l lowing year. This period i n 1972 i s of p a r t i c u l a r i n t e r e s t because the t u r b i d i t y l e v e l was r e l a t i v e l y low and nearly equal throughout the ent i re water column. The cond i t ion , which i s a lso marked by high s a l i n i t y throughout the water column (Figure 4), 161 T U R B I D I T Y B O T T O M 200' Station A Station F *—. Station C — Station D 1973 T — i —i—r— I 0 F i g u r e 62. 162 F i g u r e 63. T U R B I D I T Y - S T N . B • Top 2 0 0 ' Mid 2 0 0 ' Bottom IOO' Figure 64. 164 may be i n d i c a t i v e of the period of maximum i n t r u s i o n of deep water. The event i s not repeated i n 197 3. The base l e v e l for t u r b i d i t y for a l l horizons at a l l s tat ions except D, i s noted to increase i n October-November 1971 then r i s e to new l eve l s at the same time i n 1972. This i s p a r t -i c u l a r l y i l l u s t r a t e d by t u r b i d i t y l eve l s i n the upper 200 feet . At Stat ion B (Figure 6 4) i n Holberg gap, the t u r b i d i t y pattern bears a subdued s i m i l a r i t y to Stat ion E (Figure 63). The i n -crease i n t u r b i d i t y i n the l a s t quarter i n each year i s s t i l l obvious; however, a marked high occurs i n mid-summer of 1973 i n the bottom layer . A s i m i l a r feature i s noted at Stat ion A (Figure 62). This high t u r b i d i t y i n the bottom waters at Stations A and B i s co incident with a minor high i n t u r b i d i t y at Stat ion E . While not reso lved , there i s an apparent r e l a t i o n s h i p between stat ions evidencing c y c l i c a l pat terns , poss ib ly dependent upon the volume and depth of i n t r u s i o n of spring f lood t i d e s . I t i s of casual i n t e r e s t to note that the bottom waters at Stat ion C further up Holberg In le t have t u r b i d i t y i n the same order as the surface waters at Stations E and B. Surface Observations Surface t u r b i d i t y with gray co lourat ion obviously r e -lated to t a i l i n g has been observed with increas ing frequency during the second operat ional year i n the area about Hankin Po in t , often re la ted to spring f lood t i d e s . The d isco loured waters appear f i r s t o f f Hankin Po int , then separate about the Point and 165 are observed several hundred yards both east and west along the shore. During ebb t ide the gray t u r b i d water i s drawn out thro -ugh the Narrows into Quatsino Sound where i t extends on occasion to the mouth of Neroutsos I n l e t . A secondary area of gray t u r -b i d surface water i s seen o f f the waste rock dump i n Rupert I n l e t . P e l l e t i e r (1974a) notes the surface appearance of t u r -b id water at Hankin Point occurs la te i n the f lood t i d e , approxi -mately one and a ha l f hours before high s lack water. The f i r s t appearance i s i n b o i l s c lose to the Po in t . These observations i n conjunction with the bottom current observations of Chapter III suggest that upward pressures below the Narrows o u t f a l l caused by the converging bottom currents , develop s u f f i c i e n t l y that as the f lood t ide begins to decay, turb id mater ia l i s intermixed to a higher l e v e l , appearing f i r s t at the surface i n the turbulent b o i l s . This process would cause a v e r t i c a l s ift ing-winnowing ac t ion i n which the f ine mater ia l enters current patterns of the water columns while the coarser mater ia l remains captured below the Narrows u n t i l a dense inflow scours the bottom and c a r r i e s the mater ia l up i n l e t . The nature and d i s t r i b u t i o n of t u r b i d i t y caused by mine a c t i v i t y i n the Holberg-Rupert basin represents a major area for future research. The present study through observations of cur -rents near the sediment-water in ter face c l e a r l y requires r e -v i s i o n of the pre-operat iona l appra i sa l of the i n t e n s i t y , dura-t i o n and d i r e c t i o n of bottom currents . A s i m i l a r problem ex is t s 166 for the ent i re water column where layer ing and mixing are i n d i c a -ted by the t u r b i d i t y ( E l l i s , 1972) and micro-temperature patterns (Drinkwater, 1973). Such research would improve understanding of the complicated movements i n the t u r b i d i t y f i e l d as expressed i n the monthly t u r b i d i t y reports of the mine survey. The work i s fundamental to any f i n a l r e so lu t ion to s a t i s f a c t o r y submarine t a i l i n g d i sposa l i n the basin and would improve understanding of current motion i n other s h a l l o w - s i l l e d i n l e t s . Summary The sediments ind icate the past and present contro l on natura l sedimentation and how t a i l i n g introduced into the present system are being d i s t r i b u t e d . Sediments from cores and samples taken p r i o r to mine a c t i v i t y i n October 1971, then quarter ly to September 197 3, have been analyzed for s t r u c t u r e , gra in s ize and s o r t i n g . A l l cores were s p l i t and examined i n the laboratory . Grain s ize analys is was by the hydrometry method with the data computerized to provide s a n d - s i l t - c l a y r a t i o s and to present cumulative per cent i n graphic form. An overlay to the graphic presentat ion permitted data conversion, enabling c a l c u l a t i o n of mean gra in s ize and of standard dev iat ion indices to s o r t i n g . Two uni ts are recognized i n the natura l sediments: Unit B, the lower and Unit A, the upper. Since t a i l i n g depos i t ion rests on Unit A , the study concentrated on the upper 10 cm of that uni t as the best i n d i c a t o r of the p r e v a i l i n g sedimentation regime. 167 Unit B was penetrated only along the deep axis of the basin from lower Holberg In le t to middle Rupert I n l e t . I t i s a f l a t - l y i n g , uniform, gray, c layey s i l t and represented depos i -t i o n p r i o r to the e f f ec t ive connection of Quatsino Sound to the Holberg-Rupert basin through Quatsino Narrows. Unit A i s eroded and r e d i s t r i b u t e d Unit B sediments plus a d d i t i o n a l sedimentation. Sediment transport of Unit A i s headward away from Quatsino Narrows with depos i t ion mainly above Coal Harbour i n Holberg In le t and on the north f lank of Rupert In le t o f f the mine s i t e . Unit A, general ly dark o l i v e - g r a y , i s h ighly v a r i a b l e i n gra in s ize from sand to c lay with minor gravels below Quatsino Narrows. Mapping of the upper 10 cm of Unit A shows that coarse c l a s t i c dominates the area beneath Quatsino Narrows extending up Rupert gap and to a lesser degree up Holberg gap, with f ine mater ia l up i n l e t at the s i t e s of maximum depos i t ion . Sort ing i s poor but shows improvement along the north side of Holberg gap and i s markedly improved i n Rupert gap. The sor t ing corroborates the eros iona l -depos i t i ona l pattern r e s u l t i n g from dominant bottom currents o r i g i n a t i n g at the Narrows and extending up both i n l e t s . The sediments i n f e r the strongest bottom currents occur i n Rupert gap. T a i l i n g are dominantly s i l t s i z e , with r e s u l t i n g depos-i t s ranging from s i l t y sand to s i l t y c l a y . Thickest t a i l i n g de-pos i t s are l i m i t e d to Rupert In le t and extend from the t a i l i n g o u t f a l l to about half-way to the head of the i n l e t , and down i n -168 l e t through the Rupert gap to below the Narrows. Thickest t a i l -ing appear to be ponded behind the t a i l i n g fan exceeding 25 feet , as we l l as i n f i l l i n g l o c a l topography i n Rupert gap to 40 feet . T a i l i n g d i s t r i b u t i o n present ly extends from the head of Rupert In le t up Holberg In le t to the Dahlstrom-Norton narrows. About 7.5% of the t a i l i n g mainly of very f ine s i l t to c lay s ize are be-ing deposited i n Holberg I n l e t . The gra in s ize d i s t r i b u t i o n and sor t ing show the coarsest t a i l i n g and the best sor t ing i n Rupert gap, confirming the evidence of strong bottom currents i n t h i s area. In Rupert I n l e t , theethicker sect ions often exhibi ted c y c l i c a l f-irie grained beds separated by very t h i n , sandy p a r t -ings which are a t t r ibuted to sor t ing by in termit tent t i d e - r e -la ted bottom currents . In areas of less t a i l i n g sedimentation, b io turbat ion was noted. No graded bedding as evidence of t u r -b i d i t y currents has been observed. Mine-or ig inated t u r b i d i t y i s caused by the very f ine f r a c t i o n of the t a i l i n g . More than ha l f the t a i l i n g by weight are less than medium s i l t s ize (<23.3y) and of these more than 50% of the p a r t i c l e s are c lay s ize (<2y) . These f ine sediments can be kept i n suspension for long periods by even s l i g h t cur -rents . T a i l i n g t u r b i d i t y or ig inates at the o u t f a l l pipe and spreads as a cloud i n the middle and lower water column both headward and towards the Narrows. Current patterns below the Narrows l i f t the t u r b i d i t y upwards i n the water column. U p - i n l e t 169 currents return part of the t u r b i d i t y up Rupert and move some up Holberg. On occasion where the t u r b i d i t y has been c a r r i e d up-wards into the surface l ayer , i t i s entrained by the ebb t ide out through Quatsino Narrows. The t u r b i d i t y l eve l s for given horizons i n the water column indicate c y c l i c a l d i s t r i b u t i o n which are re la ted to d e n s i t y - c o n t r o l l e d t i d a l currents . 170 CHAPTER VI CONCLUSIONS The monitoring of the marine t a i l i n g d i sposa l i n Rupert I n l e t , and re la ted studies have produced more sequential s c i e n t i -f i c data than i s ava i l ab l e for any other i n l e t (fjord) i n B r i t i s h Columbia. The knowledge acquired from th i s one project i l l u s -trates the need for prolonged i n t e r d i s c i p l i n a r y studies of various types of i n l e t s . This thes is i s concerned with the s e d i -mentation regime. I t i s l imi t ed to pre-product ion condit ions and observations on the e f fect of the f i r s t two years of t a i l i n g d i s -posa l . I t i s an inter im study. As the Mine continues and the growth of the sediment system i s observed, there w i l l be a con-t inu ing need for reassessment. The bottom current studies measuring v e l o c i t i e s about 1.5 metres o f f bottom establ i shed the repeated presence of cur -rents often i n excess of 50 cm/sec and occas iona l ly i n excess of 100 cm/sec i n the area beneath Quatsino Narrows and the lower reach of Rupert I n l e t . The data co l l ec t ed from the Quatsino Narrows to the Mine s i t e suggest that the current regime of the basin i s contro l l ed by the height , range and densi ty of the f lood t i d e . The incoming t ide seeks i t s density l e v e l and progresses up i n l e t . Water at and above the i n j e c t i o n l e v e l moves up i n l e t , while water below the i n j e c t i o n l e v e l moves down i n l e t as a counter current . The down-inlet f lood t ide currents i n Rupert 171 and Holberg i n l e t s are convergent below the Narrows. Where down-i n l e t f l o o d t i d e c u r r e n t s occur as hig h s l a c k t i d e i s approached, p r e s s u r e s are r e l e a s e d and the bottom i s swept by an u p - i n l e t c u r r e n t . U p - i n l e t v e l o c i t i e s i n g e n e r a l exceed down-inlet v e l o -c i t i e s . Maximum u p - i n l e t bottom c u r r e n t s observed are near the upper end of Rupert gap and may exceed 75 cm/sec. Maximum down-i n l e t c u r r e n t s occur near the Narrows and commonly exceed 50 cm/ sec but o c c a s i o n a l l y exceed 100 cm/sec. Maximum bottom c u r r e n t c o n d i t i o n s were not observed, but t h e o r e t i c a l l y occur when the d e n s i t y of the f l o o d t i d e exceeds the d e n s i t y of the bottom water i n the b a s i n . The r e s u l t would be an u p - i n l e t bottom c u r r e n t s t a r t i n g a t the Narrows, with a poten-t i a l v e l o c i t y o f between 100 cm/sec and 300 cm/sec (6 k n o t s ) . The most probable time f o r t h i s type of i n c u r s i o n i s i n l a t e sum-mer when s u r f a c e and upper water i n Quatsino Sound have h i g h den-s i t y , but may be induced a t other seasons by storms b r i n g i n g dense bottom water i n t o the upper water column. The bottom c u r r e n t s t u d i e s support the sedimentation regime as i n t e r p r e t e d from s e i s m i c and sediment data and c o n f i r m t h a t the prese n t bottom c u r r e n t regime has been i n e f f e c t s i n c e Quatsino Narrows has been an a c t i v e passage, f o l l o w i n g the end of g l a c i a t i o n . The t h r e e annual s e i s m i c surveys p r o v i d e v i s u a l p r e -s e n t a t i o n of the major f e a t u r e s of geology and topography. The 172 b a s i n i s a U-shaped v a l l e y with t h r e e d i v i s i o n s of sediment i n -f i l l : U n i t C, a p p a r e n t l y coarse e l a s t i c s with p o o r l y d e f i n e d bedding and not s i g n i f i c a n t to t h i s study; U n i t B, h o r i z o n t a l and a c c o u s t i c a l l y thin-bedded; and U n i t A, i r r e g u l a r l y d i s t r i -buted but a c c o u s t i c a l l y w e l l s t r a t i f i e d . S eismic r e c o r d s i n d i -c a t e e r o s i o n of U n i t B beneath Quatsino Narrows,and the l o c i of d e p o s i t i o n of U n i t A to be up both Holberg and Rupert i n l e t s . The e r o s i o n a l p a t t e r n i l l u s t r a t e s t h a t Quatsino Narrows was not connected with Quatsino Sound d u r i n g d e p o s i t i o n of U n i t B. Access o f Quatsino Sound t i d e w a t e r v i a Quatsino Narrows t o the b a s i n r e s u l t e d i n e r o s i o n of U n i t B below the Narrows by c u r -r e n t s which obey C o r e o l i s e f f e c t as they move sediments up both i n l e t s . The main d e p o s i t i o n of U n i t A i n Rupert I n l e t i s a s e t of s l o p i n g beds on the n o r t h c e n t r a l f l a n k , o f f the Mine s i t e . Minor u n c o n f o r m i t i e s i n the U n i t A s e c t i o n a t t e s t t o pas t v a r i a -t i o n s i n c u r r e n t v e l o c i t i e s . S e ismic surveys adjacent t o t a i l i n g and waste rock dumping show s l i d i n g and slumping of the t i l t e d U n i t A beds. There i s a l s o evidence t h a t these t i l t e d beds may have i n the past slumped under t h e i r own weight. A f a n forming down slope from the t a i l i n g o u t f a l l p i p e dams Rupert trough and ponds t a i l -i n g behind i t . Down i n l e t from the f a n , t a i l i n g have i n f i l l e d t o p ographic i r r e g u l a r i t i e s and developed a r e g u l a r l y graded slope which ends on the Rupert I n l e t s i d e of the o u t f a l l of Quatsino Narrows. D i r e c t l y below the Narrows and up Holberg In-l e t , the o r i g i n a l hummocky topography of eroded U n i t B p e r s i s t s , 173 although cores i n d i c a t e a mantling of t a i l i n g . The i n f e r e n c e i s t h a t the c u r r e n t s from the Narrows are managing t o c o n t a i n most o f the bottom l o a d o f the t a i l i n g i n Rupert I n l e t . Continued annual s e i s m i c surveys are e s s e n t i a l to determine the extent and amount of major d e p o s i t i o n a l s i t e s as w e l l as r e c o r d any l a r g e -s c a l e d e f ormation. The sediment s t u d i e s r e c o g n i z e U n i t A and U n i t B of the s e i s m i c study. While U n i t B i s a gray, uniform, c l a y e y s i l t , U n i t A i s dark o l i v e - g r a y w i t h v a r i a b l e g r a i n s i z e , being c o a r s -e s t below Quatsino Narrows and becoming f i n e r up i n l e t . The s i t e s of maximum d e p o s i t i o n of U n i t A, i n Holberg trough and on the north c e n t r a l f l a n k of Rupert I n l e t , are a l s o the s i t e s of f i n e s t g r a i n s i z e d e p o s i t i o n . S o r t i n g and g r a i n s i z e d i s t r i b u t i o n sug-ge s t t h a t maximum bottom c u r r e n t s are st r o n g e r up Rupert I n l e t than Holberg I n l e t . T a i l i n g d e p o s i t i o n confirms the sedimentation regime observed i n the n a t u r a l sediment i n t h a t i t i s being l a r g e l y l i m i t e d t o Rupert I n l e t . Maximum winnowing of the t a i l i n g by bot-tom c u r r e n t occurs i n Rupert gap w h i l e c u r r e n t s s t a r t i n g a t Quatsino Narrows w i l l c o ntinue t o erode t a i l i n g from below the Narrows. An estimated 7.5% of the t a i l i n g have been moved up Holberg I n l e t . These t a i l i n g are b e l i e v e d l a r g e l y the r e s u l t of tu r b u l e n c e below the Narrows r a i s i n g t a i l i n g h i g h e r i n the water column f o r t r a n s p o r t up i n l e t by c u r r e n t s . T u r b i d i t y caused by very f i n e t a i l i n g i s common through much of the water column and 174 throughout the b a s i n t o beyond the S t r a g g l i n g I s l a n d s . The sediment study confirms the i n i t i a l c o n t e n t i o n t h a t s t r o n g u p - i n l e t bottom c u r r e n t s cause the major area of d e p o s i t i o n on the nort h f l a n k of Rupert I n l e t near the Mine. Because the t a i l i n g are p l a c e d i n t h i s d e p o s i t i o n a l c e n t r e but do not remain, the method of d i s p o s a l i s i n p a r t d e f e a t i n g the n a t u r a l c o n d i -t i o n s , which f a v o r t h i s area as the main d e p o s i t i o n a l s i t e i n Rupert I n l e t . The c u r r e n t s t u d i e s suggest t h a t the bottom c u r -r e n t s i n the upper end of Rupert gap are dominantly up i n l e t . The o b j e c t i v e of the dumping would seem to be de f e a t e d by two f a c t o r s : 1) too much f i n e t a i l i n g (slimes) are being allowed to enter the water column a t i n t e r m e d i a t e l e v e l s and 2) p o s s i b l y too much of the bottom l o a d i s being allowed to progress down i n l e t probably by o v e r l o a d i n g the c u r r e n t c a p a c i t y to overcome the down-inlet g r a v i t a t i o n a l e f f e c t . Both of these c o n d i t i o n s allow m a t e r i a l t o enter the main area of tu r b u l e n c e below the Narrows, become d i s p e r s e d i n the water column and r e d i s t r i b u t e d throughout the Holberg-Rupert b a s i n . Present e v a l u a t i o n of the combined t a i l i n g and waste rock d i s p o s a l system suggests t h a t most of the mine d e t r i t u s w i l l remain i n Rupert I n l e t , but as the p r e s e n t sedimentation regime becomes overloaded, an i n c r e a s -i n g percentage of t a i l i n g w i l l extend to below Quatsino Narrows r e s u l t i n g i n a d d i t i o n a l t u r b i d i t y and percentage of t a i l i n g r e a c h i n g the Holberg sedimentation regime. Increased t u r b i d i t y w i l l a l s o r e s u l t i n a d d i t i o n a l s u r f a c e t u r b i d i t y being drawn out through the Narrows. A f t e r mine a c t i v i t y ceases, bottom c u r -175 r e n t s w i l l continue to attempt t o excavate the area beneath the Narrows t o i t s p r e s e n t depth. The p r e p a r a t i o n of t a i l i n g t o ensure maximum enhance-ment of sedimentation should be re-examined. The depth and p l a c e -ment of the o u t f a l l p i p e , and the p o s s i b l e use of more than one o u t f a l l p i p e , r e q u i r e s e n g i n e e r i n g c o n s i d e r a t i o n . There i s a danger of b u i l d i n g u n s t a b l e , f l u i d o v e r - p r e s s u r e d s l o p e s through r a p i d sedimentation which may r e s u l t i n massive slumping and t u r -b i d i t y c u r r e n t s . Study should be g i v e n t o v e l o c i t y of d i s c h a r g e ; to the most i d e a l p r e p a r a t o r y d i l u t i o n w i t h sea water t o enhance p a r t i c l e bonding; to the c o n t r o l of temperature as an a i d to d e n s i t y ; t o the p o s s i b i l i t y of induced super d e n s i t y w i t h chemi-c a l a d d i t i v e s to a i d bonding and compaction. F i n a l l y , c o n s i d e r a -t i o n should be g i v e n to p r i o r removal of a percentage o f the f i n e t a i l i n g (slime) to c o n f i n e t u r b i d i t y w i t h i n t o l e r a b l e limits,.;. The p r e s e n t d i s p o s a l of waste rock works a g a i n s t the system by adding t u r b i d i t y t o the upper l e v e l of the water column and c a u s i n g massive d i s t u r b a n c e of the s l o p e as w e l l as the t a i l -i n g pond d e v e l o p i n g behind the t a i l i n g f a n . The waste rock, which should be d i s p o s e d of i n a manner not to t h r e a t e n the t a i l -i n g fan impondment, might be.used t o e i t h e r improve the impondment or c r e a t e a secondary l i n e of impondment down sl o p e from the t a i l -i n g f a n , perhaps a t the upper end of Rupert gap. The danger of such a dam c r e a t i n g an u n d e s i r a b l e b a f f l i n g e f f e c t on bottom c u r r e n t s and thereby producing t u r b i d i t y , needs p r i o r i n v e s t i g a -176 t i o n . More current data for middle and upper Rupert In le t are required to advance th i s suggestion. The monitoring program at Rupert In le t should serve as a model, with modi f icat ion and extension, for i n t e r d i s c i p l i n a r y inves t igat ions i n preparat ion for orderly"mult i -purpose u t i l i z a -t i o n of i n l e t waters. BIBLIOGRAPHY American Geologica l I n s t i t u t e , 1967. Invest igat ing the E a r t h . Houghton M i f f l i n Company, Boston. 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