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The use of air bubblers to prevent shoaling at wharves in navigable rivers Ages, Alard Berend 1967

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THE USE OF AIR BUBBLERS TO PREVENT SHOALING AT WHARVES IN NAVIGABLE RIVERS by ALARD BEREND AGES B.A.Sc, The University of B r i t i s h Columbia, Vancouver, B.C., Canada: 1960 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of C i v i l Engineering We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1967 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia,, I agree that the 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 agree that per m i s s i o n f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the.Head of 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 understood that copying or p u b l i  c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission.. Department of CL?M { ( {£^,'.... ee v - C The U n i v e r s i t y of B r i t i s h Columbia,, Vancouver 8 5 Canada Date -Apr-) 1^, \<j(>l Errata and Addendum, M.A.Sc. Thesis, A.B. Ages Page Line i i 18 X 7 7 8 20 34 38 45 48 57 58 67 67 102 2 19 19 7 5 18 12 7 12 8 12 16 7 Words slopes Groxier In Tuktoyaktuk, NWT pneumatic b a r r i e r recent development fact 0.20 l b / f t 2 Change to: slope Grozier (20,21) i n CYAQ /2pAp concerned mainly on re j cted wharf; replacing Mr. Schtnitt and Professor E. S. Pretious form 8 = 00 (15 feet deep) (13) (13) 104 18 shoaling, 104 21 i n future 104 22 freshest 105 11 enclosed 107 10 hose, which i s 107 12 air-bubbler 108 23 bubbbler 108 24 30 feet of water In Tuktoyaktuk, NWT (22) pneumatic b a r r i e r (23) recent development factor 0.020 l b / f t 2 £ - CYA /2pAp o concerned mainly with rejected wharf, replacing Professor E.S. Pretious and Mr. Schmitt from 8 + 00 (8-1/2 feet deep, 20 feet wide and 150 feet long) shoaling i n future, freshets encloses hose i s air-bubbler hose bubbler 34 feet of fresh water Cont'd . 2 Errata and Addendum. M.A.Sc. Thesis, A.B. Ages. (Continued) Page Line Words Change to: 110 23 effect affect 112 #4 Preszluft."Olsperren Pressluft Olsperren" 112 #13 W. Schmitt and E. S. Pretious, 1966 E. S. Pretious 1967 113 l i n e 8 Addendum #20 Simon Ince, "Winter Regime of a Tid a l Inlet i n the A r c t i c and the Use of A i r Bubbles for the Protection of Wharf Structures"; Proceedings of 8th Conference, Coastal Engineering, November 1962. #21 Baines, W. D., "The Princ i p l e s of Operation of Bubbling Systems"; Proc. of the Symposium of A i r Bubbling; N.R.C., 1961. #22 Ian Larsen, "Pneumatic Barrier Against Salt Water Intrusion", Journal of Waterways & Harbour Div.;Proc. of ASCE, September 1960. #23 G. Abraham & P.V.D. Burgh, "Pneumatic Reduction of Salt Intrusion thrcughLocks", Journal of the Hydraulics D i v i s i o n , Proceedings, ASCE, January 1964. i i ABSTRACT The Fraser-Surrey Wharf, situated on the l e f t bank of the Main Arm of the Fraser River just downstream of New Westminster, B.C., has been subject to severe shoaling during annual freshets, ever since i t s construction i n 1926. This has seriously hampered shipping and caused a loss i n revenue. In the summer of 1965, Professor E. S. Pretious of the C i v i l Engineering Department, the University of B r i t i s h Columbia, was approached by the Fraser River Harbour Commissioners (owners of the wharf) to investigate the f e a s i b i l i t y of employing air-bubblers to prevent shoaling i n the approaches to the wharf. The project study was chosen as a thesis topic by the author, under the supervision of Professor Pretious. The research which was subsequently undertaken involved the theory underlying the interaction between air-bubbles and water; labora tory experiments to measure upward water v e l o c i t i e s induced by r i s i n g air-bubbles; s e t t l i n g v e l o c i t i e s of the bed-sand found i n front of the wharf, and the c r i t i c a l t r a c t i v e shear stresses for impending motion of the bed material. In the f i e l d , the hydraulic slopes of the water surface at the wharf was measured to determine i f the conditions for bed-load movement existed; r i v e r current v e l o c i t i e s were measured (surface and sub-surface); weekly, con t r o l l e d , sounding surveys were carried out i n addition to a number of sediment sampling surveys and f l o a t studies, to determine flow patterns. Bubbler hoses were designed and prepared i n the Hydraulics Laboratory of the University of B r i t i s h Columbia and i i i ABSTRACT (Continued) subsequently Installed at the wharf. They were kept operating throughout the major part of the 1966 freshet (May, June, J u l y ) . Recommendations for improved designs and further research are also made. i v TABLE OF CONTENTS SECTION PAGE Introduction 1 I Review of P r a c t i c a l Applications of Air-bubblers under Water 6 I I Theory 13 I I I Laboratory Tests 28 IV F i e l d Investigations 56 V Discussion of Results 99 VI Conclusion 106 Bibliography 112 APPENDIX I I Average Bubble Vel o c i t i e s I I I S e t t l i n g Velocities of Fraser River Sand IV O r i f i c e Meter i n A i r Supply V Upward Water Vel o c i t i e s Induced by Bubbles VI K i n Taylor's Analogy VII F i e l d Calculation of Tidal Effect on Hydr. Slope Measurements at Wharf. VIII Graph of Slope Measurements at Wharf. IX Chart for determining Largest Grain Sizes to reach Deposit Area. X Pressure Drop i n Unperforated and Perforat Hose. XI Soundings at Fraser-Surrey Wharf. TABLE OF CONTENTS (Continued) APPENDIX (Cont'd) XII Soundings at Fraser-Surrey Wharf. XIII Longitudinal P r o f i l e s of River Bottom at Fraser-Surrey Wharf, freshet 1966. XIV Longitudinal P r o f i l e s of River Bottom at Fraser-Surrey Wharf, post-freshet, 1956-1965. XV Equipment and Material. v i LIST OF FIGURES NUMBER 1 Lower Fraser River 2 Cir c u l a t i o n i n Bubble vs. Drag. 3 Drag Coefficient versus Reynolds' Number. 4 Bubble Velocity Versus Diameter. 5 Calibration of O r i f i c e Meter (Water). 6 Calibration of O r i f i c e Meter (Water). 7 Water-Surface Slope Measurements i n Laboratory. 8 S e t t l i n g Rate of Sand P a r t i c l e s i n Water. 9 Sketch of Puri Siltometer. 10 Calibration of O r i f i c e Meter ( A i r ) . 11 Coefficient C. 12 Upward Water Vel o c i t i e s Induced by Air-Bubbles. 13 Upward Water Vel o c i t i e s Induced by Air-Bubbles. 14 Upward Water Vel o c i t i e s Induced by Air-Bubbles. 15 Upward Water Velocities Induced by Air-Bubbles. 16 F i e l d Operations at Fraser-Surrey Wharf. 17 Water-Surface Slope Measurements at Wharf. 18 Surface Currents, Fraser-Surrey Wharf. 19 Surface Currents, Fraser-Surrey Wharf, v i i LIST OF FIGURES (Continued) NUMBER 20 Sub-Surface Current V e l o c i t i e s , Fraser- Surrey Wharf. 21 Sub-Surface Current V e l o c i t i e s , Fraser- Surrey Wharf, 22 Sub-Surface Current V e l o c i t i e s , Fraser- Surrey Wharf. 23 Sub-Surface Current V e l o c i t i e s , Fraser- Surrey Wharf. 24 Sub-Surface Current V e l o c i t i e s , Fraser- Surrey Wharf. 25 Fraser River at Hope and Mission, B.C. 26 Tide Comparison Point Atkinson-New Westminster. 27 Dis t r i b u t i o n Curve of Suspended Sediment. Pt. Mann. 28 Dis t r i b u t i o n Curve of Suspended Sediment. Pt. Mann. 29 Distr i b u t i o n Curve of Suspended Sediment, Pt. Mann. 30 Distr i b u t i o n Curve of Suspended Sediment, Pt. Mann. 31 Distr i b u t i o n Curve of Bed Material, Pt. Mann. 32 Dis t r i b u t i o n Curve of Bed Load, Pt. Mann. 33 Distr i b u t i o n Curve of Bed Material, Fraser-Surrey. 34 Deep Sea Vessels at Fraser-Surrey Wharf. v i i i LIST OF PLATES PLATE NO. 1 New Westminster T r i f u r c a t i o n Area. 2 Laboratory Investigations. 3 Miniflow Meter. 4 I n s t a l l a t i o n of Air-Bubbler. 5 Fraser-Surrey Wharf. 6 Sounding at Fraser-Surrey Wharf. 7 Sampling of Suspended Sediment. ACKNOWLEDGEMENTS i x The author i s greatly indebted to his thesis supervisor, Professor E. S. Pretious, P.Eng., of the Department of C i v i l Engineering, the University of B r i t i s h Columbia, and formerly Director of the Fraser River Model Project (1948-1962 i n c l . ) , for his constant encouragement and guidance and his t i r e l e s s , active p a r t i c i p a t i o n i n a l l aspects of this project. The project could not have been carried out without the unf a i l i n g support and cooperation of certain Federal Government agencies, i n p a r t i c u l a r the Water Resources Branch of the Department of Energy, Mines and Resources, who provided a suspended-sediment sampler and a current meter together with operators. They also made th e i r sedimentation laboratory f a c i l i t i e s available for analyzing the sediment samples. The cooperation of Mr. T.F. Smith of this Department, who coordinated the f i e l d work and organized the compila t i o n of survey information, as well as the assistance and advice given by Mr. R. Keene and his s t a f f i n the New Westminster sedimenta tion laboratory, are gratefully acknowledged. The lo c a l D i s t r i c t Office of the Federal Department of Public Works generously provided vessels and personnel to carry out regular hydrographic surveys of the project area and to i n s t a l l and remove the air-bubbler. Thanks are due to Mr. R. Wallace, P.Eng., of this Department for his co operation i n planning the sounding surveys and to Messrs, Faulkner and Gilmour, the Officers i n Charge of the M.V. "Sounder", and th e i r crews, ACKNOWLEDGEMENTS (Continued) The author wishes to express his gratitude to Captain Ho R. Johansen, of the Fraser River Harbour Commission, Harbour Master for New Westminster Harbour, who o r i g i n a l l y suggested the p o s s i b i l i t y of applying an air-bubbler to the a l l e v i a t i o n of shoaling at the wharf. His continuous and enthusiastic support of the f i e l d work, together with the cooperation of Captain Tom Groxier of the M.V. "Port Fraser", were indispensable to the operation of the air-bubblers, the sediment sampling and other integrated operations. The experimental work described i n this thesis was carried out i n the Hydraulics Laboratory of the University of B r i t i s h Columbia. The use of these f a c i l i t i e s i s gratefully acknowledged, and thanks are due to Messrs. H.W. Schmitt and E, M. White of the instrument shop, Department of C i v i l Engineer ing, U.B.C., for t h e i r valuable suggestions and help i n carrying out phases of the laboratory experiments and f i e l d tests. The National Research Council of Canada generously supported the project with a research grant and the Fraser River Harbour Commission undertook a l l expenditures i n connection with the rental of the a i r compressors besides providing free use of wharf f a c i l i t i e s . A p r i l , 1967. Vancouver, B r i t i s h Columbia. 1 INTRODUCTION The Fraser-Surrey Wharf, previously known as P a c i f i c Elevators Wharf, was b u i l t i n 1928 together with a grain elevator, s i l o s and a large unprotected storage space. Situated i n the municipality of Surrey, about one and one half miles downstream from New Westminster, B.C., on the l e f t bank of the Main Arm of the Fraser River, the wharf i s rather isolated from the main port f a c i l i t i e s of New Westminster Harbour. However, being the only grain elevator wharf i n the harbour area, and ea s i l y accessible to large cargo ships, i t has grown i n importance, p a r t i c u l a r l y during the present boom i n the export of grain and lumber. Although New Westminster i s the only fresh- water port of Western Canada, having certain t r a n s i t advantages over the salt-water ports of Vancouver and Prince Rupert, i t s t i l l has to struggle with a problem much less v i t a l to Vancouver and of no concern whatsoever to the almost perfect natural harbour of Prince Rupert. The harbour of New Westminster, including the Fraser-Surrey Wharf, i s subject to heavy s i l t a t i o n during freshet periods occurring annually between May and July. The Fraser River at New Westminster tr i f u r c a t e s into the North Arm, Annacis Channel and Annieville Channel (vid. Plate 1), with a consequent decrease i n flow and increase i n sedimentation i n Annieville Channel, the navigation channel for deep- sea vessels. The major portion of New Westminster's harbour f a c i l i t i e s i s located at the junction of this t r i f u r c a t i o n and i s 2 therefore vulnerable to shoaling. The Department of Public Works, Canada, c a r r i e s out an annual dredging program between the Port of New Westminster and the mouth of the Fraser River, about 21 miles downstream of the Port. This program includes A n n i e v i l l e Channel and the approaches to the Fraser-Surrey Wharf, As Plate 1 shows, the wharf being located on the l e f t bank of the River on the s l i g h t l y convex side of the bend, the r i v e r ' s cross-section there would n a t u r a l l y tend to be shallow. Although the wharf would normally have created a l o c a l c o n s t r i c t i o n i n the width of the channel and might thus have improved l o c a l depths, i t was b u i l t s l i g h t l y downstream of an e x i s t i n g groin and thus did not contribute appreciably to any b e n e f i c i a l changes i n the r i v e r bed. The natural depths of 16 to 22 feet below l o c a l low water i n the immediate approaches to the wharf, were inadequate for the r a p i d l y increasing draughts of modern shipping and since neither the presence of the elevator wharf, nor a t r a i n i n g w a l l between the groin and the wharf appeared to improve the depths, annual dredging was i n e v i t a b l e ever since the wharf was put into s e r v i c e . To maintain a required depth of 27 feet below l o c a l low water during the period 1928-1933, an annual average of 84,000 cubic yards of sand had to be dredged from the approaches to the w h a r f F r o m 1934 to 1948, a depth of 27 to 30 feet was main tained by an average annual dredging of 44,000 cubic yards. A f t e r the abnormally high 1948 freshet, 343,000 cubic yards were dredged 3 from the same area, followed by only 91,000 cubic yards i n 1949 and an annual average of about 177,000 cubic yards between 1949 and 1954. In 1954, an increase i n shoal of about three feet i n front of the elevator was caused by excavating the r i v e r bed on the west side of the regular, navigation dredge cut i n A n n i e v i l l e Channel, to provide f i l l f o r Annacis Island,, This resulted i n a stronger flow along the r i g h t side of the r i v e r and a weaker flow along the l e f t side (approaches to the elevator wharf), increasing the shoaling tendency there The gradual increase i n draughts of cargo vessels necessitated a dredged depth of 30 feet below l o c a l low water, which involved a general increase i n dredging quantities to 300,000 cubic yards annually, from 1954 to the present year» Sounding charts and shipping records i n d i c a t e that the wharf has remained open to deep-sea ships annually from September to May without the help of dredgingo Unfortunately, attempts to extend this period by dredging during the freshet periods were f r u s t r a t e d by the swollen sediment-laden r i v e r , causing the excavated area to f i l l i n almost immediately a f t e r the dredge had moved away. Furthermore, dredging operations were made hazardous by the strong r i v e r currents, the dredge having to avoid the close proximity of the wharf for fear of damaging her equipment. Last but not l e a s t , a dredge would be i n the way of shipping. These l i m i t a t i o n s i n the use of a conventional dredge c l e a r l y c a l l e d f or other methods to provide the Port of New Westminster with a wharf which could handle grain ships throughout the year. ' Apart from remedial works i n the form of r i v e r - t r a i n i n g structures which had been designed and tested i n the Fraser River Model at the University of B r i t i s h Columbia, the i n s t a l l a t i o n of an air-bubbler on the r i v e r bottom i n front of the Grain-Elevator Wharf was suggested as a possible shoal i n h i b i t e r . In comparison with a dredge, the air-bubbler would e n l i s t , rather than avoid, the strong r i v e r currents and would operate at maximum e f f i c i e n c y during freshet periods. Furthermore, i t would not get i n the way of shipping. In p r i n c i p l e , the method of using an air-bubbler to prevent sedimentation can be explained as follows: The v e r t i c a l , v e l o c i t y p r o f i l e of r i v e r flow generally shows a d i s t r i b u t i o n of v e l o c i t i e s increasing from zero near the r i v e r bed to a maximum at a depth approximately equal to 0.2 of the t o t a l depth, A screen of r i s i n g air-bubbles induces a v e r t i c a l upward flow of water i n the immediate v i c i n i t y of the r i s i n g bubbles. I f this upward flow i s strong enough to overcome the downward s e t t l i n g motion of the suspended sediment or bed load, then the sediment, while t r a v e l l i n g downstream, would be forced up into the flow layers of higher v e l o c i t i e s . Sediment, which would normally s e t t l e i n front of the wharf, would thus be car r i e d further downstream, provided that: a) the upward flow, l o c a l l y induced i n the r i v e r by the bubble screen, i s capable of l i f t i n g the sediment, and b) the ho r i z o n t a l r i v e r flow along the wharf i s su f f i c i e n t l y , strong to transport the sediment past the wharf, once 5 i t has been l i f t e d to a higher l e v e l i n the flow. I t i s clear that a strong, upward, water-flow induced by air-bubbles i s a necessary, but not s u f f i c i e n t condition for prevention of shoaling. Without a s u f f i c i e n t l y strong h o r i z o n t a l flow to carry the sediment away, the bubbler would be i n e f f e c t u a l . Therefore, to investigate the p o s s i b i l i t i e s of an a i r - bubbler to prevent shoaling at the Fraser-Surrey Wharf, laboratory research had to be combined with a study and analysis of the f i e l d conditions. 6 SECTION I Review of P r a c t i c a l Applications of Air-Bubblers under Water The use of compressed a i r to create a screen of r i s i n g air-bubbles i n water and thus induce a c i r c u l a t i o n i n the water, has been recognized by engineers since the turn of this century and, p a r t i c u l a r l y i n the la s t ten years, many research projects have been undertaken to investigate applications of this basic concepto Probably the best known application of the property of r i s i n g air-bubbles to create a convection current i n the surrounding water i s the de-icer, a perforated pipe ly i n g on the bottom of a lake or r i v e r and releasing compressed a i r . The r i s i n g air-bubbles entrain the r e l a t i v e l y warm water at the, bottom, carrying i t upward to the frozen surface thereby melting the i c e . This method originated i n Sweden i n 1953, where a great many ferry routes are now kept open during the. winter. In.Canada, de-icers have been i n s t a l l e d at Prescott, Ontario, to keep the ferry s l i p open; i n Manitoba, to prevent ice formation at the Slave F a l l s Dam; i n B r i t i s h Columbia to keep a log pond near Castlegar operating during the winter; and i n Quebec, where a lake near Kilmar i s made ice-free by a bubbler, which also, maintains the oxygen content of the lake, thus producing a healthier environment for the f i s h population. In this connection, mention should be made of the air-bubbler at Lake LakeIse i n B r i t i s h Columbia, where r i c h , nutrient-laden bottom 7 water was forced to the surface where the f i s h reside. In Tuktoyaktuk, N.W.T., near the mouth of the Mackenzie River, the wharf of the Northern Transportation Company, which i s a v i t a l l i n k i n the supply route along the DEW l i n e , suffered heavy damage when the ice sheet i n the bay moved up and down with a two-feet tide and dislocated the p i l e s . An air-bubbler was i n s t a l l e d underneath the wharf and the continuous flow of a i r - bubbles kept the ice away from the p i l e s , saving the wharf. How ever, this method i s only possible when the bottom water i s warmer than the surface layers, which i s the case i n Tuktoyaktuk Bay with i t s brackish water ( s a l i n i t y 0.5% at 32°F). The same bubbler was ineffec t u a l under the wharf at Cambridge Bay, 700 miles east of Tuk, where the s a l i n i t y (2,9% at 29°F) i s much higher and the water temperature consequently close to freezing a l l the way from the surface to the bottom. A de-icer therefore makes use of the property of a stream of air-bubbles to induce a convection current i n the surrounding water, which carries r e l a t i v e l y warm water to the frozen surface. A s i m i l a r application i s the pneumatic b a r r i e r . In many rivers and t i d a l estuaries, salt-water intrusion from the sea threatens the fresh-water intakes of f a c t o r i e s , industries and c i t i e s and the f e r t i l i t y of the surrounding land. The s a l t water moves upstream under the out-flowing fresh water i n the form of a wedge. I f the fresh-water outflow i s much greater than the t i d a l inflow, a bubble ba r r i e r across the r i v e r would force the s a l t water upwards where 8 the r i v e r flow can carry i t seaward. Salt water intrusion i s a p a r t i c u l a r l y aggravating problem on the East Coast of the United States, where i n the near future the water supplies of New York and Philadelphia may have to depend partly on fresh r i v e r water. The Hudson and Delaware rivers have mixed estuaries; the t i d a l flow there i s much larger than the r i v e r - flow, resulting i n a mixing of s a l t and fresh water during incoming tide and consequently a small, v e r t i c a l salinity-gradient. A l  though an air-bubbler obviously would work better i n a large, v e r t i c a l s a l i n i t y - g r a d i e n t , experiments carried out i n 1965 i n the Hudson River with a number of bubblers showed a s a l t water reduction of 70% at a point 30 miles upstream from Manhattan. Encouraging tests with pneumatic barriers to reduce s a l t water intrusion have y (2) also been conducted i n the harbour of New Castle, A u s t r a l i a (3) Recent reports from Holland describe how the s a l i n i t y of deep saltwater pockets i n the Schelde estuary i s being reduced success f u l l y by air-bubblers, after this estuary was closed off from the sea by the "Delta" dams. Another recent development i n Holland as well as i n England i s the pneumatic b a r r i e r to prevent s i l t - l a d e n bottom water from penetrating r i v e r locks when the gates are opened to admit ships. The operation of both the de-icer and the pneumatic barr i e r make use of the convection current i n water, created by air-bubbles. The r i s i n g water current spreads out into a strong horizontal current 9 which has inspired the design of another device, the pneumatic breakwater. The idea that o s c i l l a t o r y , progressive surface- waves could be attenuated by a curtain of air-bubbles was put forward i n 1902. by the American C i v i l Engineer. P. Brasher. The p r i n c i p l e underlying the mechanism i n the behaviour of this pneumatic breakwater has been a subject of s c i e n t i f i c controversy for many years. Or i g i n a l l y i t was thought that the introduction of big air-bubbles would disturb the harmonic p a r t i c l e motion of the surface waves and reduce t h e i r amplitude. An a r t i c l e i n "Compressed A i r " (November 1959) by G. R. Smith mentioned a reduction i n amplitude of 50%. The energy of a progressive wave system of amplitude "a" can be represented by E • *s Y a 2 where y i s the s p e c i f i c weight of water i n l b s / f t 3 , and a, the amplitude i n feet, by d e f i n i t i o n - \ wave height (H); therefore E - y H 2 i n f t . l b s . per square foot of water surface, i . e . f t . l b s . per foot of wave length per foot of crest length. A reduction of amplitude by 50% would reduce the energy of the waves by 75%. Although this approach did not seem to be contradicted by research, i t was perhaps misleading i n that i t implied that the bubbles were d i r e c t l y responsible for the wave-attenuating e f f e c t . Investigations carried out over the past t h i r t y years ( J . Thijsse, D e l f t , 1936; T. Evans, Southall, 1955, et al.) showed that waves up to a certain wave length could be attenuated by an opposing surface current, set up by the bubbles, but that the bubbles themselves did not have as much effect on the waves as implied by the f i r s t theory. I t can be shown 10 a n a l y t i c a l l y (Appendix I) that waves are shortened by an opposing surface current and that, i n the process of becoming shorter, they become higher u n t i l they become too steep for s t a b i l i t y and break before reaching the protected area. The foregoing Idea was put Into practice at Dover Harbour, England, In 1957. A battery of jug-shaped polyethylene units was anchored on the sea f l o o r between the two j e t t i e s forming the harbour entrance. The units received t h e i r a i r from shore-based compressors and belched out large air-bubbles with a frequency which eeuld be regulated aeeerding t§ the s i s a ©f the waves a Act u a l l y , the surface currents created by the air-bubble§ eeuld also be created by water j e t s , emerging frem noggles i n c l i n e d upwards cl§se te the water surface. A battery ©f negales weuld be impracticable i n a harbeur entrance but might have i t s merits i n protecting a beach er an exposed eenstruetien s i t e , provided that such a water-jet breakwater i s mere economical than a pneumatic breakwaters Another device which makes use of horizontal surface currents created i n the water, but which cannot be produced by water- je t s for p r a c t i c a l reasons, i s the pneumatic o i l b a r r i e r . I t was extensively tested i n Hamburg In 1957. The p o s s i b i l i t y of o i l spread ing out over the water surface i n a harbour aft e r a c o l l i s i o n of ships has always been of major concern to harbour a u t h o r i t i e s , not only because of dangerous f i r e hazards but also because of the inevitable damage done to marine l i f e and public property by o i l p o l l u t i o n . Obviously, i t i s e s s e n t i a l to confine the spreading o i l to a small 11 area. Barriers made of log booms or other f l o a t i n g objects have proven unsatisfactory, because they can get i n the way of shipping. Moreover, with a surface current of more than 0.3 feet per second, the o i l tends to pass underneath the fl o a t i n g b a r r i e r s , even when they consist of pontoons with a draught of two feet. (4) A pneumatic o i l b a r r i e r consists of a perforated pipe lying on the harbour bottom and connected to an a i r compressor ashore or on a barge. The ascending air-bubbles decrease the s p e c i f i c weight of the water column d i r e c t l y above the bubbler with respect to the surrounding water, which together with the ve l o c i t y head of the v e r t i c a l l y induced current i n the water create a l o c a l r i s e or hump i n the water surface. This hump must be high enough to generate a horizontal current with a velocity at least as great as that with which the o i l spreads out. The o i l ' s v e l o c i t y i n turn depends mostly on the s p e c i f i c weight of the o i l and very l i t t l e on i t s v i s c o s i t y . This type of ba r r i e r can be quickly i n s t a l l e d by a boat, equipped with a number of weighted perforated hoses and an a i r compressor. The boat would lay the pipe i n a c i r c l e around the o i l patch, thus con f i n i n g i t . The ba r r i e r could l e t ships through and immediately close again after the ship had passed. O i l would be prevented from passing underneath, such as was the case with the conventional f l o a t i n g b a r r i e r s . However, the b a r r i e r i s useless i n a mass move ment of water with a velocity of at least 0.7 feet per second. The bubble-screen i s then dispersed so e f f e c t i v e l y that the hump i n the water surface disappears and i s therefore unable to maintain a 12 s u f f i c i e n t l y large horizontal flow to confine the o i l . Another p r a c t i c a l application of air-bubblers which seems to depend more d i r e c t l y on the screen of r i s i n g air-bubbles i n water, rather than the water currents induced by the bubbles, i s the use of a bubble-screen i n under-water demolition. The screen of air-bubbles damps the shock waves created by the exploding charge. In summary, p r a c t i c a l air-bubbler applications can be c l a s s i f i e d into three main categories: I. Bubblers for creating a l o c a l v e r t i c a l water current induced by the screen of r i s i n g air-bubbles: a) De-icing i n rivers and harbours. b) Reduction of s a l t water intrusion i n estuaries. c) Providing surface f i s h with bottom nutrients i n lakes. d) Preventing s i l t intrusion into r i v e r locks. I I . Bubblers for creating horizontal surface currents generated by the r i s i n g a i r bubbles: a) Pneumatic breakwaters for harbours. b) Pneumatic o i l barriers for harbours. I I I . Bubblers to produce a screen of air-bubbles without regard to the currents induced i n the surrounding water: a) Underwater demolition around Marine I n s t a l l a t i o n s . A bubbler to prevent r i v e r sedimentation would cle a r l y belong i n the f i r s t category. 13 SECTION I I THEORY I I - l The Behaviour of Air-Bubbles i n Water i Before attempting to develop an air-bubbler which would induce a s u f f i c i e n t l y high, upward ve l o c i t y i n the water, able to l i f t suspended sediment and bed-load to the required l e v e l (region of higher v e l o c i t i e s ) i n the riverflow, the mechanics of the motion of air-bubbles and thei r interaction with the surrounding water must be examined f i r s t i n d e t a i l . The following remarks are based on previous research by others. These have been confirmed by the author's observations, wherever possible i n the time available for this project. In s t i l l water, the r i s i n g air-bubbles from a point source of a i r ( o r i f i c e ) form a cone, which subtends an angle of from zero to twelve degrees, depending on the a i r pressure inside the bubbler. The a i r emerges from the o r i f i c e with a much higher velocity than the subsequent upward ve l o c i t y of the bubbles, the air-bubbles spreading out immediately after leaving the o r i f i c e . As the bubbles r i s e , they maintain a very s l i g h t l a t e r a l motion under the influence of the water c i r c u l a t i o n induced by the bubble screen (the upward water motion diverges from the v e r t i c a l above the o r i f i c e before i t changes into a strong horizontal motion near the surface). I f the a i r pressure inside the bubbler does not exceed the hydrostatic pressure appreciably, the bubbles w i l l r i s e i n a straight l i n e . By varying the o r i f i c e diameter, the head of water above 14 the o r i f i c e , and i n p a r t i c u l a r the flow of a i r through the o r i f i c e , one can create a great many sizes and shapes of air-bubbles, which, a f t e r c l o s e r examination, may be reduced to three basic types: Spherical bubbles, oblate spheroids and s p h e r i c a l caps or mushrooms. The shape depends lar g e l y on t h e i r s i z e ; i n ordinary tap water, small bubbles up to a diameter of about 1.0 mm appear to be s p h e r i c a l . The oblate spheriod i s predominant among bubbles with an equivalent radius between 1.0 mm and 10„0 mm (equivalent radius to be defined as the radius of a sphere with a volume equal to that of the bubble). The large bubbles (over 10.0 mm) take on the shape of a mushroom with a hemispherical top. A number of investigators have rel a t e d the shape of bubbles to t h e i r s i z e as w e l l as to the v i s c o s i t y of the surrounding l i q u i d . In t h i s case, the bubble shape can be categorized according to the magnitude of the Reynolds Number 2 r UP (R) = - ( r g = equivalent radius, U = mean, upward bubble v e l o c i t y , p = l i q u i d density, p ° l i q u i d dynamic v i s c o s i t y - a l l i n consistent u n i t s ) : Spherical Bubbles, R < 400 ( 5 , 6 ) Oblate Spheroids, 400 < R < 5000 Spherical Caps, R > 5000 Although i t i s d i f f i c u l t (and for our project not essential) to ascribe a p a r t i c u l a r path to each type of bubble, the small sp h e r i c a l bubbles seem to go s t r a i g h t up, while the oblate spheroids and sph e r i c a l caps follow an i r r e g u l a r sinuous path, quite resembling a h e l i x . The very large bubbles (spherical caps) rock to and fro 15 as they ascend, Haberman and M o r t o n ^ , using motion p i c t u r e s , experimented extensively on the motions of bubbles i n d i f f e r e n t l i q u i d s and re l a t e d the motion to the p r e v a i l i n g Reynolds Number: they found a r e c t i l i n e a r motion below R = 300, s p i r a l i n g between R = 300 and R = 3000, and r e c t i l i n e a r motion with rocking, above R = 3000o Surface tension i s la r g e l y responsible f or the spher i c a l shape of small bubbles, where the hydrodynamic forces are s t i l l r e l a t i v e l y small, (Hydrodynamic forces are forces due to the acceleration of the air-bubbles, i n p a r t i c u l a r , the shear forces acting t a n g e n t i a l l y along the bubble surfaces). Surface tension then would tend to minimize the surface area of the bubble and since the sphere has the minimum surface area f o r a ce r t a i n volume, the small bubbles would be expected to be s p h e r i c a l . For very low Reynolds numbers (R = 40 f o r f i l t e r e d water), i t has been shown e x p e r i m e n t a l l y ^ that the drag c o e f f i c i e n t of very small bubbles becomes equal to that of r i g i d spheres i n any l i q u i d , i n accordance with Stokes' law. Their upward v e l o c i t y then w i l l depend l a r g e l y on the v i s c o s i t y of the l i q u i d . When these small s p h e r i c a l bubbles become larger, a c i r c u l a t i o n inside the bubble develops, which decreases the t o t a l drag r e l a t i v e to that of r i g i d spheres of the same size ( F i g , 2), (8) This c i r c u l a t i o n was observed experimentally by Garner , When the r a d i i of the bubbles exceed approximately 1,0 mm, the hydro- dynamic forces become s i g n i f i c a n t ; surface tension cannot maintain 16 a spherical shape any more and the bubbles become f l a t t e r . The drag force exerted on the bubble by the l i q u i d now becomes greater than that on a sphere of equal volume. The bubbles distinguished by large spherical caps are s t r i c t l y related to hydrodynamic forces. A constant drag (6 i c o e f f i c i e n t was determined by Rosenberg , Davies and Taylor for geometrically s i m i l a r bubbles of this type. Considering this constant, empirically-found drag coefficient and the terminal v e l o c i t y of the bubble W (when a l l forces on the bubble, v i z . drag, buoyancy and gravity, are i n equilibrium), the conventional equation for the drag c o e f f i c i e n t C = ^ ( P r a f i ) c a n be transformed D plTA into an expression containing the equivalent radius: C - (2)(Buoyancy - Weight) ° pW2(Trr 2 ) ( 2 ) ( | irr e 3)(Ywater)g _ | ~ ~ Wz(rrr z) water e W^  ignoring the s p e c i f i c weight of a i r . For constant C^, the terminal velocity (W) would then be a function of /r • only. Thus, spherical- cap bubbles r i s e with a terminal v e l o c i t y which depends on th e i r s i z e , not on the physical properties of the f l u i d . I t i s interesting to note that the drag for bubbles between 0.035 cm and 0.25 cm i s larger i n normal tap water than i n f i l t e r e d or d i s t i l l e d water. Investigations by Gorodetskaya^ , S t u k e ^ ^ , Haberman and Morton, who added various surface-active substances 17 to water, confirmed that the drag coeffi c i e n t of medium sized, e l l i p s o i d a l (oblate spheroid) bubbles i n water containing surface- active materials, i s larger than that i n pure water. For the large, mushroom-type (spherical cap) bubbles, these impurities did not have any effect on the drag coefficient or their rate of r i s e . Tap water contains many minute p a r t i c l e s , which tend to adhere to the surface of a bubble and travel along with i t as i t moves upward. These minute p a r t i c l e s seem to impart a certain amount of r i g i d i t y to the bubble surface. The phenomenon whereby very small bubbles obey Stokes' law can then be explained, not only by the tendency of the surface tension to give them a spherical shape but also by the presence i n water of minute p a r t i c l e s , which s t i c k to the surfaces of the bubbles and make them behave l i k e small, r i g i d spheres. I t i s not quite clear why, i n pure water, the very tiny spherical bubbles also behave l i k e r i g i d spheres. When the spherical bubbles increase i n s i z e , the minute pa r t i c l e s are prevented from adhering to the bubble surface by the increasing shear forces. The bubble then loses i t s r i g i d i t y , and a c i r c u l a t i o n inside the bubble i s created with a consequent decrease i n drag c o e f f i c i e n t . This drag coefficient w i l l thence continue to decrease with increasing Reynolds numbers (obviously, the decrease w i l l be more rapid i n pure water than i n tap water, see figure 3) and the upward velocity w i l l increase with size (see 18 figure 4) u n t i l , at a bubble diameter of 0.7 mm, the bubble starts to f l a t t e n out with a rapid increase i n drag and decrease i n v e l o c i t y . As figure 4 shows, this maximum velocity i n the curve i s less pronounced i n tap water, where the c i r c u l a t i o n inside the bubble i s retarded by the presence of impurities on the boundary between bubble and water, resulting i n a higher drag. F i n a l l y , for bubbles larger than about 3.0 mm, i n e r t i a becomes the dominating force i n comparison to v i s c o s i t y and surface tension and the velocity curves of bubbles i n f i l t e r e d and tap water coincide. The presence of surface-active substances has no e f f e c t , because the bubbles are now unable to hold on to them due to the high shear forces. The v e l o c i t i e s of the very large spherical-cap bubbles w i l l s t i l l be a function of thei r sizes but much of the gain i n energy by an increased buoyancy w i l l be lost by the dissipation of energy i n shedding vortices by the l e n t i c u l a r and semi-spherical shaped bubbles of this category. I t i s this shedding of vortices which actually causes the s p i r a l i n g and rocking motion of the very large bubbles. The question arises why these big bubbles take on such an unfavourable shape from a hydrodynamic point of view. A rough plot of the pressure d i s t r i b u t i o n of viscous flow past a sphere indicates what would happen i f this sphere has no r i g i d boundaries: 19 There w i l l be a negative pressure perpendicular to the direction of motion and the bubble w i l l try to adjust i t s shape to this pressure d i s t r i b u t i o n , resulting i n the formation of an approximate e l l i p s o i d of revolution generated about i t s minor axis, (oblate spheroid) which i s p a r a l l e l to the direction of motion. I t should be emphasized that the velo c i t y of a single r i s i n g bubble i s considerably lower than the velocity of a bubble cluster. Over the past years, a number of investigators (Hbefer; Hensen; Haberman and Morton) have l e f t no doubt that the upward v e l o c i t i e s of the bubbles increase with decreasing v e r t i c a l spacing (11) between the bubbles; Hensen found an average upward velocity of 23 cm/sec for single bubbles with a diameter of 15 mm, as com pared with a v e l o c i t y of 35 cm/sec for a stream (cluster) of bubbles emerging from the same opening. This phenomenon might we l l be explained by the presence of a vortex street behind each bubble, which progressively "helps" the following bubbles i n t h e i r ascent. Exner, who conducted extensive tests with bubblers i n the Lake of 20 Luzern, found a maximum upward bubble v e l o c i t y of 68 cm/sec. Appl i c a t i o n of the Gas Law (PV = RT) w i l l show that the volume of a bubble r i s i n g from a depth of about 35 feet (a represent ative value for the depths found near wharves such as the Fraser- Surrey Wharf ) , w i l l become only twice i t s o r i g i n a l volume as i t reaches the surface. The radius of this presumably equivalent 1/3 sp h e r i c a l bubble would then increase by a fa c t of 2 = 1.26. As figure 4 shows, this would hardly change the upward v e l o c i t y of the bubbles, i n p a r t i c u l a r the larger ones. Therefore, the water depth has very l i t t l e e f f e c t upon the upward v e l o c i t y of the air-bubbles i n this range of depth. I t stands to reason that the s i z e of bubbles i n water, immediately a f t e r emerging from an o r i f i c e , depends on the diameter of the o r i f i c e . In u n f i l t e r e d water, where the terminal v e l o c i t y of the bubbles increases with t h e i r diameter the terminal v e l o c i t y would thus be expected to be proportional to the o r i f i c e diameter. Tests with a number of o r i f i c e diameters i n the Hydraulics Laboratory at the University of B r i t i s h Columbia confirmed this observation (Appendix I I ) . The tests were c a r r i e d out with d i f f e r e n t a i r pressures as w e l l and the re s u l t s showed that the upward terminal v e l o c i t y of the bubbles i s also a function of the a i r pressure in s i d e the bubbler. This i s conceivable since a higher pressure increases the flow of a i r d i s t r i b u t e d among the o r i f i c e s , which again implies an increase i n the number of bubbles formed per unit of time. The air-bubbles fellow each other closer for higher pressures with a consequently higher upward v e l o c i t y 21 (probably due to the vortex streets) (4) Stehr developed an empirical relationship between mean bubble v e l o c i t y , o r i f i c e diameter and re l a t i v e a i r pressure: w = 0.4 F ^ ' ^ ^ P ^ / P ) ^ * ^ , where w = mean upward velo c i t y of 2 air-bubbles i n meters per second; F^ = o r i f i c e i n mm ; ? j / ^ a = r a t i o between absolute pressure inside and outside the bubbler. Stehr showed bubble terminal v e l o c i t i e s for four different o r i f i c e diameters, each with three different values of airflow rate. Similar tests i n the Hydraulics Laboratory at the University of B r i t i s h Columbia produced results giving an equation si m i l a r to Stehr's, except for the constant and the exponent of the pressure 0.25 P i °- 4 0 r a t i o (see App.II). The test results gave W = 6.6 A ' (—) o with a different constant because of different units employed (A 2 o r i f i c e area i n inch , W » upward mean velocity of bubbles i n feet per second),. This equation did not hold at pressures P^ only j s l i g h t l y above hydrostatic pressure where the bubbles are isolated and do not follow each other closely. In the l a t t e r case the actual v e l o c i t i e s were much lower than the v e l o c i t i e s predicted by this equation. Stehr ?s equation and the author's modification of i t are s t r i c t l y empirical, based on a " b e s t - f i t " and not on any physical analysis„ The larger o r i f i c e s release a great many different sizes and shapes of bubbles, each r i s i n g with Its individual terminal v e l o c i t y , thus making i t rather d i f f i c u l t to arrive at a fixed relationship between bubble v e l o c i t y , o r i f i c e diameter and a i r pressure. Before discussing the motion induced i n the surrounding 22 water by air-bubbles, some p r a c t i c a l aspects of the behaviour of air-bubbles r i s i n g i n water are reviewed: REVIEW 1) As they move upward i n the water and increase i n s i z e , air-bubbles take on the following successive shapes: Spherical; E l l i p s o i d a l (oblate spheroid); Spherical Cap (Mush room) o The v i s c o s i t y of the f l u i d determines the sizes at which the transitions i n shape take place. 2) The upward terminal v e l o c i t y of the bubbles i s generally proportional to their s i z e , although there i s a pronounced anomaly i n f i l t e r e d water. In this case, changing the bubble size affects the rate of r i s e of small bubbles much more than that of large bubbles, 3) The rate of r i s e of indiv i d u a l bubbles, released one after another, i s smaller than the rate of r i s e of a stream or screen of bubbles of i d e n t i c a l s i z e . Therefore, the upward vel o c i t y of the bubbles i s proportional to the amount of a i r d i s  charged by an o r i f i c e i n a unit of time, and to the a i r pressure inside the bubbler. 4) The larger the o r i f i c e diameter, the larger the bubbles, with a consequent increase i n upward ve l o c i t y . Of course, the o r i f i c e diameter i s limited by the capacity of the compressor and the bubbles cannot grow I n d e f i n i t e l y , They would divide into smaller bubbles. 5) The r e l a t i v e l y shallow depths of water of about 30 to 40 feet found near a wharf, cause the air-bubbles to expand to 23 a volume twice t h e i r o r i g i n a l volume, which hardly a f f e c t s t h e i r upward v e l o c i t i e s . 6) The a i r emerging from a si n g l e o r i f i c e w i l l r i s e to the water surface i n a cone of bubbles, subtending an angle of from 0 e to 1 2 % this angle being a function of the a i r discharge, which i s dependent on the a i r pressure inside the bubbler, I1-2 The Upward Flow Induced i n the Surrounding Water by the Ris i n g Air-Bubbles The upward flow i n the water induced by the screen of r i s i n g air-bubbles i s b a s i c a l l y a r e s u l t of the conversion of p o t e n t i a l energy of the air-bubbles into k i n e t i c energy of the surrounding water. To f i n d an expression f o r the energy av a i l a b l e i n the a i r at the moment i t leaves the o r i f i c e , iso-thermal conditions may be assumed. The expansion of the air-bubble, as i t r i s e s to the surface, takes place i n an environment which i s not only a v i r t u a l l y i n f i n i t e r e s e r v o i r but also has a much greater s p e c i f i c heat than a i r ( s p e c i f i c heat of water = 1,00; of a i r = 0,24), O — As the bubble r i s e s , the work — t i r of expansion = / p(dV), where p and 7<FL V are res p e c t i v e l y the Inside pressure and volume of the bubble and and •¥"_ 6 ' are the volumes of the bubble at two ! t a r b i t r a r i l y chosen levels 1 and 2, as j i t r i s e s i n the water. The work done ^ ^ ^ i y r ^ ^ 7 7 7 7 7 : r m r ^ r r . 2 4 by the bubbles on the water, as they expand on their way from the orifice to the water surface, i.e. the total energy available in V IFg JIT the air just before leaving the orifice, E =7 8 p(dV) = K / ~ (since pV = constant, K). = K'.ln ^r-, where V • volume of bubble o when i t leaves the o r i f i c e Now, i f we express the volumes in the corresponding pressures and let =. atmospheric pressure in feet of water, Q = cubic feet of free air per second per linear foot length of bubbler, D = water depth at bubbler in feet, Y W = specific weight of water,..we have: s = A, giving: IF H. o A .. D. + H/ D +. H E = K fcn : u. A ' = .P ..V to . „ A 8 HA D + H A o*o E + H.(y Q.) in •'_''* foot pounds per second per A W A r i . A foot length of the bubbler. From this equation, i t can readily be deduced that the energy available in a bubbler will increase with.a) the flow of air emerging from a unit length.of bubbler; b) the depth of submergence of the bubbler. A short calculation will show that a bubble of free air (i.e. at; atmospheric pressure) leaving a bubbler thirty feet deep (the depth at the Fraser-Surrey Wharf) has, almost six times as much energy, as a bubble of the same volume of free air leaving a bubbler four feet deep (the usual water depth in the laboratory flume), To compare the effect of water-depth ( D ) and the rate of-25 air^discharge (Q.) on the available, energy i n the bubbler, l e t D + H A us consider again the energy equation: E " H A ( V W Q A ) An -g A and i t s p a r t i a l derivations, w.r. to Q A and D: 3E D + HA — = H . Y An • „ •— = constant at constant depth. 3QA A\ A ^ Therefore, at constant depth, the energy i s a linea r function of the air^discharge. 3E H Furthermore, — = H a ( Y W Q A ) - ^ - ^ , — = - v w 3D2 A • W A ( D + H A ) 2 Obviously,, the second derivative i s always negative, implying that an increase i n depth w i l l increase the energy at an ever decreasing rate. Therefore, i t i s evident that the available energy i n the bubbler i s affected more by the a i r discharge than by the water depth. Searching for a relationship between the upward currents induced i n the water by the screen of r i s i n g air-bubbles, and the (12) amount of a i r released by the bubbler, S i r Geoffrey Taylor drew an analogy between this upward flow of water and the upward flow of a i r caused by a heat source, such as a candle flame. He reasoned that a volume (v) of air-bubbles would give the same buoyancy to a unit volume of water as a ri s e i n temperature (0) Q would give to, a i r at absolute temperature (T), jLf v = Y° (This v 6 idea i s perhaps easier to see If: we put y = —;. a volume of a i r v then gives a unit volume of water the same decrease i n density as a temperature r i s e 6 gives to an arbitrary volume of a i r at 26 temperature T ) . To f i n d an analogy between the v e r t i c a l currents induced i n the water by bubbles and those induced i n a i r by heat, we release i n water a volume V of a i r from a unit length of bubbler, and we release i n a i r H c a l o r i e s of heat per second from V a l i n e source one centimeter long, so that H = --—; (p = density of a i r and s = s p e c i f i c heat of a i r ) . C l e a r l y , the same amounts of energy are involved, creating the same d i s t r i b u t i o n of v e r t i c a l currents. Taylor then included the v e r t i c a l v e l o c i t y by putting H o /psw6(dx), where w = v e r t i c a l a i r v e l o c i t y , x i s a h o r i z o n t a l coordinate. ((1)(dx)(w)p) i s the mass of the volume of heated a i r passing through a h o r i z o n t a l face per unit time. Considering the whole ho r i z o n t a l plane, bounded by a unit length heat source and x, we have H= Xpws6dx; 6 s u b s t i t u t i n g t h i s H and v « — Levi i t of S o u r c e A / 1 _ 1 / / / cx.\.f • Y into V = H(psT), we have «= /wvdx, f o r p and s constant. Taylor, r e f e r r i n g to the work by Schmidt (1941) on currents above a h o r i z o n t a l l i n e source of heat, expressed the v e r t i c a l v e l o c i t y as a function of x and z: w = W q f ( — ) , since, as was shown by Schmidt, the heat spreads out l i n e a r l y so that x i s proportional 27 to z. ViL, being an arbitrary term, was chosen by Taylor to be the maximum v e r t i c a l velocity i n the centre of the r i s i n g column. Taylor then, again referring to Schmidt's theory, put W q a K(Hg/psT)] an experimentally proven equation with the constant K about 1.9. When we now substitute into this, equation the previously derived expression H = VpsT, we arrive at the maximum v e r t i c a l water current, produced by an air-^discharge "V per second per linea r foot of 1/3 bubbler: W q = K'QFg), , where W q i s the maximum upward water ve l o c i t y i n feet per second, V i s the volume of a i r i n cubic feet per second at the depth of submergence of the bubbler, and K i s a constant, approximately 1,9. 28 SECTION I I I LABORATORY TESTS I I I - l Calibration of O r i f i c e Meter i i i • 8-inch Pipe Leading to Flume Most of the laboratory tests of the air-bubbler were carried out i n a st e e l and glass flume, t h i r t y feet long, f i v e feet high, and one and one-half feet wide. An 8-inch diameter water-supply pipe leading to the flume had already been f i t t e d with an uncalibrated o r i f i c e plate (Line 8.071"; Bore 4.974"). To measure the flow into the flume during experiments with air-bubbles i n moving water, a three-feet long, d i f f e r e n t i a l manometer was permanently i n s t a l l e d and connected to the supply pipe on each side of the o r i f i c e plate. The o r i f i c e meter was calibrated as follows: A v e r t i c a l , sharp-crested, rectangular suppressed weir was b u i l t near the downstream end of the flume. For this type of weir, the discharge Q i n c.f.s. i s expressed i n terms of the head 3/2 (H) of water ( i n feet) above the weir: Q = kbH , where b i s the length of the weir crest i n feet. According to C.W, Harris, k = 3,27 + 1.5(^) 2 + •£; D i s the height of the weir crest i n feet H 2 (H < 0.4D). The term 1.5 (—) i s the correction for velocity of Q approach and incomplete v e r t i c a l contraction. The term — i s the correction for f r i c t l o n a l drag ( v i s c o s i t y ) , where C = 0.020 for fresh water at 56°F (the temperature of the water entering the flume). The head (H) on the weir was measured by a hook gauge i n a plexiglass s t i l l i n g w e l l , placed outside of the flume and connected 29 to i t and fa r enough upstream from the weir to avoid the down- drop curve. p o l e t o spl i t? 0*. r-M^C L*. y\ cLa y - S Cot_e T weLt. hose. _ Connection • f l o o r o"f "TI V / / / / / / / , / / / / / / / V / f//s//>/// / / / / /*///// //// / /// //,/ r///'/ //S> 7 W S / "Datum" (zero reading of the hook-gauge) was obtained by setting up a surveyor's le v e l outside the flume and moving the hook gauge to a position where the t i p of the gauge would be le v e l with the brass weir crest, which was made exactly horizontal. The elevations were measured with a graduated l e v e l l i n g rod to an accuracy of 0.001 foot. J irje of & i Kir r o d w e i , r U 00 U i t i i l i ' r i c j w e l l i r 30 A f t e r the datum (zero reading) had been established, the main valve to the flume was opened i n increments to produce corresponding increments i n the manometer readings of about 0,5 inch and the weir hook gauge read. The procedure was repeated both ways ( i . e . fo r increasing as w e l l as decreasing flows) and the r e s u l t s p l o t t e d as a cartesian graph. This was followed by a double logarithmic graph merely to detect any i r r e g u l a r i t i e s i n the readings (see figures 5 and 6). The maximum discharge a v a i l a b l e was found to be 5.79 c . f . s . III-2 Laboratory Investigations to Determine Hydraulic Slopes as a C r i t e r i o n for Incipient Motion of Bed Material To assess the p o s s i b i l i t i e s of an air-bubbler as a method to prevent shoaling of bed load, i t was necessary to determine the hydraulic conditions under which i n c i p i e n t bed-load movement would occur i n front of the wharf. I t was reasonable to assume that bed load contributed i n some measure to the shoaling at the Fraser-Surrey Wharf, i n conjunction with the deposition of suspended sediment. I t would be very d i f f i c u l t to observe bed-load movement i n the r i v e r due to t u r b i d i t y , depth of flow and high w a t e r - v e l o c i t i e s . Therefore, c e r t a i n variables were selected which were known to a f f e c t bed-load movement and which could r e a d i l y be measured i n the f i e l d . By t e s t i n g the i n t e r a c t i o n of these variables i n the laboratory and then measuring the same variables i n the f i e l d , the hydraulic conditions at which i n c i p i e n t bed-load transport would occur, could be predicted. 31 Several important variables involved i n the inc i p i e n t (threshold) movement of bed-load are combined i n du Boy's Law: The t r a c t i v e shear stress (T) exerted by a moving l i q u i d on a boundary surface of any material i s r = yRS, where y = s p e c i f i c weight of the l i q u i d , R •= wetted perimeter, S = hydraulic slope, i c e . the sine of the angle of slope of the t o t a l energy gradient, which i s the same as the slope of the hydraulic grade l i n e (water- surface slope), and the slope of the channel bed i n steady, uniform, turbulent flow. By measuring y, R and S i n the laboratory flume at the instant when the bed pa r t i c l e s of a certain size commenced to move, T •, the c r i t i c a l t r a c t i v e shear stress for incipient motion, was obtained. I f s i m i l a r measurements i n the proto type revealed a shear stress larger than T ., i t was reasonable to assume that bed load movement occurred i n the proto type. To measure the hydraulic slope (S) i n the laboratory, the fixed s t e e l and glass fume, already referred to, was employed with a plexiglass s t i l l i n g w e l l connected to each of the upstream and downstream ends. The hose connections to the s t i l l i n g wells were i n the fl o o r of the flume, 18 feet apart. Each s t i l l i n g w e l l contained a plexiglass hollow cylinder, weighted with leadshot and suspended from a short brass cantilever mounted on top of the flume, ( v i d o f i g o 7 ) , Strain gauges connected to a s t r a i n indicator were attached to the top and bottom surfaces of the cantilevers. Both cylinders were of equal dimensions and equal weights. The s t r a i n gauges and the s t r a i n indicator formed a complete Wheatstone bridge I V 32 with a balanced condition at E = o, i c e , when the water levels i n both s t i l l i n g wells were at the same height. However, when the water levels were not at the same height, the differences i n buoyant forces acting upon the cylinders would create d i f f e r e n t bending moments i n the c a n t i l e v e r s , r e s u l t i n g i n a p o s i t i v e or 13 negative reading of the s t r a i n i n d i c a t o r To c a l i b r a t e the foregoing equipment, both s t i l l i n g wells were f i r s t disconnected from the flume and connected d i r e c t l y to each other with a p l a s t i c hose. Water was then added u n t i l the cylinders were p a r t i a l l y submerged. A f t e r a s u f f i c i e n t time for the water le v e l s i n both s t i l l i n g wells to reach s t a t i c equilibrium, the s t r a i n i n d i c a t o r was set at zero. As a check, this procedure was repeated several times to make ce r t a i n that the recorder pen would return to zero, regardless of the heights of the water le v e l s i n the s t i l l i n g w e l l s . ( I t should be empha sized that the equipment was designed to measure differences i n water surface heights, not i n d i v i d u a l heights.) To determine the r e l a t i o n s h i p between the recorder units and actual differences i n water-surface heights, both s t i l l i n g wells were p a r t i a l l y f i l l e d with water to the same elevation and then disconnected from each other. In one of the s t i l l i n g w e l l s , a point gauge, equipped with an e l e c t r o n i c switch was capable of reading to an accuracy of 10"^ foot. To t h i s s t i l l i n g w e l l , water was added and the Increase i n elevation read on the e l e c t r o n i c point gauge and compared with the reading of the recorder. A f t e r a number of r e p e t i t i o n s , i t was found that two units of the recorder 33 diagram corresponded to a difference i n water-surface heights between the two s t i l l i n g wells of 0,01 feet. During this c a l i b r a t i o n the l i n e a r i t y of the measurements was also tested. In the flume study, p a r t i c l e - s i z e s were selected which most commonly occurred i n bed-material samples obtained at the approaches to the wharf and separate flume tests were performed on each selected f r a c t i o n separated out by sieving. The bottom of the flume was covered with.a thin layer of sand of a p a r t i c u l a r p a r t i c l e size (or f r a c t i o n ) ; flow was imposed on the sand bed and increased very slowly u n t i l incipient motion was observed. With the aid of a magnifying glass, the observer watched for the f i r s t sand p a r t i c l e s to become agitated.and "stand out" ( i . e . , protrude from the sand bed), When incipient motion occurred, the rate of flow was kept constant and the water depth read by a point gauge with an electronic switch (a neon l i g h t indicating contact of the point with the water surface). The recorder showed the difference i n height between the water surfaces i n the two s t i l l i n g w e l l s , from which the hydraulic slope could be determined. The tests were repeated several times, mainly to acquire good judgement In determining incipient motion. The 14 results were generally lower than the published values (Straub) but agreed w e l l with the results of sim i l a r laboratory studies with Fraser River sand at the University of B r i t i s h Columbia i n 1955. (The l a t t e r studies were carried out with varying depths of water and are extensively described i n a report by 34 Professor E.S. Pretious, issued to the Department of Publ i c works of Canada^,) Apart from these other studies, the following values were obtained f o r the c r i t i c a l t r a c t i v e shear stress ( T ) : c Diameter of sand p a r t i c l e s 0,25 mm: T = 0,20 l b / f t 2 c Diameter of sand p a r t i c l e s 0,15 mm: T c = 0,017 l b / f t 2 Diameter of sand p a r t i c l e s 0,10 mm: T £ = 0.012 l b / f t 2 Normally, tests of this nature are made with t i l t i n g flumes i n which the water surface i s made to agree with the bedslope, thus ensuring uniform flow at constant depth. In these t e s t s , the depth was not constant. To obtain r e l i a b l e values of x c, the water depth had to be measured at the point where i n c i p i e n t motion occurred. Thus i n c i p i e n t motion was allowed to occur near the intake of the hose to the s t i l l i n g w e l l , where the water depth could be measured accurately with a point gauge and e l e c t r o n i c switch. III-3 Determination of S e t t l i n g V e l o c i t i e s of Fraser River Sand The upward v e l o c i t y of the water current induced by the r i s i n g air-bubbles should be at least equal to the s e t t l i n g v e l o c i t y of the biggest sand p a r t i c l e s i n s t i l l water. I f these p a r t i c l e s are assumed to be sph e r i c a l with a density of 2,65, then t h e i r s e t t l i n g v e l o c i t i e s In s t i l l water vary with t h e i r diameters as follows: P a r t i c l e s smaller than 0,15 mm i n diameter obey Stokes 1 Laws v = 0.545 d 2 ' — p a r t i c l e s larger than 2.0 mm s ]i obey Newton's Law, v g = 14,38\/~_y I where d =. diameter i n mm, p = density i n grams/cm3 v i z , 2,65, (the density of quartz i s 35 14 regarded as being c h a r a c t e r i s t i c of a l l sediment ); y = dynamic vi s c o s i t y i n poises and v = s e t t l i n g velocity i n centimeters/second. s A zone of t r a n s i t i o n between the two laws covers the behaviour of spherical p a r t i c l e s between 0.15 mm and 2,0 m, so that, roughly speaking, the relationship between s e t t l i n g v e l o c i t y and p a r t i c l e s i z e , can be summarized as follows: d < 0.15 mm : v a d 2 s 0.15 mm < d < 2.0 mm : v ad s 2.0 mm < d : v a Vd. s The relationship can be plotted on a log-log grid and the graph for t = 16',?C i s shown on f i g . 8 . I t has: been shown by a number of investigators (Hazen, Bardwell, e.a,) that sandgrains, generally, behave like.perfect spheres except that the t r a n s i t i o n zone between Stokes' Law and Newton's Law for natural sand p a r t i c l e s i s smaller than that for perfect.spheres, being somewhere between 0,1 mm and 0.3 mm. The sand found i n front of the Fraser-Surrey wharf has a median diameter of s l i g h t l y over 0.1 mm. This being a boundary value i t would c a l l for an actual measurement of the s e t t l i n g v e l o c i t i e s i n the laboratory, instead of assuming values predicted by theory, or from published plots of settlement rates, The s e t t l i n g v e l o c i t i e s of the r i v e r sand were measured with a modified P u r l Siltometer, after the various p a r t i c l e sizes had been separated by a standard sieve analysis. The Purl Siltometer, described i n d e t a i l i n " S o i l s , t h e i r Physics and Chemistry" by A.N, P u r l , i n p r i n c i p l e consists of a plexiglass tube, 200 cm long and,closed at the top end, 36 which stands with i t s lower end immersed i n water i n an open c i r c u l a r metal trough. Both tube and trough are f i l l e d with water, the a i r t i g h t top of the tube maintaining the water-column. A number of segmental aluminium dishes are arranged along the circumference of the bottom of the slowly rotating trough. A sample of wet sand i s released instantaneously from the top of the tube by a switch-rope rated solenoid and distributed among the dishes according to the s e t t l i n g v e l o c i t i e s of the various p a r t i c l e s i z e s. I t i s thus possible to carry out a sediment analysis, obtaining a grain-size d i s t r i b u t i o n based on s e t t l i n g v e l o c i t i e s which i n turn depend on p a r t i c l e s i z e , shape and density. This apparatus was idea l for measuring s e t t l i n g v e l o c i t i e s , p a r t i c u l a r l y because of i t s quick-acting sediment releasing device, modified from the o r i g i n a l by P u r l , for the Fraser River Model Project at the University of B r i t i s h Columbia (1948-62).. The wet sand was introduced into a conical funnel at the top of the sedimentation tube and prevented from entering the tube by a small t i g h t l y f i t t i n g , inverted conical funnel (see fig.9) having i t s brass stem i n the centre of a solenoid. One single switch energized the solenoid, releasing the sample and simultaneously started an e l e c t r i c a l timer. F a l l i n g p a r t i c l e s could be observed cle a r l y over a v e r t i c a l distance of s i x feet; the s e t t l i n g rate of seven p a r t i c l e s i z e s , ranging from 0.074 mm to 2.0.mm. being measured. Care had to be taken to ensure that convection currents would not be created i n the tube by sunlight or other heat sources. The 37 observations were repeated several times and the results (Appendix I I I ) plotted on log-log paper, f i g . 8. The slope of the l i e s t - f i t straight l i n e agrees w e l l with the 45° slope of the t r a n s i t i o n part of the theoretical curve (v g a d) and there i s a tendency at both ends of the range of p a r t i c l e sizes to follow the appropriate Stokes' Law, or Newton's Law. However, i t i s to be noted that nearly a l l experimental results consistently y i e l d s e t t l i n g v e l o c i t i e s higher than those predicted by theory, p a r t i c u l a r l y for p a r t i c l e sizes below 1,5 mm. Flocculation, which might explain the high s e t t l i n g rate of very fine sand, can safely be disregarded i n fresh water, A reasonable explanation for the higher v e l o c i t i e s seems to be that the boundaries of the t r a n s i t i o n region are not cl e a r l y defined. This i s p a r t i c u l a r l y evident i n the lower part of the region. The observed velocity of 2 cm/sec. for a sand p a r t i c l e of 0.105 mm sieve diameter would give a Reynolds number (R) of 1.73; for p a r t i c l e s of diameter 0,074 mm with an observed velo c i t y of 1,3 cm/sec, R = 0.82. This smallest size tested could.then s t i l l be regarded as a boundary case, since the upper l i m i t of the laminar range for which Stokes' Law i s applicable, occurs at a Reynold's number of about 0.8, F i e l d measurements of the dissolved solids contained i n the r i v e r water i n front of the wharf indicated no s a l t water intrusion from the ocean during the freshet (Section IV-3). Therefore, no f l o c c u l a t i o n , with a possible increase i n s e t t l i n g rate of the very fine p a r t i c l e s , could be expected. Hence, the s e t t l i n g v e l o c i t i e s found by the Puri Siltometer Analysis were assumed to 3 8 apply to f i e l d conditions and were employed i n the design of the air-bubbler. I I I - 4 Supply of Compressed A i r to the Air-Bubbler i n the Laboratory Flume Compressed a i r was supplied to the air-bubbler by a compressor having a pressure regulator. To measure the mass flow of a i r . an o r i f i c e plate, bore diameter 1 / 4 inch, was i n s t a l l e d i n the e x i s t i n g one-inch diameter air-supply pipe and a water d i f f e r  e n t i a l manometer was connected to the pipe, upstream and downstream of the o r i f i c e plate, with vena contracta taps i n accordance with ASME spe c i f i c a t i o n s . To avoid abnormal turbulence i n the a i r flow, the o r i f i c e plate was i n s t a l l e d i n a straight stretch of pipe, preceded by a smooth brass section, four feet long and 1 . 0 6 inch i n diameter. A.bourdon gauge, located one foot downstream from the o r i f i c e p l a t e , measured the pressure of the a i r approaching the o r i f i c e , assuming negligible pressure drop across the o r i f i c e . The mass-flow (m) of a i r i n slugs per second could be obtained from the compressible flow equation, i n CYAo/2pAp, where the expansion factor Y = 1 , A q = cross sectional area of the o r i f i c e i n f t 2 , Ap = pressure drop across the o r i f i c e i n psf, obtained from the manometer reading, p = density of a i r i n s l u g s / f t 3 , depending on pressure and temperature, and C = discharge c o e f f i c i e n t . Solving for known quantities (vid. Appendix I V ) , we can express the mass flow i n slugs per second: m - 1 0 . 9 8 x 1 0 - I T C /pAh, Ah being the manometer d i f f e r e n t i a l 39 reading i n inches of water. Because of the very small quantities of a i r entering the bubbler, the use of published tabulated values of C i n calculations of the mass flow of a i r was avoided and the o r i f i c e meter was calibrated d i r e c t l y i n the following manner: A plexiglass box was constructed as shown below, two feet high, one square foot i n cross-section, open at the bottom and a i r t i g h t at top and sides, except for a 1/4-inch diameter opening i n the top to connect the space inside the box with a simple mercury manometer, and a s i m i l a r opening near the bottom's edge to connect the box to the air-supply pipe coming from the o r i f i c e meter. 40 To c a l i b r a t e the o r i f i c e meter, the box, (or gasometer), was completely submerged and f i l l e d with water. A i r was then fed i n t o the box a f t e r passing through the o r i f i c e meter. While the box was held down by the overhead s t e e l frame of the flume, the increasing volume of a i r trapped i n the box forced the water- l e v e l down insi d e the box. When the water-level i n the box reached a point about 1.5 feet below the top of the box (measured by an attached s c a l e ) , the a i r flow was stopped and the time observed. The a i r flow could thus be derived from the quantity of a i r flowing into the box, the a i r pressure: and temperature: Y = r ^ r l b s / f t 3 ; weight flow of a i r w = 7^- lbs/sec, where V K 1 t 0 sec i s the measured volume of a i r (cubical content of a i r space inside box). The c o e f f i c i e n t C followed from w = (32.2 ,x 10.98 x 10-1* /pAh) x C, where p could be calculated and Ah, the observed d i f f e r e n t i a l of the water manometer (inches of water) at the o r i f i c e meter. The c a l i b r a t i o n was c a r r i e d out for d i f f e r e n t values of a i r flow, which again could be c o n t r o l l e d by the pressure regulator. Figure 10 shows the c a l i b r a t i o n r e s u l t s , i n the conventional units of weight flow. To a r r i v e at values for the c o e f f i c i e n t C i n the previous formula, the weight flow had to be converted into mass flow. The question might be r a i s e d whether this method i s only an approximation, since the quantity of a i r entering the gasometer i s measured at the end of a time i n t e r v a l , without considering possible changes i n conditions a f f e c t i n g the a i r flow i n the supply pipe during that time i n t e r v a l . However, while the s e t t i n g of 41 1 I I -AIR • A ' i«. ' S U P P L Y the a i r regulator i s not altered during one pa r t i c u l a r measurement, the only variable affecting the rate of flow of a i r emerging from the air-supply pipe would be the pressure at the discharging end of the pipe. This pressure i s always equal to the hydrostatic pressure which i s constant as long as the box i s held i n the same v e r t i c a l position r e l a t i v e to the water-surface outside the box. Therefore, the amount of a i r collected inside the gasometer during a time i n t e r v a l At, corrected for pressure and temperature and divided by At, represented the rate of flow of a i r i n the supply pipe per unit time at any instant and i s not an average value. The results .obtained for C, although quite consistent, are s l i g h t l y below the published (ASME) values of C i n the previously mentioned flow equation. This might have been caused by the con struction of the o r i f i c e and vena contracta taps. At any rate, they were the observed values for this p a r t i c u l a r o r i f i c e meter as i n s t a l l e d , consequently these values were used i n the computation of a i r flow into the bubblers i n the laboratory tests. I t should perhaps be mentioned that this gasometer was designed to f i l l the need for a simple and reasonably accurate method of c a l i b r a t i n g the o r i f i c e meter i n the time available. In i t s present form, i t i s d i f f i c u l t to handle and much too small for large a i r flows. A more permanent construction to hold the gasometer i n 42 the water would be advisable, l e s t the unwary observer be caught unawares by the rapidly surfacing box. F i n a l l y , the gasometer could be s i m p l i f i e d by eliminating the simple mercury manometer. The difference i n elevation between water le v e l s inside and outside of the box would automatically measure the a i r pressure inside the box. III-5 Laboratory Investigations of Upward Water V e l o c i t i e s Induced by Air-Bubbles To investigate the i n t e r a c t i o n between the r i s i n g a i r - bubbles and the surrounding water, the laboratory flume previously re f e r r e d to, was employed. However, the flume being rather short and the water discharge l i m i t e d , i t was d i f f i c u l t to simulate a r i v e r flow with the correct d i s t r i b u t i o n of v e l o c i t i e s . B a f f l e s at the upstream end and a bulkhead at the downstream end containing small gates at three d i f f e r e n t levels to regulate the flow, helped somewhat to improve the d i s t r i b u t i o n s . The c a l i b r a t i o n of the o r i f i c e meter i n the 8-inch diameter water-supply main indicated an a v a i l a b l e maximum flow of 5.8 cubic feet per second, which gave a mean v e l o c i t y of less than one foot per second i n a depth of f i v e feet of water (flume width 1-1/2 f e e t ) . I n s t a l l i n g side c o n s t r i c t i o n s i n the flume to increase the v e l o c i t y was not p r a c t i c a l since the already l i m i t e d width was needed to accommodate at least a one-foot-length of perforated a i r hose l a i d on the bed of the flume, perpendicular to the flow. Decreasing the depth of water would have increased the flow v e l o c i t y ; however, t h i s flume 43 was selected because I t was the only one In the laboratory capable of accommodating a water depth of fi v e feet. The l a t t e r feature was considered important i n this study involving the v e r t i c a l d i s t r i b u t i o n of v e l o c i t i e s . A horizontal flow i n the flume was less important than the v e r t i c a l flow induced i n the water by the screen of r i s i n g air-bubbles and which had to overcome the s e t t l i n g v e l o c i t i e s of the sediment to prevent deposition. In a horizontal flow, the screen of air-bubbles naturally becomes in c l i n e d i n the downstream direction and loses i t s int e n s i t y . The bubbles spread out and do not follow each other closely; consequently, they are less effective i n entraining the surrounding water than they would be in s t i l l water. The fa m i l i a r hummock or hump i n the water surface, seen above a column of bubbles i n s t i l l water, disappears very rapidly when there i s a horizontal flow. This i s an indication that the k i n e t i c energy given to the water by the bubbles (and converted again into potential energy at the surface i n the form of this hump) has either been dissipated i n turbulent f r i c t i o n or spread out over a large area. Both causes can result i n smaller maximum vertically-upward water v e l o c i t i e s . Therefore, although turbulence i n the r i v e r flow would help considerably to keep the sediment i n suspension, the upward water v e l o c i t i e s induced by the bubbles are quite l i k e l y adversely affected. The complex i n t e r  action of r i s i n g air-bubbles i n a superimposed horizontal flow of water, and i t s effect upon sediment moving either i n suspension or as bed load, could be investigated to advantage i n a very carefully 44 prepared and controlled environment such as existed i n the Fraser River Model at the University of B.C. (1948-1962), or perhaps, at greater cost, i n the proto type. However, with the laboratory f a c i l i t i e s available for the air-bubbler project, the observations of the c i r c u l a t i o n induced i n the water by the screen of r i s i n g air-bubbles were carried put i n s t i l l water. I f the maximum, upward, water v e l o c i t i e s induced by the bubbles i n s t i l l water would be less than the s e t t l i n g v e l o c i t i e s of the sediment grain sizes most commonly found near the wharf, i t was f e l t that l i t t l e would be gained by investigating this relationship i n a super imposed horizontal flow i n a laboratory flume having a limited depth and flow. The laboratory alr-bubblers were made of one-inch (I.D.) diameter polyethylene hose 16 inches long. Five different test sections were prepared with o r i f i c e s ( a i r holes) varying i n dia meter from 0,020 to 1/16 of an inch, with spacings varying from 1/4 to s i x inches. They were successively placed on the bottom of the flume, mid-way along i t s length and perpendicular to the sides. They were readily interchangeable; one end being connected to the laboratory compressed-air supply v i a a 1/4-inch diameter poly f l o tube, leading to the top of the flume and down inside; the other end was s i m i l a r l y connected to a Bourdon pressure gauge i n s t a l l e d outside the flume, at the same height as the air-bubbler hose. With the above arrangement, the bubbles created a r e l a t i v e l y free, two-dimensional water c i r c u l a t i o n p a r a l l e l to the 45 glass side of the flume. This i s a marked advantage of having a flume instead of a square or round tank; p a r t i c u l a r l y when a l i n e source of a i r and not a point source, i s under investigation. A reference grid graduated i n feet was painted on the glass front side of the flume as we l l as on the opposite or rear st e e l side. The st e e l side had previously been painted white, which f a c i l i t a t e d v i s u a l observation of flow patterns, traced by dyes, Some preliminary research on air-bubblers was carried out before the proto type bubblers were placed i n the Fraser River i n May 1966. The available technical l i t e r a t u r e on a i r - bubbler applications was concerned mainly on the effect of r i s i n g bubbles on the upper layers of water, such as occurred i n pneu matic breakwaters, de-icers, pneumatic o i l b a r r i e r s , etc. The o r i f i c e spacing and diameter, which seemed effective for pneumatic breakwaters and de-icers, would not necessarily prevent sediment ation. For these preliminary investigations a 16-inch length of hose with three 1/16-inch diameter o r i f i c e s , spaced s i x inches apart, was placed on the bottom of the laboratory flume at right angles to the flow. To trace the water c i r c u l a t i o n , meriam, neutral o i l , drops ( s p e c i f i c gravity « 1.00), coloured red, were injected into the water at different depths. The Injector was the t i p of a f i n e l y drawn glass tube attached to a c y l i n d r i c a l brass messenger, one-inch long and 3/8 inch diameter, "which could s l i d e along a taut, v e r t i c a l nylon f i s h - l i n e between the water surface 46 and the bottom of the flume. c d - o p 1 ( c^ltxss - t u p i n j e c t o r — "Tiik I i ' * \ a cx-L-t exc K e ol "to ! p ^ v^ Meriam o i l was fed to the glass t i p through a nylon Intracath, 1 mm i n diameter, connected to a syringe outside the flume. The nylon f i s h - l i n e passing through the messenger could be moved p a r a l l e l to i t s e l f and by p u l l i n g on a second nylon f i s h - l i n e , attached to the messenger, the observer could place the messenger at any desired p o s i t i o n i n the water. Although the meriam drops were not employed to measure water v e l o c i t i e s accurately, they mapped a continuous 2-dimensional flow pattern, a d i s t i n c t advantage over point, v e l o c i t y measurements with a current meter. The general flow pattern agreed c l o s e l y with that obsrved by many previous i n v e s t i g a t o r s . I t showed a very rapid upward water movement i n the immediate v i c i n i t y of the bubbles an equally rapid h o r i z o n t a l movement at and near the water surface away from the bubble screen; a weak and rather confused c i r c u l a t i o n downward a few feet away from the bubbles; and a slowly increasing h o r i z o n t a l motion towards the bubbler along the bottom. Near the 47 t Two - D m £ IN 5 I O N A L W A T E R C I R C U L A T I O N " INDUCtsfc S T R l i l N G , AIR B U l i C L l i S F R O h A L I N E i o u n i : A S 0 & - T A I M £ k F R O M T H f O i l £ Is ft. V A T l O ST OP M f f t l A n QROPS bottom, a s l i g h t inward motion away from the walls of the flume towards the centre was also observed, obviously the wal l effect on the circulatory pattern. I t was not possible to observe properly the path of the meriam drops injected into the centre of the screen of air-bubbles. The water v e l o c i t i e s at various points i n the flow pattern increased with an increase of a i r pressure inside the bubbler hose, which depended on the rate of a i r flow. As the injector was moved horizontally away from the bubble screen, the upward v e l o c i t i e s of the injected meriam drops decreased rapidly. The most important observation, however, was the absence of any upward water velocity near the air-bubbler hose. Meriam drops injected between the a i r holes and within approximately four inches above the bubbler, 48 remained nearly motionless. They started to move when injected within an inch horizontally (measured along the hose) of the a i r holes. However, there was obviously a region between the o r i f i c e s which would present no. bar r i e r to the moving bed sediment. Without examining the upward v e l o c i t i e s further, i n other regions, above this p a r t i c u l a r test bubbler, the six-inch spacing had to be rejcted as possible design for the prototype bubbler. After a number of t r i a l s with other spacings and o r i f i c e diameters, ( s t i l l using the meriam drops), a spacing of 1/4 inch and a diameter of 0.0135 inch were selected for the o r i f i c e s of the prototype. This selection was based mainly on attempts to minimize the dead-water region close to the bubbler. An o r i f i c e spacing smaller than 1/4 inch was not considered p r a c t i c a l for the prototype bubbler because i t was f e l t that too many holes per unit length of hose would weaken i t . The hose would probably be subjected to severe tens i l e and bending stresses i n the f i e l d . The small diameter for the a i r holes was favoured over larger diameters because of the limited capacity of the air-compressors available. Another consideration was that, for the same volume of a i r escaping,, a great many small air-bubbles would have a larger t o t a l cross-sectional area than a few large airr-bubbles and would therefore entrain more water. The urgency of preparing the prototype bubblers before the onset of the freshet i n the spring of 1966 temporarily halted the laboratory studies. After a three-months1 period of f i e l d investigations, the laboratory studies were renewed and a 4 9 miniature current meter was i n s t a l l e d i n the flume to replace the meriam drop inj e c t o r . This "Miniflow" current, meter, manufactured by Armstrong Whitworth A i r c r a f t Limited, England, i s primarily designed to measure very low v e l o c i t i e s of flow i n a laboratory. I t consists of a stainless s t e e l probe, 18 inches long and 1/16 inch i n diameter, with a measuring head 0.6 inch i n diameter containing a five-bladed Cobex p l a s t i c rotor. The revolutions of this rotor are counted e l e c t r o n i c a l l y and displayed by three Dekatron counters (Plate 3). A detailed description of the electronic arrangement i s beyond the scope of this thesis but has been published by the manufacturers i n one of t h e i r brochures Only the components of flow velocity perpendicular to the plane of the rotor could be measured. To study the upward water v e l o c i t i e s , therefore, the meter probe had to be horizontal. The connection between the probe and the coaxial cable leading to the Dekatron counters had to remain dry and i t was necessary to be able to move the rotor to any desirable position near the bubble screen. To s a t i s f y the foregoing three requirements, the end. of the probe which was connected to the coaxial cable was sealed i n the horizontal leg of an L-shaped, one-inch diameter st e e l pipe. The v e r t i c a l leg of this pipe could s l i d e i n an adjustable clamp fastened to the top of the flume. Water was prevented from entering the pipe by a rubber plug, which also held the probe firmly i n po s i t i o n , keeping the plane of rotation of the rotor horizontal. J < t r j ii. 50 Pr*.or*>(f W I T H R o T o r s . T o r\fA<,UR£ U P W A R D W A T l f r ? . V E L O C I T I E S 71 &IA. O o o o o Possible errors i n the measurement of water v e l o c i t i e s , caused by the presence of the stee l pipe near the region of flow, were ignored. Approximately 600 velocity determinations were obtained, each requiring at least ten readings. At each point of velocity measurement, f i v e different rates rates of a i r flow were introduced; f i v e different test bubblers were studied, each with.a different o r i f i c e diameter and spacing; the depth of water was varied from fi v e to two feet; the position of the current.meter was varied v e r t i c a l l y between halfra-foot above the bottom of the flume and one. foot below the surface; i n addition, a number of readings were taken i n the lowest layers, between 0.2.foot and 1.0 foot above the bottom of the flume. The position of the current meter was varied horizontally between a point d i r e c t l y above the bubbler and a point three feet from the centre of the bubble screen. The probe was usually kept on the longitudinal centre l i n e of the 51. flume; however, a few measurements were made to investigate w a l l e f f e c t s , by moving the rotor close to one wal l of the flume. As was mentioned e a r l i e r , the a i r flow was measured by a calibrated o r i f i c e meter. Tap water was employed i n the flume tests. Since the miniflow current meter could only register i n conductive l i q u i d s , sodium s i l i c a t e (waterglass) had to be added to the tap water, at a concentration of 1:1000 by volume. I t should be noted that the miniflow current meter registers both direct and reverse flow. The rotor had to be watched carefully at very low flows when turbulence at times might reverse the flow, resulting i n abnormal readings. Very f i n e , almost i n v i s i b l e hairs i n the water, sometimes fouled the delicate rotor spindle; this could e a s i l y be detected by an unexpected sudden drop i n the pulsing rate displayed by the Dekatron counters. However, i t would be good practice to check the rotor frequently, even i f fouling i s not noticeable. Results of Velocity Measurements The tables i n Appendix V show some of the results of veloci t y measurements made and figures 12 to 15 were selected to i l l u s t r a t e the discussion. For ease i n orientation, a cartesian coordinate system i s introduced, the x-y plane.coinciding with the bottom of the flume, the y-axis along the bubbler, the x-axis along the longitudinal centre l i n e of the flume. The z-axis, measured from the or i g i n upward, denotes the direction of the upward v e l o c i t i e s , induced 52 i n the water by the r i s i n g air-bubbles. Figure 12 represents the upward velocity distributions at levels 0,5, 1, 2 and 3 feet above the bottom of the flume, for an. o r i f i c e diameter of 0,020 inch and a spacing of 0.250 inch. The depth of water was four feet. Although measurements of water velo c i t y were taken for f i v e different rates of flow of a i r , only two sets are plotted, v i z . for a maximum of 3,2 x 10— lbs/sec/ft length of a i r hose and a minimum of 0.9 x 10"^ lbs/sec/ f t . The two curves for each l e v e l may be regarded as an envelope of a l l f i v e rates of a i r flow investigated. For the sake of c l a r i t y of the graph, the bubble screen i s not shown. The graph shows clea r l y how the volume of water moving v e r t i c a l l y upward increases with v e r t i c a l distance above the bubbler. However, the upward ve l o c i t y does not change appreciably with v e r t i c a l distance. There i s a very pronounced peak velocity i n the centre of the bubble screen, with a maximum upward velocity of 1,60 feet per second, occurring two feet d i r e c t l y above the air - rbubb ler . 12 The measurements closely confirmed Taylor's prediction that the maximum upward water v e l o c i t i e s induced by the r i s i n g air-bubbles are proportional to the t h i r d root of the volume rate of a i r flow. The constant k i n his equation W q = k(Vg) 5 3 1 / 3 was calculated from the average of ten different values of volume rate of a i r flow, each of the ten values being the average of twenty measured repetitions. I t was found to be 1 . 4 9 , giving 1 / 3 W q (the maximum upward water velo c i t y i n f.p.s.) = 1 . 4 9 (Vg) , where ¥ i s the volume rate of a i r flow In c.f.s. (see appendix VI). Bulson^, who carried out large-scale experiments with pneumatic breakwaters at Southampton, England, found a maximum horizontal velocity at the water surface, induced i n the water by the bubbles, 1 / 3 U O = 1 . 4 6 (gv) feet per second, and a maximum upward waters- velocity W Q = 0 . 7 9 U . (Bulson had at his disposal a large graving dock and a water depth of 3 4 feet.) Of p a r t i c u l a r interest i n this project were the maximum, upward water v e l o c i t i e s very close to the r i v e r bed, induced by the r i s i n g bubbles. Detailed velocity measurements were made i n s t i l l water at levels 0 . 2 , 0 . 4 , 0 , 6 , 0 . 8 and 1 , 0 feet above the bottom of the flume, d i r e c t l y above the bubbler. Figures 1 3 to 15 represent the distributions of the upward water v e l o c i t i e s at 0 . 2 feet depth intervals between 0 , 2 and 1 . 0 feet, d i r e c t l y above the bubbler. I t should be recalled that i n a l l of these tests the bubbler hose was perpendicular to the longitudinal axis of the flume (the x-axis i n figures 1 2 to 1 5 ) . Each of the three figures 1 3 to 1 5 refers to one pa r t i c u l a r o r i f i c e diameter and spacing (both o r i f i c e diameter and spacing were changed for each test bubbler to keep the volume rate of a i r flow approximately the same for a given a i r pressure i n the bubbler). 54 Conclusions drawn from observations with the meriam drops were confirmed by the miniflow current meter: there was hardly any upward v e l o c i t y of the water between the o r i f i c e s when spaced s i x inches apart. Even at a v e r t i c a l distance of one foot above the bubbler, the upward v e l o c i t y was very small. Figures 12 to 15 a l l show a one-foot length of bubbler hose, but with o r i f i c e spacings reduced by factors two and four. The upward v e l o c i t i e s of the water between the o r i f i c e s are c l e a r l y greater with smaller o r i f i c e spacings, above the 0.4 foot l e v e l . Above a l e v e l of 0.5 feet , measured above the bubbler hose, there i s hardly any v a r i a t i o n i n the upward water v e l o c i t i e s along the Y-axis, for a bubbler with an o r i f i c e spacing of one and one-half incheso I t i s noteworthy that the upward water v e l o c i t y above the 1/16-inch diameter o r i f i c e s , increases much more rap i d l y with height than that above the smaller diameter o r i f i c e s . This i s probably r e l a t e d i n some way to the s i z e of the bubbles and the quantity rate of a i r flow per o r i f i c e . The above remark does not contradict Taylor's analogy, which relates the quantity rate of a i r flow per foot of bubbler to the maximum upward v e l o c i t y Of the water. The maximum upward water v e l o c i t y was never attained below a l e v e l of two feet above the test bubbler, i n any of the tests performed i n the laboratory i n connection with t h i s p r o j e c t . The r e s u l t s of the laboratory experiments with varying depths of water were inconclusive. A l t e r i n g the water depth i n the flume from two to f i v e f e e t , was apparently too narrow a 55 range to obtain a r e l i a b l e i n d i c a t i o n of the e f f e c t of depth upon upward v e l o c i t i e s at a given point, other variables remaining constant. There seemed to be a s l i g h t increase i n upward v e l o c i t i e s with depth at points outside the bubbler screen, although there was no such trend i n the bubble screen i t s e l f . Since the results were inconsistent and inconclusive, they were rejected. To test the e f f e c t of the sides of the flume on the observed water v e l o c i t i e s , the upward v e l o c i t i e s at a distance of one inch from a side of the flume were compared at regular i n t e r v a l s with those normally observed i n the centre of the flume, a l l other conditions remaining the same. The v e l o c i t i e s near a side of the flume were found to be 10% to 20% lower than those at the centre. 56 SECTION IV FIELD INVESTIGATIONS IV-1 Determination of Hydraulic Slopes as a C r i t e r i o n for Incipient Motion of Bed Material Inspection of Federal Public Works sounding records showed a tendency for the r i v e r bottom to form bedwaves and dunes i n front of the Fraser-Surrey wharf during a freshet. This tendency was 18 also c l e a r l y observed and recorded In the f i e l d i n 1955 by the s t a f f of the Fraser River Model Project. I t was also observed i n the Fraser River Model tests. I t was therefore assumed that bed movement contributed to the shoaling during freshet periods. To ascertain that the hydraulic conditions i n the approaches to the wharf supported this assumption, the c r i t i c a l t r a c t i v e shear stress necessary for impending movement of the various fractions of Fraser River sand found on the r i v e r bed i n front of the wharf, was investigated i n the laboratory ( I I I - 2 ) . From these laboratory r e s u l t s , the minimum slope of the water surface which would s a t i s f y the hydraulic conditions for Impending movement of bed material near the wharf was calculated. I t was realized that this method had some debatable features: regardless of how accurately the slope of the water surface could be measured between two points i n the r i v e r near the wharf, i t was quite unlikely that the slope at a l l intermediate points would be exactly the same. However, the distance over which the slope would be measured was r e l a t i v e l y small (the length of the wharf). Consequently, the difference between the upstream and downstream water-surface elevations at the wharf would be small and probably very sensitive to fluctuations i n water levels caused by passing ships, wind and ti d e . F i n a l l y , the computation of the c r i t i c a l t ractive shear stress from the observed water-surface slope would be a debatable approximation. In calculating the c r i t i c a l t r a c t i v e shear stress (T ) , the boundaries of the body of water responsible for this shear stress are determined by the hydraulic slope, depth and the hydraulic radius. In wide and r e l a t i v e l y shallow a l l u v i a l r i v e r s , the hydraulic radius i s ofter closely approximated by the r i v e r mean depth. Since the analysis was only concerned with the hydraulic conditions i n the immediate v i c i n i t y of the wharf; replacing the hydraulic radius by the average l o c a l depth and a r b i t a r i l y assuming boundaries within which only the water-surface slope and average depth were known, was an approximation which could lead to discrepancies. , However, to gain at least some indication of the behaviour of the r i v e r bed near the wharf, i t was decided to measure the difference i n water-surface elevations between a point near the upstream end of the wharf and one near the downstream end, and assume a uniform, s t r a i g h t - l i n e water-surface p r o f i l e between these two points, which were 1030 feet apart. The method for measuring water-surface slopes i n the laboratory flume (III-2) could not be employed i n the f i e l d because the wharf did not provide the necessary r i g i d base on which to mount the small brass cantilevers. Furthermore, the lengths of the wires for s i m i l a r instrumentation at the wharf 58 would lead to inaccuracies and the t i d a l o s c i l l a t i o n s varying from four to s i x feet would have to be eliminated,, An e n t i r e l y different electronic and mechanical device was developed i n the C i v i l Engineering Instrument shop by Messrs. H.W, Schmitt, electronics technician and E.M.White, machinist. Since the instrumentation employed i n the laboratory flume test and i n the f i e l d i s f u l l y described i n an unpublished manuscript pre- 13 pared j o i n t l y by Mr. Schmitt and Professor E.S. Pretious , a short description of the f i e l d method and Its principles may su f f i c e here. A plexiglass f l o a t , eight inches O.D. and A inches long, was contained i n the upstream and downstream s t i l l i n g w ells. Each f l o a t was suspended by a very fine wire, guided over a two and one-half inch diameter plexiglass drum and p a r t i a l l y counter balanced by a small weight. The drum was mounted on a small wooden platform above each s t i l l i n g w e l l and attached to the shaft of a potentiometer, which converted the v e r t i c a l movement of the f l o a t into a small D,C, voltage. Any difference i n the water levels between the upstream and downstream s t i l l i n g wells was transferred to the two s l i d e r s A and B (see figure 17) of the two potentiometers, resulting i n a potential difference, which was measured by a voltmeter and recorded continuously on a graph. The bottom of each s t i l l i n g w e l l was closed, except for a small hole (1/4 inch diameter), lined with a short length of pipe, i n the exact centre, which e f f e c t i v e l y damped transient surges caused by 59 passing ships, waves, etc. The design of the c i r c u i t eliminated the effect of t i d a l o s c i l l a t i o n s on the voltmeter readings, although a small correction would have to be applied to the readings i n order to correct for the time travelled by the tide wave between the two ends of the wharf. Assuming no r i v e r flow and the t i d a l disturbance reaching the two s t i l l i n g wells at exactly the same instant, both floats would r i s e or f a l l an equal amount during a small time i n t e r v a l . Sliders. A and B on the potentiometers would then move an equal amount and (see figure 17), the potential differences between A and F, Q and A, would remain equal to those between B and R, S and B respectively, resulting i n zero voltmeter reading. With a tide wave having a velocity of propagation of about 28 feet per second i n .25 feet of water (V = /|d~ for a shallow water wave), a t i d a l disturbance would not reach the two s t i l l i n g wells at exactly, the same instant. A. r i s i n g tide with a l o c a l range of three feet i n f i v e hours would, at a given Instant, cause a difference i n .elevation between the water levels i n the upstream and downstream s t i l l i n g wells of 10 30 3 3c 12 n n x 'A'mn = 0.07 inch. Since the difference between 28 5 x 3600 the upstream and downstream water-surface elevations, caused by the r i v e r flow alonej was expected to be anywhere between 0.1 and,1.0 inches, there would be a measurable contribution to the slope,.by the tide wave. 60 The c a l i b r a t i o n of the equipment was f i r s t carried out i n the Hydraulics Laboratory of the University of B r i t i s h Columbia by setting up the measuring instruments and placing the two floats i n buckets f i l l e d with water. One potentiometer s l i d e r was set at i t s centre and the s l i d e r on the other potentiometer moved to a position giving a zero reading on the voltmeter. One of the buckets was then raised 0.125. inches (by aluminium s t r i p s ) , r e sulting i n a graph recording, which depended on the voltmeter j reading. This procedure was repeated several times, then reversed and f i n a l l y extended to larger d i f f e r e n t i a l s i n height to check the l i n e a r i t y of the voltmeter readings. One of the major d i f f i c u l t i e s encountered i n the design of the f i e l d instrumentation was the selection of the s t i l l i n g w e l l locations, p a r t i c u l a r l y the upstream one. The most.suitable location for the upstream we l l would have been the outer corner of the wharf; however, this corner was subject to considerable vibration caused by the large a i r compressor supplying the a i r - bubblers.. The corner was also exposed to wind, waves and f l o a t i n g debris and the instruments might be damaged by mooring lines and the movements of ships. To avoid these disturbing influences, the s t i l l i n g w e l l was b u i l t at the blunt upstream end of the main wharf near the point where the catwalk commences (see figure 16). This location proved to be w e l l protected, although the p i l i n g and fenderboom tended to retard the r i v e r velocity somewhat, possibly resulting i n a s l i g h t l y higher water l e v e l l o c a l l y . The other s t i l l i n g w e l l was b u i l t close to the downstream corner of the wharf. 61 Both s t i l l i n g wells were fastened securely to the p i l i n g with heavy stee l brackets and timbers. An i n i t i a l attempt to measure, the water-surface slopes was made during the last week of June 1966. A zero reading on the voltmeter was established at l o c a l high water, when the incoming tide and r i v e r flow produced slack-water conditions at the wharf. Unfortunately, the wharf, at this time was occupied by ships. Considerable a c t i v i t y with, heavy equipment near the upstream part of the wharf disturbed the very sensitive instrumentation so much that, the slope measurements had to be deferred to a more favourable period. Also there was evidence that continuous heavy rain, during this period had. swelled the timbers supporting the platforms, introducing an error i n the common reference datum. On July 29, 1966, the instruments were again set up and this time the slope of the water-surface was measured successfully during a f u l l , t i d a l cycle under ideal conditions. The maximum difference i n water-surface elevation between the two s t i l l i n g wells was recorded at. 0,69 inches, y i e l d i n g a slope of 0.56 x 10"^. The t i d a l contribution to this difference i n elevation was calculated to be only 0,02 inches (vid. APP.VII). The maximum water-surface slope on.that day occurred about two hours before l o c a l lower low water at New Westminster and v i r t u a l l y coincided with a maximum surface vel o c i t y i n the r i v e r , 50 feet off the wharf, of s i x feet per second i n the seaward direction. For bed-sand p a r t i c l e s of 0.25 mm diameter, the water- surface slope required for impending bed-load movement, would be i n 62 the order of 0.1 x 10"^, corresponding to a difference i n elevation of 0.13 inches between the water levels i n the upstream and down stream s t i l l i n g wells. The graphs of July 29 and July 30 indicate a difference i n elevation greater than 0.13 inches for a period equal to 2/3 of a complete t i d a l cycle. Since the observations were carried out near the end of the freshet (Fraser River Discharge at Hope, B.C. was 170,000 cfs on July 30), we could postulate that the waters-surface slope necessary for impending bed-load movement exists for at least two-thirds of the time during the freshet and probably longer at higher r i v e r flows. F i e l d investigations and model tests carried out by the Fraser River Model Project indicated that active bed-load movement accompanied by bed waves and dunes should be expected i n this area when the Fraser River Discharge at Hope exceeds 225,000 cfs. REMARKS. Although this method of measuring the slope of the water surface has merit i n regard to accuracy and s e n s i t i v i t y , the f i e l d tests brought to l i g h t certain deficiencies which should be corrected before future measurements are made. For establishing a reference datum for the recorder, a zero slope has to be accurately established between the two measuring, points under consideration (vld. the water levels i n the two s t i l l i n g w e l l s ) . This i s possible i f the r i v e r flow can momentarily be halted by a high flood t i d e , assuming no wind effects i Theoretically, i t should be possible to determine the difference i n water-surface elevation between these two points at any instant by o p t i c a l precise l e v e l l i n g , comparing the result with the 63 simultaneous reading of the recorder (voltmeter) and thus obtain a reference datum. However, no matter how w e l l the surges i n the s t i l l i n g wells are damped, there i s always an o s c i l l a t i o n which makes an. instantaneous comparison by precise l e v e l l i n g a most fr u s t r a t i n g , i f not impossible task. Before employing this instrumentation on a r i v e r where there i s no reversal of flows (no t i d a l e f f e c t ) , one would have to introduce some refinements and modifications i n the present design. As for the locations of the s t i l l i n g w e l l s , i t would be advisable to b u i l d them away from the wharf, on a more s o l i d foundation and connect them to submerged pipes ending somewhere near the wharf face. By moving these pipes at w i l l , one could measure the water-surface slope between any two points i n the approaches to the wharf, without having to move the s t i l l i n g wells. The s t i l l i n g wells i n the present study were r i g i d l y attached to the p i l i n g of the wharf. They were each ten feet long,.well beyond the l o c a l range of tide and r i v e r stages which could occur during, the freshet and summer. However, the observations.were made near the end of the freshet, when the water-surface at low tide approached the bottom of the s t i l l i n g w e l l . At this point, surface waves had a disturbing effect on the readings (yid. Appendix V I I I ) . The s t i l l i n g wells should therefore be made manually adjustable, i . e . able to move v e r t i c a l l y up or down so that.they can be adjusted p e r i o d i c a l l y to keep the bottom always submerged s u f f i c i e n t l y to eliminate o s c i l l a t i o n s due to surface waves. 64 Finally, the question might arise whether this rather sensitive method of measuring very small water-surface differences in elevation oyer a short distance could not have been avoided by comparing the records of existing automatic tide gauges located upstream and downstream from the wharf. Unfortunately, the nearest installed automatic recording tide gauges were at the Rice Mills' wharf, 7 miles downstream and at the Federal Public Works Wharf in New Westminster, 1 mile upstream (see figure 1). Over such a large distance, the curved water-surface profiles, due to the unsteady flow caused by the tides cannot be ignored and i t would be.quite wrong to use the difference in water-surface elevations between these two gauge stations as a base for calculating the differences in water-surface elevations between Intermediate points by linear proportion. It was therefore necessary to install the instruments in locations close enough apart to be able to ignore the curvature of the water-surface profile and at the same time far enough apart to provide measurable differences in water-surface elevations. IV-2 Survey of River Currents in the Vicinity of the Fraser-Surrey Wharf As was mentioned in the Introduction, the location of the Fraser-Surrey Wharf on the convex side (Plate I) of a bend in Annieville Channel makes its approaches naturally vulnerable to shoaling. However, not only the location of the wharf but also the.alignment of the wharf face relative to the main river current 65 inevitably contributes to shoaling. E a r l i e r f l o a t studies of flow patterns i n Annieville Channel, i n the prototype and la t e r on the Fraser River Model at U.B.C., demonstrated quite cl e a r l y that the wharf face diverges i n the downstream direction from the r i v e r current, tending to create a dead-water area and back- eddy along the downstream face of the wharf. Moreover, the blunt upstream end of the wharf forces the flow away from the wharf, further aggravating the foregoing conditions. Freshet peak flows suppress this dead-water area considerably, but even so, there .• ^ i s s t i l l a noticeable retardation i n current velocity i n the area bounded by the wharf face and a l i n e from the upstream end of the wharf to a point about 100 feet off the downstream end. To map the flow pattern i n this area more accurately, the.surface currents were measured a number of times, generally just before and after l o c a l low water at New Westminster. The wharf had to be free of ships, of course, a necessity which limited the number of observations that could be taken. The flow pattern was obtained as follows: The position (F) of a passing f l o a t i n the r i v e r could be fixed from the wharf by i t s bearing r e l a t i v e to the wharf face (an angle of 90° for a l l measurements); i t s v e r t i c a l angle and the height of eye (h) above the water l e v e l , giving the distance: d = h tan BOF. The wharf face was marked off at intervals of 100 feet and the v e r t i c a l distance between eye and water l e v e l measured by tape. Small wooden f l o a t s , painted orange, to be eas i l y distinguishable 66 from f l o a t i n g debris, were thrown into the r i v e r at various distances from the wharf face and from various points along the wharf. They were subsequently carried downstream by the current. Walking along the wharf, ahead of the f l o a t , the observer would wait for the f l o a t to pass a 100 or 200 foot mark, etc., take the v e r t i c a l angle by sextant, and record the time the f l o a t travelled between marks. To define the instant of passing, the fl o a t was lined up with some object on the opposite r i v e r bank, which had previously been i d e n t i f i e d by turning off a horizontal angle of 90° at each point of observation. Average surface v e l o c i t i e s over distances of 100 or 200 feet, as wel l as positions, could thus be mapped for a number of f l o a t s . This simple, one-man method could not be carried out too far from.the wharf, because the tangent of an angle close to 90° changes rapidly and a s l i g h t inaccuracy i n the sextant v e r t i c a l angle could therefore lead to a considerable error i n distance (d). At large distances,only a theodolite would give accurate results. However, the area of interest was well within the l i m i t s of accuracy 67 of a sextant and after some practice, a s u f f i c i e n t number of observations could be obtained within a reasonable time to obtain a good flow pattern. A time l i m i t of one-half hour for a complete set of observations minimized changes i n current v e l o c i t i e s due to t i d a l e f f e c t s . The results (figures 18 and 19 are two sample sketches of the f l o a t survey) show a considerable retardation of surface velo c i t y i n a triangular area enclosed by the wharf face and a l i n e connecting the upstream corner of the wharf with a point about 80 feet out from the 2 + 00; mark. A dead-water area near the wharf extends approximately from 8 + 00 to 4 +00; down stream form 4 + 0 0 , the flow near the wharf appears to slowly accelerate again. Judging by the surface flow patterns the most adverse flow, conditions near the wharf exist i n the area downstream of 8 = 00. I t i s i n this area that shoal deposits more rapidly than elsewhere i n the approaches to the wharf. In addition to the f l o a t survey, measurements of the sub surface .curents were taken during the 1966 freshet. The Water Resources Branch of the Department of Mines and Technical Surveys provided a current meter and operators at regular i n t e r v a l s . The current meter (Price, Gurley 622 A) measured the r i v e r v e l o c i t i e s at YQ depth i n t e r v a l s , from the surface down to one foot above the river.bed. The vel o c i t y traverses were taken at four different locations (see figure 16) near the wharf, at r i v e r discharges (metered .at Hope B.C.) varying from a freshet maximum of 281,000 cfs 68 (June 15) to a low of 150,000 cfs (July 5) and at different stages of the tid e . A velocity p r o f i l e at the buoy (vid. figure 20) on June 15 (peak discharge at Hope, see hydrograph, figure 25), 120 feet off the upstream end of the wharf, shows a maximum veloc i t y of 7.5 feet per second at a depth of 0.2 of the t o t a l depth, which i s i n close agreement with the normal, v e r t i c a l , velocity p r o f i l e s of r i v e r flow. The veloc i t y traverse for intervals of one-foot depth was taken one-half hour after Lower Low Water at New Westminster on that p a r t i c u l a r date, and was w e l l outside of the influence of the wharf. Under these conditions, i t can reasonably be assumed that, i n the approaches to the Fraser-Surrey Wharf, the r i v e r v e l o c i t y , at the surface or just below the surface, ra r e l y , i f ever, exceeded 7.5 feet per second i n 1966. The conventional current meters employed did not measure directions of flow. This was rather unfortunate because no conclusive proof that there was no reversal of flow In the sub surface water layers during l o c a l high tide could be obtained. The surface flow at no time reversed during the peak of the freshet period. However, i f there was a sub-surface reversal of flow, we might expect a zero v e l o c i t y , or at least a velocity close to zero, somewhere i n the v e r t i c a l , v e l o c i t y p r o f i l e s . Close inspection of the graphs does not reveal such a reversal at any point, not even i n the last velocity traverses taken on the 5th of July 1966, when the freshet was nearly over and when the surface currents near the wharf at l o c a l high tide were one foot per second i n the seaward 69 d i r e c t i o n . From these observations, i t seems reasonable to assume that there was no reversal of flow i n the sub-surface layers during the 1966 freshet period, which extended approximately from the beginning of May to the end of July (the duration of the freshet period w i l l be examined more cl o s e l y i n section IV, paragraph 3). Even i f a reversal of flow occurred during a very high flood t i d e , i t would probably be of such short duration that the general d i r e c t i o n of sediment transport would hardly have been affected. Furthermore, flow reversals when they do occur, take place i n the surface layers, p a r t i c u l a r l y upstream of the l i m i t of i n t r u s i o n of the salt-water wedge. Figures 21 to 24 represent a group of v e l o c i t y traverses taken i n one day. (June 29, 1966) at four d i f f e r e n t locations along the wharf face. P r o f i l e s obtained at the same locations on other days during the freshet have s i m i l a r c h a r a c t e r i s t i c s : they a l l show v e r t i c a l , v e l o c i t y d i s t r i b u t i o n s near the wharf which are much more i r r e g u l a r than those at the buoy, 120 feet o f f the up stream end of the wharf. This i s p a r t i c u l a r l y noticeable at the mid-point of the wharf. Considering a l l observations c o l l e c t i v e l y , the average flow v e l o c i t y at mid-depth along the wharf might roughly be estimated to be about one h a l f of the v e l o c i t y at mid-depth near the buoy. However, d e f i n i t e conclusions should not be drawn from the l i m i t e d amount of data a v a i l a b l e . The measurements could only be taken when the wharf was free of ships and t h i s made planning and organizing d i f f i c u l t ; e s p e c i a l l y since the crowded harbour f a c i l i t i e s 70 at New Westminster forced ships to s h i f t berths without much advance notice. I t was rather a fru s t r a t i n g but not uncommon experience to watch a ship approach the wharf a few hours after arrangements had been made with the Water Resources Branch for a current meter survey. IV-3 A Study of the Sedimentation at the Approaches to the Fraser-Surrey Wharf To properly introduce a study of the sedimentation occurring i n front of the wharf, a b r i e f review of the terminology employed i n the subject would, perhaps, be i n order. Sediment i s transported by a r i v e r as suspended sediment, i f i t i s i n suspension i n the turbulently moving water, or as bed load i f i t r o l l s and slides along the bed. In addition, there i s wash load, consisting of very fine p a r t i c l e s of s i l t and clay which tra v e l with about the same velocity as the r i v e r , and the dissolved solids (salts and chemicals). I f some of the bed load bounces along the bed, i t i s called s a l t a t i o n load. When the sediment settles down and becomes, at least temporarily, part of the r i v e r bed, i t i s cal l e d bed material. Wash load, although normally comprising the largest part of the t o t a l sediment load transported, does not s e t t l e readily as long as there i s appreciable flow and therefore, hardly affects r i v e r sedimentation. On the other hand, i t could affect very much the s i l t a t i o n of a reservoir. Shoaling features i n a t i d a l r i v e r r e f l e c t the sediment characteristics and hydraulic behaviour. The variables to be 71 considered i n a study of shoaling which occurs i n front of the Fraser-Surrey Wharf are: suspended sediment; bed load; r i v e r discharge; t i d e ; r i v e r geometry. Relatively few detailed f i e l d investigations of the sedimentation i n this part of the r i v e r had been carried out i n the past and we again had to reply heavily on the cooperation of the Water Resources Branch of the Department of Mines and Technical Surveys (the present Department of Energy, Mines and Resources), who made available t h e i r sedi mentation personnel, f i e l d equipment and laboratory. As with the survey of the l o c a l r i v e r currents, the sediment sampling program was hampered by ships and barges berthed at the wharf. Therefore the only way to arrive at reasonable conclusions concerning the sedimentation trends at the wharf, was to compare the scattered sediment data gathered there with data obtained regularly at Port Mann, B.C. The Water Resources Branch maintain t h e i r nearest sediment f i e l d station at Port Mann, which i s about three miles upstream from the wharf and about two miles upstream of New Westminster. Unfortunately the suspended-sediment sampler (P61, weight 80 lbs) had to be transferred from Port Mann to the Fraser- Surrey Wharf, which meant that no sim i l a r measurements at Port Mann were available for comparison on that day. However, by interpolation between data taken on the previous and following days at Port Mann, a f a i r l y r e l i a b l e relationship between sediment conditions at the wharf and Port Mann could be established. 72 At Port Mann, the suspended sediment concentration i s measured dally by depth Integrating and point Integrating samplers. The samples are analysed i n the Water Resources Sedimentation Laboratory at New Westminster, resulting i n daily t o t a l concentrations, corrected for the amounts of dissolved s o l i d s . The t o t a l concen tr a t i o n i n grams per l i t e r for the Fraser River at Port Mann varies from 0.01 i n the winter to about 0.5 during the freshet, at times going as high as 0.9 during a rapid r i s e of the freshet, which normally occurs i n the middle of May (vid. hydrograph, F i g . 25). The maximum seasonal concentrations at Port Mann v i r t u a l l y coincide with the maxima i n the r i v e r hydrographs for Hope, B.C. A maximum daily t o t a l concentration of 0.9 grams per l i t e r occurred at Port Mann two days before the Hope discharge of 261,000 cfs on May 13, 1966; another maximum daily t o t a l concentration of 0.5 was record ed three days after the freshet peak discharge of 281,000 cfs on June 15, at Hope. Both of these daily maxima were obtained from observations taken at Local Lower Low Tide during the freshet season. The tides have a marked effect on the sediment concentrations because the r i v e r flow, which transports the sediment, has a reduced * "Concentration", i . e . the weight of the sediment found i n a unit weight of the water-sediment mixture, i s a misnomer. I t does not recognise the obvious fact that water moves faster than suspended sediment (except wash load) and that therefore a sampler measures concentrations which are too low. A more appropriate term would be sediment "charge", the r a t i o of the weight of the sediment to the weight of water per unit time. However, to avoid confusion the term "concentration" w i l l be maintained. "Total" concen t r a t i o n implies the sum of suspended load, wash load and dissolved s o l i d s , as an average over a v e r t i c a l . 73 velocity at high tide i n the New Westminster area and an increased velocity at lo c a l low tide. Therefore, i n comparing sediment concentrations based on r i v e r discharge i n this area from day to day, the phase of the tide at which these concen trations were measured should be specified. Even then, such a comparison can only be approximate, since the tide curve keeps varying from day to day, with different maximum and minimum tide heights. Moreover, the daily discharges of the Fraser River at New Westminster depend mainly on the upland fresh-water discharges (metered at Hope), modified by the t i d a l effects superimposed on them. However, heavy rains i n the water sheds downstream of Hope, (e.g. Harrison Lake, P i t t Lake, etc., see F i g . 1), can also markedly affect the trib u t a r y inflow. The sediment concentration i s an extremely complex function of these varying tides and r i v e r discharges and i t may take several years of data c o l l e c t i n g i n the New Westminster area before this function can be derived and before i t w i l l be possible to predict at which r i v e r discharges and tide phases shoaling w i l l commence and stop. This knowledge would be of great p r a c t i c a l value to harbour authorities because i t would enable them to operate t h e i r anti-shoaling devices (such as air-bubblers, or perhaps under water Jets) i n an economically feasible manner. To i l l u s t r a t e the dependence of the r i v e r gauge heights at New Westminster on the tides i n the S t r a i t of Georgia, the New Westminster tide curve between June 22nd and June 25, 1966 was 74 traced from the automatic gauge record and the hourly heights of tide at Point Atkinson (entrance to Vancouver Harbour, see Fig. 1) plotted on the same graph (Fig. 26). When examining the observed tide curve at New Westminster, B.C. for the freshet of 1966, one observes that the concentration of suspended sediment at Port Mann at l o c a l low water i s , rough ly speaking, twice as large as that at l o c a l high water. A good example of the foregoing occurred on June 19th, 1966, when the suspended-sediment concentration was 0.176 at higher high water, and 0.349 at lower low water. On March 28th, 1966, the concentrations were 0.013 and 0.026 respectively. There are exceptions to the above trend, depending on the r i v e r conditions upstream, ( v i z . s l i d e s , a collapsing r i v e r bank, sudden r a i n f a l l over a tributary water shed, et c . ) . The suspended-sediment concentration at Port Mann, averaging about 0.02 grams per l i t e r during the winter, increased markedly at the beginning of May 1966; an increase which coincided with a sharp r i s e i n the river-discharge at Hope. In the f i r s t week of that month, the concentration during l o c a l low tides averaged about 0,1 grams per l i t e r , r i s i n g to 0.9 grams per l i t e r on May 11th. The r i v e r discharge at Hope rose above 150,000 cfs on May 8th and from then on the records at Port Mann show a concen tr a t i o n during l o c a l low tides remaining well above 0.1 gram per l i t e r u n t i l the end of July when the r i v e r discharge at Hope de creased rapidly to s l i g h t l y above 150,000 cfs. I t has not been established that this discharge of 150,000 cfs 75 at Hope indicates a def i n i t e t r a n s i t i o n between normal and above- normal suspended-sediment concentrations at Port Mann. The Water Resources Branch has only been c o l l e c t i n g sediment data i n the New Westminster area (Port Mann) since the early summer of 1965 and i t would take a number of years of record to prove this figure right or wrong. However, the available data so f a r , indicate a marked tendency for the r i v e r to increase i t s suspended- sediment carrying capacity i n the New Westminster area when the  r i v e r discharge at Hope i s above 150,000 cfs. Therefore, i n studying causes of sedimentation, i t seems reasonable to use the discharge of 150,000 cfs at Hope as a reference for the duration of freshets i n the lower Fraser River, u n t i l further information i s available. Figure^ 27 to 30 are t y p i c a l p a r t i c l e - s i z e d i s t r i b u t i o n curves of the suspended sediment i n the Fraser River at Port Mann, B.C. They represent the p a r t i c l e - s i z e distributions at 5, 15, 25 and 35 feet depths on June 30th, 1966, taken at l o c a l higher high water. The curves show an increase i n the median diameter of the suspended sediment from 0.0092 mm at fi v e feet depth, to 0.012 mm at 35 feet depth, with no p a r t i c l e s larger than 1.0 mm at depths less than 15 feet below the surface. On that same date, during l o c a l lower low water, a t o t a l concentration of 0.312 grams per l i t e r was measured at the Fraser- Surrey Wharf. I t was not possible to compare this value with the concentration at Port Mann because the sampler was the only one 76 available i n the area at that time, thereby preventing simultaneous measurements at the two places. However, on the previous day at Port Mann, the concentration at exactly the same l o c a l tide height • was 0.351; the concentration at Port Mann on the following day (July 1) was not measured d i r e c t l y at the same tide height, but after comparison with other measurements on that day and on following days, could quite safely be assumed to l i e between 0.30 and 0.35. Other comparisons indicated a further close correspondence between sediment concentrations at Port Mann and the Fraser-Surrey Wharf. I t should be remembered that the entire flow of the Fraser River passes Port Mann, whereas i n passing the Fraser-Surrey Wharf i t has been diminished by the off-takes into the North Arm and Annacis Channel which amount to a t o t a l reduction of about 20% i n the flow entering the t r i f u r c a t i o n . The point sampler at our disposal did not col l e c t s u f f i c i e n t amounts of suspended sediment to plot a p a r t i c l e - s i z e d i s t r i b u t i o n curve. The station at Port Mann pe r i o d i c a l l y obtains such d i s  tributions by the pumping method ( i . e . c o l l e c t i n g samples at ten- second intervals from r i v e r water, which i s pumped up continuously by a pump on a catamaran while she crosses the r i v e r ) . However, i t seems unlikely that the suspended sediment at Port Mann would change i t s p a r t i c l e - s i z e d i s t r i b u t i o n as i t travels downstream without r e f l e c t i n g a change i n the t o t a l concentration. Since f i e l d observations did not reveal any appreciable change i n t o t a l concentration of the suspended sediment between the Port Mann and the Fraser-Surrey Wharf, this can be taken as evidence that the d i s t r i b u t i o n curves of the suspended sediment at these two places are s i m i l a r . This conclusion may seem bold, lacking s u f f i c i e n t s t a t i s t i c a l evidence. The margin of error, however, may be negligible compared to the daily changes i n p a r t i c l e - s i z e d i s t r i b u t i o n curves at one p a r t i c u l a r location. The curves shown i n figures 27 to 30 are distributions obtained at l o c a l higher high water. The Water Resources Branch f i l e s i n New Westminster contain a s i m i l a r set of curves for the same date, obtained at l o c a l lower low water. At each depth, the curve representing p a r t i c l e size d i s t r i b u t i o n at low water shows a marked s h i f t to the r i g h t , compared to the one at high water. This s h i f t to the right i s i l l u s t r a t e d by a comparison of the median diameters: Median Diameters of Suspended Sediment at Port Mann, June 30, 1966 Depth Median Diameter (mm) (feet) Local Higher High Water Local Lower Low Water 35 0.012 0.096 25 0.012 0.035 15 0.010 0.046 5 0.009 0.023 Within less than s i x hours, as the tides changed from low to high, the median diameters decreased by factors varying from two to eight! This s t r i k i n g daily fluctuation i n p a r t i c l e - s i z e d i s t r i b u t i o n at Port Mann, which most l i k e l y w i l l follow a sim i l a r 78 va r i a t i o n near the wharf, makes i t p r a c t i c a l l y impossible to determine or predict exactly the amount of suspended sediment involved i n the shoaling at the wharf. There can hardly be any doubt that suspended sediment contributes largely to this shoaling. The concentration of suspended sediment during the freshet i s at least ten times, frequently twenty to t h i r t y times, greater than i t i s at normal flows. Furthermore, the r i v e r decelerates considerably i n the immediate v i c i n i t y of the wharf and simply cannot support this heavy sediment load i n suspension. While measuring the concentrations of the suspended-sediment samples collected at the wharf, the concentrations of dissolved solids were also obtained (by evaporation and weighing). In this connection, values were found, ranging between 53 and 74 milligrams per l i t e r . The s a l i n i t y of the S t r a i t of Georgia, around the mouth of the Fraser River, i s about 25.7 (eight-years average for June at East Point). The samples were taken as low as one-half foot above the r i v e r bed and at r e l a t i v e l y low r i v e r discharges (about 200,000 cfs at Hope), when the incoming flood tide would have been able to penetrate the r i v e r further upstream than i t would at much higher discharges. However, the laboratory analysis of the dissolved solids established beyond reasonable doubt that there i s no s a l t water intrusion i n the r i v e r area off the Fraser-Surrey Wharf during a freshet, a fact which had already been indicated by the sub-surface current measurements (IV-2), In contrast with suspended sediment, the p a r t i c l e - s i z e d i s -79 tributions of bed load and bed material appear to be much less sensitive to t i d a l e f f e c ts. Figures 31 and 32 are d i s t r i b u t i o n curves of bed material and bed load at Port Mann, compiled from the Water Resources Branch records for a r b i t r a r i l y chosen dates, June 24th and 25th, 1966. The curves show an over-al l increase i n p a r t i c l e sizes for both bed load and bed material with decreas ing heights of tide (see also the tide curves for New Westminster and Point Atkinson for these two p a r t i c u l a r dates, figure 26). The median diameter of bed load i n mid-stream increases from 0.37 to 0.43 mm; near the shore, from 0.20 to 0.22 mm as the lo c a l tide height drops. The p a r t i c l e s are larger i n mid-stream (where i t i s deeper), a common phenomenon. As for bed material, i t s median diameter increases from 0.39 to 0.41 mm i n mid-stream and from 0.21 to 0.29 mm near the shore. Bed material on the average i s s l i g h t l y coarser than bed load, which i s to be expected. I t i s d i f f i c u l t to distinguish sharply between bed load and bed material; bed material becomes bed load as soon as the c r i t i c a l t r a c t i v e shear stress (III-2) has been exceeded. For a given hydraulic slope, bed material would always be s l i g h t l y coarser than bed load. Therefore, to examine the composition of sediment which an air-bubbler would have to prevent from s e t t l i n g , a study of the bed material found at the Fraser-Surrey Wharf would eliminate the need for any further information regarding bed load. At the Fraser-Surrey Wharf, bed-material samples gathered at various points throughout the freshet season i n 1966 (as well as 80 a few samples taken In 1965, show an almost constant median diameter of 0.14 mm, and a great s i m i l a r i t y In the shape of t h e i r d i s t r i b u t i o n curves. This median diameter of 0.14 mm i s , roughly speaking, more than one-half the median diameter of the bed material sampled near the shore at Port Mann. As the Water Resources Branch collects more information con cerning sedimentation behaviour i n the New Westminster area, some of the assumptions made i n this discussion may be refuted. How ever, these assumptions, although not supported by strong s t a t i s t  i c a l evidence based on continuous long-term records, are based on accurate data gathered and analyzed so far by experienced and w e l l trained observers employing up-to-date equipment. IV-4 I n s t a l l a t i o n and Operation of the A i r - Bubblers at the Fraser-Surrey Wharf The design of the air-bubblers and thei r i n s t a l l a t i o n on the r i v e r bed.at the Fraser-Surrey Wharf, were based on preliminary laboratory tests and limited information concerning the hydraulic conditions i n the r i v e r i n front of the wharf. By the time these preliminary tests had been completed and arrangements had been made for the f i e l d surveys and financing of the bubbler equipment, the freshet was impending. The operation of the prototype bubblers was essential to obtain a clear understanding of th e i r behaviour and p o s s i b i l i t i e s . Problems most certainly would arise during the f i e l d t e s t s , which perhaps would never be exposed i n the laboratory. The time a v a i l -81 able for the f i e l d t e s t s , however, was limited by the duration of the freshet, while the laboratory tests could be carried out i n d e f i n i t e l y . I t was therefore decided to proceed with the design of the prototype bubblers and planning t h e i r lay-out on the r i v e r bed as quickly as possible, even though future research and f i e l d investigations might c a l l for a different approach. Another important consideration was the rapidly increasing river,, flow during the i n i t i a l stages of the freshet, which would make i t more d i f f i c u l t to place the bubblers i n the planned positions. The experiments performed with drops of Meriam neutral o i l i n the laboratory flume (III-5) had clea r l y shown the importance of a very close spacing of the o r i f i c e s i n the bubble hose. During these preliminary experiments, a i r holes with a diameter of 0.0135 inches, spaced 1/4 inch apart, and an estimated rate of flow of free (atmospheric) a i r i n the order of one cubic foot per minute per foot length of bubbler hose, created a f a i r l y good upward motion i n the water near the bed of the flume, although accurate measurements had to be deferred to a l a t e r date. This arrangement appeared to be a reasonable basis for the design of the bubblers i n the f i e l d . Larger o r i f i c e s would admittedly create larger bubbles with higher upward v e l o c i t i e s . However, not much was known about the flow of compressed a i r through small o r i f i c e s i n a polyethylene pipe. A very conservative o r i f i c e diameter of 0.0135 inches (corresponding to the smallest d r i l l l o c a l l y available) was selected to allow for a pertain margin of erroi? i n the design of the t o t a l length of the bubblers. Once 82 the bubblers were anchored on the r i v e r bed, i t would be a simple matter to add another bubble hose i f the a i r compressor was not operating at i t s f u l l capacity. However, i t would be almost impossible to a l t e r o r i f i c e diameters and spacings i f the t o t a l cross-sectional area of the o r i f i c e s proved to be too large for the capacity of the compressor, because part of the bubbler hose (outer end) would then remain f u l l of water. The bubblers were to be placed i n approximately 30 feet of water at the wharf. To supply one cubic foot of a i r per foot length of bubble hose at a depth of 30 feet i n water, a compressor would have to deliver nearly two cubic feet of free a i r per foot of bubble hose. I t was intended to make the bubble hoses each 120 feet long '•V and place them i n a direction perpendicular to the face of the wharf. For each bubble hose, 120 feet long, the compressor would have to deliver about 240 cubic feet of free a i r . A compressor having a capacity of about 500 cfm could then be expected to supply s u f f i c i e n t a i r to operate two bubblers, each of the above length. Two, portable, rotary-screw compressors were rented from the Atlas Copco Organization; one a large compressor (Cummins) delivering 620 cfm of free a i r at 100 p s i and a smaller one (Deutz), delivering 365 cfm of free a i r at 100 p s i . I n i t i a l l y , two poly ethylene hoses, one inch i n diameter and 150 feet long, were prepared for the large compressor and one si m i l a r hose for the small compressor; However, when the large compressor was obviously operating well below i t s capacity, a t h i r d hose of the same design as the other two 83 was added. A l l bubbler hoses were prepared i n the C i v i l Engineering Laboratory at the University of B.C.,. shortly before the freshet. More than 5000 a i r holes were d r i l l e d i n each 120-foot length of the perforated part of the hose. The remaining, unperforated length of 30 feet led from the r i v e r bed up to the water surface, where i t was connected to a rubber hose f i f t y feet long and two inches i n diameter, leading to the compressor on the wharf. The r i v e r ward end of the perforated length was closed with an aluminium plug. To overcome the buoyancy of the a i r hoses, s t e e l cables, 5/8 inches i n diameter, were fastened to the hoses. One-foot length of polyethylene hose of one-inch inside diameter with a density of 0.97 would be subject to a buoyant force of (4) (144) ( 6 2 * ^ a 0.3A'.lbs. (ignoring the w a l l of the hose, which had a density almost equal to the water). One foot length of s t e e l cable 5/8, inches i n diameter would have a submerged weight of (IW)2 ( 4 8 ? " 6 2- 4> = 0- 9 0 l b s . . w h i c h was w e l l above the buoyant force on the hose. As a further precaution against the drag forces of the,current, both ends and centre of each hose were weighted with.short lengths of boom chain, weighing 80 lbs each, which were attached to the cable, two chains at each end and one i n the centre. The bubbler hoses were placed on the r i v e r bed during the l a s t week of May, 1966, In the positions indicated on figure 16. At the upstream end of the wharf, three p a r a l l e l bubblers, 75, feet apart, were connected to the 620 cfm compressor. They were 84 pointing i n a direction perpendicular to the wharf face to produce three, p a r a l l e l , barriers or screens of r i s i n g air-bubbles each 100 feet long. (The perforated portion of each hose was actually made 120 feet long to allow for i r r e g u l a r i t i e s i n the r i v e r bed and bends, etc . ) . The smaller compressor, when not used as a mobile air-supply unit i n attempts to remove loc a l i z e d shoals near the wharf, or as a replacement of the large compressor i n case of a break-down, was kept at mark 6 + 0 0 (about half-way along the wharf) and attached to the fourth, bubbler. The rather isolated position of the fourth bubbler was chosen, not so much to prevent shoaling as to observe the effect of a single bubbler on the adjacent r i v e r bed. The r i v e r bed at the fourth bubbler being f l a t and sandy, any change i n the configuration of the bed here due to the currents induced i n the water by the screen of r i s i n g air-bubbles, would immediately be apparent on an echo- sounder graph. Similar observations were not possible i n the area near the upstream end of the wharf, where the other three bubblers had been placed. The r i v e r bottom there was irr e g u l a r and very uneven due to sunken logs and other debris. The 100-ton snagboat "Samson", a sternwheeler, was made available by the Department of Public Works, Canada, to place the bubblers on the r i v e r bed. The previously mentioned steel cables, 5/8 inches i n diameter, were fastened to the bubble hoses with stainless s t e e l clamps at six-foot intervals and with marline at intermediate, two-foot intervals (vid. plate 4 ). Care was necessary to keep the steel cables from blocking the a i r holes 85 since there was evidence obtained from f i e l d t r i a l s In 1965 that the a i r j e t s entraining fine sand, were capable of eroding holes i n the st e e l cable. The bubblers were sunk at l o c a l high t i d e , when the r i v e r currents were r e l a t i v e l y slack. After the "Samson" had anchored" about 100 feet off the wharf, the end of a bubbler cable was connected to a steel ring which was hauled across and above the water by s l i d i n g i t along a t i g h t , 1/2-inch diameter wire con necting the wharf to the "Samson" (plate .4).. The end of the f i r s t bubbler, paid out from the upstream end of the wharf, was fastened to a l - r l/2 ton concrete block. This block was also the anchor for a large, conical, river-buoy, painted red and marking the up-stream, r i v e r ward boundary corner of the air-bubbler lay out (see plate 5). The r i v e r ward ends of the three other bubblers were ^ ach weighted with two boom chains already described, after being pulled on board the "Samson". They were then dropped i n the r i v e r approximately f i f t y feet upstream from their, planned positions, to allow for the set of the current. The middle of each bubbler was anchored with, one boom chain, the land>-ward end with, two boom chains as already described. Bubbling operations commenced on May 24th, 1966, and continued u n t i l the 12th of July. The PR 620 compressor operated for a t o t a l of 868 hours and the PR 365 operated 950 hours. The i n s t a l l a t i o n of' the bubblers was executed almost without a flaw, thanks to the powerful aid of the large, w e l l equipped and manned "Samson". Altogether d i f f e r e n t , however, was the operation 86 r\s loo1 of the bubblers themselves. Many unexpected d i f f i c u l t i e s were encountered which seemed to be absent i n the laboratory but which haunted the f u l l - s c a l e f i e l d t r i a l s . I t soon became clear that the Fraser-Surrey Wharf was not as i d e a l l y suited for f i e l d tests of the bubblers as had o r i g i n a l l y be anticipated. Although i t would have been impossible to estimate beforehand the exact number of ships berthing at the wharf during the 1966 freshet period, r e l a t i v e l y few ships were expected to venture near the wharf during this period, i n view of the severe shoaling which occurred there during the previous freshets. Nevertheless, i t was only one day after the i n s t a l l a t i o n of the f i r s t bubblers, that a large ship, the " A t l a n t i c Breeze" (see plate 5), berthed at the wharf; i t s h u l l partly covering the upstream bubblers. This ship along with other ocean-going vessels or cargo barges occupied the up stream ha l f of the wharf for a t o t a l of 27 days out of the 49 that . 87 the bubblers were i n operation. A ship with a draught of 26 feet i n 30 feet of water would only leave four feet of water under her keel. Sediment which was carried upward along with the flow induced i n the water by the air-bubbles, would almost immediately be stopped by the ship's bottom and deflected downwards. Travelling along the h u l l after being arrested i n th e i r ascent, the air-bubbles would entrain some of the surrounding water, but i t i s unlikely that this induced water flow, after part of i t s energy had been dissipated i n f r i c t i o n , would be capable of carrying much sediment to higher levels i n the river-flow alongside a ship. On the other hand, a ship's h u l l would create a l o c a l constriction i n the river-flow, resulting i n a higher water velo c i t y between h u l l and river-bed. and a possible removal of bed material from underneath the. ship. This bed material might gradually accumulate immediately downstream of the stern of a ship due to back eddies, but part of i t would l a t e r be agitated by the ship's propeller during her departure and be carried further downstream. A ship, occupying a berth which normally shoals due to low r i v e r v e l o c i t i e s , appears to help prevent shoaling. For example, i n figures 18 and 19, a ship berthed between 8 + 00 and 4 + 00 would cle a r l y be effective as a shoal i n h i b i t e r by giving to the plan outline of the wharf a configuation which almost coincides with the streamlines of the r i v e r . However, the frequent use of the wharf by ships defeated the e f f i c i e n t operation of the bubblers and became a disturbing factor i n the f i e l d tests. A further serious setback was the e r r a t i c behaviour of the 88 large a i r compressor at the upstream end of the wharf. This unit suffered i t s f i r s t breakdown one.day after i t started to operate and had to be recalled for a three-day overhaul. I t went out of order again within an hour after i t s return to the wharf and went, back to the repair shop for a further five-day period. From then on, this compressor had numerous, minor breakdowns and needed frequent attention. Its speed varied from 1500 to 1700 rpm, corresponding to a flow rate between 510 and 575.cfm of free a i r , based on a c a l i b r a t i o n table provided by Atlas Copco. This was about 80 cfm below i t s designated capacity. The smaller compressor performed w e l l , operating s l i g h t l y below capacity and needing very l i t t l e attention. Its usual position on the wharf was at mark 6 + 00, as mentioned previously. Both compressors were recalled for overhauls on July 12th, 1966 and were replaced by two small compressors, a Deutz Diesel of' 315 cfm and a Ford Diesel of 160 cfm. These units were used partly for the bubblers at the upstream end of the wharf and partly i n attempts to remove a lo c a l i z e d shoal hump at mark 8 + 0 0 . Un- fortunately, t h e i r performance was unsatisfactory. The larger compressor went up i n flames i n the early morning of July 24th and the other one, after frequent minor f a i l u r e s , suffered a major breakdown on July 28th. The contributions made by these l a s t two compressors to the overall e f f o r t may be v i r t u a l l y disregarded; the l a s t day of effe c t i v e bubbling operation thus being July 12th, 1966. The buoy together with some fragments of the bubblers were picked up by the "Samson"-on July 29th, 1966. 3 9 Que p r e r e q u i s i t e f o r the successful outcome of the e n t i r e project was the r i v e r v e l o c i t y at the wharf downstream from the bubblers. Sediment ra i s e d by the air-bubble3 to a higher l e v e l i n the r i v e r - f l o w had to be c a r r i e d downstream past the wharf by a s u f f i c i e n t l y strong r i v e r current. Except during the peak cf the freshet, the mean r i v e r v e l o c i t i e s i n an area downstream from 8 + 00, and extending about 100 feet out from the wharf face, r a r e l y appeared to exceed two feet per second. Appendix IX i s « reproduction of a chart for determining the largest grain sizes to reach a deposit area, appearing i n "The Hopper Dredge" (U.S. Array Engineers) ns f i g . 188. This chart i s of s i g n i f i c a n c e to a g i t a t i o n dredging and was quite useful i a the design of the bubblers (which i n essence are a form of a g i t a t i o n dredging). Reference to the chart and a short c a l c u l a t i o n showed that p a r t i c l e s l a rger than 0,16 usn i n diameter would not cl e a r the wharf when c a r r i e d downstream from a point near the r i v e r ourface at mark 8 + 00 , by a current with a mean v e l o c i t y of two feet per second and assuming the depth at the point of deposit to be 30 fee t . This mtar.fi (vld, f i g . 33), that at beat, not more than 40% of the sediment agitated by the air-bubbles and c a r r i e d a l l the way up to the water surface> would be transported past the wharf. The foregoing percentage i s based on theory and may a c t u a l l y be much lower. At any rate, the absence of a s u f f i  c i e n t l y strong h o r i z o n t a l flow v e l o c i t y at the downstream portion of the wharf, was without a doubt one of the moat adverse con-90 ditions surrounding the project, from the viewpoint of a l l e v i a t i n g shoal. Some p r a c t i c a l observations and features of the bubblers may be worth mentioning here. There was no. evidence of clogging of the a i r holes through out the f i e l d operation, nor of any gradual f i l l i n g of the hoses with fine sand. The compressors were stopped frequently (due to breakdowns and also to permit echosounding), allowing the ri v e r water to f i l l the hoses. I t was suspected that sand would be l e f t behind i n the hoses after the a i r had forced the water out again. However, there was no trace of sand i n any of the hose sections (including one end section) which were salvaged at the end of the operation. Accumulation of sand (shoal) on top of the bubblers did not affect t h e i r performance i n the f i e l d . This had already been c l e a r l y demonstrated i n the laboratory flume when, with the a i r supply turned o f f , two feet of sand were dumped on top of a bubbler under water. When the a i r was turned on again, the bubbles forced t h e i r way upward through the sand i n a matter of seconds. The a i r holes d r i l l e d i n the polyethylene hose did not retain t h e i r o r i g i n a l diameter but had become smaller after a few hours, apparently due to creep i n the polyethylene. Unfortunately, this shrinkage was not consistent and might we l l be affected by the temperature at which the holes were d r i l l e d . The holes might shrink even more under water. This factor of uncertainty could introduce appreciable errors i n the design of bubblers, p a r t i  c ularly where thousands of a i r holes are involved. The polyethylene hoses should be kept w e l l away from the compressors. The compressed a i r leaving the compressors i s quite hot and can eventually melt the polyethylene material. The best way to avoid a rupture was to keep the polyethylene hoses under water and j o i n them to the compressors by the heavy rubber hoses that came with the compressors. The precaution of anchoring a bubbler to the 1-1/2 ton concrete block proved unnecessary. Those bubblers which were each anchor ed to two 80-pound lengths of boom chain also remained i n position throughout the operation. The polyethylene bubblers should be handled very carefully when placed on the river-bed. The main advantage of using poly ethylene i s that i t i s cheap and readily available; however, the hoses kink and break e a s i l y . I t might be advisable to test a different material i n future experiments of this nature. In deciding the length of bubbler hose to use, i t was assumed that the a i r delivered by the compressor to the bubblers was under s u f f i c i e n t pressure at the furthermost o r i f i c e to overcome the hydrostatic pressure there. This requirement enlisted the results of Stehr's elaborate investigations of the pressure drop i n the bubbler hoses of exactly the same material (polyethylene) but of 4 a s l i g h t l y smaller diameter . Stehr derived an equation (pages 4 307 to 312 of his paper ) for the pressure drop i n an unperforated polyethylene hose: 92 P A = P f- I *W 2 0 . 0 6 8 4 S } - T ° , where P and P are the a i r o o pressures at a downstream point (away from the Compressor) and 2 an upstream point i n the hose, respectively, i n kg/cm ; i s the distance between these two points i n meters; W q i s the a i r v e l o c i t y i n meters per second; d_ i s the diameter of the hose i n mm; T q the temperature, i n degrees k e l v i n , of the a i r i n the hose and g a coeffi c i e n t of f r i c t i o n , which Stehr deter mined empirically and expressed as a function of the mass flow of a i r through the hose: v i z . 8 = 2.48 G 0*14^ W N E R E Q ^ 8 T N E mass flow i n kg/hr. Converted into foot-pounds-seconds units and degrees Fahrenheit and with s l i g h t modification, this equation becomes (see appendix X): P ^ - pressure of a i r i n psia at the far end of the supply hose ( i . e . at the beginning of the bubbler hose); P q ° pressure of a i r in.psia i n the beginning of the supply hose (see following sketch) q Q » flow of a i r (at pressure P Q ) through the supply hose i n c u . f t . / s e c ; &2 = length of supply hose (unperforated) i n feet; Fg = cross sectional area of supply hose i n inch ; T q = temperature i n °F of the a i r i n the supply hose; d 7 = diameter of supply hose i n inches. The f r i c t i o n c o e f f i c i e n t becomes 3 ° 0.82 G ®'^^t where G = weight Z 0 Z 93 flow of a i r i n lbs/sec obtained from G = (q ) (Y ); where Y i s 1 4 4 P O ° 0 ° the s p e c i f i c weight of the a i r , Y Q A R(460 + t ) ' FC * N ^ E 8 R E E S Fahrenheit; R the gas constant, 53.3; P q i n psia. o _i u.r\ pe r'forft.'f eoL |ae.r*fo roA e cL canrfK essoR l. For a rough, but very conservative check of the pressure drop i n the supply hose at the wharf, l e t us assume a length of unperforated polyethylene supply hose, A^, of 100 feet (more than three times the length actually used); the rate of flow of free a i r (at 14.7 psia) to the supply hose = 200 cfm (assuming that the large compressor i s operating at nearly f u l l capacity and that the a i r i s equally distributed over three hoses); and f i n a l l y a temperature T q of a i r i n the supply hose of 50°F (assuming that the temperature of the compressed a i r inside the hose i s about equal to that of the surrounding water; both the polyethylene supply hose and bubbler hose are submerged). A short calculation (see appendix X), using Stehr's modified equation, w i l l show that the pressure drop i n the supply hose w i l l be s l i g h t l y more than YQ °f t n e a * r pressure i n the beginning of the supply hose. ; The a i r pressure gauges on both compressors on the wharf generally registered a pressure of approximately 90 psig while 94 operating the bubblers, corresponding to 104 psia. After passing through the rubber hose into the polyethylene supply hose, the a i r would be at a pressure P ,less than 104 psia (due to f r i c t i o n losses i n the short rubber hose and the connection); the pressure drop i n the polyethylene supply hose would then be no more than 11 p s i . This low value for the pressure drop i s not surprising i n view of the very smooth inside w a l l of these polyethylene hoses. Stehr also investigated the pressure drop i n the bubble hose, i . e . , the perforated section. He measured the a i r pressures at the beginning and the end of the bubble hose (points A and E i n the sketch) and at two intermediate points. His tabulated results show that the pressure drop between the beginning and the end of the perforated hose i s , for the same rate of a i r flow, almost exactly one-third of the pressure drop i n an imperforated hose of the same dimensions and material. This result i s the same as that derived th e o r e t i c a l l y for incompressible flow i n pipes having perforations of constant diameter and uniform spacing throughout, the theory given i n some texts on applied hydraulics. At a pressure drop of less than 11 p s i i n 100 feet of unperforated polyethylene hose, the pressure i n 120 feet of perforated poly ethylene hose would therefore be approximately 4 p s i , giving a t o t a l pressure drop i n the polyethylene hose (perforated and unperforated) of no more than 15 p s i . Additional f r i c t i o n losses would be expected i n the rubber hose and at f i t t i n g s and bends. 95 However, the inside diameter of the rubber hose was twice that of the polyethylene hoses and since only two f i t t i n g s were involved and no sharp bends, i t may be safely assumed that, under the above conditions, the a i r pressure i n the river-ward end of the bubble hoses, a f t e r deduction of pressure losses, was well above the hydrostatic pressure of 13 p s i . ( i . e . 30 feet of water). IV-5 Sounding To examine the e f f i c a c y of the bubblers i n reducing sediment ation i n front of the Fraser-Surrey Wharf, the hydrographic launch "Sounder" of the Federal Public Works.Department carried out weekly sounding surveys at the immediate approaches to the wharf during the freshet period, The launch "Port Fraser" of the Fraser River Harbour Commission took d a l l y soundings In the same area, both operations being c a r r i e d out whenever the presence of ships did not prevent them. .The sounding l i n t s of the Public Works Department were perpendicular to the wharf, 25 feet apart and extending approx imately 120 feet out from the wharf face. The sounding lines of Fraser River Harbour Commission were p a r a l l e l to the,wharf, 20 feet apart and as far out as 100 feet from the wharf-face. The "Sounder' survey results were compiled on f i e l d sheets. Two blue pr i n t s of these f i e l d sheets are included as appendices XI and XII. The two prints are records of the hydrographic surveys made on May 31st, 1966 shortly before the compressors were operating more or less contin uously, and on July 19th, 1966, shortly a f t e r the air-bubblers had e f f e c t i v e l y ceased operation. 96 The fieldsheets i l l u s t r a t e a gradual decrease i n water depths over the e n t i r e project area during the freshet; however, the downstream part of the area c l e a r l y shows a much more pro- nounced trend to shoal than the upstream part. Three series of l o n g i t u d i n a l p r o f i l e s , p a r a l l e l to the wharf (alongside the wharf-face and at distances of 50 and 100 feet out from the wharf-face) show a s i m i l a r tend (appendix XIII) .. The necessary data for these p r o f i l e s were provided by the fieldsheets of the weekly soundings, taken by the "Sounder" during the freshet of 1966. To compare the river-bed configurations a f t e r freshets i n previous years, s i m i l a r l o n g i t u d i n a l prof l i e s were p l o t t e d f or the post-freshet, pre-dredging hydrographic surveys of the approaches to the wharf i n the years 1957-1965. They show almost consistent ly a shoal area at the down-stream part of the wharf and a r e l a t i v e  ly deep area near the upstream end of the wharf, probably caused by scour as a r e s u l t of a crowding of the streamlines near this up stream end. A. convincing example of how much the bubblers as an a n t i - shoaling device depend on a strong h o r i z o n t a l flow, can be found at mark 6 + 0 0 of the wharf, where the fourth bubbler was placed. Along the l i n e of the bubbler hose, there was no sign of a trench scoured out of the river-bed, or any increase i n depth which might have suggested some l o c a l deepening due to the bubbler. This p a r t i c u l a r bubbler, although occasionally covered by a grain ship, had been operating quite strongly and the l o c a t i o n had been 97 specially selected to observe the effect of an individual bubbler on the surrounding sand bed, and also to keep i n suspension sediment agitated at the upstream end of the wharf. However, the flow conditions at this part of the wharf were very poor (low v e l o c i t i e s and back eddies) and the soundings indicated quite c l e a r l y the importance of having a strong horizontal flow, with out which the bubblers would f a i l as shoal-inhibiters. No d e f i n i t e conclusions were drawn from the soundings taken by the "Port Fraser". Her sounding l i n e s , although run with great diligence and s k i l l , did not follow control survey l i n e s , whereas the p a r a l l e l sounding lines perpendicular to the wharf run by the "Sounder" were controlled by ranges established on the wharf by survey measurements. Furthermore, distances out from the wharf were accurately measured by stretch-line and sextant angles. However,:the sounding graphs from the "Port Fraser's" echosounder were very useful i n following the progress of the shoaling and were retained for possible future reference. IV-6 Shipping at the Fraser-Surrey Wharf During Freshets On the base of records provided by the B.C. Pilotage Author i t i e s at New Westminster, a s t a t i s t i c a l study was made of ship's a c t i v i t i e s at the wharf, during freshets from 1957 to 1966. The results are presented as a histogram (fig.34), which shows on the horizontal axis the freshet durations and on the v e r t i c a l axis the number of days per freshet ( i n percent) when the wharf was partly 98 or wholly occupied by ships. As a reference for the duration of a freshet, the Fraser River discharge at Hope of at least 150,000 cfs had been chosen (see IV-3). Vessels with draughts of l e s s than ten feet were not considered; t h e i r draughts generally varied between 15 and 25 feet. The histogram clearly, i l l u s t r a t e s that the freshet period of 1966 has been more, favourable to. shipping at the wharf than any of the previous freshet periods. The wharf was occupied by one or two vessels 41% of the duration of the freshet, a s l i g h t l y lower percentage than i n 1963; however, the freshet i n 1966 lasted much longer than i n 1963. Of the freshets considered, these two distinguished themselves by the lowest maximum d a i l y discharges at Hope; the peak discharge i n . 1.963 was 272,000 cfs (June 16); the peak discharge i n 1966 was 281,000 c f s . (June 15). This remarkable agreement not only i n peak discharges, but also i n the dates that they were registered, would tempt one to i n f e r that low freshets create favourable conditions, at the wharf: f o r shipping, perhaps even a decrease i n shoaling. Unfortunately, the 1964 freshet with a peak discharge at Hope of 408,000 cfs (June 21),. the highest.in ten years, showed a decrease i n shipping at the wharf of only 7%, compared to 1963. Of course, the number of days that a wharf i s occupied by ships Is not necessarily the r e s u l t of i t s a c c e s s i b i l i t y . There are also economical and p o l i t i c a l f a c t o r s . 99 SECTION V . Discussion of Results This project covered such widely varied topics i n the laboratory and f i e l d that i t was not always possible to go into each p a r t i c u l a r aspect as thoroughly as desired, with the time and equipment a v a i l a b l e . However, in. s p i t e of l i m i t a t i o n s , and set-backs encountered during the research, the information gathered and experience gained should be of value to future research of- a s i m i l a r nature. The most important observations w i l l be b r i e f l y discussed i n the following summary. Vel o c i t y measurements made with a miniature current meter i n the laboratory flume f i l l e d with four feet of s t i l l water, showed that a screen of r i s i n g bubbles emerging from a perforated, one-inch diameter bubble hose, placed on the bed of the flume, was capable of inducing a v e r t i c a l flow i n the surrounding water which was s u f f i c i e n t l y strong, to l i f t f i n e sand from a point about 1.0 inch above the top of the bubble hose to the water sur face, provided that: a) s u f f i c i e n t a i r was supplied to the bubbler (a minimum of 0,0025 pounds of a i r per second per foot of bubbler hose); b) the spacing between the o r i f i c e s was s u f f i c i e n t l y small (a spacing of l / ' i inch appeared to be the most s a t i s f a c t o r y one); c) the diameter of the a i r holes was small enough to enable the compressor to provide a l l a i r holes with a strong flow of a i r without exceeding i t s capacity. The term " f i n e sand" applies to a grain s i z e smaller than 100 0,2 mm, according to the U.S. Bureau of Standard Sieve Series. It was shown a n a l y t i c a l l y (II-2) that the potential energy of the bubbles, which i s converted into k i n e t i c energy of the surrounding water, increases with the water depth above the bubbler and with the volume of a i r supplied to the bubbler. A sieve analysis of the bed material found In front of the Fraser-Surrey Wharf indicated that 90% of this bed material consists of fine sand (IV-3). Therefore, an air-bubbler, s i m i l a r In design to the one employed i n the laboratory tests should be able to l i f t to the r i v e r surface both bed load and suspended sediment (being l i g h t e r than bed material, see section IV-3), found i n front, of the Fraser- Surrey Wharf. In conjunction with a strong r i v e r current, s u f f i c i e n t l y fast to carry this agitated sediment past the wharf, several bubble hoses placed i n the river-bed perpendicular to the river-flow and of s u f f i c i e n t length, should a p r i o r i be able to prevent sedimentation i n the approaches to the wharf. However, although being a necessary condition to the success of a bubbler as a shoa l - i n h i b i t e r , the superposition of a h o r i  zontal flow has also an adverse effect upon the bubbler's operation. The laboratory tests (see f i g . 12) showed that the maximum upward v e l o c i t i e s induced by bubbles i n s t i l l water were confined to a very narrow zone, v e r t i c a l l y above the bubbler. Outside of this zone, there was a sharp drop i n the upward v e l o c i t i e s induced i n the water, p a r t i c u l a r l y on a horizontal plane about one inch 101 above the bubbler hose, where a strong upward flow i n the water i s most needed to contend with bed-and s a l t a t i n g load. Once a r e l a t i v e l y large p a r t i c l e escapes from this zone of maximum up ward v e l o c i t i e s , i t w i l l almost immediately enter a region where the upward v e l o c i t i e s i n the water are unable to support i t any longer, and the p a r t i c l e w i l l sink back to the bed. Turbulence, which i s always present i n river-flow, would force a large number of sand p a r t i c l e s out of the narrow v e r t i c a l zone. An e n t i r e l y d i f f e r e n t , but more obvious effect of the horizontal flow i n a r i v e r would be the dispersionof the bubbles with a consequent loss i n energy and hence decrease i n upward water v e l o c i t i e s ( I I - l ) . Therefore, the laboratory experiments performed i n s t i l l water, v although very encouraging, are bound to exaggerate the e f f e c t i v e  ness of an air-bubbler i n the prevention of shoaling. Consequent ly the design of a prototype bubbler, i f based on laboratory tests i n s t i l l water, should include an ample safety factor i n the a i r supply to the prototype bubbler. In the laboratory flume available for the bubbler t e s t s , i t was not possible to superimpose upon the bubble screen a horizontal flow .large enough to simulate r i v e r conditions ( I I I - l ) . Conse quently, the imposition of a f a i r l y deep flow on a screen of r i s i n g bubbles would be a worth-while project for future research on bubblers for preventing shoal. To observe the water, c i r c u l a t i o n , induced by r i s i n g air-bubbles, a large flume would be almost essential. Bulson''' used a graving dock with a width of 106 feet and a depth of 36 feet above the keel blocks. The cross sectional area of this dock would 102 require an exorbitantly high discharge to simulate river-flow (Bulson, who concentrated on pneumatic breakwaters, was not interested in introducing a horizontal flow). However, a reason able site for a large flume, where, at the same time, sufficiently high horizontal velocities could be created, might be found near a river in British Columbia. The existing Robertson Creek test flume on Vancouver Island (15 feet deep), operated by the Federal Department of Fisheries, appears quite suitable for such tests. Although the field tests at the wharf suffered some unexpected set-backs, they provided valuable experience. For example, the apparently simple procedure of placing the bubble hoses on the river-bed In a strong river current, required careful planning. The success of the operation showed.how important i t was to have the assistance of a powerful, well equipped vessel with skilled personnel. Much less satisfactory than the installation of the bubblers, was the operation of the compressors to supply air to the bubblers. It would be advisable in future operations to have the presence of a technician continuously, or preferably, a standby compressor. Instead of relying entirely on an rpm indicator on the compressor (from which the rate of flow of air could be estimated from performance curves and calibration tables), an air. flow meter would be more accurate and positive. The presence of ships at the wharf (IV-4) was detrimental to the operation of the bubblers; on the other hand, the function of the bubblers was to keep the wharf open, for shipping. The only 103 solution i s to i n s t a l the bubblers upstream of the wharf and i n locations just outside of the normal berth of a ship, i f possible. A bubbler location downstream of the stern of a ship should be avoided i n view of the dead-water area caused by the ship's h u l l (assuming that the ship's bow faces into the r i v e r current). Inspection of the longitudinal p r o f i l e s of the r i v e r bed p a r a l l e l to the wharf, at distances of 100, 50 and 0 feet out from the wharf-face (Appendices XIII and XIV), plotted from the 1966 weekly freshet soundings as wel l as from a 10-year record of post- freshet, pre-dredging soundings, shows that the downstream half of the Fraser-Surrey Wharf i s more susceptible to shoaling than the upstream h a l f . There i s a consistent depression i n the river-bed near the upstream end of the wharf, probably caused by scour as a result of the contraction of the river-flow just outside the up stream end of the wharf. Furthermore, the current measurements during the freshet of 1966 show a marked decrease i n r i v e r v e l o c i t i e s (surface as w e l l as sub-surface) i n the downstream part of the immediate approaches to the wharf. This retardation of flow, (due to causes mentioned i n Section IV-2). would naturally contribute to shoaling. However, the i n s t a l l a t i o n of bubblers near the downstream part of the wharf would not be advisable due to the lack of horizontal flow to carry the agitated sediment past the wharf and out of the project area. This was demonstrated by placing the bubbler on the river-bed at mark 6 + 0 0 and also by blowing large quantities of a i r into the sand-bed at mark 8 + 0 0 with a v e r t i c a l pipe connected to the small compressor, i n attempts 104 to remove a l o c a l hump. This l o c a l shoal hump was reduced i n height but a new shoal was created i n the immediate v i c i n i t y because of the absence of a horizontal flow to carry the agitated sediment downstream. The three bubblers at the upstream end, however, did have the support of a strong horizontal flow and there i s reason to believe that the i r presence diverted part of the sediment, which otherwise would have been deposited near the downstream end of the wharf. I t should be pointed out that the Federal Department of Public Works dredged a "sediment trap" (see f i g . 16) upstream from the wharf following the 1965 freshet, which trapped about 100,000 cubic yards of sediment during the 1966 freshet. This "sediment trap", i n conjunction with the bubblers and a rather small freshet may a l l have contributed to the r e l a t i v e l y favourable shoaling conditions at the wharf during the summer of 1966 with the conse quent increase i n shipping over s i m i l a r periods i n preceedlng years. Although i t i s very doubtful that air-bubblers of any design could a l l e v i a t e shoaling, at the downstream part of the wharf, i n view of the low r i v e r v e l o c i t i e s there, i t would have been-worth while to continue tests with bubblers at the upstream part of the wharf In future by varying the design of the bubblers and studying the effect of freshest upon the shoaling. Unfortunately, however, this w i l l not be possible. In the f a l l of 1966, plans were approved to b u i l d a river - c o n t r o l structure i n front of the Fraser- Surrey Wharf, consisting of a p i l e dike 950 feet long and a p i l e dike 330 feet long connecting i t with the upstream end of the 105 Fraser-Surrey Wharf. This structure, which was .completed i n the winter of 1966-67, i s one of the control structures proposed by the Fraser River Model Project at the University of B r i t i s h Columbia 19 i n 1959 , to minimize dredging maintenance i n the Trifurcation Area and at the same time increase the navigation channel widths and depths. The Fraser River Model had showed that this structure was needed to keep i n motion the bed material moved downstream by the action of the training structures further upstream. The structure creates a sheltered basin at the wharf, which cannot be entered by bed material brought downstream because of closed p i l i n g below water, which enclosed the wharf approaches on the river-ward and upstream sides. However, the upper portion near the surface consists of open p i l i n g to produce flushing action and i t i s possible that the i n s t a l l a t i o n of one or more air-bubblers i n this basin would be instrumental i n preventing suspended sediment from s e t t l i n g . At any rate, further large-scale fieId-tests with air-bubblers on the Fraser River estuary should be conducted elsewhere i n the future. 106 SECTION VII CONCLUSION General. Without a strong horizontal r i v e r current to carry  the agitated sediment outside of the project area, the air-bubbler  cannot prevent shoaling. Preliminary Studies. Before deciding i f the I n s t a l l a t i o n of a system of air-bubblers i n a shoal area i s warranted as a shoal- prevent at ive measure, f i e l d studies should be carried out during the period when •s^oallnJ^cturB : ; ;-TneiBe:;:8tudies would include soundings (to follow the pattern of shoaling); current velocity measurements; f l o a t studies (to determine flow patterns) and sedi ment sampling and analysis. The current velocity measurements should cover the entire project area, but should concentrate p a r t i c  u l a r l y on that part where shoaling appears to be most severe and where the flow conditions are most adverse (see page 67). I f ade quate equipment for current measurements i s not available, a simple f l o a t survey as outlined i n IV-2 would give a good approximation to v e l o c i t i e s . However, sub-surface ve l o c i t y measurements (preferably with a d i r e c t i o n a l current meter) would be desirable i n t i d a l estuaries i f a reversal of flow i s suspected at flood tides. I f no up-to-date samplers are available for measuring suspended sediment, or bed load, a sieve analysis of the bed material which i s e a s i l y obtained with a drag-bucket type of bed-material sampler, would be quite i n order since bed-load and bed-material have almost i d e n t i c a l grain-size d i s t r i b u t i o n curves (see figures 31 and 32) 107 and suspended sediment Is generally fin e r than bed load and more easi l y kept In suspension by agitation. I f the results of these field-surveys ( i . e . soundings, velocity measurements, flow patterns, and sediment analysis) together with an examination of the "Chart for determining largest grain sizes to reach deposit area" (Appendix IX) indicated that the i n s t a l l a t i o n of air-bubblers i s j u s t i f i e d , then the proposed design of the bubblers i s as follows. Suggestions.for design and operation of air-bubblers. DIMENSIONS AND MATERIAL: One-inch I.D. polyethylene hose, which i s f a i r l y cheap, non-corrosive, l i g h t and easy to d r i l l . The length of each air-bubbler should be equal to the width of the project area (since the bubblers w i l l be placed i n a direction perpendicular to the-river flow). v:1 ORIFICE DIAMETER AND SPACING. The diameter of the a i r holes should be small, preferably 0.0135 inches; with a close spacing of 1/4 inch. This produces a dense screen of r i s i n g air-bubbles for a given , compressor capacity. For d e t a i l s , see page 81. This diameter and spacing may seem very small compared to other air-bubblers described i n the l i t e r a t u r e . However, i t should be emphasized that most of these other bubbler designs were aimed at creating a strong horizontal flow near the surface, or a strong v e r t i c a l flow, without the p a r t i c  ular need for a strong upward flow i n the bottom layers of the sur rounding water, close to the bed and near a bubbler hose. In the case of a shoal i n h i b i t e r , the effect of the air-bubbles on the bottom layers of the water i n producing an upward flow i s very 108 Important and the laboratory experiments have shown quite cl e a r l y that a close spacing of the a i r holes with a correspondingly small  diameter ( i n view of the limited capacity of an a i r compressor) are preferable to a large spacing and large o r i f i c e diameters (see also figures 13-15). AIR PRESSURE: The a i r pressure at the r i v e r ward end of the bubbler hose should be w e l l above hydrostatic pressure (twice the hydrostatic pressure i s suggested). A i r pressure and rate of a i r flow are i n t e r  dependent but a pressure w e l l above hydrostatic pressure would prevent p a r t i a l f i l l i n g of the hose with water due to possible pressure fluctuations. For calculations of pressure drop i n a polyethylene hose, Stehr's equation on page 92 could be used (determining 6 em p i r i c a l l y ) ; the pressure drop i n the perforated part of the hose i ( i . e . the part which serves as the actual air-bubbler) should be taken as 1/3 of the pressure drop i n an equal length of unperforated hose under sim i l a r conditions. The results., allowing also for pressure lossses i n connections, etc. (say 10%) would determine the minimum required pressure at the compressor. This could be checked by i n s t a l l i n g a pressure gauge at the outer end of the hose, with the compressor operating and before the bubbler was lowered into the water. RATE OF FLOW OF AIR: I t was found that one cubic foot of a i r per minute,per foot length of bubbbler hose, at the prevailing hydro s t a t i c pressure was adequate. When the bubbler i s placed i n 30 feet of water, this would mean 2 cfm of free (atm. pressure) a i r . COMPRESSOR CAPACITY would be defined by the rate of flow of a i r required 109 and the t o t a l length of perforated (bubbler) hose, e.g. 200 feet of bubbler hose In 30 feet of water would require a compressor capacity of approximately 400 cfm. INSTALLATION OF BUBBLER HOSES. A recommended procedure f o r i n s t a l l a t i o n i s described on page 84, see also plate 4. I n s t a l l a t i o n from a boat p u l l i n g away from the wharf i s not recommended, since the movement of the boat cannot be c o n t r o l l e d accurately enough i n a r i v e r current to prevent breaking or kinking the hose. OPERATION, The presence of a standby compressor would be desirable, to guarantee continuous operation. A technician should be at hand at a l l times and an a i r flow meter should be a v a i l a b l e . For some ad d i t i o n a l p r a c t i c a l d e t a i l s regarding the bubbler hoses, vide page 90, NUMBER OF HOSES, I t was shown ( r e f . Section V) that the maximum upward water v e l o c i t i e s induced by the bubbles, are confined i n a very narrow v e r t i c a l zone above the bubbler hose, p a r t i c u l a r l y near the river-bed," providing a r e l a t i v e l y weak b a r r i e r against bed load and s a l t a t i o n load. A much more e f f e c t i v e b a r r i e r or screen against these sediment fract i o n s would be obtained by three p a r a l l e l a i r - bubbler hosesj spaced about one foot apart. Comparison with other applications of,air-bubblers. Of a l l the possible p r a c t i c a l applications (see also Section I) of the property of r i s i n g air-bubbles to create a c i r c u l a t i o n i n the surrounding water, the shoal i n h i b i t e r appears to be the least e f f i c i e n t , because: A) The upward flow induced i n the water by the r i s i n g bubbles 110 Is weakest where i t Is most needed: v i z . near the r i v e r bed. B) The h o r i z o n t a l flow In the r i v e r , without which the bubblers would not operate as s h o a l - i n h i b i t e r s , has also an adverse e f f e c t upon the magnitude of the v e r t i c a l v e l o c i t i e s i n the water induced by the air-bubbles. Although a strong h o r i z o n t a l flow would be most b e n e f i c i a l to the bubbler's operation i n carrying the agitated sediment out of the project area, i t would require large quantities of a i r to overcome the reduction i n upward water v e l o c i t i e s due to the s c a t t e r i n g and d i s p e r s a l of the a i r bubbles. The Fraser-Surrey Wharf. Although much valuable experience was gained during the f i e l d tests at the Fraser-Surrey Wharf, i t must be recognized that a c l e a r appraisal of an air-bubbler as a s h o a l - i n b i b i t e r was severely hampered by a number of f a c t o r s , including the presence of ships, the flow conditions i n the approaches to the wharf, and the unsatis factory performance of the compressors. However, due to the un favourable r i v e r . f l o w conditions near the downstream end of the wharf, i t i s very doubtful that air-bubblers would have a l l e v i a t e d shoaling  at t h i s wharf to such an extent as to warrant t h e i r permanent i n s t a l l a   t i o n there. Suggestions for Further Research Detailed studies are necessary to determine how a h o r i z o n t a l flow can e f f e c t the e f f i c i e n c y of a screen of r i s i n g a i r bubbles i n pre venting shoal, A large experimental flume (with a width of 5 feet or more and a depth of about 10 feet would permit detailed observations of v e r t i c a l d i s t r i b u t i o n s of v e l o c i t y and would eliminate w a l l e f f e c t s . i l l Such a flume should also be capable of producing h o r i z o n t a l v e l o c i t i e s comparable to those occurring i n the prototype when shoaling occurs. The large outdoor te s t flume b u i l t by the Department of Fi s h e r i e s at Robertson Creek on Vancouver Island, might conceivably serve t h i s purpose, 112 BIBLIOGRAPHY 1. E» S. Pretious and E. Vollmer, " H i s t o r i c a l Review of River Training and i t s Effects i n the New Westminster Area, Fraser River, B.C., March 1960. FRM 233. 2. E. J . Lesleighter, "Saltwater Intrusions and the use of Pneumatic and Similar Barriers i n New Castle Harbour". N.S.W. Dept. of Public Works, Manly Vale, A u s t r a l i a . 3. "Delta werken", Augustus 1966. 's Gravenhage (in Dutch). 4. E. Stehr, "Berechnungs grundlagen f l i r P r e s z l u f t " . dlsperren, Franzius I n s t l t u t , Hannover ( i n German). 5. F. Peebles, "Chem. Eng. Progress", February 1953. 6. B. Rosenberg, "U.S. Navy Department Report 727" (1950). 7o W„ Haberman, R. Morton, "U.S. Navy Department Report 802" (1953). 8. F„ Ho Garner, "Diffusion Mechanism i n the Mixing of Flu i d s " , Trans. Inst, of Chem. Eng. (G,B.), 1950, V.28. 9. A, Gorodetskaya, "The Rate of Rise of Bubbles i n Water and Aqueous Solutions", Phys. Chem. (U.S.S.R), 1949, V.23. 10. B, Stuke, "Das Verhalten der Oberflache von sich i n FlUssig- keiten bewegenden Gasblasen", Natur wissenschaften, 1952, Vol, 39 (In German), 11, W, Hensen, "Model Versuche mit pneumatischen Wellenbrechern", Franzius I n s t i t u t , Hannover (German), 12, G. Taylor, "The Action of a Surface Current used as a Break water", Proc. Roy. Soc. A. Vol. 231, 1955, p. 466. 13. W. Schmitt and E. S. Pretious, "The Precise Measurements of Small Water-Surface Slopes i n Open Channels", the University of B.C., Vancouver, 1966, 14. H. Rouse, "Engineering Hydraulics". 15. E, So Pretious, "Bed Load Movement i n the Main Arm of the Fraser River Estuary", FRM 224, 1956. 16, "Brochure #76, Armstrong Whitworth Equipment", Hucclecote, Gloucester, England, 17, P, S, Bulson, "Currents Produced by an A i r Curtain i n Deep Water", Dock and Harbour Authority, May 1961. BIBLIOGRAPHY (Continued) 113 18. W. Parkinson, "1955 Prototype Studies of the Lower Fraser River", FRM 220, 1955. 19. E. S. Pretious and E. Vollmer, "Final Report on Plans for Reduction of Shoaling and for Improvement of the Fraser River at New Westminster, B.C.", plus "Revision and Addendum", FRM 232, 1959. APPENDIX I PNEUMATIC BREAKWATERS gA 2TTh Velocity of Surface Waves; C 2 - / j ^ r ..tanh ~^ , where c = celerity of waves; h = s t i l l water depth and A = wave length. 2 rr h For h y (deep water wave): tanh — ^ — —>- 1. gA ° 2 " IT? • O R C " \| 2TT gA, If waves are met by an opposing current with velocity v, c^ = , where c^ is the absolute celerity, = c - v. Therefore, since c ^ > c-^ , X^>A, . When a surface wave in deep water meets an opposing current, both its celerity and wave length decrease. ' Rate of Transmission of Wave Energy = 4 TT h 4 "TT h = k g ^  a 2c ( 1 + — c o s e c h — — ), where a = amplitude. A is shorter in an opposing current than in s t i l l water. 4 TT h 4 TT h Consider the term ( 1 + — — cosech - y — ) , or y = 1 + x cosech(x) <^x always p o s i t i v e ^ . dy _ _ - -x cosech(x) coth(x) + cosech(x) - dx = ( 1 - x coth(x) ) cosech(x), where cosech(x) always positive for x >^ o Consider the term ( 1 - x coth(x) ): x coth(x) is always^> 1 for a l l positive x values. dy . . 1 - x coth x is negative for a l l positive x values; , \ ~ <^o. 4 TT h 4 TT h The term ( 1 + cosech ) decreases with decreasing A. Therefore, assuming deep water waves and no d i s s i p a t i o n of energy i n the t r a n s i t i o n from s t i l l water to opposing current: X decreases ) . . . a must increase, c decreases ; APPENDIX II Average v e l o c i t i e s of bubbles emerging from 1' bubbler i n flume, under varying pressures. 0.25 ( Pi ) 0.40 Empirical Equation: W = 6.6 A Q ( ^ ( P ° ) where A Q = cross, area o r i f i c e i n square inches; Pj^ = absolute pressure inside bubbles P q = absolute pressure outside bubblejs (both P,. and P i n psia) 1 o W = upward v e l o c i t y of bubbles i n f t . / s e c . :Water depth i n flume = 4 feet. ( O r i f i c e diameter = 0.036", A Q = 10.2 x 10 4 ) P 0 = 16.4 p i < p i / > ° " 4 w w ( P Q ) c a l c obs error (%) ( ) 49 3.00 1.83 1.78 3 30 1.84 1.50 1.54 3 26 1.59 1.42 1.48 4 24 1.46 1.40 1.43 2 20 1.22 1.28 1.29 1 ( O r i f i c e diameter = 0.026", A Q = 5.3 x 10~ 4 ). 59 1.67 1.67 1.66 1 40 1.43 1.43 1.48 3 32 1.31 1.31 1.33 2 29 1.26 1.26 1.29 2 22 1.12 1.12 1.14 2 -4 ( O r i f i c e diameter - 0.020", A„ = 3.1 x 10 ). 60 1.68 1.47 1.60 9 50 1.56 1.36 1.42 4 45 1.50 1.31 1.38 5 31 1.29 1.13 1.25 10 26 1.20 1.05 1.18 12 APPENDIX III S e t t l i n g v e l o c i t i e s of Fraser River sand deposited i n front of Fraser-Surrey Wharf. Retained by Sieve Mean s e t t i n g time i n seconds, distance = 183 cm. mm 2.00 0.84 0.42 0.25 No. 10 '20 "40 ^60 8.4 14.7 33.6 47.6 78.1 0.074 200 92.7 PAN 141.3 Arrows denote the maximum s i z e found i n the following sieve; i . e . the s i : sieve. 0.147 100 0.105 140 s z e of p a r t i c l e s which have the maximum v g for that p a r t i c u l a r Theoretical * s e t t l i n g v e l o c i t i e s (cm/sec.) 16 9.3 5.6 3.2 1.5 0.8 0.4 S e t t l i n g v e l o c i t i e s found with PURI (cm/sec) 21.8 12.4 5.5 3.8 2.3 1.9 1.3 Dia (mm) p a r t i c l e s 2.00 0. 84 0.42 0.25 0.147 0.105 0.074 * Based on U.S. Bureau of Reclamation data. APPENDIX IV ORIFICE METER IN AIR S U P P L Y r Compressible flow, mass flow m - C Y A J ^ , 2 Af>' 0.0491 2 D0 = 0.25" A0 = 0.057 A„ = J_ _^ f t . — 144 A l ' f Assume J)^T P 2 y Expansion Factor Y = 1. A p = i ( i±Z ) = 0 .036 A U ( P * 0 12 (m<>\) 34 ° _ 0.0491 m - 144 J (144) (0.072)?, C = 10.98 x 10~ 4 c J ^ A h slugs/sec. (where \>{ i n s l u g s / f t j ZiK i n inches) n _ 144 ( P + 14.7) 3 vri ~ • a s l u g s / f t . (1715) (460+t) CALIBRATION DATA Airpressure at o r i f i c e meter(psi) P a 15 35 46 55 65 75 85 95 104 114 Manometer at o r i f i c e m. (inch water) 1 . 0 2 . 9 3 . 7 4 . 8 5 . 9 6 .8 7 .8 8 .8 9 . 8 1 0 . 8 Manometer at Gasom. (inch Mg) h m 1 . 0 0 1 .20 1 .10 1 .15 1 .25 1 .15 1 .30 1 .30 1 .25 1 .25 A i r v o l . i n Gasom, ( f t . 3 ) ¥ 1 .50 1 .59 1 .62 1 .70 1 .76 1 .54 1 .69 1 .61 1 .59 1 .66 A t sees 80 41 35 30 26 20 19 £ 17 15 14 E t op 50 48 48 48 48 48 48 47 47 47 A i r p r e s s u r e i n gasometer p = ( 1 3 . 6 ) ( 6 2 . 4 ) ( a 12 S p e c i f i c w e i g h t o f a i r Y + 2116 = 70 .72 h + 2116 p s f . m P a R Q T ( 5 3 . 4 ) ( 5 0 8 ) = ( 0 . 3 7 ) ( 1 0 )p A t o r i f i c e : P = 1 4 4 ( p a + 1 4 - 7 ) = ( 0 . 1 6 6 ) (10 3 ) P + 14 .7 ) ( 1 7 1 5 ) ( ° F + 4 6 0 ) a s l u g s / f t . W = V Y l b s / s e c . A t C a l c u l a t i o n s o f C i n m = (10 .98 ) (C) \|<^hw (10 ) , where m i n s l u g s / s e c . „ - (m) ( 1 0 4 ) • . C - ( i f m i n s l u g s / s e c . ) ( 1 0 . 9 8 ) 4 o r C = ( n ° , ( 1 ° } x Ji ( i f W i n l b s / s e c ) , 10 .98 ) U L 3 2 . 2 P + 14.7 a ? h w If 0 W C R psi S l u g s / f t 3 x 10 3 inch x 10 _ 1 l b s / f t 3 lbs/sec x 10 x 10" 3 30 4.96 1.0 0.71 0.081 1.52 0.61 1.90 50 8.30 2.9 1.56 0.082 3.18 0.58 3.98 61 10.01 3.7 1.92 0.081 3.75 0.555 4.29 70 11.60 4,8 2.35 0.081 4.60 0.555 5.76 80 13.26 5.9 2.80 0.082 5.54 0.56 6j93 90 14.96 6.8 3.19 0.081 6,24 0.56 7.80 100 16.60 7.8 3.60 0.082 7.10 0.56 8.80 110 18.32 8.8 4.00 0.082 7.76 0.55 8.70 119 19.78 9.8 4.40 0.082 8.68 0.56 10.84 129 21.45 10.8 4.80 0.082 9.38 0.56 11.76 Reynolds Number : R = V D <? = (4.03) 7  0 (10 ) m. /*-=(3.8X ' 0 " D = — F T - 12 APPENDIX V Sample Measurements with mini-flow current meter (Armstrong-Whitworth) of Upward Water V e l o c i t i e s induced by Bubbles i n Laboratory Flume. D-= Depth of Water, i n Feet. T = Temp, of Water, i n Centigrades. H = Height of Probe above Bed, i n Feet. P = Air pressure i n Bubbler, i n Psig. Pg = Air pressure at o r i f i c e meter i n psig. hg = Reading Water manometer at O r i f i c e meter i n inches, t = A i r temperature i n Centigrades. W = Weight flow of A i r in lbs/sec. V = : Upward Water v e l o c i t y i n Inch/second, TEST 1. Spacing O r i f i c e s \ inch. Diameter O r i f i c e s 0.020 inch Probe d i r e c t l y over bubbler. D T H P h g P g t g- o W 3 xlO V 4 8.5 3 22 1.1 62 8 1.7 15.3 4 8.5 3 11 0.2 62 8 1.0 14.8 4 8.5 3 31 1.9 62 8 2.3 17.7 4 8.5 3 40 2.5 76 8 2.8 18.2 4 8.5 3 50 3.1 91 8 3.3 18.7 4 8.5 2 10 0%1 93 8 0.9 12.2 4 8.5 2 20 0.5 93 8 1.4 14.4 4 8.5 2 30 1.3 93 8 1.8 15.5 4 8.5 2 40 2.0 92 8 2.3 16.8 4 8.5 2 50 2.9 91 8 3.2 19.2 4 8.5 1 10 0.1 93 8 0.9 12.2 4 8.5 1 20 0.4 93 8 1.4 12.5 4 8.5 1 30 1.1 92 8 1.8 13.9 4 8.5 1 40 2.0 92 8 2.3 15.3 4 8.5 1 50 3.0 91 8 3.2 17.5 D T H P h g P g t g W 3 xlO V 4 8 .5 0 .5 10 0 .1 91' 3 0 . 9 1 0 . 9 4 8.5 0 .5 20 0 .5 91 3 1 .4 1 2 . 9 4 8.5 0 .5 30 1 .2 91 3 1 .8 1 3 . 3 4 8 .5 0 .5 40 1 . 9 91 3 2 .3 15 .1 4 8.5 0 .5 50 2\i9 91 3 3 .2 15 .4 T E S T 2. Spacing \ inch Dia. 0 .020 inch Probe 1 ' to l e f t . 4 8.5 0 .5 10 0 . 1 93 3 0 . 9 rev. (reversed 4 8.5 0 .5 20 0 .5 93 3 1 .4 rev. flow) 4 8 .5 0 .5 30 1 . 0 92 3 1 .6 rev. 4 8.5 0 .5 40 2 . 0 91 3 2 .3 rev. 4 8.5 0 .5 50 2 . 8 91 3 3 . 2 rev. 4 8.5 1 10 0 . 1 93 3 0 . 9 rev. 4 8.5 1 20 0 .5 93 3 1 .4 rev. 4 8 .5 1 30 1 . 0 92 3 1 .6 rev. 4 8 .5 1 40 2 . 0 91 3 2 .3 rev. 4 8 .5 1 50 2 . 8 91 3 3 . 2 rev. 4 8.5 2 10 0 . 1 93 3 0 . 9 • 1 .5 4 8.5 2 20 0 .5 93 3 1 .4 2 .2 4 8.5 2 30 1 . 0 92 3 1 .6 2 .4 4 8.5 2 40 2 . 0 91 3 2 .3 2 .6 4 8.5 2 50 2 . 8 91 3 3 . 2 2 . 7 4 8 .5 3 10 0 . 1 93 3 0 . 9 3 .8 4 8.5 3 20 0 .5 93 3 1 .4 3 .5 4 . 8 .5 3 30 1 . 0 92 3 1 .6 3 . 9 4 8.5 3 40 2 , 0 91 3 2 .3 3 .8 4 8.5 3 50 2 . 8 91 3 3 . 2 4 . 3 T E S T 3. S p a c i n g \ i n c h D i a . D T H P h g 4 8 .0 1 10 0 .1 4 8 .0 1 20 0 .5 4 8 .0 1 30 1 .1 4 8 .0 1 40 1 . 9 4 8 .0 1 50 2 . 8 4 9 .0 0 .5 10 0 . 1 4 9 .0 0 .5 20 0 .5 4 9 . 0 0 .5 30 1 . 0 4 9 .0 0 .5 40 1 . 8 4 9 . 0 0 .5 50 2 . 8 4 9 . 0 2 10 0 . 1 4 9 .0 2 20 0 .5 4 9 .0 2 30 1 . 0 4 9 . 0 2 40 1 . 8 4 9 .0 2 50 2 . 8 4 9 .0 3 10 0 . 1 4 9 . 0 3 20 0 .5 4 9 .0 3 30 1 . 0 4 9 . 0 3 40 1 . 8 4 9 .0 3 50 2 . 8 T E S T 4 . S p a c i n g \ i n c h D i a 4 8 .5 2 10 0 . 1 4 8.5 2 20 0 .5 4 8.5 2 30 1 . 0 4 8.5 2 40 1 . 8 4 8.5 2 50 2 . 8 020 i n c h P r o b e §• t o l e f t . P t a w V g g xlO"* 93 9 .0 0 . 9 0 . 8 93 9 .0 1 .4 1 .4 92 9 .0 1 . 8 1 .5 91 9 .0 2 .3 1 . 7 91 9 .0 3 . 2 2 .2 93 9 .0 0 . 9 0 . 1 93 9 .0 1 .4 0 . 6 92 9 .0 1 .8 0 . 8 91 9 .0 2 .3 0 . 8 91 9 .0 3 .2 0 . 8 93 8 .0 0 . 9 2 .3 93 8 .0 1 .4 3 . 2 92 8 .0 1 . 8 3 . 7 91 8 .0 2 .3 3 .8 91 8 .0 3 . 2 3 . 9 93 7 .0 0 . 9 4 . 9 93 7 .0 1 .4 5 . 6 92 7 .0 1 . 8 6 .7 91 7 .0 2 . 3 7 .3 91 7 .0 3 . 2 8 .3 020 i n c h P r o b e 2' t o l e f t . 93 3 .0 0 . 9 0 . 2 93 3 . 0 1 .4 0 . 6 92 3 . 0 1 .6 0 . 8 91 3 . 0 2 .2 0 . 8 91 3 . 0 3 .2 1 . 2 D T H P h P t W V g g g xlO 4 8.5 3 10 0.1 93 3 0.9 2.7 4 8.5 3 20 0.5 93 3 1.4 2.8 4 8.5 3 30 1.0 92 3 1.6 3.2 4 8.5 3 40 1.8 91 3 2.2 3.7 4 8.5 3 50 2.8 91 3 3.2 3.7 TEST 5. Spacing \ inch Dia. 0.020 inch Probe 3' to l e f t . 4 8.5 3 10 0.1 93 4 0.9 1.4 4 8.5 3 20 0.5 93 4 1.4 1.4 4 8.5 3 30 1.0 92 4 1.6 1.8 4 8.5 3 40 1.8 ei 4 2.2 2.5 4 8.5 3 50 2.8 91 4 3.2 2.7 4 8.5 2 10 0.1 93 4 0.9 0.8 4 8.5 2 20 0.5 93 4 1.4 1.0 4 8.5 2 30 1.0 92 4 1.6 1.1 4 8.5 2 40 1.8 91 4 2.2 1.7 4 8.5 2 50 2.8 91 4 3.2 1.7 TEST 16. Spacing 6 inch Dia. 1/16" Probe d i r e c t l y i above ( o r i f i c e of bubbler. 4 8 0.2 10 0.1 97 8 0.9 1.0 4 8 0.2 20 0.9 97 8 1.5 1.6 4 8 0.2 30 1.9 96 8 2.3 1.8 4 8 0.2 40 3.0 96 8 3.2 2.3 4 8 0.2 50 4.4 95 8 4.3 2,5 4 8 0.4 10 0.1 97 8 0.9 3.5 4 8 0.4 20 0.9 97 8 1.5 3.5 4 8 0.4 30 1.9 96 8 2.3 3.8 4 8 0.4 40 3.0 96 8 3.2 4.6 4 8 0.4 50 4.4 95 8 4.3 5.9 w , x l O ^ 4 8 0 . 6 10 0 . 1 97 8 0 . 9 9 .7 4 8 0 . 6 20 0 . 9 97 8 1.5 6 .3 4 8 0 .6 30 1 .9 96 8 2 .3 9 . 3 4 8 0 .6 40 3 . 0 96 8 3 . 2 8 ,2 4 8 0 . 6 50 4 . 4 95 8 4 . 3 8 . 9 4 8 0 . 8 10 0 . 1 97 8 0 . 9 9 . 1 4 8 0 . 8 20 0 , 9 97 8 1 .5 9 . 1 4 8 0 . 8 30 1 .9 96 8 2 .3 1 0 . 7 4 8 0 . 8 40 3 . 0 96 8 3 .2 10 .4 4 8 0 . 8 50 4 . 4 95 8 4 . 3 1 0 . 7 4 8 1 .0 10 0 . 1 97 8 0 . 9 9 .6 4 8 1 .0 20 0 . 9 97 8 1.5 4 8 1 .0 30 1 .9 96 8 2 .3 1 1 . 8 4 8 1 .0 40 3 . 0 96 8 3 .2 12. 8 4 8 1 .0 50 4 . 4 95 8 4 . 3 1 2 . 9 TEST 17. S p a c i n g 6 i n c h D i a . 1/16" P r o b e d i r e c t l y o v e r b u b b l e r , b u t midway between o r i f i c e s . 4 8 0 . 2 10 0 . 1 98 8 0 . 9 0 . 3 4 8 0 . 2 20 0 , 9 97 8 1.5 0 . 9 4 8 0 . 2 30 1 .9 97 8 2 .3 1 .0 4 8 0 . 2 40 3 . 0 96 8 3 . 2 1 .1 4 8 0 . 2 50 4 . 4 95 8 4 . 3 1.4 4 8 0 . 4 10 0 . 1 97 8 0 . 9 0 . 8 4 8 0 . 4 20 0 . 9 97 8 1.5 1 .0 4 8 0 . 4 30 1 .9 97 8 2 .3 1 .2 4 8 0 . 4 40 3 . 0 96 8 3 . 2 1 .5 4 8 0 . 4 50 4 . 4 95 8 4 . 3 1.6 0 T H P h g P g t g W 3 x l O V 4 8 0 . 6 10 0 . 1 98 8 0 . 9 0 . 7 4 8 0 . 6 20 0 . 9 97 8 1 .5 1 .3 4 8 0 . 6 30 1 . 9 97 8 2 . 3 1 .4 4 8 0 . 6 40 3 . 0 96 8 3 .2 1 .5 4 8 0 . 6 50 4 . 4 95 8 4 . 3 1 .3 4 8 0 . 8 10 0 . 1 98 8 0 . 9 0 . 8 4 8 0 . 8 20 0 . 9 97 8 1.5 1 .4 4 8 0 . 8 30 1 . 9 97 8 2 .3 1 . 9 4 8 0 . 8 40 3.0: 96 8 3 . 2 2 .1 4 8 0 . 8 50 4 . 4 95 8 4 . 3 2 . 3 4 8 1 . 0 10 0 . 1 98 8 0 . 9 1 .4 4 8 1 . 0 20 0 . 9 97 8 1 .5 1 . 8 4 8 1 .0 30 1 . 9 97 8 2 .3 2 .1 4 8 1 . 0 40 3 . 0 96 8 3 .2 2 .5 4 8 1 . 0 50 4 . 4 . 95 8 4 . 3 2 , 7 APPENDIX VI TAYLOR'S ANALOGY 1/3 W q = K(Vg) W q = max. v e l o c i t y of water In fps. V = volume of air/second/foot length of bubbler ( c f s / f t ) 2 g = acc. of gravity i n f t / s e c . Calculate V ( i . e . volume of a i r at the depth of the bubbler) P(4') 2116.3 + 4 x 62.4 n n e _ .,,.3 Y = RT = 53.4 x 510 = ° ' 0 8 7 l b s / f t • i n 4 f t of water. W • *•• V = » n o j , where W = weight flow of a i r i n lbs/sec. 49 o r i f i c e s per foot of bubbler, d i a o r i f i c e s 0.020", spacing 1/4". w lbs/sec x 10 3 V f t 3 / s e c x 10 2 (V 8) 1 / 3 WQ(exp.) f t / s e c K 1.0 1.15 0.72 1.24 1.72 1.7 1.95 0.86 1.28 1.48 2,3 2.63 0.95 1.48 1.53 2.8 3.22 1.01 1.52 1.51 3.3 3.80 1.06 1.56 1.48 0.9 1.04 0.69 1.02 1.48 1.4 1.61 0.80 1.20 1.50 1.8 2.07 0.87 1.29 1.48 2.3 2.65 0.95 1.40 1.48 3.2 3.68 1.05 1.60 1.52 Assume f i r s t reading w i l d (W = 1.0 x 10" 3) Coverage of a l l remaining nine values of K : 1.49 W q - 1.49 ( V g ) 1 / 3 . g 1 / 3 = 3.18 1/3 .'.Max. upw. v e l o c i t y of water W q = 4.74 V f t / s e c . New West tYUftl t e r M A X Vert Ucc-I Scale : I" a I P i of Wetted Misi id0=7 sl^C = \ l 3 * l x i s- " = 28 -T-t / A P P E N D I X "SIT. FIELD C A L C U L A T I Q M S - O P T'» b A L - C O i N T « 1 i i u f 1 o ivr "To A e L e v A f ibisr, O.1' f. O. o C; s 7 O o o o o o .0 o >!: I- I. ..V _-_ •,'<l <•• ; ••"4 *' i o[ o • j . .1 - - " : -i;if v i (Figure 188.) Chart for determining largest grain sizes to reach deposit area. APPENDIX IX APPENDIX X, Continued. Flow of a i r through Pipe l i n e (After Gibson) v ' ' -* v 1 r dead end X £ Pipe of constant diameter d. Flow decreases with length at constant rate due to l a t e r a l o f f-takes, each off-take taking same flow; equal spacing. Rate of decrease of flow = q c f s / f o o t . At P: flow = Q - qx. Loss of head up to P = ( h f ) x At P: (h,) , = ^ — dx, but since diameter i s constant ^ = ^ ~ ^ x f dx 2gd V Q • * * ^ V d x 2gd k Q ; * 2 (h f) • - — / X (Q - q x ) 2 dx E x 2gdQz 0 f V 2 r n2 _ 2 . 1 2 3 l - „ [Q x - Qqx + -rq x J] 2gdQ 2 Flow at downstream end of x i s Qx- Then Q = Q x + <lx» f r o m continuity. Substitution and s i m p l i f i c a t i o n gives: <?f>x - fi§Q2 C Q x 2 x + vx 2 + F x 3 ] At x = A, Q x = 0; Q = qx. CVi \ _ i c JL y__ (with l a t e r a l o f f t a k e s ) . ' ' 1 f V i r d• • 2g Note: loss of head only -j of loss of head f o r steady flow without any decrease i n flow along pipe due to l a t e r a l offtakes. APPENDIX X, Continued. Flow of a i r through Pipe l i n e (After Gibson) P l A *• • - * V 1 r X — • dead end Pipe of constant diameter d. Flow decreases with length at constant rate due to l a t e r a l off-takes, each,off-take taking same flow; equal spacing. Rate of decrease of flow = q cfs/foot. At P: flow = Q - qx. Loss of head up to P = ^ h f ^ x At P: (h,) , = dx, but since diameter i s constant 77 = ^ ~ ^ X f dx 2gd ' V Q ' fh \ = f.dx.V 2 ,Q-qx .2 2 (h ) - — • /* (Q -qx) 2 dx * X 2gdQ2 0 f V 2 rn2 _ 2 , 1 2 3 , = [Q x - Qqx + -rq x J] 2gdQ2 Flow at downstream end of x i s Q . Then Q =• Q + qx, from X X continuity. Substitution and s i m p l i f i c a t i o n gives: <N>*-!i3o? t Q x 2 x + v x 2 + hz*3] At x = A, Q x = 0; Q = qx. /•h \ o i f i -L. (with l a t e r a l offtakes). 0 - U f x = A 3 1 d * 2g Note: loss of head only -j of loss of head for steady flow without any decrease i n flow along pipe due to l a t e r a l offtakes. <:6- 26- a- Z7 75? 26. 2Jb. 17- zsr lS? 26- 27- 16- rj- 28- 31- 32? 16? 2A'. 27' 27- 25- 2# 14' 23? 14- Jtlf 26-* 25? 25? 14? I S ? 23? 24- 22. £X>' 23? 28- 2B? 13? 28- 17? 18' 26. 24. 24- is- is. 14- 14' 24. 22. —«- 19- 30? 29' 27- 25? 16- IS- 24? 24? 14? 22.- 28? 33? 30- 17- ZB' IS? 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ZS- 26. 16 26? 2*? 29. m 30. 10 ft+00 31 31 28- 29- 30- 31- 31- 31- 33- 32. 30. 28- 26. 25. 26. 27- 28- 29- 30- 31' 32- 33? Jl- 31. 30- 28? 27- APPENDIX XI N O ~ r £ s : Souna* 1 nys are in fe.eir referred rt? JL&cctl Low tyafer- CeveLj which is 6.° feet above Sctndheaxi's Pafvm. fak P U B L I C W O R K S O F C A N A D A F R A S E R R I V E R , B . C . A T N E W W E S T M I N S T E R F R A S E R S U R R E Y D O C K \ 5 0 U N D J Nl . S C A L E S AS N O T E D S H E E T f O F | S U R V E Y E D BYL£"f DRAVyN B Y ^ ^ ? DESIGNED BY * EXAMINED BY O T T A W A 196 A P P R O V E D 196 VERIFIED BY j^^J^r^*^ CERTIFIED C O R R E C T C ? 1 9 € ^ C H I E F E N G I N E E R P L A N N o . > ^ D I S T R » C T E N G I N E E R • MS ] ; 2S 2S 24* 22* 21- 21 2o-* 23s 22* 20 20- 2a 2J> 2o- 2<*> 20 21' 20 20- I91 20 19- 20 I9': 19' 2o- 19 21- 21- 20* 2o- 20* 21' 20 19- 19* 2,* 27: 26' 2f 29' 27 26- 2* 23- 2* 22 23- 24* 24- 24 23- 23- 22 •24-2S' 21* 22- 22* 23 22 23 22* 22' 22 23 21- 21 SU- 21* 22- 21-* 22 22 21* 21' 2J 21- 21* 22 2iS 21' 2J* 21' 2oS 22* 22 21- 21- 20 22 21' 22* it* 21- 22 20* 20- 22S 2J* 23* 24S 22' 2o 21- 19' 2o 20* 2h 20 20* 20* 21- 21* 2J* 22* 23 22* 22* 22* 22 '% JQ. *9- 20+ ?Q* 2o- 20-z 3 23 23 24 t23- 22' 22- 22" 23- 22- 22- 22- 21 20- 23- 23- 22* a* 22 Z3-* 23 22' 23' 22* 22- 22* 22- *** 21* 22- 22? 23-2?-24- 21 • 2oS =<* 22- 2Z 20^. 20- 22* 2o* 20. 22? 21. 28 2i 2*' 23- 22' 23 221 23' 22 22 21- 23- 23. 22. 21- 2A? 24* 23- 26? 2f* 27- 28- 27- 2*' 23- 22 22- 22 21' *? V s 20- 22. 21- 23- 21- 21' 20- 21 21- 21* 20- 19s 19 ** 20- 22. >9* 21- 2^ UL »7* t** S 6 F R A S E R - S U R R E Y 2f* & 2$- 2$> .2^ 24 22' 24" 26 27' 26J 2S. 22 23- 21' 22- 20 20' 20 19* 19-* /S IB- 2J »-* 2J* IB. /ft- If* DO CX /="R AS ER - ^ U R R.&Y &OCK SOU/VD/fvGS 26- 26- 23* 23* 24 2$' 24 23? 2LL 22 23- 23-* 24- 24 24* 2$ 25'' 2$ 2f- 26 23? 2$ 2$-* 30- 24. 24' 2* 24* 2 4 S 27* 2S. 26' &• 26 2$-- 2* 2* 2*. 2S- 26 27- 26 29.* 27 2f 2$. * 26* 27* 23* 27- 27- 27* 2d* 2$". 26- 27* 27* 27 2$' 27- 27- 2S- 2£- 2£ 26. 24- £2ei 2 ± 23J 22, 24* 27* 27- 27' 27* 27- 27- 27. 26 26* 26* 27. 2$. 27* J23A. 2 3 * 2^ 23- 2 3 * 23.* 22-* 2$- 26* 27> 27'* 27- 24 23. 26 27* 2S* 28- 25". 2$* 2f* 2S- 26 27* 2** 29- 10 28- 29- 27'" 2$. 28-* 29? 24j* 23,* Mr 23 2$- 27 29 29. 29' 29 32 28- 2* 2f. 2S- 27- 27'' 29- 30 3o 27- 29 3o 3o> 33* 33* M* 2J+ Jit Zh* 26-. 26- 25- 29? 3o' 27- * Jt -2LL 24- 22 21' 22 22-* 22- 22* 23. 24- 26' 27* 29* 3o- 27-* 3h* _2S. APPENDIX XI! N O T E S : Sounc/ings are in f<te£ referred Jt> Local low Wafer CeveL, which /3 6.° feet above Sand'hectc/s Pafunt. Sounc/tnas /a.ken 1 JTuLy /9*' , '?66 P U B L I C W O R K S O F C A N A D A F R A S E R R I V E R , B . C . A T N E W W E S T M I N S T E R F R A S E R S U R R E Y D O C K S O U N D I M G S . S C A L E S A S N O T E D S H E E T J O F J S U R V E Y E D B Y D R A W N B Y ^ ^ D E S I G N E D B Y V E R I F I E D B Y 4 C E R T I F I E D C O R R E C T D I S T R I C T E N G I N E E R E X A M I N E D B Y c' • * ' -' • A P P R O V E D O T T A W A 196 196 C H I E F E N G I N E E R PLAN N o . °s • Z -APPENDIX XV EQUIPMENT AND MATERIALS USED IN FIELD Bubbler. Compressor: PR 620 Cummins Dies e l 620 cfm normal operating press. 100 p s i Speed max/min 1900/1400. Compressor: PR 365 Deutz Die s e l 365 cfm normal operating press. 100 p s i Speed max/min 1800/1400. Hose: Carlon p l a s t i c , 1 inch I.D. 1-1/4 inch O.D. Polyethylene s e r i e s , standard type 11. 80 p s i . Available at Fleck Bros. $13.93/100 f t . Clamps: Tridon HAS-24 (3/4" - 1-1/2" I.D. and 1-1/16" to 2" O.D. ALL STAINLESS. Available at Fleck BRos. $42.10/100. Vessels. Launch "Sounder". Length 40 feet O.A. Draught 4 f e e t . 165 H.P., G.M. motor. Crew: 4. Launch "Port Fraser". Length 37 feet O.A, Draught 4 fee t . . 340,H.P., G.M. motor. Crew: 3. Snag boat "Samson". Length 90 feet O.A. 100 Tons. T r i p l e Exp. engine. Stern Wheeler. Crew: 14. STRAIT OF GEORGIA PLATE 1. NEW WESTMINSTER TRIFURCATION AREA, FRASER RIVER, B . C . (MAY 1959) . COURTESY GEORGE ALLEN Plate 2. Laboratory Investigations 2a. Steel and glass flume i n the C i v i l Engineering Hydraulics Laboratory at the University of B.C.; showing s t r a i n i n d i c a t o r (on table) for measuring hydraulic slopes, and pl e x i g l a s s s t i l l i n g w e l l ( r i g h t , foreground). 2b. Injector of meriam drops (releasing a meriam drop) and 16" long polyethylene hose with o r i f i c e s ( dia. 0.026 inch; spacing 0.75 inch) and emerging screen of air-bubbles. A i r pressure in s i d e bubbler 10 p s i g . The heavy black h o r i z o n t a l l i n e above the i n j e c t o r belongs to the g r i d painted on the glass of the flume. Plate 3. Measurements with the Miniflow Meter 3b. Dekatron counter unit of Miniflow meter with probe i n foreground. Plate_4. I n s t a l l a t i o n of air-bubblers on river-bed at Fraser- Surrey Wharf. May 24th. 1966. 4a. Part of the one-inch diameter bubble hose shortly before i n s t a l l a t i o n . Note 5/8 inch s t e e l cable; s t a i n l e s s s t e e l clamp; boomchain; and small balloon to keep hose suspended above river-bed while being payed out from wharf to "Samson". 4b. Bubble hose being payed out from wharf to "Samson". "Port Fraser" a s s i s t i n g . Plate 5. Fraser-Surrey Wharf (facing downstream), May 2 5 , 1966, showing lo c a t i o n of PR 620 Compressor and buoy. " A t l a n t i c Breeze" has j u s t a r r i v e d to load lumber. Courtesy George A l l e n . Plate 6. Sounding at the Fraser-Surrey Wharf, June 1966. 6a. View from top of Grain Elevator. "Port Fraser" running sounding li n e s p a r a l l e l to upstream part of the wharf. Note bubbles at mark 6 + 0 0 . 6b. "Sounder" surveying with s t r e t c h l i n e and range poles (one shown). Plate 7. Sampling of Suspended Sediment at Fraser-Surrey  Wharf, June 1966. 7b. Recovering b o t t l e containing sample. LOWER FRASER RIVER MISSION i SUMAS r (UPSTREAM LIMIT OF TIDE WATER I to a A9ASSIZ HH C H I L U W A C K B KOSIDALC \ (FIG 8) ( F R M - 2 3 2 ) o B R I J I S H _ C O L U M B J A W A S H I N G T O N FIG. I INTERNAL CIRCULATION IN RISING AIR BUBBLES AND ITS EFFECT UPON DRAG-COEFFICIENT NO CIRCULATION DUE TO IMPURITIES  AT INTERFACE. STREAMLINES LEAVE INTERFACE OVER PART OF REAR HEMISPHERE OF BUBBLE (SEPARATION), INTRODUCING FORM DRAG: LARGE DRAG-COEFFICIENT CIRCULATION DELAYS SEPARATION : SMALL DRAG-COEFFICIENT FIG. 2 I t A B A 1967 DRAG COEFFICIENT AS A FUNCTION OF REYNOLDS NUMBER FOR BUBBLES RISING AT THEIR TERMINAL VELOCITY IN WATER CONTAINING VARIOUS SURFACE-ACTIVE MATERIALS - 4 — ' - > • — r • • i j . . . . 1 • f • i |+H- L . . r i - ; i i-*- — - LAFT -H ,B IA M IV 1 {1 ON ) • H - i - •Hi!- r. i - ; - i • • 1 • : i , i : : : i : - - J j . l - t . I ' l l rH"! J " i ' i i i 1 i i • riii T _L 1 1- 1. 1 4-M-l- .!..! i.L 1 1 1 1 Mil ' i ' 1T 1 1 -i 1 - ; i i : 1 i 11 , i i i 1 1 ; J - . - - . r i . - ; - ; ; : n - J-.LI r ;T 3-V-C- -' y. i ;!rt i E "J- j" : . ' _L . : "t : . : ; . :.: . i : ' ' I i •;- z:. 1 1 ' im - i"fnf i ; i T TT , . , . . •\r, T z T i i T ! ' - : : i T i i : i i i i _c Z'C i - 1 -I . . i . . ' . a ' : ! i i :b t- • S f "I • "I " T - h 1 H r i ' - i rll. TT i -H j- ti : _ i ' ! 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' i i i 'in ± 1 r 1 I" "| i "IT I ' ' i i i ! i f i ! $ J: i i 1 T T f N : -j-htt -'-i-H EYff 1 1 1 T 3.1 -IT DtiC 1. 1!; T i"i TT ill! 11' Liij iii iii ih i 1 L T i 1 1 1 j | i 1 1 1 T ! i . i : j | - J ' A .Jl U l 'il' 3A - 1 1 T i _ J _ | . •\-i l l . .III' • ' i i : i 1 i : 1 1 1 1 1 1 • 11 ' 1 9€ 1 I 1 i i i ) 1 ' i ' i ' i ' l ' i ' l i ' ; i 1 1 1 1 1 1 1 1 1 1 ' *PPW 1 • w ur:^ 11 »\^I.IP+/I^ 1 ' ' i 1 1 1 t 1 t i 1 1 1 1 1 1 1 ' 1 . • 1 1 1 . ' 1 w y ^ t ~f M ' 1 1 ' 1 > 2 3 4 6 6 7 a 9 1 0 2 3 4 5 6 7 8 9 1 0 2 3 4 5 1 ) 7 3 3 1 0 10 1 0 0 1000 FIG. 3 TERMINAL VELOCITY OF AIR BUBBLES IN TAP WATER (2I°C) AS A FUNCTION OF BUBBLE SIZE FIG. 4 CALIBRATION OF ORIFICE METER IN 8" PIPE LEADING TO STEEL a GLASS FLUME, I 1/2 FT WIDE AND 5 FT HIGH- I 1.5 2 2.5 3 4 5 6. 7 8 9 10 1.5 t 2.5 3 4 5 6 7 8 9 10 | x |o : • FIG. 6 V ROD R, / W W R; SLOPE MEASUREMENTS IN HYDRAULICS U N I V E R S I T Y O F B C - LABORATORY BALANCED CONDITION —' = - 1 E = 0 L O A D R , L > R , R ; L < R : or R L L > R T STRAIN INDICATOR — 1 O 2 O 30 40 r - B U O Y A N C Y C H A M B E R | . WITH B A L L A S T 22 5 BRASS C A N T I L E V E R w w \ R i R ; ROD SETTLING RATE OF SAND PARTICLES IN WATER (RESULTS OF PURI SILTOMETER ANALYSIS WITH FRASER RIVER SAND FIG. 8 PURI SILTOMETER, DROPPING DEVICE AND ITS CIRCUIT DIAGRAM SWITCH 0 o- . A R E L A Y E L E C T R I C T I M E R JO. S O L E N O I D , . L I T J -.1.-3 . . - !- !i li- i-.-A-, / O O M A I N S P L E X I G L A S S T U B E F I L L E D W I T H W A T E R C H A R G I N G H O L E F O R S A N D SCALE (SILTOMETER): 1/4 IN-= I IN- C I R C U L A R T R O U G H B R A S S F U N N E L S WITH S E D I M E N T 200 CM S E G M E N T A L C O L L E C T I N G T R A Y *) FRASER RIVER MODEL VERSION A B A 1966 FIG. 9 >».A0£ 1 N CANAC* 0 5 1 1 — i — i 1 1 | 1 i i i i -I >\ V t f > r 0 :r \ z < k_ ID J c V -y |t X A n f f t] r P m MS R f 11 n f \i 1 s- i i 1 1 ni n j ( c hill V ) i 1 c -c 1 i i i \ i \ \ T r I iT\t r t c re D- j r 2 5 i n ; i Ui t 1 i 1 , • • • • 1 ! 5f 1 j i • w o -\ i 1 HI )W ~$ R — -3 r :i I ' M l WE. t r u - > i i , 1 1 1 1 1 J . - : i 1 .l.L T i i J 11 fc r -SLSl F Ik- k bL < | 1 ! I T i 1 | I.I 1 i i i 1 i 1 I M i l UJ i | | i c 1 I i | | 1 1 z 1 l l i i i i 1 1 , i -59— 1 1 1. ] i S C J u . i ! 1 j | i — 1 — 1 1 l I i T 7 1 I 1 1 I 1 u n o ZON1 \. f 1 i -15 1 1 1 i I * 1 l _ 1 ! ! TiTC a l r 0 7 l ! ! 1 It/1 ' ] i ; ; 1 1 ! i , 1 i 1 1 ; t 1 1 y i 1 ; | 1 i | , 1—1 1 i 1 r 1 1 1 1 | 1 ' 1 I 1 i I t i —• (1 ; ! I i i i 1 i i l 1 , i i i  i 1 1 1 ;— 1 1 I I 1 i M J 1 i 1_ 1 i i i i T .1 i i 1 j 1 *\ i i i 1 : -A r V J i I • 1 r\ • i V1 . . i _ __ 1 i A ; i . \ i y N s S ! 1 I I J i v M I i 1 [ — i — i i I 1 u w ! I | | i 1 i i >. ! I > - L L r 1 1 - T i 1 ( t ' f ! I | | I T i i 1 o! I i : | i i 1 ! 1 i r 1 ! j 1 1 I J i I I i 1 A r -w i 1 — i i 1 'N L i I i j | • — . M l | \ i 1 < I i I \ I ; i i i y \ 1 \ I —t—• i i i / | | i 1 / 1— N — —<r**~ s. i 1 (\ 1 i l f K 1 • i ^ i \s\ 1 j[ . L. v. ^  l l i s f i : 1 - I ; 1 1 r i ! | i I ; ! I I ' 1 W i 1 i i 1 —*—I J 1 i i.L j_ i i i I 1 i - < »- i j | - )"— I t 1 • , — p _ , — , — , 1 1 i I l 1 | t 1 : 1 t l ! [ 1 i 1 1 1 1 1 i : 1 ! 1 1 i i i ! i j : K — K ! f t n i l —1 I— i 1 1 i ' 1 i I I J k | y- 1 i f—1 i / V j / \ > —n— v^- • i I i i >>. 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M i i >4 i - l 1 L J 1 y C •4 i : 1 1 j l >" i r i i f n i i i l i i IT 11 i i 1_ M M 1 M M | i j i i i , t 1 ! n i l I I ; i  i 1 l | l > M M i_i i_-!-i • : M i i 1 1 1 : ! i . i . i 1 • i 1 I ! 1 i , ! r . i i 1 1 : 1 i | ! i 1 , i i i 1 ! 1 M M | i _ , ; , | | H T T .. i.. ! 1 ; ! i 1 f i • i i i M i i \ | ; 1 i I 1 i ! , i i ; : ; . • i 1 ; 1 i ! ! M M ! 1 i l l ! 1 ! I I i 1 i i 1 ' 1 i I j _ • ! +— — +— I 1 I l l ; j i i p ! | | I - i — —1~ { | I I I | | 1 L. _ 1 -< L 1 I i.. i 1 - s i — - t t-< »-1 ~~ • • fcr 1 i **- w 1 i ! i i 1 I i | i • 1 1 1 1 i 1 i —1— 1 i — I — I 1 I 1 r ] L (_ i i 1 ! 'I | 1 i I i t 1 ORIFIT i K I 1 i i . I 1 . ' 1 1 I I I i i 1 - i-p" 1 | i i 1 i I i w i i 1 | r 1 — i h I'-I 1 Fi 1 F F I o 1 J oto  1 1 HtJRl z 7 I fc I 1 i IJfi n k NT fi 1 * s 1 1 B I1 h 3 6 9 1 1 1 L r >\ \ i R J \ 1 ) V > r II i ) . ir 1-1 ) p 1 / \ | t > l \ | i f j j •M ll- | R c * 1 • • p T j M AT 0 A i— r T uc 1 J T \ _ 1 n r )IF •1 IVJ rc •[ i - \ I M P L. \ u <ir 1 r l\ IE c .r i \J 1 yj l M L r ? i f •I n r» ti it •% I Jr L U1 1 U r i\ j l 1 i d ML \h i / - i r r i •r. i / i K 1 r r / i V 1/ 1LQ L J J h n. w Li ^. a1 LL * ~- p* l i f It i J \ P i t l l l i J M I I M s J u F << IS 1 l i |W i i i 11 c • r u i I i« 11 « ; | i q F Zi ) g u \| 2 ?Z • i 1 1 1 p i 1 ] .1 . \) F T K c • > d i i i \ E I n c V Y *' 1 F T A ;E c < ri a. u i • ^ i — 1 \ i I A h i i 1 >. • — - 1 1 >- 1 — >L — i- - -« i - * E 1 | • i ! i r 1 i 1 : i I 1 1 1 i i | i 1 1 1 i j i i i 1 1 i i 1 1 i 1 L A . I i i 1 '< x 1 1 i i j '{ K s i . A r ... r T* ! | I L ^_ —i i r-<j I 1 s l - L -c }-r~ i I i L V f i i c. i 1 1 1 ; 1 i | | / \ A \ >; J. i 1 i J *i f\ |J>'| -1 - I t > > -^ i 1 ! i 1 i — ! — < ?- i 5 - i 1 i , ! . . i 1 i 1 r CI-6 i . i i i i 1 | ! 1 : i ! ! ' 1 ! 1 ! i 1 1 i__ i ; ! i 1 1 1 1 i P I . I I 1 i | 1 ; j I I I : . ; ! I ! i 1 1 1 l I j 1 1 ! ' 1 i ; i J . _ ! _ _ . 1 1 I 1 i ' L i ! i i 1 1 i i 1 \ i i 1 i i i 1 i I 1 i i i 1 i 1 1 1 1 i . i i . I | I 1 1 1 N I I I i 1/' V j 1 /\ 'v I i 1 / \ \» ~- 1 > - r* — -— 3 - . •— •4 i i H r I i i 1 i' T | i ...!__: i . ' i ' 1 i i U 1 j I i i ) ; i 1 ; i J 1 1 I ' . i i i | 1 i 1 i I ! ! ! 1 ' 1 I 1 1 i ! i | i i l i r i i I i 1 r 1 r ! 1 '< i _ l _ _ 1 i i i t i i , l i l t i 1 . i .j i i ! 1 ; ! 1 1 1 i i i j i i ; i i i i i 1 ! 1 , i 1 i 1 I 1 i i ! 1 ! I 1 ' 1 1 I I I ! 1 i 1 i 1 i ; i i i i ' i i i i i i . 1 I A u A » i 1 < » , < H r . ( + j 3 _ , . * 0 2 I I f f V f 1 i i i : j ! t I 1 i I j ! 1 'z 1 1 t 1 1 i i IPU rF i 1 i ! 1 1 i r1 . i. 1 1 i • 1 I n t IB Blr E:F B F 1 1 J i 1 1 P ( 0 i 1 1 n 12 <? - '! 3" •4 IN N :< 1 I A 1? 7 i 1 ft VI -1 Pt "11 T r r tl N n Cl F n -| -< Ai 1 M ^ I T •\ rvr 1 1 u y T 'A • n J r 1 1 1 r W i w 1 L i t 'i - L . I •Y , L i -€ i • i < J "< us rr 1 IN i f T E J 1 P'J t X St i f f \ I >i /VI R c IE S- EJ IIC m\ "tl r >l( S M r t V i i \ i .[LI i & 9 1 Z IP- 1 r* M r c j 51 • C .9 1 IT>I 1 n o' i *H— 1 1 VJ 1 \\ Z l 1 / 1 c. »-; 1 h 1 II f\ (A R 1 A ! O' i . a )( VE T T I HI / j>, y. H O H • • • > < >- 1 ) i— V i i •1 1 I / 1 ! i i V p i j i 1 4 4 - H 1 ' i 1 i 0 € i 1 i i i : j ] i i I l i i 1 1 i i i i j l 1 1 1 1 i 1 ( , 1 I rk i < II i ; , i n i i / V I c i „r ?• r — , / -4 fr i " N 4 M - ( r- , >• •) J) 1' -< L 1 ~ 1 1 1 I ? I 1 1 j H 1 I i 1 ' 1 0 : 4 T i i 1 i i H— U - 1 i | i i i 1 1 j 1 ! • | I 1 ; 1 1 i ! I 1 | | i i i i ; I 1 1 i i * i 1 1 | ' i 1 i 1 : , 1 1 1 i i i i J t i | ! 1 ! 1 . I i i ; ; ! 1 ! 1 1 I i 1 : . , ' 1 ! i i i : i i ~\ I ! 1 i 1 .: i i A i \\ i i \ 1 < I. —t-f-t I , i V \ A • V > t /i ( ri - -G ) - e>- - ( >-u > • * 9 •2 . ! f 1 < r f i . i i I 7 i i n i 1 \j i ( n_ 1 I 1 / • 1 : lit H r •I • 1 u C < H 1 kar J \. D 1 ac E IE 3 6 a H rf O I 8 3 * S 6 7 8 9 10 II 12 FIELD INVESTIGATIONS AT FRASER-SURREY WHARF DURING FRESHET PERIOD, MAY-JULY 1966 EBB FLOW bm1 brm 2tOO 4*00 6*0 0 T 6 8*00 0 ts £L s s bm © Bubbler hose Compre ssor Hydraulic-slope recorder Stilling well for , , T ide scole Buoy Sounding lines OPW Suspended sediment sampling Bed material sampling Current observations F R A S E R - S U R R E Y W H A R F S C A L E : ONE INCH = 1 2 5 F E E T (See also F igures 18 and 19 for observat ions of S u r f a c e Currents) A B A 1967 FIG. 16 WATER-SURFACE SLOPE MEASUREMENTS , FRASER - SURREY WHARF, NEW WESTMINSTER 30 K< 30 K 2 8 V 50 K / A > 30 K > 30 K BALANCED CONDITION -FLOAT V O L T M E T E R RIVER L E V E L DOWNSTREAM FIG.17 1030 30 K 30 K B >50 K —1>: 28 V ,30 K 30 K SUSPENSION —WIRE —STILLING WELL UPSTREAM A B A 1 9 6 6 SURFACE CURRENTS, FRASER-SURREY WHARF JULY 19 , 1966 , 17 0 0 HR PST- (TWO HRS-AFTER LLW AT NW-) HOPE DISCHARGE 2 1 3 , 0 0 0 CFS EBB FLOW 1 4 . 12 . 10 TIDE CURVE RECORDED AT FRASER RIVER AT NEW WESTMINSTER, B C J U L Y 19,1966 0 0 h 0 0 h 12 0 0 T J U L Y 19 h 0 0 0 0 T i m e h 12 0 0 -i 4_5 4 5 a . B u o » 4~0 ' ^ ~ * i ' 5 - 4-5 , * J-6- , , •* ^2 9 - - *JJ> J_0 ~0 - - *1~9- -~^~Z I ~J_9 - - «_«•' o o O O Cy " " " " o °9< A? ~ ~ - > I 1 1 1 1 I — 2 * 0 0 4 * 0 0 6 + 0 0 • 8 + 0 0 1 0 * 0 0 F R A S E R - S U R R E Y WHARF S C A L E : ONE INCH = 125 F E E T C U R R E N T S IN F E E T / S E C O N D ABA 1 9 6 6 FIG. 18 1. J SURFACE CURRENTS, FRASER-SURREY WHARF JULY 24 , 1966 , 17 0 0 HR PST (ONE HR- BEFORE LLW AT NW-) HOPE DISCHARGE 2 0 5 , 0 0 0 CFS E B B F L O W io TIDE CURVE RECORDED AT FRASER RIVER AT NEW WESTMINSTER JULY 24 , 1966 h 00 00 h 12 00 h 00 00 •JULY 24- Time ,42 4 4 3 4 4 2 42 4 7 Buoy *^ - & .2 9 +±1 4_4 2 9 ~ - 2 2 12 II 0 9 o_, 01 / ~ OA- - <-J C3 O CJ C_3 o 2 + 0 0 4 + 00 6 + 0 0 8 + 0 0 F R A S E R - S U R R E Y WHARF S C A L E . ONE INCH= 125 FEET- CURRENTS IN F E E T / S E C O N D 10 + 00 ABA 1966 FIG.19 UJ u U J Q DEPTH IN FEET DEPTH IN FEET 5 5 1 to G9-10071 (8i53) 0.1 AOOI fVite * o J^-ri?£f Ti me G. Ht. l_Dlscharge_ Snmpla cS 2- 2- & . Sta. //. /• Depth 5" / Analysis /5c-~2? w •"j'A~-Jr ••<••»-•» / 0.01 0.1 1.0 . V DIAMETER IN MILLIMETERS G9-10071 (RI53) G9-10071 H2J3) G9-10071 (1253) 9 9 . 9 P 99.8 9 9 3 99.0] 98 ll!iT!l!!fii!i?iii.w ? 9 9 . 9 95- 90 80 70] 60 50 40 3 0 20 L U z LL. t— • z L U u L U Q - 7 1.0 05 0.2 0.1 0.001 mm DEPARTMENT OF KORTHERN AFFAIRS AND NATIONAL RESOURCES WATER RESOURCES BRANCH M I > £• >2 Date 3 a / ^ v - t ^ Time_ G. Ht. !_Dlscharge_ /9:oo Sample <T Z ? ?> Sta. (V. f. jrfs. -PPM. _Deplh_ Analysis j3&t ^ if A <Jr o. / . V 0.1 1.0 DIAMETER IN MILLIMETERS MICROGRAPH M A D E IN C A N A D A f j i pi po t O o 1 0 0 MADE IN CANADA. ,00 t O C 100 

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