In the context of plans by the Province of British Columbia to construct a bridge over the Lower Fraser River to replace the George Massey Tunnel, MetroVanWatch is posting this preliminary report by Trevor Langevin, with permission. Download: fraser-river-dredge-report-sept-2016-langevin
Implications of Dredging the Lower Fraser River for the Purpose of Increasing Commercial Shipping: The Risk to Specific Industries, Services & Fisheries
The waters of the upper Fraser river have come to the top of their river banks nearly every year. Every year there is a flood watch during the spring snow melt run off. In the lower sections, the river has breached the lower mainland’s dike system, the two worst years being 1894 and 1948.
The river is dangerous and unpredictable when too much water from melting snow runoff hits the river at the same time as the oceans high tide. Steps to tame the river happened when the larger Southern main flow was dredged to a nearly uniform 35 foot depth, from the mouth of the river up to the New Westminster bridge. The Northern channels of the river were used mainly for the logging industries so were not regularly dredged. Dredging has happened right up to the Mission bridge during the last 100 years. The ships that require the river to be dredged to a 35ft. depth all used the larger Southern flow.
The new bridge to replace the George Massey Tunnel is in controversy because the news media has found inconsistent reasons for its being pushed by the Government. To the Governments point, yes the current tunnel is backlogged, but to the common person, that is not reason to decommission the tunnel before its service life has been reached, which is the opinion of BC residents.
The people of British Columbia have been led to believe the tunnel is the safest in North America, and the world because not only is it buried under the level of the riverbed, but it is encased in stainless steel to keep it watertight. That’s primarily why it was so expensive to build. This tunnel was meant to last, it was designed to survive being run over by a commercial ship navigating the channel.
Then without warning, it was deemed unsafe and needs immediate replacement without any evidence?
From a commercial standpoint, at least on paper the Fraser Surrey Docks are at a disadvantage in that its competition in downtown Vancouver can handle post Panamax sized container ships (that did require dredging). The Roberts Bank Superport was specifically built to handle all oversized ships, and the Duke Point terminal in Nanaimo can handle one post Panamax ship but it has no rail access, and only one retired crane. The only issue stopping the Fraser Surrey Docks from handling bigger ships is the George Massey tunnel, and deeper dredging of the Fraser river. What has not been explained to the public is that Port Metro Vancouver is one commercial entity, but the Downtown Vancouver Centern Terminal and Vanterm Terminal, and the Fraser Surrey Docks are also 3 separate commercial entities.
Other industries using the waterway have publicly stated they have no need to have the river dredged any deeper than its at now. The largest user Seaspan does not need the river dredged for its shipping purposes. CN, which is building a Intermodal Container Port in Richmond said it does not need a deeper port, and The Japanese car ferries that deliver new cars from Asia to North America don’t need it either. They dock weekly at the Fraser Wharves in Richmond and Annacis Auto Terminal across from the Fraser Surrey Docks.
Because of the differences of opinion in the overall project This has led many, even Richmond Mayor Malcolm Brodie to state;
“This bridge is just an excuse to dredge the river!”
Hydraulics Of The River
The river dredging system has worked so well to control the flooding risk, that the need to have the river properly and scientifically modelled, has not happened. This needs to happen to discover what will happen if changes are made to affect its flow. Nearly all major cities that have a river flowing through them now use large room sized scale models and computer modelling to research any and all aspects of their river systems to make absolutely sure that man made changes won’t have any detrimental effects. In this day and age, its just going that extra mile to prevent Murphy’s Law!
Water seen flowing in a river is not usually associated with the principal of hydraulics. People assume the casually flowing river is just a meandering flow of water. People also do not generally associate the Pacific Ocean having any effect on the river. That cannot be any further from the truth!
The Pacific Ocean is a very different beast from the Fraser river. The tidal range for the lower mainland is 16.1ft, or 4.92M. But the river, depending on flow rate can increase that range by several factors from snow melt runoff.
In the river channel, the ocean waters run up under the Fraser river’s water. The two don’t mix because of the salinity of the ocean water. They behave like oil and water in a glass cup, remaining two different independent liquids. At high tide the ocean can cause the river to back itself up. This can happen at up to 30kmh river speeds. That is a huge hydraulic action that the ocean is pushing river water backwards. The ocean waters now (on paper) go as far upstream as the Mission bridge, but where high and low tides end during fish migration times it is not known.
The tidal action, and constant dredging have reduced the riverbed’s obstructions to the point that residents don’t worry about flooding as they used to in the past. In 1948 all along the Fraser river was flooded. In the last 100 years Richmond’s dikes have only been breached once. The dike failed at a river bend from the combined ocean and downward currents action of washing out the dike.
The predicted implications of this dredging plan is the displacement of ocean water pressure. After dredging, the oceans at high tides will be able to add more hydraulic back pressure to the river, causing more lower river restrictions. This back pressure will increase the risk of flooding in the upper Fraser Valley at high tides, and during the high spring melt runoff times. It would also have the effect of channelling more water to the Northern channels. At low tides, because the newly dredged area is at a lower level, there may not be enough oceanic hydraulic pressure to push saltwater and the fish up to the Mission bridge. This lack of saltwater and current assist would, (not could) have the effect that less fish will be able to reach the spawning grounds and further thin out the stocks. Just as aircraft use the jet stream, flying in the same direction saves fuel and decreases travel time. Flying against the jet stream uses more fuel and increases travel time. It’s exactly the same for the fish in the river.
The Fraser river’s freshwater current is going downstream, while the ocean’s upstream current is only during the rising tide. The turning basin is expected to cross the river’s width. Depending on how sharp the rim is cut, anything less than a laminar flow will cause disturbances and back pressure in the river’s flow, just like a finger plugging a garden hose. The more back pressure there is on the river’s flow, the higher the water level will get. The only help that fish get going upstream, is the ocean’s rising tide upstream current. Disruptions in that flow means the fish won’t get as far of a push as prior to the dredging. The less fish reach the spawning grounds, the less fish there will be next year!
Figure: Ocean Hydraulic Pressure of the Lower Fraser River
A. The cross section of the river gives an example of the fresh water and ocean water separation. The ocean water stays below the freshwater due to salinity differences.
B. As the tides go in and out (the river currents) this changes the hydraulic pressure of the ocean water and raises the fresh water level on the in tide and lowers on the out tides.
C. The ocean is rarely calm and during the winter months or storms the ocean surges. Just as waves develop on the ocean, this translates into variable pressure spots or pulsing under the water. This is a hydro-static shock.
D. The currents and the hydro-static pulsing will cause the sides of the newly dug trench to erode and collapse back to the lowest part of the dredge. The riverbed is sand, and sand will average a 30 percent slope. If that sandy slope goes under a dike, the dike will be eroded from underneath.
E. This is made worse by bends in the river. Just as an object in motion will want to maintain that motion, objects changing directions will amplify the forces in a turn, such as a river bend. These areas of higher erosion will be the first areas to be eroded under, or the erosion shape will help funnel surge waters over the dikes walls.
F. The same applies to vertical changes in the river. This diagram by the Government’s Environmental Assessment Office shows the erosion pattern of the riverbed on the ocean side of the tunnel because the majority of the ocean’s hydraulic forces going over the tunnel is being compiled there.
Dredging To New Depths
The 100 plus years of dredging the river has worn the riverbed to a nearly uniform or smooth shape, including that and the action of ocean and river tides. By changing the depth of the river, that will increase the ocean’s hydraulic force and ability to manipulate the river. Over time the dredged area will increase in size from hydraulic erosion until its banks are a uniform shape again, with roughly a 30% slope from shore to shore.
The Fraser River Pile & Dredge ship Fraser Titan runs almost daily up and down the river. The sand collected from the bottom is sold to construction companies to be used as preload or land fill. The dredging process to maintain the current 35ft depth does not stir up much debris as the cutting head is skimming along the bottom only shaving off the recent buildup.
To increase the river bed depth requires changing from a maintenance type of shallow cut, to a digging cut. This increase will stir up much more sediment and debris. This will be sand, mud, silt, rocks, wood and anything else that is in the path of the dredging head. From the fisheries perspective, the majority of fish will be going up stream using the northern river channel because of the currents around the University of British Columbia, however those in the southern channel will be fighting through a mud storm both upstream and the new fish heading downstream.
Recommendation: If the enlarging of the river depth is to proceed, it should not interfere with the fish migration times of the year. If this information is contested, a demonstration cut in shallow water to see the effects of this plume should be arranged and recorded.
Caption: The Fraser River Pile & Dredge ship Fraser Titan is a 70 year old ship. In 2015 she was put into dry dock in preparation for this work. This picture above right shows her getting her propeller shaft bearings upgraded.
Caption: There will have to be a turning basin or dredged circle for ships at the Fraser Surrey Docks to turn around. On the upstream tide, this circle, if dredged in this pattern will be rapidly eroded and be the cause of much sand and debris flowing down stream. This erosion will undermine the docks unless they are piled deeper than the erosion pattern. The dike system in critical areas will require new pilings that prevent sand erosion from undermining them. This is the same failure mechanism of the Levee system in New Orleans during Hurricane Katrina. The storm surges undermined the Levees supports.
Critical Industries Along The River
A brief study was compiled to see what industries are at risk along the sections of the lower Fraser river to determine what their economic loss would be. This list is by no means complete, but its enough. The Down Current Trap area would block fast moving downstream flood waters, which would be forced over the dikes flooding Tilbury Island.
Caption: Based on flooding during prior years, the arrows show the direction of the water flow should the dike system fail in the same places it has in the past.
1) The LaFarge cement plant. It is the largest suppliers of concrete in Vancouver.
2) Con-Force precast concrete structures. This company supplies prebuilt concrete forms to projects throughout the city.
3) Lehigh cement plant. Another large supplier of concrete to the lower mainland.
4) Seaspan Ferries, Tilbury Terminal. This dock specifically supplies all of Vancouver Island with all of its goods and supplies that are shipped via truck or rail. It also organizes the delivery logistics. Loss of this facility would cripple Vancouver Island of all goods and supplies!
In an emergency the Seaspan Ferries could use the BC Ferry terminals, but that would bump BC Ferries from their scheduled sailings, and hinder passenger flow. Resupplying the island through the BC Ferry docks would cause major highway and road disruptions as trucks would have to be shuffled between Tsawwassen and Horseshoe ferry terminals.
Those terminals have no rail transport capability. All rail supply is now through the Tilbury facility. The logistical organization that this facility provides of getting those supplies to where the’re needed would still be crippled, so moving goods without proper logistics won’t work.
There is only one other operational rail barge dock, run by SRY Rail link on Annacis island. It too is in the South Channel. The remaining rail dock in downtown Vancouver is shut down and the Annacis Island dock is its replacement. Richmond’s North channel rail dock was damaged beyond repair, and shut down some years ago. It was dismantled. The only other rail dock is in Bellingham at the former Georgia Pacific pulp mill site. Its status is unknown.
5) Fortis Tilbury LNG Liquefaction Plant. This plant supplies LNG to Victoria. It has exclusive supplier rights to cities and towns in the North West Territories. Lastly it supplies Metro Vancouver in the peak power times.
The loss of these key facilities would have severe implications throughout BC and the North West Territories.
Caption: This section of Delta BC, as in the past would be expected to be the hardest hit in the lower river because it has the sharpest bend in the river. Combining factors such as the new dredging depth, high tides, ocean surging, high river flow from snow melt and the erosion of the river bank forming a scoop, could easily push the downstream flood water flows over the dikes, as in the past.
The Fishing Industry
The Fraser river is a fish bearing stream. A very simple question to dredging the river is;
“What will dredging of the lower Fraser river do to the fish stocks?”
To answer that question most would just consider the risk the dredging machine itself makes to the fish, and not think about the effects of the mud disturbances that will pelt the fish down stream of that mud plume.
Salmon are born in fresh water, then they have to adapt to being a salt water fish. Then they return to their birthplace in fresh water, spawn, and die. Some say that is how nature made them. Science describes this as a process. Fishermen say that when the fish returns to fresh water, they begin to rot.
This is three different valid opinions on the life cycle of fish. What is true is when fish that have adapted to a salt water environment enter fresh water, they have no more than two weeks to live before they die. They are dead within one week of spawning.
Currently the fish swim up the river staying in the lower salt water layers, using the tides as much as possible. Beyond the Mission bridge they enter the fresh water area. It is not currently mapped where the salt water table ends at high tide or low tide, but the Mission bridge is what is printed in the fishing guides. This is a void in understanding the life cycle of fish.
If the fish do not make it to their spawning grounds, most will die without spawning. The less that spawn, the less there will be for next years hatching. Male Salmon do fertilize more than one female fish, but with all mating practices between animals, not all fish can be expected to mate several times.
The health of the fish can also be questioned. If as fishermen say the fish begin to rot as they enter fresh water, can a rotting fish produce healthy offspring. Is this also the reason for the fisheries decline?
This is something that needs to be properly researched in the Fraser river;
Question 1. Has past earth changes and the last 100 years of dredging reduced the distance that salt water travels up the Fraser river?
Question 2. Will dredging the river change the dynamics of the salt water to fresh water ratio? Will the current Port Metro Vancouver plan for dredging of the lower Fraser cause changes that reduce the distance that salt water travels up the Fraser river estuary?
Question 3a. Will dredging of a small channel in the upper Fraser river that allows saltwater to get closer to the spawning grounds of a salt water fish, increase the fish population?
Question 3b. Or is the answer to also dredge a collection of areas on the riverbed where saltwater can fill at high tide, and not be immediately washed away at low tides? This would allow the fish to hop under the fresh water, but between lower salt water pools up to the spawning ground.
Dredging is not a negative on the environment, but only research will tell us what changes are needed to this plan to allow both projects to succeed.
Research will most likely reveal that deepening or widening of the shallower North channels of the Fraser river is the answer to allowing more water to flow downstream during the flood season, as it will allow more waters to bypass the dredging obstruction at the Fraser Ports.
For the Fisheries, what is the balance between dredging the North and South channels that allows the saltwater to continue to reach its current destination up the estuary, or increase it closer to the spawning grounds. It is well understood that the Fisheries have been in trouble for many years, and the past concept of allowing Mother Nature to decide which fish makes it back to the spawning grounds is clearly not working. Dredging that has negative effects on the river’s health is NOT Mother Nature’s doing!
The immediate answer seems to be that a salt water channel up to the spawning ground would be the best idea. The fish ladder system has clearly saved the Capilano Fish Hatchery, which exists at the bottom of Cleveland dam! A salt water path for the fish to take up to the spawning grounds seems the best and fastest idea to restore the Fisheries health.
After a long consultation with the Environmental Assessment Office over the new George Massey tunnel replacement project, the position of that office was;
“If Port Metro Vancouver wants to dredge the river any way they want to, they can go ahead!”
Clearly this is not the right answer!
Research That Needs To Be Done
1) There is genuine concern among the population that further dredging of the Fraser will have unintended consequences.
2) There is genuine concern that if the government pushes the new bridge through, that dredging of the river will also happen. Both issues are linked to this bridge and both need to be addressed. For the population living along the Fraser River there needs to be scientific proof deliverable and understood to the common person that dredging, or any future changes to the river won’t cause an environmental or economic disaster.
Research may reveal that widening the river’s pinch points, or increasing the river’s volume by dredging only the fresh water areas is the answer. Increasing the volume flow in the Northern channels would also reduce the pressure on the Southern channel. Once that part has been alleviated, the bridge project, and future projects to do with the Fraser river will have a much easier time of proceeding by the public.
Recommendation: This modelling facility should not be a one time project. Currently the National Research Council of Canada’s – Ocean, Coastal and River Engineering (NRC/OCRE) in St John’s would be the facility to do the research. Fisheries and Oceans Canada should also be part of that research too.
For example; questions this facility should be able to answer;
The dredging of the Fraser river has raised some questions on the health of the river.
a) Will these dredging changes undermine the soundness of the dike system?
b) What changes to the riverbed will affect the river’s flow?
c) How will the river be dredged?
d) What will the shape of the dredged river be after dredging?
e) Will those changes made to the river erode the dike system, and will more piling prevent that failure?
f) What is the long term forecast of how the river will behave to these changes.
g) Will the changes affect the fish bearing capability of the river?
h) Will these changes affect the freshwater and saltwater tables?
Along with this immediate concern, the model should be able to deal with future dredging possibilities. Will dredging reduce the salt water table from reaching further up the river? And with absolute certainty, the river should be modelled as if man had not been there to do a comparison of what the status of the fishery would be in either case.
According to the City of Richmond’s records from First Nations oral history, shellfish used to grow in the mouth of the Fraser river up to the 1900’s but after that they could no longer be found. The industrialization of the river is clearly responsible for that decline. By understanding what the future and past changes are, that comparison of what is needed to determine the best possible choices for BC’s economy, the fishery, and health of the river can be made.