Winter Safety on Alex Fraser and Port Mann Bridges Explained

port mann bridge

Winter doesn’t mess with the Lower Mainland all too often. But when it does, our maintenance efforts go beyond the standard plowing and sanding of highways. Our attention is also drawn skyward to the cables on the Alex Fraser Bridge and Port Mann Bridge.

Snow and ice can build up around the cables that support the bridges, becoming a safety hazard to traffic below if left to freeze, melt and potentially fall. To combat the risk, we developed cable collar systems as a mitigation measure to reduce snow and ice forming and falling.

How it Works

During a winter event, Rope Access Technicians (affectionately known as RATS) release the collars from the top of the cables – manually by rope access on the Alex Fraser Bridge, or remotely, as is the case with the Port Mann Bridge. The collars, which are basically chains that fit around the bridge cables, remove snow and ice as they move down the length of the cables. Think of the collars as specially-designed scrapers. It takes a collar under a minute to travel to the bottom of the cable; times vary due to the different lengths of the cables.

See what a collar drop looks like on the Alex Fraser Bridge:

People have asked us: “doesn’t this damage the cables?” The chains slide on the protective cable sheathing, not on the structural steel cables themselves. Wear on the cable coatings is minimal and monitored.

When it’s time to reload, the technicians manually detach the collars from the cables, move them to the towers, and hoist them back up to the top of the cables using lifting bridles via winch and davits (crane-like devices) mounted on the bridge towers. Reloading times vary depending on the number of chains dropped and the weather conditions in which the technicians are working. The technicians can safely work with maximum wind speeds of 20 km/h.

Also, our maintenance contractor applies de-icing solution to the Alex Fraser Bridge cross beams before winter weather events are predicted.

What it Means for You

As a safety precaution, we must temporarily close the outside bridge lanes closest to the cables when dropping and reloading the cable collars. In the Port Mann’s case, these are the HOV lanes.

For reloading, we choose a time when lane closures will have a minimum impact to traffic. However, we don’t have as much flexibility when choosing when to release the collars because it depends largely on the forecast and current weather conditions.

Depending on the snow accumulation on the bridge deck during the closure, our maintenance contractor may need to plow before we can safely reopen the lanes to regular traffic.

Rope Access Technicians on Port Mann Bridge
Rope Access Technicians reload the cable collar system on the Port Mann Bridge in January 2020.

What About Heating the Cables?

Some of you have wondered: “couldn’t we avoid lanes closures by simply heating the cables?” Heating the cables isn’t as simple as it sounds. We’ve looked into it, and we’re not aware of any other cable bridge in the world that has successfully used heated cables to address snow and ice build-up.

There is a huge surface area of each of the cables that would have to be heated (for example, there are 26 kilometres of cables on the Alex Fraser Bridge). With the wind, rain and snow hitting the cables, the heat loss would be tremendous, and providing the immense amount of energy needed would not be practical. Ice would also form outside the heated section of the cables, defeating the purpose. Based on the research we did when exploring snow and ice clearing technologies for the Port Mann Bridge, the power needed to heat the cables for just one hour could run a small community. Heat from such a system would also damage the cables’ protective sheathing.

Were Any Other Systems Considered?

We considered a sweeper system, with brushes moving up and down the cables, for the Port Mann. However, it would have required additional cables that could be problematic in a snow storm. The system was not very reliable or effective under extreme ice conditions for its designed purpose, so we chose gravity-dropped collars for both bridges given its less complicated operation.

By the Numbers

Alex Fraser Bridge Port Mann Bridge
Year Opened 1986 2013
# Lanes 6 (7 coming soon) 10
# Cables 192 288
# Collars per Cable 10 30
Collar Weight 7-9 kg 12-22 kg
# Rope Access Technicians 12-16 12-20

 

The risk of falling ice and snow on the bridges – even the Alex Fraser, which is more than 30 years old –  is relatively new. Most years, very little snow accumulates on the cables, or the majority of snow is light and blows off before accumulating enough to pose a threat. In fact, the three temporary closures that happened in the winter of 2016-17 were the very first on the Alex Fraser due to snow/ice forming on the cables.

Sometimes, a combination of factors can lead to the build up of snow and ice:  the type of snow, temperatures fluctuating around freezing and making the snow wet and heavy, a high range of temperatures that quickly heats the cables, as well as wind direction.

But with these cable collar systems in place, we are in a much better positions to contend with the conditions nature throws at us.

After each weather event, we compile a post-storm review to discuss areas of improvements and implement measures to prevent similar situations from reoccurring. And we’re constantly investigating new technologies/innovations to improve snow and ice operations.

Got a question about the cable collar systems that we didn’t answer here? Comment below.

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Page 1 of 39 comments on “Winter Safety on Alex Fraser and Port Mann Bridges Explained”

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  1. I use to work on the transmission power lines and to save time from climbing up and down everyone which would take alot of time and physical work theres a portable cable device that allows you to get out and around to the next one fr above, shouldnt be to difficult to make a device with a small dolly wheel that locks onto each cable with a plastic scrapper not to hurt the span and even vibrate as its remotely driven up and down each cable using a lithium battery pack, then transfer to the next cable, it be like a mini cable car the size of a small winch which can be controlled through a remote control…. can always have someone or some device to send an acoustic signal via cable maybe tap with rubber mallet once every half hr when weather sees fit to do so, or perhaps spray them with a non stick material thats out there today,

    Reply
  2. Heat them?!?!?!!? Like heated rail lines in EU? I’m sure bc hydro and and bc transit can come up with some kind of system… damn you both have trained engineers… you have electrical and mechanical engineers…both under the bubble of bc gov funding… add a wrapped coil of heat emitting.. wire.. coil.. come on…

    Reply
    • Hi there Ashley,

      Here’s more info, from the blog on heating the cables.

      What About Heating the Cables?

      Some of you have wondered: “couldn’t we avoid lanes closures by simply heating the cables?” Heating the cables isn’t as simple as it sounds. We’ve looked into it, and we’re not aware of any other cable bridge in the world that has successfully used heated cables to address snow and ice build-up.

      There is a huge surface area of each of the cables that would have to be heated (for example, there are 26 kilometres of cables on the Alex Fraser Bridge). With the wind, rain and snow hitting the cables, the heat loss would be tremendous, and providing the immense amount of energy needed would not be practical. Ice would also form outside the heated section of the cables, defeating the purpose. Based on the research we did when exploring snow and ice clearing technologies for the Port Mann Bridge, the power needed to heat the cables for just one hour could run a small community. Heat from such a system would also damage the cables’ protective sheathing.

      Reply
  3. I really appreciate this easy to find and easy to read explanation of what’s happening on the bridges. Thanks for following up on so many comments too. I’m glad the ministry puts resources into making this accessible.

    Reply
    • Hi there Paul – thanks for your message. Bridges aren’t closed solely to clear cables. Other extreme weather events can cause unsafe driving conditions, despite our best efforts. When we do close these structures for cable clearing only the outside lanes on the bridges are closed proactively to protect any travellers from falling snow and ice. Hope this helps clarify. Safe travels.

      Reply
  4. Hi!
    How much does each collar weigh?
    Have there been times when a collar has been stopped mid cable? If so do you send another cable down to knock it forward?

    Reply
    • Hi again Bobbi-Jo,

      Here’s what we heard: The chains/collars they drop weigh approx. 25 pounds each, they’re pretty heavy duty. They do sometimes get stopped mid cable by snow/ice build up, when that occurs more chains are dropped to dislodge them and send the bundle down. Hope this information is helpful. Safe travels.

      Reply
  5. This is just unacceptable. You can explain away all you rush but in today’s world of fixes knowing from previous years this should have been dealt with. The re touting if traffic to both Massey tunnel and the already overburdened Patullo is simply disastrous. People have appointments to get to re covid shots or planes to catch to say the least. Fix the damn situation

    Reply
    • That was a very frank comment. I hope Frank applies for a job with Tranbc so he can make the world a better place with his endless wisdom.

      Reply
    • Independent comment – It is not an easy fix for sure. It is a fundamental design problem that was either missed or not considered relevant enough versus the cost of the bridge 2 column versus 4 column support. In other words run the cable stays could have been run vertical instead of crossing all traffic lanes as they do on the Port Mann bridge. Regardless even vertical cable stay designs using a four column instead of two column design like the Alex Fraser bridge pose problems with wind gusts releasing trapped ice on the cables. Trace heating the cable stays would be an enormous retrofit issue and not necessarily 100% successful. An improvement on the manual cleaning method of dropping heavy rings is likely the only choice that can be made A review of oil pipeline cleaning “pig” technology which travel through O&G lines scouring the inside might be a direction worth looking in to using ROV technology.

      Reply
  6. Those rope-access technicians must have nerves of steel to be up that high. I would never be able to ascend to such a height without passing out!

    Kudos to them for keeping the roads open and as safe as possible.

    Reply
    • You are right David. The irony is that we feel safe inside an airplane at 33000 feet, but I think the relativity is that we would not feel as safe if we are the wing! The RAT guys are inside the columns at the top I would think, but there is till that visual perspective to overcome of looking down at height from an open unprotected position

      Reply
  7. Why are you closing HOV lanes for winter maintenance on Dec 22 when it’s 6 degrees with no snow? Couldn’t this work be done at night to minimize traffic interruptions?

    Reply
    • Good morning Eric,

      Thanks for your comment. – thanks for your comment. Lane closures have been in place at the Port Mann Bridge (particularly EB HOV) for reloading. As a safety precaution, we must temporarily close the outside bridge lanes closest to the cables when dropping and reloading the cable collars. In the Port Mann’s case, these are the HOV lanes.

      For reloading, we choose a time when lane closures will have a minimum impact to traffic. However, we don’t have as much flexibility when choosing when to release the collars because it depends largely on the forecast and current weather conditions.

      Depending on the snow accumulation on the bridge deck during the closure, our maintenance contractor may need to plow before we can safely reopen the lanes to regular traffic.

      Here’s a link to our blog outlining the work: https://www.tranbc.ca/2019/03/05/winter-safety-on-alex-fraser-and-port-mann-bridges-explained/

      Reply
  8. Hello!

    We captured some video of the RATS working on the Port Mann Bridge yesterday (February 15, 2021) while doing traffic reports for Global News. The images are very cool and I’d like to share them with the technicians if possible. Shoot me an email and I’ll send them over!

    Thanks,
    Tim

    Reply
    • Hi Wally – thanks for your comment. The risk of falling ice and snow on the bridges – even the Alex Fraser, which is more than 30 years old –  is relatively new. Most years, very little snow accumulates on the cables, or the majority of snow is light and blows off before accumulating enough to pose a threat. In fact, the three temporary closures that happened in the winter of 2016-17 were the very first on the Alex Fraser due to snow/ice forming on the cables.

      Sometimes, a combination of factors can lead to the build up of snow and ice:  the type of snow, temperatures fluctuating around freezing and making the snow wet and heavy, a high range of temperatures that quickly heats the cables, as well as wind direction.

      But with these cable collar systems in place, we are in a much better positions to contend with the conditions nature throws at us.

      After each weather event, we compile a post-storm review to discuss areas of improvements and implement measures to prevent similar situations from reoccurring. And we’re constantly investigating new technologies/innovations to improve snow and ice operations.

      Reply
    • Good morning Franck – thanks for your question. We’ve sent it to our bridge engineering group and will let you know what we hear back.

      Reply
    • Hello Franck – we’ve received a document from our engineering group outlining the suppliers, which we are sending to the email address you have provided here. Hope it’s helpful!

      Reply
  9. You don’t have to heat the whole cable, may be running a small heating element around the cable will keep the temp up to melt the snow.

    Reply
    • Hi there Kan – thanks for your message. Unfortunately, heating only a portion of the cables might allow ice/snow build up on those portions of the cable not being heated, not the end result we are working towards.

      Reply
    • Hi there – thanks for your comment. Unpredictable changes in the weather conditions on site challenged the mitigation measures in place (including the collar system on both bridges). Further, high winds also led to shedding slush to fall into all travel lanes at rates faster than the collar system could operate in to clear the same accumulations safely. A certain set of factors can lead to snow and ice accumulating on the cables: the type of snow, temperatures fluctuating around freezing and making the snow wet and heavy, a high range of temperatures that quickly heats the cables, as well as wind direction.

      Reply
  10. I am looking for a technical paper published by MOTI in 2015: Port Mann Bridge Stay Cable Snow & Ice Removal and Ice Management Program – Technical Summary Paper. Please let me know where I can find it.

    Reply
    • Hello again Kim,

      We are sorry to say that at this time we do not have a technical paper for public distribution.
      Many of the components of the system have numerous pending patents and intellectual property rights, which prohibit us from sharing it publicly.
      We hope that this helps to clarify. If there is anything else we can do, please let us know.

      Reply