Talking Michigan Transportation

The challenges and perils of falling ice on the Mackinac Bridge

April 07, 2022 Season 4 Episode 99
Talking Michigan Transportation
The challenges and perils of falling ice on the Mackinac Bridge
Show Notes Transcript

On this week’s Talking Michigan Transportation podcast, questions and explanations about the increasing frequency of melting ice falling from the Mackinac Bridge cables, creating hazards for motorists and the need to close the bridge for many hours at a time. This video illustrates the danger. 

As this record shows, closures because of falling ice have happened with increasing frequency. 

First, Matt Chynoweth, chief bridge engineer at the Michigan Department of Transportation, explains what causes the big chunks of ice to come crashing down and the challenges other bridge operators across the country and world have had in managing the problem. 

In Toledo, the Ohio Department of Transportation has been forced to close the Veterans Glass City Skyway over the Maumee River because of falling ice.  

Chynoweth also explains the challenge in striking a balance between the cost of delays to travelers and the expensive solutions being discussed elsewhere. 

Later, James Lake, MDOT North Region media relations representative who also supports the Mackinac Bridge Authority, talks about his efforts in explaining the issues to media outlets and social media users.

Podcast photo: Ice builds up on the iconic green Mackinac Bridge cables.


Jeff Cranson: Welcome to the Talking Michigan Transportation podcast. I'm Jeff Cranson. 


Cranson: Thank you again for tuning in to this week's Talking Michigan Transportation podcast. I am pleased to have with me today a repeat visitor and one of my favorites, Matt Chynoweth, who is the chief engineer, chief bridge engineer, at MDOT and has a bank of knowledge about all things related to building and maintaining bridges and is in close touch with his counterparts from the various boards and committees that he serves on around the country and into the nation. So we're going to talk today about the perils of the falling ice on the Mackinac Bridge, why this seems to be an increasing phenomenon, and what can be done about it. Later, I’ll be talking with James Lake, who is the MDOT media relations representative in the North region and has been dealing with a lot of the media questions about the Mackinac Bridge closures because of this ice falling and has done an outstanding job on Twitter answering questions and explaining this. But first, Matt, thank you for taking time to be here. 

Matt Chynoweth: Yeah, thank you, Jeff, thanks for having me again. 

Cranson: So, talk first, if you could, just offer some basic explanation of what we're seeing on the Mackinac Bridge, and goes on with other bridges, obviously, but why the ice melts and big chunks come crashing down. 

Chynoweth: Yeah, so for the Mackinac Bridge, you have two main, I guess, accumulators of ice, right. Just like on your house that collects snow or anything like that. So you have the towers, which have a lot of vertical surface. They also have a lot of horizontal surface. And then you also have the main cables. Now, the main cables are circular, and water will hit the cables, and then it will run, and then it will eventually freeze. And keep in mind, the towers themselves, the top of the towers, are 300 some feet above the deck level. So, temperatures and wind are much different, those conditions are much different, than they are at deck level, and then at the level of the straits. And so, through changes in temperature, obviously, water is going to fall, you're going to have humidity in the air, you're going to have snow. And that creates what's called ice accretion, which is a big issue on long span bridges in general in cold climates. We're dealing with it right now in the design of the Gordie Howe bridge. There are many Canadian long span bridges where they're considering retrofits for ice mitigation. It's happening in Ohio; it's happening at all the bridges in Manhattan that are managed by the New York-New Jersey port authority. And so you get this freezing of the water turning into ice. And then, right now, because we're trying, the state is trying, to enter spring, we are still going above and below 32 degrees on a regular basis. And as the elements of the bridge warm, these sheets of ice come off. And this is something that we've been tracking for a number of years. This isn't the first year that it's happened—it's been happening for a while—but typically what we see, especially up that far north, is once that area freezes, it pretty much stays frozen until spring. But what we're seeing right now are these cycles of freeze/thaw, and that's causing the ice to come off in large chunks. 

Cranson: Yeah, so this is not unlike the increased flooding, the deluges, that we're seeing that are overwhelming our pump stations and closing freeways in metro Detroit, or the high water lapping away at roads on our many shorelines. I mean, this is all part of a volatile climate, and I guess people can debate whether the earth is warming, even though science says it is. Those are definitely factors here. So, what we have to do is deal with the reality of that. And this isn't unique to Michigan, so there's speculation that it must be related to, you know, you mentioned the Northern Michigan location, and extreme cold, and the winds in the straits. But you've talked to others in other states and provinces that have wrestled with this, too, and in fact, you mentioned Toledo. That's not a big bridge that people might be familiar with. On I-280 is a cable stay, similar design to the Gordie Howe International Bridge, not a suspension bridge like the Mackinac Bridge. But they've got issues they've had to mitigate, too, right? 

Chynoweth: That’s correct, yeah. From early on, when that bridge was open, the Veteran’s Memorial Skyway there in Toledo, it's I-280 over the Maumee River, they had instances where they had to close that bridge because of ice coming off of the stay cables and the tower. And they put forth a study to look at ways that they can mitigate ice. And we did something similar years ago on Mackinac, we looked at a bunch of different things, sort of some industry practices, some innovative things that we could do. One of them was to try to heat the towers. Well, keep in mind, those towers on the Mackinac Bridge, there's two of them, and each of them is the equivalent of a 30-story building. So, think about the infrastructure that would be needed to just heat those towers just enough—not 70 degrees, but just enough to prevent ice from forming. There was discussion about running a small current through the towers. That has its own issues because straight current can cause corrosion.  

Cranson: That one comes up a lot, Matt, as you probably know from all the armchair engineers. That one like, why don't you just run some current through it? 

Chynoweth: Yeah, so that is plausible, and it's been done in the past on smaller scales. Like, for example, that's called cathodic protection, and what it means is you run a current through, and the current has to be strong enough to prevent the corrosion cell from forming. But, when you have a bridge that is all steel like the Mackinac Bridge, that current can go anywhere. And you can create a corrosion cell, which is a huge risk, right. That's why we coat the bridge, that's the way we paint the bridge, is to protect it from corrosion. The other ice mitigation technique is how we shape the elements where water pools. So, for example, on Gordie Howe, the stay cables themselves, the sheathing that we're gonna put on it, has corrugations and it's not perfectly circular, so that when water hits, it descends faster than it would if it were circular. And then these corrugations break up—if there is going to be formations of ice, these corrugations would break up the size, and it would result in smaller pieces of ice that would fall and go unnoticed. We looked at something like that for Mackinac, for the main cables, but again, you have these very large round main cables with the secondary suspender cables coming off at regular intervals. And to put some sort of different shape on that, some sort of sheathing with a different shape, just becomes a very, very difficult and expensive endeavor. So, there are things that we've looked into, it's not like we're just standing by and saying, well, it freezes, that's it. We've looked into certain things, it's just been somewhat cost prohibitive. 

Cranson: So what do you hear from your counterparts? Have you talked to anybody that faces the similar issues with lack of alternatives? I mean, it's not like you can just put a sign up that says Mackinac Bridge closed, seek alternate route. 

Chynoweth: Yeah, so for example, for the New York-New Jersey port authority, they've, just what I’ve explained, they've looked into different types of shapes that can break up the ice and stuff like that. And you know, when you're in downtown Manhattan, you can’t afford to close a bridge, either. So, some of these things are very much on the cutting edge; they're being tested, and they're being tried. Like I mentioned, on the Gordie Howe, we're doing what's called a passive ice mitigation technique, which is the shapes of things, but we also looked at active ice mitigation. And we looked at, okay, what if we had chains or some sort of little robots that could run up and down the stay cables and break up the ice or prevent ice from forming. We also looked at a system, we actually provisioned a system and tested it. And we're not going to build it on the bridge, but the bridge is going to be built such that this could be added later in the bridge's life, where we put rotational motors over at the ends of the cable stays, and it rotates the sheath at a rate of one or two feet per second in rainy and icy conditions to prevent any ice from forming. Again, something like that added significant cost to the project so we decided not to do it, but the infrastructure will be there to if WDBA chooses to do it in the future. 

Cranson: Is there a way to capitalize on drone technology?  

Chynoweth: Well, yeah, there could be, Jeff, but when you're talking on Gordie Howe, we're gonna have 204 stay cables all at different angles, and you'd have to have an army of drones out there. And then what could those drones do, right? Do you put a cutting head on the drone to try to cut ice away? And then, is it possible that something could happen, and you could damage the sheathing that protects the stay cables? There's a lot of technical details that would have to be worked out. 

Cranson: Yeah, that does sound risky. So when you talk about the costs, MDOT officials obviously have a user delay cost model, and folks at the Mackinac Bridge authority certainly know the cost of delays, not to mention the frustration. So how do you balance that against the cost of solutions and the dangers of not closing the bridge? 

Chynoweth: Yeah, I mean, it comes down to what is the true cost of something like this. So there's an initial cost to build it, there's an initial cost to do something. And anything that we do, Jeff, on the Mackinac Bridge, there's nothing that's going to be off the shelf. Everything is going to have to be custom designed, custom built for those elements on the bridge. So, there's the initial cost to build it, but then, now, we've also added something else to the bridge that will affect and use resources for life cycle maintenance. So now, we're going to put a system on the bridge that mitigates ice, however, we're now going to have to maintain that system as well. So without running all of those costs, I couldn't tell you if there's a break-even point in terms of loss of revenue from tolls. But these are, we're talking fairly significant costs, and it is a big deal when the bridge is closed, but for my recollection, I don't believe we had an issue where we had to close the bridge at all last year. We did a couple times the year before, so this seems to be a recurring issue, but not on an annual basis. 

Cranson: Well, and I'll be sure to post the photo in the show notes of the car that had ice crashed through its windshield a couple years back. And if that doesn't convince anybody of the potential dangers, then you're probably never going to win that fight. So real quickly, since news broke this week on bridge bundling, and there's another round of bridges that have been announced, just give us a quick update and overview of where things stand with that program. 

Chynoweth: Sure, so the pilot project, which we've talked about before, which is 19 bridges, that is currently under construction. We have three bridges with active construction going right now, with another two that are going to start soon. And more starting throughout the summer, with a plan to have all of those done by November of this year. So the pilot project is going well. The local agencies that own these bridges that we've been working with have been excellent to work with. The phase two portion, which is the 196 million dollars in CRRSSA funds that was appropriated for, we focused on closed bridges throughout the state. 

Cranson: Will you explain CRRSSA funds? 

Chynoweth: I’m sorry, yeah. So CRRSSA funds are the covid relief funds that came from the federal government to all the states as part of the Cares Act and as part of legislation to deal with covid. And so a significant portion of that came to Michigan, and we were appropriated 196 million for this phase two—we're calling it phase two—of the bridge bundling, which is dealing with closed bridges. Some of these bridges have been closed for a while, and there's no real public need or public use for them anymore. So we are working with local agencies to actually get those removed. And then the other focus is on load restricted bridges, where these bridges may affect the local economy or mobility in that area or access to emergency services. And with this program, we're thinking we can do probably another 60 bridges over the next three years. And so we're hoping by the end of this year, we'll start getting a couple packages on the street for construction. 

Cranson: So this, again, is just to remind people; this is MDOT offering some, both engineering and contracting, expertise to help local road agencies repair and replace their bridges. It creates economies of scale and creates efficiencies and, yeah, it's a real collaborative effort between state and local officials. So far, so good. Thank you, Matt, I appreciate you taking time to talk about that. And next, I'll be back with James Lake to talk about communicating on this bridge ice issue. 

Chynoweth: Thanks, Jeff. 

Cranson: Please stay tuned, we'll be back with more Talking Michigan Transportation right after this. 

Narrator: The Michigan Department of Transportation reminds you that when a vehicle collides with another vehicle, person, or other object, it is a crash, not an accident. By reducing human error, we can prevent crashes and rebuild Michigan roads safely. 

Cranson: We’re back again for our second segment and as advertised, James Lake, who is the North region media relations rep for MDOT, a veteran at communicating about transportation issues. But nobody really had the expertise to take on this relatively new phenomenon. When I say new, we're talking really something that's, within the last 25 years, probably, become an issue, but increasing frequency the past few years. James, Matt Chynoweth, the chief bridge engineer at MDOT, kind of explained the technical parts of this: why it happens, why the ice forms, and melts more often, where in a climate like Northern Michigan it used to just stay frozen basically from November to April. But you dealt with the challenges when this first occurred on your watch a few years back, and now off and on with trying to explain it to media, and especially with trying to explain it to the Twitter universe. Talk about what that's been like. 

James Lake: Well, it's been challenging, but it's certainly something that I’m sympathetic to. I mean, no one, including us, likes to be stuck in traffic, especially when there's no clear idea of how long you'll be stuck. And so as, I mean, that's probably the more new phenomenon; ice has been forming on the Mackinac Bridge, falling resulting in closure. But now we have social media, where we can reach out to people, and they can reach out to us to talk about what's going on during these closures. And certainly during the last four that occurred the end of March and beginning of April here, more and more that's how they're reaching out to us. 

Cranson: That's the good and the bad of social media, isn't it? 

Lake: It is, it is. 

Cranson: So you probably start all your responses with kind of a Bill Clinton, “I feel your pain”. Is that what you do? 

Lake: [laughing] Well, either start them or end them like that. I mean, I was really trying to meet people where they were coming from. Certainly, people were coming to us with some frustration, some anger about how the closure was handled and how we were responding to people. And so, certainly I was responding with sympathy, with information that we had—although limited. And then others were making light of the situation, too, so I tried to respond in kind. We got a lot of maybe joking not joking suggestions for how we might melt the ice, and we rolled with that; I think had some laughs together. And by and large, people were pretty understanding. When we shared information, particularly images videos of what the falling ice looks like out by the towers when it hits that bridge deck, I think we got a lot more understanding of why we needed to close the bridge. 

Cranson: Yeah absolutely, and you've heard my analogy; I equate it to sitting on the tarmac and wondering why the plane's not taking off. And for a long time, the airlines were not very good about updating you and letting you know what's going on. And they've gotten better at it, it goes a long way, it really takes down the temperature when people are just like, okay, now I know what's going, why we're delayed, and what they're trying to do to fix it.  

Lake: Yes, unfortunately in these situations with falling ice, between the announcement of closure and the announcement of reopening, there isn't a lot to share. We can't make accurate predictions as to how long that closure will last, so that's frustrating for people. But we did our best to share regular updates: what bridge staff were doing, sharing temperature information, what the winds were doing out there, just confirming that ice was continuing to fall. And then, both with these last two closures this past Saturday and Sunday, bridge staff were out in fully loaded plow trucks, doing their best to shake the remaining ice loose from the cables. 

Cranson: How effective is that? 

Lake: Well, it depends on the day, and it depends on the other conditions. When they did it on Saturday, they weren't seeing many results. Sunday, which ended up being a little bit warmer, maybe a little bit more sun, it seemed to be quite a bit more effective. So it's one tool, but it has to be supported by the weather conditions that they're seeing in the straits. 

Cranson: So you just have to turn up the sun. 

Lake: Right. I wasn’t able to do that this weekend. 

Cranson: I think you're right for the most part, people get it, but the people that are stuck, they're the ones that you know they're probably not in the laughing mood. So those are the ones that you wish they could all be following the Twitter feed at least and getting at least that much information. There's only so much you can do on the message boards, and if you're not right next to one, you're not going to see that anyway. What do you think going forward—you would advise people to just know maybe that certain times a year, you know, March and April, that this is a phenomena that could be occurring? 

Lake: Right, well, we're gonna do a better job of getting the word out ahead of time to let people know of this possibility in case they weren't aware before. As you say, it's kind of late winter, early spring when we get those thaws during the daytime, re-freezing at night that seems to result in these back-to-back closures. But we're putting together a video right now that shows more of the imagery of falling ice, of the damage that's been done to vehicles over the years: caved in roofs, caved in windshields. And then explaining to people some of the circumstances that go into these falling ice closures. So we can show them that about the same time every year, let them know that this is a possibility. We're also going to, once we're aware that ice is forming on those upper cables and tower components, we're going to start putting out a warning after that happens, so that people are aware that a falling ice closure, while not certain, is likely in the coming days.  

Cranson: Kind of like the conditions are right for a tornado, right? 

Lake: Right, yep. The warning versus watch conditions, the conditions that are right for falling ice closure, and then people can make their own decision as to whether they want to proceed and run the risk of getting stuck, or maybe reschedule their plans if they're flexible.  

Cranson: But I should say, too, that with what's going on with the climate and with the earth and the more volatile weather that we're seeing, that it isn't just March and April. Really, this could occur just about any time between November and April. 

Lake: Yeah, those mid-winter thaws. Because we have, in the past several years, had closures in January, closures in February; so not exclusive to these spring months. 

Cranson: So today's April 7th, how much ice is still up there? 

Lake: Right now, I don't believe there's any, or there isn't any of significance. And usually, the amount of ice that results in the closure, we're talking about a thick coating—somewhere between a quarter of an inch, half an inch, or more—that when it comes down is of significant weight and can damage vehicles. But we've got pictures of chunks of ice that are as big as a loaf of bread, and it's remarkable that they've survived that 300-foot plunge from the top of the towers down to the top of the deck, but they do. And I think we can imagine, like I told a couple of people on Twitter this last weekend, I wouldn't want a seven-pound bag of ice from the gas station to fall on my vehicle from any height, let alone one of these pieces of ice that could potentially weigh hundreds of pounds. 

Cranson: Good analogy, excellent. Well thanks, James, for taking time to explain this and for all your good work communicating with the media, and other people, and especially on the twitter feed over the weekend. I think it's greatly appreciated, and it helps. 

Lake: My pleasure. 


Cranson: Thank you again for listening to this week's edition of the Talking Michigan Transportation podcast. I would like to thank Randy Debler and Corey Petee for engineering this week's podcast. To subscribe, to show notes, and more, go to Apple podcast and search for Talking Michigan Transportation.