"Rust" is the new "steel," says RIDOT (Update, with quote)

Sakonnet River Bridge
Weathered steel Sakonnet River Bridge, via RI DOT.

Yesterday's Sakonnet Times and Tuesday's Newport Daily News reported on a presentation by RIDOT on a new look for the Sakonnet River Bridge: to save $2.9M, it would be constructed of so-called "weathering steel," an alloy designed to weather to a naturally rusty-brown finish. Unlike regular steel which must be painted (because the rust eats the surface and exposes more material) the corrosion of weathering steels is self-limiting — once a surface patina of rust is built up, it protects the good steel beneath.

According to the Sakonnet Times, attendees at the meeting last Monday in Tiverton where this was unveiled raised questions about the choice, including Tiverton Council President Louise Durfee who is quoted as saying, "What assurance can you give us that we are not left with an ugly brown bridge?" State Rep Joe Amaral expressed concerns when RIDOT representatives cited similar spans in New Jersey as examples. "Every time you mention New Jersey, I get more and more nervous about what this bridge is going to look like," he is quoted as saying.

With a little research on the Google, I turned up a good amount of info (see links, below) and while I'll admit this isn't the prettiest material for a bridge, it's probably not completely out of whack, given the color palette of sand and water it would be seen against. My concerns go more to the engineering and maintenance aspects.

Insurance company investigator and amateur linguist Ben Whorf long ago noted what he called the "empty drum" problem. Workers around full containers of gasoline, he found, tend to be cautious. It was around those labelled "Empty" that they became careless, tossing cigarette butts with predictable results. Of course, it is these empty containers that are the most dangerous, since liquid gasoline is not flammable, but the residual vapor is.

So here we have a proposal to replace a bridge which fell apart, arguably because of insufficient maintenance. And we're going to replace it with a bridge that looks — that is designed to look — like it is rusting? Does that not strike you as a big freaking "empty drum?" An invitation to miss potential problems?

Want to go straight to the horse's mouth? Today at noon, the Providence Journal is hosting a live web chat with RIDOT Director Jerome Williams. While I have the utmost respect for Mr. Williams (read my translation of his letter in reply to my complaint about East Main Road) and the professional capabilities of his department, I have already submitted a couple of questions, and we'll see if they get answered:

Mr. Williams: While I think all Rhode Islanders are thrilled to see the beautiful IWay bridge, the recent proposed changes to the Sakonnet River bridge are troubling. Unlike the beautiful blue IWay, the towns of Portsmouth and Tiverton are getting a rusty-brown weathered steel structure.

Two questions: What is the ambient chloride level at the Sakonnet Bridge location and what wil its effect be on the lifespan of the proposed steel?

And a follow-up: Given that the problems with the existing bridge arose because of maintenance issues, do you think it is prudent to propose a material which makes it difficult to visually tell the difference between "good" weathering and dangerous corrosion?

I'll post an update this afternoon.

Update: Jerome Williams, RI DOT Director, responds:
"The proposal to use weathering steel was generated from a team that included national engineering experts along with research staff from the Federal Highway Administration (FHWA). Weathering steel has been used successfully in many bridges in similar environments. The color is not a rusty brown but will be brown in color. The bridge is being designed for at least a 75 year lifespan and will carry bridge inspections based on FHWA standards. While this is a change from the original design the bridge originally was estimated at $125 million. The latest estiate on the original design was $215 million. Given the infrastructure needs of the State we conducted a value engineering process with national experts to maintain the usability and size of the bridge while identifying options to reduce the cost without sacrificing safety. The result of this was a $39 million reduction in cost. These savings can be used on other transportation infrastructure needs the State has. We do not have the ambient chloride level with us at this time. Please contact our Customer Service office at 401-222-2450. Thank you."

Err...did he actually answer the question? Got voicemail at the DOT. Update to come on that...

Sakonnet River Bridge page
Uncoated Weathering Steel in Structures US DOT Federal Highway Administration
Wikipedia entry on Weathering Steel. Has a nice photo showing color.


The problem with the existing Sakonnet River bridge stems from more than just inattention to appropriate periodic maintenance. The problems began right off the bat when the thing was engineered with NO STRUCTURAL REDUNDANCIES. I don't think it is legal to build a bridge like that today -- there's always redundant support trusses (at least in a truss type bridge). It's because of the lack of redundant support structure design that today the weight limits are imposed.

The reason it was built with no structural redundancy back then was -- to save money. And, the reason being given now to go to weathered steel? To save money.


Hi, Lije...
I'm not necessarily questioning the use of weathered steel — it may be perfectly appropriate. But it doesn't instill confidence for the DOT to replace a bridge that's rusted out with one that starts rusting before they finish building it.

There's something almost, well, Microsoft-like about it. If you have a problem with something in your first release, in the second release you don't fix it, you just call it a feature...


I am unsure how anyone found weathering steel to be a good material for this bridge. Weathering steel is not stainless, its designed to maintain a protective petina like copper. However, this petina is not suitable in places where water, mainly SALTWATER may accumulate.

A bridge constructed of a material that is basicly intolerant of water and corrosion-catalysing substances, i.e. salt from the water it is directly above, or from winter snow conditions, in this area should be viewed as obscenely irresponsible.

Saving costs is one thing, but "fixing" a problem with a bridge that is more prone to failure under the same conditions is rediculous.

A quick look at the current Sakonnet river bridge gives the bridge's testimoney of lack of maintenance and downright abuse. Sections of the bridge are visibly bent from traffic accidents. The paint to rust ratio seems to be an even 1:1.

Weathering steel requires prudent inspection and maintenance, two things that this state clearly lacks. A quick look at the Mt. Hope bridge construction incompetancies can display this.

Why build a bridge that is clearly prone to failure? Weathering steel is merely pushing the problem 20 years ahead., a problem that could potentially leave many people injured or dead.

"We can't solve problems using the same method of thinking we used to create them." -Albert Einstein.

Hi, rhetor...
Thanks for your comment, and welcome. I share your concerns about weathering steel. Not being an engineer, I have to go by the research I've been able to do, and what I've seen is that in places like Japan, where they have been using weathering steel since the 1960s, there are very stringent standards for exposure to salt (hence my question to Williams about the ambient chloride level).

I also find Mr. Williams reassurances about the FHA inspections, well, less than reassuring, since this was the same government entity which didn't even know we had any at-risk steel deck truss bridges back in August following the Minneapolis disaster. (See the ProJo story. Here's the money quote:

The Federal Highway Administration’s tally of 756 of them counts 6 in Connecticut and 19 in Massachusetts, but lists zero for Rhode Island, and the state Department of Transportation said there weren’t any in Rhode Island.

Yesterday, the DOT acknowledged that there is such a bridge in the state, and a prominent one at that: the Sakonnet River Bridge that carries Route 24 from Tiverton to Portsmouth.

Yeah, these are the national engineering experts who Williams says helped design this bridge and the inspection regimen. But hey, anybody can misplace a bridge or two. You can be sure they're more careful about strict standards for material. Really.


Let's make sure we have the facts here before we make a judgement or a decison. The key here is not how the bridge looks - we can spend a lot of extra money on non-stuctural aestetics on this bridge. But the real bottom line is bridge safety, maintenance and life. If we can be assured the best of these without the need for some periodic maintenance (that costs money - like painting) that, by itself, sounds like a good thing. I undersand that we may not trust the engineers after the debacle of a design on the original bridge. But we must put trust in sound engineering design backed up by real proof of concept in the field. There surely is no assurance that a painted bridge will have any less corrossion problems than a weathering steel bridge. We just have to hold DOT's feet to the fire to provide us the right data on Sakonnet conditions (like salt conditions) and proof of similar designs in similar environments that have shown the test of time. (We should also ask the questoin as to why the new I-WAY bridge did not use this design to save money - there must have been a reason that may provide some insight) But, let's not get focused on one aspect of the bridge without looking at the total design with ALL the supporting data. Can we PLEASE put emotion aside. Emotion is not a measure of sound bridge design. Forcelfully requesting full data and analysis IS. What we want is the BEST Bridge for the money.

Thanks for your comment. As I said in my original post, I may not think it's the prettiest material, but I'm more interested in the right answer. I asked Director Williams about chloride levels, and left a message at DOT as he suggested, and I will post the response. The problem with weathering steel and salt water, as I understand it from the research I cited, is that it prevents the protective patina from building up, leading to a situation with accelerated corrosion.

I also contacted one of my sf-writer friends who is an engineer and who has built some big things in the salt and humidity of Florida. His take was that weathering steel could certainly be an acceptable material, but he strongly suggested, as you did, remaining vigilant with DOT and their contractors.

As you suggest, the decision should be based on science and safety. And there's my core concern. As I said in my original post, the "empty drum" syndrome scares the heck out of me. Weathering steel structures are not maintenance-free; according to everything I read, they do require periodic inspections and occasional cleaning and care (especially at joints and in any structural areas where corrosive material could build up). I want to know the experience base RIDOT has with weathering steel, and how they are going to guarantee a rigorous regimen with trained inspectors and scrupulous oversight.

I think we know the answer to why the Iway bridge didn't use this. It's in Providence. And a rusty brown bridge wouldn't have gotten on "Mega Movers." But I will stick to the facts about the material; if it's right, it's right. I'm not going to let bitterness and snark make the decision. I am, however, free to let them know that *we* know that any other explanation is a PR handwave.