"Rust" is the new "steel," says RIDOT (Update, with quote)
|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
PERFORMANCE OF WEATHERING STEEL IN HIGHWAY BRIDGES American Iron and Steel Institute
Wikipedia entry on Weathering Steel. Has a nice photo showing color.