Monday, December 15, 2014

Why we spend millions to repaint bridges

The North Fork Lewis River Bridges
after their $12 million paint jobs.
By Tamara Hellman

Painting a bridge is a lot different than painting your house. Sure, it’s nice to get a touch-up to improve your home’s curb appeal. But for a bridge, it’s more than just making it look pretty.

Painting helps preserve the roughly 3,500 bridges we manage around the state. The paint helps protect our bridges from the elements so everyone can use them for a longer period of time.

Here’s an example. We just finished painting the North Fork Lewis River Bridges on I-5 south of Woodland. Both spans carry 65,000 vehicles a day on our state’s primary north-south interstate highway.

Decades of wear, including rust and
peeling paint, on one of the bridges’ trusses.
If we didn’t paint these bridges, they would rust and deteriorate faster. The last time the North Fork Lewis River Bridges received a fresh coat, it was 1990. Since then, its “Cascade Green” color has worn off in spots and rust has formed on sections of the steel. Without a proper touch-up, the rust would spread and deteriorate the steel structure, causing it to weaken. Eventually, the bridge would not be able to carry the load it once did. As a result, freight haulers would have to make long detours, putting a crimp on interstate commerce.

We try our best to paint bridges every couple decades to ensure they’re properly protected. While it’s cheaper to paint a bridge than it is to build a new one, it still costs a decent amount of money. For the North Fork Lewis River Bridges, the final bill was around $12 million– about 20 percent under budget, paid for by both state-gas-tax and federal-preservation funds.

Why so much?
Several factors contribute to the cost of a bridge-painting project, two of which are the most important:

1. Keeping people safe
With any project, we need to keep traffic moving while ensuring the safety of both the people traveling through our work zones and the crews working in them. A good portion of the cost covers safety measures, such as temporary barriers, traffic control and scaffolding. Lane closures are expensive and limit the times when contractors can do their work.  If we have to close lanes, we do it mostly at night or on weekends, when people travel less frequently. Temporary barriers also provide a safe work area for crews, as well as safe lanes of travel for drivers. Scaffolding is used so workers can get access to high and low points on the bridges, and cable systems are used to protect the workers from falling. Keeping everyone safe is our number-one priority.

Barriers provide safe lanes of travel for drivers and a safe place for crews to work.

2. Keeping the environment safe
We work to be good stewards of the environment– not simply because it’s required as part of the permitting process, but because it’s the right thing to do. During the North Fork Lewis River Bridges repainting project, contractor crews installed a containment system of tarps, collection tubes and vacuum systems to prevent the many layers of deteriorated paint, rust and other debris from falling into the river. They sandblasted the old lead-based paint off the steel and cleaned the rust and dirt off the bridge. The environmental-protection systems collected all the material so crews could dispose of it properly. This was done in sections to keep the metal from exposure to the elements for too long, preventing new rust from forming before each section could be painted.

Environmental protection
systems prevent debris
from falling in the river.
The end result
The new coats of paint are expected to help preserve the bridges for about 25 years. We maximize the life of the paint by cleaning our bridges between paintings to remove debris that can make them deteriorate faster.

We have a significant backlog of steel bridges that need to be repainted throughout our highway system. With less funding and the list of bridges growing, we have to make some tough decisions on prioritizing which ones get painted next. We are constantly exploring practical ways to maintain and preserve our bridges, and we do it with safety, cost savings and the environment in mind.


Anonymous said...

Wondering why the Nooksack River bridge on I5 didn't get finished. Months of work, appears only ⅔ finished at best.

WSDOT said...

Anonymous - You're right! The Nooksack Bridges painting project is partially complete. Crews are restricted to work only at night, because the bridges are two lanes. Also, the work is weather dependent. Most of the painting on the southbound bridge was completed this fall and we anticipate the project to be completed ahead of schedule, in the summer of 2015. You can read more about the project on our project page:

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