The nuts and bolts of bridge repair

After being closed for minor damage in January, the bridge near Flying Diamond Ranch has been repaired and is open to traffic.

Workers from Simon Contractors had been removing rivets and angle irons and replacing cords on the bridge, which crosses the Encampment River on County Road 680, since March 26. Repair work was completed the morning of April 2, and the bridge was open to traffic later that day at noon.

The 1940s-built bridge, constructed to withstand eight tons with a couple of axles and 15 tons with several axles, was compromised by an overweight vehicle and closed in January. Carbon County Road and Bridge Supervisor Bill Nation said the riveted portion of the two-inch by two-inch angle on the bridge had broken, and two previously repaired bottom cords were replaced during repair work.

"They replaced the two bottom cords on the downstream side, so they consisted of 30-feet each and a 2x2 angle," Nation said. "The most recent breaks were on the east side. The guys pretty much worked straight through, got it done and did a really good job. The deadline was May 1, which they certainly beat, and one of our major goals was to accomplish that and get it done as quick as possible."

Nation said an extremely heavy load traveling over the bridge, combined with a below-zero temperature, is what caused the damage. He said that when very cold iron and an extreme weight is added, it compromises the bridge.

"It was a super cold day and a super heavy load of some sort went across there, and it cracked through the rivet holes," Nation said. "We shut the bridge down for safety, and started the process for emergency repair. It was January when it broke again after it was repaired, and that's when I shut it down."

Since the bridge support had been damaged last year, Nation said it was time to replace it with new structural steel on portions of the bottom of the bridge. He said it was important to replace what has been injured or damaged in the last 25 or 30 years.

"When we looked at the bridge and decided to go through the repair process, we decided to replace everything that had been repaired," Nation said. "We thought that if we're going to shut it down and do it, let's overdo it and take it back to an as new or better condition."

The previous repair, done by Nation in August, put the bridge down to a 3-ton limit. After the most recent repair, Nation said the bridge is now back to its full load limit of 8 tons, 15 tons and 15 tons, depending on the amount of axles going across the bridge.

"The limits of the bridge now are back to what they were before, with eight tons, 15 and 15, and I think that will serve the traveling public in that area very well again if they stay within the limits of that weight restriction," he said. "When it cracked before, I fixed it and limited the weight capacity to three tons, but then after that it cracked again in a different location and through the old rivet holes. That's when we decided the old repair wasn't enough, and in this cold extreme weather, we thought we should shut it down and repair it."

Nation said Simon Contractors, headquartered in Cheyenne, was the contracting firm with the lowest bid for the project.

"We had a couple of contractors bid for it, and Simon was the one that got the low bid, got right on the project and got it finished," he said. "We repaired it before and then it cracked, and then the last time it cracked we decided to shut the bridge down."

Nation also worked with PMPC, who were the project's lead engineer; Martin/Martin, which worked on the structural engineer design; and the Wyoming Department of Transportation's Pat Pearson in Cheyenne. Nation said the nearly 75-year-old bridge should last another 70 years, before any serious repair construction or complete replacement is needed.

Now posted on either side of the bridge are two five mile per hour speed limit signs, which Nation said would help keep travelers from going too fast over the bridge. Nation suggested placing other 5 mph signs on other county bridges.

"There was never a posted speed limit on any of these particular bridges, but I think it would be wise to take up that activity through resolution and the county commissioners," he said. "It's a decision they will make, but it will be my recommendation for the six other bridges in the county."