Shattuck Avenue will reopen sometime in fall 2009, a year behind schedule because of delays in designing “sacrificial beams” that will protect a new railroad bridge from too-tall vehicles.
The cost for the sacrificial beams and warning systems also will double, from about $50,000 to $100,000.
The new bridge carrying the Burlington Northern Santa Fe tracks over Shattuck was one of three railroad bridges downtown that the city of Renton replaced in cooperation with Burlington Northern.
Work on the other two railroad bridges, at Rainier Avenue and Hardie Avenue, was finished earlier this year after intermittent road closures.
The plan all along was to keep Shattuck Avenue closed at the bridge near South Fourth Place to accommodate work on a new storm interceptor designed to ease flooding on Rainier Avenue.
The goal was to have the sacrificial beams designed and built this year and the road reopened. Now, with winter weather approaching, work won’t get done until next year, according to Bob Hanson, the city’s design engineering supervisor.
“The requirement is that we protect the bridge from a collision by a vehicle,” said Hanson.
But what makes that task “troublesome” is that Burlington Northern doesn’t have a standard for such sacrificial beams, including the type of the vehicle the beams must stop, he said.
Part of the issue has been a foundation for the beams, Hanson said. The beams must be strong enough to stop a vehicle going at a “reasonable” speed, he said.
Burlington Northern can place conditions on streets going over or under railroad tracks because the street typically is crossing a railroad-owned right of way.
In some cases, the issue isn’t as complicated because of the clearance under a bridge, such as the 16 1/2 feet at the Rainier Avenue Bridge.
The Shattuck bridge has an 8-foot clearance. One of the conditions placed on the Shattuck bridge is a limit on the size of the vehicle allowed under the bridge. Also of concern are vehicles with bike racks or hauling large boats.
“The forces that are brought to bear on the (sacrificial) beam can be huge,” said Hanson. The city doesn’t expect to stop large vehicles, but the beam has to be able to stop one if it comes through, he said.
“And that’s where it gets sticky,” he said.
The “sacrificial beams” are required on either side of the bridge, along with a warning system. To accommodate traffic under the bridge, the city is looking at the approach to the bridge as more like a driveway than an extension of the street, Hanson said.
The speed limit will be set at 5 mph under the bridge when it reopens. “We are treating it as if you are entering a parking garage,” he said.
Shattuck has always been an important alternate route through downtown Renton, especially in the case of major backups on Rainier Avenue.
But, it was never intended for large semis – the new bridge replaced an ancient one barely big enough to accommodate one vehicle at a time.
The city is pressing to reopen the street because it is important to local drivers – and to emergency vehicles – and retains its value as an alternative to Rainier Avenue, Hanson said.
The final design is subject to a review by Burlington Northern.
Dean A. Radford can be reached at 425-255-3484, ext. 5050, or at dean.radford@rentonreporter.com
