If you’ve managed to drive state Highway 500 at St. Johns Boulevard recently without noticing the construction, expect that to change this week. Lane closures and reduced speed limits will make the busy intersection look and feel completely different starting Monday.
The reason: Work is picking up steam on a $48 million project that will eventually send St. Johns Boulevard up and over the highway on a new bridge. The end result will remove the traffic signal there now, and replace it with a freeway-style interchange — allowing the highway to flow freely underneath.
Washington State Department of Transportation planners hope the change will help ease traffic for an area that sees up to 60,000 motorists passing through daily. But for the next year, driving the intersection could be ugly.
To prepare for the construction of the new St. Johns bridge and elevated connector ramps on each side, WSDOT crews will narrow lanes on Highway 500 and reduce the speed limit to 45 mph. St. Johns will be reduced to one lane in each direction — along what’s now the northbound side of the road — with a reduced speed limit of 25 mph. Left turns will be prohibited on both corridors.
Delays and congestion at the intersection could last for twelve months, according to WSDOT.
By the time the project is finished in late 2012 or early 2013, St. Johns will be back to the same alignment it follows now.
“Just 20 feet higher,” said WSDOT project manager Lori Figone.
Construction on the project began last spring under lead contractor Tapani Underground Inc. Crews have spent much of that time doing everything they can to shorten the worst of the traffic impacts, said WSDOT spokeswoman Heidi Sause. Ramp supports are already partially built.
By early next year, workers will be constructing three bridges simultaneously — the main St. Johns bridge, plus two connecting ramps to the east that span Burnt Bridge Creek. Ramps on the other side of St. Johns won’t cross the creek, and will be supported by rock, dirt and fill.
Crews don’t plan to remove the existing St. Johns Boulevard. Much of it will simply be buried by dirt under the approach to the new bridge. But before that happens, workers will dig out a lot of the ground above a culvert that sends Burnt Bridge Creek under St. Johns. A “cap” above the culvert will allow the structure to hold up under the weight of the new bridge approach that’s about to be put on top of it.
Some of the dirt dug out from under St. Johns will be hauled away, Sause said. But much of it will end up elsewhere on the site to save on costs, she said.
“Any time we can use it on-site, it’s a benefit,’ Sause said.
The project’s setting creates a unique set of challenges, Figone said. In addition to the high traffic volume, crews are also carefully working around the creek, a popular trail nearby and large power lines. The orientation of the land itself also presents some obstacles, she said.
“One of the biggest complications for the contractor is just how steep the slopes are around here,” Figone said. In many cases, “you can’t just drive a piece of equipment in there.”
Some equipment will work from the edges of a now-narrowed Highway 500. The Burnt Bridge Creek Trail was detoured earlier this year. And while earlier plans called for the complete closure of St. Johns Boulevard — to the dismay of some residents and businesses — it will now be partially rerouted to at least keep traffic moving through the area.
That doesn’t mean there won’t be delays. WSDOT has encouraged drivers to plan ahead, or use a different route if they can.
Eric Florip: 360-735-4541; www.twitter.com/col_enviro; firstname.lastname@example.org.