For decades, cars and trucks have jockeyed on and off Interstate 5 at a dangerous freeway interchange in Federal Way called "the Triangle."
“It’s one of the most notorious chokepoints in South King County,” said state Department of Transportation spokesman Mike Murphy.
For thousands of drivers, the days of precarious weaving on outmoded cloverleaf ramps are now numbered.
Work started this week on a $112 million project to end the weaving and improve the interchange at I-5 and state Route 18 by adding two flyover ramps. Crews started putting their job-site trailers in place Monday.
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The project won’t be completed for more than 2½ years, in spring 2013.
Linda and Carl Holden of Tacoma battle the weaving to get off of I-5 for doctors’ appointments in Federal Way. They say the improvements are long overdue.
“It’s like shuffling a deck of cards,” Linda Holden said. “It’s a mess.”
Lisa Eichman of Federal Way gets on and off I-5 at the interchange going to and from Seattle and Tacoma. Vehicles jockey to avoid each other as they enter and exit via the tightly bunched on-ramps and off - ramps.
“It’s a little scary,” she said. “You have to be so defensive so you don’t get sideswiped.”
Sitting in a Denny’s restaurant in the thick of the congestion at state Route 161 and South 348th Street, the Holdens and Eichman expressed hope the improvements will be worth the wait.
The Triangle is named for the intersection of I-5, Route 18 and Route 161, also called Enchanted Parkway South.
The interchange’s four cloverleaf ramps were considered state-of-the-art design when constructed in the early-1960s. Over time, traffic volumes soared as the population grew, overwhelming the ramps.
“The cloverleaf no longer provides sufficient capacity,” said Aleta Borschowa , project engineer for the Transportation Department.
The DOT website is more direct, calling the cloverleaf design a “freeway relic.”
Cars back up for blocks on South 348th Street getting on and off I-5 and Route 18. More cars enter the tangle from Route 161.
The two flyover ramps will eliminate the weaving of vehicles entering and exiting I-5 by removing two of the four cloverleafs. Reaching as high as 38 feet, the flyover ramps will pass completely over I-5.
The two cloverleafs that remain won’t be next to each other and won’t be on the same side of I-5. That means cars won’t come and go at the same spots on the freeway.
Improving the interchange will cause traffic delays and lane closures. HOV lanes are expected to close after Jan. 1 temporarily for work on bridge supports, Borschowa said.
In the next two weeks, some short-term nighttime closures of some lanes are expected for lane re-striping , she said.
The Transportation Department has seen evidence of homeless camps in the cloverleafs and has started using a heat-sensing camera to make sure no one is in areas to be cleared, Borschowa said.
The work adds to other construction going on this summer along the I-5 corridor – the Route 16/Nalley Valley viaduct project, the Fife I-5 HOV project, and the replacement of worn concrete panels on I-5 in south Pierce and north Thurston counties.
All of the state’s proposed improvements for the Triangle are expected to cost from $215 million to $235 million. But only $112.7 million for the first phase has been funded – mostly from state dollars including gas taxes and some federal money.
In the first phase, crews will:
Build one single-lane flyover ramp to take eastbound traffic from South 348th Street/Route 18 over the freeway and onto I-5 north.
Construct a two-lane flyover ramp to carry westbound vehicles on Route 18 to southbound I-5.
Rebuild ramps from westbound Route 18 to northbound I-5 and from eastbound Route 18 to southbound I-5 for the new flyover ramps.
Construct a new exit ramp connecting the I-5 south flyover ramp to Route 161 at South 359th Street. That’s expected to help ease congestion on South 348th Street.
The Triangle improvements have topped Federal Way’s list of most-needed transportation projects for several years.
The project is important for the city to relieve congestion and enhance economic development, said City Council member Jeanne Burbidge, who’s advocated for the improvements for 10 years.
“It’s gratifying to see it actually begin,” said Burbidge, a member of state and regional transportation boards. “For the city as a whole, it’s huge.”