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Tuesday, September 25, 1990 - Page updated at 12:00 AM

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S-Curves On I-405 To Be Set Straight -- First, Water Pipes Will Be Rerouted

Long-suffering motorists on Interstate 405 can expect more slowdowns next year when the state Department of Transportation begins work to straighten out the

S-curves.

The department began advertising last week for bids to relocate three pipes that cross under the S-curves. Work on the 300-foot-long pipes, which carry water from the Cedar River watershed to Seattle households, will start in January.

Bob Josephson, project development director for the Transportation Department, said the major work on the 1.7-mile stretch, a dangerous part of the highway known for congestion and traffic accidents, will begin after the pipeline is moved. The S-curves are so known because of their shape as they bend around a section of the freeway in Renton.

In addition to making the route safer, highway engineers are building car- and bus-pooling lanes in both directions. Also being added are separate lanes on each side of the highway, called collector distributors, to connect with the off-and on-ramps to the Maple Valley Highway.

But the $70 million project won't be done until 1994 at the earliest.

During the construction, motorists can expect slowdowns and periods of congestion, with lots of shifting of lanes, Josephson said. But usually two lanes will be kept open in each direction, and the majority of the most disruptive work will be done at night.

Meanwhile, the 2-year-old effort to finish the I-405 segment from Tukwila to south Renton is nearing completion. The high-occupancy-vehicle (HOV) lanes on the section are scheduled to open in three weeks.

Reconstruction of the rutted and cracking three-mile stretch of highway, which carries more than 100,000 vehicles a day, has been called one of the single most complex Washington state road projects ever attempted.

``It's the first time we've ever totally reconstructed a freeway,'' said Terry Paananen, construction project engineer. ``We've gone through about 270 change orders.''

Because of the complexities and mistakes in the planning, the cost of redoing the section has jumped to $42 million - almost

$4 million beyond the $38.5 million bid submitted by general contractor Kiewit Pacific Co. The federal government is paying for 90 percent of the project, the state 10 percent. The money for the additional cost is coming from both the federal and state governments.

Paananen said crews still must seal cracks, apply asphalt paving, install light poles, and dress up slopes along the roadway, which will be separated by permanent concrete barriers.

The Transportation Department will let two separate contracts for the upcoming S-curves work. The first one, estimated at about $20 million, will be to lower the pipe along the east side of the highway on Renton Hill so the roadway can be moved over about 100 feet and cut into the hillside.

Twenty-six houses that the state purchased on the hill must be torn down or moved before tunnels for the new pipe can be drilled. Eighteen of the houses already have been razed.

Paananen said the elimination of the S-curves will be done under a separate contract starting next spring. The cost of that job, which includes building a new bridge over the Cedar River, is estimated at about $50 million.

``It's not going to be a straight shot, but it's going to be nothing compared to what's there now,'' said John Johnson, design engineer on the I-405 project. ``There will still be a slight curve as you go through the city of Renton.''

South End motorists and bus commuters can also look forward to having HOV lanes on Interstate 5 by next June. A bid opening is scheduled next week on a $3-$4 million project to construct transit-car-pool lanes on I-5 from Tukwila to Federal Way.

Charles Cook, an assistant construction engineer for District 1, said pressure to reduce highway congestion helped speed up the HOV lanes project on I-5.

The southbound HOV lane will run four miles from the Tukwila interchange to South 221st Street, and the northbound HOV lane will begin at South 204th Street and end at South 272nd Street, a distance of about five miles.

In other significant South End transportation projects, stoplights are scheduled to be installed at three different intersections next year on Highway 18: 208th Avenue Southeast, Southeast 312th Way, and Southeast 296th Street near the entrance to Seattle International Raceway.

And except for some mopping up, work is almost done on improvements at the Highway 18 and South 320th Street interchanges along I-5 near Federal Way.

Paving of the old northbound

I-5 on-ramp - for westbound traffic on South 320th - starts Saturday, said project engineer Bob Ginter.

Copyright (c) 1990 Seattle Times Company, All Rights Reserved.

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