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Project Evaluation: I-5, S 317th Street HOV Direct Access
Federal Way, King County
WSDOT and Sound Transit are building new on- and off-ramps for carpools, vanpools and buses in the I-5 median at South 317th Street. The ramps will lead to a new overpass above southbound I-5, directly connecting I-5 carpool lanes to Sound Transit's Federal Way Transit Center. When work is complete, carpool lane users won't have to cross four lanes of traffic to get on and off the freeway at the crowded South 320th Street interchange. The direct access ramps will increase the speed and reliability of carpools and transit, and improve traffic flow and safety for all drivers. Crews are also extending the southbound carpool lane to South 320th Street and replacing and improving I-5 pavement.
Construction Summary
A combination of plan errors and contractor mistakes progressively delayed the project and increased costs.
We discovered that the height difference between northbound and southbound I-5 at the north end of the new HOV ramps is seven feet instead of the expected four feet. We needed to eliminate an approximately 610 foot section of median barrier and replace it with a retaining wall. We believe that more accurate survey data during project design could help prevent this situation in the future.
There were also conflicts between retaining walls and drainage systems. To correct these conflicts we lowered the retaining wall two feet to accommodate drainage structures. A contractor survey error placed the steel plates that temporarily hold back earth during construction beyond the new retaining wall footing limit, which required redesign of the wall footing. In addition, the contractor did not order enough wall panels and wire screens to hold wall panels in place and had to reorder them.
This series of problems delayed this project from a scheduled October opening date to January 2006 and will likely increase costs. The new opening date coincides with the opening of Sound Transit’s new Federal Way Transit Center, which is adjacent to the new freeway overpass.
We worked effectively with ICON Materials, our contractor, to develop solutions to minimize costs and complete the work quickly. To expedite the work we made a portion of the wall and some traffic barriers off site. We also requested that the traffic barrier on top of the wall be constructed using a machine to form the barrier instead of forming the barrier by hand. We authorized work on Saturdays and extended work hours, with WSDOT picking up the premium time costs.
We estimate the final project cost will be
10 to 15 percent over the contractor’s bid amount. We are currently evaluating and negotiating additional payments to the contractor.
Contact information
Contractor:
Icon Materials, Tukwila
WSDOT Contact:
John Chi, Project Engineer
(206) 768-9002
ChiJ@wsdot.wa.gov
For more information: www.wsdot.wa.gov/Projects/i5/S317th_DirectAccess
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