WYE Interchange Reconstruction Project
Location: At the intersection of I-84 and I-184 in Boise.
History: The original interchange was completed by the Idaho Transportation Department in December 1969 and, at the time, was about a mile outside the Boise City Limits. The interchange was designed to comfortably carry about 33,000 vehicles per day. In 1998, the average daily traffic was about 92,000 vehicles per day. The WYE Interchange is being rebuilt to comfortably carry about 120,000 vehicles per day, the projected traffic level in 2020. The project is being constructed in two stages at a total cost of about $80 million. Stage 1 is in progress and will be finished in 2001. Stage 2 will start in 2001 and last about two more years. In completely rebuilding the WYE, the transportation department is still keeping two lanes of traffic open in all directions on the interstates, the same level of service available to motorists before construction started. When finished, the WYE will feature three lanes of traffic in all directions along with new ramps for increased capacity and added safety.
Interesting points: One of the most obvious impacts of an area’s growth is increased traffic. As roadways become clogged with traffic, safety and efficiency are challenged. The WYE interchange Reconstruction Project commenced on March 1, 1999, in response to these problems. Stage 1 is highlighted by a three-lane flyover structure (already open) that eliminates the left-hand exit and left-side merge for traffic coming from downtown or leaving the mall area and heading east on Interstate 84. In addition, Interstate 184 (the Connector) will be widened from four lanes to six between Curtis Road and Franklin Road. Construction for Stage 2 is scheduled to begin in early 2001 and will take two years to finish, giving the overall project an estimated completion date in late 2002. Stage 2 of the project will add lanes and ramps to improve safety, access, and efficiency.
The flyover bridge is designed to withstand the maximum credible earthquake for the Boise area without suffering any significant damage.
Statistics: This $73.2 million project will add lanes and ramps to improve safety and efficiency at the busy interchange. Stage one will cost approximately $48.2 million. Stage two is projected at $25 million
The new flyover bridge is 823 feet long and 58.2 feet wide, carrying three lanes of traffic. The curved bridge is supported in part by reinforcing steel (tendons) that weigh 1.3 million pounds and total 421,000 feet (about 80 miles) in length.
The road surfaces are being paved with concrete. There will be 80,000 cubic yards of concrete used in Stage 1, which will cover 220,000 square yards one foot deep.
To prepare for the work, 330,000 cubic yards of material was moved, 16,600 feet of storm sewer pipe buried, and 227,000 tons of base material (mostly gravel) put in place.
Six bridges are being built that will become the overpasses for the Connector above Franklin and Cole roads. They will total 3.5 million pounds of steel and weigh 2,135 tons.
For more information about the project, check the transportation department’s project web site at www2.state.id.us/wye.