Interchange Build Opens Path to ’Treasure Valley’

Thu March 09, 2006 - Midwest Edition
Dawn Weinberger

The Idaho Transportation Department has known about the inadequacies of the highway between Boise and Nampa for nearly 20 years.

In 1987, the agency held its first public meeting on the issue, but funding problems caused delays in getting started.

Finally, a solution is in sight. Last August, the ITD, in partnership with general contractor Central Paving, started work on a $40 million road construction project (90 percent from dedicated federal funds, along with a 10 percent state match) that will significantly reduce congestion and boost Nampa’s retail economy.

Coined the Karcher Interchange project, the result will be a brand-new interchange, including entrance and exit ramps of off Interstate-84 into Nampa at Karcher Road, providing direct access to state highway Idaho 55.

Other features include new bridges — one over the Union Pacific Railroad tracks, one over Indian Creek and a large I-84 overpass.

Crews will also resurface adjoining roadways and add bike, pedestrian and traffic lanes along with additional lanes traffic signals. If all goes well, the new interchange will open by this November.

“Karcher has a lot of heavy traffic, and there is a train yard just to the east,” said Ryan Ward, project manager for Central Paving. “The trains stop a lot and cause huge delays. This will ease a lot of congestion.”

Some retail stores have already laid stake on vacant land next to the forthcoming interchange, including Costco and Target. Jack Sparks, ITD’s project manager for the Karcher Interchange, said several smaller retailers and at least five restaurants are also considering the location for new stores.

“(Currently, it is) just vacant agricultural land,” Sparks said. “They would not have had access to it without (the new interchange).”

At least a quarter of a million people reside in the Boise/Nampa area, known as “Treasure Valley” to locals, and this undoubtedly means the new interchange will get a lot of use.

Sparks said the state’s traffic projections indicate that about 80,000 cars, each direction, will use the interchange every day by 2026.

Idaho considered several other locations for the new interchange, but chose Karcher Road because it would create the most direct route and avoid sending trucks through downtown Nampa and nearby Caldwell.

And while the original design was a simple diamond interchange, state officials realized there was a need for a westbound loop as well so the project grew significantly into its current configuration.

Central Paving is working with about 25 subcontractors on the 375-acre project, and many of the key subs are local to Boise, including Concrete Placing (for the bridge concrete work), Masco Inc. (for piping), Power Plus (electrical) and Hillside Landscaping.

Materials include more than 100 pre-stressed concrete girders and 51,854 cu. yds. (32,000 cu m) of concrete for the five bridges, 804,687 tons (730,000 t) of import granular borrow, 392,385 cu. yds. (300,000 cu m) of on-sight excavation, 116,845 tons (106,000 t) of road base, 2,600 tons (2,359 t)of rock cap and 60,627 tons (55,000 t) of asphalt paving.

In addition, the interchange will feature landscaping with sprinkler irrigation, an irrigation pond and well, curb gutter sidewalks, retaining walls, and a total of 4,600 trees and shrubs. Pipe work will include waterlines, a pressurized sanitary sewer, storm drainage and a gravity sanitary sewer.

Equipment-wise, Central Paving is using two Link-Belt HC218 cranes, one HC138, and a Delmag D3 pilehammer for the bridge and roadwork. For earthwork, crews are using a Caterpillar 140H and 140G motorgraders, but their main piece of equipment is the 14H motorgrader with GPS capability is the main piece of equipment.

“We have the entire project modeled in 3D,” said Ward. “The 14H has a computer and can go anywhere on the site and see a picture of what it is supposed to look like. This makes it fun and …makes it easier to control. This is new for us on this project and we will keep using it. It is valuable.”

But despite access to such innovative equipment — along with dedicated workers and a supportive community — the project is not without obstacles. First and foremost, less-than-perfect soil, he said.

“It all has to be monitored using geotech sensors, ground water pressure sensors and movement sensors to make sure the ground is maintaining stability. It’s just not the best soil to build on,” he explained, adding that crews can only fill two feet of embankment soil per day, and bridge work cannot begin until the embankments are finished. Which leads to Ward’s next challenge: timing.

“We have a really tight and accelerated schedule,” he said, adding that it has been difficult to predict when various aspects will be completed, in part because of the aforementioned soil issues, as well as working around sensitive environmental wetlands and dealing with construction delays caused by the train’s schedule.

“But the overall benefits to the community are …worth the cost of accelerating.” CEG