As the cold winds of December hit Idaho, work on the U.S. 93 Twin Falls Alternate Route project was well into the final phase, right on schedule.
“The concrete roadway is open and the signals are going,” Kimbol Allen, Idaho Transportation Department District 4 resident engineer, said. “We’re just finishing the landscaping. There will be decorative stamped red concrete along the gutters, a sprinkler system and lots of plants – but with the cold temperatures, we may have to wait until spring to plant them.”
But, he added, there’s contract time until March, so even if planting is delayed, they can still finish on schedule.
With a slight note of disappointment in his voice, Allen said they had hoped to finish ahead of schedule, but work was slowed due to weather, extensive utility work and an extreme number of change orders. “We had a lot of change orders – about 40. That adds work and time.”
In some instances, IDT had to redo things that were already completed because the design began eight years ago and the landscape has changed. That required alterations in the plans. Open fields and irrigation systems have been developed in the intervening eight years. In addition, he explained that some things requested during the right-of-way acquisition no longer fit the needs of the city and had to be adjusted.
Allen said the contractor, Western Construction, based in Boise, could have finished early, had it not been for the inordinate amount of change orders. “Our intent was to have the work finished this year.” But even with crews working 10-hour days five days a week, too many change orders prohibited signing off on the work by December. However, Allen expressed reluctance to extend more than just the landscaping into next year served to reign in additional change orders.
Start to Finish
The project encompassed an eight-mi. (12.9 m) stretch of roadway carrying 35,000 cars a day. The two-lane road wasn’t built to handle today’s traffic and the four-way stop signs result in quarter-mile back-ups at rush hour. The new six-lane section through the urban section (and four-lane portion for the next mi.) with traffic signal is expected to better serve the rapidly growing community of nearly 30,000 and 100,000 in the county within 20 mi. of the project.
Intended to initially redirect truck traffic that runs through Twin Falls, Idaho, the new road will eventually become part of U.S. 93. Allen said that played a significant role in the plans – and the change orders. “We worked hard with the utility companies to look ahead,” Allen said. Projections for the future anticipate eight signals in the two-mi. corridor; IDT is prepared, having already installed the conduit for it. “The State paid to add fiber optic conduit throughout the corridor for future growth without undoing all the concrete work and disrupting traffic flow.”
That concrete work put the project over budget, but Allen considers it worth the price. Intersection approaches were widened from 20 ft. to 64 ft. (6.1 to 19.5 m)– full street approaches. IDT extended the pavement 1,312.3 ft. (400 m). “That was the biggest expense; it was about a $1 million change order,” he said. “It needed to be done. The plant mix at the major intersection was failing. We’d been in there three times in the last five years. As long as we were doing this project, we wanted to get it done right. It added a lot of work, but the contractor was able to save some time.”
Over its life cycle, Allen emphasized that the concrete should pay for itself and save maintenance costs. Concrete was chosen because, for now, it served as an alternate truck route. The concrete would hold up better under heavy truck traffic than asphalt. When the road becomes a state highway, it will see even more traffic.
Until then, IDT kept in mind that the area is an urban setting, densely populated with businesses along the main corridor and a subdivision on one leg. Therefore, IDT borrowed Minn. standards and techniques to provide a quieter highway by incorporating a carpet drag finishing process.
“The American Concrete Paving Association determined that this process produces significant noise reduction over 35 mph,” Allen stated.
The speed limit through the corridor is 45 mph (72 kph). The process involves dragging an Astroturf-style material longitudinally across freshly poured concrete, instead of running a tining machine behind a slip form paver.
“The transverse tining we usually do provides good skid resistance, so we were interested in how the finer texture [provided by carpet dragging] would handle snow. After testing, we got good numbers; we’re happy,” Allen said.
The paving sub-contractor, Concrete Placing Co. of Boise, earned nearly $1 million in QCQA bonuses for materials and workmanship. The bonuses included $250,000 for meeting uniform thickness requirements, $250,000 for “smoothness bonuses” and $125,000 for superior asphalt content and for asphalt patch work. The final cost of the project has not been tallied yet. The original bid was $19 million. Allen reckons $23 million has been paid to date, but the tab is not closed.
Once the final sum is calculated, it will cover the cost of moving more than 50,000 tons (45,659 t) of base rock and 25,000 cu. yds. (19,114 cu m) of concrete rock from two different locations, and removing 40,000 cu. yds. (30,582 cu m) of dirt. Allen said crews rebuilt the road base with aggregate, using an assortment of D8 Cats, Cat 14-H blades, rollers, pavers and dowel baskets because they didn’t have a dowel bar inserter machine. They also installed, for the first time in Idaho, MMFX steel reinforcement, which is less prone to corrosion than standard rebar.
Additional work entailed building a combination bike tunnel-canal that had a voided slab concrete girder bridge with a 39.3-ft. (12-m.) span and trapezoidal channel for the canal, which replaces 13-by-16.4-ft. (4 by 5 m) arch culvert. A dividing concrete wall separated water from the tunnel. Allen noted that walls of the divider and abutment had an aesthetically pleasing textured surface. “We used form liners to get that nice rock texture.”
Community Project
Despite the experimentation with new processes and materials, Allen considered the highlight of the project to be the community’s involvement and support. “The community was really good to us. For nearly a year and a half, they had put up with construction with very few complaints – mostly only about the intersections and traffic shifts. We used temporary, portable signals that didn’t have the sensor control, often lines of traffic would be waiting at a red light when there was no cross traffic. It tested some patience.”
Allen explained that IDT appreciated the freedom that local businesses and the city allowed them when it came to road closures. “We presented alternatives for shorter timelines with more closures. They let us know what they considered acceptable delays.” In some cases, he said the community countered with such good ideas, IDT adopted them. “We showed them our suggestions; they came back with strategic changes and alternative staging ideas that helped keep us on schedule.”
During construction, a cross-section of businesses including banks, restaurants, gas stations and retail shops faced inconvenience. However, an example of the cooperation between local businesses and IDT occurred in the rebuilding of approaches to a Hertz car dealer. The Hertz management notified the contractor that they had scheduled an off-site car sale for a week, allowing crews to power through the work without impedance, without worrying about keeping access open to the car dealer.
Allen considered the most important part of the project “our communication with local businesses.” Presumably, the community considers the most important part of the project its conclusion, and joined forces with IDT and the contractor to ensure it ended on time. CEG
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