The Arizona Department of Transportation (ADOT) has many priorities across a complex transportation network that boasts nearly 7,000 lane miles and currently requires an estimated $53.3 billion in capital expenditures through 2040. Right now, one key focus is the $129 million reconstruction of the I-10 and Ruthrauff Road interchange in northwest Tucson, Arizona, along with other related improvements.

“ADOT is building the project to improve safety and increase capacity along a key corridor that serves the growing Tucson region. When completed, the project will add an additional lane in each direction of I-10 in the project area while providing more through-lanes and turning lanes where Ruthrauff Road/El Camino del Cerro crosses the highway,” explains Daniel Casmer, Senior Resident Engineer at ADOT’s Southcentral District. These infrastructure upgrades are part of a series of projects designed to increase capacity on I-10 between Ruthrauff and Ina roads.

Currently, passing trains stop all traffic on Ruthrauff Road, which causes backups onto I-10. In the new configuration, traffic on Ruthrauff Road will pass over the railroad and I-10, eliminating the at-grade railroad crossing. “By building an overpass above the Union Pacific Railroad (UPRR), the new interchange will eliminate the need for drivers to stop for the more than 40 trains that pass through the area each day,” Casmer adds.

In November 2019, ADOT awarded a $79 million construction contract to prime contractor Sundt Construction, Inc. (Sundt), one of four companies that bid on the project.

“ADOT is utilizing an A+B contracting method on this project. The Department chose to utilize this contracting method to incentivize an aggressive construction schedule and to minimize the time that the Ruthrauff Road traffic interchange would be closed to traffic,” Casmer says. He notes that Sundt bid both a construction fee and a time component for the project, which includes an early completion incentive in the contract that will pay the contractor $31,500 per day for finishing the project up to 40 days sooner than the contractor’s specified completion date. The maximum available incentive is $1.26 million.

In addition to the $79 million allocated toward construction, another $50 million is being used for project design, project management, right-of-way acquisitions, utility relocations, public outreach, environmental mitigations, and various other project elements. “WSP was the lead design firm on the project and they worked closely with ADOT staff to develop a comprehensive package of plans and specifications for the project,” Casmer notes.

The I-10/Ruthrauff Road interchange project has been under construction since January 2020.

Substantial completion is anticipated for the end of 2021, with the Ruthrauff Road overpass opening to traffic by fall 2021 and interchange ramps opening later in the year.

The project is divided into three major phases of construction; currently, crews are focused on Phase 2. Key elements across the entirety of the project consist of: lowering I-10 to go beneath Ruthrauff Road/El Camino del Cerro; raising Ruthrauff Road/El Camino del Cerro to go over Davis Avenue/Highway Drive, the Union Pacific Railroad, and I-10; widening I-10 to four lanes in each direction; widening Ruthrauff Road/El Camino del Cerro to two lanes in each direction; and reconstructing the I-10 frontage roads to connect to the elevated Ruthrauff Road/El Camino del Cerro.

To accommodate the nearly two-year construction effort, Ruthrauff Road has been closed at I-10 in Tucson, but remains open east of I-10, as does El Camino del Cerro west of the freeway. During the closure, drivers who normally use Ruthrauff Road have the option to use Prince, Sunset, or Orange Grove roads to access I-10. The interstate will remain open, with various traffic shifts occurring across the course of the project.

In March 2020, I-10 westbound traffic was shifted to the westbound frontage road and eastbound traffic was moved to the freeway’s westbound lanes, allowing crews to demolish the eastbound overpass and rebuild a portion of I-10.

“Demolition of the eastbound I-10 bridge over Ruthrauff Road/El Camino del Cerro took about four days to complete,” Casmer comments. After finishing eastbound I-10 mainline construction in November 2020, crews shifted westbound I-10 traffic to the new eastbound I-10 pavement, which will allow for the demolition and reconstruction of the westbound I-10 mainline.

“The Department expects that the El Camino del Cerro/Ruthrauff Road overpass bridge and the UPRR overpass bridge will be completed and open to traffic across I-10 by mid-July 2021,” he adds. “The westbound I-10 mainline reconstruction will be completed in August 2021, and the Department expects substantial completion of the project by early December 2021.”

ADOT is committed to maintaining access to all businesses situated near the workzone area. To achieve this, the eastbound frontage road south of Sunset Road has been converted to a two-way road. The section of Chuck Huckelberry Loop that passes through the project limits remains open as well. This popular urban trail system extends more than 130 miles across Arizona and connects parks, trailheads, bus and bike routes, hotels, restaurants, and retail and entertainment areas.

The relocation of existing utilities proved to be one of the most challenging aspects of the interchange reconstruction effort. Early in design stages, project team members coordinated with each utility to iron out all the relocation details.

“The design team arranged the relocation schedules so that utility companies were not relocating facilities in the same areas at the same time,” Casmer says. “Once construction started, ADOT and the prime contractor, Sundt Construction, held weekly utility meetings with all utility companies so that the contractor’s project schedule and work locations could be coordinated with the relocation efforts of the utility companies. There were no delays to the schedule caused by utility companies and only a handful of minor conflicts were ever realized.”

Maintaining the existing drainage systems also proved cumbersome. “The drainage in the project area flows from east to west across the I-10 corridor. There are existing underground storm drain pipes that handle the current flows that also need to be maintained throughout construction; unfortunately, these pipes are not structurally strong enough to handle the increased loading that will be placed upon them when the new embankment fills and bridge structures are constructed,” Casmer explains.

In response, the design team specified a fiberglass reinforced plastic (FRP) strengthening method, making it possible for parts of the existing storm drain system to remain in use during and after construction. Casmer adds, “This allowed acceleration of the project schedule and saved the project on removal and reconstruction costs.”

Another project innovation is the use of 3-D/4-D visualization methods to communicate the construction sequence. In addition to submitting and maintaining a monthly critical path method (CPM) schedule, the contractor had to develop a 3-D model of the existing and proposed project features as well as a 4-D element presenting key design features in a time-scaled appearance of model elements/objects.

Casmer comments, “Sundt Construction has utilized their staff to produce cutting-edge visual representations of the project to assist in communicating the construction sequence, avoiding existing and design-feature conflicts, and assisting in the maintenance of traffic throughout the project.”

Also of note, this project is part of the Regional Transportation Authority’s (RTA’s) 20-year roadway improvement plan, managed by the Pima Association of Governments. As of March 2020, more than 860 RTA projects had been successfully delivered as part of an overarching goal to widen roadways, expand transit services, improve safety, enhance the environment, and boost economic vitality. The current RTA plan includes 35 roadway corridor projects; as of June 2020, 15 of then had been finalized and 10 others were either partially completed or under construction.

In addition to improving traffic operations, the I-10/Ruthrauff Road interchange project provides an opportunity to honor the work of one of Tucson’s most revered engineers. John “Mos” Ruthrauff, who is known for transforming the city’s dirt roads to paved streets as chief engineer from 1912-1917, will be featured in the artwork planned for one of the concrete overpass walls along I-10. The artistic design will also reflect the history of the community by including a map of Tucson and mountains.

• 1.1 million cubic yards of dirtwork
• 150,000 square feet of MSE retaining walls
• 139,000 square yards of concrete pavement
• 78,000 tons of asphalt pavement
• 2,500 linear feet of drilled shaft foundations

Photos courtesy of the Arizona Department of Transportation