The Canyon Lake Bridge, which sits a few miles west of Tortilla Flat along the State Route 88 Apache Trail, owes its existence to construction of a dam.

In the early 1920s, as the Mormon Flat Dam neared completion, the Salt River Valley Water Users’ Association  was tasked with building a new road and two new bridges. One of the bridges became the Canyon Lake Bridge.

The bridge was designed and built with relative speed, beginning in September 1924 and finishing in February 1925. The bridge has functioned in place since, with the only modification being a replacement of the original deck with a steel grid deck.

This one-lane bridge has what’s called a Camelback truss, an arched top with five sections that looks like a camel’s back from afar. This design not only distributes stress efficiently, it allows less material to be used. A similar design was used for bridges atop Gillespie Dam and Walnut Canyon. (The black and white photo shows the bridge as it appeared in 2003.)

The Canyon Lake Bridge is an integral part of the Apache Trail, and continues carrying traffic on one of Arizona’s most scenic roads.

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Arizona's highways feature more than 8,500 bridges ranging from wee to grand. Whether or not a highway trip takes you across Pinto Creek Bridge on US 60, Navajo Bridge on US 89A or Glen Canyon Bridge on US 89, you're almost certain to benefit from one of our bridges. 

Arizona has an enviable record for the condition of state highway bridges. Some of that has to do with the relative youth of our infrastructure, but it also has a lot to do with the work of ADOT team members like David Benton, our State Bridge Engineer. 

David joins On the Road With ADOT this week to share how his team looks out for the health of Arizona's bridges. Listen to him visit with host Doug Nintzel, and may come away with an appreciation for not just for that historic SR 88 trust bridge at Canyon Lake and what goes into keeping it in good condition. 

You can subscribe to episodes of On the Road with ADOT through Apple Podcasts and Spotify. You also can find episodes at azdot.gov/Podcast and featured in ADOT Blog posts.

Around 3,000 people gathered Oct. 23, 1990, to dedicate Roosevelt Lake Bridge on State Route 188, and none had a better seat than 9-year-old Carmelle Malkovich of Claypool. 

Malkovich got to join Governor Rose Mofford on the first trip across the bridge by winning a Globe-Miami Chamber of Commerce raffle. That’s her in the photo above, riding in a 1915 electric car flanked by Governor Mofford and a representative of Arizona Public Service.

Thanks to LinkedIn, I recently caught up with Malkovich, who today is Director of Communications for Dignity Health in Arizona and Nevada. She graciously shared her memories of that day, including the way Governor Mofford put her at ease during an event that drew numerous VIPs and reporters. 

“She couldn’t have been any kinder and nicer to me,” Malkovich said.

Governor Mofford shared her fondness for Malkovich’s grandparents, whom she knew because the governor too hailed from the Globe-Miami area. The two also had a shared Slavic heritage – Croatian for Mofford and Serbian for Malkovich. 

“She did very much inspire me,” Malkovich said. “She really demonstrated that day how a young Slavic girl from a small copper-mining town like her can really achieve anything.” 

And then there was the magnificent 1,080-foot-long arch carrying State Route 188 over Roosevelt Lake. Roosevelt Lake Bridge remains the nation’s longest two-lane, single-span steel through arch bridge.

“I remember seeing this huge, beautiful bridge,” Malkovich said. “I remember watching the progress of the bridge being built, but I don’t think I realized at the time just how big and how beautiful it was going to be.”

With Malkovich helping cut the ribbon to open the bridge, Governor Mofford and others celebrated a far more efficient path for SR 188 at Roosevelt Lake and between the Gila County communities of Globe and Payson. Traffic had been winding down to and then crossing one direction at a time atop the original Roosevelt Dam, which was soon to be replaced by a larger dam when the bridge was dedicated. 

Governor Mofford told the crowd: “People in Gila County will no longer feel separated by northern and southern sections.” 

Even at such a young age, Malkovich knew she was doing something very special. “I remember my dad telling me how historic this was and to really be honored to be a part of it,” she said. The photo above still hangs in her parents’ house in Claypool. 

The experience made Malkovich a bit of a celebrity in her hometown. The owner of a local Mexican restaurant made her a jacket – blue, like the bridge’s arch – with “First to Cross the Bridge” on the back in pink letters.

“I’ll go home to my parents and I still get stopped by people in town who will say, ‘I remember when you were the first to cross the bridge,’” Malkovich said. 

About a decade after the dedication, Malkovich got to experience the bridge’s benefits, along with a heavy dose of nostalgia, when she crossed it on her way to and from Northern Arizona University.

“It really connected us to Roosevelt, to Payson and to northern Arizona,” she said. 

It's been a few years since Malkovich has visited the bridge, but it continues to impress her long after that first trip across. 

“It’s just beautiful, and the landscape out there is gorgeous too,” she said. “It fits just perfectly.”

During the early days of Arizona’s roads, many local streets carried highway traffic, some of which were transcontinental highways. 

A great example is the 17th Avenue Underpass in downtown Phoenix, near the Arizona State Capitol. This structure once carried the tracks of the Southern Pacific Railroad over US 80. 

US 80 was a major transcontinental highway that ran from San Diego, Calif., all the way to Savannah, Ga. In Arizona, US 80 traveled from Yuma to the Arizona-New Mexico state line by way of Phoenix. At 17th Avenue, US 80 left Buckeye Road, heading north past the capitol to Van Buren Street.

The underpass itself was part of a Depression-era movement to eliminate on-grade railroad crossings. The structure was designed and completed in 1935 by ADOT’s predecessor, the Arizona Highway Department. It’s a concrete rigid frame with two 25-foot spans over the northbound and southbound lanes of the street. The deck was 80 feet wide to accommodate the multi-track railyards, with smaller openings for pedestrian sidewalks at both sides. The structure also incorporated decorative touches, like slotted concrete guardrails.

Interstates 8 and 10 gradually replaced US 80 and 17th Avenue now carries local traffic. The 17th Avenue Underpass is a well-preserved example of bridge construction of the time, as well as a reminder of what was an important transcontinental highway.

Constructing roads requires plenty of planning: Determining the location, design and materials are all important. One key element that might go unnoticed by many, though, is gaining an understanding of the soil and ground upon which the road will be built.

For that, we introduce you to ADOT’s Soils and Aggregates Lab.

“Soil tests are done before every project,” said David Coronado, a transportation engineering specialist. “The tests help engineers to understand the soil's properties, stability, and bearing capacity. It also helps engineers choose the best materials to use to ensure a durable and long lasting structure and roadway performance.”

Prior to the construction phase of a project, ADOT’s Soils and Aggregates Lab runs tests on soil samples taken from the project area. These tests can involve very simple procedures, like rolling a ball of clay back and forth by hand until it crumbles, which is essentially rolling out the moisture until it loses its integrity and can no longer hold together. Other tests are more complicated, like the aforementioned counterpart involving mixing a fine grained soil and using a mechanical device which must adhere to a set of specifications and criteria.

One common soil test is T89, a counterpart to T90, which together determine the soil's plasticity. According to the American Association of Highway Transportation Officials(AASHTO) technical regulations, a technician mixes a soil sample with 8-10/15-20 milliliters of distilled water until it is completely absorbed, further adding 1-3 millimeters until it becomes viscous. The resulting mixture is then placed into the brass dish of a liquid-limit device and spread carefully to conform to the dish's shape while meeting the regulated 10 millimeter thickness criteria.

A groove is cut vertically into the soil separating two sides, with a clear visible brass dividing line. The liquid-limit device is turned on, subjecting the dish to shocks, which is lifting it 10 millimeters in height and dropping it onto the base causing both sides from the split to close in on each other. Once both sides touch at approximately half of an inch at the required 25 shocks, a soil sample is taken by performing a horizontal cut across the soil where both sides meet, placing it in a glass jar and recording the wet weight before putting it in the oven to dry until achieving a constant weight. After the dry weight is recorded, the calculation for the percent moisture is done.

Coronado says Arizona has diverse soil types, including sandy and gravelly soils. “The Phoenix metropolitan area mostly consists of sandy soils, as well as a mixture of sand, silt, and clay,” he says. “In northern Arizona, such as Flagstaff, heavy clays are more prevalent.”

As for what type of soil is best to build roads on: “Ideally, free-draining but with enough clay for cohesion and stabilization, but not so high a clay content that the water is prevented from draining,” Coronado said. “Granular soils with fines are best. High clay materials affect drainage and are highly absorbent, which also leads to issues with swelling and shrinkage thus affecting the road's integrity and are not suitable to build on. Also, very silty soils are not ideal as they can be prone to collapse when water is introduced.”

So next time you see the dirt beside the road, know it was thoroughly tested before that road was built.

 

 

 

 

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Several concrete bridge girders have been placed throughout the I-10 Broadway Curve Improvement Project and by the project’s end, dozens of these girders will have been placed within the project area. 

Bridge girders are the beams that support the deck portion of a bridge which is the part of the bridge that motorists drive on. 

Many of the concrete girders for the I-10 Broadway Curve Improvement Project are made in the south Phoenix area, off 19th Avenue and Lower Buckeye Road.

When workers begin construction of concrete girders, they first place rebar within the girder formwork which helps to enhance the structural strength of the concrete bridge girders. Tons of rebar strands can be used for just one girder depending on the height and length of the girder that’s being constructed. 

Once the rebar is in place, the form cast that shapes the concrete girder is placed around the rebar. Concrete is then poured into the girder form cast. Workers then level and smooth the surface of the concrete and let it cure or dry for two to three days.  

When curing is complete, the form cast is removed from around the concrete and the new bridge girder is revealed. Workers then conduct inspections on each girder, making sure they meet the necessary design and safety standards needed. 

View the Behind the Scenes video on concrete bridge girders below.

Learn more about the I-10 Broadway Curve Improvement Project at I10broadwaycurve.com and download the free project mobile app called The Curve.