When ADOT builds a new bridge, our top priority is to make sure the gigantic mass of steel and concrete stays right where we build it.

But that won’t be the case with a new bridge we’re constructing on State Route 79 in Florence, because this bridge is designed to move.

Or more precisely, slide. 

This new bridge’s mobile nature will be only temporary, however, as part of an innovative method of constructing a new bridge by assembling the new structure’s components next to the old bridge and then sliding them into place.

The process begins by constructing new bridge piers in the bed of the Gila River. The piers will be extra wide so the new structure’s components can be built in halves on either side of the old bridge. Once the new segments are complete, crews will tear out the old bridge and slide each half of the new structure where the existing bridge now stands.

ADOT has slid new bridges into the place of old ones before, including a 2020 project to replace the Fourth Street bridge over Interstate 40 in Flagstaff.

By sliding a bridge into place, ADOT can keep traffic moving with minimal delays during construction. Both lanes of traffic will remain open during the SR 79 project, except for two weekends when the bridge halves are slid into place. On both weekends, a temporary traffic signal will restrict traffic to one lane in each direction.

The existing bridge was built in 1957-58 and has reached the end of its useful life. When ADOT began planning for a replacement, engineers had several options for its construction. 

One common method involves building the new bridge next to the old one, which was the case when ADOT replaced the Pinto Creek bridge on US 60 between Globe and Miami. That option was ruled out for the Florence bridge project because of the additional cost to buy right-of-way and shift the road to the new structure. 

Another approach is replacing the bridge one half at a time, which is how ADOT replaced the SR 77 bridge in Winkelman. That option would have meant only one lane of traffic would remain open during the project, which would have led to excessive delays because SR 79 carries significantly more traffic than the highway through Winkelman.

No matter what method ADOT chooses to replace a bridge, our goal is to maintain a safe and reliable transportation system while minimizing delays for motorists. In the case of the project in Florence, drivers should look for a reduced speed limit in the work zone and watch for traffic alerts when the bridge slides require two weekends of lane restrictions. 

Learn more about the project and stay up to date by checking out the SR 79 bridge replacement project page. 

As you drive through the Verde Valley on Interstate 17, you won’t notice any construction work as you cross over the Verde River. But down below the highway, crews are working in the river bed to reinforce the footings of the Verde River Bridges to prevent erosion.

But there’s more going on than just construction work. Because that work is taking place in an area that is home to several endangered species, including snakes, birds and fish, biology teams work alongside construction crews to find and relocate these species.

This team of biomonitors from Northern Arizona University is led by Dr. Erika Nowak, assistant research professor in the Center for Adaptable Western Landscapes and director of the NAU Gartersnake Research Program.

Their purpose is to ensure that these species are protected as best they can be, given the construction activities. These species include the northern Mexican gartersnake, birds such as the yellow-billed cuckoo and the southwestern willow flycatcher, and endangered fish like the razorback sucker and spikedace.

Specifically, the team trains construction workers and project team members on identifying these species and what to do if they come across one. They will also watch construction activity and help ensure that any species are safely removed out of harm’s way. 

Because the work is in the river bed, crews built earthen bypass channels to contain river flow so crews can work outside of the area safely. For this team, it means that the biomonitors will remove all fish from pools that need to be filled in and rescue fish stranded during river moving events.

So what does the biology team do with these captured creatures? The team will identify the species as well as photograph and measure them. The northern Mexican gartersnakes are microchipped. And then, they are released. Fish and amphibian tadpoles are released into the Verde River downstream of the construction area.

“The relocation distance varies, but it’s typically about 50-150 yards from the capture point. We don’t want to release the animals too far away, as moving them out of their home range can disrupt their behavior, cause them to become disoriented, and thus more likely to die,” Nowak said.

You can learn more about the NAU biology team led by Dr. Nowak and their research on northern Mexican gartersnakes here.

The project to protect the I-17 Verde River Bridge footings is set to be completed later this spring. Learn more about the project itself here.

November is Historic Bridge Awareness Month. There's no official celebration here in Arizona, but we'd like to highlight some a few of our favorite bridges in Arizona.

First, is the "other" Salt River Bridge. It's carried State Route 288 traffic across the Salt River in Gila County since 1920. Even more impressive, it's done that without any significant changes. Although it's considered a remote crossing, the SR 288 Salt River Bridge is important in state bridge history because it's the earliest documented example of a bridge constructed by the Bureau of Public Roads in Arizona.

Another of our favorites is the Chevelon Creek Bridge in Navajo County. The deep, rocky canyon over Chevelon Creek, east of Winslow, cuts across the Colorado Plateau, the broad, relatively flat piece of topography that makes up most of northeast Arizona. This bridge carried mainline traffic on the Santa Fe Highway across that creek and was an important crossing for one of the nation's earliest transcontinental routes. Today, it carries relatively sparse local traffic, but is still remembered as one of the State of Arizona's first highway structures.

The Bylas Bridge also has historical importance. Located on US 70, it was the longest historical bridge over the Gila River. After its completion in 1957, the Bylas Bridge carried mainline traffic on US 70 for decades, essentially unchanged. Unfortunately, by the early 2010s it could no longer support modern traffic needs and was demolished in 2013 after a new bridge was built.

It may not look like much from afar ... but the Gillespie Dam bridge is a survivor in one of the most notorious bridge-problem areas in Arizona.

Building on the Gila River has always been a challenge. The floodplain is a very turbulent one, and the Antelope Hill bridge (the original site for a bridge across the river) sustained severe damage time and again from floods. In addition, continual flood damage to the newly-established Ocean-to-Ocean Highway led state officials to reroute the road between Wellton and Arlington (south of the river, through Gila Bend). However, since Arlington was north of the river, a new crossing had to be built.

After a few years of problems and false starts (including a flood that washed away much of the construction equipment and materials), the Gillespie Dam Bridge was opened for traffic in 1927. It remained part of the old U.S. 80 mainline until 1956, when the road was re-aligned. It now functions as a county bridge and is part of Historic U.S. Route 80.

The Gillespie Dam bridge was one of the longest vehicular structures in Arizona when it was originally built; it was also the only steel bridge across the Gila River, and one of two remaining bridges with multi-span vehicular through trusses. The Gila River Flood of 1993 only caused some support piers to settle (because of its design and concrete support piers sunk in bedrock). It's one of the most important examples of early bridge construction in Arizona.

 

We are so excited to announce that for the second year in a row, an ADOT project is in line for a national award from America’s Transportation Awards! In the transportation industry, this is a BIG deal! 

The Fourth Street Bridge replacement project in Flagstaff, which won a regional award in the 2021 America’s Transportation Awards competition, has made it to the Top 12 finalists to compete for one of two national awards - the Grand Prize and the People’s Choice Award.

While the Grand Prize is decided by an independent panel of industry experts, the People’s Choice Award is decided by the general public through online voting. Last year, when the Loop 202 South Mountain Freeway made the Top 12, we asked a big, but simple favor from you to go online and vote daily for that project. 

We’re asking the same favor from you this year! Go online and vote for the Fourth Street Bridge project each day from now until Oct. 25! Every vote counts!

Need some reasons why you should cast your vote for the Fourth Street Bridge project? Happy to oblige:

• The Fourth Street Bridge has improved community connectivity in Flagstaff by adding more lanes for vehicles to use and a protected path for pedestrians and cyclists!
• The new bridge helps make it easier for students at nearby Northland Preparatory Academy to get to-and-from school.
• The bridge also connected the Flagstaff Urban Trail System across Interstate 40, allowing trail hikers to continue along uninterrupted.
• The bridge was replaced using the “bridge slide” method, in which crews slide the new bridge into place of the old one using hydraulic jacks. This method cut an estimated two months off of construction time and saved nearly $7 million.

Anyone, anywhere can vote. If you’re a Flagstaff resident who has benefited from the new Fourth Street Bridge, now is the time to show your support through voting! Follow this direct link to vote not just once, but every day, for the Fourth Street Bridge through Oct. 25.

As an added bonus, the winning project gets a $10,000 cash prize donated to the charity of the state DOT’s choice. So voting not only gives this well-deserving project national kudos, but it will help benefit a local charity as well!

So do us a solid and set a reminder on your smartphone to vote daily for the Fourth Street Bridge project and give Arizona a chance to shine in the transportation world! 

Looking at State Route 264 on a map, it appears as a jagged east-west line in the northeast corner of Arizona.

But appearances can be deceiving. SR 264 is a vital connecting corridor for the Hopi Tribe and other area motorists, much like State Route 51, Loop 101 and Interstate 17 are for Phoenix area commuters.

Winding from US 160 near Tuba City, the state highway links together all 12 Hopi villages and continues on past Steamboat and Ganado and other destinations. The 154-mile Arizona portion ends at the New Mexico state line near Window Rock, where it continues east as NM 264.

This is why the Arizona Department of Transportation rehabilitation of the Dinnebito Wash Bridge on SR 264 near Hotevilla-Bacavi, milepost 363, is so important.  

The deck replacement project, which is nearing completion, is located west of Third Mesa, one of three mesas on the Hopi Reservation that are comprised of the 12 Hopi villages.

Despite it's importance to SR 264 travelers, by bridge standards, this bridge is short at only 212 feet long, said Mokarr

om Hye, Senior Bridge Engineer with the ADOT Bridge Group.

“The main work is replacing the bridge deck,” Hye said. “We demolished it completely. We are increasing the deck thickness.”  

Originally constructed in 1955, the steel girder bridge allows travelers to cross the Dinnebito Wash about three miles west of Hotevilla-Bacavi Village and 40 miles east of Tuba City.

“It is in a remote area, which makes it challenging,” Hye said. “It is really in the middle of nowhere.”

There’s no quick and easy way to get to milepost 363 on SR 264 from central Phoenix. It’s a 276-mile journey starting with Interstate 17 northbound to Flagstaff, Interstate 40 eastbound to Winslow, State Route 87 northbound to the town of Second Mesa and then heading west on SR 264, past Hotevilla-Bacavi to the destination.

Crews are in the second phase of the project. They’ve poured concrete on one half the bridge and are working on the other half.

Since the rehabilitation started in May, SR 264 has been reduced to one lane of alternating travel on the bridge from 6 a.m. to 6 p.m. daily, including weekends.

“In terms of schedule, we are on schedule,” Hye said. “The roadway is scheduled to reopen this fall.”