There's an idea out there called creative destruction. It basically says that tearing down the old is sometimes necessary to make way for the new. This has been applied to everything from economics to the arts, but we found it very fitting recently for our project on Interstate 17 over Central Avenue.

As you can see in these photos, crews spent a busy weekend recently tearing down the old southbound bridge. Now that the old bridge (built in 1962, by the way) is gone, we can go ahead and start building its replacement. Traffic was switched to using only the northbound bridge back in June. When the southbound bridge is finished early next year, traffic will be switched again to use that and the whole process of creative destruction will begin on the northbound side.

Drivers should continue to expect delays in the area while I-17 is narrowed to two lanes in each direction. They should also consider using Interstate 10 if they are going beyond the downtown area. 

But we aren't tearing down just to erect something similar in its place. The new bridge will raise the clearance on Central Avenue from 14 to 16 feet, which will also allow for the future extension of the Valley Metro light rail south of the downtown area. Plus, the structure will be wide enough to accommodate future work to add auxiliary, or merge, lanes along the right shoulder of I-17 in both directions between the on- and off-ramps at Seventh Street and Seventh Avenue.

Once the creative destruction is all over, we think you’ll like what we will have created.

The whole $13.5 million project is scheduled to wrap up in fall 2021. You can learn more on our website. 

The year was 1928. Antelope Bridge, built in 1915 over the Gila River near Yuma, was sustaining damage with nearly every flood. Repair bills were mounting. The state decided to abandon the bridge completely. 

Arizona State Engineer Lamar Cobb decided to build a long suspension bridge over a ford in the river at Dome, about 15 miles east of Yuma. It would be named McPhaul Bridge, in honor of Henry Harrison McPhaul, a Yuman who served with the Arizona Rangers. 

In January 1928, the Arizona Highway Department contracted with the Levy Construction Co. of Denver to build the structure for $152,454 (that's around $2.28 million in 2019 dollars). Although highway department engineers had outlined the bridge's location and span, Levy engineered the bridge with the assistance of nationally known consulting engineer Ralph Modjeski, a pioneer in the design of suspension bridges.

Construction began in mid-1928 and was completed in December 1929. McPhaul Bridge carried traffic on US 95 until 1968, when it was deemed unacceptable for modern, heavier cars. A new dam was built upstream that rerouted the river, along with a new bridge to carry the highway, leaving the old bridge metaphorically and a bit literally high and dry.

The bridge is in reasonably good condition today; one can even see the wooden spans under it. However, due to safety concerns because of its age, you can no longer walk or drive across the bridge. Because it sits in the middle of the desert (check out the map below to see its location and proximity to US 95 and Yuma), some on the internet have taken to calling it Yuma's bridge to nowhere.

McPhaul Bridge is a historic piece of Arizona. Suspension bridges are rarely found in this part of the country. And to find one from the pre-Depression era in as good of a condition as McPhaul is even more rare. The bridge was also an integral link on a regionally important north-south highway in western Arizona.

Given that the majority of us are transportation geeks, it's no wonder that we are a little mesmorized by this photo, showing the back-and-forth riveting and lacing along one of the beams of the bridge that straddles the Verde River at Perkinsville. It's a perfect example of how even the most utilitarian engineering details can have a beauty all of their own.

Now Perkinsville is a weird place for us to be spotlighting, as the ghost town sits in the heart of Yavapai County, northwest of Jerome, far from any state highways. The town sprang into existence as a railway depot for a shortine in 1912. A nearby limestone quarry and kiln helped it produce lime for a smelter at Clarksdale and a copper mine in Jerome. This bridge went up across the river in 1936. However, the closure of the smelter a few decades later led to its rapid decline. Though today it does now serve as a turn-around point for the scenic Verde Canyon Railroad.

That's all well and good, but where does ADOT come in? Well, we did some digging into the bridge's history and found that Perkinsville was not it's first home. For that we have to jump more than 20 years further into the past and some 160 miles to the southeast. According to a historic bridge inventory, Arizona congressman Carl Hayden was able to pass legislation in 1912 for a multi-span steel-and-concrete wagon bridge to be built across the Gila River near Calva on the San Carlos Reservation. The seven-span, nearly 1,000-foot-long bridge was built by Midland Bridge Company out of Kansas City, under the supervision of the Office of Indian Affairs in Washington, D.C. This became an important regional river crossing and was the first of the increasingly common riveted Pratt through truss bridges in the state. 

The bridge's abutements would be damaged by flooding and four of the seven spans would be replaced in 1921. Finally, in 1936, it was decided to replace the bridge completely. 

And that's where we get invovled. Well, not us exactly, but our predecessor, the Arizona Highway Department. During the Great Depression, the state and the U.S. Forest Service entered into an agreement to find labor projects for unemployed transients living in camps across Arizona. So, with the bridge over the Gila set to be replaced, Arizona Highways Department Bridge Engineer Ralph Hoffman had the idea to use this labor force to dismantle three of its spans and then erect them in the Prescott National Forest. Two of the spans became the Perkinsville Bridge, while the remaining span became a nearby bridge over Walnut Creek. Though other public works were completed under this partnership, the crossings at Perkinsville and Walnut Creek are the only know bridges to have been erected by this program.

The two bridges have remained unaltered to this day at their relatively remote crossings. You can see a full photo of the Perkinsville bridge from 2002 below.

Over the span of a couple nights, concrete trucks and pumps worked from along the banks of the Gila River in Winkelman to transform a long grid of rebar into something drivers can really appreciate: the concrete surface of a new bridge.

It may be only half a bridge at the moment, but that’s a big milestone for the State Route 77 bridge replacement project in this community east of the Valley. The ADOT project that began in September 2019 is nearing the halfway point, and the progress is clear in this recent photo from the project site.

The deck pour took place at night to avoid scorching daytime temperatures. Best of all, the crew positioned concrete trucks along the river banks so the remaining half of the bridge could remain open to traffic throughout the work.

The project was designed to replace half the two-lane bridge at a time, which means one lane of alternating traffic can use the structure. A signal regulates traffic flow, and drivers should expect some delays.

Once the new half of the bridge is complete, we’ll move traffic to the new concrete surface. That’s expected in about a month, and it will involve some additional delays for a day as crews shift the single lane of traffic.

Then work will begin to demolish the remainder of the old bridge and construct the remaining structure. The project is scheduled for completion by summer 2021. For more information, please visit the project page. 

If you're a driver whose travel takes you along Interstate 17 near Central Avenue south of downtown Phoenix, you've likely noticed some changes now that bridge resconstruction work has started in that area.

As we told you about a few weeks ago, we have kicked off our project to replace the aging Central Avenue bridge. The new structure will raise the clearance from 14 to 16 feet, which better allows for modern commercial vehicles, trailer-towed construction equipment and the coming Central Avenue light rail extension. That's a slideshow of the beginning of the $13.5 million replacement project you can see to the right. You can also check out the project's page on our website to learn more.

But after this weekend, you'll notice more changes.

Starting tonight,  the southbound freeway will be closed at Seventh Avenue while northbound will be closed between the Interstate 10 "Split" and Seventh Avenue. When it reopens early Monday morning, traffic will have been switched to using just the northbound bridge, so the southbound bridge can be reconsructed. Once that wraps up early next year, traffic will be switched to the southbound structure so the northbound bridge can be similarly improved. While the project continues, outside of other needed closures or restrictions, we will keep two I-17 lanes open in both directions.

But while we are keeping lanes open, drivers should continue to budget extra time if their commutes take them through the work zone. You can also consider using alternate routes, such as I-10 through downtown Phoenix.

The whole project is scheduled to be wrapped up in fall 2021, and we are confident you will notice and appreciate this improvement.

Did you know that Arizona highways have more than 4,824 bridges? 

Crazy right? That's 4,824 times a highway has to cross rivers, washes, rail road tracks, canals, another highway, etc.

That's why we think it's a such great thing that recent survey of bridges across the nation showed that the state has some of the best bridges in the country. Only 1.6 percent of Arizona bridges are listed as being in poor condition, which puts us just a step behind Nevada and Texas.

Now a couple things to keep in mind. First, a bridge in "poor" condition doesn't mean it's a hazard to drivers who have to cross a river, canal or wash. It does mean that repair needs have been identified and provides ADOT's bridge engineers with a measurement to plan for improvement projects. Second, that 1.6 percent covers every single bridge in the state, even those that might be overseen by a county or municipality. If you just limit it to ADOT's 4,824 bridges, the number of bridges in the poor category actually goes down to 0.9 percent. Not too shabby!

The even better news is there are several projects that are already underway or planned in the near future to take care of some of those identified repairs. And projects are going all the time to build new structures or take steps to continue to limit the number of bridges in the poor category. We've told you several times about the bridge replacements happening along Interstate 17 over Pinnacle Peak and Happy Valley Roads, there's a major project happening on Interstate 10 and Ruthrauff in Tucson, and we can't forget the new bridge being put up on US 60 over Pinto Creek east of Superior. And just recently we announced improvements to the bridge on Interstate 17 over Central Avenue.

So, if like us, you have bridges on the brain, take a moment to celebrate all the state's spectacular spans with this compilation video. Or you can check out the gallery of images below. Either way, remember that you have 4,824 reasons to be excited about bridges.

Work to build a new, larger Interstate 17 bridge over Central Avenue south of downtown Phoenix is now underway as ADOT and partner agencies look ahead to improvements beyond the freeway itself. But the progress also means drivers should consider using alternate routes, including Interstate 10, while the bridge reconstruction requires I-17 lane closures.

The current I-17 bridge, dating back to 1962, provides clearance of just under 14 feet for vehicles passing underneath it along Central Avenue. ADOT’s $13.5 million project will provide a new structure with clearance of approximately 16 feet, which certainly helps with the movement of today’s larger commercial vehicles as well as the variety of construction equipment that is often hauled on trailers.

Meanwhile, the timing of the I-17 bridge reconstruction has been coordinated with the city of Phoenix and Valley Metro, since the modernized bridge will allow the future Central Avenue light rail line to extend south of the downtown area.

If you’re a driver who uses the stretch of I-17 between the I-10 “Split” interchange near Phoenix Sky Harbor International Airport and the I-10 “Stack” south of McDowell Road, you should plan ahead for lane restrictions now that a work zone is established in the area between Seventh Street and Seventh Avenue.

I-17 is now narrowed to two lanes in both directions approaching Central Avenue. By early June, additional work will be done to temporarily switch I-17 traffic to one side of the freeway so that the first half of the new bridge can be built. The freeway will operate with two lanes in each direction outside of times when closures or other restrictions are needed for work, mostly during overnight hours or on some weekends. That’s why it might be a good idea to use I-10 as a way to travel beyond the I-17 bridge construction zone.

The entire project is scheduled for completion in fall 2021. Additional information is available at azdot.gov/I17CentralBridge.

When finished, the new I-17 bridge will have been widened enough to accommodate a future project to add auxiliary, or merge, lanes along the right shoulder of I-17 in both directions between the on- and off-ramps at Seventh Street and Seventh Avenue.

It’s another step forward in what regional planners see as major improvements to help manage the traffic needs along one of the original backbone freeways in the Valley of the Sun.

EDITOR'S NOTE: During this unprecedented time, ADOT is creating transportation activities for kids. Please visit azdot.gov/ADOTKids or use the hashtag #ADOTKids on ADOT's Twitter, Facebook and Instagram accounts to see what we have going on. 

By Garin Groff / ADOT Communications

We’re excited that so many kids wanted to learn more about bridges and also that so many of you shared your bridge drawings with us!

We’ve already explained some of the work that goes into designing, building and maintaining bridges, and then we asked you to share questions you have about bridges. And you had lots of great questions! The video at right has answers from David Benton, ADOT’s bridge design manager. And here are some others, also with Mr. Benton's help: 

What is the longest bridge in Arizona?

While the video highlights the Mile-Long Bridge on Loop 202 in Tempe (a mile is 5,280 feet), after this activity ended we realized there's an even longer one. An elevated section of Interstate 10 near the "Stack" interchange with Interstate 17, just west of downtown Phoenix, is 7,111 feet long, making it the longest bridge in Arizona. Those are two very long bridges!  

How do bridges withstand earthquakes?

You might be surprised by this, but bridges can be built to move and wiggle like a spring when an earthquake hits. This allows the bridge to move along with the earthquake so the bridge parts don’t get damaged. And if they do get damaged, those parts can be fixed and the bridge can still stand.

How do you fix the parts of a bridge that are underwater if they break?

Fixing bridge parts underwater is tricky. In most cases, the best way to fix a bridge part that is underwater is to pump the water away so the construction workers can get to it and make repairs.

Why are triangles strong?

Triangles are strong when you put them together with a lot of other triangles. The reason they can be so strong is because some of the three sides of that triangle can be pushed and pulled. When those sides work together as a team, they can take a lot of weight. Check out how to build a popsicle stick bridge on the internet and you can find out ways to build these triangles!

Thanks again for all these great questions. Now let’s look at everyone’s great artwork!