Remember this awesome time-lapse video showing the construction of a temporary bypass at Greenway Road and the Loop 303?

Well, today we’ve got an even more in-depth look at how crews built the new intersection – complete with temporary barriers, fences and traffic signals – in just about 43 hours! (Take a look at the photos below for an amazing before and after aerial glimpse of the new bypass!)

Having this new intersection/bypass in place is pretty critical for the rest of the work being completed on the Loop 303 (the project is in its second phase and stretches from Mountain View Boulevard to Peoria Avenue).

The temporary intersection not only helps motorists avoid the work zone, but the incorporation of an equipment pass-through will assist crews as they haul an estimated 75,000 loads of dirt away from the site to build the Greenway Road overpass.

“We started back in August working on this knowing that getting Greenway and the 303 relocated on the detour was going to set this project in motion,” Loop 303 Project Supervisor Mark Wheeler said.

Check out the video above and you’ll see that it took some real coordination to complete the work in such a short period of time (bonus points if you also see the lunar eclipse at about the 1:42 mark).

This photo is from December and shows the new bypass.

Accommodating existing traffic is a key priority when ADOT builds a freeway …

Depending on the project, that can mean working out a construction schedule that takes rush hours into account or hiring extra crews to flag and direct traffic through the site.

But, on the Loop 303 project in the West Valley drivers will notice a new construction bypass that (amazingly) was built in around 43 hours this past weekend. The bypass will be in place for the next 10 months and not only will it allow for a more efficient way to haul dirt, but it’s also going to help drivers avoid the construction zone!

Building the bypass

Crews shut down the intersection at Greenway Road and the Loop 303 at 10 p.m. Friday, Dec. 9.

Roughly 8,000 cubic yards of dirt was hauled in from other parts of the project site to build up the road. That dirt was placed Friday night in eight-inch layers and was compacted until it was the right height for the bypass (see video above!). After that, the road was paved and striped on Saturday.

Prior to the weekend work, crews had built everything they could up until the point where the bypass would cross “live” traffic and require the closure. That required even more dirt – about 40,000 cubic yards.

Crews not only had to build the bypass, but also installed temporary concrete barriers, fencing, sidewalk and a traffic signal.

The traffic signal went in Saturday morning after the power was shut off to the “old” signal. The signal pole’s electric meter and pedestal were set to the new location and power was turned on. ADOT wired the signal Sunday morning and installed a common video detection device that will help with signal timing.

After some finishing touches, the bypass was ready and opened to traffic by about 5:15 Sunday evening – 12 hours ahead of schedule!

Before you can build a freeway, you’ve got to move a little dirt...

Make that a LOT of dirt, especially in the case of the Loop 303 project under construction right now in the West Valley.

Crews are working to construct additional lanes and plan to move about 3 million cubic yards of dirt by the time the project is finished. (By the way, a lot of work is planned for the Loop 303. The portion of the project we’re talking about runs from Mountain View Boulevard, south to Peoria Avenue.)

That much dirt translates to roughly 200,000 truck loads – and these are some big trucks (take a look at them in action in the video above).

Other projects may, or may not require this much earthwork. It depends on the road design and the original shape of the terrain.

Take the Loop 303 project for example...

Part of the freeway (starting slightly south of Greenway Road headed north) is going to be depressed ... in other words, freeway traffic will pass underneath the nearby local streets. The rest of the freeway (heading south of Greenway down to Cactus Road) is going to be elevated and will pass over local traffic.

So, parts of this project need to be dug out and other portions need to be lifted up. The dirt that crews dig out in some areas helps to build the overpasses in other spots.

If you’re lucky, it all balances out. Otherwise, purchasing additional dirt is an option. Or, if there is a surplus, the extra dirt often can be utilized in landscaping and to build berms.

Moving the dirt...

Before any digging can start, the dirt is pre-wet to make it easier to move and help with compaction and dust control.

After that, there’s some heavy-duty equipment that comes into play.

Typically, an excavator is used to dig up the dirt. The excavators being used on the 303 project have buckets that hold about seven cubic yards worth of material at a time. Those load onto something called a belly dump truck (see photo below).

Scrapers also are used to dig up the dirt. Depending on their size, scrapers can hold and transport about 14-18 cubic yards at a time.

Contractors have geotechnical reports that tell them the type of soil they’re going to be dealing with. Crews sometimes will run into rocky terrain on projects, which requires blasting.

Whether they need to blast or just dig, crews have to put the dirt somewhere...

If it’s being used on the project (as is the case with the Loop 303), the dirt is hauled to where it is needed.

It is dumped in 8-inch lifts (or layers) and is knocked down with a compactor and roller until it reaches the necessary compaction rate – again, this is where pre-wetting the dirt comes in handy.

Last month, as part of our Building a Freeway series, we told you about the massive underground support substructures that help give bridges strength.

Next up in the series is an important -- but temporary -- structure that’s used as crews build a bridge, tunnel or even a box culvert.

It’s called false work, and it is used to support the structure until the concrete gets its desired strength and the bridge can carry its own weight.

Imagine that you’re building a bridge out of popsicle sticks. Those sticks can’t support their own weight at first, so you might use some blocks to give it some support until your glue dries.

Those blocks are the basic equivalent to false work…

But now what happens when your bridge is complete and it’s time to take the false work out so you have a fully functioning bridge?

With the popsicle-stick scenario, pulling the blocks out might be pretty easy once your glue is dry. But with a large bridge or tunnel, it’s not so simple.

Because the false work is so tightly jammed up against the structure that it has been supporting, taking it down safely requires something called a sand-jack.

A sand-jack is a simple concept, but really is genius when you think about it …

Basically, it is a metal, square “box” (see photo below). It gets lined with plastic (to keep moisture out) and filled with sand. A ¾-inch piece of plywood goes on top of that sand and the false work is built on top.

Because the sand is contained, none of the weight is going to settle -- there’s nowhere for the sand to go.

Now, when it’s time to take the false work down, all crews have to do is unbolt the sand jack “box” and blow the sand out of it. That gives crews a few inches of “wiggle room” to pull out the false work.

To do that safely, they’ll first secure the false work with a forklift. Next they’ll carefully remove the false work structure, except for the “lid” (not a technical term, but the best word to describe this part of the false work).

The “lid” is the top, flat part of the false work over which the deck of the bridge or culvert is built. Just pulling out its support would be dangerous … so crews hold the lid up with the use of hydraulic jacks. The jacks will set on top of the concrete structure with long rods that run through the jack, through the concrete deck, and finally connecting to the false work lid. After the false work legs have been removed, the crews will slowly lower the false work lid to the ground (imagine a mechanic jacking up a car, but in reverse).

When the false work (including the lid) is all out, the bridge, tunnel or box culvert is ready to go! Check out the video above for a look at false work and sand jacks in action. The structure being built is a box culvert that will be used as an equipment pass through during construction of the Loop 303. We'll explain more about that one soon. Stay tuned...

You know when you drive under or over a freeway bridge that it’s a massive structure…

There are the two abutments (the upright supporting structures at each end that carries the load of the bridge span), there are usually center columns or piers, and, of course, the girders and the bridge deck (the part you actually drive across).

The girders and the deck make up the bridge’s superstructure. (You can tell how much goes into a bridge’s superstructure by checking out what goes into taking one down.)

But what you don’t see is that buried beneath the bridge is part of the equally impressive substructure formed by rows of caissons – massive steel-and-concrete pillars that support and lock in place the abutments.

The substructure, which is made up of the caissons and the abutments, ensures that the bridge is secure and strong enough to support not only its own weight, but also the weight of all the vehicles that drive across it every day.

The caissons are formed by tying thousands of feet of rebar into massive steel cages that are then lifted with a crane, lowered into drilled shafts, and filled with concrete. Several feet of rebar is left rising out of the ground, which is what the abutments are ultimately secured to.

There’s no such thing as a “standard size” caisson…their lengths and diameters vary from project to project and bridge to bridge based on several factors, including the soil type and the expected and actual weights the bridge must support.

Generally speaking, caissons for most bridges in Arizona are between 40 and 120 feet deep and 5 to 12 feet in diameter.

There’s also no set number for how many caissons each abutment will require – that, too varies by bridge.

Take the three bridges being constructed for the new phase of Loop 303 in Surprise, for example. The bridge abutments at Waddell and Cactus roads are supported by 23 caissons each (46 total per bridge), while the bridge at Greenway Road, which is only partially elevated over Loop 303, requires just 20 total caissons (10 under each abutment).

The video above shows the fabrication and installation of those Loop 303 caissons. The steel cages for these particular caissons are 95-feet long and weigh about 20,000 pounds. The cages were lowered into 88-feet-deep drilled shafts and filled with 80 cubic yards (8 truckloads) of concrete each.

If you’re keeping tally…that’s 8 truckloads for each caisson, times 106 caissons, for a total of 848 cement truckloads (for just those three bridges)…and that is just part of the substructure!

The concrete for these caissons cures in about 24 hours, clearing the way for the next phase of building a freeway.

When ADOT has a freeway to build, many steps must be taken long before any asphalt is paved.

One of those initial tasks involves pre-wetting the soil, which entails pretty much exactly what you think it does … crews put sprinkler systems into place and water the dirt!

Just how long crews need to water depends on the type of soil they’re dealing with, but usually this step takes a few days.

Pre-wetting the dirt makes it easier to move, helps the crews eliminate dust pollution and allows them to bring the soil’s moisture content up to a level that enhances compaction.

If you’ve ever built a sand castle, you know it’s much easier to work with sand that’s a little wet (but not too wet). Not only is it easier to build with compared to dry, loose grains of sand, but it also gives your castle a stronger foundation to build upon.

The same principal holds true out in the middle of a road construction site …

Once the soil’s moisture content is at the optimum level, the dirt can be excavated and moved to embankments or medians or off the site completely (depending on the project).

Then it’s time for compaction. This is done with different types of heavy-duty equipment like rollers, dozers, scrapers and front-end loaders. Compacting the soil creates a good solid base for the road (think of your castle’s foundation) and pre-wetting the dirt makes this step easier.

“Water serves a big purpose in compaction,” says Loop 303 Project Supervisor Mark Wheeler in the video above. “It gives you the foundation which you build on and that equates to longevity on your roadway.”

When ADOT builds a road, the work gets started years (sometimes decades) ahead of any real construction …

It all begins with the planning phase, which includes everything from determining where a new roadway is most needed to taking a look at available funding.

From there, environmental studies are completed, public involvement is conducted and preliminary plans get designed. ADOT continues to engage the public as engineers begin developing more detailed project plans. Through each phase of the project, ADOT coordinates with other government agencies, developer/landowners and utility companies.

By the time the project is ready for construction, a considerable amount of time has been invested, but there’s still a lot of work left to be done!

(By the way, this is by no means an exhaustive list of what it takes to build a road, but hopefully you can see that it’s a big job.)

More work on Loop 303. Crews are building an underpass for construction vehicles to use during the build.

We want to give you a more detailed look at each step, so today we’re kicking off a long-term series of blog posts and videos designed to show how ADOT builds a road from start to finish.

We want to use this space to help inform people about what we do and why and how we do it.

We hope you stay tuned and look out for posts tagged with “Building a Freeway.” It all starts tomorrow with a video and blog post on pre-wetting— one of the very first steps in the construction phase.