Critical work is underway underneath the I-10 Broadway Curve - and you may have driven right over it

Some very impressive work for the Interstate 10 Broadway Curve Improvement Project is underway – almost 30 feet beneath I-10 and State Route 143.

Crews are relocating a 1,600-foot-long concrete irrigation pipe that crosses I-10 near 48th Street and continues north to the Tempe Drain. They’re using a jack-and-bore operation to dig under I-10 horizontally for about 400 feet. The jack-and-bore method enables workers to tunnel under the freeway without disturbing the ground surface. That’s important in this case, as roughly 300,000 vehicles are being driven on I-10 directly above the work area every day.

Making space for the irrigation pipe under I-10 is no easy feat. Because of the proximity to the Salt River the soil is sandy and riddled with rocks, known as cobbles. The workers are hand-digging, removing about five tons of soil and cobbles a day.  As they remove the soil and cobbles, they install a steel casing in 10-foot increments. They place each 10-foot section on rails and use a jack to push it into place, advancing four-to-six feet a day. Once all the casing is in place and firmly welded together, crews will install the irrigation line inside of it. See photos of the boring pit below ground and from the street level here. 

So why not leave the irrigation pipe where it is? First, it is too shallow, so widening I-10 over the existing pipe could cause it to break and leak water under the freeway. Second, it’s in the way of where crews need to build several drilled-shaft foundations for the new-and-improved interchange at I-10 and SR 143. The drilled-shaft foundations will be up to 60 feet deep; drilling down that far without hitting the irrigation pipe isn’t possible. By shifting the pipe to its new location - a few hundred feet to the west - crews will avoid a conflict during construction.

The jack-and-bore operation in this location is expected to wrap up this month. The project team anticipates the irrigation pipe will be fully relocated by the end of February 2022. Meanwhile, critical utility-relocation work remains underway in other areas of the project. Completing it in advance makes for a more efficient construction phase and protects the buried utilities we rely on every day from damage.

So the next time you drive along the project area, remember that some of the most important work is underway ... but underground.