Upgrades to begin soon to keep Interstate 17 underpasses from flooding

Heavy rains can cause highway flooding, snarling traffic. Four underpasses along Interstate 17 in north Phoenix will be improved to help alleviate flooding during downpours. (Photo by Jordan Evans/Cronkite News)

PHOENIX — During last week’s monsoon storm, several underpasses along Interstate 17 in north Phoenix flooded, causing traffic delays. This isn’t uncommon. In September 2014, for instance, flooded underpasses shut down sections of Interstates 17 and 10 and U.S. 60 for several hours — and, in some cases, several days — while outdated pumping stations worked to remove the water.

Flood control upgrades to four underpasses along I-17 – Peoria Avenue, Cactus Road, Thunderbird Road and Greenway Road – will help alleviate this. The Maricopa Association of Governments and Arizona Department of Transportation will begin work on these upgrades in the next few weeks. The project is expected to take up to two years to complete.

According to MAG’s Transportation and Finance program manager, John Bullen, the core of the work will involve replacing old pumping stations, which use large engines to remove floodwater.

“The pump stations aren’t as efficient as they once were,” he said. “They’re old, which means they don’t quite work well.”

Instead of pumps, the four underpasses will be fitted with a gravity drainage system that will channel water to the Arizona Canal and a new drainage basin.

“This gravity-fed system is anticipated to work significantly better and certainly reduce the potential for flooding,” Bullen said.

This project is one of many planned for Valley freeways under MAG’s 2040 Regional Transportation Master Plan.

I-17: A key corridor and a roadblock

In the regional transportation plan, Interstate 17 is slated for significant upgrades between now and 2040. MAG expects to spend close to $1.5 billion on upgrades to the I-17 and I-10 “Spine Corridor” over the next two decades.

Most of those upgrades won’t involve the freeway mainline itself but will focus instead on the arterial roads crossing it. The interchanges are “pinch points” in the east-west transport system, according to multiple MAG studies.

“More traffic actually crosses I-17 than uses it,” Bullen said. “This project in particular will address a lot of those connectivity issues around the freeway and enable that east-west traffic.”

The interchanges at Happy Valley and Pinnacle Peak Road are under construction now. Upgrades to Indian School Road interchange are currently in the planning phase, Bullen said.

The I-10/I-17 Master Plan calls for nearly every arterial road crossing I-17 to have interchanges upgraded by 2040.

Funding for these projects comes from Proposition 400, which Maricopa County voters approved in 2004.
The proposition authorized the county to continue collecting a half-cent sales tax — originally authorized by voters in 1984 — through 2025. Revenues collected from the sales tax go into funds for highways, arterial roads and public transit.