MAG News

When the monsoon arrives in Arizona every year, it brings wind, dust, and rain—sometimes a lot of rain. For years, right in the heart of the Interstate 17 corridor through Phoenix, heavy monsoon rains would occasionally overwhelm the drainage system. When that happened, it led to dangerous flooding in the underpass areas from Peoria Avenue to Greenway Road.

Rainy Day Problems

The original system of four pump stations, built in 1964, was designed to move excess water from the area after storms and needed a significant upgrade.

Thanks to funding from Proposition 400, the dedicated half-cent sales tax for transportation approved by Maricopa County voters in 2004, a new $49.5 million drainage system was built. The gravity-controlled system allowed the Arizona Department of Transportation (ADOT) to remove the four outdated pump stations.

Those stations were near the low-lying underpasses on I-17 at Peoria Avenue, Cactus, Thunderbird, and Greenway roads beneath I-17, along the same four-mile stretch the new system follows. 

The updated system installed new pipelines for the gravity controlled system, and built sizeable stormwater retention basins. "Our engineers designed this system to better handle significant storm events," said ADOT Senior Resident Engineer Jimmy Naujokaitis. "In addition to the removal of the outdated pump stations at cross-street underpasses between Peoria Avenue and Greenway Road, the project installed pipelines to use gravity to move stormwater without pumps."

Tunneling Under I-17

Getting the job done was not easy. Construction involved approximately four miles of extensive trench work and tunneling nearly 30 feet under I-17 for pipeline installation. Doing so allowed ADOT to keep I-17 open during the construction process. 

The new drainage system has been a success. Angled pipelines now move stormwater into two retention basins at Thunderbird Road and Greenway Avenue, and into the Arizona Canal Diversion Channel north of Dunlap Avenue.

Just In Time for the Monsoon

While it was completed in time for the monsoon, the project had been in the works for a while. Planning and design concept work wrapped up in 2014, but the final design continued through 2019. The first shovels went into the ground in 2020. After three years of hard work, the infrastructure project was completed in June 2023. Since then, the once frequently flooded areas of I-17 have been free of floodwaters, ensuring a safer commute for all drivers.

"Now that we don't have to rely on mechanical means to remove runoff in the underpasses, the dependability of the drainage infrastructure along this section of I-17 north of Dunlap Avenue has significantly increased," added Naujokaitis. "We haven't experienced any significant buildups of standing water since the new system went into operation last summer."

The upgrades are designed to reduce the potential for flooding, but a large amount of rain in a short period still can make things difficult for any drainage system. Drivers should proceed with caution when storms hit and avoid driving into areas with standing or moving water.