A new I-17 regional drainage system designed to reduce the risk of stormwater flooding in underpasses between Peoria Avenue and Greenway Road in Phoenix is ready to operate .

The Arizona Department of Transportation managed construction of the $38 million drainage system on behalf of the Maricopa Association of Governments, the Valley's metropolitan planning organization. Crews installed new pipelines for the gravity controlled system and built large stormwater retention basins near Thunderbird Road.

The new system also allowed ADOT to remove outdated pump stations, installed back in 1964, near lower-lying underpasses carrying Peoria Avenue and Cactus, Thunderbird and Greenway roads beneath I-17. Those underpasses have been subject to flooding during periods of heavy rain and the new drainage system is designed to limit such events.

Primary work on the new system started in spring 2020. Construction involved extensive trench work as well as tunneling under I-17 for some pipeline installation. Angled pipelines will now move stormwater into retention basins or the Arizona Canal Diversion Channel north of Dunlap Avenue.

Although the upgrades are designed to reduce the potential for flooding, a large amount of rain in a short period of time can tax any drainage system, be it on state highways or local roads. Drivers should proceed with caution when storms hit and avoid driving into areas with standing or moving water.

ADOT plans and constructs new freeways, additional lanes and other improvements in the Phoenix area as part of the Regional Transportation Plan for the Maricopa County region. Most projects are funded in part by Proposition 400, a dedicated sales tax approved by Maricopa County voters in 2004.