A new regional drainage system is ready to handle stormwater flooding at underpasses between Peoria Avenue and Greenway Road in Phoenix, state transportation officials said Monday.

The $38 million drainage system was managed by the Arizona Department of Transportation 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 stormwater retention basins near Thunderbird Road.

“The new system also allowed ADOT to remove outdated pump stations, installed in 1964, near lower-lying underpasses carrying Peoria Avenue and Cactus, Thunderbird and Greenway roads beneath I-17,” state officials said.

The underpasses have been subject to flooding during heavy rain, they said.

Work on the new system started in spring 2020.

Construction involved 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, according to ADOT.

“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,” officials said.

“Drivers should proceed with caution when storms hit and avoid driving into areas with standing or moving water.”

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