Pumping stations failed at some freeway stations

Sean Holstege, Caitlin McGlade, and Edward Gately
The Republic | azcentral.com
Jim Sampson retrieves items from his 2002 Toyota Corolla stuck in floodwaters on Interstate 10 at 43rd Avenue after Monday’s monsoon rains inundated the freeway. Pump stations along Valley freeways, including this stretch of I-10, failed, causing floods that stranded dozens of motorists.

In a Valley unaccustomed to the rain, the historic late-summer deluge of 2014 tested pieces of the public-works infrastructure — and pushed some of them beyond their limits, as pumps failed, freeways and city streets disappeared beneath rising water and some motorists headed into the mouth of the flooding unaware.

Those stretches of freeway flooded because pumping stations designed to keep them dry failed at key locations, including along Interstate 10 in west Phoenix, according to early indications from the Arizona Department of Transportation. That left dozens of morning motorists stranded in deep water.

"If there was flooding, we likely faced some kind of challenge at the pump station," ADOT spokesman Doug Nintzel said. Some older pumps failed to kick in, while others automatically switched off, he said. Both had to be started by hand.

Other parts of the Valley saw stories of success and failure Monday as man-made systems managed heavy rain and runoff.

In Mesa, neighborhoods on the north edge of U.S. 60 flooded late in the day as retention basins overflowed. The basins normally hold runoff in conjunction with nearby Arizona Department of Transportation canals along U.S. 60. But both the basins and the canals filled Monday, leaving extra water with nowhere to go. It backed up into a neighborhood off Harris Drive and Harmony Avenue. Mesa officials said it could take two weeks to a month to drain the water, and urged residents to evacuate.

The rain deluge had such a strong impact on Phoenix, city officials may be rethinking their standards for flood planning.

But Scottsdale officials had reason to cheer: the11-mile Indian Bend Wash flood control project did its job.

The Valley's freeway loop system, the newest freeways, also fared well during Monday's soaker. There was water on the roads, but none of the widespread flooding experienced on older highways.

Most of the freeway network's 71 pumping stations are designed with three to five individual engines, which are triggered by in-ground sensors. Those sensors act like a float in a toilet tank: When the water rises to a certain level, the pumps kick in.

Except on Monday at 1-10 near 43rd Avenue, site of the most dramatic flooding.

"The pumps were not turning on automatically," Nintzel said, and it wasn't until 7 a.m., four hours into the downpour, that "troubleshooters manually turned on the engines."

Elsewhere, pumps did kick on but couldn't keep up with the volumes of rain and run-off water. Some engines in some pump houses automatically switched off to avoid burning out, Nintzel said.

On State Route 51 near Cactus Boulevard, two of the five engines cut out. The station couldn't keep up with the deluge at 60 percent capacity, and the highway was under water by the time crews manually restored full pumping. Farther south near Highland Avenue, one of the five pumps shut off. It was the same story at the Kyrene pumping station, where two of the three engines shut off.

"This gets into the challenges you have with an aging infrastructure," Nintzel said, adding that ADOT crews maintain the stations year round, and step up inspections right before the monsoon.

Generally speaking, he said, the older the freeway, the older the pumps, and the more maintenance they need. On Interstate 17, one of the oldest stretches of interstate in the country, a pump station is 50 years old, and the engines have to be removed and repaired by specialists in such models.

But there may have also been more underlying issues.

ADOT's "Highway Drainage Design Manual," published in 2007, says freeway design should handle the amount of water generated by a 100-year flood. A 100-year flood means one that has a 1 percent chance of occurring in any given year, on average. But it states that pumps at "depressed freeways," such as the underpasses that were inundated Monday, should only accommodate a 50-year storm, one that is twice as likely. ADOT designed the pumps to the looser 50-year standard in such locations, Nintzel said.

Parts of the Valley saw record rainfall, but until final storm totals are in, it remains unclear if the storm topped the 50-year mark.

Valley cities, some with higher standards, appeared to fare better, even though street flooding was widespread.

If Monday was a test, Scottsdale's Indian Bend Wash didn't break. The 11-mile wash, completed in 1984 as a flood control project, "worked exactly as it was designed to work," said city spokesman Mike Phillips.

The greenbelt stretches north from Paradise Valley down south to the Salt River in Tempe. The wash carried as much as 6,000 cubic feet per second, about one-fifth of what it was designed to handle, city officials said. Once the rain stopped, the wash played a major role is draining city streets and neighborhoods within the Indian Bend Wash watershed, said Ashley Couch, the city's storm water manager and floodplain administer.

In Phoenix, the standard to withstand 100-year floods may not be good enough to clear low-lying roads in Laveen and in northern Phoenix and along the Salt River, said Ray Dovalina, street transportation director.

He said Phoenix will work with the Flood Control District of Maricopa County and other agencies to assess whether plans for future infrastructure improvements need to be updated to address higher demand.

Councilwoman Kate Gallego says the city's needs exceeds available funding. "We'll have to have conversations about how much risk we're willing to take,'' she said. "We need to look hard at what we can do and assume what used to be an extreme event is not an extreme event anymore."

Phoenix installed a $20 million conveyance channel in Laveen in the 2000s to help catch the rain that dumps into the area from South Mountain and funnel it to the Salt River. But the area remains on high priority for future flood-control infrastructure improvements.

Connie Cone Sexton, Maria Polletta and Megan Finnerty contributed to this report.