As the Salt Lake Valley saw its rainiest October in over a century, the Midvale City Council approved a Storm Water Master Plan to address deficiencies in handling storm water runoff in the city’s infrastructure.

The master plan – prepared by consulting firm Hansen, Allen and Luce (HAL) – recommends 12 capital projects for Midvale, which would cost the city about $20.7 million. 

Kayson Shurtz, project manager and engineer at HAL, told the council on Oct. 7 that the “heart of the master plan” is three of those 12 project proposals: 7800 South, stretching from the East Jordan Canal to I-15; Lennox Street, from Main to Holden Street; and Wasatch Street, from State Street to Main. One of the key issues with the drainage systems is that they are combined with irrigation pipes. 

“The irrigation issue is one that I'm seeing in a lot of cities, when, at the time, it seemed like a good idea,” Shurtz said. “We have pipes. We maybe don't need all of the pipe for irrigation. But as urbanization increases, that irrigation decreases. It becomes a very difficult marriage in some ways for the irrigation and the city stormwater to work together.”

Decoupling the city’s stormwater system from irrigation channels will put Midvale’s “pipeline in the city right of way so city crews can adequately maintain the system,” Shurtz said.

“If we can disconnect from [the irrigation pipes], we have our own system, we control our own destiny,” he added.

The total cost of the three projects adds up to $14.7 million.

“These are projects that could occur over time,” Shurtz said. “The good news is that overall, your system works very well…so some of these [projects] could be viewed as longer-term things, depending on how things work with the budgets.”

Along with the 12 capital projects, the master plan requests purchasing a camera inspection truck and putting aside $200,000 annually from the city budget to replace pipes at high risk of collapse.

“To be able to identify the worst areas, you need a camera and a strap inspection truck,” Shurtz said. “You need to be able to see the condition of the pipe and assess it, to be able to know where to put those dollars to work.”

To determine how much runoff Midvale’s stormwater system must handle to prevent flooding, Shurtz said the plan uses a study from the National Oceanic and Atmospheric Administration as a blueprint for predicting the volume of water from 10-year and 100-year storm events.

“What a 10-year event actually means is not that it's going to happen once every 10 years; it means that there's a 10% chance that a storm like that could happen on any given year,” Shurtz said, with 100-year events referring to storms with a 1% chance of occurring in any year.

The Salt Lake Valley had its wettest October in 151 years, with rainfall reaching nearly 5 inches, according to the Utah Division of Water Resources. 

With the valley seeing unprecedented storms, Mayor Dustin Gettel asked how the city can prepare for two 10-year events two weekends in a row. Shurtz responded that keeping up with maintenance on stormwater pipes is crucial in handling back-to-back events. He added that having developers show that their system designs can withstand a 100-year event is another key piece of the puzzle.

“Sometimes we just close our eyes and say, ‘I hope the street can take it,’” Shurtz said. “But actually having calculations behind that to show, if we have a super big event, I'm not flooding homes, I might have 6 inches or a foot of water in the street. That's OK if it's not flooding a house.”

The council approved the Storm Water Master Plan on a 4-0 vote on Oct. 21, with Councilmember Heidi Robinson absent.

  A map of Midvale’s stormwater basins. (Midvale City)