In the span of three hours, between three and six inches of rain fell across the city. The resulting floods gave city staff an opportunity to see where the city’s storm sewer system was doing its job — and where it was not.

During a workshop prior to Monday evening’s regular Fort Dodge City Council meeting, Chief Development Officer Chad Schaeffer gave the council an update on the May 30 rain event and its impact on the city’s storm sewer system.

“One thing to note is that three inches of rain in three hours is a 10-year storm event,” Schaeffer said. “So that means that a storm like that should happen once every 10 years, or at about a 10% chance of it happening.”

He added that six inches of rain in three hours is considered a “100-year” storm event, or a storm that has a 1% probability of happening in any given year. He said in stormwater management, they categorize rain events into two-, five-, 10-, 50-, 100- and 500-year events.

-Submitted photo
Flood water from Central Avenue and 13th Street reached all the way up to the building at 1302 Central Ave. during a rainstorm in July 2019. Building owner Katie Underberg said she and her husband have invested a lot of money into the building and continually see it flood when the city’s storm drains on Central Avenue can’t keep up with heavy rains.

“When you look at our system, the storm sewer systems are designed for a five- to 10-year type event,” he said. He noted that the storm water detention facilities — or reservoirs designed to temporarily hold the rainwater that the storm sewers cannot handle during an active storm — are designed to manage a 100-year storm event.

“A 1% chance, that’s just a probability, but we are seeing those events happen much more often,” Schaeffer said. “We’ve seen that back in 2018 and 2010, so much more than every 100 years.”

Local business owner Katie Underberg recalled when a storm in July 2019 flooded the street in front of her business. Underberg and her husband own 1302 Central Ave., which houses businesses including The Drill Barbershop, Guthrie and Associates Real Estate and Cornerstone Property Management.

The building is located on the northeast corner of the intersection of Central Avenue and 13th Street, and the street in front floods during significant rain events, to the point where water seeps into the building, Underberg said.

“We bought the building and remodeled it in 2015,” Underberg said. “It’s a building that we are proud of, we have an investment in it; we have a lot of money in the building.”

-Messenger file photo
Crews work on the storm sewer lines on South 29th Street just south of Fifth Avenue South during the summer construction season in June 2017. The work helped alleviate flooding in the intersections during heavy rain storms.

She said that they finished the remodel in late 2016 and the very next year it flooded. She said that when they bought the building, they knew that it had flooded prior, so when they remodeled, they had the floor raised by four inches.

“That doesn’t seem to be enough,” Underberg said. “The storm sewer does not keep up out front of our building.”

She said it’s “nerve-wracking” to see this flooding happen to her businesses and investments.

“We have talked to several insurance agents and they have told us that since it is a city problem with the storm sewer, that we are not covered,” she said.

Every time it floods, Underberg said, they have to spend a couple thousand dollars to have the water removed and damage repaired.

“And while that’s bad enough, we just feel like we’re just waiting on when we lose the whole thing,” she said.

During the May 30 flooding event, Underberg said, they noticed that the flood water on the south side of Central Avenue was draining faster and was told it was because there are larger drains on that side of the street. She said in front of Green State Credit Union, the water drains twice as fast as it does in front of her building.

This flooding was the worst they’ve experienced thus far, Underberg said.

“I’m here today to ask for help and for the city to take this seriously, because it’s a big problem,” she said. “We really did try to do something good for downtown by remodeling the business and putting a lot of money into it.”

A little over a decade ago, after some significant flooding from heavy rains in 2010, the city looked at its storm sewer system and commissioned a study that showed major updates were needed for the storm sewers to keep up with heavy rainfall and not cause flooding in the city’s streets.

Schaeffer showed photos from some areas that experienced devastating flooding in 2010, including a portion of First Avenue South in front of Kemna Auto. In the photo, a vehicle that had presumably been driving eastbound on First Avenue South was surrounded by a lake of water reaching up to nearly the top of the sedan’s wheel wells.

Other areas that ended up underwater during that storm event included Smitty’s Garden Center and the former Land O’ Lakes property on Eighth Avenue South.

As a result of the study, Schaeffer said, plans for upgrades to the storm sewers were set into motion, starting with the East Region Storm Sewer Project. Over the last 12 years, there has been about $20 million worth of work in that area, which spans from the foot of Veteran’s Bridge on First Avenue South to South 29th Street, and from First Avenue South to Eighth Avenue South. The project included creating stormwater detention facilities under Veterans Bridge and at the site of the former Land O’ Lakes elevator on Eighth Avenue South.

During the May 30 storm, intersections and low-laying spots in that area had “little to no flooding,” Schaeffer said.

“That was a big win,” he said. “The first time all of these facilities were tested to that type of storm, and we didn’t really have any issues.”

Over the past decade, the city has completed millions of dollars worth of upgrades to the storm sewer system, but more is still needed, Schaeffer said.

The need was painfully obvious on May 30 at the intersection of Fifth Avenue North and North 15th Street, he said. There were 18 inches of standing water in the middle of that intersection that took several hours to drain.

Fixing that would be a “major” project, Schaeffer said. It would require all-new storm sewers down North 15th Street, starting at Third Avenue North all the way to 10th or 12th Avenue North. A portion of North 15th Street would have to be closed for a year or two and the project would likely carry a cost of $3 million to $4 million, he said.

“We’ll have to look at grants and look at other things to try to fix these areas and continue to work on the problem areas we have,” Schaeffer said.

Anticipated storm sewer updates next year just south of downtown are expected to further reduce the strain of flooding in the area. The project will run from Third Avenue South at the southeast corner in front of the Blanden Memorial Art Museum, east to South 12th Street, and then north up to the south side of the roundabout at First Avenue South and South 12th Street.

When the roundabout was constructed, 36-inch drain pipes were installed, Schaeffer said. South of there still has the older, 18-inch drain pipes.

Though Underberg’s property is northeast of the roundabout, Schaeffer said, the updates should help alleviate the flooding problems at 13th and Central.

Schaeffer noted that during the storm sewer studies from a decade ago, several other areas of needed updates were identified. He said he plans to have those areas reevaluated because some of the completed updates and repairs have alleviated the concerns. He said the city may not need to be quite as aggressive in updating the storm sewer system, but noted that the infrastructure will always need to be updated as it continues to age.

“I think now is the time to pause, look at the data, see what happened in the system … and reevaluate those other projects,” he said. “Decide are those the projects that we need to do, or can those be held off for five years or something?”