Celebrating the completion of Johnson County Government’s largest-ever project

Aerial view of wastewater treatment facility

Rebuilding Johnson County’s Tomahawk Creek Wastewater Treatment Facility took four years, nine miles of underground utilities, 50,000 cubic yards of concrete and nearly 800 drilled shafts. (Picture six and a half Empire State Buildings stacked on top of each other.)

Yet, for Johnson County Wastewater General Manager Susan Pekarek, the project’s most impressive data point is invisible.

“For the users at home, the transition was seamless,” Pekarek said. “When they wash their dishes or flush their toilet, nobody thinks about it.”

Residents may not have noticed the transition, but the long-term effects of the new facility will impact them – and future generations – for years to come.

Getting to that point, though, was a long, arduous process that began with planning in 2014 and ended last month with a ribbon cutting. All told, the project involved hundreds of people and countless hours from JCW staff as well as partners from engineering firms Black & Veatch and HDR, construction lead McCarthy Building Companies, and Shockey Consulting, which oversaw community engagement.

“Making this type of investment in the infrastructure of Johnson County is crucial, and the project was a success due to the talent and expertise of everyone involved,” said Chairman Ed Eilert, Johnson County Board of County Commissioners.

At the Tomahawk ribbon cutting ceremony, more than 170 people gathered to mark completion of the county’s largest capital project to date – and to celebrate the project’s many achievements. Chief among them are ratepayer savings and improved water quality. In fact, the technology used at Tomahawk will reap environmental benefits that will positively impact Indian Creek, as well as the downstream waters of the Missouri and Mississippi rivers, all the way to the Gulf of Mexico.

“The creativity and collaboration that went into this project is incredible,” said County Manager Penny Postoak Ferguson. “The project achieved all goals, including utilizing the most cost-effective solution and improving water quality.”

From the 1950s to the Future

Graph showing revenue savings for the facility through 2050

The Tomahawk Creek Wastewater Treatment Facility, located at 10701 Lee Blvd., is one of six treatment sites owned and operated by the county. Johnson County Wastewater’s assets and infrastructure are worth more than $3 billion and, as systems have aged, JCW engineers and technicians have focused on maintaining, repairing and rehabilitating the County’s 2,300 miles of sanitary sewers and 31 pump stations.

But the Tomahawk facility was built in 1955 and now serves about 150,000 residents from parts of Leawood, Overland Park, Olathe and Prairie Village, a significantly larger population than the facility was built to manage.

In the 1980s, JCW implemented a workaround to keep up with demand by diverting part of Tomahawk’s daily flow to Kansas City, Missouri, for treatment. By the 2010s, nearly 60 percent of Tomahawk’s incoming flow was being sent to KCMO for treatment – and at two to three times the cost to treat it locally.

Plus, Kansas City is facing significant improvements to its infrastructure which would have increased costs even more.

In addition, the Environmental Protection Agency and Kansas Department of Health and Environment had strengthened limits on the amount of ammonia, nitrogen, and phosphorus that could be discharged.

“It was time for us to do something about the issue,” said Tami Lorenzen, JCW Assistant Chief Engineer - Integrated Planning. “There were so many issues impacting Tomahawk.”

The JCW team first started exploring ways to transform the 1950s-era wastewater plant into a modern treatment facility over a decade ago, said Pekarek. Along with Chief Engineer Aaron Witt, they evaluated three options: continue to divert flow to KCMO, build a different treatment facility or rebuild Tomahawk.

In the end, they determined that building an expanded facility with capacity to treat all of the area’s wastewater was a lower cost, longer-term solution than continuing to treat only a portion of the flow. It’s projected to save ratepayers $785 million over 35 years when compared to other alternatives. What’s more, JCW will have greater control over managing the cost of treatment and, by extension, the sewer rates charged to customers.

“This was the best solution on every front,” Lorenzen said. “Cost, water quality and the long-term health of our community.”

From the facility plan through design to construction, the project cost $334 million and will save JCW customers $16 million a year. What’s more, it will treat up to 19 million gallons of wastewater a day, while the previous capacity was 7 MGD. JCW is funded by ratepayers, not tax revenue.

“The collaboration of JCW staff, our design engineers Black & Veatch and HDR, and our contractor McCarthy Building Companies was critical to the success of this complex project,” said Aaron Witt, Chief Engineer at JCW

Creativity at Work

Infographic showing project highlights, including underground utilities, pumps, tower cranes and more

As the teams of engineers mapped out an improved wastewater facility, they took advantage of new but proven technologies that improved water quality while saving money. Among them:

  • Biological Nutrient Removal. BNR uses bacteria to break down and reduce the biological components of wastewater, namely ammonia, nitrogen, and phosphorus, before they’re discharged into surface or groundwater. Nutrient compounds like nitrogen and phosphorus can act like a fertilizer, causing algae breakouts, which can kill fish.

“The previous facility had more basic treatment technology from the 1960s,” said Lorenzen. “With this new technology we’ll have much better water quality for aquatic life.”

  • Disk filtration system. Modern wastewater treatment facilities are designed to carry both wastewater and stormwater, but, unlike other area facilities, the previous Tomahawk system did not. When stormwater gets into the wastewater system, called peak flow, it’s difficult and expensive to treat. The Tomahawk team looked at building additional storage facilities to manage peak flow, but the price tag was steep – $250 million.

Instead, the team worked with state regulators to negotiate the use of disk filters, a new technology for JCW.

“The filters allow us to reduce phosphorus and polish the water daily, but they’re also used to treat wet weather flows up to 172 million gallons a day when we get extreme rainfall events,” said Witt. “Utilizing this technology allowed us to save $200 million over an alternative to store the wet weather flows in large underground tanks.”

Overcoming Challenges

County staff and officials pose for a ribbon cutting at the improved Tomahawk Wastewater Facility

Not only did the teams manage the county’s largest infrastructure project to date – the facility has a 30 percent larger footprint than the old one – they did so under extreme conditions.

“I can’t say enough about the teams that worked on this project,” said Lorenzen. “The collaboration was incredible.”

They worked through the wettest year on record in the Kansas City region, navigating more than 64 inches of rain from Oct. 2018 to Oct. 2019. Because the site was almost entirely in the 100-year flood plain, the wet weather made construction much more complicated.

The site was raised using fill from the site, plus some additional material. An overflow channel was constructed to serve as a relief point for Indian Creek floodwaters.

On top of that, they had to battle the pandemic. Crews worked through COVID-19, navigating the shifting guidelines, eventually completing the project on time and on budget.

“Watching the facility go through startup and operate for months now, I am particularly proud of the operations staff that continues to work 24 hours a day, seven days a week through storms and heat to provide a vital health and environmental service for our community,” said Alex Szerwinski, JCW’s Managing Engineer, Existing Infrastructure – Treatment & Pumping.

While JCW staff have moved on to the next infrastructure improvement project – Nelson WWTF, its oldest facility – the Tomahawk project will remain a professional highlight for many involved in the project.

For Lorenzen, this project was a “once-in-a-career project.”

“This was such an important project and I felt lucky to be able to work on it,” said Lorenzen. “Not just the magnitude – our largest project – but also because of the positive benefits that we were able, as a team, to realize for customers and residents of Johnson County.”

To meet three of the employees who worked on this project, we invite you to turn to page 22 for Three Questions for Employees. To learn more about the project, please visit www.JCWTomahawk.com.