Let’s face it, for most people, the less said about sewer plants and wastewater treatment, the better.
It’s down the drain. Out of sight, out of mind, and you just hope everything is handled properly.
But for anyone who flushes a toilet in Johnson County, Thursday’s groundbreaking at the Tomahawk treatment plant in Leawood was a big deal. The county is demolishing and completely rebuilding the plant on a 60-acre site at 10701 Lee Boulevard, near Mission Road.
The $335 million project is the most expensive and one of the most complex public works projects in county history. And the plant’s modernization will affect every property owner's sewer bill, with a few dollars of added expense per month. But it also entails big savings in the long run over what costs could have been without the new plant.
Tomahawk was built in 1955 and has expanded over the years to treat flows from parts of Leawood, Prairie Village, Overland Park and Olathe. The current facility, which serves about 150,000 residents, could only handle about 40 percent of the flow, or about seven million gallons daily. So Kansas City has been treating about 60 percent, at a cost of about $16 million per year. The plant’s shortcomings affected all of Johnson County’s 450,000 wastewater customers through their sewer charges.
Once rebuilt, the plant will handle 100 percent of the flow there, giving the county more control over long-term expenses. The work starts now and should be completed by the end of 2021.
The overhaul will also be better for the environment, providing cleaner water flowing through Indian Creek to the Blue River and all the way to the Gulf of Mexico. And although the plant is expanding on land near Leawood City Park, not far from Hallbrook, the odor conditions should improve rather than worsen.
“It’s the best alternative for controlling our rates long term, as well as being the best environmental solution,” said Susan Pekarek, general manager of Johnson County Wastewater.
The county could have continued to rely on Kansas City to treat most of the wastewater from the aging Tomahawk plant’s service area.
But Kansas City’s sewer costs are skyrocketing under a wastewater cleanup agreement with the Environmental Protection Agency. As a big wholesale customer of Kansas City, Johnson County would have continued to incur those increasing costs, adding hundreds of millions of dollars to its payments to Kansas City over 25 years.
During the 3 1/2 years of construction while the plant is shut down, Johnson County will send all its flow from the Tomahawk service area to Kansas City. Sewer rate charges will rise about 7.75 percent per year during that time to cover that cost.
But by 2022, rate increases should drop below 6 percent per year.
The average residential customer sewer charge is $35 per month. With all factors including the Tomahawk plant, average residential rates will increase by about $2 per month over time. (For comparison, the average monthly household sewer bill in Kansas City is more than $60, and water charges are on top of that.)
Once reopened, the Tomahawk plant will be able to accommodate up to 19 million gallons per day, which allows for growth and should extend its life another 75 years.
The plant is near some upscale residential neighborhoods. Some have wondered whether the expanded plant would add to odors at the facility. But actually, Pekarek and others said, the modernization should improve odor conditions.
“The technology we have now is prone to odors, particularly in the spring and fall,” Pekarek said. “With newer technology you tend to have less odors overall.”
City Councilman Jim Rawlings, who represents that part of Leawood, says odors have been a sporadic rather than a persistent problem along Lee Boulevard.
“You can drive through the park and get a smell if the weather is just right or wrong,” he said. “When the humidity level is higher you get the effluent smell as they call it.”
He’s optimistic the situation will improve.
“I had the opportunity to visit a similar plant in Broomfield, Colorado,” he said of the improved technology. “There was no smell at all.”
The plant meets current regulatory requirements but wasn’t going to meet new, more stringent water quality regulations for dealing with excess nitrogen, phosphorous and ammonia, said Tami Lorenzen, the project’s engineering manager with Johnson County Wastewater. The upgrades will fulfill those requirements.
“The nutrient removal we’re doing here is very advanced compared to some facilities locally,” she said.
So this project will improve Tomahawk Creek's and Indian Creek’s stream health, she said. Currently, the streams get very low and stagnant over the summer, she said, which adversely affects fish health and encourages algae growth. The treatment plant expansion will maintain sufficient flow, she said, increasing oxygen levels and preventing algae accumulation.
The expansion will take up about 30 percent more land but will remain on wastewater property and will not encroach on Leawood City Park. The county will work with Leawood on preserving as many trees as possible and on landscaping improvements, primarily on the north.
But the site will be raised out of the floodplain, so the treatment plant's brick buildings will be much more visible than they have been before. Leawood Mayor Peggy Dunn said the county has worked well with the city on making the building designs as aesthetically pleasing as possible.
Part of Lee Boulevard will be raised above the 100-year flood elevation to access the plant during high water conditions. Lee Boulevard will remain open during construction, but there will be intermittent road detours. Mission Road won't change.
The construction will also close part of the Indian Creek trail that runs north of the facility, from now through fall 2021. Trail users can still traverse the area by using an existing trail south of the facility.
A map of the trail detour is at https://www.jcwtomahawk.com/copy-of-schedule-maps.
More information is available at https://www.jcwtomahawk.com/.
The project was designed by Black & Veatch and HDR Engineering. The construction manager is McCarthy Building Companies, which has done major sewer plant projects around the country.