Tomahawk Creek Wastewater Treatment Facility Improvements

Johnson County Wastewater Tomahawk Creek WWTF Expansion

Tomahawk Creek Wastewater Treatment Facility Improvements

Constructed in 1955, the Tomahawk Creek Wastewater Treatment Facility has expanded over the years to treat wastewater flows from parts of Leawood, Overland Park, Olathe, and Prairie Village, Kansas. The facility is a 10 Millions of Gallons per Day trickling filter plant but can only treat 4-6 MGD and still comply with its discharge limit for ammonia. The remainder of the 15 MGD from the tributary area bypasses the plant through a 72-inch interceptor that conveys it to Kansas City, Missouri’s system. 

In 2006, in response to a regulatory directive, Johnson County Wastewater retained HDR to perform a feasibility study for converting the facility from antiquated trickling filters to state-of-the-art nutrient removal. Due to the costs of the upgrades, an interim process improvements project was developed for quick implementation to address the permit compliance issue. We completed the design of this interim project, which consisted of replacing the trickling filter distributors and adding controllable drives, adding chemically enhanced coagulation to both primary and secondary clarifiers, and incorporating improvements to address operational and maintenance concerns. 

In 2011, JCW returned to HDR to update the previous study. This update was driven by new information from Kansas City on anticipated rate changes for flows discharged to Kansas City. The Study Update was completed in 2013. 

One key aspect of the study was a comprehensive analysis of wet weather management options that employed various combinations of treatment, storage, and conveyance. Another key was the financial evaluation, both net present value and cash flow, of treatment of all or part of this flow by Kansas City. The outcome was a well-defined path forward at Tomahawk, including full treatment of all flow, dry and wet, which enabled JCW to move forward with implementation of this $300M project.

In 2014, the Black & Veatch/HDR team was selected for final design, permitting, and bid phase services. Improvements to the 19 MGD wastewater treatment facility were to include biological nutrient removal, auxiliary treatment for peak wet weather flows up to 172 MGD, and biosolids processing. 

Construction officially began in April 2018 with major construction scheduled to be completed by spring of 2022. The long-term infrastructure investment will utilize the latest proven technologies, protect the environment, and improve water quality in Indian Creek and for downstream communities. 

To learn more about the project, check out the project website.

Johnson County Wastewater Tomahawk Creek WWTF Expansion
Johnson County Wastewater

Lenexa, KS
United States

19 MGD average