The Tomahawk Creek Wastewater Treatment Facility Expansion Project (THCWWTF) is a $250M 19MGD project that will start construction during the first part of 2018.  Johnson County has electected to use  the collaborative delivery method Construction Manager at Risk (CM@R) for this project.  McCarthy Building Companies was chosen as the CM@R contractor to work side by side with Johnson County and the design team.  The design team consists of Black & Veatch and HDR.

The existing THCWWTF consists of a mechanical treatment plant and a lagoon.  The facility can treat up to approximately 7 million gallons a day (MGD).  Flow in excess of this capacity is conveyed to Kansas City, Missouri for treatment.  The original site was developed for wastewater treatment in 1955, and numerous projects have occurred on the site since to expand and upgrade the existing facilities to their current state.

Numerous studies have been completed to determine the future of the facility with the most recent study identifying expansion of the facility to 19 MGD as the most beneficial alternative.  The Project Definition Phase of the expansion was recently completed by a Black

& Veatch/HDR engineering team.  The Project Definition Phase focused on: refining the recommended improvements, project costs, and schedule; as well as developing a conceptual level site plan.  This information is summarized in the Preliminary Design Report available on the Johnson County Wastewater website.

As a result of that phase of design the preliminary project scope consists of the following elements of work:

  • Demolition and Decommissioning of the existing facilities
  • Establishing Temporary Provisions for flow diversion
  • Site work inclusive of grading and drainage, underground piping, site roads, and constructing a site bridge
  • Modifications to Lee Boulevard to accommodate site access
  • Influent Junction and Flow Control Structures
  • Influent and Peak Flow Pump Stations
  • Headworks Building
  • Primary Clarifiers
  • BNR Basins
  • Final Clarifiers as well as associated pump stations and splitter structures
  • Tertiary Pump Station
  • Filtration Complex
  • Chemical Disinfection
  • Effluent Reaeration Structure
  • Gravity Thickeners
  • Solids Process Building which includes thickening and dewatering
  • Solids Digestion and Gas Storage
  • Waste Gas Flares
  • Administration / Maintenance Building

The plant will be a campus style plant and the project’s construction schedule will dictate multiple areas of work progressing concurrently.  More information regarding sequencing, logistics, etc. will be provided as part of the project procurement process.  If you have any further questions regarding the scope or other details of the project please submit them using the contact McCarthy section of this website so our team can get connected with you.