Tomahawk Creek Wastewater Treatment Facility (WWTF) Expansion

Project Name: Tomahawk Creek Wastewater Treatment Facility (WWTF) Expansion

Date Authorized: July 31, 2014 (project def.); May 5, 2016 (design); March 2, 2017 (pre-construction); March 29, 2018 (construction)

Project Authorization: $4,100,000 (project definition); $21,387,000 (design); $2,680,000 (preconstruction); $306,678,678 (construction funding including $23,131,462 (engineering construction services), $267,892,045 (Construction GMP, and bonds, PAF, and other project costs)) Total Project Authorization = $334,990,678

Delivery Method: Construction Manager at Risk (CMAR)

Design Firm: Black & Veatch/HDR Engineers

Contractor: McCarthy Building Companies, Inc. (CMAR)

Completion Date (Estimated): March 1, 2022 (Substantial Completion)

Major Milestones:

  • Milestone 1, liquids treatment is contractually October 25, 2021. However, the team began commissioning activities for this Milestone on August 30, and began discharging treated effluent to Indian Creek on Monday, September 20. The Facility is operating at roughly 80% of its current flow and will begin receiving all flow over the subsequent weeks.
  • The solids treatment Milestone 2 deadline is November 29, 2021. Solids will be discharged to KCMO until this milestone is complete.
  • There are currently 8 additional weather days above the allowed number of days in the contract. This essentially pushes back the milestone deadlines; however, McCarthy plans on meeting each milestone on time.

Future Pending Action(s):

  • None.


  • Maintaining a safe and productive work environment, especially relating to COVID-19, is still a high priority for the team.
  • McCarthy is currently on schedule and on budget.
  • 9 out of 12 process startups have been completed to date.
  • Construction is approximately 96% complete as per budget spent.
  • Underground utilities are 100% complete.
  • Leakage testing on water retaining structures is approximately 100% complete (48 out of 48 tests).
  • The majority of work remaining is on the solids treatment side and includes interior piping, mechanical work, electrical, plumbing, HVAC, installation of equipment, and finalizing the facility control system programming and hardware.
  • The second digester lid was lifted into place on September 1. One more fixed cover and a flexible membrane remain critical path.
  • Concrete paving and sidewalk and asphalt continue to be installed throughout the site.
  • Restoration of Lee Blvd and the soccer field parking lot have been completed.
  • The Bike Trail restoration and onsite paving will finish by the end of October.
  • Landscaping will begin in October through November.
  • The team has finished posting information on wastewater processes to Johnson County
  • Facebook page and the project website ( about wastewater treatment at the Tomahawk Creek WWTF as part of a monthly educational outreach series. To date, 23 segments have been posted.
  • The team will be offering tours of the facility to BOCC officials in November of 2021.