Wastewater Digester Lid & Miscellaneous Improvements

Wastewater Digester Lid & Miscellaneous Improvements

Project Manager

City Engineering / David Barth, P.E.

SUA Project No. 16SG01

Visit the GIS Infrastructure Map to see where city infrastructure projects are happening.

What We're Doing

The City of Stillwater and Stillwater Utilities Authority is making improvements to multiple facilities at the Wastewater Treatment Plant. These include: a new lid for Digester A, an automatic transfer switch, a gas collection system used for fueling the heat generation system, basin drains, fencing and roofing. 

Anticipated Milestones

  • Anticipated Date (Design): Design began FY2017
  • Anticipated Date (Construction): Construction began August 2018
  • Anticipated Date (Completion): November 2020

Benefits of the Project

Sludge digestion produces corrosive gases that have led to the deterioration of Digester A and B lids. 

Budget & Funding

  • Year Funded: FY2017
  • Funding Source: Wastewater Fund
  • Project Budget: $3.1 Million
  • Expenditures to Date: $2.5 Million

Project Management


May 12, 2017: The design kickoff meeting between the City and Freese and Nichols was held on May 8th. The study phase is expected to last five months.

November 15, 2017: Bid Opening for the Automatic Transfer Switch phase occurred November 18th.

January 22, 2018: The study phase for the miscellaneous improvements at the WWTP is now complete and we are moving into final design to include:

  • New fixed cover for Digester A,
  • Gas collection/handling and safety equipment for all three digesters,
  • Aeration basin access and drainage improvements,
  • New perimeter fencing surrounding the sludge fields and plant facilities, and
  • New roofing on four buildings at the WWTP.

Construction on the Automatic Transfer Switch will begin end of January 2018.

February 27, 2018: Notice to Proceed has been issued to Dane & Associates Electric Co. for the automatic transfer switch replacement.

May 23, 2018: Design Engineer submitted preliminary design for the Digester Lid.

November 19, 2018: Final design is underway and expected to be submitted by February 2019. Bidding and Construction phase will soon follow.

May 31, 2019: Final design is nearly complete. Advertisement for bids is scheduled for June 2019. Construction will likely begin in the fall and is anticipated to last 14 months.

August 20, 2019: Bid for the Digester Lid replacement was awarded to BRB Contractors, Inc.

November 13, 2019: Pre construction meeting to be held on November 18th. 

October 2, 2019: Notice to Proceed issued.

January 23, 2020: Trees and fencing have been cleared from the sludge field perimeter.

April 23, 2020: Roofing on the Admin Building, Sludge Pump Building, Maintenance Building, and Digester Control Building is 80% complete. Barbwire fencing is complete along 19th Avenue and in progress along the other boundaries. Work on the Aeration Basins will begin at the end of April, 2020. 

June 24, 2020: Work is nearly complete on Aeration Basin 1, and the Admin Building roof work is awaiting inspection. 

July 29, 2020: Aeration Basins 1 and 2 are complete and Digester Lid A is underway.

August 27, 2020: Aeration Basins 1, 2 and 3 are complete. The Digester Lid is being welded and prepped for coating.

November 11, 2020: Digester Lid A is in place and the coatings are being applied. The waste gas piping and other digester gas improvements are progressing.

January 4, 2021: Construction of the waster gas burner and gas piping is 90% complete. Digester Lid A has been coated and is currently waiting to be installed.

February 18, 2021: The waster gas burner and gas piping are operational and the sludge from Digester A is being pumped out. 

April 8, 2021: Damage was discovered on the walls of Digester A after the sludge was pumped out. The concrete wall is currently being repaired. 

June 2, 2021: Digester A concrete has been hydro blasted. 

August 31, 2021: All work on the project is now complete. 

Actions authorized by Stillwater Utilities Authority (SUA):

  • 4.17.14  | SUA-17-08 |  Authorization of Professional Services Agreement

  • 12.04.17| SUA-17-42 |  Bid Recommendation for Automatic Transfer Switch

  • 1.22.18  | SUA-18-05 |  Professional Services Contract Amendment for Final Design

  • 8.19.19  | SUA-19-33 |  Bid Recommendation for Digester Lid Replacement and Miscellaneous Projects at the WWTP


Digester lid on scaffolding being welded

View showing the poor condition of the digester lid at the waste water treatment plant