Lime Softening

Lime Feed System

Project Manager

Water Utilities Engineering / Bill Millis, P.E.

SUA Project No. 16WG08

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What We're Doing

The City of Stillwater and the Stillwater Utilities Authority will be upgrading and improving the lime softening system at the Water Treatment Plant (WTP).

Anticipated Milestones

  • Anticipated Date (Design): TBD
  • Anticipated Date (Construction): TBD
  • Anticipated Date (Completion): TBD

Benefits of the Project

The Kaw Lake water flowing into the WTP has an average hardness that classifies it as moderate to hard water. A lime softening process is used to remove this hardness and reduce the potential for scaling inside the City's water lines and also inside our customer's plumbing. Customers may notice the benefits of a softer water because it reduces the amount of soap needed for washing laundry and bathing, leaves dishes shinier and cleaner and preserves the life of coffee makers, water heaters and other appliances that use water.

Budget & Funding

  • Year Funded: FY2017
  • Funding Source: Water Fund
  • Project Budget: $615,000
  • Expenditures to date: $332,000

Project Management


February 7, 2017: Black and Veatch has been hired to provide conceptual design services.

September 6, 2017: Evaluation of the filters added to Black and Veatch's scope in order to optimize filtration and improve overall functionality.

March 12, 2018: After evaluation most of the process and chemical feed systems at the WTP, a priority has been assigned to each individual component. The Project Team will prepare a Facilities Plan to develop a conceptual and phasing plan for the work to include lime softening. The lime feed system improvements will be on hold until the Facilities Plan is complete. 

April 15, 2019: The first workshop for the Facilities Plan is anticipated to occur in May 2019. The Lime Feed System replacement effort will remain on hold until the Facilities Plan is complete.

August 13, 2019: The Facilities Plan is 75% complete.

October 28, 2019: The Facilities Plan is 90% complete. The Project Team is considering phasing options while striving to minimize project costs. 

January 22, 2020: Alternative Project Delivery (APD) methods are being considered for the overall WTP needed improvements which have a combined design and construction cost estimate of up to $60 Million.

April 23, 2020: With the recent completion of pilot tests, summary reports are being reviewed by City staff. New insights to optional treatment strategies and project sequencing are being evaluated for a holistic approach to needed upgrades at the WTP.

July 14, 2020: Staff is evaluating the costs of various phasing scenarios associated with existing WTP rehabilitation versus construction of a new WTP in the future.

September 28, 2020: A presentation was delivered to City Council and SUA describing various scenarios for the future of the Water Treatment Plant and the Raw Water Supply Line. The presentation included early planning level cost estimates and rankings, among other topics. Staff will move forward with solicitation of a Designer/CMAR team (CMAR: Construction Manager at Risk). 

Actions Authorized by Stillwater Utilities Authority (SUA)

  • 1.9.17  I  SUA-17-01  I  Professional Services Agreement

  • 7.17.17  I  SUA-17-22  I  Amendment to Professional Services Agreement

  • 9.10.18  I  SUA-18-34  I  Request for Additional Expenditures and to Execute Contract Amendments to the Professional Services Agreement

  • 9.28.20  I  Presentation I  Stillwater Water Treatment Plant & Raw Water Supply Scenarios


Existing Lime Feed System

photo of old lime fee system in the lime silo

existing lime silos