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City of Waukesha Diversion



  • The DNR approved the city of Waukesha’s diversion application to divert up to 8.2 million gallons per day.
  • The city purchases drinking water from the city of Milwaukee, whose water source is Lake Michigan.
  • The city of Waukesha discharges its treated wastewater to the Root River, a tributary of Lake Michigan and the Fox River. Treated wastewater, up to the volume of annual average diversion, is then discharged to the Root River. Wastewater in excess of the diversion volume is discharged to the Fox River. The source of additional wastewater is inflow and infiltration into the city’s sewer system.
  • Waukesha applied to the DNR for a diversion of Lake Michigan water under the Great Lakes Compact and Agreement as a “community in a straddling county” in a revised application in 2013.
  • The DNR forwarded its application review to the Great Lakes Regional Body and Compact Council in 2016, which include representatives from all 10 Great Lakes states and provinces. The Compact Council approved Waukesha's diversion application with conditions including:
    • A reduced diversion volume of 8.2 million gallons per day;
    • A smaller diversion area of only the area currently served by the Waukesha water utility;
    • Monitoring wastewater impacts to the Root River; and
    • Annual reporting to the Great Lakes states and provinces on the diversion.
  • The DNR’s approval came in 2021 after all permits and approval needed to implement the diversion were in place.
  • The city applied for a switch to a Lake Michigan water source because its previous source, groundwater from the deep aquifer, was contaminated by high radium concentrations that required costly treatment. As a result, the city was under an amended court order to comply with state and federal radium standards by September 2023.
  • The city worked with the DNR to test its new water source and ensure that changing to Lake Michigan water would not cause unexpected water quality problems.
  • The city is required to monitor water quality in the distribution system following standard Safe Drinking Water Act requirements.

Find more information on the city of Waukesha’s transition to a Lake Michigan water supply on the Great Water Alliance website.

Approval Documents

Approval Documents

State of Wisconsin Diversion Approval

The DNR approved the City of Waukesha’s diversion and the water supply service area plan in June 2021. The City of Waukesha has obtained all necessary federal, state and local permits to implement the diversion.

Findings of Facts, Conclusions of Law, Decision, June 29, 2021.
Water Supply Service Area Plan Approval, June 29, 2021.

Compact Council Approval

City of Waukesha Diversion Compact Council Final Decision – June 2016.

Other Permits and Correspondence

The DNR has completed a final environmental impact statement (EIS) for the proposed project and has issued a determination of compliance with the Wisconsin Environmental Policy Act. For more information, see Waukesha Water Diversion EIS.

The City of Waukesha has obtained permits and approvals to discharge wastewater to the Root River, for wastewater facilities, for pipeline stream and wetland crossings, for the water supply pipeline, construction stormwater management from the Department of Transportation and construction authorization from the Wisconsin Public Service Commission.

Date Title
10/31/2023 Letter to Update August 2023 QAPP
08/02/2023 City of Waukesha Quality Assurance Program Plan - Root River Monitoring
07/06/2023 DNR Letter to Waukesha re. Root River Monitoring
04/26/2023 DNR Letter to Waukesha re. Root River Monitoring
04/06/2023 2023 Water Conservation Plan Update
05/13/2021 Waukesha Pharmaceuticals and Personal Care Products Recycling and Reduction Plan
02/03/2021 Water Conservation Plan Update to DNR
02/03/2021 City of Waukesha Conservation Report to Public Service Commission
11/18/2020 City of Waukesha Post-Return Flow Root River Monitoring Program
11/16/2020 Approval of return flow pipeline
08/21/2020 Wetland and waterways permit amendment
03/06/2020 Approval of return flow pipeline and outfall facilities
02/24/2020 Approval of phosphorus treatment upgrades, return flow pump station, and other alterations
12/30/2019 City of Waukesha WPDES permit
12/30/2019 City of Waukesha WPDES notice of final determination
12/30/2019 City of Waukesha WPDES fact sheet
12/13/2019 Wetland and Waterways permit decision
04/25/2019 FHWA Hardship Application Approval
04/08/2019 NEPA CE Analysis for FHWA Hardship Application Approval
02/11/2019 Approval of August 2018 Clean Water Plant Facility Plan Amendment
01/28/2019 EIS Information Needs Letter
01/28/2019 GWA Incompleteness Letter
11/09/2018 Milwaukee Route Alternatives Descriptions
11/09/2018 Milwaukee Route Alternative Panels
11/01/2018 EIS Information Needs Response
10/22/2018 EIS Information Needs Response
09/21/2018 EIS Information Needs Response
08/30/2018 Waukesha Clean Water Plant Facility Plan Amendment (available upon request)
08/13/2018 WI SRF WIFRA Notification letter
06/07/2018 EIR route alternative panels
06/07/2018 EIR route alternative descriptions
03/23/2018 Waukesha supplemental environmental impact report
12/21/2017 Waukesha WPDES individual permit application
12/18/2017 RB-CC Letter re: Milwaukee water supply
11/30/2017 DNR letter regarding Milwaukee water supply
11/29/2017 Waukesha letter to DNR re: water supplier
06/26/2017 DNR and PSC WEPA letter
02/27/2017 Pre-Return Flow Root River Data Collection Plan
07/13/2016 Waukesha return flow planning limits letter

Application Materials

Application Materials

The City of Waukesha submitted a revised application for a Lake Michigan diversion in October 2013.

Regional Review

The DNR submitted the City of Waukesha application to the Regional Body and Compact Council in January 2016. Compact Council decision documents are available from the Compact Council.

DNR Review

Prior to submitting the City of Waukesha Application for Regional Review, the DNR reviewed the City of Waukesha diversion application between 2010 and 2015. The DNR did additional review for permit and approval applications to implement the diversion after the Compact Council approval of the diversion.

The DNR also used the EIS process to analyze environmental effects and alternatives of the proposed Waukesha diversion under the Wisconsin Environmental Policy Act (WEPA) and Chapter NR 150, Wis. Adm. Code. As a result of this process, the department issued a final EIS in 2019.

The DNR issued a Technical Review and a response to comments in 2015.

In addition to the Regional Review public participation process, the DNR held public comment periods in 2010, 2013 and 2015.