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Read a MN Department of Health analysis.

Duluth, MN Drinking Water Quality:

City of Duluth Water Quality Information:

Superior, WI Drinking Water Quality:

Well Testing and Groundwater Information:

Drinking Water

Drinking water in the Duluth area primarily comes from Lake Superior via the City Water Treatment Plant or from private residential wells in rural areas. There are also a small number of systems, mostly from resorts, that draw water from lakes.

The Minnesota Department of Health (MDH) is responsible for ensuring a safe drinking water supply for Minnesotans under the provisions of the federal Safe Drinking Water Act (SDWA).

Learn how the drinking water system in Duluth works in this report by the EPA (1.1MB pdf) or view a slide presentation on the city's infrastructure (3.3 MB pdf).

In the City of Duluth, the Water Treatment Plant draws water from Lake Superior, several miles east of the Lester River from a depth of about 55 m (180 ft), filters it to remove particulate material, disinfects it with chlorine, and then pumps it to reservoirs throughout the City. Staff perform a variety of water quality analyses, some every day, others every 3 months, for a suite of over 100 chemicals. These data may be obtained by contacting either the City Water Treatment Plant in Lakewood Township at 218/525-0834, the Duluth Office of the MDH ( 218/723-4651), or via the main office in St. Paul (651/215-0770).

Since March of 1989 the City has added a caustic soda (50% NaOH) solution until the final pH of the treated water reaches pH 9.00. This is the only corrosion control step that is now taken. Prior to this a low concentration of zinc phosphate was added. At consumer taps the pH will not be that high and usually is in the 8.0 - 8.5 range since the sodium hydroxide does not provide buffering. The final hardness and alkalinity are about the same in the treated water as for the raw water pumped from Lake Superior at 46 ppm which is indicative of a very "soft" water (L. Janson, City of Duluth, Jan 2014). 

Drinking water from private wells is less regulated. There are standards for well construction and well-drillers must be certified by the MDH but there are no monitoring requirements. Prudent homeowners should familiarize themselves with proper operation and maintenance of their well and consider periodic monitoring of their drinking water quality for at least nitrate and total coliform bacteria annually, and at least once for arsenic, lead, volatile organic chemicals and pesticides. There is good information about wells and groundwater in State agency and University of Minnesota Sea Grant websites (see box), and possibly about your particular well in the Computerized County Well Index (CWI) developed by the Minnesota Geological Survey (see box below).

Surface water systems for resorts are also regulated by the MDH (see Noncommunity public water systems below) and now require filtration and disinfection.

MDH is also responsible for source water protection which includes:

  • Wellhead Protection
  • Source Water Assessments
  • Protection of Surface Water Intakes


Over one billion people lack access to safe drinking water worldwide. Learn more about this problem and explore possible solutions.

Diseases caused by unsafe drinking water and poor sanitation are among the world's most serious public health threats, accounting for nearly 80 percent of illnesses in developing countries and killing millions of people - mostly children - each year.

Learn more about this problem and explore possible solutions.

City Water Supply

Community public water supplies serve at least 26 persons or 15 service connections year-round, which includes municipalities, manufactured mobile home parks, etc. Duluth is one of about 1,000 community water supply systems in Minnesota. These systems are required to provide a safe and adequate supply of water under the federal Safe Drinking Water Act (SDWA).

The City of Duluth Water Supply Section of the Department of Public Works is responsible for operating and maintaining the drinking water treatment plant that filters and disinfects our source water from Lake Superior and the pipes and, pumps and reservoirs that deliver the water to our homes.

The Minnesota Department of Health Community Water Supply Unit is responsible for assuring the compliance of community water supply systems with the SDWA. The Unit consists of field staff located in MDH's district offices and compliance staff located in St. Paul. Unit field staff provide on-site technical assistance to community water supply systems and conduct much of the testing for smaller community systems, sending most samples to St. Paul for analyses. All community water supplies are tested for contaminants such as pesticides, solvents, and metals as well as "conventional pollutants" such as bacteria and nitrate.

County Well Index (CWI)

How to find out about your home's well:

The County Well Index (CWI) is a data base that contains information for over 533,000 water-wells drilled in Minnesota. The data are derived from water-well contractors' logs of geologic materials encountered during drilling. Confirmed locations and interpreted geologic well records are available for over 340,000 of the wells. Available data also include casing, screen and pump information.

CWI is now Web accessible at CWI ONLINE.

The data base can be searched and files printed. Files cannot be downloaded.

Noncommunity public water systems

include schools, factories, restaurants, resorts, and churches that are served by their own supply of water (usually a well). These facilities also must provide a safe supply of water under the federal SDWA. They serve either a nontransient (same people each day such as a school, daycare, or factory) or a transient population (different people each day such as a restaurant, motel, or highway rest area), each being regulated. Read more about these systems at the Minnesota Department of Health.