Water Quality Report

Secretary's Award

The Mid-Dakota Rural Water System has supplied twenty-three consecutive years of safe drinking water to the public it serves and has been awarded the Secretary's Award for Drinking Water Excellence by the South Dakota Department of Environment and Natural Resources.


Water Quality

This report is a snapshot of the quality of the water that Mid-Dakota provided last year. Included are details about where your water comes from, what it contains, and how it compares to Environmental Protection Agency (EPA) and state standards. We are committed to providing you with information because informed customers are our best allies.

Water Source

We serve more than 6,500 customer accounts, or a population greater than 32,700, an average of 6,204,000 gallons of water per day. We get our water from the Oahe Dam on the Missouri River which is a surface water source.  The state has performed an assessment of our source water and they have determined that the relative susceptibility rating for the Mid-Dakota Rural Water public water supply system is medium.

For more information about your water and information on opportunities to participate in public meetings, call (605) 945-0437 and ask for Bill Sarringar.

Additional Information

The sources of drinking water (both tap and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs and wells. As water travels over the surface of the land or through the ground, it dissolves naturally-occurring minerals, and can pick up substances resulting from the presence of animals or from human activity.

Contaminants that may be present in source water include:

  • Microbial contaminants, such as viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations and wildlife.
  • Inorganic contaminants, such as salts and metals, which can be naturally-occurring or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining or farming.
  • Pesticides and herbicides, which may come from a variety of sources such as agriculture, urban stormwater runoff and residential uses.
  • Organic, chemical contaminants, including synthetic and volatile organic chemicals, which are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater runoff, and septic systems.
  • Radioactive contaminants, which can be naturally-occurring or be the result of oil and gas production and mining activities.

In order to ensure that tap water is safe to drink, EPA prescribes regulations which limit the amount of certain contaminants in water provided by public water systems. Food & Drug Administration regulations establish limits for contaminants in bottled water which must provide the same protections for public health.

Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that water poses a health risk. More information about contaminants and potential health effects can be obtained by calling the Environmental Protection Agency's Safe Drinking Water Hotline (800-426-4791).

Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, persons with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers. EPA/Center for Disease Control guidelines on appropriate means to learn the risk of infection by Cryptosporidium and other microbial contaminants can be obtained by calling the Environmental Protection Agency's Safe Drinking Water Hotline (800-426-4791).

If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. The Mid-Dakota Rural Water public water supply system is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components. When your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes before using water for drinking or cooking. If you are concerned about lead in your water, you may wish to have your water tested. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline or at http://www.epa.gov/safewater/lead.

Detected Contaminants

The table entitled "2023 Water Quality Test Results" lists all the drinking water contaminants that we detected during the 2022 calendar year. The presence of these contaminants in the water does not necessarily indicate that the water poses a health risk. Unless otherwise noted, the data presented in this table is from testing done January 1 - December 31, 2023. The state requires us to monitor for certain contaminants less than once per year because the concentrations of these contaminants are not expected to vary significantly from year to year. Some of the data, though representative of the water quality, is more than one year old.

What Treatment Does Our Water Receive?

Lake Oahe, a reservoir on the Missouri River, above the Oahe Dam supplies the raw water for Mid-Dakota. The raw water is pumped to two raw water storage tanks located at the chemical feed building. The water passes through the chemical feed building where chlorine gas in injected into the raw water pipeline. The water then travels about four miles to the 13 1/2 million gallons per day (MGD) capacity water treatment plant. As it enters the plant, aluminum chlorohydrate is added before the water enters the flocculation basin to form pin floc before entering the filters. After the flocculation basin the water then enters the ultrafiltration membranes from Zenon (GE Water & Process Technologies). The water is then piped to the clearwell and on the way to the clearwell, it is given caustic soda for pH adjustment. Chlorine and anhydrous ammonia are injected to form chloramines, a longer-lasting disinfectant. The water is then pumped out to the distribution system and into customers' homes.

Definition of Terms

These definitions are provided to assist you in understanding our water quality test results and the following discussion of the results.

ACTION LEVEL (AL) - The concentration of a contaminant which, when exceeded, triggers treatment or other requirements which a water system must follow. For Lead and Copper, 90% of samples must be below the AL.

TREATMENT TECHNIQUE (TT) - A required process intended to reduce the level of a contaminant in drinking water. For turbidity, 95% of sample must be less than 0.3 NTU.

MAXIMUM CONTAMINANT LEVEL (MCL) - This is the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology.

MAXIMUM CONTAMINANT LEVEL GOAL (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.

RUNNING ANNUAL AVERAGE (RAA) - Compliance is calculated using the running annual average of samples from designated monitoring locations.

NOTE: MCLs are set at very stringent levels. To understand the possible health effects described for many regulated contaminants, a person would have to drink 2 liters of water every day at the MCL level for a lifetime to have a one-in-a-million chance of having the described health effect.


  • ppb = parts per billion or micrograms per liter (ug/l)
  • ppm = parts per million or milligrams per liter (mg/l)
  • pCi/l = picocuries per liter (a measure of radioactivity)

2023 Water Quality Test Results

2023 Water Quality Test Results
Substance Date Last Tested Highest Level Detected Range of Detection   Ideal   Goals (MCLG) Highest Level Allowed (MCL) Likely Source of Substance
 Alpha emitters, pCi/l 11/30/22 4 ND-4 0 14 Erosion of natural deposits. 
 Antimony, ppb  3/22/22 0.32   6 6 Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder.
 Arsenic, ppb 3/22/22
2   0 10 Erosion of natural deposits; runoff from orchards; runoff from glass and electronics production wastes.
Atrazine, ppb 11/13/19  0.280  ND-0.280 3 Runoff from herbicide used on row crops.
 Barium, ppm  3/22/22 0.035   2 2 Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits. 
Copper, ppm 8/24/22 0.3 # sites >1.3   - 0 0 AL=1.3 Corrosion of household plumbing systems; erosion of natural deposits; leaching from wood preservatives
Fluoride, ppm 10/04/23 0.50   <4 4 Erosion of natural deposits; water additive which promotes strong teeth; discharge from fertilizer and aluminum factories
Haloacetic Acids, ppb (RAA) 3/20/23 20   0 60 By-product of drinking water chlorination.  Results are reported as a running annual average of test results.
Lead, ppb 8/31/22 1

>15 AL-0

0 AL=15 Corrosion of household plumbing systems; erosion of natural deposits
 Selenium, ppb  3/22/22 0.96   50 50 Discharge from petroleum and metal refineries; erosion of natural deposits; discharge from mines. 
 Total Coliform Bacteria, pspm   1 positive samples 0 1 Naturally present in the environment. 
Total Trihalomethanes, ppb (RAA) 11/07/23 38.50   0 80 By-product of drinking water chlorination.  Results are reported as a running annual average of test results.


2023 Table of Detected Unregulated Contaminants For Mid-Dakota Rural Water (EPA ID 2175)

The EPA is required to test for possible contaminants in your drinking water every five years.  These contaminants are not regulated and acceptable levels have not been set by EPA.  As a means of informing the public, the detected levels of these unregulated contaminants are listed below.


ug/L: micrograms per liter
Substances Level Detected Units Date Tested Range
Lithium 60 ug/l 4/12/23 52.0-60