Drinking Water Advisory

PWSID: 64202545
DNR Violation: 117903058

MC-Monroe Co.

Drinking Water Advisory

Recent water quality samples for Tomah Water showed nitrate concentrations that exceeded the maximum contaminant level (MCL) allowed. Levels of nitrate vary throughout the year but may not exceed an average of 10 milligrams per liter (mg/l). A sample collected at Well 14 on 5/13/2025 had a concentration of 14.4 mg/L and a sample collected on 5/15/25 had a concentration of 7.85 mg/L resulting in an average concentration of 11.13 mg/L. This is a violation of State and Federal Safe Drinking Water Regulations.

The Tomah water system gets its water from 5 different wells. Only one of the five wells tested above the Nitrate MCL. This well was immediately inactivated and is no longer supplying drinking water to the community.

All water in the distribution system is below 10 mg/L. When nitrate concentrations exceed the safe drinking water standard, we advise consumers to take the following precautions:

DO NOT GIVE TAP WATER TO INFANTS. Infants less than six months of age who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue baby syndrome. Blue baby syndrome is indicated by blue grey skin. Symptoms develop rapidly, with health deteriorating over several days. If these symptoms occur, seek medical attention immediately.

DO NOT PREPARE BABY FORMULA, JUICE, or DRINKS for infants under six months with this tap water.

FEMALES WHO ARE OR MAY BECOME PREGNANT SHOULD NOT CONSUME THIS WATER. (Consumption means drinking the water or eating foods prepared with the water, such as soups, juices, and coffee.) There is some evidence of an association between exposure to high nitrate levels in drinking water during the first weeks of pregnancy and certain birth defects.

DO NOT BOIL THE WATER. Boiling, freezing, filtering, or letting water stand does not reduce nitrate. Boiling will increase the nitrate hazard.

USE BOTTLED WATER or water from another source KNOWN TO BE SAFE.

What are the concerns for drinking water with nitrate concentrations above the standard?

Persons older than six months and anyone who is not or may not become pregnant can drink this water occasionally without harm. Nitrate is found in many natural and processed foods. However, nitrate is an acute hazard for infants because they don't digest nitrate like adults, causing a lack of oxygen in their blood.

People of all ages are urged to avoid long-term consumption of high nitrate water because it is linked to some chronic diseases, according to Wisconsin Department of Health Services.

Nitrate in well water comes from groundwater contaminated by fertilizer, manure, seepage from septic systems, or stormwater run-off.

What is being done to correct the problem?

During the last week of April of 2025 the City of Tomah identified that the nitrate concentration for Well 14 had exceeded 9.0mg/L, but was still below the limit of 10mg/L. City of Tomah Water Division coordinated with the City Engineer, Town and Country Engineering, and the Wisconsin Department of Natural Resources to monitor the well and prepare to take action should the well exceed the threshold. On 13 May 2025 Well 14 tested at 14.4mg/L. The City of Tomah Water immediately notified the Interim Director of Public Works and Utilities (Town and Country Engineering) and the DNR. State policy requires a second, or “confirmation,” test is conducted whenever a sample exceeds the 10mg/L threshold, and the average of the two samples determines whether or not a well needs to be shut down and public notification conducted.

However, the City of Tomah took immediate and proactive action by shutting down Well 14 on 13 May 2025 prior to the confirmation test. It should be noted that the City of Tomah’s water system is such that Well 14 alone does not service any part of the City. Rather, Wells 10 and 14 work in conjunction to service the water tower on the northside of the City. Therefore, at no point has anyone consumed Well 14 only water. The original sample was tested at the La Crosse County laboratory, and due to the large difference between the nitrate levels in April and May the City of Tomah conducted not only a second test but also a third test. Each of these tests were conducted at different laboratories. Below are the results of those tests received on 16 May 2025:

Well #        Baraboo Lab         Davy Lab
14               6.8mg/L                 7.85mg/L

The higher of these two tests was used as the confirmation test, which resulted in an average nitrate content of 11.13 mg/L. Although this average exceeded the 10mg/L threshold, the DNR directed the City of Tomah to standby for further guidance prior to issuing public notification due to the large differences in results between laboratories. Out of an abundance of caution Well 14 remained offline. City officials were updated during each step of the process. 

On 2 June 2025 the DNR reached a final determination with respect to the way forward with Well 14 and directed the City of Tomah to issue public notification no later than 25 June 2025. It is typical for the DNR to require a municipality to issue public notification within 24 hours of a confirmation test. However, recognizing the anomalies presented by the samples, and in consideration of the fact that the City of Tomah proactively shut down Well 14, the DNR has provided the City of Tomah a longer timeline.

On 3 June 2025, within 24 hours of being directed by the DNR to issue public notification no later than 25 June 2025, public notification was provided on the water bills for 3 June 2025. Additionally, this public notice was published on the City website, Facebook page, and posted on the Public Notice Board in City Hall.

As previously stated, Well 14 was taken offline on 13 May 2025 and will remain offline until further notice. The City of Tomah is working hand-in-hand with the DNR to determine the future of Well 14. Possible corrective actions may include additional testing and monitoring if approved to return to service, constructing a replacement well, reconstructing the existing well, installing additional treatment, or installing a continual nitrate monitor. The City of Tomah will also consider developing and implementing a source water protection plan to reduce the nitrate input to the groundwater used by Well 14.

The City of Tomah thanks the Wisconsin DNR, Tomah Water Division, and Town and Country Engineering for their diligence in resolving this issue.

If you have questions regarding the safety of our drinking water, please contact:

City of Tomah Water Utility
819 Superior Ave Tomah, WI 54660
608-374-7431