Mabton Community Water System 

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On July 12, 2023, the Yakima Health District (YHD) received complaints from Mabton residents about taste and odor issues with their drinking water, which was communicated to Washington State Department of Health (DOH) and Valley Water Services in Mabton. The Valley Water Services operator conducted tests for contaminants with drinking water safety standards. Test results showed that the water met required safety standards and is not hazardous to consume.

While the water is not considered hazardous at this time, involved agencies understand that water should not have an unpleasant taste or odor, and are working together to address this problem. 

Taste and Odor Issues

Hydrogen Sulfide

Hydrogen sulfide is a colorless, flammable gas that smells like rotten eggs at low concentration levels in the air. Hydrogen sulfide naturally forms in groundwater through organic matter decay and can also result from bacteria in low-oxygen environments like wells, plumbing, water softeners, and heaters, though these bacteria are not harmful.

Hydrogen sulfide in Mabton's wells has been a problem in past years. This summer it has been particularly severe and hard to manage. The DOH Office of Drinking Water (ODW) believes that this year’s problem is related to hydrogen sulfide, which does not have a safety standard.  Hydrogen sulfide is not considered hazardous at levels typically associated with drinking water. However, steps are being taken to address this problem.

Iron Bacteria
Another potential source is iron bacteria. Iron bacteria are a group of microorganisms that are commonly found in groundwater, wells, and plumbing systems. These bacteria feed off iron in the water and form brown slime coatings inside water pipes, well screens and water storage tanks. While they can give an unpleasant taste and odor to the water, they are not considered hazardous to consume. Agencies are working to investigate and address this potential source of the issue.

Health Risks
Involved agencies are currently investigating to rule out any other water contaminants that might have a health risk. Contact a health care provider if you have health concerns or are experiencing health symptoms.

How are Taste and Odor Issues Being Addressed?  

State and local agencies are working together with the City of Mabton to improve the drinking water quality. This includes short and long-term actions. 


The City of Mabton completed city wide flushing of the water distribution system. This process involves flushing water through the city's pipes at high speeds in one direction to effectively clean the pipes. This helps eliminate the taste and odor issues in the older water and also removes chemicals that can stick to the inside wall and may cause the water to appear dirty or discolored. If your household continues to experience taste and odor issues, report this to the City.  Your help in identifying where they are having issues will help improve their flushing program and identify areas that may need more attention.

Monitoring Plan and Well Sampling

On November 8th, a consultant hired by the Department of Ecology used a proposed monitoring plan from the Department of Health, to collect water quality samples from the city’s wells and distribution system.  They checked for specific substances, such as hyrdogen sulfide, that might cause taste, odor, and discoloration issues in the water. The monitoring plan will also help assess how well treatments are working. Sampling results will be posted once available.

New Wells

A new well, named Well #8, has been completed. At this time, the well does not produce enough water and initial nitrate results are higher than 10.0 mg/L, which is the Maximum Contaminant Level (MCL) for nitrate. The City's consultants will determine the steps needed to move the next new well, named Well #7, farther away from Well #8 . The consultants may provide more recommendations once the well sampling results are available. 

Involved Agencies

WADOH logo
DOH is the lead agency that has authority over the Mabton Community Water System. DOH is currently monitoring the water for any health risks and is working closely with the water system operator to improve taste and odor issues.

Ecology’s water quality program works to ensure clean water is available to communities and the natural environment. The program works with municipal, industrial and agricultural entities to help them manage operations in a way that is protective of Washington State water quality standards.

YHD_High Resolution Logo
YHD is partnering with involved agencies to share information on the Mabton Community Water System and provide education to community members.