Pollution in Lower Yakima Valley wells is worsening, according to a new paper that examines multiple studies over the last 25 years.
Federal, state and local agencies have known about elevated nitrates in the Lower Yakima Valley for years. Many studies have found nitrates, or chemicals found in items like fertilizer and agricultural runoff, in groundwater and private wells.
At high levels, nitrates in drinking water can be most harmful for infants and during pregnancies. According to the Washington State Department of Health, excessive nitrates make it difficult for red blood cells to deliver oxygen throughout the body.
Now, the advocacy group Friends of Toppenish Creek has compiled decades of studies. Ron Sell is a retired chemist and helped with one of the first studies of drinking water in the Lower Valley. Sell said this synthesis shows the nitrate problem is getting worse.
“ It's not only impacting the rural folks, but it's also going to impact the city folks,” he said.
A spokesperson for the state Department of Ecology said there’s not enough data yet to see a trend, for better or for worse, in nitrates. Monitoring typically requires eight to 10 samples from the same location at the same time of year, said Emily Tasaka, spokesperson for Ecology’s central region.
“This problem took decades to create and will likely need many years to fully address. Nitrate moves through the environment really easily and comes from a variety of sources, which is why we are working on long-term, holistic solutions to address multiple components of the issue,” Tasaka wrote in an email.
The department plans to continue monitoring so that it can collect enough data, she said. So far, the department has sampled and tested 170 wells throughout the lower valley. Samples were taken quarterly from 2021-2023. Starting in 2024, samples are taken annually.
Many of the studies have focused on the region in Yakima County known as the Groundwater Management Area. However, Sell said more study needs to be done in lesser-studied parts of the valley.
“ The public is unaware of how bad the water has gotten,” he said. “It's a big problem and somebody needs to look into why, how to solve it and how to find a solution. We just can't continue along with voluntary compliance. It hasn't worked for 20 years.”
Yakima Valley drinking water
Around 36% of people living in Yakima County get their water from private or shared domestic wells that draw from groundwater.
State and federal standards say nitrates in drinking water should be under 10 milligrams per liter. Sell said many private wells in his analysis of earlier studies are much higher than that.
In 2002, studies found the Lower Yakima Valley aquifer had areas of nitrate contamination above those standards.
In 2013, the U.S. Environmental Protection Agency found elevated nitrates in monitoring wells near three large dairies, known as concentrated animal feeding operations, or CAFOs. The report pointed to those dairies as a likely source of contamination. The dairies fought the findings, noting that nitrate pollution could come from irrigated crops and leaking septic systems.
Years of court petitions and orders followed.
In 2024, a judge ordered three large dairies to provide well testing and bottled water or treatment systems to people living nearby.
However, Sell said those are just Band-Aids, instead of fixes for the nitrate problem. Sell said he’s helped install and test reverse osmosis systems in people’s houses. He said the systems are expensive and require more maintenance than people expect.
“ These devices do not have alarms, so they don't know when they're not working anymore. And they often fail, we found,” he said. “What this has done, in a sense, is that this quick fix has prevented people from really studying where this pollution is coming from, and it's allowed it to get worse.”
The state Department of Ecology, along with other state, federal and local agencies, has published a new nitrate reduction plan. It includes ideas to reduce nitrate contamination from various sources, including irrigated agriculture, large dairies, septic tanks and lawn fertilizer.
“Since we already have extensive monitoring data, this plan identifies what each agency will do and outlines strategies for protecting drinking water, reducing nitrate pollution from different sources, and analyzing other data,” Tasaka wrote in an email.
The department is asking for public comments on the new plan until Jan. 31, 2027.
