Waterkeeper: DEQ stream protocol would fail to detect acidity
Laura Lundquist
(Missoula Current) The state of Montana has proposed a sampling protocol for pH in streams, but some water watchdogs say the method might not detect trouble until it’s too late.
A week ago, the Montana Department of Environmental Quality closed the public comment period on a protocol proposed in November for sampling pH in stream water. On Thursday, the Upper Missouri Waterkeeper and the Montana Environmental Information Center announced that they’d submitted comments criticizing the proposal for its lack of scientific rigor and public input.
“It’s no secret that Montana’s waterways and fisheries are already under extreme stress; yet instead of ensuring our monitoring can identify - and prevent - harmful conditions, DEQ is proposing weak assessment methods that fail to detect when harm is occurring,” said Guy Alsentzer, Upper Missouri Waterkeeper executive director. “Despite being the agency charged with protecting water quality, DEQ’s proposal does the opposite - undermining Montanans’ constitutional rights and pushing our rivers further toward their tipping point.”
A stream’s pH level indicates whether the water is acidic - a pH less than 7 - or basic - a pH between 7 and 14. If the pH of a stream gets too far away from the neutral value of 7, aquatic life starts to suffer. The Environmental Protection Agency has determined that water that is too acidic or basic can affect cell membrane processes, gill function and cause other physiological problems in aquatic organisms. Changes in pH can also increase the toxicity of various compounds and limit the biological availability of important nutrients.
Certain natural processes cause the pH of a lake or stream to fluctuate on a daily and seasonal basis. Due to photosynthesis, aquatic plants release oxygen into the water during the day and carbon dioxide at night when the process reverses. Carbon combines with water to create a weak acid, which lowers the pH. So, in a lake or stream, the water is the most acidic and pH is lowest at the end of the night, while the pH is highest at the end of the day. But if the stream is healthy, the fluctuations aren’t very big.
However, in streams with large algae growths often caused by high amounts of nutrients, all that plant material releases more carbon dioxide, causing the water to become more acidic by dawn. Similarly, in regions with abandoned mines, rainstorms can cause acid-mine drainage to enter streams, leading to spikes in acidity.
For these reasons, the Upper Missouri Waterkeeper and the Montana Environmental Information Center say the best-available science supports a protocol that uses continuous sampling over a number of days so the daily swings in pH can be measured. In addition, such sampling should occur during the growing season when algae and other aquatic plants cause greater daily changes in pH. Finally, in regions with abandoned mines, DEQ should sample following any large precipitation event to see if acid-mine drainage has caused the pH in the streams to drop.
However, that’s not what the DEQ is proposing. The proposed assessment describes four sampling methods, only one of which is continuous but it doesn’t have to be conducted during the growing season. The other three allow technicians to take discrete samples of water at times that may or may not identify the pH maximums and minimums. One method would take one sample a day for five days outside the growing season. Another would take two samples a day for five days, one at dawn and one at dusk, during the growing season.
At the request of the Upper Missouri Waterkeeper, aquatic scientist JoAnn Burkholder of North Carolina State University assessed the DEQ’s proposed methods and found them wanting, particularly the five-sample method.
“So few measurements, taken outside the growing season, cannot reliably detect impairment. The approach can be expected to substantially underestimate impairment or miss it entirely,” Burkholder wrote in her comment. “The draft pH assessment will further weaken protection of Montana’s streams and rivers from nutrient pollution. The poor sampling designs and unacceptable data requirements will cause harmful pH conditions to be easily missed. As the direct result, these economically and ecologically important waters will not be assessed as nutrient-impaired until they have already sustained major degradation from nutrient pollution.”
In 2014, Montana DEQ adopted a numerical water quality standard for nutrients, which are compounds containing nitrogen and phosphorus, which encourage plant growth. Too many nutrients in the water lead to extensive plant growth and algae blooms, which degrade water quality. But the agriculture and mining industries and cities and towns pushed back, demanding a narrative standard, which is less exact and allows more nutrient pollution before action is needed. After first rejecting a narrative standard, the U.S. Environmental Protection Agency approved Montana’s request for a narrative standard in October 2025.
Burkholder also said the DEQ needed to identify regions where acid-mine drainage exists so headwater streams in those areas can get special pH sampling. Such areas include the Great Falls-Lewistown Coal Field, which “contains over 400 abandoned underground coal mines, many of which are discharging acidic water with serious environmental consequences.” Rainstorms and spring runoff can release pulses of acidic water that can cause stream pH to plummet. Although short-lived, the sudden increase in acidity can “cause major adverse impacts on beneficial aquatic life.”
The Upper Missouri Waterkeeper and the Montana Environmental Information Center say that DEQ should have gone through a formal rulemaking process before publishing its proposed protocol. “Because the proposed methods affect how water quality standards are applied, including whether assessed waters are listed as impaired, the changes legally qualify as new or revised water quality standards, which must go through public rulemaking and federal review under the Clean Water Act,” the Upper Missouri Waterkeeper said.
When asked about the rulemaking process, DEQ spokeswoman Madison McGeffers responded in an email saying individual assessment methods “are not rules and therefore do not go through the formal rulemaking process. Assessment methods provide guidance for DEQ’s implementation of a water quality standard, establishing minimum data requirements and other data analysis specifications used to inform decisions.”
McGeffers added that the finalized documents - including an appendix with the public comments, DEQ’s responses, and a summary of changes - will likely be submitted to the EPA for approval this spring.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.