The Montana Dept. of Environmental Quality (DEQ) is currently accepting public comment – until Feb. 8 – on a new proposed rule attempting to limit the impact of nutrient pollution on Montana’s waterways. The rulemaking is the result of Senate Bill 358, which passed the legislature in 2021.

SB 358 sought to repeal Montana’s existing “numeric” nutrient standards, which set quantifiable limits on the amount of nutrient pollution that can be discharged to waterways, and directed DEQ to go back to using so-called “narrative” standards, which say, rather vaguely, that discharges should not create problems in our waterways.

The changes proposed by SB 358 were resisted by clean water advocates because in the past, these vague, narrative standards often failed to protect Montana’s high quality waters from nutrient pollution, leading to nuisance and toxic algae blooms, low oxygen levels and negative impacts to our fisheries.

The narrative standards also resulted in inefficient, incremental efforts to clean up degraded waterways. Wastewater engineers working for regulated dischargers would design and build a system that reduced nutrients somewhat, but turned out to be insufficient to correct the problem. So engineers would have to redesign and rebuild. Sound expensive? You bet it was.

To address this problem, engineers told water scientists that a numeric target was needed so they could design for that. Montana’s water scientists, including myself, spent decades studying nutrient levels, algae levels and other water quality measures in healthy water bodies and nutrient-impacted water bodies throughout Montana. Using this data and lab studies that related these measures to one another, the scientists developed numeric nutrient standards.

These standards were reviewed and endorsed by other scientists, accepted by the EPA, and ultimately Montana’s approach was seen as a model and adopted by other states grappling with nutrient pollution. Recently, the Montana Legislature proposed to reverse course. While the specifics of a new narrative rule have yet to be fleshed out, one thing is certain: without numeric targets, Montana will go back to allowing our high quality waters to degrade until problems are obvious, and engineers will go back to guessing what might work, and trying over and over again.

A better way would be to continue to use the scientific information we already have to develop nutrient load targets for water bodies. This approach could divide water bodies into 3 groups: 1) water bodies where nutrient targets are being met and should be maintained; 2) water bodies where targets are not being met and resulting water quality problems require a management plan to reduce loads; and 3) water bodies where nutrient targets are not being met, but do not have water quality problems connected to nutrients and can simply continue to monitor for problems.

In some water bodies, other factors limit algae growth, which explains the third group. For water bodies in the second group, additional site-specific data are needed to inform management plans so that they are as effective as possible.

Such an approach would make use of existing, relevant scientific information to prioritize which waterbodies are most susceptible to nutrient related problems, and most likely to respond to management for nutrients. It would also give engineers and land managers a meaningful target when designing systems to address an existing problem or to prevent degradation when new development occurs – as required by the Clean Water Act.

There are more technical issues being debated, but the big picture is this: Montana should not abandon decades of science-based nutrient targets developed to protect high quality waters and restore degraded waters. You can voice your views in writing or orally – this DEQ website explains how

Vicki Watson is an emeritus professor at the University of Montana, speaking for herself.