The Truth About a Stormwater Designation in Gallatin County

In the summer of 2021, Upper Missouri Waterkeeper submitted a petition to the Montana Dept. of Environmental Quality (DEQ) requesting the designation of Gallatin County as a municipal separate stormwater system (MS4) entity to better control stormwater pollution in the fastest growing county in the state. In December, 2021, DEQ denied the petition to designate Gallatin County as a MS4 permittee, and in response, Waterkeeper filed a complaint challenging DEQ’s determination. Read the latest from Bozeman Daily Chronicle here.

A MS4 designation would provide Gallatin County with a proven path for managing the adverse water quality impacts caused by sprawl development outside of city limits. It’s a win-win for both population growth and water quality.

To clear the water on what a stormwater designation would really mean for Gallatin County, below are some claims, rebuttals, questions, and answers about an MS4 designation, our petition to DEQ, and stormwater pollution.

Claim #1:  Gallatin Co is predominantly rural, and adjacent to public lands, and therefore cannot be a stormwater authority.

Rebuttal:  The petition seeks the designation of Gallatin County as an MS4 permittee to address undisputed water quality degradation related to development in high-growth, urban and ex-urban areas, not public lands or farm fields.  It’s misleading and simply untrue to suggest stormwater control in Gallatin County would be anything other than focused on developed and developing areas.  

Because high-growth zones occur throughout the County, some within municipal boundaries and others not (e.g. Four Corners, Big Sky), the County is ideally positioned to lead on a thoughtful regional effort aimed at better protecting local water quality from sprawl development. 

DEQ also argues that a county-wide designation would inappropriately focus on rural areas.  This is also untrue, and existing examples of county-wide designations tell a different story.  Three of Montana’s most developed counties – Cascade Co around Great Falls, Missoula Co around Missoula, and Yellowstone Co around Billings – have been MS4 authorities for almost 20 years, and each of these counties also have wide swaths of agricultural and public lands.  Not designating Gallatin County as a stormwater management authority on the basis of diverse landscapes ignores legal standards and the actual petition request from Waterkeeper.

Claim #2:  The petition didn’t satisfy legal requirements or provide sufficient data quality control.

Rebuttal:  DEQ is just plain wrong.  The legal and scientific bar for designating a new stormwater management authority is purposefully low, just as intended by the federal Clean Water Act and the Montana Water Quality Act.  Federal law has specifically intended the designation of high-growth areas as new stormwater authorities, and DEQ’s own rules reflect that proactive intent in getting ahead of the curve to best protect local water quality.

All that’s required to designate a new MS4 authority is evidence that (a) population is >10,000, and (b) stormwater runoff from developed areas is resulting in, or has the potential to result in, degradation of local water quality.  Waterkeeper’s petition provided expert scientific and economic data proving that both population requirements and water quality impacts are met in Gallatin Co, and therefore the county must become a permittee and start developing a thoughtful program for better controlling stormwater pollution from urban and sprawl development.

Claim #3:  The petition didn’t request or include details to determine which parts of the county may meet designation criteria.

Rebuttal:  Designation rules don’t require a petition to show the precise path for how a new stormwater authority designation would unfold; the law simply mandates that if sufficient density is present, and there’s evidence of likely water quality degradation from density and development, then a new MS4 designation is appropriate.

In arguing that Waterkeeper has to provide explicit detail on how a stormwater designation would unfold DEQ is placing senseless, and unlawful, burdens on Waterkeeper, when those implementation decisions are properly its duty.  While Waterkeeper supports flexibility for Gallatin Co’s stormwater designation to ensure it can look at facts on the ground and use its own expertise and sound science to develop a targeted stormwater program, this work isn’t Waterkeeper’s obligation, and neither does the law require Waterkeeper to explain how implementation would play out in a designation petition.

Q:  Why does stormwater control matter?

A:  When it rains or snows, runoff from roads, commercial and industrial spaces, and suburbs frequently washes harmful pollutants into nearby rivers, streams, and lakes because their surfaces are impervious, meaning that water cannot pass through them. Rain that falls on impervious surfaces is not able to soak into the ground as it would naturally. 

In fact, only 10 to 20 percent of rainwater runs off the land in its natural state, while the runoff from impervious surfaces approaches 100 percent. It does not take much impervious surface to create massive quantities of polluted runoff: one inch of rain that falls on one mile of a narrow two-lane road produces 55,000 gallons of stormwater.

That runoff makes its way into local water bodies, untreated, carrying with it any substances that may be present on the road’s surface. Well-established science shows that stormwater runoff from populated areas carries harmful pollutants that degrade local water quality, destroy aquatic habitat, and slowly but surely poison our favorite local creeks and streams.

Q:  Aren’t stormwater rules just a rain tax?

A: Opponents of stormwater fees sometimes call them a “rain tax,” but that term is a misnomer: no one is taxed or charged a fee because it is raining or snowing. During wet-weather events, impervious areas on developed land generate polluted runoff, and local governments need to spend money to clean it up.

A property owner pays a water bill that covers municipal costs to provide potable water, including the costs of building out and maintaining underground infrastructure. Similarly, private property owners must also contribute to the cost of managing the pollution and flood risk created by the impervious areas they own.