The state of Montana, spurred by a law passed this year, has begun to roll back elements of its pioneering water quality standards, even as federal regulators have questioned the science behind the changes, warned of loopholes and maintained that current metrics are in place until they confirm otherwise, documents obtained by the Daily Montanan show. 

At issue is Senate Bill 358, a bill passed in the 2021 legislative session essentially repealing a water quality regulatory structure that’s been in place for the better part of a decade. That structure provided for strict but regionally dependent numeric nutrient standards that set limits on the total levels of nitrogen and phosphorous in a body of water — both elements that are key contributors to potentially harmful algal blooms and other ailments. Nutrients such as these impair 35 percent of river miles in the state.

Municipal and commercial dischargers supported the bill as a way of creating more attainable water quality standards. Permitees were unable to meet the numeric criteria without variances, they argued; a system of narrative criteria, which was on the books in the past, would allow for more flexibility. These criteria are based on descriptors of water quality and pollution, rather than precise measurements of nutrient load.