Three years into a legislatively mandated effort to adopt looser standards for two nutrients abundant in Montana waterways, the state has halted rulemaking on the contentious effort.

Environmentalists described DEQ’s proposed rules as unscientific and unprotective, while sewer operators and industrial dischargers deemed them difficult to understand and financially and technologically unattainable.

The nutrient standard revision was a product of Senate Bill 358, which sought to make compliance with the water quality standards the state adopted in 2014 more attainable and affordable for wastewater treatment plants and industrial operators such as refineries and mines.

SB 358 directed DEQ to do away with the “base numeric nutrient standards” — numbers that set objective limits for nitrogen and phosphorus, which impair one-third of Montana’s river miles. In its place, the Legislature ordered the agency to adopt subjective rules for nutrients such as the prohibition of introducing nutrients that would “create conditions that are toxic or harmful to human, animal, plant and aquatic life” or “create conditions that produce undesirable aquatic life.”

MTFP: DEQ halts rewrite of water quality standards