Bozeman-based Upper Missouri Waterkeeper said that a set of replacement rules suggested by the Montana Department of Environmental Quality would allow more nutrient polluting to enter streams, rivers, and other waterways throughout the state.
According to the suit filed in U.S. District Court, Great Falls on Thursday, the U.S. Environmental Protection Agency oversees the state's pollution rules. It is required to approve or deny the changes.
Farm fertilizer, industrial plants and treated sewage, among other sources, can cause nutrient pollution. It can cause damage to fish and other health issues by encouraging the growth toxic algae blooms.
Montana boasts almost 60,000 miles (97,000 km) of perennial streams and rivers. This includes major rivers like the Missouri, which drains into North Dakota, and the Clark Fork of the Columbia, which drains into Idaho.
The water quality of about a third Montana's rivers was tested for pollution. Most of the river miles were found to have been impaired or harmed by polluting, according to both federal and state agencies.
The Montana Republican-dominated Legislature repealed last year long-standing rules that imposed water pollution limits. These standards were also known as numeric standard. These limits have been replaced by "narrative standards", which describe the conditions that should exist for a waterbody to be free from pollution.
The new rules were presented in a broad framework earlier this month. More details will be released later in the year.
Officials from the state stated that the rules would protect streams and rivers that are essential to the state's tourism industry and recreation industries. They also allow for flexibility regarding how nutrients are reduced by polluters.
They rejected the idea that the rules could cause waterways to be degraded.
Richard Mylott, spokesperson for the EPA, stated that the agency has no comment regarding the litigation against it.
