State environmental officials say excessive levels of E. coli, ammonia and chloride recorded in water samples from the Belle Fourche River watershed in Wyoming shouldn't cause alarm in South Dakota.
Still, the pollutants detected are typical of the the kind of water-quality issues that both Wyoming and South Dakota face in prairie rivers that catch runoff from cities, towns and agricultural lands, said Rich Hanson and Pete Jahraus of the state Department of Environment and Natural Resources in Pierre.
The Wyoming Department of Environmental Quality recently released results of testing done on the Belle Fourche River in two spots near Keyhole Reservoir and two of the river's tributary streams, Donkey Creek and Stonepile Creek, about 50 miles from where the river reaches South Dakota.
Scientists in Wyoming say the creeks flow through Gillette and likely collect urban pollutants there, while the river is more likely to receive agricultural pollutants.
The chloride in the samples is believed to have come from de-icing chemicals used on Gillette streets. Amonia likely came from the Moorcroft wastewater lagoon, they said. The E. coli could have come from dog and cat waste in the urban areas and livestock waste in the rural stretches.
Hanson said tests on the Belle Fourche River from the Wyoming line to where it meets the Redwater River at Belle Fourche haven't shown problems with ammonia or chloride.
That stretch has its own issues typical to prairie streams, however, with elevated levels of suspended solids (essentially sediment), fecal coliform and E. coli, with probable sources similar to those in Wyoming.
DENR and local officials have been working on potential solutions for the pollutants. They include grazing management, restoring stream-side vegetation and creating other filters to control runoff.
"They've been focused on the total suspended solids, but they're going to start addressing some of the E. coli issues in that segment of river," Jahraus said.
In Wyoming, the Department of Environmental Quality is taking comments on the pollution report that could be used to shape a response plan.
DEQ employees will explain the report and take comments from 6 p.m. to 8 p.m. Wednesday at the Campbell County Public Library in Gillette.