The Sierra Club says it plans to sue railroad and coal companies in 60 days for spilled coal in the Northwest, and sent out letters of intent to the parties. The environmental group has been testing land and water around railroad tracks, and claims to have found pieces of coal and coal dust that, they say, blows off the train cars from mines in Wyoming and Montana.
The oil and gas industry is trying to ease environmental concerns by developing nontoxic fluids for hydraulic fracturing.
But it's not clear whether the fluids will be widely embraced by drilling companies.
Fracking has made it possible to tap into energy reserves across the nation but also has raised concerns about pollution, since large volumes of water along with sand and hazardous chemicals are injected underground to free the oil and gas from rock.