Burlington Northern Santa Fe Railroad says they take many successful steps to prevent coal dust from falling from their trains; but a letter of intent to sue BNSF and multiple coal companies argues they're not doing enough to prevent pollution along the lines. Eric de Place with the Sightline Institute says more research needs to be done to fully understand the damage coal does to the eco-system.  The Sierra Club, Columbia Riverkeeper and Friends of the Columbia Gorge are among several environmental advocacy groups that have warned the coal and rail companies they have 60 days to show they're doing more to prevent pollution, or they'll sue, claiming violations of the Federal Clean Water Act.