Lawsuit threatened over ballast rule

TRAVERSE CITY, Mich. (AP) - Environmental groups say they may renew a legal battle if the federal government doesn't toughen proposed regulations of ship ballast water that has brought invasive species such as zebra mussels to the Great Lakes.

Groups have gone to court twice to force the U.S. Environmental Protection Agency to crack down on ballast water disposal. The agency now requires ships to exchange the water at sea. In November, EPA proposed requiring vessels to install equipment that would kill at least some organisms remaining in the tanks.

The rule is based on an international standard that shippers say is the best they can do with existing technology.

But environmental groups said Tuesday the rules aren't strong enough to prevent more species invasions and they may sue again unless EPA toughens them.