Gansler said Thursday that his office has filed notice that it intends to sue the company over a Pennsylvania natural gas well blowout last year that caused drilling fluids to flow into a Susquehanna tributary.
The river provides almost half of the fresh water entering the Chesapeake Bay.
Gansler said in a letter to the company that an investigation found the incident didn’t pose a threat to the state, and his office doesn’t plan further action.
The attorney general said the company has also agreed to take steps to minimize the impact of drilling on the environment.
Pennsylvania fined the company $500,000 earlier this year for the blowout and two other violations.