The Navy's plan to build a sonar range off the coast of Onslow County prompted the North Carolina Coastal Federation and Environmental groups to hold a forum in Carteret County Monday. The navy is planning a 660 square mile sonar range, about 50 miles off the coast of Camp Lejeune in Jacksonville. Groups like the Southern Environmental Law Center are among the vocal critics of the plan, warning that sonar could have serious effects on whales and other marine life. According to environmentalists, more than three dozen whales beached and died on the Outer Banks in January 2005 within hours of a U.S. Navy sonar training exercise. While the exact cause of deaths of the beached whales has not been conclusively established, environmentalists claim sonar testing and the increased boat traffic of the proposed range could have serious effects on marine life, including critically endangered species such as the Right Whale and the Loggerhead Turtle.