Developers of a major offshore wind farm in Massachusetts Bay failed to reach agreement by March 1 with local Native American tribes who say the $1-billion Cape Wind project would destroy ancestral burial sites. The continuing impasse over the 135-turbine project means U.S. Interior Secretary Kenneth Salazar will make a final ruling on its fate by the end of April. Salazar had acted as arbiter between the tribes and project developer Cape Wind Associates, with a self-imposed March 1 deadline. The lengthy permitting process now goes to a Dept. of the Interior agency, the Advisory Council on Historic Preservation, for a 45-day review period. The council will determine whether or not the site is appropriate to build on, but its decision would not be binding, say Interior officials. Salazar has said previously that moving the project to a new site would not be a realistic alternative.