A proposed Huntington Beach seawater desalination plant passed a major regulatory hurdle Thursday when a marathon session at City Hall concluded with an endorsement from the California State Lands Commission. After more than four hours of public comment, the three-member panel unanimously approved amendments to a 2010 environmental impact report on Poseidon Water’s $1-billion project. The additions, recommended by commission staff, are expected to make the proposed plant at Pacific Coast Highway and Newland Street less harmful to ocean life and ensure its compliance with the California Ocean Plan, passed in 2015.