The Poseidon desalination plant proposed for Huntington Beach could be facing rough waters ahead, as several regulatory officials on Friday expressed concerns over the controversial plan..

During a Regional Water Quality Control Board workshop held online, three of the agency’s six board members persistently pressed local officials about the need, consumer cost and environmental harm of the $1 billion project.

The board is tentatively scheduled to a vote July 31 on one of two permits still needed by Poseidon Water before it can negotiate a final contract and begin construction on a project that that company has been pursuing for two decades. The proposal needs four votes from the regional board before it can go before the Coastal Commission for its last permit.

The Orange County Water District, the prospective purchaser of the water, has been attracted to the desalination project because it’s drought-proof and would protect its service area of 2.5 million residents from shortages of imported water. Currently, about 23% of the district’s water is imported.