The board shall hold a public hearing in April of each year, in the regular meeting place of the board, not sooner than 30 days after receipt of the engineering investigation and report. Any operator of a water-producing facility within the district, or any person interested in the condition of the groundwater or surface water supplies of the district, may in person, or by representative, appear and submit evidence at the public hearing concerning the groundwater conditions and the surface water supplies of the district. Appearances also may be made supporting or protesting the engineering investigation and report.