In the event of sudden or unexpected damage, injury or impairment of such plant, works, system, or other property belonging to the district, or an order of a regulatory body which would prevent compliance with section 70-637, the board of directors may, in its discretion, declare an emergency, and proceed with the necessary construction, reconstruction, remodeling, building, alteration, maintenance, repair, extension, or improvement without first complying with the provisions of sections 70-637 to 70-641.