No cooperative may sell, lease or dispose of any of its property other than property which, in the judgment of the board, is neither necessary nor useful in operating or maintaining the cooperative's system and which in any one year shall not exceed ten per centum in value of the value of all the property of the cooperative, unless authorized so to do by the votes of at least a two-thirds majority of its members; provided, however, that a cooperative:
Va. Code § 56-496