The board of engineers shall consist of five (5) persons. All five (5) persons must be professional engineers registered in Rhode Island, one of whom may also be a professional land surveyor registered in the state. Each member of the board must be a qualified elector of this state for three (3) consecutive years prior to appointment. Each member shall have been engaged in the lawful practice of engineering for at least twelve (12) years and been in responsible charge of engineering work for at least five (5) years. The professional engineer members of the state board of registration for professional engineers serving on February 1, 1991, shall complete their terms of appointment. Upon the expiration of their terms, the governor may make subsequent appointments as subsequently provided.