Except where otherwise required by state statute or ordinance,
the Board of Selectmen may appoint one or more, but not more than
three alternates to a commission, each such alternate to serve a term
of five years commencing on the first Monday of January of the year
following the appointment of such alternate; provided, however, that
no two or more alternates shall have coincident terms. Any vacancy
on the Commission shall be filled by the Board of Selectmen for the
unexpired portion of the term. Any such alternate member shall, when
seated, have all the powers and duties of a member of the Commission.