11-2-50. Board of adjustment--Composition--Vacancies--Alternates. A board of adjustment, other than the planning and zoning commission acting as a board of adjustment, consists of five members, each to be appointed for a term of three years and removable for cause by the appointing authority upon written charges and after public hearing. Vacancies shall be filed for the unexpired term of any member whose term becomes vacant. The appointing authority may also appoint a first alternate and a second alternate for a term of three years each. If a member is unable to attend a meeting, the first alternate, or second alternate, in turn, shall serve in the member's place.