(1) A tier one member is eligible to receive a service retirement allowance calculated under 19-20-804 (1) if the member:
(a) has been credited with at least 5 full years of creditable service and has attained the age of 60; or
(b) has been credited with full-time or part-time creditable service in 25 or more years.
(2) Except as provided in subsection (3), a tier two member is eligible to receive a service retirement allowance calculated under 19-20-804 (1) if the member:
(a) has been credited with at least 5 full years of creditable service and has attained the age of 60; or
(b) has been credited with full-time or part-time creditable service in 30 or more years and has attained the age of 55.
(3) A tier two member who has been credited with 30 or more years of creditable service and has attained the age of 60 is eligible for a professional retirement option allowance calculated under 19-20-804 (2).
(4) To receive a retirement allowance under 19-20-804, the member must have terminated employment in all positions reportable to the retirement system and must file a written application with the retirement board.
(5) A vested member who has attained normal retirement age has a nonforfeitable right to the benefits accrued and payable under the provisions of this chapter, subject to the member's right to a refund of the member's accumulated contributions under 19-20-603.