(a) Ordinary Disability Retirement Authorized. Any member who has completed the service requirement for such member's classification as set forth in subsection (b) and suffers from a total and permanent disability may be retired by the board of trustees on an ordinary disability retirement allowance. Before approval may be granted, the member must file with the retirement division an application for the retirement allowance in the manner prescribed by the retirement division. In addition, the member must provide competent medical evidence conclusively documenting that the member is totally and permanently disabled from engaging in any type of substantial gainful activity and that such disability existed at and since the date of the member's separation from service.

(b) Creditable Service Required. The number of years of creditable service which a member shall have completed to be eligible for ordinary disability retirement shall be:

(1) Five (5) years for a member in Group 1 or 2; and

(2) Eight (8) years for a member in Group 3 or 4.

(c) Amount of Allowance.

(1) Upon ordinary disability retirement, a member shall receive a service retirement allowance as provided in §§ 8-36-201 — 8-36-205, if eligible therefor. Otherwise, the member shall receive an ordinary disability retirement allowance until the member's attainment of service retirement age as provided in §§ 8-36-201 — 8-36-205. The ordinary disability retirement allowance shall be equal to nine tenths (⁄) of a service retirement allowance as computed in accordance with §§ 8-36-206, 8-36-207 on the basis of the member's average final compensation and creditable service at the time of ordinary disability retirement.

(2) Notwithstanding the foregoing, if the member has completed less than twenty (20) years of creditable service at the time of ordinary disability retirement, the number of years of creditable service used in calculating the ordinary disability retirement allowance under subdivision (c)(1) shall be increased to the number of years of creditable service the member would have had at the member's service retirement date had the member remained in service to such date, but not greater than twenty (20) years. This subdivision (c)(2) does not apply to members joining the retirement system after October 15, 1992. Any member joining the retirement system on or before October 14, 1992, shall receive the greater of the disability retirement allowance computed with or without the provisions of this subdivision (c)(2).

(3) Notwithstanding subdivision (c)(1) or (c)(2), if the member has completed less than twenty (20) years of creditable service at the time of ordinary disability retirement, the number of years of creditable service used in calculating the ordinary disability retirement allowance under subdivision (c)(1) shall be increased to the greater of ten (10) years or to the number of years of creditable service the member would have had at the member's service retirement date had the member remained in service to such date, but not greater than twenty (20) years.

(4) The maximum ordinary disability retirement allowance payable under this section shall not exceed seventy-five percent (75%) of the member's average final compensation. This section shall not be construed to prevent any increase in the ordinary disability retirement allowance of a member in excess of the seventy-five percent (75%) limit when such increase is in accordance with § 8-36-124 or § 8-36-701.

(5) Except as may be reduced under subdivision (c)(7), the minimum ordinary disability retirement allowance payable under this section shall be the minimum service retirement allowance computed in accordance with § 8-36-209 on the basis of the member's creditable service at the time of ordinary disability retirement.

(6) Upon the member's attainment of service retirement age as provided in §§ 8-36-201 — 8-36-205, the ordinary disability retirement allowance shall become equal to the full service retirement allowance as computed in accordance with §§ 8-36-206 — 8-36-209.

(7) Notwithstanding anything to the contrary, in all cases where a member, including a prior class member, is receiving payments from the division of claims and risk management or workers' compensation, the disability retirement allowance payable under this section shall be reduced so that the disability retirement allowance, together with payments from the division of claims and risk management and workers' compensation, does not exceed seventy-five percent (75%) of the member's average final compensation; provided, that if the member is receiving the minimum ordinary disability retirement allowance computed in accordance with § 8-36-209, such allowance shall be reduced so that the member's disability retirement allowance, together with payments from workers' compensation and the division of claims and risk management, does not exceed one hundred percent (100%) of the member's average final compensation. This section shall not be construed to prevent any increase in the ordinary disability retirement allowance of a member in excess of the seventy-five percent (75%) or the one hundred percent (100%) limit when such increase is in accordance with § 8-36-124 or § 8-36-701. Any lump sum payment made by the division of claims and risk management or workers' compensation shall be prorated over the period of time the payments would have been made had the payments not been commuted to a lump sum.