(a) The board of trustees shall administer the retirement fund and shall maintain records as follows:

(1) The board of trustees shall maintain individual accounts for each participating employee, to which shall be credited the dollar value of participation allocated to such employee under the respective member employer's retirement plan, and such other accounts, if any, as may be reasonably required, in the discretion of the board of trustees, for the convenient administration of the plan;

(2) There shall be credited to the contribution account of each member employer all contributions received by the board of trustees from it or its participating employees and there shall be charged against such account all payments made from it pursuant to the terms of the retirement plan, together with any other payment or expenses chargeable against that account;

(3) The interest of each member employer in any retirement fund established under the system shall be represented by units which shall constitute equal interest in any such fund; and

(4) The board of trustees may from time to time establish new or additional retirement funds and may separate and place new contributions in such funds instead of adding to existing funds, provided that member employers continue to be represented by units which constitute equal interests in such funds.

(b) The board of trustees may establish a workers' compensation fund, employee benefit fund, and other funds necessary or incident to the provision of workers' compensation benefits and employee benefits under this chapter.

(c) The retirement fund shall not be commingled with the workers' compensation fund, employee benefit fund, or other funds.