The authority shall be operated on an actuarially sound basis and become neither more nor less than self-supporting. For that purpose, loss experience and expense shall be ascertained and credits, refunds, and assessments may be made as determined appropriate by the board. The authority shall have the powers and duties set forth in this chapter and the powers and duties given it by its agreement. The original board may enter into the original joint powers agreement creating and governing the authority, which shall be made subject to subsequent modification and termination by the members of the authority.