The Environmental Quality Commission shall establish by rule criteria for Green Permits and procedures for the application, review and public participation in the process of issuance of the permits. The accepting, processing and issuing of Green Permits is a discretionary function of the commission. In establishing the criteria for Green Permits, the commission:
(1) Shall consider the objectives set forth in ORS 468.503;
(2) May establish classes or categories of Green Permits as the commission considers appropriate; and
(3) May limit the number and duration of such permits issued by the agencies for the purpose of evaluating the effectiveness of the Green Permit program.