Sec. 3. A fee established under this title for a type or class of permit:
(1) may be based on the average of the costs specified in section 2 of this chapter for all permits of that type or class;
(2) may be set at a particular amount in consideration of the type and amount of discharge or emission to which the permit relates; and
(3) may not be different in amount for public sector permit holders than for private sector permit holders, unless the difference is specifically authorized by the Indiana Code.