6. a. The total annual fee collected by the department from the owner or operator of a privately-owned sanitary landfill facility to cover the costs of supervising the privately-owned sanitary landfill facility pursuant to the provisions of P.L.1970, c.40 (C.48:13A-1 et seq.) shall not exceed the annual assessment authorized under the provisions of P.L.1968, c.173 (C.48:2-59 et seq.).
b. For the purposes of the annual assessment authorized under the provisions of P.L.1968, c.173 (C.48:2-59 et seq.), the owner or operator of a privately-owned sanitary landfill facility shall file with the department not later than May 1 of each year a certification of gross operating revenues received from intrastate utility services during the preceding calendar year.