On or before October 1, 1992, each county and municipality shall file a statement of intent with the department describing the way in which it intends to fulfill its responsibility for integrated solid waste management. If a municipality or county intends to enter into a cooperative relationship with another entity to fulfill such responsibility, documentation of the reciprocal intent of those entities shall be included with the statement. If no statement of intent is filed by a municipality or county, the responsibility for integrated solid waste management shall remain with the nonfiling county or municipality.