(a) If authorized by their legislative or other governing bodies, two or more public agencies which have the authority to identify, plan for, monitor, control, regulate, dispose of, or abate liquid, toxic, or hazardous wastes or hazardous materials may, by agreement, jointly exercise any of these powers common to the contracting parties.
(b) The contracting parties may provide special services, including persons specially trained, experienced, expert, and competent to perform these special services.
(c) The provisions of this section are declaratory of existing law and do not limit any authority which already exists.