70 ILCS 1545/19

If any surface or subsurface utilities serve parks and boulevards and it is either impossible or impractical to separate the maintenance and operation of such utilities between parks and boulevards, the park district and the city may by agreement provide that either the park district or the city may maintain and operate such utilities upon such terms, conditions and compensations as shall be reasonable. If the city and park district cannot reach agreement, and the city elects to receive such services, the park district shall maintain and operate such utilities and the city shall pay the park district the reasonable value of the services rendered.