Ohio Rev. Code § 729.42: Two or more municipal corporations may construct joint sewers.

The legislative authorities of two or more municipal corporations may provide for the construction of a main sewer and branches jointly by such municipal corporations for the sewering and draining of such municipal corporations or any part thereof, and agree upon the plan and location of such main sewer, the terms on which it shall be constructed and maintained for common use, and the portion of the cost thereof to be paid by each municipal corporation. For this purpose such municipal corporations may jointly appropriate land either within or without their respective limits.