Va. Code § 21-285
Any commission, and any county, city or town in whole or in part outside of the district, is authorized to enter into a contract or contracts on such terms and conditions as such contract may contain, providing for or relating to the treatment and disposal of sewage or industrial wastes originating in such county, city or town, by means of the sewage disposal system or such other facilities as the commission may determine to provide for such purpose, and such county, city or town is authorized to do everything necessary or proper to carry out and perform every such contract and to provide for the payment or discharge of any obligation thereunder by the same means and in the same manner as any other of its obligations.
In the event any such contract is entered into in accordance with the provisions of this section, provision shall be made therein whereby the cost of rendering the services herein referred to, to such county, city or town, will be borne by such county, city or town.
Va. Code § 21-285