D.C. Code § 34-1117
Nothing in this subtitle shall be taken to prohibit a public utility, with the consent of the Commission, from providing a sliding scale of rates and dividends according to what is commonly known as the Boston sliding scale, or other financial device that may be practicable and advantageous to the parties interested. No such arrangement or device shall be lawful until it shall be found by the Commission, after investigation, to be reasonable and just and not inconsistent with the purposes of this subtitle. Such arrangement shall be under the supervision and regulation of the Commission. The Commission shall ascertain, determine, and order such rates, charges, and regulations, and the duration thereof, as may be necessary to give effect to such arrangement, but the right and power to make such other and further changes in rates, charges, and regulations as the Commission may ascertain and determine to be necessary and reasonable, and the right to alter or amend all orders relative thereto, is reserved and vested in the Commission notwithstanding any such arrangement and mutual agreement.
D.C. Code § 34-1117
Investigations of public utilities, assessing expenses, see § 34-912. Public Service Commission, creation, powers and duties, see § 34-802. Rate change procedures, appeal and review, see § 34-901. Rates and charges, Commission's power to regulate, see § 34-709. .