D.C. Code § 9-1209.02
The Mayor of the District of Columbia, or his duly designated representatives, are authorized to employ temporarily such laborers, skilled laborers, drivers, hostlers, and mechanics as may be required exclusively in connection with sewer, water, street, and road work, and street cleaning, or the construction and repair of buildings and bridges, furniture and equipment, and any general or special engineering or construction or repair work, at per diem rates of pay to be fixed and adjusted from time to time by a wage board and approved by the Council of the District of Columbia, and to incur all necessary engineering and other expenses, exclusive of personal services, incidental to carrying on such work and necessary for the proper execution thereof, said laborers, skilled laborers, drivers, hostlers, and mechanics to be employed to perform such work as may not be required by law to be done under contract, and to pay for such services and expenses from the appropriations under which such services are rendered and expenses incurred.
D.C. Code § 9-1209.02