D.C. Code § 2-203.01

On all contracts made by the District of Columbia for construction work there shall be withheld, until completion and acceptance of the work, a retent of 10 per centum of the total amount of any payments made thereunder as a guaranty fund that the terms of such contracts shall be strictly and faithfully performed: Provided, however, that whenever 50 per centum of the work required under a contract for construction work has been completed and payments therefor have been made, the Mayor of the District of Columbia, in his sole discretion, may authorize subsequent payments to be made to the contractor without withholding from such subsequent payments 10 per centum thereof as required by this section, or the said Mayor may authorize retention from such subsequent payments of less than 10 per centum thereof, and whenever the work is substantially complete, the Mayor, if he considers the amount retained to be in excess of the amount adequate for the protection of the District of Columbia, at his discretion may release to the contractor all or a portion of such excess amount; and the said Mayor in his sole discretion, may further authorize payment in full, including retained percentages, for each separate building or public work on which the price is stated separately in the contract upon completion and acceptance of such building or work.