D.C. Code § 43-116

It shall be the duty of the owner or owners of any cemetery or cemeteries in the District to divide the area to be used for graves into lots of reasonable size, to be permanently designated by conspicuous marks, so that the position of each may be readily determined, each lot to be duly numbered. A plat of such cemetery showing the area so divided, the division into lots, and the number of each such lot shall be filed in the Office of the Surveyor of said District; the grave spaces hereafter laid out for the burial of persons above 10 years of age to be at least 8 feet by 3 feet, and those for the burial of children under 10 years of age at least 6 feet by 2 feet, or, if preferred by said owner or owners, one-half the measurement of the adult grave space, namely, 4 feet by 3 feet. No coffin shall be buried in said District so that any part thereof is within less than 4 feet of the ordinary level of the ground, unless it contains the body of a child under 12 years of age, when it shall not be less than 3 feet below that level.