D.C. Code § 9-421.09
The assessments provided for in §§æ9-421.01 to 9-421.12 shall be made and collected as provided in § 9-401.06, relating to alleys and sidewalks. The rate of interest to be charged upon any assessment, levied under § 9-401.06 relating to alleys and sidewalks, or any instalment thereof, is reduced hereby from 8 per centum per annum to 6 per centum per annum; provided, however, that any instalment of any such assessment not paid within the time provided in § 9-401.06 shall thereafter bear interest at the rate of 12 per centum per annum; and provided further, that the advertisement by publication of the intention of the Mayor of the District of Columbia to perform the work and the formal hearing in respect thereto required by law as to alley and sidewalk improvements shall not be required as to roadway, curbing, and gutter improvements.
D.C. Code § 9-421.09