D.C. Code § 6-503: Design of water and sanitary sewage systems; location of on-site waste disposal systems.

The Mayor shall require new or replacement water systems and sanitary sewage systems to be designed to minimize or eliminate infiltration of flood waters into the systems and discharges from the systems into flood waters, and require on-site waste disposal systems to be located so as to avoid impairment of them or contamination from them during flooding.