The provisions of this article do not prohibit the present or future discharge of storm
water runoff to combined sewers, or directly to natural watercourses within the City. (1969 Code §22-18) Provided, however, that in the event the Sanitary Board shall hereafter order the separation of storm water runoff from sanitary sewage, and shall present a plan for the construction of such facilities as may make such separation possible, then, the Sanitary Board may order such separation and may thereafter prohibit the discharge of storm water runoff into the sanitary sewer so provided in that area.