No person shall discharge or cause to be discharged any stormwater, surface water, groundwater, roof run-off, sub-surface drainage, uncontaminated cooling water, or unpolluted industrial process waters to any sanitary sewer. Stormwater and all other unpolluted drainage shall be discharged to such sewers as are specifically designated as combined sewers or storm sewers, or to a natural outlet approved by the Superintendent. Industrial cooling water or unpolluted process waters may be discharged on approval of the Superintendent, to a storm sewer, combined sewer, or natural outlet.