In H-1 districts, the aggregate ground coverage, calculated as provided in Section 17.52.380, shall not exceed forty (40) percent of the area of the lot. All open portions of the lot shall be graded and drained to standards approved by the planning commission and maintained in a dust-free condition. All parking areas and driveways shall be paved to standards approved by the planning commission. (Prior gen. code § 8-45.7)