In C-O districts the aggregate ground coverage, calculated as provided in Section 17.52.380, shall not exceed fifty (50) percent of the area of the lot. All open portions shall be graded, drained and maintained continuously in a dust free condition, either by landscaping or by paving, to standards approved by the board of zoning adjustments. (Ord. 2002-60 (part): Prior gen. code § 8-46.6)