The use of land for the storage, collection or accumulation of used lumber and other used materials, or for the dumping, disposal or salvage of automobile scrap iron, junk, garbage, rubbish or other refuse or of ashes, slag or other industrial wastes or by-products shall not be permitted in any district, except as specifically permitted in Section 17.24. The dumping of dirt, sand, rock or other material excavated from the earth is permitted in any district, provided the surface of such material is graded within a reasonable time in a manner preventing the collection of stagnant water, and which leaves the ground surface in a condition suitable for the growing of turf or for other land uses permitted in the district.