In all Residence Districts, any of the following objectionable uses listed in Use Group 18, other than a use of land with minor improvements:

Coal storage;

Dumps, marine transfer stations for garbage, or slag piles;

Junk or salvage yards, including auto wrecking or similar establishments (whether or not such yard is enclosed);

Lumber yards (whether or not such yard is enclosed);

Manure, peat or topsoil storage;

Scrap metal, junk, paper or rags storage, sorting or baling (whether or not the yard in which such use is conducted is enclosed);

that:

(a)        involves activities not located within a completely enclosed building; and

(b)        involves the use of buildings or other structures or other improvements with a total assessed valuation, excluding land, of less than $20,000 as determined from the assessment rolls effective on the date established for termination;

may be continued for 10 years after December 15, 1961, or such later date that the use becomes non-conforming, provided that after the expiration of that period such non-conforming use shall terminate, and thereafter such land or building or other structure shall be used only for a conforming use.