A nonconforming soil mining operation may expand by mining within the boundaries of the original parcel on which the mine was legally permitted only to the extent allowed by an existing Department of Environmental Conservation (DEC) permit or as otherwise provided by the laws of New York State. A soil mining operation commenced in violation of the Dover Zoning Law after September 1, 1991, shall be permitted to continue mining under a valid DEC permit but shall not be permitted to expand or otherwise benefit from the legal protections afforded under state law for a nonconforming use that was commenced in full compliance with applicable local laws and regulations. Such an operation may not process materials mined off site by crushing, screening, sorting, washing, drying, or otherwise. This shall not prevent the continuation of any nonconforming industrial use of a property where soil mining products mined off site are used as a raw material.