As used in this chapter, the following terms shall have the meanings indicated:
A lowering of the existing grade in excess of two feet, regardless of the area involved in such change, and/or any lowering of the existing grade over an area of 300 square feet or more.
Depositing of clean nonburning material free from garbage, refuse or deleterious matter to change the existing grade in excess of two feet, regardless of the area involved in such change, and/or the raising of the existing grade over an area of 300 square feet or more.
The removal of the overlying fertile mixture of sand, silt or clay containing organic matter to any depth for an area of 300 square feet or more.