The grading plans and specifications shall specify and delineate the use and extent of fills in accordance with the following classifications: Class 1 fill — Load-bearing fills proposed for support of buildings, walls, and other structures, the function thereof which would be especially impaired by settlement. Class 2 fill — Load-bearing fills proposed for support of roadways, pavements, rigid utility lines, house connections, and structures which would not be especially impaired by moderate settlement. Class 3 fill — Common fills proposed for lawns, landscape plantings, or for other nonload-bearing usage.