Applies to specialist contractors engaged in general excavation including ditch digging, burrowing, filling or backfilling provided such operations are not otherwise classified. Includes excavation in connection with building foundations, swimming pools, landscape gardening and waterproofing operations. Also contemplates specialist contractors engaged in grading land and landfilling, provided such operations are not otherwise classified. Includes grading involved in airport construction, grading of land preparatory to construction or planting, grading of parking lots, etc. Does not include grading in connection with street or road construction, dam or lock construction, pile driving, shaft sinking and caisson or cofferdam work. Includes specialist contractors engaged in tree removal operations on developed sites using mechanical equipment. This does not include trees removed in order to clear a right of way. Applies to specialist contractors engaged on the blasting or removal of mass rock of any type. Refer to code 6204 when holes are drilled by a specialist drill contractor.