An earthwork and paving contractor digs, moves and places material forming the surface of the earth, other than water, in such a manner that a cut, fill, excavation, grade, trench, backfill or tunnel (if incidental thereto) can be executed, including the use of explosives for these purposes. This classification includes the mixing, fabricating and placing of paving and any other surfacing materials.

A pipeline contractor fabricates and installs pipelines for the conveyance of fluids, such as water, gas, or petroleum, or for the containment or protection of any other material, including the application of protective coatings or systems and the trenching, boring, shoring, backfilling, compacting, paving and surfacing necessary to complete the installation of such pipelines.

A sanitation system contractor fabricates and installs cesspools, septic tanks, storm drains, and other sewage disposal and drain structures. This classification includes the laying of cast-iron, steel, concrete, vitreous and nonvitreous pipe and any other hardware associated with these systems.

General engineering contractor is a contractor whose principal contracting business is in connection with fixed works requiring specialized engineering knowledge and skill.