As used in this chapter:
(a) “Competent spoil” means soils that can be treated to bring their moisture content into the optimum range, and that can achieve the compaction required by the city or county in whose jurisdiction an excavation is located.
(b) “Excavation” means any operation in which earth, rock, or other material in the ground is moved, removed, or otherwise displaced by means of tools, equipment, or explosive in any of the following ways: grading, trenching, digging, ditching, drilling, augering, tunneling, scraping, pipe plowing and driving, or any other way.
(c) “Local agency” means any city, county, city and county, special district, school district, or other political subdivision of the state.