The construction, installation, maintenance, or repair of oil and gas drilling rigs, decks and associated equipment, earthwork, access roads, foundations, mat roads, monitoring wells, retention tanks and ponds, pipework, pits, and pumps. Also includes the drilling of oil and gas wells and fabrication of oil field equipment, as well as valves, fittings, “Christmas Trees” etc. to regulate the flow of gas or oil on a drilling rig, oil well servicing, workover, and plugging and abandoning wells. Does not include transmission pipelines beyond the drilling field. Oil field construction is a subclassification of Heavy Construction.