* Dig ditches or trenches, backfill excavations, or compact and level earth to grade specifications, using picks, shovels, pneumatic tampers, or rakes. * Mix, pour, or spread concrete, using portable cement mixers. * Tend pumps, compressors, or generators to provide power for tools, machinery, or equipment or to heat or move materials, such as asphalt. * Erect or dismantle scaffolding, shoring,...