Unlike other cancers, the vast majority of skin cancers have no potential to spread to other parts of the body (metastasize) and become life-threatening. There are two major types of skin cancer: basal cell carcinoma (the most common) and squamous cell carcinoma (the second most common). Melanoma is also a form of skin cancer but is far less common, though more dangerous, than the other two varieties.
OSHA defines an excavation as any man-made cut, cavity, trench, or depression in the earth's surface formed by earth removal. This can include excavations for anything from cellars to highways. A trench is defined as a narrow underground excavation that is deeper than it is wide, and no wider than 15 feet (4.5 meters).
Backgouging: The removal of weld metal and base metal from the weld root side of a welded joint to facilitate complete fusion and complete joint penetration upon subsequent welding from that side. Backhand Welding: A welding technique in which the welding torch or gun is directed opposite to the progress of welding. Backing Gas: Backing in the form of a shielding gas employed primarily to provide a protective atmosphere.