Have you heard to term "call before you dig" ? If you're a plumbing service provider this term should be familiar. Very familiar! If you're a property owner ask your plumber if he/she is familiar with the term. If not, it's time to find another plumber. USA is an organization that provides services to locate and mark underground utilities. These underground utilities can include natural gas lines, electrical lines, telecommunication lines, etc. Marking underground utilities lets the plumber know where the lines are located. Knowing a location helps the plumber avoid and not damage these lines during a repair. So, ask you plumber if he/she "calls before they dig". The picture included shows a natural gas line that was marked via a USA mark and locate. Our plumber knew the location, and left it untouched and safe.