, we are gathered here at this node
to learn about the people who save our collective butts from paying huge amounts of money to the utility companies
For those who don't do this sort of thing, they are the people who mark up the sidewalks with multicolored spraypaints, or put funny looking flags with your utility's logos in your flowerbeds. There are various companies who do this - there is Underground Services Alert here in Southern California, and others in other regions. All of them, near as I can tell, are collectively known as "digalert", or the "call before you dig" people.
Vandalism, you say? Au contraire, mon frair. See, there's great significance and importance to what these people do. The theory is that these lines they mark on your garden delineate where the underground utilities are going - so that makes two things you don't have to worry about. You don't have to worry about finding them yourself, and you don't have to worry about accidentally puncturing a fiber optic line and cutting off the internet for the rest of your neighborhood.
Sounds really cool, eh? Well, it's more than that. If you cut those FO lines with your fiber-seeking backhoe, it is you who pays for it. Or, if you're doing work for somebody (an excavation company, for instance), they pay for it - but you'll probably lose your job as a result. Let's also remember that, in California, you can be fined for not calling digalert, and dig permits in most areas require that you have a call tag number from them.
So with that, we've discussed why it's a Very Good Thing to call Digalert (and, likewise, not just a Bad Thing, but The Wrong Thing, not to call them).
So here's how it all works.
First thing you do is determine why, where, and how you're going to dig. So find a spot, and make a determination. Are you driving a ground rod for an isolated ground? Digging a hole for a post? Running a new gas line for a room addition? Dropping a septic tank underground? All that considered, where? And most importantly, how? Shovel? Earth moving equipment? A Ditchwitch brand earth cutter? You need to have this information and other bits of information available to Digalert when you call them - they'll tell you what you need, and give you instructions.
Now, this is the part where you need a can of white chalk-based paint. The Lord has commanded you to spray paint the ground where you're going to be excavating - either a small circle around where you're dropping your ground rod, or the general area that you're shoveling up. See, they need to know where you're planning on going underground, so they know where to spray. And note that it must be white. There are reasons for this, and you shall be enlightened.
Now you wait a couple of days. During this time, somebody will come out and start demarcating where the various underground utilities go. They use a veritable rainbow of colors to make it known what utility is there, with appropriate abbreviations:
YELLOW: Natural gas, propane, oil (petroleum lines for instance), fuel lines, or steam. Basically, stuff that burns.
ORANGE: Communications lines (phone, copper, fiber optic, etc.) and cable TV. Usually, in this case, the owner of the lines are noted near the demarcs.
BLUE: Water, natch, but specifically potable municipal water.
GREEN: Sewer lines and/or storm drains
MAROON: Reclaimed water (relatively new)
Now, you can imagine the effects of punching into any of these respective lines with your digging equipment. Aside from the loss of utilities and whatnot, punching into a sewer line is going to smell pretty bad, and there have been incidents recorded where a homeowner, while digging in his yard, thought he struck oil - only because he didn't call to have them lay down a stripe of yellow paint.
So with all that considered, you now need to keep an important thing in mind - it would be extremely wise to usually avoid a single line by about a foot insofar as where you're digging. Give it a nice wide berth. Be afraid - very afraid - of punching a hole in the main water lines. You probably can't afford the damages.
So with that, we conclude - and you are now ready to dig. You HAVE made that phone call, haven't you?
Information on this WU was gleaned from http://www.digalert.com - which also contains many graphics and some abbreviation tables that are exceedingly informative to those who may want to do a dig.
Similar services for other states:
rootbeer277 sez "In Illinois, this service is provided by Julie. In Minnesota, it's Gopher State One Call."