In 1870, New York's subway system opened after workers had dug through miles of pipes, lines and cables with some mishaps along the way. As years went by and more subways were dug through even more underground lines and cables, the work became even more tedious and dangerous. The same problems exist with your house because there are thousands of feet of pipes, cables and power lines buried only a few feet under your yard. If they're cut, all sorts of problems could arise. Water could be disrupted and contaminated. Phones and emergency services like 911 could be interrupted and broken gas lines could cause an explosion. How can you know what's underfoot? Most areas now have "one-call" centers supported by local utilities. They contact each company to come out and mark buried lines at no charge. Soon there'll be one number for the whole USA. Until then, check your phone book or contact a local utility for the number in your area. Then call, before you dig. And that's the On The House tip for today.