How to untangle our underground mess of cables, gas lines, and pipes. | Bing Guan/Bloomberg via Getty Images Buried beneath every American city is a mysterious jumble of cables, pipes, and gas lines, entangled like a pair of wired headphones the moment you pull them out of your pocket. Every time a contractor sticks a shovel in the asphalt, they embark on a high-risk excavate-by-dots obstacle course, dodging color-coded clusters of spaghetti-like power lines, gas mains, sewers, and fiber-optic cables. A line of blue spray paint means water. Red means power. Yellow is gas. Orange is tel...