Before you do any work on your property that involves digging (such as landscaping, planting trees, installing a mail box, building a deck), call the national Call Before You Dig number @ 811. Call at least a few days before you plan to dig to provide the operator with the location of the intended work.
After you call, the 811 service will alert local utility companies, who will send professional locators to mark buried utilities with small flags or water-soluble paint. You can identify the type of utility based on the color of the flags/paint. Google Fiber and other telecommunication providers use orange flags/paint.
For your own safety, do not start digging until buried utilities have been located and marked.