811 is the national call-before-you-dig phone number. Anyone who plans to dig should call 811 or go to Texas811's website two business days (excluding weekends and holidays) before digging to request that the approximate location of buried utilities be marked with paint or flags so that you don't unintentionally dig into an underground utility line. This is required even if you're working in your own backyard.
Signs of a potential leak
Strong petroleum or sulfur (rotten eggs) odor
Dead vegetation or liquid on the ground near a pipeline, dirt being blown into the air or a dense white cloud or fog
The US Department of Transportation's Pipeline and Hazardous Materials Safety Administration maintains the National Pipeline Mapping System Public Map Viewer. It is a web-based mapping application designed to assist the general public with displaying and querying data related to: gas transmission and hazardous liquid pipelines, liquefied natural gas plants, and breakout tanks. Please note that this application does not contain distribution or gas gathering pipelines.