The map below from the National Pipeline Mapping System (https://www.npms.phmsa.dot.gov/) shows the general location of the hazardous liquid (red) and the gas transmission (blue) pipelines in Contra Costa County. These maps should not be used as a substitute for calling 811 and having utilities located before any digging, as required by law.
Anyone can access these maps to see where hazardous liquid and gas transmission pipelines run through their community. The map below shows the two main pipelines running through the Alamo area – the Kinder Morgan San Jose Line in red and the PG&E natural gas line in blue. The public viewer for the maps is available online at: https://pvnpms.phmsa.dot.gov/PublicViewer/
PG&E also maintains an interactive map system that will allow you to locate its transmission lines anywhere in its service area. The image below is an example of what you can see. https://www.pge.com/en_US/safety/how-the-system-works/natural-gas-system-overview/gas-transmission-pipeline/gas-transmission-pipelines.page
Please note: These maps do not include the locations of gas distribution lines. And again, the location of pipelines in these maps is ± 500 feet, so they should not be relied on for anything other than general location. Call 811 before any digging to have utilities located.