PG&E's neighborhood distribution pipelines branch off from larger regional transmission lines to deliver natural gas to homes and businesses. Distribution pipes are much smaller than transmission pipes, and operate at lower pressures.In addition to our regular patrols and leak surveys, PG&E has multiple programs governing the safety of our neighborhood distribution system.
Under the Distribution Integrity Management Program launched in August 2011, we analyze our system holistically to identify pipelines for further inspection or potential replacement. This holistic approach captures as much data as possible to enhance safety.We also have programs that follow a more targeted approach. For the past 20 years, PG&E has been modernizing our distribution system through the Gas Pipeline Replacement Program by replacing cast iron and pre-1940 steel distribution lines with new plastic pipe. Plastic pipe is more flexible and reliable during earthquakes, and is the preferred pipeline material for California. We’re also replacing all copper pipelines through 2013 with our Copper Service Pipeline Replacement program.
One of the challenges in urban areas is potential interactions with other underground utilities.When a new utility line is installed in an urban area, it’s very common to dig horizontally underground (called “directional boring”) instead of digging a trench. This method avoids damage to sidewalks, patios, and landscaping. However, because sewer lines are not mapped or marked by 811, in rare cases our small-diameter pipeline may inadvertently cross through a sewer pipe. We have safety programs in place to prevent this from happening, and to inspect our previously installed pipelines.