Natural Gas and Hazardous Liquid Transmission Pipelines

Proximity to a transmission pipeline does not of itself indicate a safety risk. However, on September 9, 2010, a Pacific Gas and Electric (PG&E) natural gas transmission pipeline exploded in San Bruno, California, causing loss of life and extensive property damage. Following this incident much attention has focused on the presence of natural gas and hazardous liquid pipelines in the vicinity of residential neighborhoods. As a result, PG&E periodically notifies residents and businesses within 2,000 feet of PG&E's natural gas transmission pipelines about their proximity, and other gas utilities in California have done likewise. Therefore, many believe that notification of a transmission pipeline within 2,000 feet may be material to a residential property transaction.

Transmission vs. Distribution Pipelines

The 2,000-foot proximity determination in this residential disclosure report covers gas "transmission" and hazardous liquid pipelines only. It is important to note that every home that uses natural gas is connected to a gas "distribution" pipeline. Distribution pipelines are generally of smaller size and lower pressure than transmission pipelines. This disclosure does not include distribution pipelines nor is it meant to indicate there is no risk associated with distribution lines. While proximity to a pipeline does not of itself indicate a safety risk, excavation near a pipeline poses a definite hazard. For this reason, this disclosure includes an advisory about how to spot and avoid buried pipelines on and near a property.

The U.S. Department of Transportation, Pipeline and Hazardous Materials Safety Administration (PHMSA) administers the national regulatory program to monitor the transportation of natural gas, liquefied natural gas (LNG), and hazardous liquids by pipeline. PHMSA and the U.S. Office of Pipeline Safety (OPS) maintain a database of pipeline information called the National Pipeline Mapping System (NPMS) in cooperation with other federal and state governmental agencies and the pipeline industry. The NPMS is created using data compiled from mandatory submissions to PHMSA made by operators of pipelines and LNG plants, and from voluntary submissions made by breakout tank operators. The data is processed by private contractors. Since 2002, transmission pipeline and LNG plant facility operators are required to update their submissions annually.

The PHMSA website provides a Public Map Viewer that allows the general public to view pipeline maps in one county at a time. The viewer displays maps and associated data identifying transmission pipelines, LNG plants, and breakout tanks stored in the NPMS database. The data include information about the pipeline commodity (e.g., natural gas or liquid fuel), pipeline operator, agency contact, etc. The Public Map Viewer can be accessed at the following address:

The pipeline disclosure in this report is based on a proximity search of the gas transmission pipelines and hazardous liquid pipelines depicted in NPMS Public Map Viewer at a scale of approximately 1:24,000. That map scale is the maximum resolution at which pipelines are displayed. At that map scale one inch on the map equals approximately 2,000 feet on the ground, which is the same scale as regulatory maps required for statutory natural hazard disclosure in California. NPMS data should be considered no more accurate than +/- 500 feet and must never be used as a substitute for contacting the appropriate one-call center prior to digging. To identify a specific pipeline owner/operator, please use the NPMS Public Map Viewer at the web address above. For policy and technical questions regarding NPMS, please contact PHMSA directly.