Manufactured gas plants

In the mid-1800s and early 1900s, before natural gas was available as an energy source, more than 1,500 manufactured gas plants (MGPs) were located in cities and towns across the country. These plants used coal and oil to produce gas for the lighting, heating and cooking needs of the local community. With the arrival of natural gas in the 1930s, most of the MGP sites in California were no longer needed and were closed. As was common practice at the time, byproducts of the gas-making process were left buried on-site.

Additional information on the history of MGPs in the U.S. is available at the New York State Department of Environmental Conservation.

PG&E began operating in 1905, approximately 40 years after the first MGP was built in California. In the early years of PG&E’s operations, the company acquired numerous MGPs and properties where these plants had previously operated. Most of the sites in PG&E’s service area were closed and dismantled more than 85 years ago.

PG&E has made significant progress in investigating and remediating the 42 MGP sites it formerly owned or operated. As of 2019, we have completed remediation activities at 30 sites which are now closed or in long-term post-remediation monitoring. The remaining sites are in various stages of remediation, from investigation to active cleanup.

PG&E currently owns all or portions of approximately 23 former MGP sites, most of which house PG&E substations, service centers or other utility operations facilities. The remaining sites are owned by private parties.

PG&E looks for residues from the historic gas manufacturing process. The most common are coal tar and lampblack. Coal tar is a black substance that looks like and is chemically similar to roofing tar. Lampblack looks like and is chemically similar to soot from a candle. In some instances, these materials can have an odor that smells similar to roofing tar, asphalt or mothballs.

The residues found at MGP sites are comprised of many chemicals and generally include polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). PAHs, found in MGP residues such as coal tar and lampblack, naturally occur in coal, crude oil and gasoline. They also may be formed when organic materials such as wood, tobacco or even foods burn at high temperatures.

VOCs get their name from their ability to pass easily from a liquid into a gaseous state. They are compounds commonly used to build and maintain homes, in cleaning products and in industrial manufacturing processes. MGP-related VOCs are major ingredients in nail polish, disinfectants, moth repellants and many other commercial products.

Additional information on PAHs and VOCs is available at the Agency for Toxic Substances and Control Registry.

There is no indication that these sites pose any health concerns to the public because, in most cases, MGP residues are located below the ground surface where direct contact exposure is unlikely. This is the conclusion of some of the country’s leading health experts and toxicologists based on extensive research of MGP sites across the country, as well as work conducted to date by PG&E.

While exposure to MGP residues is not common, under certain conditions, they can affect human health. PG&E’s remediation program ensures that these sites will remain protective of public health and the environment over the long-term in accordance with today’s regulatory standards.

No, drinking water supplies have not been affected by MGP residues at any PG&E site.

PG&E is committed to providing timely information through a variety of methods including briefings with key City/County staff, meetings with interested community groups, door-to-door outreach to nearby residences and businesses, public meetings/open houses, fact sheets, work notices and other outreach, as appropriate.

Should you have a question about one of our MGP sites, please call our Environmental Remediation toll-free response line at 1-866-247-0581. Calls are returned the same day or next business day.

The safety of the community is our number one priority. We put in place community protection measures during remediation to reduce impacts from noise, dust and traffic to the greatest extent possible. This can range from sound blankets to limiting equipment speeds to spraying the site with water to keep soil damp. We work closely with community members as needed to provide additional measures to further reduce impacts when concerns arise.

In the rare situations where a customer has told us that even with mitigation measures the work will still have a significant, disruptive impact on their daily activities or business operations, we have provided an alternate place for them to live or work during construction that meets their needs and addresses their concerns.

Many sites will continue to look similar after cleanup than before since the impacts are typically below ground and not visible at ground level. Where possible, we have conducted restoration activities like planting new landscaping, repairing sidewalks or constructing new parking spaces. You can see examples of this work at our former Colusa MGP, Lodi MGP, Monterey MGP, Santa Cruz MGP and Watsonville-1 MGP.

If you have additional questions, please contact us at 1-866-247-0581 (toll-free) or remediation@pge.com. Calls are returned the same or next business day. You may also visit the California Department of Toxic Substances Control’s Envirostor website or the Regional Water Quality Control Board’s Geotracker website for more information on specific PG&E sites.