Manufactured gas plants
Frequently asked questions
What is a manufactured gas plant?
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 lighting, heating and cooking. With the arrival of natural gas in the 1930s, most of the MGP sites in California were no longer needed and were closed.
Additional information on the history of MGPs in the U.S. is available at the New York State Department of Environmental Conservation.
What is PG&E’s connection to manufactured gas plants?
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 area of service were closed and dismantled more than 75 years ago.
How many sites is PG&E working on?
PG&E is in the process of investigating and remediating 41 MGP sites it formerly owned or operated. They are in various stages of remediation, from investigation to post remediation monitoring and project completion.
How many sites does PG&E still own or use?
PG&E currently owns all or portions of approximately 27 former MGP sites, most of which house PG&E substations or other utility operations facilities. The remaining sites are owned by others.
What are you looking for at these sites?
PG&E looks for residues from the historic gas manufacturing process. The most common residues found at historic MGP sites 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. These materials can in some instances have an odor similar to roofing tar or fresh asphalt.
What chemicals are associated with MGP residues?
The residues found at some MGP sites are comprised of many chemicals, including polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). PAHs, found in MGP residues such as coal tar and lampblack, are chemically similar to materials commonly found in the environment from natural and human activities, especially those that involve burning, for example, fossil fuels, cigarette smoke, fireplaces, forest fires, grilling meats, etc. MGP-related VOCs are major ingredients in nail polish, disinfectants, moth repellants and many other commercial products.
Do these sites pose any concerns to public health?
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 toxicologists and health experts 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, MGP residues in the environment can affect human health. The purpose of our program is to reconfirm that these sites will continue to have no impact on public health in the future.
Is drinking water affected?
No, drinking water supplies have not been affected by gas plant residues at any PG&E site.
How is the community kept informed of site activities?
PG&E keeps the community informed of site activities and progress through door-to-door outreach, public meetings, fact sheets, work notices and other outreach, as appropriate.
Do you ever relocate people during remediation?
Measures are put in place during remediation to reduce impacts related to noise, dust and traffic on nearby homes and businesses. In situations where a customer has told us that, even with the mitigation measures, the work will 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 the construction period that meets their needs and addresses their concerns.
What do sites look like after remediation is complete?
Each site is different, depending on such factors as whether the property is residential or commercial, whether there are redevelopment plans for that area, and whether it is in an urban or rural area. Many sites will continue to look much the same after cleanup as before since the impacts are typically below the ground and not visible at ground level. Where possible, such as at our former Monterey MGP, we have conducted restoration activities like planting new landscaping, repairing sidewalks or constructing new parking spaces.
There is no indication that PG&E's former MGP sites pose any health concerns to the public, based on our testing, experience, and extensive review of medical literature.