Blowout and Public Health Disaster

The Aliso Canyon natural gas storage facility is situated in the Santa Susana Mountains in Los Angeles County, California, north of the Porter Ranch neighborhood of the City of Los Angeles. The Aliso Canyon gas storage facility is owned and operated by the Southern California Gas Company (SoCal Gas), a subsidiary of Sempra Energy. On October 23, 2015, the largest gas blowout in the history of the United States began at the Aliso Canyon gas storage facility. An estimated total of 109,000 metric tons of methane flowed uncontrolled from Aliso Canyon Well SS-25 until it was successfully sealed 111 days later, on February 11, 2016.

As a result of the blowout, people in neighboring communities experienced "rotten egg" odors, oily mists, and acute health symptoms, including eye, nose, and throat irritation, headaches, and respiratory symptoms. In response to thousands of health problems subsequently experienced by residents, Public Health directed the temporary relocation of over 8,000 households in the surrounding areas. Many residents reported ongoing health problems after returning home from temporary relocation and expressed concerns about potential long- term health effects.

Detailed information on the Facility's SS-25 well failure is available on the California Public Utilities Commission website.

Public Health's Role in the Blowout and Disaster

Public Health issued a directive to SoCal Gas to expedite efforts to stop the blowout and, in the interim, offer free, temporary relocation to affected residents. Additionally, Public Health issued a separate directive to SoCal Gas to work directly with the Los Angeles Unified School District to assist in temporarily relocating affected students to alternate locations outside of the impacted area.

Public Health implemented an Expanded Air Monitoring Plan (EAMP) to comprehensively evaluate air quality in the Porter Ranch area in response to the natural gas leak at the Aliso Canyon natural gas storage facility. Implementation of the EAMP was part of an ongoing effort to consolidate and evaluate data collected by multiple parties, including Los Angeles County Fire Department (LACoFD), SoCalGas, South Coast Air Quality Management District (SCAQMD), Los Angeles Unified School District (LAUSD), and California Air Resources Board (CARB).

Following the sealing of the well, outdoor air monitoring was continued by the California Air Resources Board (CARB) and the South Coast Air Quality Management District (SCAQMD), with Public Health documenting and monitoring community health concerns and consulting with local and state regulatory agencies. Public Health also continued to actively monitor and assess environmental and health issues related to the disaster, recording ongoing symptoms reported by residents. Following the blowout, Public Health conducted a Community Assessment for Public Health Emergency Response (CASPER) and an Indoor Environmental Testing Protocol, testing for over 250 chemicals in indoor air and household surface dust samples. Testing was conducted in 101 Porter Ranch homes near the Aliso Canyon Storage Facility, two schools and 11 homes outside the Porter Ranch area. Additionally, Public Health tested indoor air and dust in some area homes and based on the results, directed SoCal Gas to pay for professional comprehensive cleaning of the homes of area residents. Public Health designed a cleaning protocol and helped to secure a ruling from the Los Angeles Superior Court requiring the SoCalGas to offer interior cleaning to residents relocated at the time of the ruling.

Los Angeles County joined with local and state public agencies in the lawsuit against Southern California Gas Company, successfully advocating for the inclusion of a health study in the Settlement.

Resource: Who Regulates the Southern California Gas Company?


On August 8, 2018, California Attorney General Xavier Becerra, along with the California Air Resources Board, Los Angeles City Attorney Mike Feuer, and the County of Los Angeles secured a $119.5 million settlement with Southern California Gas Company over the Disaster. As part of this settlement, $25 million was secured for a long-term health study.