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UNGS Major Incidents

Aliso Canyon

On October 23, 2015, an underground natural gas storage well, Southern California Gas Company’s (SoCal Gas) Aliso Canyon Well SS25, failed. The failure resulted in a sustained and uncontrolled natural gas leak in an area known as Porter Ranch in Los Angeles, California. Over 5,000 households (families) in the Porter Ranch area had to be relocated. California Governor Jerry Brown declared the Aliso Canyon incident a state emergency. After repeated unsuccessful attempts to contain the leak, a relief well was drilled to plug the leaking well.

The Aliso Canyon underground storage field can store up to 86 billion cubic feet of natural gas. It has 115 storage wells and is the second largest storage facility of its kind in the United States. The well was drilled in 1953 and was later converted to a natural gas storage well in 1972. Initially, the leak from Well SS25 was believed to be from the subsurface (downhole) well casing. PHMSA worked closely with the State of California to provide technical assistance and to support State regulatory agencies in their response and oversight activities related to this incident. Information on the Aliso Canyon incident and well remediation for the field located near the Porter Ranch area can be found on the following State of California link:

In the wake of the Aliso Canyon incident, the U.S. Department of Energy (DOE) and the Department of Transportation’s (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) established an Interagency Task Force on Natural Gas Storage Safety. The Task Force included premier scientists, engineers and technical experts from across the DOE complex, including five National Labs, DOT, the Environmental Protection Agency (EPA), the Department of Health and Human Services (HHS), the Department of Commerce (DOC), the Department of the Interior (DOI), the Federal Energy Regulatory Commission (FERC), and the Executive Office of the President.

Other Underground Natural Gas Storage Facility Incidents

Since 2001 several accidents involving underground gas storage facilities have occurred and two of the more extensive accidents that occurred in Texas and Kansas are highlighted below.

On August 19, 2004, the Market Hub Partners Moss Bluff storage facility located in Liberty County, Texas, had a well control incident and natural gas fire at Cavern #1. Over a period of six and one-half days, approximately 6 billion cubic feet of natural gas was released from the cavern and burned. The fire eventually self-extinguished, and late on August 26, 2004, installation of a blowout prevention valve was completed, effectively placing the well back under control.

The Moss Bluff storage facility was comprised of three separated underground caverns leached out of a salt formation beneath the surface; a compressor station to help move natural gas into and out of the caverns; well head assemblies on each of the caverns for operational control purposes; and natural gas, fresh water and salt water (brine) piping and related facilities to facilitate transportation and/or holding of those materials A detailed investigation by company personnel and outside consultants determined the accident was caused by a separation of the 8 and 5/8-inch well string inside the cavern; a breach of the 8-inch brine piping above ground; and the separation of the wellhead assembly above the cavern.

On January 17 and 18, 2001, an accident occurred at the Yaggy underground natural gas storage field operated by Kansas Gas Service. At the Yaggy storage field, natural gas was injected to a depth of 600 to 900 feet underground into salt caverns. Gas leaked from the storage field well production casing, migrated approximately nine miles underground, and then traveled to the surface through old brine, or salt wells, in the Hutchinson, Kansas area. This led to a series of gas explosions in Hutchinson, Kansas. An explosion in downtown Hutchinson destroyed two businesses, damaged 26 other businesses, and killed two persons in a mobile home park. Approximately 143 million cubic feet of natural gas leaked from the storage field.