Over a series of recent natural disasters, natural gas service was less likely to be disrupted than electricity service, although restoring gas service was more time-consuming and labor-intensive than power, according to ICF International analysis of major climate-related events in 2017.
The analysis, commissioned by Southern California Gas, looked at the effects of hurricanes Harvey and Irma, along with two rounds of wildfires in California and subsequent mudslides.
"These case studies found that natural gas infrastructure and services were relatively resilient to hurricanes, wildfires and mudslides. Most natural gas infrastructure is belowground, which is inherently less vulnerable to natural disasters than aboveground infrastructure," the report said. Pipeline operators are also increasingly planning for natural disasters in anticipation of changing weather patterns associated with climate change.
Following Hurricane Harvey, which made landfall in southern Texas in August 2017, and Hurricane Irma, which made landfall in Florida in September 2017, gas infrastructure was largely resilient, the ICF study found. The US Pipeline and Hazardous Materials Safety Administration reported two gas-related incidents: one in which a downed power line burned a hole in an underground gas main in Florida and another in which flooding and turbulence may have ruptured a gas line in Texas, the ICF report said.
ELECTRIC OUTAGES
The study contrasted these incidents with the widespread electric outages the storms caused. The Electric Reliability Council of Texas reported more than 293,000 customers without power the day after Hurricane Harvey made landfall, and 4.2 million Floridian customers lost power after Hurricane Irma struck. Some of Florida's coastal communities reported outage rates of up to 97%, the study said.
California's wildfires affected gas infrastructure more than the hurricanes did, in part because utilities shut off service as a pre-emptive measure, the report found. As wildfires spread, Pacific Gas and Electric voluntarily disrupted service beginning October 9, 2017, ultimately disconnecting 42,000 customers, in an effort to isolate damaged assets and to prevent further damage. However, some of PG&E's above-ground gas infrastructure was damaged in the fires, with meters in several locations melting and igniting the gas.
By contrast, about 359,000 PG&E customers lost electric power in the October fires, some of whom were cut off when PG&E deliberately de-energized power lines.
SERVICE RESTORATION
The restoration process for reconnecting the California power customers was much faster than the gas restoration process, because gas workers have to manually relight every pilot light. As a result, while PG&E restored about 5,000 power outages overnight on October 11-12, 2017, only 700 pilot lights were relit on October 11, 2017, the report said.
The study noted that dividing up the gas system further -- perhaps with more interconnects or valves -- could help avoid some of the larger outages by giving companies the option to more precisely isolate particular segments of their system when disasters could affect infrastructure safety.
Mudslides that followed December 2017 California wildfires were more damaging to pipelines than the other events studied, the report said, detailing multiple instances of destruction. A vehicle damaged above-ground gas infrastructure; flowing debris caused a gas leak and related house fire; and swift-flowing water removed two gas lines' normal protective ground cover, exposing one to boulders and destroying the protective concrete slab over the other, among other issues.
Roughly 2,900 SoCal Gas customers also lost gas service after first responders asked that certain sections of the system be isolated for safety reasons, the report said.
