What happened

Natural gas began escaping at the Alpine field's CD1 drillsite, appearing at seven wellhouses and through cracks in the gravel pad near a drilling rig. ConocoPhillips relocated about 300 of roughly 400 workers, while local officials and residents said about 20 families left nearby Nuiqsut amid fears about air quality and emergency readiness. Early public discussion considered permafrost thaw, seismic activity and equipment failure, but no cause had then been established. The subsequent Alaska Oil and Gas Conservation Commission investigation classified the event as a shallow blowout: ConocoPhillips had evidence that the C10 Halo interval contained gas but did not adequately isolate it with cement while constructing the WD-03 disposal well. ConocoPhillips estimated that about 7.2 million standard cubic feet escaped, mostly from 4–8 March; additional gas was routed into the Alpine Central Facility until flow stopped on 29 March. Monitoring found no gas off the CD1 pad and no injuries were reported, although some residents and advocates disputed the company's broader no-impact assurances. Regulators later imposed approximately $914,000 in penalties for five violations.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.