Spill among the worst on North Slope

What seemed like a small leak of a mix of oil and water from the North Slope oil fields a week ago is looking more like one of the area’s largest, with about 46,000 gallons leaking onto the frozen tundra.
The 18-inch line apparently froze, with one ice-plug measuring more than one-quarter-mile long, leading to a build-up in pressure within the pipe:

“Officials have found a 24-inch jagged rupture in a pipeline that began pouring oil and water Nov. 29, creating one of the biggest North Slope crude oil spills ever.
The on-scene coordinator for the state Department of Environmental Conservation, Tom DeRuyter, said Tuesday that the breach on the bottom of the pipe was the biggest he had ever seen and indicative of the incredible pressure the pipeline was under when it split.
Workers located the source of the leak Monday after cleanup crews hauled away spilled crude and contaminated snow and ice that had been obscuring the area.
Officials say massive ice plugs had formed inside the pipe, which caused BP Exploration (Alaska) Inc. to stop operating it a few weeks ago. Pressure then built up until the pipeline ruptured, according to BP.

The largest spill of the North Slope pipeline system was in 2006 when more than 200,000 gallons of crude leaked from a corroded transit line. That led to a criminal misdemeanor conviction for BP, $20 million in fines and restitution, and three years of probation, which the company is still on.