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Sunday 05.02.2012

Pipe burst!

A rupture in a pipeline that began pouring oil and water Nov. 29, creating one of the biggest North Slope crude oil spills ever.

Officials have found a 24-inch (60 cm) 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, told the Anchorage Daily News Dec. 8 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 Dec. 7 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.

"It looks like it was caused by overpressure in the pipe, which we think was linked to ice forming -- the plugs that have formed on either side of the release site," BP spokesman Steve Rinehart said.

Most likely, rapidly forming ice plugs began to grow toward one other, creating a high-pressure area in between.

As for the specific circumstances that caused the line to fail, those are still under investigation, Rinehart said.

BP began X-raying the failed line on Dec. 3, four days after discovering the spill, to check for ice plugs and assess whether it would be safe for cleanup crews to get close to the pipe. They found it was full of ice, a frozen pipeline. One plug was more than one-quarter of a mile long.

"Analysis of the initial images indicates extensive ice plugs within the 18-inch line; one ice plug measured approximately 1,500 feet in length," officials said in a situation report over the weekend.

Crews have been trying different methods of cleanup. They've used a steamer with a four-foot head to melt contaminated snow, which is then vacuumed up. They've flushed out the spill site with warm water. They've used Bobcats to scoop up the mess and vehicles called Rolligons with huge, low-pressure tires to haul it away. They're building an ice road for trucks, though the weather at times has been too warm for the ice road work.