On Sunday August 6, 2006, BP Exploration Alaska notified the NRC of a 4-5 barrel (approx. 200 gallon) crude oil discharge to wet tundra from a leak in a crude oil transit line in their Alaska North Slope Prudhoe Bay crude oil production field. The 30-inch diameter, aboveground transit line runs between Flow Stations 2 and 1 (a distance of approximately 3 miles) and transports crude oil that was processed (oil separated from water and gas) for export via the Trans Alaska Pipeline System. The pipeline is located over wet tundra. There are numerous tundra ponds, drainages, creeks and rivers in the immediate vicinity. The area is frequented by abundant wildlife during summer months including but not limited to brown bears, caribou, arctic fox, and migratory birds including an endangered species of eider. The cause of the leak is unknown at this time although some form of corrosion is suspected since this line was recently evaluated for integrity with a "smart pig" device and 16 significant "anomalies" (areas of pipe wall thinning) were initially detected according to BP. Upon discovery of the leak, BP shut down the pipeline and commenced response and clean-up operation. A START member was dispatched by EPA to the site for monitoring the incident situation and progress and has since demobilized. Personnel from the Alaska Department of Environmental Conservation (ADEC) remain on-scene and US Department of Transportation representatives were also on-scene.
Folding tanks placed underneath the leaking pipeline captured 176 bbl of crude oil until the leak stopped flowing on August 8, 2006. Oil that leaked prior to tank placement impacted an approximate 6,200 square foot area of tundra underneath and adjacent to the pipeline. Cleanup of the oil-impacted tundra progressed from oil recovery via direct suction and rope-mop skimming to a modified flushing technique to mobilize and float remaining oil. Vegetation burning is now in progress as the final planned remediation method. Based on oil quantities collected during recovery efforts and estimated to remain adhered to the tundra (now being burned off), BP has revised the estimate of crude oil released to the ground from 4-5 bbl to 23 bbl (966 gallons.
Leak stoppage allowed for the installation of a patch over the leak site. Five other significant anomaly sites that exhibited signs of minor seepage through the pipeline wall have also been patched as a precaution. All anomaly sites are now receiving a more secure clamps as a source control measure. These steps are not intended as permanent pipeline repairs. Planning for de-inventorying the pipeline to effect final repairs or replacement is in progress.
BP has stopped all oil production in Prudhoe Bay's Eastern Operating Area in response to this incident and the recent pipeline integrity results. The circumstances leading to the discharge will be further investigated.
