On Thursday March 2, 2006, BP Alaska reported an oil discharge of an unknown quantity from a flowline carrying crude oil on the North Slope's Prudhoe Bay oil field. The spill location is in the western operating area of the field between Gathering Center 1 and Gathering Center 2. Site conditions at the time of the spill were frozen tundra covered with snow. Spill responders from BP and Alaska Clean Seas responded with vac trucks and BP shut down its process and depressurized the line. Based upon Historic Properties checks from other spills in this area there are no known cultural or historic sites impacted by the spill. DOI was notified, and the USFWS has been involved in the response and cleanup effort to evaluate the risk to wildlife and natural resources. The spill was found to have impacted 1.93 acres, consisting mainly of frozen tundra but also a portion of an adjacent frozen lake.
On March 10, 2006, the Unified Command released a preliminary estimate of the volume of oil spilled. The estimate was between 201,000 and 267,000 gallons and is based upon GPS mapping of over 1,800 oil thickness data points and surveyor calculations done by the Volume Estimation Team. The source of the leak was found to be a 1/4 inch hole in the bottom of the pipeline at the six o’clock position, in a portion of the pipeline that passes underneath a gravel caribou crossing. A BP leak investigation report places the cause of the release on internal pipe corrosion.
Clean-up efforts progressed from the initial free-product vacuuming recovery effort that yielded approximately 63,000 gallons of oil to the removal of over 9,000 cubic yards of contaminated snow to the trimming off (grinding) the top layer of contaminated ice and tundra throughout the spill area to remove residual oil contamination. Once cleanup verification samples showed that trimming had successfully met State of Alaska cleanup levels, backfilling of trimmed areas with organic matter and a replacement tundra mat took place to restore the trimmed area to its natural condition and prevent permafrost melting. Backfilling, followed by the placement of a protective snow layer, was completed on April 30, 2006. This signaled the completion of planned cleanup operations with the exception of any oil sheen control or tundra restoration support work needed over the upcoming spingtime break-up and summer periods.
On April 25, 2006, the measurement of oil in a holding tank recovered via free-product vacuuming and contaminated snow melting showed 177,059 gallons of oil. This figure, along with the still-to-be determined amount of oil contained in contaminated tundra/ice trimmings and contaminated caribou crossing gravel, constitutes what will be considered the final spill volume determination.
EPA OSCs and START contractors as well as ADEC responded immediately to the incident. They conducted on-site monitoring and participated in the incident's Unified Command. The UC later transitioned to a project management structure for the final cleanup stages. With all planned cleanup activities now completed, no agency personnel are presently on-site. Return visits by the EPA or START to view site conditions may be performed. For additional site information see the Documents and POLREP sections of this website.
