Anchorage, AK -- December 6, 1996 -- Alyeska Pipeline Service Company today released the findings of an interim report on Thompson Pass pipeline integrity. The pipeline has experienced vibrations in this area due to declining throughput. Alyeska hired a team of experts to analyze the vibration's affects on nine areas of concern, and the interim report addressed the most significant anomaly closest to the pressure pulsations.

The findings conclude:

• Eliminating the pressure pulsations eliminates the integrity concern
• This should be done as soon as practical
• Backpressure measures are an appropriate solution to the vibrations
• If a dig is necessary, it should not be conducted until backpressure is in place
• If the vibrations continue unchecked at rates experienced this fall, integrity concerns could arise in 3 to 23 years

Alyeska is currently working to install temporary backpressure from the Valdez Marine Terminal up the slope of Thompson Pass, thereby eliminating the pressure pulsations. This system will be in place as soon as possible, by the end of January, 1997. Until the temporary backpressure is in place, Alyeska is working with the North Slope Producers to manage throughput to minimize the vibrations. The company is accelerating the permanent backpressure project, which is slated for completion by the summer of 1997.

The integrity analysis will continue on the other anomalies in the Thompson Pass area. The results of that analysis will be available in January. The eight other areas of concern are less significant than the governing area of concern, and most are further away from the strongest pressure pulsations. It is anticipated that recommendations from the additional analysis will be similar to actions already underway to mitigate the vibrations. Based on the final stress analysis report, Alyeska will design an inspection and repair program.

Alyeska will use three methods to monitor in the area. Soil gas probes will continue to be used at seven locations along the Thompson Pass downslope. In addition, four hydrocarbon sensors will be installed underground at different boring sites. They will be wired to send a 'real-time' signal to the Operations Control Center in Valdez. This technology is approved by the Environmental Protection Agency and is in use to monitor tanks at gas stations. Alyeska will also be able to monitor two wells which were installed as part of the spill investigation. These wells are two inches in diameter and will allow Alyeska to inspect near the governing area of concern. Alyeska will continue to closely monitor the area and maintain the enhanced oil spill contingency plans that were developed during the spill investigation.

Information generated from the Thompson Pass slackline project will be used to assess other possible slackline situations along the pipeline. Currently Keystone Canyon is the only slackline condition, and no vibrations occur there. Other possible slackline locations occur at Atigun Pass, Isabel Pass, and Finger Mountain. The pressure pulsations associated with slackline conditions are rare, and not anticipated at the other locations. However, Alyeska will use the information gathered from the Thompson Pass situation to plan for declining throughput.

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