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Round the clock monitoring at site of slow leak on pipeline
Alyeska Pipeline Service Co. found a slow leak at an isolation fitting just north of Pump Station on May 29. The release was found during excavations to investigate a corrosion inspection anomaly in a separate location among the main line, the Alaska Department of Environmental Conservation’s Division of Spill Prevention and Response said in a June 5 situation report. Alyeska personnel then discovered discolored gravel at the electrical isolation joint.
The spill was described as a slow weeping of crude oil. Pump Station 10 is along the Richardson Highway at milepost 219, Trans-Alaska oil pipeline milepost 585.91.
DEC said PS 10 has been out of service since 1998, but is being used to support operations along the line.
The spilled product from the isolation fitting is Alaska North Slope crude oil, a determination based on laboratory sample results, the department said.
The initial weep rate was about one drip per second and DEC said oil had accumulated within the tar membrane/packing material that covered the coupling and dripped from the fitting once the soil surrounding the pipe was removed. No active weeping was immediately observed when the tar membrane and tar were removed from the pipe, but small dampened areas started to appear later on the coupling surface, indicating weeping from the joint was still active.
DEC said Alyeska estimates some 10 gallons have been released, with minor weeping continuing.
Round the clock monitoring Alyeska has “round the clock monitoring at the site with containment in place and crews and a vac truck on site,” Alyeska spokeswoman Michelle Egan told Petroleum News in a June 10 email.
“We are engineering a repair and determining the best and safest approach to repairing.” Egan said the weep is releasing at a rate of less than a teaspoon a day.
DEC said in its June 5 situation report that source control had not been achieved due to the nature and location of the source, but said plans are being developed to achieve source control.
The source has been determined to be an isolation fitting installed on the 48-inch trans-Alaska oil pipeline mainline. The purpose of the isolation fitting was to electrically isolate the mainline and facility piping cathodic protection systems to provide optimal corrosion protection.
The fitting at issue was installed during initial pipeline construction, DEC said.
The isolation fitting is not currently needed due to upgrades in the cathodic protection systems and has been electrically bypassed.
Response DEC said Alyeska personnel have removed contaminated gravel that is accessible and continue to contain and recover any additional oil weeping from the fitting. Alyeska is monitoring the area on a 24-hour basis to ensure the leak rate is not increasing and has response equipment on site for immediate use if the weep were to increase.
If conditions warrant, DEC said, the isolation joint can be isolated by closing the surrounding mainline block valves.
Alyeska is continuing to monitor and is developing cleanup plans for DEC review and approval.
DEC said it is unknown at this time if shutting down the mainline will be necessary to complete repairs.
In addition to identifying and correcting the cause of the release, DEC said Alyeska is developing protocols for assessing 21 other isolation fittings along the system.
- Kristen Nelson
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