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It announced delays to maintenance as part of the cost cutting measures it implemented in March.
The contract for the program began in 2015 was being handled by a joint venture between UGL and UK-based Cape - United Cape Joint Venture.
According to a memo sent by the UCJV to workers dated on Friday, Woodside conducted a review of essential work scopes and the joint venture had been directed to temporarily cease onsite works "with immediate effect".
"As a result of circumstances beyond our control, we cannot usefully employ our employees currently engaged on the Karratha Life Extension Project," the memo said.
"For employees who are currently on roster, you will be stood down from the end of shift today."
UGL declined to comment on the matter.
Woodside however has flatly denied the stand down, telling Energy News any suggestion of additional stand downs from the ones reported last month were "false and misleading".
"These stand downs are as a result of changes in non-essential contractor roles at Karratha Gas Plant were notified to all our contractors on March 23 and were very widely reported at the time," a Woodside spokesperson said this morning.
She referred to Woodside's announcement on March 27, which said its work plan had been reviewed and non-essential activities cancelled, or deferred, which included reduction in the scope of the life extension activities at the gas plant slated for this year.
However AMWU (WA) state secretary Steve Mcartney said their members were not told about the stand downs until Friday, the day the memo was circulated.
"That's what our workers were telling us, they were told they were being stood down on Friday, we were going backwards and forwards trying to get a reasonable outcome and they got treated pretty poorly in my view," he told Energy News.
"There wouldn't be so much mystery around this shit if they actually came out and told people -we're going off the information we got."
The workers stood down are a mix of Karratha-based and fly-in fly-out workers that includes both casual and full-time employees according to the AMWU.
The memo said the contractor was investigating its eligibility for the federal government's JobKeeper program.
Last month Woodside stood down workers at the onshore Karratha Gas Plant and Pluto LNG facility with immediate effect, according to the Offshore Alliance, a coalition of two unions.
The first wave of contractor employees who were summarily stood down worked on Woodside's offshore facilities - the Goodwyn and North Rankin platforms as well as associated floating production storage and offloading units.
According to unions, the number stood down by Woodside over COVID-19 concerns now sits at around 1100.