More than two weeks after workers at Chevron's Gorgon LNG plant were first allegedly contaminated with toxic mercury the safety regulator does not know when it will receive results to determine if the exposures were unsafe.

Unions have reported three incidents involving four workers to the WA safety regulator WorkSafe. The incidents occurred during a major planned maintenance shutdown, or turnaround, of the third of Gorgon's huge LNG trains on Barrow Island.

The Offshore Alliance detailed on social media the drenching in chemicals of a Contact Resources employee working on a slugcatcher on about April 26. The worker then could not find a nearby operational safety shower.

In another incident three days later, a Contract Resources worker was in a vessel affected by mercury for more than an hour with inadequate personal protective equipment, according to the Offshore Alliance.

In a third incident reported by the union, two electrical and instrumentation technicians working for UGL were tested on May 1 by a qualified mercury tester and advised they were contaminated.

A WorkSafe spokesperson confirmed that four workers were involved in the reported incidents.

Boiling Cold asked WorkSafe how many of the exposures were above legal and or safe limits.

The WorkSafe spokesperson said all the workers had been tested, and the regulator does not know when the full results will be available.

"The investigation is in its early stages, and there is no estimated completion date," the WorkSafe spokesperson said.

"WorkSafe is currently ensuring that the employer is instigating appropriate measures and improvements in relation to the alleged events."

A Chevron spokesperson said onsite response teams acted immediately after the incidents.

The company is also investigating "instances of potential localised mercury exposure" at Gorgon, the Chevron spokesperson said.

"At this time, no adverse health effects from exposure to a hazardous substance have been recorded,

"While precautionary health monitoring is ongoing, personnel have resumed duties."

"Robust safety procedures are in place in all areas where mercury is handled…and additional protocols have been implemented at Gorgon in response to recent events."

The Gorgon plant has mercury removal units at the front end of its processing equipment to filter out the toxic substance that can damage equipment. The MRUs are contained vessels that are only emptied during turnarounds.

Boiling Cold understands Chevron discovered more mercury than it expected during this turnaround which is the first to work on the inlet area where the incidents occurred.

Gorgon's continuing problems with mercury

Mercury is a common problem in LNG plants, and safely disposing of the metal collected is not straightforward.

Woodside was a foundation customer for Contract Resources $20 million hazardous waste treatment plant in Karratha that opened in 2018. Before the plant opened, the Pluto and North West Shelf LNG operator sent its mercury waste to Switzerland for treatment and disposal.

Department of Mines, Industry Regulation and Safety director dangerous goods and petroleum safety Steve Emery said Chevron was licensed under the Dangerous Goods Storage Act to store and handle quantities of mercuric compounds.

"The department regularly inspects Chevron for compliance with the DGSA and its licence," Emery said.

The recent incidents on Train 3 are not the first time mercury has troubled the Gorgon project.

Gorgon was initially designed to handle lower amounts of mercury in the gas arriving on Barrow Island from the Gorgon and Jansz-Io offshore fields.

In 2015, six years after construction commenced, Gorgon's licence was amended to allow for the installation of additional mercury removal units after the mercury level in the gas from the Gorgon field was found to be higher than expected.

In 2018 concerns were raised about vapours containing mercury and toxic BTEX chemicals being vented to the atmosphere for the past two years.

The chemicals were meant to be disposed of in Gorgon's carbon dioxide injection system, but that did not operate in the early years of the LNG plant's operation. The $3.1 billion system is now working at less than full capacity due to technical problems.

In 2019 Chevron was temporarily permitted to dispose of the vapours in a gas flare further away from workers.

Steam cleaning of equipment on Train 2 in April 2019 resulted in up to half a tonne of water containing mercury discharging onto equipment and the ground.

Chevron reported the incident to the Department of Water and Environmental Regulation in an annual compliance report.

The causes were a faulty level indicator, overly simplistic work instructions and excessive flow rates.


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Main image: Gorgon LNG plant on Barrow Island. Source: Chevron Australia Pty Ltd