The formal decision, to be released today following a three-year environmental impact assessment, has shocked the project's partners, ExxonMobil, Chevron and Shell, according to a report in today’s Australian Financial Review.

Under the plan, gas from the Gorgon and Io/Jansz field would be processed on Barrow Island, which is about 70 kilometres offshore.

The proposed processing plant would use existing pipelines which already crisscross Barrow Island.

The Gorgon partners have said the project could increase Australia's GDP by $2 billion and boost exports by $1.2 billion. It could also create up to 6000 jobs directly and indirectly.

But the multi-billion dollar project’s planned site is a nature reserve off the Pilbara coast of north-west Western Australia.

The EPA is expected to find that the risks to Barrow Island from dredging of the sea floor and the possible introduction of non-native flora and fauna are too great.

In 2003, the EPA opposed the siting of the gas plant on the island and was overruled by the state government. It is likely that WA Premier Alan Carpenter, a former Energy and Resources Minister, will again overrule the agency.