According to the Gladstone Observer a number of people were arrested as the union picketed the ferry terminals for the Gladstone LNG and Queensland Curtis LNG projects in Gladstone.

"It was reported that traffic was backed up for more than 3.5km as CFMEU members began their strike action against construction giant Bechtel," the newspaper revealed.

"Gladstone residents took to social media to highlight their frustration at traffic delays, with one saying the protesters ‘don't stop to realise that non-Bechtel and non-island workers need to get to work. They don't just stop their work, they stop other businesses too. Picketing should be made illegal.'"

Bechtel's more recent update this morning was more dramatic.

"About 50 people affiliated with the CFMEU sought to disrupt our three projects today by blocking access to ferry terminals and engaging in abusive, dangerous and illegal behaviour," Bechtel Gladstone general manager Kevin Berg told Energy News Bulletin.

"Not only did they place large rocks across the road, they kicked and spat at cars, threw rocks and one person was pushed off of his motorbike during the picket action."

Bechtel claimed that many in the picket line were CFMEU officials and some were even "people who have no association with the projects at all".

"We are appalled at this behaviour and outraged that the CFMEU, which says safety is a priority, would behave like this," Berg said.

"Many of the protestors who turned up prior to 4am were clearly under the influence of alcohol and even brought alcohol with them.

"We believe everyone has the right to have their say. However, the CFMEU's actions today are completely unacceptable and illegal."

He also thanked the vast majority of its 13,000 employees for their patience and tolerance.

"Many reported to work as normal, despite the unsafe and illegal actions of a few," he said.

ENB is seeking comment from the CFMEU.

Earlier this week the industrial action was predicted to start on Thursday and involve crane operators going on an "indefinite strike".

The CFMEU is mainly campaigning for a more family-friendly roster of three weeks on with one week off, compared to the existing 4&1 roster of the enterprise agreement, which expired in June.

According to a press report on Monday, Bechtel's most recently revised EA offer will go to a vote on August 12-14.

The revised EA reportedly needs 50% approval plus one vote from 8000 eligible employees to pass.

Bechtel previously flagged locking out employees in regards to industrial action.

It also warned the industrial action could affect workers who were not participating in it - which would be the case if cranes stopped operating.

Last week BG Group said industrial action could threaten the QCLNG project's schedule of first LNG in late 2014.