Freight link protest costs WA police $120k

West Australian police have spent $120,000 in three days for 300 officers to be at the Roe 8 highway site protests.

Police Commissioner Karl O'Callaghan said there were 100 officers at the site each day and a police spokesman confirmed the cost was about $40,000 a day.

Two women were arrested after they chained themselves to the gates of a construction company's yard on Tuesday, stalling work for several hours while specialist police freed them.

There have been weeks of protests at the controversial $1.9 billion Perth Freight Link worksite, with many people arrested and issued with move-on notices.

Mr O'Callaghan said he was not against peaceful protesters, but that police did not have many options other than intervening if people interfered with the work.

Last week, protest group Save Beeliar Wetlands lost its bid to challenge state environmental approval for the road in the High Court, and is now pursuing a legal challenge in the Federal Court over the Commonwealth environmental approval.