Demonstrators opposed to the expansion of Russell Vale mine say a blockade at the site on Monday was "just the beginning" of a beefed-up protest effort.
Police moved on about 10 peaceful protesters who gathered at the colliery entryway from about 7am Monday.
The protesters spent about an hour blocking the path of arriving and departing vehicles, in an action aimed at interrupting Wollongong Coal as it prepares for a controversial expansion at the site.
Miranda Gibson, spokesperson for Stop Russell Vale Mine, said Monday's protest marked the launch of a new direct action campaign designed to halt the mine's expansion.
"Today's action has successfully demonstrated the community's opposition to this mine," she said.
"This expansion would allow extraction further into Sydney's water catchment, putting our water at risk.
"Today is just the beginning. After a decade of community opposition to this mine, we are launching a new direct action campaign.
"We are committed to taking action until Wollongong Coal cease their plans to extract more coal from our water catchment."
Wollongong Coal gained approval for its mine extension at Russell Vale in December last year, capping off a more than decade-long effort by the company.
Wollongong Coal plans to extract 3.7 million tonnes of coal from under the Greater Sydney water catchment over the next five years.
Opponents say the expansion poses a risk to the drinking water supply of more than five million NSW residents, and that it will contribute an extra 11 million tonnes of greenhouse gas emissions.
"This issue impacts local communities, with the mine set to add up to 34 coal trucks per hour onto our residential roads, increasing pollution and noise," said Ms Gibson.
"Our community and water catchment will pay the price while this coal is exported for the profit of Wollongong Coal's parent company in India, Jindall Steel and Power, who now own 98.6 per cent of the shares."