Chile issues fresh measures against Lundin Mining for giant sinkhole

Chile’s environmental regulator SMA said on Wednesday it had issued fresh measures against a copper mine owned by Lundin Mining (TSX: LUN) after detecting new leaks around a sinkhole that opened up last year near one of the company’s mines.

The huge 36-metre-diameter sinkhole that appeared in late July in the Tierra Amarilla commune, close to the Alcaparrosa mine, drew widespread global attention and saw Lundin being charged by authorities.

Together with extending six “urgent and transitory” measures that Lundin was asked to implement last year, the SMA issued four new mandatory actions, which seek to determine the reason for the lower levels in nearby aquifers.

“Based on new information provided by the company and through monitoring by the water authority, we can say there have been leaks around the Jocelyn and Gaby caves, with a flow that would have reached 80 litres per second,” the SMA said in the statement.

“These actions requested from the mining company must be carried out between 10 and 20 days, and subsequently be reported to the SMA for the corresponding analysis,” it added.

Alleged over-extraction

Chilean authorities, including the SMA superintendent Emanuel Ibarra, have said that preliminary investigations linked the sinkhole on the mine’s property to ore over extraction.

“In addition, when the event occurred, large amounts of water began to leak into the mine from places where the company intervened beyond what was considered in the environmental assessment,” Ibarra said last year.

The environmental watchdog’s previous orders are related to filling the sinkhole, sealing the adjacent tunnels, replacing groundwater, reopening the mine, protecting employment and improving the social environment.

Operations at Alcaparrosa remain suspended while the company, which has already spent around US$10 million on solving the issue, works on fulfilling all the conditions imposed.

The Toronto-based miner owns 80% of the Ojos del Salado complex, which holds two underground mines: Santos and Alcaparrosa. The remaining 20% is held by Japan’s Sumitomo Metal Mining and Sumitomo Corp.

Sinkholes are pits that form over areas where water gathers underground without external drainage, causing the water to carve out subterranean caverns.

These cavities also form regularly near old and active mines, where large amounts of rock and ore have been extracted, studies have shown.

Sinkholes often form gradually over many years, but can also open quite suddenly, taking cars, homes and streets down with them.