Kendal Blust/KJZZ

The Rio Sonora flows through the town of Baviácora, Sonora, on July 30, 2019.

Residents of the Rio Sonora valley are concerned about a major new tailings dam at a mine upstream. In 2014, a spill there caused what is considered the worst environmental disaster in Mexican mining history.

The new tailings pond at the Grupo Mexico’s Buenavista copper mine can store thousands of times more waste than one that caused the 2014 spill. And that has residents downstream concerned about the risk of another disaster.

"That's the fear, that what happened in 2014 will happen again," said Alicia Miranda, a spokesperson for the Rio Sonora Watershed Committees, which started the petition asking for support to require additional safety measures at the new tailings dam.

Mexico’s environmental ministry initially ordered the added safeguards after Mexico’s Supreme Court found the mining company had violated the community’s rights by failing to inform and consult them about the project.

A federal magistrate later ruled that Grupo Mexico was not obligated to implement the changes, but members of the community are seeking support to have that ruling overturned.