Kendal Blust/KJZZ

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

Mexican authorities have confirmed widespread heavy metal contamination in wells in the Sonora River Valley. Residents in the region have been redress for more than six years, since a 2014 mining spill considered the worst in Mexico's history.

Mexico's Commission for Protection Against Sanitary Risks (Cofepris) said in a letter this month that about 99% of wells tested in the Rio Sonora valley contain concentrations of arsenic, lead and other heavy metals that exceed Mexico’s safety standards, and pose a serious health risk.

For more than six years, residents of communities downstream from Grupo Mexico’s Buenavista copper mine have pushed the government to ensure the water they use in their homes, for agricultural purposes and livestock is safe.

"What other tests could they need at this point," said Gloria Simpson, a resident of the town of Bacanuchi and a member of the Sonora River Basin Committees that have been pushing for change. "We're at the point now where we want them to give us a solution."

She said it's past time for the Mexican government to take clear action with concrete deadlines to provide the community with clean water. River valley communities want contaminated wells closed, new ones opened and water treatment plants installed, and they want to be part of the decision-making process.

The committees formed after Grupo Mexico's Buenavista copper mine spilled 11 million gallons of toxic waste into the Sonora and Bacanuchi rivers, impacting more than 20,000 people in the region. Since then, they've been in a legal battel with environmental regulators and the mining company.

In a statement Thursday, Grupo Mexico denied any connection between water contamination and it’s mining activities, saying heavy metals have been present in the water in this region for millions of years. The company also claims it completed clean-up efforts of millions of gallons of copper sulfate acid solution in the Sonora and Bacanuchi rivers and surrounding areas within months of the 2014 spill.

Simpson, however, said that claim is a slap in the face to residents of the area.

"It's like they are laughing at us," she said. "This is an injustice that is slowly killing us, and they just want to wash their hands of it."