Peru’s ombudswoman warns government of potentially vast water contamination in Lima from mine

Peru’s ombudswoman has warned the government that the Rimac River, the most important source of potable water for Peru’s desert capital city, Lima, is threatened by possible  arsenic, lead and cadmium contamination from a mining operation upriver in the Andes.

Beatriz Merino, in an open letter to President Alan Garcia’s top Cabinet minister, contended that the failure of the San Juan S.A. Mining Company to protect its tailings dam against existing subterranean water filtration and seismic activity puts the city’s population of eight million people at risk. A major earthquake could potentially cause the contamination of Lima’s entire potable water system and shut down Peru’s central highway and railway,  she argued.

“This situation, Mr. Prime Minister, was communicated by the company to Peru’s Institute for the Supervision of Investment in Energy and Mines, or Osinergmin, on May 12 of this year, and it has progressively worsened,” Merino wrote in the letter delivered to Jorge Del Castillo on Wednesday.

“The National Civil Defense Institute, or Indeci, has issued a “high risk” warning because of the enormous probability that the tailings dam will collapse.”

The San Juan S.A. Mining Co. is located 90 kilometers east of Lima, near the town of San Mateo. The mine, which covers an area of more than 3,000 hectares, has been exploited almost continuously since Spanish colonial times, producing silver, lead zinc and smaller amounts of gold. Gold Hawk Resources Inc. purchased the mine from Gestiones y Recuperaciones de Activos S.A. in 2006 for a purchase price of $12 million.

Tailings, also known as slimes or gangue, are produced when mechanical and chemical processes are used to extract the desired product from the worthless ore and are usually stored on the surface in retaining structures such as dams.

Common materials and elements found in tailings — and, according to Merino, soon likely to be found in Lima’s potable water system — include arsenic, barite, radioactive materials, mercury, cadmium, hydrocarbons, and sometimes cyanide and sulphuric acid.

Because the situation is critical and a collapse likely to generate catastrophic consequences, the Osinergmin has ordered the suspension of the mine’s activities and the relocation of the tailings dam to a safer area.

But Merino warned that efforts are not moving fast enough and called for immediate action.

Tailings dam failures are not uncommon.

On Feb. 13, a pipeline carrying mine tailings from the San Cristobal Mine ruptured in the town of San Cristobal, in Bolivia’s department of Potosí. The pipeline carried mine tailings containing high levels of very toxic chemicals, including cyanide. Rivers were affected, causing environmental damage and water sources to be polluted.

On Nov. 6, 2006, a tailings dam failed in Zambia, releasing highly acidic tailings into the Kafue River, which caused the drinking water supply of numerous downstream communities to be shut down.

On April 30, 2006, another tailings dam failure caused a landslide that buried approximately nine households and killed 17 people. Toxic potassium cyanide was released into the Huashui River, contaminating it for approximately 5 kilometers, or 3 miles, downstream.

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