China’s environment ministry said on Monday that a tailings breach last month at the country’s largest molybdenum mine was the worse environmental disaster in almost 20 years.

The spillage on March 28 at Yichun Luming’s tailings storage in the northeastern province of Heilongjiang sent 2.53 million cubic metres of mining waste into the local river system, reviving fears over the safety of ponds used for tailings.

The waste reached as far as 110 km (68.35 miles) southwest of the mining site, where the chemical oxygen demand reading (DOC) — a measure of water quality — was 5.7 times higher than standard levels, Reuters reported.

While there were no casualties, China’s Ministry of Emergency Management and the Ministry of Ecology and Environment pledged on Friday to conduct centralized investigations of hidden risks at tailings dams.

The inspections, they said in a joint videoconference, will focus on facilities close to residential areas, out of service for an extended time, or likely to cause major environmental pollution along the Yangtze and Yellow Rivers.

A 2018 assessment of the site by the Chinese Ministry of Emergency Management concluded that the company and its tailings storage “had serious potential safety risks.” The mine had already been fined at least twice for concerns related to tailings management.

Tailings dams have been under close scrutiny globally since last year’s tailings dam collapse at Vale’s (NYSE: VALE) Brazil Córrego do Feijão iron ore mine, which killed 270 people and contaminated nearby streams.

Until then, there was no set of universal rules defining exactly what a tailings dam is, how to build one or how to care for it after it is decommissioned.

Previous efforts to improve processes included the World Mine Tailings Failures, an online database aimed at exposing the cause of tailing dams disasters, giving direction on how to prevent them.

Only in the past year, however, have organizations and miners across the globe stepped up efforts to set global standards.

The International Council on Mining and Metals (ICMM), a London-based industry group representing 27 major mining companies, formed an independent panel of experts in charge of developing global standards for tailings facilities.

The Church of England, which invests in mining companies through its pensions for retired clergy, along with its partners, launched a global inquiry in April 2019 into the mining waste storage systems of more than 700 resources companies.

It now asks companies to disclose data on tailings dams on a regular basis.

Switzerland-based Responsible Mining Foundation (RMF) published a study in early April this year, showing that investor-led action had resulted in improved transparency regarding the state of such facilities.

The vast majority of miners, however, have yet to demonstrate they are reviewing how they effectively manage tailings-related risks.

The non-profit, funded by the Dutch and Swiss governments and some small philanthropic organizations, said that while a global standard on tailings management is a welcome initiative, it could be significantly strengthened to become significant in terms of tailings safety.

China has nearly 8,000 tailings dams, the most of any country in the world.

Fonte: MINING.COM