Atlas of Contaminated Sites

Notable case, Omai, fiume Essequibo, Guyana

Omai gold mine (1995 cyanide spill)

On 19 August 1995 the tailings dam of the Omai gold mine, then the largest in the Guiana Shield, failed through internal erosion: 4.2 million m³ of cyanide-bearing slurry ran into the Essequibo, Guyana's main river.

Status
Not addressed
Activity
1993–2005
Media
surface water, sediment, living organisms
Kind of site
mining, accident
  1. Area. Eighty kilometres of the Essequibo River were declared an environmental disaster zone (WISE Uranium Project).

Contaminants

Other inorganics

Status

Not addressed

The alert on the river was lifted after one week and the mine resumed production after some months, until 2005. The sources consulted describe neither a cleanup nor later monitoring; according to Wikipedia, seven years on the Indigenous villages along the river were still using alternative water sources.

Story

At Omai, near the west bank of the Essequibo, gold has been sought since at least the 1880s. The industrial mine was developed by Canada's Cambior (65%) with the US company Golden Star Resources (30%) and the government of Guyana; its two open pits, Fennell and Wenot, were worked from 1993 to 2005 and produced 3.7 million ounces of gold (Wikipedia).

In May 1995 a first, smaller spill of sodium cyanide killed hundreds of fish. On 19 August the tailings dam failed through internal erosion and released 4.2 million m³ of cyanide-bearing slurry, which reached the Essequibo. Eighty kilometres of river were declared an environmental disaster zone and production stopped for some months during the inquiry (WISE Uranium Project; Wikipedia).

The alert was lifted after one week. The accident remains one of the reference cases in the international record of tailings dam failures.

Timeline

  1. 1993Mining of the Fennell and Wenot pits begins.
  2. 1995May: a first sodium cyanide spill kills hundreds of fish. 19 August: the tailings dam fails, 4.2 million m³ into the river.
  3. 2005Mining ends.

From the literature

Species that acted on one of this site's contaminants in at least one study. The list is automatic and takes no account of this site's soil, concentrations or climate.

Fungi

Sources

  1. Chronology of major tailings dam failures (voce Omai, 19 agosto 1995), WISE Uranium Project
  2. Omai Mine, Wikipedia (en), 2026

Draft compiled from public sources, not yet reviewed.