Omai plans to dump water with low-level cyanide, mercury into Essequibo River

Oct 07, 2024 News

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“Omai plans to dump water with low-level cyanide and mercury into the Essequibo River for dewatering existing open pits. Local miners will know it as “bailing out pit”, a very common practice in “land drege” operations ( a form of open pit mining)”

 

Kaieteur News- The future re-opening of Canadian mining company Omai Gold Mines Corporation operations in Guyana would require dewatering of the existing open pits. As such, the company said it would need to dump the water which contains some level of cyanide and mercury from the mining pits into the nearby Essequibo River.

Omai through its wholly owned subsidiary Avalon Gold Exploration Inc., holds a 100% interest in the Omai Prospecting License, covering some 4,590 acres or 18.575 square kilometres including the past producing Omai gold mine. Omai’s gold project encompasses two gold deposits: the shear-hosted Wenot Deposit and the adjacent intrusive-hosted Gilt Creek Deposit.

This publication recently reported that Avalon submitted an application for environmental authorisation to conduct gold mining and processing operations in Region Seven, at the confluence of the Essequibo and Seballi Rivers, Omai, Potaro Mining District 2. The project aims to sustainably extract and process gold from the area.

According to the project summary submitted to the Environmental Protection Agency (EPA), characterisation of both the pit water chemistry and the receiving water body (Essequibo River) chemistry is essential to understand any potential impacts.

Water sampling took place between November 14 and 16, 2023, to characterise the chemistry and water quality of the Wenot and Fennell pit water, and the adjacent Essequibo River, the document noted. Within those three-days, Omai said it collected a total of 86 water samples from the Wenot and Fennell pits and 26 water samples from the Essequibo River. The samples were analysed within the recommended timeframes for metals, anions, and cyanide.

 

Results from the sample of the Essequibo River showed that the majority of the samples were within established surface water quality objectives, except for three sites with minor copper exceedances, the company said.

According to Omai, the results were compared to international water quality standards such as the Canadian Council of Ministers of the Environment (CCME) and Ontario’s Provincial Water Quality Objectives (PWQO) and showed no exceedances for key contaminants like arsenic, cadmium, cyanide, copper, lead, mercury, nitrate, and sulphate.

It was highlighted that cyanide and mercury levels were below detection limits. “All cyanide data was reported below the method detection limit of 0.002 mg/L (accepted objective is 0.005 mg/L) and all mercury data was reported below the method detection limit of 0.2 ug/L (accepted objective is 0.2 ug/L),” it was stated.

“Review of all quality control (QC) data demonstrated overall good reproducibility and excellent accuracy,” the company said. Omai explained that while the CCME and PWQO guideline values have no regulatory standing in Guyana, the practices were used for comparative purposes as current best industry practice concentrations.

Overall, the company findings are that all critical parameters were well within safe limits for the protection of aquatic life. The study analyzed the water chemistry in both Omai pits (Fennell and Wenot) and the receiving Essequibo River. The results indicated that the water from the pits did not exceed any international water quality standards for the protection of aquatic life.

 

In fact, the company said that the water quality in the pits was found to be better than that of the Essequibo River in several parameters. As a result, Omai said that the discharge of water from the Wenot Pit into the river is expected to improve the Essequibo River water quality in the discharge area and downstream.

As part of the legal requirements outlined in the Environmental Protection Act, an Environmental Impact Assessment (EIA) is necessary due to the potential significant environmental effects of the proposed mining activity. The EPA said it will only decide on the approval or rejection of the project after the EIA is completed. As such, the public is invited to participate in the process by submitting questions and concerns they would like to see addressed in the EIA. These submissions must be made in writing to the EPA within 28 days of the notice issued on September 17, 2024.

Kaieteur News had reported that the results from its first Preliminary Economic Assessment (PEA) for the Wenot Project revealed that the project is slated to yield over 142,000 ounces of gold annually over a 13-year mine life. At its peak, production is anticipated to soar to 184,000 ounces in a single year, with a total estimated production of 1,840,000 ounces of payable gold.

Last month, Omai announced that it is advancing its expansion plans for its gold project in Guyana, with newly released drill results showing potential to increase gold production and extend the life of the Wenot mining pit.

The company said that the dewatering of the Wenot Pit will enhance its drilling programme.  The Wenot Pit is one of two previously mined pit on the company’s property.  It has a capacity of 42.1 million cubic meters (Mm³), with an estimated 17.8 Mm³ of tailings. The calculated net contained water is 24.3Mm3 of water or 6.4B US gallons is planned to be released from the Wenot Pit.

The company’s planned drill programme for 2024-25 will test several areas, including extensions to Wenot to the east and west.  Additional targets on the Omai property will also be drilled as some are near surface and high grade that could bolster the grade profile in the early years of a production scenario.

In 2020, Omai re-entered Guyana’s mining industry. The company had said that their work completed thus far, has put them on track to become the next large-scale gold mine to open in Guyana. Over the past three years the company said it discovered and established a new 4.3 million ounce fresh-rock gold resource.

Cyanide spill

On August 19, 1995, a man-made environmental disaster had occurred in the Omai River in Guyana; the walls of an earthen tailings pond, constructed to contain cyanide utilized in the gold-mining industry, became breached. More than 400 million gallons of cyanide-laced material spilled into the Omai River and subsequently, into the Essequibo, the country’s largest river.

The spill resulted in severe environmental, ecological, social, economic and political consequences for the Guyanese community. The local and international media, government, politicians and environmental groups were actively involved in the matter. Due to local outcry and international outrage, gold-mining operations in the region were suspended for several months.

During the crisis, former President Cheddi Jagan had declared a stretch of 50 contaminated miles of the Essequibo River as an environmental disaster zone. While concentrations of cyanide of two parts per million (ppm) are fatal, the slag along the Omai River values reached 28 ppm during that disaster.

A government-mandated Commission of Enquiry investigated the matter and made recommendations. Nevertheless, gold-mining operations resumed fully at the spill site by March of the following year. The mining company eventually shut down its operations in 2005 and its holdings passed from Cambior Resources to IAMGOLD before they made it into the hands of Mahdia Gold Corporation (MGC).

Moreover, project details are available on the EPA’s website or can be obtained from the EPA’s office. Public comments and concerns can be sent to the Environmental Assessment Board via email at [email protected].

(Omai plans to dump water with low-level cyanide, mercury into Essequibo River)

 

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• cyanide, Elaine Ellingham, Environmental Impact Assessment (EIA), mercury into Essequibo River, Omai, President of Omai

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