Restoration of Benambra Mine

Sunday, 25 March, 2007

The sudden closure of Benambra Mine in East Gippsland, Victoria in 1998 left the area in desperate need of environmental restoration. Abandoned buildings, equipment and other materials led to heavily chemical-laden water in the tailing dams.

Benambra operated as a base metals mine between 1992 and 1996 before its operator, Denehurst Limited, went into administration. Due to Benambra's sudden closure, mining operations ceased without post-mining works required to restore the environment.

The mine has since been under the care and maintenance of administrator, PricewaterhouseCoopers and the Department of Primary Industries (DPI). Abigroup Contractors were awarded the project to complete closure works on the mine.

The two major issues needing rectification were the strengthening of the dam wall and the minimisation of heavily chemical-laden water from the tailings dam running into the Tambo River, which flows into the Gippsland Lakes.

All Stakes Supply came to the rescue with a proposal using its organic jute matting. It suggested that some 37,000 square metres of matting be sewn together to cover the tailings dam floor, capturing the lime used to neutralise the highly acidic sediment.

Abigroup Contractors agreed to employ the solution proposed by All Stake Supply, not only because of the company's horticultural expertise, but because the company had a detailed and strategic plan which offered competitive pricing on the product.

The Benambra project was the first time organic jute matting was used on such a large scale or for such a purpose. To minimise concern surrounding this issue, Stephen Jarret from All Stake Supply travelled to Victoria to inspect the site and advise on the direction they should take.

Sewing the matting together proved to be the best option in terms of finances and logistics. The method significantly minimised the amount of product used and in turn saved Abigroup up to 30% in costing.

"There were four major challenges that we had to face with this project," said Jarret. "The product was not being used for its intended purpose, trying to find a way to stitch the matting together, the limited time frame that we had and the remoteness of the Benambra site."

Jarret advised Abigroup that the best option for sewing the matting together was to use handheld bag-closing machines. The machines were ordered from India and used manually by the team to sew the large sheets together.

Despite the fact that the matting had to be imported and usually takes a minimum of six weeks to arrive, All Stake Supply was able to deliver a total of 60% of the matting within the four-week deadline. Moreover, the company sourced the other 40% of the product from another vendor to complete the project.

Once stitched, the organic jute matting was re-rolled for deployment from the barge. As it was deployed, the jute initially floated then slowly sunk over several days, allowing it to be placed accurately in a controlled manner on the dam floor, thus containing the highly acidic sediment.

Recent progress at the Benambra site shows that the organic jute matting has successfully contained the lime used to neutralise the highly acidic sediment in the tailings dam. Furthermore, the matting has exceeded expectations and is encouraging new growth and development in the area.

"The matting has now started to break up and create an organic layer that is encouraging new life and the development of a new ecosystem," said Jarret.

"Not only has the environmental hazard been eliminated, but the surrounding environment is also reaping the rewards with the return of natural flora and fauna."

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