Barrier Wall at Island Copper Mine
Since 1995 when the Island Copper Mine closed, reclamation activities and environmental monitoring of the site has been ongoing. During routine environmental monitoring near the south waste rock dump (South Dump) metals contaminated groundwater was discovered to be seeping from the waste rock dump into the marine environment. A barrier wall system was required to collect seepage for treatment, while preventing infiltration of seawater to the collection system. The system needed to be non-corrosive, environmentally sound, and cost-effective.
BHP Billiton retained EBA Engineering Consultants Ltd to design and supervise the construction of this South Dump Seepage Collection System, with Wolf Remediation Ltd supplying the sheet pile.
The system consists of two components; a vinyl sheet pile barrier wall to block shallow seepage and seawater infiltration, and a ditch at mean sea level to collect the contaminated seepage and maintain low gradients across the sheet pile wall. Wolf Remediation Ltd supplied and directed the installation of the vinyl sheet barrier wall for the South Dump Seepage Collection System.
The South Dump Seepage Collector prevents seepage with dissolved metals from entering the marine environment. The system provides maximum reliability, performance and design life, while minimizing long-term operation and maintenance costs. The South Dump Seepage collector is a key component of the ongoing reclamation work that BHP Billiton has undertaken at the Island Copper Mine.
“The design of the South Dump Seepage Collection system by EBA Engineering Ltd involved the use of an innovative sheet pile cut-off wall made of vinyl. A total of 822 sheet piles, with an approximate length of 12m, were vibrated into the ground to create a 500m long low permeability barrier that would prevent seawater intrusion into an adjacent up-gradient ditch. The sheet piles would also resist seawater corrosion leading to longevity. The ditch invert design was near sea level, so that acidic seepage from the South Dump could be collected and pumped to the Pit Lake for treatment. The design of the vinyl sheet piles cut-off wall consisted of interlocking sheet piles and a hydrophilic string sealant that would limit hydraulic conductivity. The performance of the sheet piles cut-off wall has been simple to verify, in that there has been no seawater intrusion into the up-gradient ditch. The success of this low permeability cut-off wall installation has led the way for vinyl sheet walls to be an acceptable method in the engineering field for remediation.”
M.E. Wen, Rescan Environmental Services Ltd, Canada
Wolf Remediation Ltd composite sheet pile solutions offer an alternative to conventional materials and have a wide range of uses. With a high strength to low weight ratio, composite sheet piling affords easier handling, more economical shipping, lower maintenance on installation, and a longer life-span. An environmentally sensitive solution with no compromise.