HAKK Demolition and Remediation

Summary

Following the completion of smelting activities in September 2012, Hydro Aluminium announced the formal closure of the smelter and commenced the demolition and remediation of the smelter area.

Daracon constructed an Engineered Containment Cell (ECC) with relocating and placing contaminated waste materials from the site into the ECC, for the long term storage of materials. This enabled the zoning and development of the project site for significant employment, residential, rural and biodiversity conservation purposes.

Scope of Works

• Relocation of existing stockpiles (~ 60,000m3) within containment cell footprint;
• Clearing of existing tree’s and vegetation;
• Bulk excavation (~70,000m3) of containment cell and stockpile of surplus materials onsite,
• Cut to fill earthworks (~25,000m3) to form containment cell;
• Cut to fill earthworks (~15,000m3) to form 3 x Sediment Basins and 2 x Leachate storage dams;
• Construction of permanent quad cell culvert creek crossing including erosion and sediment control management;
• Rip and re-compact containment cell subgrade to a depth of 300mm (~ 36,000m2);
• Installation of Base Liner system ~36,000m2 including the following:

- Geocomposite layer

- Geosynthetic clay liner

- 2mm HDPE Geomembrane

- 300mm sand drainage layer (~ 11,000t)

- Drainage Geocomposite

- Geosynthetic clay liner

- 2mm HDPE Geomembrane

- Geotextile

- 300mm drainage aggregate layer (~ 16,000t)

- Geotextile

- Geomembrane

• Installation of leachate transfer system including collection sumps and pipe risers;
• Establishment, continuous operation and maintenance of temporary water treatment plant to treat leachate generated within containment cell and discharge following successful treatment;
• Load, haul and place contaminated waste materials (~ 600,000t) within containment cell;
• Handle and add Gypsum by weight to each load of contaminated waste prior to placement within containment cell;
• Placement of Capping Layer system ~ 35,000m2 including the following:

- Geonet drainage composite

- 300mm select fill sealing layer (~ 23,000t)

- Geosynthetic clay liner 

- LLDPE Geomembrane

- Protection Geotextile

- 300mm drainage aggregate layer (~ 20,000t)

- Separation Geotextile

- 1.3m thick subsoil layer (~ 110,000t)

- 100mm topsoil layer (~ 5,000m3)

- Hydromulch revegetation layer (~ 5,000m3)

• Installation of gas management system; and
• Removal of all temporary works and reinstatement of affected landform including Leachate storage dams.