GFWAust were responsible for constructing a grout curtain 350m long along the south eatern rim of Pit #1

Located about 250 kilometres east of Darwin, mining of Ranger Pit # 1 commenced in May 1980 using the open-cut method. Pit # 1 was mined out in December 1994 and is now a part of the mines on site storage for process water. Located in the World Heritage Listed Kakadu National Park, ERA has been recognised for its World Class Environment Management System, achieving International Environmental Standard ISO 14001 certification in December 2003. As part of this environmental control GFWAust were appointed to construct a grout curtain 350m long along the south eastern rim of Pit # 1 to ensure that the stored process water was unable to escape into the surrounding area.

The grout curtain consisted of a double row of grout holes through the placed compacted laterite soil and clay barrier to a depth of up to 40m into the weathered mica schist bed rock using down-stage grouting techniques. Grouting was carried out using microfine grouts with microsilica to ensure excellent penetration into the rockmass and to provide longterm performance of the grout curtain.

Due to the potential increase in flood levels in the pit, the grouting crew, equipment and materials were mobilized within 10 days to the site. With day time temperatures in excess of 40o C, to avoid premature setting of the grout the work was carried out during the cooler nightshifts. Together with competing with the difficult logistics of carrying out construction on a remote mine site, GFWAust also provided technical support to determine the grouting needs and achieve the final required result.