In May 2020, Dunstans completed a crossing under the Nerang River on the Gold Coast as part of the City of Gold Coast’s Long Term Recycled Water Release Plan. The crossing was one of the largest Horizontal Directional Drilling (HDD) crossings to be constructed in Australia.
Due to the geology, location and diameter of the borehole, the design and methodology was technically challenging and complex engineering solutions were required to successfully complete the works.
Drilling was conducted from within The Southport School, with the borehole passing under the Nerang River, Gold Coast Light Rail and Sundale Bridge and exiting at Waterways Drive, Main Beach, a distance of 900m.
Pilot holes were drilled from both sides of the crossing with an intersect undertaken below the Nerang River utilising Gyroscopic and radar guidance tools. Reaming was conducted using a two drill rig system to ensure continuity of drill pipe from entry to exit at all times during reaming operations. Reaming was conducted in only three stages with 27 inch, 42 inch and 58 inch reaming passes completed using industry leading Sharewell reamers.
A 1200mm OD PE100 HDPE pipe was welded and strung at The Spit, 5km north of the project site. For pipe insertion, the 900m of 1200mm HDPE pipe string was towed along the Nerang River and Broadwater to Waterways Drive with barges, tugs and water police. The pipe was then passed onto land where it was positioned in-line with the borehole and connected to the drill rig for insertion.