For the residents of this area north of Wollongong, which includes the environmentally sensitive areas of the Illawarra escarpment, The Royal National Park, Coalcliff and Stanwell Park coastlines and the Port Hacking waterways, the result provides a long-overdue upgrade to a sewage system designed more than a century ago.
In the five months that the crew from the operators, Akerman Apache, were based in the district the project was keenly observed by locals and judged to be an outstanding success on all fronts. Even the Helensburgh/Stanwell Park Surf Life Saving Club benefited – to the tune of a fully equipped Inflatable Rescue Boat donated by Akerman Apache – as a thank you for the overwhelming public support for the project.
The operation, a joint venture between the Oklahoma-based Akerman Construction Inc and Australian-owned Apache Earthworks Pty Ltd, involved a low-pressure system totalling 6,500 metres of reticulation and 6,746 metres of transfer mains in all ground conditions.
The rig used was a track-mounted American Augers 220 with a Basic 1000 gpm mud-recycling unit. The HDD rigs ranged in size from 24,000 pounds of pullback to 220,000 pounds of pullback.
The longest bore was from Stanwell Park to Otford, a length of 1,740 metres. This accommodated a 225 mm polyethylene pipe with a 50 mm wall thickness, with a weight of 46 tonnes. It took 4,500 man-hours to complete the bore with no injuries to any personnel.
Within the first 350 metres of the bore, a 52-degree compound curve was made before straightening out to complete the 1,740 metre shot. 1,000 metres into the pilot bore, an underground aquifer was drilled through to create 80,000 litres of water per day. This required large frac tanks to be mobilised, with waste fluid removed on a regular basis. Akerman Apache instituted constant round-the-clock monitoring to safeguard against any environmental incident. In total 1.6 million litres of fluid was removed from the site during the pilot and reaming process.
To accurately locate the position of the bore at all times, a True Tracker with a Tensor steering tool was employed. This system was operated by running a wire coil (located within a historical rail tunnel adjacent to the route) to allow communication with the drill head.
An expert steering tool hand was employed from Texas who monitored the progress of the pilot bore and exited just 500 mm from the target stake. The pilot hole was then reamed to 400 mm diameter for the length of the bore using a straight mud motor and push reaming method. Ground conditions were variable strength Sydney Sandstones for the full length of the bore.
Sydney Water believe the bore to be the second longest in the world for this size pipe.
Construction Manager of Akerman Apache, John Herbert, said, “The (Northern Towns) project meant overcoming natural obstacles such as rivers and swamps, as well as man-made considerations like roads and existing installations, while closely observing regulations and environmental issues. It was quite a challenge but I can happily say that every goal we set ourselves was achieved or surpassed.”