With the Australian Anglesea Outfall Replacement Project time was the critical factor: in August 2015 a collapsing cliff damaged the sea outfall pipe of the local water treatment plant on the coast of the Bass Strait. A new pipeline had to be installed promptly and before the start of the Christmas holidays, when demand on the plant is at its peak due to the many tourists.
In order to meet the strict conservation conditions, a Herrenknecht HK250C HDD Rig was used for the drilling. Starting from the treatment plant, first a pilot hole was created under the seabed, which was sealed on the seabed after reaching the required 700 meters. In a second step the drilling contractor was thus able to ream the pilot hole from the rig side as well, without escaping drill fluids or cuttings affecting the nearby Point Addis Marine National Park.
By November 2015 drilling had been completed already and the pipeline could be installed. For this a vessel towed the 700 meter long prefabricated pipe string out to sea from the beach. The task required careful planning, as the installation of the new pipeline was done directly outside the entrance to Port Phillip Bay, Australia's busiest cargo port. With the help of the HDD Rig the 14" pipeline (Ø 335mm) was pulled through the predrilled alignment as far as the treatment plant and connected there. Barely 3 months after the damaging of the old pipe the new outfall pipeline was put into service.
