Alkimos Completes Its First Intake-to-Tunnel Connection

Excavation gives way to permanent connections

Water Corporation has completed the first offshore intake-to-tunnel connection at the Alkimos Seawater Desalination Plant in Western Australia. Its October project update says the construction team is excavating towards the second intake riser. The centre of the first riser was located approximately 11 metres below the seabed, 10 centimetres from its planned target. [1] The result advances a distinct part of the marine works. Tunnel excavation and installation of the offshore structures had already reached their reported milestones; the permanent connection joins those separately constructed elements into the intake system. The 10-centimetre figure describes the owner's reported position relative to the target. The update gives no directional breakdown or acceptance tolerance. [1] Both tunnel boring machines, Karli and Mary, have been dismantled, demobilised and transported off site. The slurry and water-treatment plants that supported tunnelling have also been removed. [1] Those removals reduce the onshore temporary-plant footprint while offshore excavation continues at the second riser. They also change the practical workfront: the remaining connection must be completed with the tunnel-excavation support systems already demobilised. Connection planning needs its own access, excavation and verification arrangements.

Permanent junctions join the intake system

The owner's earlier construction updates place the first connection in a longer sequence. Mary reached the intake location in May; Karli completed the outfall drive in late August. The offshore installation vessel Beverley had installed the two intake structures and outfall diffuser before departing on 28 July. Water Corporation's September announcement records completion of the intake and outfall tunnel excavation. [1, 2] The owner's marine construction fact sheet describes two intake structures, each 12 metres wide, about 1.6 kilometres offshore. The permanent tunnel junctions connect this offshore collection system to the underground seawater route. [3] The October update closes the first of the permanent intake junctions and identifies the second as the next excavation target. For programme control, recording each junction separately gives a more precise measure of remaining marine work than a single tunnel-completion percentage.