Enlargement of Lyttelton Harbour, New Zeeland

Abstract

Lyttleton Port Authority has drawn up a project for the reform and construction of new wharves and breakwaters, to cater for the increasing sea traffic. The cost of the project is 4.5 million pounds. The main work consists of a 1,070 m long front wharf, built in deep water, and apt for use by large ships. The structure of the wharf consists of a filled in zone, taken from the sea, along the edge of which a row of piles has been arranged, to support the wharf itself. This has been made with hard Australian timber. But the platform over the filled in zone is built with soft local timber. The hills rising along the coastline have been traversed by two tunnels: one for the roadway and the other to take the railway. These communication lines, which save 11 km, will link the harbour with Christchurch, the most important city in South Island. The bottom, where the wharf has been made, was soft mud, awkward to contain and control. To overcome this difficulty a simple and ingenious method was adopted. Loads of stone, from nearby quarry residues, were thrown into the mud. The stones pushed out the mud in the manner of a wavefront. The mud was then dredged away, and the stone filling operation was continued. Stone had to be used as there was insufficient sand in the neighbourhood.