- Rivett, Norman C and Hicks, George
- Naval technology, History - WW2, Garden Island
- RAN Ships
- HMAS Lachlan
- March 2005 edition of the Naval Historical Review (all rights reserved)
The sixtieth anniversary of the official opening of the (then) largest dry dock in the Southern Hemisphere by the Governor General, HRH the Duke of Gloucester, falls on 24 March 2005. This was the largest civil engineering project undertaken in Australia to that date and it was designed to accommodate the largest warship afloat, together with the leviathan ocean liners (then troopships), RMS Queen Mary and Queen Elizabeth. The following article is reprinted from the brochure published by ADI in 1995 to commemorate the 50th anniversary of the opening of the dock. Contributed by Norman Rivett (member) and George Hicks (ADI), courtesy of ADI Ltd.
The need for a naval graving dock in Australia became crucial with the deteriorating world situation in the 1930s. There was little doubt that Australia’s security would depend upon its commercial sea lanes. The country’s ability to maintain the rate at which its naval forces could be repaired and returned to sea would play a large part in its ultimate survival.
In 1938 the Cabinet responded to this situation by approving, in principle, the construction of an Australian naval graving dock. The Australian Government approached the British Admiralty with its assessment of the requirement and asked for its assistance. As a result Sir Leopold Savile KCB, a senior principal in the British engineering firm Sir Alexander Gibb and Partners, was invited to Australia to investigate and report on the most suitable site. As a former Civil Engineer- in-Chief of the British Admiralty and responsible for the Singapore Naval Base, Savile was eminently qualified for the task. He arrived in June 1939 for a tour of every state and an inspection of 16 possible sites located within eight principal ports in southern Australia. He was to consider the strategic as well as the engineering aspects of the sites and was reminded that the dock would also need to be used for repairing large merchantmen acting as troop ships. After completing his investigation, Savile concluded that three sites would fulfil these requirements. One was at Adelaide while the other two were in Sydney Harbour. Construction of the graving dock between Garden Island and the foreshore would best fulfil all the requirements. It was already well protected, provided easy entry for the fleet, and would enhance the importance of the existing Garden Island Naval Depot. In a report dated 31 January 1940, Sir Alexander Gibbs and Partners advised the adoption of the Garden Island-Potts Point proposal.
The Prime Minister, Mr. R. G. Menzies, told the Parliament on 1 May, 1940: ‘A dry dock of a larger size than any in Australia has been an important strategic consideration since the size of capital ships has increased so greatly. I do not need to elaborate the great value to Australia of a dock capable of accommodating not only the largest warships but also merchant ships of great tonnage. The possession of such a dock would make Australia a fit base for a powerful fleet and would, in certain contingencies, enable naval operations to be conducted in Australian waters without the necessity for ships to travel 4,000 miles to Singapore for purposes of refit and repair. It is estimated that three years will be occupied in the construction of the dock. The estimated cost of the dock on the selected site is, in Australian currency, £2,997,000 compared with £3,039,000 for the other Sydney site (above the Harbour Bridge), and £3,839,000 for the Adelaide site. The Government has decided to accept the recommendation, and the work will be put in hand at the earliest possible moment.‘
On 4 July 1940 the War Cabinet decided that although the project had been the responsibility of the Department of the Navy, the construction phase should be placed under the Department for the Interior, which established a Dock Construction Section under the Assistant Commonwealth Director-General of Works, W. M. Mehaffey. Close liaison would be maintained with the Admiralty and the firm of consultants, particularly Mr. Guthrie Brown who designed the dock. In addition to the construction of the graving dock, new workshops and modern machinery would be provided on the island, together with construction of a repair wharf with a 250-ton crane.
This would be the greatest engineering feat in Australia’s history, surpassing even the Sydney Harbour Bridge. It would involve the reclamation of 30 acres between Potts Point and Garden Island and the construction of the graving dock 1,139 feet 5 inches (347.29 metres) long, 147 feet 7.5 inches (45 metres) wide and with 45 feet (13.72 metres) draught of water on sill at spring tide.
Before the work on the dock could begin, the first task was to reclaim the area between Potts Point and the southern tip of the island. Soundings taken over the area indicated that the sea bed was only 25-30 feet below mean low water springs, making some excavation necessary. Two hundred, three inch test bores taken by a diamond drill were examined which disclosed that below a layer of about five feet of silt, there was a firm foundation of sandstone. One hundred and seventy thousand feet of sheet piling and approximately 800,000 cubic yards of stone and core filling were used to form a huge coffer-dam from which the sea was pumped, leaving a large basin in which the dock would be built. The coffer-dam, known as the ‘Burma Road’, was commenced in December 1940 and completed early in February 1942. The fall of Singapore to the invading Japanese on 15 February 1942 added to the urgency of the work. The dock at Singapore was now unavailable and Cockatoo Island was engaged in the construction of new ships for the Navy. Work on the graving dock continued night and day, with additional labour being hired as the project progressed.
To provide material for the coffer-dam, the New South Wales Department of Public Works opened up a new quarry at Balls Head from which nearly 500,000 cubic yards of sandstone were taken. While the embankment was being erected, the silt overlying the area on which the concrete body of the dock was to be established was removed by dredging. Pumping of the water enclosed by the coffer-dam commenced on 17 February 1942. The average workforce was 1,750, rising to a peak of 4,125 in July 1943. It was an amazing sight, especially at night when the blaze of lights illuminating the work area contrasted with the darkened city.
Concrete was poured at a rate of 2,000 cubic yards (1,529 cubic metres) per day. This was special concrete capable of resisting the chemical action of sulphates in the seawater. Most of the plant required for the dockyard was manufactured in Britain and shipped to Australia. This was a risky undertaking, given the possibility of attack from German U-boats, bombers and Japanese submarines during the long voyage, but fortunately only two shipments were lost through enemy action.
While the dock itself was being constructed, the caissons, designed by Vickers Armstrong of Barrow-in-Furness were also being built within the area enclosed by the coffer-dam, there being no suitable launching facilities available. Their construction, by the Sydney Steel Company Pty. Ltd., was one of the most difficult undertaken in Australia up till that time; the caissons, made of welded steel, were fitted with buoyancy tanks, tidal chambers and ballast tanks designed to enable their flotation and sinking within the dock grooves as required.
The dock was ready for initial flooding in September 1944. Three 60-inch centrifugal pumps designed to discharge 70,500 gallons (320,493 litres) per minute allowed the dock to be emptied of its 57,000,000 gallons (259,122,000 litres) of water in about four hours. The construction was sufficiently advanced to allow the emergency docking of HMS Illustrious on 2 March, 1945, three weeks before the official opening ceremony.
The graving dock was named in honour of Captain James Cook, R.N and opened by the Governor-General, the Duke of Gloucester, on 24 March 1945. To mark the occasion the bow of the River Class frigate, HMAS Lachlan, broke a ribbon extended across the entrance to the Dock.