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Planning the excavation
The excavation was carefully planned to consider the prevailing south-westerly swell that moved along the axis of the site, heading north towards the reef. The excavation began at the stern area where the deeper water made it easier to work. The inshore bow area was shallower, more turbulent and suitable for diving less often.
The cluster of anchors and cannon in the middle of the site stabilised sand cover and associated buried materials in this area, so it was decided this would be the northern-most limit of the stern excavation.
Diving operations
Divers used a ‘hookah’ system of surface supplied air running through hoses, providing them with an unlimited supply of air for shallow water diving operations. During suitable weather conditions, the Museum’s workboat was attached to
permanent moorings installed on the seabed. Large capacity air compressors were used to operate airlifts and air-powered tools. The workboat used a winch and hydraulic A-frame to raise heavy items onto the deck.
Large waves break over the Batavia wreck site and onto the WA Museum’s work boat, Henrietta. The force of the impact smashed the windows.
Credit: WA Museum, BTB_637, BTB_638
RAISING THE SHIP
Diver excavating the Batavia wreck site with airlift, 1973. Airlifts pump compressed air down a hose to exit into the lower end of a length of PVC pipe. Buoyed upright in the water column and anchored to the seabed, the working end is held by a diver. As air flows, the expanding air bubbles cause the pipe to draw up water and create suction at the working end.
Moving the airlift head closer to or further away from sediments, controls the amount of suction to gently expose buried artefacts.
Credit: WA Museum, BTA_170z
