In-situ preservation of shipwrecks
Article | Updated 12 months ago
Conservation scientists and conservators at the Western Australian Museum conduct research to develop new and improved techniques for ensuring the long-term preservation of our underwater cultural heritage sites. This article focuses on the unique conservation methods applied to the James Matthews shipwreck site.
The James Matthews, an ex-slaver turned colonial trader, was wrecked in 1841 in Cockburn Sound, Western Australia, on its way from Britain to the Swan River colony. The site was first discovered in the early 1970s by the vocational diving association, the Underwater Explorers Club. Subsequently the site was fully excavated under the supervision of Graeme Henderson, former curator of the Western Australian Maritime Museum. Over five summers archaeologists excavated, documented, recovered associated artefacts and then reburied each section of the remaining hull structure in order to preserve the shipwreck.
Conditions often exist in underwater environments that favour the long-term in situ preservation of archaeological remains. However, increasingly archaeologists are opting for on-site examination, reinterment and in-situ preservation of underwater cultural heritage sites as the first option in the management of sites at risk as opposed to the more traditional excavation, recovery, conservation, display, and storage methods.
The wreck site remained stable for many years until in early 2000, a survey led by Dr Mack McCarthy, curator in the Maritime Archaeology Department, indicated that sand was moving away from the site, exposing large sections of the James Matthews’ structural timbers to degradation by marine worms. Over the next few years, conservation scientist Vicki Richards from the Materials Conservation Department undertook a series of on-site experiments to assess the efficiency of different in-situ preservation techniques. These tests included the use of sand bags, sediment trapping experiments using artificial seagrass and shade cloth mats and a cofferdam consisting of four environmentally inert ‘road crash barrier’ units arranged in a square formation, filled with sediment. After several years of accumulated data it appeared that the crash barrier cofferdam technique was the best solution to preserve the James Matthews in situ.
In November 2013 the large-scale reburial of the James Matthews wreck site commenced utilising funding from an Australian Research Council Linkage Grant. Over five days the archaeologists filled 1400 sand bags with 20kg of clean, washed proprietary sand equivalent to 28 tonne, deployed 36 road crash barriers in a semi-elliptical arrangement surrounding the wreck, emptied the sand from the bags into a purpose-built barge and then dumped the sterile sand directly onto the site.
As the wreck site cannot be re-excavated to assess the success of the reburial technique and the effect it has had on the actual shipwreck material, a number of sacrificial modern samples, such as wood blocks and metal coupons, were also reburied. These sacrificial samples are then recovered from the site at regular intervals and analysed so scientists can extrapolate to the condition of the reburied shipwreck material as the initial extents of degradation of the wreck before the reburial process commenced had been previously established.
This innovative in-situ preservation technique has not been applied to a shipwreck before and is therefore a world first for the Western Australian Museum. This work will be critical to the future development of national policy, methodology and technical guidelines for in-situ preservation and management of endangered historic shipwrecks.
Find out more information about the reburial of the site, the history, construction and excavation of the James Matthews, and on the many items that archaeologists recovered from the wreck site.
The Western Australian Museum also created a documented database that contains information and details on over 1650 Western Australian shipwrecks recorded by the Western Australian Museum.