Long-term management

Opening into control room

The M24 wreck site is of great significance to Australia and Japan and as such must be safeguarded into the future. Since the vessel may still house the remains of the crew the site is also a lasting memorial for family members.

The Heritage Branch and the Department of Sustainability, Environment, Water, Population and Communities have adopted a non-disturbance approach to the archaeological work being carried out on the wreck, which is in accordance with Rule 1 of the UNESCO Convention on the Protection of the Underwater Cultural Heritage 2001.

Cuttlefish near conning tower hatch

Through this work, base data is being compiled on the condition of the wreck. This information will underpin the longer-term management of the site.

There will be many years of archaeological survey and analysis to obtain the necessary site data. This work will include:

  • completing the initial phase of archaeological and environmental assessment of the site
  • obtaining quantitative data on the corrosion rate of the vessel, which will help to predict the long-term survival of the wreck if left in situ
  • ongoing investigation into the nature of the unexploded ordnance
  • further survey work into any battle damage to the vessel
  • analyses of the submarine’s environment — the water quality and the effect this might have on corrosion rates and the amount of dissolved oxygen, water temperature, salinity levels, PH. They all have an effect on the corrosion rate of the wreck.
  • analysis of the sediment surrounding the wreck — the type, the density, how it inhibits oxygen penetration.
  • analysis of the marine habitat and microbial activity – the type of marine plants and algae covering the site.

Fishing nets still trapped at bow

Work being conducted on other midget submarine sites, will be useful to this analysis. The wreck of the vessel sunk by the USS Ward early in the Pearl Harbour attack is one of the most important for comparative analysis.

Already, minimal disturbance corrosion studies at this deep Pearl Harbour midget wreck estimate that after 61 years there would be a loss of 11% of the original hull thickness. Because the M24 lies in far shallower water, and a more oxygenated environment, its corrosion pattern is considered to be more active.

Dr Hans Van Tilburg, Maritime Heritage Coordinator at the NOAA/NOS in Honolulu suggests that this low impact corrosion modeling could have applications for the M24 midget submarine. Similarly, he expects that the detailed report provided by the Heritage Branch on the Sydney submarine will ‘greatly help our understanding of our site.’

Propellers at stern

In the meantime, the Heritage Branch will continue to liaise with all relevant bodies that have a management or monitoring role with the wreck site. This will include a variety of Commonwealth and State government agencies, the Japanese government, relevant heritage professionals and the next of kin of the crew.

The joint agency management and preservation framework for the Pearl Harbour midget submarine, which is overseen by the US Navy, NOAA, National Park Service and the State of Hawaii, is a similar model to the existing management of the M24.

The development of a M24 management and conservation strategy was prepared to consider such critical issues as:

  • the recovery of human remains,
  • risks from unexploded scuttling charges
  • structural integrity of the vessel
  • the ongoing survey work associated with the wreck
  • public access issues
  • public interpretation of the site.