HMVS Cerberus Conservation Management Plan September 2002 Prepared by Ross Anderson Maritime Heritage Unit Heritage Victoria CONTENTS Acknowledgements 1.0 Introduction 1.1 Scope of Conservation Management Plan 2.0 Definition of the site 2.1 Position of the Cerberus 2.2 Area of the rectangular Protected Zone 3.0 Statement of cultural heritage significance 3.1 International 3.2 National 3.3 State 3.4 Local 3.5 Aesthetic 3.6 Archaeological 3.7 Historical 3.8 Technical 3.9 Scientific 3.10 Recreational 3.11 Ability to demonstrate 4.0 Elements of historic fabric 4.1 Deck and turrets 4.2 Collapsed hull 4.3 Buried hull 5.0 Conservation policy 5.1 Conservation options 5.1.1 Managed collapse and cathodic protection 5.1.2 Removal of deck to a land-based display and more stable environment 5.1.3 Stabilisation of deck in-situ with supporting structure 5.2 Conservation of elements 5.2.1 Guns and turrets 5.2.2 Hull 5.2.2.1 Intrusive materials 5.2.2.2 Destructive works 5.2.3 Buried hull 5.2.4 Timber deck 5.2.4.1 Maintenance 5.2.4.2 Removal 5.3 Support substructure 5.4 Risks, public access and risk management 5.4.1 Assessment of risk 5.4.2 Public access 5.4.3 Risk management 5.5 Flexibility of conservation policy 6.0 Care of Fabric and Maintenance 7.0 Documentation 8.0 Planning and management structure for future work and maintenance 8.1 ‘Save the Cerberus Alliance’ committee members 8.2 Historic Shipwrecks Advisory Committee (HSAC) and Heritage Council 9.0 Bibliography Acknowledgements Many people have assisted with their comments toward the final version of this document. Thank you to my Heritage Victoria work colleagues Peter Harvey, Cassandra Philippou, Ray Tonkin and Sue Balderstone. Also to members of the Victorian Heritage Council’s Historic Shipwrecks Advisory Committee, the Save the Cerberus Alliance, the National Trust’s Industrial Heritage committee, Dr Mike McCarthy and Dr Ian McLeod of the Western Australian Museum, and Ray Tyshing from GHD Engineers. I would also like to acknowledge the efforts of all those who have campaigned for the stabilisation, restoration and recognition of the Cerberus over the years. Cover photographs: VR insignia on muzzle loading gun in aft turret (Heritage Victoria) Queen's Birthday on Board HMVS Cerberus: Man & Arm Ship (State Library of Victoria) 1.0 Introduction On 26 December 1993 the intact buoyant hull of the HMVS Cerberus shipwreck built in 1867, scuttled in Half Moon Bay since 1926, catastrophically collapsed in a south-westerly storm. The collapse is recorded on video taken by Black Rock Yacht Club members filming the ferocity of the storm from their clubhouse. A subsequent major collapse occurred in November 1994. Such a catastrophic collapse, rather than gradual deterioration, had been anticipated for at least half a century (Effenberger, 1995: 16). Prior to this collapse, community support for schemes to ‘Save the Cerberus’ by refloating it and towing it to a berth in Williamstown or next to the Polly Woodside, relied on the buoyant hull of the Cerberus being repairable and restorable. A survey commissioned by the National Trust in 1969 however found that the hull was structurally too corroded to support the weight of the Cerberus (Effenberger, 1995: 9). Ultimately any thought of pursuing this preferred course of conservation/ restoration was rendered impossible by the 1993 collapse (Colquhoun, 1994: 1). In 1970 Prince Phillip revived interest in the Cerberus with a letter of support for its historic status and preservation. Following this the Cerberus Preservation Trust, later the Maritime Trust of Australia, was formed in 1971. This organisation was unsuccessful in its bid to reach a target of $500,000 in a public appeal to salvage the Cerberus and tow it to Duke and Orrs dry dock. Efforts to secure $3.5 million in federal government funding in 1985 and corporate funding from BHP in the 1988 were also unsuccessful (Effenberger, 1995: 9). Notably all public and community funding proposals to preserve the Cerberus have budgeted for public access with museums, walkways and site interpretation. Suggested conservation options for the HMVS Cerberus shipwreck post-collapse of the hull have included filling the hull with sand, concrete or foam, building a cofferdam around the site to create a ‘Cerberus Island’ and raising and stabilising the intact deck, turrets and guns with a supporting framework. The next major stage in the collapse of the Cerberus is predicted to be the breaking up of the deck as it is further stressed and hinged out of alignment by the weight of the armour, turrets and guns, without the even support previously provided by the buoyant hull (Colquhoun 1994: 2; MacLeod 1999). In a wreck inspection by the MHU in April 1999 the stem-post was observed to have split, indicating the Cerberus is entering into this final stage of collapse. The unique structure of the Cerberus can be described as a tank mounted on a barge. The ‘tank’ consists of 1800 tons of 8-9 inch thick armoured deck, breastwork, turrets and guns, that have predictably ‘squashed’ the lightly built, 300 ton, corroded hull of the ‘barge’. As the technical, aesthetic and historic significance (see 3.0 below) of the Cerberus is primarily the substantially intact ‘tank’, post-collapse efforts to preserve the Cerberus have focussed on supporting and conserving the intact deck in-situ (see Strachan, 1995). In the 1990s community lobbying by individuals and members of the National Trust, World Ship Society, Maritime Museums of Victoria, Historic Shipwrecks Advisory Committee, Maritime Archaeology Association of Victoria and the ‘Save the Cerberus’ group have ensured that the Cerberus does not sink beneath the waves as a heritage issue. The Australian and international conservation and maritime archaeological community has also offered support to encourage any efforts to stabilise and conserve the historic fabric of the Cerberus (McLeod, Dr. Ian, 2002, pers. comm., Broadwater, John, Curator USS Monitor National Marine Sanctuary, pers. comm. 2000; Gould, Prof. Richard, pers. comm., 2002). Additionally the recognition of iron and steam shipwrecks in Australia as an archaeological resource with historic, industrial and technical values has gained momentum since 1985 when Australia’s first ‘Iron Ships and Steam Shipwreck Archaeology’ conference was held in Fremantle, Western Australia (McCarthy, Ed., 1988). For this site type Victoria is fortunate to have the first screw steamship to cross the Pacific Ocean and first screw steamer to travel between Sydney and Melbourne (SS Conside (1852)), the first ship to travel directly from Belfast, Ireland to Melbourne (SS Ant (1862)) the first American steamship to cross the Pacific Ocean (SS Monumental City (1853)), Australia’s earliest located steamship (PS Clonmel (1841)) and the world’s only remaining twin turret breastwork Monitor (HMVS Cerberus (1867-1926)). Since 1994 the MHU has commissioned an HMVS Cerberus Archive Directory (Effenberger, 1995), corrosion and ultra-sound surveys (McLeod, 1994; 1999) and an appraisal of cathodic protection options (McLeod, 1999). A Cerberus Project Team was set up and a Conservation Plan project progress report with corrosion survey report, transitional conservation policy, recommendations, material costings on immediate actions required with costing estimates for other long term actions was prepared (Strachan, 1995). In May 2000 Heritage Victoria let selective tenders for engineering advice as to the practicality of raising and stabilising the intact deck, armoured breastwork and turrets to its pre-collapse level. The successful tenderer Gutteridge Haskins Davey (GHD) provided a methodology that met the conservation aims of stabilising the deck of the Cerberus. GHD advised the next step was to conduct an engineering parameters survey to determine the structural strength of the Cerberus structure, and geological survey of surrounding seabed for calculations of piling required for the jacking process. 1.1 Scope of Conservation Management Plan This aim of this CMP is to investigate the significance of the structure in its current form, and to clearly state the components of the structure that must be retained. This will be done in accordance with the Burra Charter (1999), the accepted standard guidelines for the management of sites of European cultural heritage significance in Australia. All definitions are in accordance with those as defined in the Burra Charter. The CMP has also been produced to complement a proposed action plan, to guide engineering parameter surveys and possible major engineering works to be undertaken on the site of the HMVS Cerberus shipwreck. These works are intended to investigate a) the feasibility of stabilising the site and b) support the deck structure sufficiently to prevent further collapse. The proposed works involve piling, jacking, destructive testing and intrusion of modern materials. Following the testing phase, and subject to funding, further proposed engineering works will involve the installation of a support structure on the site to raise the Cerberus to its pre-collapse level. The CMP also discusses options for conservation management of the site. 2.0 Definition of site 2.1 Position of the Cerberus Latitude South 37 degrees 58.1’ Longitude East 144 degrees 0.4’ (Victoria Government Gazette, 6 October 1994 p. 2684) 2.2 Area of the rectangular Protected Zone Approximately 0.5 hectare, with longer sides parallel to the length of the Cerberus and at a distance of 25 metres from the longitudinal centreline of the vessel, and the shorter side 5 metres to seaward from the peak of the bow and stern respectively. (Victoria Government Gazette, 6 October 1994 p. 2684) The perimeter of the Protected Zone is marked by floating tethered buoys surrounding the wrecksite, clearly marked with the words ‘Protected Zone’ and ‘No Entry’.