CONSERVING THE SYDNEY HARBOUR BRIDGE ARCH MAINTENANCE UNITS

16th Engineering Heritage Australia Conference Hobart November 2011 1

CONSERVING THE SYDNEY HARBOUR BRIDGE ARCH MAINTENANCE UNITS

David West1, Karina Acton

2, Rachael Crompton

3, Eleanor Sampaga

4, Fiona Treadgold

5

1 Executive Director, International Conservation Services Pty Ltd, Sydney

2 Senior Objects Conservator, International Conservation Services Pty Ltd, Sydney

3 Project Manager, International Conservation Services Pty Ltd, Sydney

4 Conservation Consultant, International Conservation Services Pty Ltd, Sydney

5 Principal Collections Manager, International Conservation Services Pty Ltd, Sydney

ABSTRACT

The original Sydney Harbour Bridge Arch Maintenance Units (AMU) are engineering marvels inextricably bound to a national icon. Yet following decommissioning from the Bridge in 1997, they were neglected, and by 2005, were in poor condition. This paper discusses the process of conserving the AMUs, and the various challenges, constraints and opportunities encountered. Identification of the appropriate conservation approach and methodology was guided by the requirements of the various stakeholders, who included the client, communities and large collecting institutions. In addition to these factors, the approach was affected by the need to consider statutory requirements for the treatment of significant items, the retention of materials considered hazardous, and the challenges in lifting, transport and storage for a large-scale industrial movable heritage item.

1 INTRODUCTION

The four Arch Maintenance Units (AMUs) were already a constant feature on the structure of the Sydney Harbour Bridge well before its completion in the early 1930s. Although they were not fixed parts of the Bridge itself, fixed and unchanging, they were objects completely unique to the Bridge, an iconic national landmark. They were designed and constructed specifically for use on the Sydney Harbour Bridge, and employed in the various painting and maintenance tasks required for its upkeep.

As is common for industrial equipment, all four AMUs were decommissioned and replaced with new maintenance cranes in 1997, as a result of the changing requirements in OHS legislation, advancing technologies, and the Bridge‟s integration into the bourgeoning tourism industry. The AMUs were stored in various outdoor depots where their condition inevitably deteriorated until 2006 when their significance was once again illuminated, this time by the compilation of a Movable Heritage Database, commissioned by the NSW Roads and Traffic Authority (RTA) and prepared by International Conservation Services (ICS). After almost a decade of neglect, a move was made towards the preservation of these significance items.

Discussions between the stakeholders and heritage specialists identified that the ideal future for these items was either as an outdoor public display item, preferably with a continued association with the Bridge, and/or in the care of a collecting institution with a known focus for engineering and industrial history. The conservation approaches were formulated around these goals.

2 THE ‘MAINTENANCE CRANES’

2.1 HISTORY AND SIGNIFICANCE

The AMUs are historically significant as objects directly associated with the Sydney Harbour Bridge (“the Bridge”). The AMUs consist of original, intact fabric, significant as an example of early-twentieth century engineering and part of the technical achievement evident in the construction of the Sydney Harbour Bridge. Although the AMUs demonstrate the characteristics of late-1920s hoist technology, they are a rare configuration of the components comprising crane technology, and are unique to the Sydney Harbour Bridge.

The holistic vision of both JJC Bradfield (chief engineer) and Dorman & Long (contractor/builder) to incorporate maintenance into the bridge design also contributes to the unique quality of the AMUs. The distinctive profiles of the AMUs in changing locations across the Bridge arches contribute to the Bridge‟s overall appearance. Involved in the continued maintenance of the Bridge for over seventy years, the AMUs have a strong associative significance with over three generations of workers who have worked on the structure.

Four AMUs were originally designed to provide access to the Bridge for continual maintenance; two servicing the south half of the Bridge (installed in 1930), and two servicing the north (installed in 1931). During construction in the 1930s, two 580-tonne electric creeper cranes moved inwards from the shore carrying


steel girders for the arch structure, with the AMUs following obediently behind allowing workers to set rivets and paint. Upon completion of the Sydney Harbour Bridge, the AMUs continued to be used as part of the regular and ongoing maintenance until 1997, when they were removed and replaced with new maintenance cranes, the originals considered to have reached the end of their working life after 67 years.

After almost 70 years of operation, the AMUs had become long outdated pieces of maintenance equipment. Their engines and mechanisms were antiquated compared to the new technologies available that would have made operations much simpler for Bridge maintenance crews. In addition, new legislation regarding Occupational Health and Safety and a better understanding of the dangers of lead-based paint and asbestos required changes in the way maintenance was carried out by staff. These factors dictated the need for new, safer, functional AMUs to be designed and built.

Tourism also played a role in the decision to replace the original AMUs. Before the AMUs were removed from the Bridge, small private groups were permitted to climb the arches, a perk often organised for participants of high level executive conferences and summits. However, as the AMUs were not designed to accommodate for this kind of traffic, they became part of the experience, with climbers having to climb onto the AMU chassis and operating deck, and walk directly through the operator‟s cabin in order to pass. The proposal for BridgeClimb was an additional catalyst for the replacement of the AMUs. When the new AMUs were designed in 1997, space was provided for visitors to walk directly beneath the AMU without having to physically mount it or pass through the cabin.

Figure 1: Historic view of southwest AMU on Bridge. Figure 2: Historic view of northwest AMU on Bridge.

2.2 DESCRIPTION

There were four original AMUs, each generally constructed to the same design and comprising the same elements. The AMUs are constructed mostly of steel and timber, and consist of four main elements:

2.2.1 Chassis

The chassis is a riveted solid frame, constructed of 150mm channel steel. The large cast iron traversing cogs are mounted to the chassis, as well as the motors and operator controls that allow the AMU to traverse the bridge arch. The chassis was originally painted with a lead-based outdoor paint system. Expanded steel mesh sheeting is laid on the top of the chassis to provide a working platform. On the chassis are two containment boxes (“cable drums”) housing large spools to which a length of steel cable is wound, facilitating the raising and lowering of the gantries. Four detachable “kickrollers” attach to the side of the chassis, working to clamp the chassis to the arch of the bridge, and stabilising the AMU as it traverses the arch. A secondary hinged chassis sub-assembly is attached to the main AMU chassis. It provides a base for the operator‟s cabin and permits adjustment of the cabin to a level position according to the position of the AMU on the bridge arches.

The chassis moved along the arch by winching itself along a heavy steel chain. However, the section of chain was limited in length. When the AMU reached the end of the chain, operators needed to clamp the AMU to the Bridge, and manhandle the heavy chain to the next anchorage point on the arch before proceeding.


2.2.2 Cabin

The operator‟s cabin is constructed mainly of an exterior cladding of galvanised sheet metal, wrapped around a timber frame. The cabin roofing is also constructed of metal sheeting. The interior walls of the cabin are clad with timber board, with various Bakelite controls and electrical wiring contained within a central control panel. Each operator‟s cabin has four windows and two doors for access to the front and back of the AMU. Within the cabin is another set of motors and controls, which operates the raising and lowering of the gantries.

2.2.3 Jibs

Two jibs attached at the cable drums service the AMU. These are constructed of strap, channel and cast steel elements. The jibs are connected to the pivoting cabin chassis and the cable drums with cast iron pins. The gantry cables feed from the cable drums and through each jib arm to suspend the gantry boxes.

2.2.4 Gantries

The gantries are working platforms allowing personnel to access the sides of the bridge arches. There are two gantries for each AMU, constructed of strap and angle steel bolted together to make a box frame. The base of this box frame is floored with Australian hardwood timbers. The gantries are slung from a set of rubber-sheathed cables. These are connected to the end of the gantry cable running down from the jib.

2.2.5 Small parts

In addition to the main elements above, there is a collection of small, associated parts including brackets, bolts, pins and clamps that all form the AMU.

Figure 3: Sydney Harbour Bridge AMU, general construction and materials

Although the AMUs are similar in design, each has their individual nuances that make them unique from each other. For example, because of their positions on the two parallel arches of the bridge, the


configuration of engines and motors of the AMUs on the south end of the Bridge is identical to the AMU diagonally opposite it on the north end of the Bridge. Another factor that affected each AMU is that they had their own programme for maintenance and updating throughout the near 70 years that they were in operation. They were updated on an „as needed‟ basis, with whatever materials were available at the time. This is evident in the different building materials found throughout all four AMUs. For example, roofing and window construction details were different in all four AMUs, allowing for some rough deductions in dating and originality.

2.3 REMOVAL AND STORAGE

The removal of the AMUs from the Bridge was a simple process of unclamping it from the arches and craning it off, the whole operation being completed in one night in order to accommodate for commuter traffic. Because it was designed specifically for the Bridge and assembled in situ, it was removed from the Bridge as one piece, short of removing the kickrollers and gantries. All went smoothly of course until the AMUs reached the toll plazas where they found that the AMUs would not fit through because the jibs were still in place. The quick decision was made to detach the jibs from the cabin, the only efficient way to do so being to cut the jib pins. This was done on three AMUs, however possibly they ran out of time on the fourth where they had simply cut the jibs in half.

Three AMUs were transported to the RTA Bridge Services depot in Rockdale. The fourth was claimed by North Sydney Council and stored at their Balls Head depot, with the intent to restore it for future display and interpretation, and thus keeping it within the context of the Bridge. At both depots, the AMUs quickly became neglected, forgotten and unidentifiable pieces of industrial machinery. The AMUs became dirty and flaking lead-based paint exposing bare metal beneath resulted in heavy corrosion throughout. They became overgrown by weeds and were a happy home to many appreciative insects (and other creatures). The AMU went from being known as the office with the best view in town, to being a receptacle for unwanted items, like an eclectic collection of women‟s clothing and lingerie found inside one of the cable drums.

The AMUs continued to deteriorate for nearly a decade, until moves were made to begin the preservation and restoration process in 2007.

2.4 FINDING THE APPROPRIATE CONSERVATION APPROACH

The Burra Charter1, a publication by Australia ICOMOS, sets out guidelines for the care and conservation of

built heritage places. Essentially, conservation involves the management of „change‟. This charter defines the idea of conservation as involving one, some, or all of the processes of preservation, restoration, reconstruction and adaptation. While the Burra Charter is more commonly applied to built heritage, the AMUs can easily be considered against these philosophies because of the size and scale of the item. Ultimately, all of the following processes were drawn upon during the conservation of the AMUs.

Preservation means maintaining the fabric of a place in its existing state and retarding deterioration.

Restoration means returning the fabric to a known earlier state by removing accretions or by

reassembling existing components without the introduction of new material.

Reconstruction means returning the fabric to a known earlier state and is distinguished from

restoration by the introduction of new material into the fabric.

Adaptation means modifying a place to suit to the existing use or purpose.

Interpretation is required where the cultural significance of an item is not readily apparent, and should

be used to enhance the understanding and enjoyment, and be culturally appropriate.

With the above processes in mind, and applying them to large-scale industrial heritage items such as the AMUs, conservation treatment could have been aimed towards one of three potential outcomes:

1. Reinstatement. Bringing them back to full working order would be an ideal outcome because in

addition to repairing and restoring all elements of the AMU to be fully operable, it would also allow for reinstating the original use and emphasising its significant historical context. However, this has significant challenges. Firstly, it would be virtually impossible to find or recreate a situation where the AMUs would be in operation as originally intended on the Bridge. Secondly, the implications of bringing the AMUs in line with current OHS legislation in order to operate would have resulted in substantial impacts on the original construction of the AMUs.

2. Preservation. This outcome would entail protecting the original fabric as is, and retaining as much original material as possible. Minimising any changes to the original fabric ensures that aspects

1 The Burra Charter (1999), Australia ICOMOS Incorporated


contributing to the AMUs cultural significance (fabric, uses, associations and meanings) have been respected. This approach has interpretive and research potential.

3. Display. This approach would entail restoring the AMU for public display. The work would involve

making physical changes to the original fabric as necessary to ensure durability and safety in a public setting, as well as telling an appropriate story in isolation. This may result in the removal and replacement of original fabric to make it safe for public installation, or to increase the interpretive potential of the display.

Figure 4: Three potential outcomes for conservation of an industrial heritage artefact.

3 DEVELOPING A CONSERVATION STRATEGY

3.1 FACILITATION

During the compilation of a Movable Heritage Database, the significance of these forgotten industrial artefacts came to light, and in 2007 ICS, with the support of the RTA, facilitated a workshop focussing on the AMUs and their future.

Consultation was gathered from several stakeholders, primarily from the RTA but also information and requirements from the NSW Heritage Branch (formerly the Heritage Office), and from within the local community, including North Sydney Council representatives & Historic Houses Trust Bridging Sydney exhibition curator, Caroline Mackaness. Facilitating the process were representatives from ICS‟ collections management department. The main points identified and agreed upon during this consultation were:

Removal of the AMUs was permitted in the late 1990s by the Heritage Branch on the provision that at least two of the four AMUs would remain intact and be moved to secure storage.

It was the general consensus that at least one of the AMUs should be interpreted for public display.

The ideal solution would be for the AMU to be placed or positioned within the context of the Bridge. This will ensure that the important association between the AMUs and the Bridge is maintained and the link between the two significant items is clear and immediate.

Storage, public safety, security and future maintenance are also important matters that will need to be dealt with once it is determined how the AMUs should be treated; there is a general assumption that the RTA will be funding majority of the works.


3.2 NEGOTIATIONS

With storage being a real hindrance for institutions in terms of accepting loans and donations of this size, it was unfortunate that candidates such as the Granville TAFE engineering campus and the Powerhouse Museum rejected the various proposals put forward. The latter was undoubtedly the primary and ideal nominee as they already housed a collection of Sydney Harbour Bridge material such as beams and associated artefacts. The next appropriate choice was the National Museum of Australia (NMA) in Canberra, who at the time was looking to expand their industrial and engineering history collection. Considering the Bridge is of national significance, the NMA is also an appropriate home for the AMUs.

One of the AMUs was already claimed by North Sydney Council, and held within their depot in North Sydney. The original intent to have this AMU restored for interpretation and display had not changed, and the plan remained for this AMU to be set within Bradfield Park, beneath the Bridge, as an industrial heritage installation.

3.3 CONSERVATION STRATEGY

Following the various conversations and workshops, the agreed conservation strategy roughly involved:

The full restoration of one AMU, with the intent to interpret for public display.

The full preservation and retention of one AMU, with the aim to keep it as „original‟ in fabric as possible.

Options for the future treatment of remaining two of four AMUs still undetermined. Suggestions for treatment included continuing to look to institutions to receive as gift or loan both in Australia and overseas, or disposal.

4 AMU FOR RESTORATION AND DISPLAY

Conservation work on the AMU nominated for display began in April 2009. However, preparatory works required had commenced several months prior. In this period before work, the methodology was negotiated and finalised, and specialist contractors in lifting, transport and hazardous materials management were sourced in order to achieve a smooth delivery for these significant heritage items. Conservation work to this AMU can be considered restoration and reconstruction, in the sense that the fabric was returned to a known earlier state, with introduction of some new materials (particularly paint, but minor other components as well).

4.1 CONSTRAINTS AND CHALLENGES

Restoration of the first AMU was difficult because all obstacles encountered during the conservation work were new and unexpected.

The challenge here was that it took some effort to see beyond the conventional idea of retaining everything, which is the most common view taken in conservation, and aim towards reaching a result aesthetically pleasing for public display.

How we approached the conservation treatment was also significantly influenced by the fact that the AMU contained unstable hazardous materials, namely flaking lead-based paint. This meant that every action undertaken needed to consider whether there was a health or environmental consequence. This consideration had a flow-on effect to how we contained the hazardous materials during lifting and transport prior to treatment.

4.2 CONSERVATION METHODOLOGY - RESTORATION

The scope of work was developed during the planning stages of the project, determined primarily by the RTA, in consultation with ICS. A set of performance parameters for the restored AMU were established to guide the decision-making process. These performance parameters included:

Occupational Health & Safety – The design is required to consider the OH&S implications of the

display. Items to be considered include trips, slips & falls surrounding the display including pavement details and transitions.

Durability – The design of the access restriction is required to consider the durability of the components given the exposure conditions evident in the vicinity of the Bridge. The design of connections and other sections of the works should consider the durability implications of those particular details.

Security – Security is critical in the design and configuration of the proposed display. The display is

required to be designed in such a manner that prevents the climbing of the structure and eliminates


access to the suspended stages. The potential vandalism of the display is a potential risk that should be considered and mitigated during the design stage.

Functionality – the display will be located within a functioning open area on the harbour foreshore.

The functionality of the display should relate with and complement the surrounding environment.

Heritage – the Sydney Harbour Bridge is one of the most significant heritage items in Australia, and as such the construction of any structure nearby needs to account for any impact on the heritage significance of the item.

An inventory was taken of the AMU with industrial heritage specialist Tony Brassil (Godden Mackay Logan), which identified how the array of parts found throughout the depot fitted together and operated as a single Bridge Arch Maintenance Unit. Once all the parts were identified and a brief understanding of their condition was noted, we were able to determine what work needed to be carried out. Essentially, work types could be divided into four groups; retention, removal, replacement and repair. Before any physical work could take place, further pre-work documentation was required including various management plans for safe working, lifting, transport, and exposure to hazardous materials.

The various repairs and treatments are summarised in Table 1:

Table 1: Summary of restoration works.

AMU Part Name Original retained

Original removed

Replaced with New

Original repaired Detail of repair / Surface treatment

Cabin (external) Blast and paint

Cabin roof was sealed with waterproof membrane

Reproduction of control box fabricated and installed to back of cabin

Cabin (internal) Door locks repaired and new keys cut

Asbestos in electric control panel removed

Cabin access ladder Blast and paint

Ladder straightened

Chassis Blast and paint

Gantries Blast and paint

Gantry floorboards Blast

New marine ply waterproof boards installed over original hardwood timbers

Gantry toolboxes

Gantry slings New shackles for gantry slings replace missing

Gantry pulleys Blast and paint

Jib arms Blast and paint

Jib backstraps Blast and paint

Added new fabricated fishplates to join cut straps

Jib pins Original pins cut on removal from Bridge; new 3-part jib pins required to permit reassembly, and to avoid substantial deconstruction of the AMU to reinstall the pins

Motors Blast and paint

Motor controllers Blast and paint

Motor controller boxes

Window (glazing) Glazing replaced with acrylic

Window frames Asbestos putty removed

Kickrollers Blast and paint

Associated smaller items and artefacts

Blast and paint

Collected and stored

With all pre-work requirements fulfilled, the AMU was wrapped in a plastic stretch film to contain any friable lead-based paint. It was then lifted and transported to a specialist blasting facility equipped to receive and


dispose of items with lead-based paint appropriately. The AMU was blasted to remove all traces of original paint, and bring it back to the base metal. This removed all surface corrosion on the metal and consequently halted any further corrosion damage. A new Micaceous Iron Oxide (MIO) industrial coating system was applied to the AMU, in Bridge Grey colour, to match RTA bridge specifications.

Figure 5: Restored AMU, before treatment. Figure 6: Restored AMU, after treatment.

Figure 7: Cable drum with missing jib pin, before treatment

Figure 8: New stainless steel jib pins, fabricated and installed, after treatment (note that jib not yet installed pending relocation for display of AMU)

4.3 STRATEGY FOR DISPLAY AND INTERPRETATION

The decision to display this AMU was determined early in the project, when the conservation strategy was being developed. This guided the conservation process undertaken. An interpretation strategy was prepared by ICS so that the full potential of the AMUs as a significant heritage item for public appreciation could be realised.

The key interpretive concepts revolved around a layered approach incorporating design, display, signage and a visual connection between the item and its historical context, the Bridge. The plan to display the AMU within the vicinity of the Bridge encouraged the visual connection between the two items. The proposal entailed elevating the AMU so that it could be seen from below, akin to its original context. The structural support evolved from a single column to the „tuning fork‟ concept seen in F igures 9-11. These were considered to provide a modern re-interpretation of the original location of the AMU on the Bridge, with a polished granite pre-cast box arch supporting cantilevered painted structural steel beams on which the AMU would sit.


Figure 9: Proposed installation of AMU on „tuning fork‟ support, perspective from ground level showing front of AMU.

Figure 10: Proposed installation of AMU on „tuning fork‟ stand, perspective from above showing back of AMU.

Figure 11: Proposed installation of AMU in Bradfield Park, Kirribilli beneath the Bridge

The proposals were submitted to North Sydney Council for approval, but the elected representatives of the local community struggled to see the visual attraction in a piece of industrial heritage installed in a picturesque area such as Bradfield Park. Eventually the plan to install one of the AMUs, which would have been placed under the care of North Sydney Council and retained the association with between AMU and Bridge, was rejected.


4.4 STORAGE

The AMU, having been fully restored and ready for outdoor display, had found itself back to being without a home until further notice. Following the restoration treatment the AMU was wrapped in a temporary plastic, and transported back to its original resting spot at the RTA Bridge Services depot in Rockdale. Although it was now a shinier, restored AMU, it remained unseen and unappreciated for over two years. Being stored outdoors and exposed to the elements, the temporary plastic wrappings began to dissolve and nature began to encroach back onto the AMU.

In 2011, an agreement was negotiated for temporary loan of this AMU to the National Museum of Australia in Canberra, for public outdoor display.

4.5 LOAN TO NMA

The NMA agreed to accept the restored AMU on temporary loan for a period of five years. Work commenced once again to move the item down to Canberra. Fortunately, much of the nuts and bolts of the operation had already been worked out and a simple review was quickly undertaken to bring the transportation processes back up to date.

As part of collection management procedures, an inventory of all parts for loan was taken and a basic condition assessment was carried out, to create a benchmark of how the item would be received by the Museum. It became evident that some additional works would be required to make the AMU ready for installation such as replacing the original hardwood timbers in the gantries and ensuring all necessary fixings for reinstating the jibs were available. This was provided by the RTA prior to loan.

The AMU was then re-wrapped for transport and delivered to an NMA facility in Canberra in June 2011. Installation of the AMU as a public outdoor installation at the NMA in Acton is due to occur in the near future.

The AMU has been loaned for a period of five years, an agreement that may be extended further. As part of the loan agreement, the NMA has agreed to be responsible for the continued maintenance of the AMU whilst within their care, involving cleaning and regular inspections for signs of corrosion and damage.

5 AMU DONATED TO NATIONAL MUSEUM OF AUSTRALIA

The story of the second AMU is different in many aspects in comparison to the first. Conservation work to this AMU can be considered preservation in a sense that as much of the original fabric was preserved in all possible instances, and where damage had occurred to the item, it was either left as is or means were taken to cease and reverse the damaging effect, rather than having the damaged element removed or replaced.

5.1 DONATION / CURATION / MUSEUM REQUIREMENTS

A Deed of Gift was drawn up between the NMA and the RTA, specifying the conditions of the donation. Generally, the Deed stipulated that some conservation work had to be carried out by the RTA prior to delivering and handing over ownership to the NMA. Some of these conservation requirements included removal of any unstable hazardous materials such as lead-based paint and asbestos, provide custom designed soft storage covers, and organise all works, loading and transport. Once received, the NMA have full ownership of the AMU, and take responsibility for all risks and liabilities associated with it.

In return, donation of the AMU must be recognised by the NMA, and the RTA must be credited in any publication or interpretation discussing the AMU.

5.2 CONSERVATION - PRESERVATION

The conservation process involved a great deal of consultation and collaboration between the RTA, NMA and the conservators carrying out the work. Some time was spent before work commenced, identifying the degree and extent to which the conservation work would be carried out.

Treatment commenced in early 2010, beginning with the manual removal of unstable lead-based paint, and wrapping for transport. The OH&S requirements for loading and transporting this item had already been dealt with in previous operations, so similar documentation was able to be produced in an efficient manner.

The AMU was taken to a specialist blasting and coatings facility where any further friable lead-based paint was removed using a light water blast. With all friable lead-based paint removed, risk of contamination by a hazardous material was removed even though red lead primer paint was still present and visible.

The water blast did act to remove some active corrosion that would have continued to deteriorate original fabric. However, much of the surface corrosion remained. The ICS materials conservators trialled several


corrosion treatment methods to address the continuing damage caused by surface corrosion on the metal. The successful methodology developed was a tannic acid process which worked to convert the residual surface corrosion to a stable, blue-black, non-active corrosion product. The tannic acid converted loose ferrous particles into a stable, harmless adherent compound that remains on the surface of the AMU. Converting the corrosion in this way meant that it did not need to be removed by more aggressive means such as blasting back to bare metal, and essentially created a coating protecting the base metal from further environmental effects.

Figure 12: Preserved AMU, before treatment. Figure 13: Preserved AMU, after treatment.

Minimal repairs were carried out to this AMU (see Table 2). As opposed to the first AMU which was destined for public outdoor installation, the second AMU was not treated to serve the same end purpose. The intention for this AMU was to be an example of a complete and unchanged AMU of the four originals, an archival record of industrial machinery unique to the Sydney Harbour Bridge and surviving intact from the early 1930s. Because there was no need to prepare this item for public viewing and interaction, things such as non-friable lead-based paint and asbestos cement sheet, broken window glazing and deteriorated timber elements were all retained. New elements were only fabricated if it was necessary for interpretation or to permit reassembly in future.

Being an archival record of what originally existed, measured architectural drawings were commissioned and prepared to illustrate all extant parts and how they fit together as one unit. A soft canvas fabric cover was designed and custom measured and made to fit the AMU, as an additional protective measure against external elements. Finally, a custom built storage trolley was designed and constructed by the NMA in consultation with ICS, in order to provide the item with appropriate care and protection whilst in storage and during any future transport.

Table 2: Summary of changes to elements during preservation works.


Original removed

Replaced with New

Original repaired

Detail of repair / Surface treatment

Cabin (external)

Cabin (internal) Door locks repaired and new keys cut

Cabin access ladder

Chassis

Gantries

Gantry floorboards

Gantry toolboxes

Gantry slings

Gantry pulleys

Jib arms

Jib backstraps

Jib pins Original pins cut on removal from Bridge; new 3-part jib pins required to permit reassembly, and to avoid substantial deconstruction of the AMU to reinstall the pins



Original removed

Replaced with New

Original repaired

Detail of repair / Surface treatment

Motors

Motor controllers

Motor controller boxes Original timber remnants installed onto new timber frame for interpretative purposes.

Window (glazing)

Window frames

Kickrollers

Associated smaller items and artefacts

5.3 DELIVERY

Once conservation work was complete, the process to wrap, lift and transport the AMU, this time down to Canberra, was again carried out. In all instances of lifting and transport, the logistics of moving an item of such scale involved various lifting and vehicle movement plans, lifting certifications, and appropriate licences and qualifications to carry out the work. In addition to this, because of the height, weight and its classification as a „wide load‟ item, the AMU was only able to be transported during specific times and through certain routes.

6 DISPOSAL OF THE REMAINING AMUS

Two of the four AMUs were conserved as per the statutory requirements set by the NSW Heritage Branch. During this process, it was necessary to cannibalise the remaining two for some components. The other two AMUs were in extremely poor condition. After all efforts were made to donate or loan them to other institutions, they were disposed of in 2010. All salvageable materials were recycled at certified merchants equipped to separate hazardous materials i.e. lead.

7 OUTCOMES

The story of the Sydney Harbour Bridge AMUs has evolved since their removal from the Bridge in 1997. It started from humble beginnings with participation in simple round table discussions and workshops, to developing complex and layered interpretation designs, and finally to carrying out conservation work guided by several different philosophies. Of the four original AMUs constructed exclusively to service the Sydney Harbour Bridge, one AMU was restored for future reassembly and installation as an example of engineering skill and progress and for appreciation by the Australian and greater community, while a second AMU has been preserved, frozen in time as an archival record of the most intact original, a rare and unique piece of engineering heritage with great research potential.

8 ACKNOWLEDGEMENTS

This project required contributions from many people. We acknowledge the following key contributors:

International Conservation Services – Julian Bickersteth, David West, Fiona Tennant, Erin Watson,

Ian Trapnell, Karina Acton, Rachael Crompton, Eleanor Sampaga, Eoin O‟Suilleabhain

NSW Roads and Traffic Authority – Vladimir Shopov, Stephen Sherwin, Bobby Yazdani, Naresh

Narendiran, Sada Sadadcharan, Rachael McMullan

National Museum of Australia – Mathew Trinca, Carol Cooper, Denise Mackenzie, Nicki Smith

North Sydney Council – David Banbury

SUBCONTRACTORS

Access Scaffolding – Peter Battiston

Carl Williams Contracting – Carl Williams

Godden Mackay Logan – Geoff Ashley, Tony Brassil

Hughes Trueman – Alex Been, John Butterworth, Russell Dunn

Hyder Consulting – Dr Richard Barnes

IMP Coatings – Albert Nixon

P & D Envirotech – Paul Dickinson, Dave Riches, Brett Riches

Pattons Awnings and Boat Trimmers – Tom Gastin


9 REFERENCES

Australia ICOMOS (1999), The Burra Charter: The Australia ICOMOS Charter for Places of Cultural Significance, Deakin University, Burwood

Banbury, David (2008), North Sydney Council Report to the General Manager: Item OSES01, 07/04/08, Sydney Harbour Bridge Crane Heritage Project, North Sydney Council, North Sydney

Berger, Ian (2003), Statement of Heritage Impact: Proposed Modification to Working Platforms, Sydney Harbour Bridge, NSW Roads and Traffic Authority, Environmental Technology Branch, RTA Operations, Sydney

Godden, Don; Mackay, Richard, (1989), Sydney Harbour Bridge Travelling Maintenance Cranes: Assessment of Cultural Significance, Don Godden & Associates, Sydney

Godden Mackay Logan (2007), Sydney Harbour Bridge Conservation Management Plan, Godden Mackay Logan, Sydney

International Conservation Services for the NSW Roads and Traffic Authority & the National Museum of Australia (2009), Sydney Harbour Bridge Arch Maintenance Unit: Conservation Report for the NMA Arch Maintenance Unit, International Conservation Services, Sydney

Raxworthy, Richard (2003), Oral History Program: Sydney Harbour Bridge Maintenance Cranes, NSW Roads and Traffic Authority

Waddell, Karina et al. (2005), RTA Phase 2 Movable Heritage: Heritage Study, Godden Mackay Logan Pty Ltd, Sydney

CONSERVING THE SYDNEY HARBOUR BRIDGE ARCH MAINTENANCE UNITS

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