NAVIGATION

THE ROADS AND BRIDGES LEADING TO THE NEW PARLIAMENT HOUSE

Keith Downey Dip CE, Dip Theol, FIE Aust
John Connal Dip CE, BE, MEngSci,MIE Aust


Keith Downey has spent 30 years engaged in the design and construction of a wide range of civil engineering projects in Victoria, Tasmania and Papua New Guinea. For the past 15 years he has worked for the National Capital Development Commission in various positions involved with the planning and design of major engineering facilities in the ACT. He was the Commission’s Design Manager for the Parliament House access roads project. He is now Director of Capital Works and Services with the National Capital Planning Authority.

John Connal is a graduate of Melbourne University and has spent 16 years in the design of civil engineering works; the past six of these having been in Canberra. He is an Associate of the consulting engineers, Maunsell and Partners, for which he has been involved on major development projects in Canberra, having moved to the National Capital originally to work on the Parliament House access roads project.

THE design and construction of the roads and bridges to the new Parliament House provided a rare opportunity where the blended skills of a wide range of professions was needed, to produce an integral, harmonious and appealing solution.

The success of the blending process is evident by the local and national recognition the work received. It was awarded Engineering Excellence awards, firstly for the bridge elements and later for the project as a whole, from the Canberra Division of the Institution of Engineers, Australia, as well as awards from the Association of Consulting Engineers Australia and from the Concrete Institute of Australia.

Clearly, in such a significant project the influence of key people is visible in the finished product. Primarily, in this instance, it is the touch of Aldo Giurgola, of the project Architects for the new House, Mitchell/Giurgola and Thorp (MGT). As far as the roads and bridges are concerned, the other major influences came from the late Richard Gray, formerly of Holford & Partners (United Kingdom), who was design adviser for the project to the then National Capital Development Commission (NCDC) as well as from architectural staff of the Commission.

The NCDC was the client for this work as it was responsible for all works associated with the House outside the 320 metre radius of the actual Capital Hill site.

EVOLUTION OF THE CONCEPT

The job of providing access to the new Parliament House, whatever the design of the House, was always going to be challenging. The Hill was at a node in Canberra’s transport system, with the surrounding roads serving both a wider metropolitan function as well as local access needs. The rotary interchange system of State and Capital Circles accommodated the peak traffic flows between Commonwealth and Adelaide Avenues, with more than 43,000 vehicles using the route daily in 1980.

MGT’s winning design added yet a further dimension to the task.

The access solution not only had to contend with the strengths and weaknesses of the existing transport system, plus provide for the future traffic demand for that part of the transport network, but also had to provide safe and convenient access to the new House.

The access roads converge
Fig. 14.1: The access roads converge on the northern entry to Parliament House (view from the top of the flagmast).Source: NCDC.

With up to 3,000 people working in the House, plus official visitors (including Heads of State) and more than one million tourists annually, the roads to the House had to cater for a diversity of visitors and modes of transport: private vehicles, buses, service delivery vehicles, vehicles in ceremonial processions, people on foot and on bicycles.

The original competition design brief for the new House contained possible access options including the radial avenues and the symbolic access from the Land Axis (the House is at the southern end of Griffin’s land axis from Mt Ainslie, the Australian War Memorial and Anzac Parade). MGT’s design chose to provide functional access from the Adelaide, Commonwealth and Kings Avenues, with service access from Brisbane Avenue. Ceremonial access was directly up the Land Axis. This meant, of course, that with no access from either Capital or State Circles a visitor would have to choose a route to the House some distance from the Hill.

There were concerns that this lack of clarity would be unacceptable. An early task for Maunsell & Partners, who had been selected by NCDC in 1980, as Civil Engineering Consultants for the roads and bridges, was to provide a feasibility study for the proposed road design. The major elements of the MGT design which had to be considered in the study were:

  • a large entrance forecourt on the northern side of the new House
  • an internal, circulatory access system (now known as Parliament Drive)
  • two new roads extending from the medians of Commonwealth and Kings Avenues
  • a road link from the median of Adelaide Avenue. These aspects of the design raised some fundamental issues. Problems of level differences, continuity of the Land Axis and traffic safety all required sensitive consideration to meet the new requirements of the design, along with the existing demands of the traffic system. Some innovative, and even some outlandish solutions were contemplated, such as:
  • lowering the House to reduce the approach grades to it
  • filling in State Circle to provide at-grade entrance to Capital Hill from the Land Axis
  • physically shifting the existing bridges which took Commonwealth Avenue over State Circle, to provide structures at the rear of the House
  • rearranging roads within the Parliamentary Triangle to improve the central access to the site, at the expense of restricting access from the Avenues.

While an over-riding factor was always that of budget, it is hardly surprising that the impact of some of these proposals stirred lengthy debate among the various disciplines involved.

Probably the most difficult compromise to reach involved the question of levels. The topography of the site and all the requirements of the House design were incompatible with simple and unobtrusive connections from the two main access roads — Commonwealth Avenue and Kings Avenue.

The construction of a link to the new House, along an extension of the Commonwealth Avenue median, with a maximum grade of 8 per cent to Parliament Drive from a point south of State Circle, dictated a maximum achievable level of RL583m at Parliament Drive. Maintaining symmetry across the Forecourt of the House, as was implicit in the design for the House, meant that the Kings Avenue extension would have to be at the same level. That would require Kings Avenue being lowered by 3 metres at its intersection with State Circle. This option was clearly unacceptable, as it would require a gross distortion of the Capital Circle profile to meet clearance requirements, and would also require major earthworks, with significant reconstruction costs, on State Circle.

Parliament House Competition
Fig. 14.2: Parliament House Competition Document access opportunities.
Access proposal embodied
Fig. 14.3: Access proposal embodied in the winning MGT

The solution adopted has an 8 percent grade from north of the existing bridges over State Circle which has the effect of vertically separating the extension above the level of the existing structures. While this created a number of complexities and the need for a new bridge in the median of Commonwealth Avenue over State Circle, it allowed the development of the appropriate elevation and entry arrangement onto Capital Hill.

Maunsell & Partners’ feasibility study showed quite clearly that MGT’s original proposal to provide a southern link from Adelaide Avenue would be unworkable because of: a. the anticipated amount of through-traffic on Parliament Drive, caused by the relatively direct nature of the link between Adelaide Avenue and Commonwealth Avenue b. the location of the median offtake on a crest and the need for traffic to cross an express bus lane.

Studies indicated two-way traffic volumes on Parliament Drive would exceed 1,000 vehicles per hour even when the average speed was reduced to 25 km/h, to reflect the likely interference to through traffic of vehicles turning into car- parks around Parliament House. This number of vehicles was considered to be unacceptable for Parliament Drive. This led to the alternative southern access being provided at Melbourne Avenue via a bridge over Capital Circle which, for clearance reasons, required Capital Circle to be lowered about 1.5 metres.

The key to good accessibility to the House was Kings Avenue. Here it was possible to provide an at-grade intersection with State Circle, the prime distributor road to Capital Hill. Direct access is made to Parliament House from both directions on State Circle and from Kings Avenue, the route being grade separated at Capital Circle, with a bridge structure, and involving some regrading and full signalisation of the Kings Avenue-State Circle intersection.

MGT’s original design proposed complex three-way intersections at the junctions of the Avenue extensions with Parliament Drive. When it became clear it would be extremely difficult to provide for comfortable and safe traffic flows, these were modified to simple T-junctions. They allow better resolution of levels on the Forecourt and easier access to the carpark underneath.

By early 1981 a compromise layout had been reached (Figure 14.4). It embodied:

  • preservation of the integrity of the winning design
  • providing a safer, more convenient southern access at Melbourne Avenue.
  • satisfying the need for a high level of accessibility with an at-grade intersection between State Circle and Kings Avenue
  • segregating the high speed inter-town traffic on Capital Circle/Adelaide Avenue from the traffic accessing Capital Hill
  • maximising the future capacity of the total traffic system to deal with general increases in urban traffic
  • preserving the geological feature in the State Circle cutting, which had been retained as a significant feature in earlier engineering works. All this was achievable at an acceptable cost, estimated at $30 million (1988 prices).

THE DESIGN PROCESS
Structures

The structures are the most dominant visual aspect of the access solution. The major consideration during their design was that they have all the necessary qualities of functional road structures, as well as being compatible with their setting.

The fundamental aesthetic quality desired of the bridges was that they could be viewed as bridges in the landscape of a country estate, inspired by the tradition of fine bridges built in Australia in the 19th century and suggesting the antithesis of high speed, highway structures. They all had to have high aesthetic quality for both the upper roadway and the lower roadway, being both major traffic routes and used occasionally for ceremonial functions. Additionally, they should have a “family” relationship to each other and to the existing bridges in the area, through consistency of basic shapes and details.

To achieve the “family” solution of bridges, many variables had to be melded into a consistent theme. They included variable road widths, different footpath widths, different pier heights, consistency of new details and compatibility of the new details with those of the existing bridges in the precinct.

It was no easy task and required input from a range of architectural consultants, from NCDC and from those advising Maunsell & Partners and the Parliament House Construction Authority (PHCA).

 The compromise solution.
Fig. 14.4: The compromise solution.

Landscape

From Griffin onwards the Central Area of Canberra has been developed on the basis of strong landscape concepts. Hence, the design concepts for both the new Parliament House and the adjacent Parliamentary Triangle rely heavily on major landscape elements for their integrity.

MGT’s design for the House relied heavily on using tree planting to frame some views, while leaving others open. Trees also would be important as windbreaks.

The Access Roads project, therefore, had to provide a landscape solution that integrated the design concepts on the Hill with those of the surrounding areas. The solution is based on native species planted both formally and informally.

Considerable engineering works were required to establish the ideal planting conditions, drainage and irrigation systems.

The complexity of these issues, as well as judging future growth of the trees resulted in the use of computer graphics techniques to understand the interactions. The computer- based work included generation of perspectives and simulation of movement along the major vehicle routes. These were varied to understand the situation in 1988, as well as next century when the trees will have reached maturity.

Traffic During Construction

Capital and State Circles are focal points for the distribution of central area traffic to the south. The free flowing Capital Circle accommodated the major traffic movements between Commonwealth and Adelaide Avenues, especially during peak periods. Therefore, considerable emphasis had to be placed on packaging and timing of works, so construction could occur, as far as possible, under traffic. Traffic-related considerations in phasing the work included:

  • the total period for construction was to be about four years, from early 1983
  • the need to construct the work in packages, to suit various financial and programming constraints
  • the advantages to be gained from closing sections of the road network during construction of the bridge structures
  • the need to ensure that convenient alternative routes were available when roads were closed.

There had to be access for up to 2,200 workers on the Capital Hill construction site. Additionally, as the work areas on the site changed, access locations had to be modified to match, as near as possible, the changes.

Numerous options were considered in each stage, taking account of the complex inter-relationships between the separate contracts, the physical requirements of each stage of the work and the changing access requirements. Sixty- two traffic staging drawings were produced during this task. The movement of traffic through the site was never seriously impeded during the construction process.

The Solution

The elements which comprised the total access solution to the new House are many and varied. However, all these elements were designed to be complementary, in both principle and detail, to the architecture and landscape of the House, while providing functional access to the House and to integrate the House design into the surrounding precincts.

  • roadworks (including cycle paths and footpaths) at Adelaide Avenue, the Adelaide Avenue-State Circle inter change, Melbourne Avenue, Canberra Avenue, Kings Avenue, Commonwealth Avenue, the Land Axis, State Circle, Capital Circle and in the Parliamentary Triangle
  • bridges carrying Melbourne Avenue over Capital Circle and Kings Avenue over Capital Circle and twin bridges on the Land Axis over State Circle
  • a tunnel carrying Capital Circle under the Land Axis roads
  • a box section viaduct on the Commonwealth Avenue extension, linking the new median bridge over State Circle with the bridge onto Capital Hill
  • retaining walls associated with the bridges and tunnel
  • a pedestrian and cycle underpass on State Circle near Flynn Drive
  • bulk excavation of about 300,000 cubic metres on Camp Hill and filling of the sector of the Land Bridge between State and Capital Circles and the Avenue extensions
  • new drainage and service lines to the Parliament House and diversions of existing services to facilitate construction of the new roads, bridges and tunnel
  • drainage augmentation works, including construction of two new retarding basins
  • soft and hard landscaping
  • protection of a geologically significant cutting on State Circle and construction of a viewing platform on the Land Axis.

Both the architectural and engineering aspirations for the structures were achieved by creating a construction environment compatible with the production of high quality work. Specification of the concrete work involved consultation with concrete manufacturers and with the PHCA and its other consultants. Prototypes were constructed for all major elements of the work, with trials of different types of surface finish to select a finish both economical and appropriate for the location. Formwork stripping times for all exposed concrete surfaces were carefully controlled to ensure good colour control.

While there were exacting requirements for workmanship , and access was difficult to much of the work, the design and construction proved to be economical. Construction techniques were generally conventional and careful planning allowed completion of the structures ahead of schedule.

Commonwealth Avenue extension
Fig. 14.5: Commonwealth Avenue extension from Capital Circle.

PRINCIPAL ELEMENTS
Commonwealth Avenue Extension

The highly prominent extension of Commonwealth Avenue onto Capital Hill required the building of a new bridge between the two existing bridges. The new median bridge is raised above the levels of the existing bridges.

With three separate bridges merging in the middle of Commonwealth Avenue from two different vertical and horizontal alignments, the resolution of the converging lines required considerable analysis and thought. Physical models aided the design process, which was further complicated by the fact that the ramps from and to Capital Circle were at slightly differing levels. In the final design the integration of precast parapet units and insitu concrete faces, some with warping geometry, provided a solution that provides a safe driving environment and has smooth, clean lines which are pleasing to the eye.

The bridge over State Circle fills in between the existing bridges, providing the effect of a continuous short tunnel beneath the bridge. This tunnel effect was reduced by recessing the soffit of the new deck above the level of the existing deck soffits. The same bearing ribs as those on the existing bridges are used on the new bridge and up-lighting onto the soffit is used to enhance the lift of the new central soffit area. This emphasises the emergence of the new bridge and lightens the space below the structures.

Between the bridge over State Circle and the bridge onto Capital Hill, is a box viaduct which sits on fill and is fully supported along its length. The walls of the box section provide the visual impression of a road extension, giving a functional symmetry of approach to Capital Hill which parallels that at Kings Avenue.

The project frequently called for innovative solutions. Early in the design process, options for the abutments of the new State Circle bridge were investigated. With the new bridge higher than the existing structures, yet needing to maintain the same foundation levels at the abutments, it required large tall abutments. With a conventional design approach, these abutments would have had massive footings and wall sizes. Instead, the economical solution of using approach spans was adopted. With this method the space is spanned by approach spans of beam and slab construction. In order to maintain the visual continuity of the bridge structure, the approach spans were founded on the rear faces of the cast insitu section of the bridge over State Circle.

The end bridge on the Commonwealth Avenue extension is an asymmetrical structure. It has the appearance of being firmly established in the landscape on the north side, yet “leaping” across onto Capital Hill. The thin deck section where the bridge passes onto the Hill was achieved by counterweighting the bridge with a mass concrete weight hidden behind the side walls of the abutment. This counter- weight reduces the mid-span bending movements to achieve the slender, asymmetrical structure. The support of the bridge at the northern abutment uses a bearing rib arrangement similar to the bridges over State Circle further north on the Avenue extension.

Bridge piers under the Land Axis
Fig. 14.6: Bridge piers under the Land Axis, part of a common theme for all bridges.

The Land Axis

The Land Axis links the new Parliament House to the Provisional House, with a formal approach of constant grade. A design requirement was that the Land Axis provide natural, uncomplicated vehicle access, plus a comfortable pedestrian access. The formality of the approach is achieved by providing a continuity of landscape between the two buildings with irrigated grass and native tree planting which emphasises the linear nature of the Land Axis.

The continuation of irrigated grass over State Circle is achieved by the unusual solution of providing planter boxes on the two bridges carrying the Land Axis roads over State Circle. Grading of the deck surface, waterproofing, drainage and soil were all chosen to encourage a quality grass surface with no apparent difference between the grass in this artificial planting environment and that on the adjacent natural ground.

The bridges are shallow, prestressed girder structures with a banana-shaped underbelly which was specifically chosen to emphasise the slender nature of the bridges. They have a bold and simple fascia created by a precast panel which is angled to catch the light, and for frequent washing by rain.

The design of the bridges meets all NAASRA specified loadings and includes stresses due to temperature differentials through the depth of the deck. Additionally, as the bridges were used to carry construction vehicles during the excavation of Camp Hill, they were designed to support loaded scrapers. The scrapers were restricted to the central strip of the bridge to reduce asymmetrical loadings. A speed restriction was also imposed on construction vehicles to reduce load impacts.

The piers which support the deck comprise three columns of varying height at each location and between the bridges. Thoughtful design was required to ensure the bridges did not create a forest of columns. After architectural consultation, the result was a set of angular columns with carefully chosen horizontal joints relating the columns to each other. The angular cross section was chosen to reduce the visual mass of columns. The columns have been repeated on the Melbourne Avenue bridge in a two-column pier arrangement.

Diagrams of parapet
Fig. 14.7: Diagrams of parapet options considered. The adopted parapet is shown at the lower right.
  Bridge parapet termination details.
Fig. 14.8: Bridge parapet termination details.

Parapets

A great deal of attention was given to producing the most appropriate design for the bridge balustrades and their terminations. This was necessary because they would be visually the strongest and most easily identifiable “family” components of the bridges, both for users and as elements in the landscape. A wide range of crashrail, handrail and balustrade alternatives was considered.

Standard specifications require that all road overbridges be designed to prevent vehicles from penetrating the edges of the bridges and crashing onto the road below. On conventional highway structures this is achieved by making the bridge handrails strong enough to contain vehicles or by incorporating a vehicular barrier adjacent to the kerb. However, this project called for estate bridges (bridges in the landscape), for which conventional techniques were unsuitable. After much analysis of steel and concrete barrier options, an edge parapet treatment was adopted for both structural and aesthetic reasons. It consists of a solid concrete balustrade surmounted by clean, crisp, precast fascia units. The overall height of the concrete parapet is 1.1 metres and the outer faces are sloped outwards to enhance the ability of the concrete to maintain a uniform colour as it weathers and to minimise buildup of grime.

The strong, clean lines of the solid balustrades, in conjunction with the bridge structures, achieve the desired blending with the landscape and the House.

The termination of a bridge balustrade is as important as the balustrade itself. The estate bridge theme suggested that the parapets should have positive terminations in harmony with the landscape. Various options were examined, and led to the adoption of a detail commonly used on the stone-arch bridges of the last century. The ends of the parapets gently flare away from the roadway and terminate with concrete bollards.

A similar parapet was used on the tops of the Capital Circle tunnel portals, to provide yet another link between the structures leading to the new Parliament House.

Capital Circle Tunnel

Designing the Capital Circle Tunnel presented geometric complexities. It was to be located on a reverse curve where Capital Circle passed through an existing cutting. The structure required greater width than the roadway pavement in order to provide lateral sight distance clearance around the curve.

This led to a barrel-vaulted shape solution, with the footpaths at the springing lines of the arch allowing adequate sight distance. The tunnel pavement rotates to provide super-elevation from three per cent in one direction to three per cent in the other direction. The rotation was achieved by rotating the whole tunnel cross-section, thus allowing a constant roof cross-section to be adopted for ease of construction. The resulting geometry was complex yet the easy-to-build section provides clean-flowing, aesthetically pleasing lines.

The tunnel is 156 metres long between the large reinforced concrete portals. The finish and joint pattern on the portals was selected after lengthy consultation with the Architects and with tunnel lighting designers. The portals have a textured concrete finish in keeping with the rest of the Parliament House complex, yet with an intensity of colour which ensures economical lighting in the tunnel by reducing the contrast between external and internal lighting levels.

The barrel-vault design is effectively a tied arch with the roadway slab forming the tension tie. Options of a pre- stressed and reinforced concrete pavement were considered; however, there was little cost differential and faster construction was possible with a reinforced pavement. The arch of the tunnel is connected to the portal walls via a ring beam which offers stiffness to the portals and the arch, and provides the architectural detail around the tunnel entry and exit.

The tunnel is constructed over two different rock strata. At the three-quarter point of the tunnel, near the western portal, a dipping fault line traverses the tunnel cross- section, skewed to the longitudinal axis of the tunnel. On either side of the fault the rock has different strength and stiffness. East of the fault the rock allowable bearing pres- sure is 270 kPa and stiffness (expressed as a modulus of subgrade reaction) is 50 kPa/mm. West of the fault the rock is the hard Black Mountain sandstone, which was attributed as allowing bearing pressure of 400 kPa and a stiffness of 5,000 to 25,000 kPa/mm.

The variation in rock stiffness presented problems for the tunnel cross-section, with greater stresses being induced by the differential settlement effects. Some thought was given to articulating the tunnel at the fault to cater for the anticipated differential movements. However, this would have created problems with waterproofing the structure and with the internal treatment of the articulation. Therefore, it was decided to strengthen the tunnel cross-section at the fault line, which simplified the solution and enabled the interior of the tunnel to maintain a constant appearance.

The effect of the fault was firstly confined to a right angle crossing by excavating soft rock and backfilling with mass concrete to “square-up” the interface between soft and hard foundations. The tunnel section straddling the fault was then thickened and post-tensioned longitudinally. This provided sufficient strength to resist the anticipated differential settlement effects, which would be magnified by the weight of the filling placed over the tunnel. During construction the thickened section was initially isolated from the standard sections to the east and west and later connected, with a 2 metre closing pour, as the final stage in the tunnel’s construction. The tunnel construction proceeded from the eastern end to allow the casting on soft rock to precede the casting on hard rock, which maximised the amount of differential settlement that occurred prior to the casting of the closing pours.

The effects of differential temperature and different progressive levels of backfilling (the material coming from Camp Hill) during construction were analysed in the design. This led to the specification of a maximum differential in backfilling heights of 2 metres from one side of the tunnel to the other.

The flowing curvilinear lines of the tunnel are accentuated by two lines of lighting, the intensity of which varies through the tunnel. A high intensity of light is provided in the entry portal, reducing along the tunnel as the driver’s eyes adjust to the lower light levels.

The tunnel has automatic sprinklers, fire hydrants, hose reels and warning devices linked to the ACT Fire Brigade network. Axial flow fans, activated by carbon monoxide monitors, operate should there be a buildup in carbon monoxide in the tunnel.

Given the closeness of the tunnel to the new Parliament House, a closed circuit television surveillance system allows constant police monitoring of the tunnel.

All services within the tunnel are concealed within the haunches at the arch springing lines, giving the tunnel a clear flowing appearance which is emphasised by the strip steel lining covering the curved arch. The lining has a red-brick colour between the rows of lighting, and an acoustic backing to minimise traffic noise.

Capital Circle turned western portal.
Fig. 14.9: Capital Circle turned western portal.

Geologically Significant Rock Cutting

State Circle passes under the Land Axis in an existing cutting through Camp Hill sandstone rock. The rock cutting exposes a geologically significant rock profile which had to be retained and protected from deterioration during the construction.

The Land Axis roads are carried over State Circle on bridges which have their northern abutments set back from the face of the cutting and are founded at a level above a berm which provides a top edge termination to the rock face.

The stability of this rock face was investigated and drainage works were designed to prevent surface water flowing over it and to minimise seepage and ground water pressure behind the face. During construction care was taken to protect the face from damage and the extent of remodelling of the land contours during the removal of part of Camp Hill was the subject of discussions with the Geological Society of the ACT, to ensure that the rock face remained intact.

A viewing platform has been constructed on the south side of State Circle between the two Land Axis bridges, to provide for formal viewing of the rock face.

Commencement Column Monument

On the original Capital Hill site a Commencement Column Monument was officially laid, commemorating the naming of Canberra as the Federal Capital.

The column comprised 63 stones with three foundation stones, one each laid by the then Prime Minister, the Hon Andrew Fisher; Sir Thomas Denman, Baron and Governor General and Commander in Chief of the Commonwealth of Australia; and the Hon King O’Malley, Minister of State for Home Affairs at the time.

The naming ceremony took place on 12 March 1913, 75 years to the day prior to the monument’s relocation on the Land Axis, and it was at the original ceremony that Lady Denman named the Federal Capital Canberra.

The ceremony to officially relocate the monument from its original site to its new site near the forecourt of the new Parliament House was attended by the modern day counterparts of the original participants, namely the Hon R.J. Hawke, Sir Ninian Stephen and the Hon Gary Punch,M.P.

The relocation of the monument was one of the finishing tasks in the access roads project, completed several months prior to the opening of the new Parliament House.

the clean lines of Capital Circle tunnel.
Fig. 14.10: the clean lines of Capital Circle tunnel.

Peripheral Works

The construction of the roads and bridges to the new House provided an opportunity to upgrade some adjoining areas, to link them in with the complex. Areas upgraded included:

  • The Lodge retarding basin. The open area adjacent to The Lodge was contoured, regrassed and planted with additional trees. The shaping of the area formed a small retarding basin to contain overland runoff.
  • Modifications to Adelaide Avenue bridge. Minor changes to the Adelaide Avenue alignment required kerb and barrier rail modifications.
  • Scrivener’s Hut. The original hut used by Scrivener during his survey for the National Capital site is located within the annulus formed by State Circle. Landscaping works, including a new cycle path, have upgraded this area, and the hut is now adjacent to a public recreation area.

Construction

Construction of the works was carried out in five main contracts, between 1983 and 1989, with all works substantially completed for the official opening in May 1988.

The timing and size of the five packages of work were adjusted to suit the traffic requirements of the site and cash flow constraints. The main packages were, in chronological order:

  • Southern Roadworks Package. These works concentrated on roadworks required at the southern end of the site and involved widening and lowering Capital Circle between Canberra and Adelaide Avenues. Also constructed was the Melbourne Avenue link towards Capital Hill and modifications along Adelaide Avenue.
  • Bridges Package. This was principally a bridgeworks con- tract with the construction of the two Land Axis bridges over State Circle and the construction of the Melbourne Avenue bridge.
  • Commonwealth Avenue North Package. This contract included all works on Commonwealth Avenue north of Coronation Drive. It involved the reconstruction of the Coronation Drive-Commonwealth Avenue intersection and all the other minor road and drainage works in the area.
  • Commonwealth Avenue Extension Package. This was the second largest package of work and involved construction of the new central bridge and ramp structures up the centre of Commonwealth Avenue, onto Capital Hill.
  • Tunnel Package. The Capital Circle tunnel was constructed in this, the largest of the contracts. Under these works, the Land Axis was formed, together with its landscape. The Kings Avenue link was also established in this package, with the construction of the Kings Avenue/State Circle intersection and the building of a new bridge over Capital Circle. This package of work substantially completed the Parliament House access roads works.
State Circle rock cutting prior
Fig. 14.11: State Circle rock cutting prior to removal of Camp Hill, showing abutments set back to preserve the integrity of the exposure.Source: NCDC.
 Ceremony markimg the repositioning
Fig. 14.12: Ceremony markimg the repositioning of the Commencement Column monument on the Land Axix, 12 March 1988.

The construction works involved some complex programming and timing issues; however, the construction of the works themselves involved no new or different construction techniques. The quality of finish was achieved by the application of good control over traditional construction methods. All work was completed to schedule and the initial estimates proved to be accurate, allowing for the effects of inflation in the intervening years.

Aerial view of construction
Fig. 14.13: Aerial view of construction in progress on tunnel, Land Axis bridges and Commonwealth Avenue extension.

Acknowledgements

This chapter draws heavily on the various reports and documents produced by design agents, Maunsell & Partners, in the process of design development and during their management of its construction.

The project was a major team effort with the authors part of that team which comprised not only NCDC and PHCA staff but also the many other consultants who worked on the project.

References and Sources

  1. Parliament House Construction Authority. Parliament House Canberra—Conditions for a Two-Stage Competition. Volume One—April 1979.
  2. Maunsell and Partners. Parliament House Access and Roadworks, Pre-Design Report. Volume 1—Text, July 1981, Unpublished report to NCDC.
  3. Maunsell and Partners. Parliament House Access and Roadworks, Pre-Design Report. Volume 2—Illustrations, July 1981, Unpublished report to NCDC.
  4. Maunsell and Partners. Parliament House Access Roads, Preliminary Design Report. January 1982, Unpublished report to NCDC.
  5. Department of Main Roads, New South Wales. The Aesthetics of Bridges. January 1987.
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