Te Pae Christchurch Convention Centre

The Te Pae Christchurch Convention and Exhibition Centre is an ambitious project, creating a large mixed-use precinct in the heart of the city. The development has a large and varied stakeholder group, including Te Rūnanga o Ngāi Tahu, Christchurch City Council and the private sector—as well as the communities the centre will serve. Capable of hosting up to 2,000 delegates for a variety of national and international events, the state of the art centre includes a 1,400-delegate auditorium, a 3,600m² exhibition hall and 1,600m² of meeting rooms. This is a project of significant local and national importance, delivering a vital events hub that will attract domestic, national and international visitors and events.

Holmes was brought in to handle the structural design for the convention centre, working in partnership with an overseas architect with very little experience in our market. Our designs to date have focused on delivering a robust, resilient structure that supports the Centre’s commercial ambitions—a facility that creates the right atmosphere and flow for visitors, as well as demonstrating the flexibility convention centres demand. With large wide open spaces a key deliverable, our engineers have applied their deep knowledge of long-span structures to optimise the space and functionality of the centre.

In the challenging geotechnical conditions and seismic environment, our experience was invaluable in designing a structure that will stand the test of time and form an important part of the city’s cultural and commercial landscape.

The Hotel Britomart

The Hotel Britomart is the first eco-friendly hotel to hit Auckland, providing the city’s thriving tourism industry with a boutique offering that seamlessly blends sustainable features into an indulgent yet comforting atmosphere. Opening its doors in mid 2020, The Hotel Britomart incorporates a new 11 storey building and the refurbished, adjoining Masonic and Buckland buildings. The hotel offers 104 rooms, mixed use commercial space and administration on the ground floor, and a gym in the basement.

As the first property company in New Zealand to join the Green Star Performance rating system, Britomart successfully achieved a 5 Green Star rating during its design and build as well as its Green Star Performance accreditation since operating. This was achieved through the choosing of sustainable materials, incorporating reused concrete and recycled water through and passive design.

This project allowed our team to provide our client with a unique level of service through our collaboration with all our Holmes engineering practices including Holmes Solutions. The team from Holmes provided valuable insight into the structural elements of the design while Holmes Solutions undertook full scale testing of the precast façade panels incorporating pieces of brick.

Rigorous cooperation with the other stakeholders was required to successfully navigate the complexities of upgrading a heritage structure to current fire standards while adhering to sustainability and design requirements. The Fire Engineering strategy for The Hotel Britomart utilised smoke modelling to assess the most effective solutions for the project. Given the hotel’s height and occupancy requirements, one of the main challenges was the single stair. Through smoke modelling and egress calculations Holmes Fire showed that the stair achieves the fire safety performance requirements. The single stair was an important part of the design as it maximised the floor area available for hotel rooms.

The refurbishment of the existing Masonic and Buckland buildings included additional structural support, fire rated separations, smoke sealing and sprinkler protection.

 

 

Greenstone Financial Services Office

Greenstone Financial Services have recently moved into their new office in Norwest Business Park, Sydney. Holmes has been developing a fire safety strategy limited to the fit out of the 8 storey building, with a different design team and certifier looking after the construction of the base building.

The office has been designed to increase interpersonal connections between employees and features a pathway connecting the lower floors to the upper floors with open stairways. The building features voids in Levels 3 to 7 for the non-required stairways and has three fire isolated stairways that provide egress from all office levels.

The fire engineering strategy for the building involved separating the office tenancy into three fire compartments that spanned multiple levels connected by the internal stairs. Automatic fire shutters and fast response sprinkler heads were incorporated into the design so that the risk of fire spread through the void was reduced. Limitations have also been placed on the placement of storage, furniture and combustible materials in the void areas.

Due to the base building having a separate fire engineering report, our team have had to work closely with all the project stakeholders throughout the design and building process to prevent any clashes between both reports and to mitigate any delays to the project schedule.

44 Martin Place

The historic MLC building is a prominent sandstone icon of Martin Place. The heritage listed commercial development, located in central Sydney CBD was originally built in the 1930s, and has previously undergone redevelopment in the 1980s.

The building has recently undergone redevelopment to incorporate a large feature atrium through the centre of the building and add two new storeys above, using Cross Laminated Timber (CLT). The building required a bespoke fire engineering strategy that had to consider the heritage nature of the building and the specific requirements by the building owner to have an open atrium and highly interconnected working space.

Holmes previous experience with atrium design and our established relationship with local Fire Brigades allowed our team to provide the client and design team with specialist fire safety advice that shaped the atrium design to satisfy the safety requirements whilst also staying sympathetic to all other stakeholder objectives. The resulting design ticked all the boxes in terms of architecturally beautify, architecturally functional, flexible to accommodate tenant fitouts and robust enough to deliver occupant safety in a fire scenario. Specifically our design adopted horizontal fire curtains at the base of the atrium void thereby separating out the Ground Level portions and providing flexibility for the use of this Ground Level space to include a café, displays and decorations.

Structural Fire Engineering was also utilised to rationalise and optimise the level of protection to be applied to the mass timber structure while ensuring that structural stability and occupant life safety is maintained. Advanced finite element modelling is being used to establish a holistic and cost effective re-mediation strategy to the dilapidated existing steel concrete composite structure, which does not comply with the most recent fire standards.

ASB North Wharf

ASB North Wharf, headquarters of ASB bank and the anchor project in Auckland’s Wynyard Quarter, was a first-rate example of flexible working spaces and sustainable design when it was completed in 2013. The building spans two sites, with a multi-level glazed walkway over a central public lane that provides access through to the adjacent Waterfront Theatre site. 

The ‘Activity Based Working’ design presented a number of challenges that required performance based solutions. 15 individually themed, open areas were designed for flexible working also required a flexible evacuation design flexible to allow for the building’s occupants to move between floors. By utilising a performance based approachHolmes reduced the number of stairs required by a prescriptive solution, supporting the project’s objective to create an open and flexible layout. The evacuation plan also was designed to be flexible and utilise the open interconnecting stairs for egress in some fire scenarios.  

Sustainability was also a significant factor that influenced the design and use of the building. The addition of a ventilating funnel and controlled internal shading have assisted in the reduction of the building’s energy use by 50% and resulted in the completed building achieving NZGBC 5 Star Green Star Rating for Office Design. While the ventilation funnel provided beneficial natural lighting throughout the building, Holmes designed a smoke management system that not only aligned with the ventilation system but also avoided the need for a dedicated smoke control plant. A ‘hot smoke test’ was conducted by Holmes following the completion of the project demonstrating the strategy for smoke movement in action. 

Take a virtual tour through all 7 storeys and explore ASB North Wharf.

Flinders Centre

Flinders Centre is a high-rise A-grade commercial tower extension to the existing Bankstown Sports Club. The tower was officially completed at the end of 2018, following a 3.5 year involvement by Holmes Fire from the early concept design, through design development and construction till occupation.

Flinders Centre is eleven storeys, containing a gym, childcare, and commercial spaces. A future rooftop bar was also considered in the design, expected to be pursued in the near future. The tower is served by four high speed lifts contained in a feature glass shaft enclosure on the eastern side of the building, complementing the floor to ceiling glass walls on all sides of the building. The glass lift shaft was demonstrated as providing an equivalent level of protection as a conventional lift shaft to evacuating occupant and fire fighters, through a performance based fire engineering solution prepared by Holmes, by providing a suite of subtle fire safety features.

Holmes also took into account existing fire engineering solutions to the remainder of the development, including complex interactions between the existing and new building parts, to allow the building to function as one whilst maximising the safety of occupants during evacuation.  The fire engineered solutions provided by Holmes included:

  • Rationalisations to the stair pressurisation system
  • Extended travel distances
  • Fire stair discharge
  • Omission of smoke exhaust from the office tower
  • Sliding doors used for egress purposes
  • Provision of a combustible roof pergola
  • Rationalised protection of supply air control equipment

Throughout this project, Holmes worked closely with the client, architect, services engineers, fire brigade, Council, BCA consultant, and the builder to develop cost effective, practical and aesthetically achievable solutions which ultimately meet the design objectives whilst achieving suitable levels of fire safety for the building’s occupants and fire brigade personnel.

Holmes has been involved with numerous other extensions and fitouts of other parts of Bankstown Sports Club, including the construction of the Travelodge Hotel, restaurant fitouts, feature light installations, carpark modifications, café remodelling, plant room modifications, and ad hoc advice.

Grosvenor Place

The iconic Grosvenor Place complex is in Sydney’s CBD, bounded by George, Grosvenor, Harrington and Essex Streets. It features a two-storey ground floor entrance lobby and 44 levels of office accommodation providing 80,000 m2  of leasable floor area. The project involved a two stage refurbishment, including remodelling the existing food court and enclosing the lobby.

Holmes was engaged to provide fire engineered solutions where the building was unable to comply with the BCA Deemed-to-Satisfy Provisions. These non- compliances were due to the constraints of the existing building, that in some cases were not identified until site works began.

The building design incorporated multiple extended travel distances, often through the high space lobby. Alternative Solutions were developed to demonstrate that the large smoke reservoirs provided a greater level of safety for egressing occupants than in a Deemed-to-Satisfy compliant building, despite the extended travel distances. As such, Holmes was able to use the existing attributes of the building without requiring additional fire safety measures.

Reduced dimensions within the paths of travel from back of house and maintenance areas were justified by the use of signage and the implementation of management procedures that incorporated requirements for confined space access. Solutions were also provided for the non-compliant location of fire hose reels and the deletion of sprinklers from beneath external awnings and areas where it was impractical to provide coverage due to the proposed design and use.

A central, architectural element of the building is the circular stairway connecting the lower and upper lobby areas. Our design justified non-compliance with this stairway, allowing the client to maintain the architectural detail of this feature.

Throughout the project Holmes worked closely with Grosvenor Place management to provide solutions that would be conducive to the day-to-day functionality of the building. The resulting assessment presented acceptable solutions for all stakeholders, reducing construction costs and time for the builder, maintaining original architectural features and providing practical and manageable solutions for the end user.

Canterbury Leagues Club

The Canterbury Leagues Club in Belmore has long been one of Sydney’s premier hospitality destinations. Holmes has been involved in many of the upgrades and extensions to the building that have occurred over the years as the club expanded in size and patronage. The Club incorporates bars, entertainment lounges, restaurants, gaming, health club, function spaces and carparking.

Since the building has been constructed in a piecemeal manner, with many extensions at different times, Holmes provided a holistic fire engineering assessment of the building in 2010 to check that the design and operation of the building as a whole would be adequate in the event of a fire. This involved fire and smoke modelling to assess the impacts of potential fires and computer modelling of a complete building evacuation to determine the egress characteristics of the building.

Canterbury Leagues Club recently underwent a master plan redevelopment to add a five-storey basement carpark, café and gaming areas. Holmes provided Fire Engineering services as part of a large consultant team to develop a practical fire safety design that integrates with the existing fire safety design and enables a number of cost savings through the application of Alternative Solutions.

Key benefits of Holmes involvement are the provision of an Alternative Solution to permit the architectural glass lift and water feature to connect all levels of the five-storey basement and permit the fire-isolated stairway to discharge into the lift lobby. These aspects of the design enabled the architect and client to achieve the desired aesthetic in the area that would form the primary entry point for patrons.

As the Club was to remain operational during construction works, Holmes provided an Interim Fire Safety Strategy to justify temporary fire safety non-compliances such as blocking of egress routes and reduced exit widths. Through the application of management procedures that Holmes developed, the construction was able to proceed uninterrupted, whilst still affording a suitable level of fire safety for occupants within the operations areas of the building.

Australis Nathan Building

These historic buildings, built in 1903 and 1904 were originally warehouse and storefronts for importers and merchants, fast forward over 110 years and these have been transformed to bring these heritage buildings back to life. Australis House and the Nathan Building was an ambitious refurbishment combining the two buildings to function as a single structure and repurposed them to include high end retail, hospitality and office spaces. These buildings had strong character with a combination of cast iron columns, heavy timber columns and beams, timber floors with herringbone bracing and impressive brickwork.  

Our brief on this project was to avoid providing ceilings beneath these floors and encasing these columns in order to celebrate these features. Our performance-based design solution involved a combination of sprinkler installation, assessment of inherent timber strength and application of clear intumescent coatings to achieve sufficient fire separations within the building and achieve Building Code compliance.

B:Hive Smales Farm

B:Hive is taking commercial space to a new level offering shared office space that is fresh, vibrant and architecturally impressive! This new build construction has seven levels in total. One basement level (below ground) for car parking, one on-grade ground floor level which provides hospitality tenancy spaces, meeting room and breakout spaces, entry foyer and reception for the offices above. Above this are four levels of serviced office space leased on highly flexible short term and long term basis. The top-most level is dedicated for plant and building services.  

The 11,000 square metre building incorporates a diverse mix of office uses, with a mix of dedicated and shared spaces. It has the ability to house businesses from 10 to 310 employees per floor: from small startups to established corporates. 

Two features key to the design flexibility and interactive working environment are the open atrium and stair interconnecting all office levels and the ability for tenants to use flexi-space with up to 50% more occupants than a standard office building design. Using a novel smoke control strategy developed collaboratively with the day-to-day ventilation design, Holmes justified a fire safety solution which avoided the need for fire curtains or smoke separations around the atrium.

Pier B Extension, Auckland International Airport

Auckland Airport has a number of expansion phases planned and underway on its International Terminal. The expansion of Pier B added two new gates (17 & 18), increasing the number of international aircraft using the airport. The 190-metre extension enables Pier B with the flexibility to accommodate a total of four A380 or eight smaller A320 aircraft at any time. In addition, the Pier B bus lounge was expanded from two boarding gates to four, to allow greater ability to board flights using aircraft located away from the terminal.

The project challenge for Holmes was the delivery of the construction phase in five stages, whilst maintaining the continuous operation of the airport for commuters and staff alike. Construction involved temporarily relocating the principal three main egress stairs for Pier B and then reinstating these into the permanent design. All of this needed to be undertaken without adding significant cost through temporary works.

Working with interim strategies is a frequent request of our clients, where we need to strategise closely with our project stakeholders, ensuring smooth transition of construction through to operation whilst meeting adequate safety requirements through the entire process. In doing this we take to time to understand the constraints and provide options to ensure the most workable solutions are adopted.

Using performance-based design solutions for the project provided a more efficient egress design including reduced construction costs for the client where we enabled the elimination of stairs that were part of previous fire strategies.

Feature New Zealand landscape artwork and sculpture is also incorporated to the design, welcoming guests to this area of the international terminal which has also been fitted out with a new retail store and food and beverage outlet. Feature ceilings provided challenges to our fire protection design to ensure that sprinklers were installed to operate effectively, and without compromising the aesthetics.

Eastlakes Live by Crown

Developed in collaboration with award-winning architects, fjmt, Eastlakes Live has been inspired by native Australian plants and golden hues of nature. The Eastlakes shopping centre redevelopment aims to provide a revitalised destination that is integrated with modern apartment living, linking to the adjacent Eastlakes reserve.

The project has been split into two sites and stages, one on either side of Evans Avenue. The north site (being built first) is a single storey shopping mall, upon which there will be three blocks of residential units on the Podium landscaped space. The south site, currently at concept/early development will be a larger two-three storey shopping centre designed with an X formation. The ground floor will feature an extensive shopping complex, creating a unique shopping experience for not only the residents but also opening the development to the community at large. On top of the shopping centre, a large landscaped podium will house four feature residential tower blocks. The architectural form of these building will be impressive with the largest residential tower in an arc formation.

Based on the preliminary architectural drawings, Holmes was able to identify areas where the design either required or could be enhanced by Alternative Solutions including solutions to permit reduced fire ratings.

The retail areas in the southern site require a smoke exhaust system, however rather than taking the broad approach specified in the building code, we have undertaken Computational Fluid Dynamics (CFD) modelling of the retail malls to predict the movement of smoke from a number of hypothetical fires. This enables a more efficiently designed smoke exhaust system, and additionally will intend for the smoke zones to be larger than those permitted in the building code. Holmes in addition to the retail space added significant value and design flexibility to the project by assessing the holistic risk of the residential portions of the building based on its use and specific design intent.

Assessing a project and how the design can be advanced using performance-based design is what our team strives to develop, resulting in a design solution that is advantageous to all stakeholders involved, with advanced safety for the end users as the ultimate focus.

 

Aurora Centre (56 The Terrace)

The Aurora Centre project in central Wellington involved the redevelopment and structural strengthening of Unisys House, the demolition and rebuild of the adjacent Aurora Chambers and a new five storey addition over the existing Aurora Terrace carpark. This existing 20 level building constructed in 1968 was gutted back to its concrete structure and redeveloped along with the construction of a new seismically isolated 9 level building next door. The end result was over 25,000 m² (270,000 sqft) of commercial office, retail and carparking.

The project has provided a structurally robust, functional and compelling new home for the Ministry of Social Development. The redevelopment of the buildings redefines their profile and purpose, including seamless connections between the structurally separate components, creating a cohesive and integrated complex.

Fire Engineering

22,000 m² (240,000 sqft) on levels 1-19 were occupied by a single Government tenant there was a need to incorporate new internal circulation stairs that linked levels 3-18. The stairs were able to be open across a total of 11 of those levels without the use of mechanical smoke control systems.

The constraints for the existing structure meant a focus of the fire engineering design was to be able to utilise the existing stairs that did not comply in geometry to current Code. Holmes had previously carried out a fully filmed and documented egress study for the building (as part of an employee’s PhD study) which was able to be used to understand how the occupants (over 2000 of them) used the existing stairs under evacuation conditions. This deep knowledge of the building was crucial in developing a solution that satisfied building officials and the Government tenant.

The age of the building meant that at the outset the building sat outside the new-Code standard and on that basis the redevelopment was able to deliver a modern and new-Code-compliant building with substantial fire safety upgrades—a significant and effectively ‘new’ for the building owner.

Structural Engineering: An NZ first—Fluid Viscous Dampers

The development has showcased technical expertise and innovation in engineering design elements. Most notably, the Aurora Centre demonstrates the first use of Fluid Viscous Dampers as part of the seismic strengthening of an existing building in New Zealand. These were used as the primary strengthening mechanism for the 18 storey tower building, and act as shock absorbers to dramatically decrease earthquake-induced motion.

Retrofitting the dampers into the existing tower structure brought it to 90% of the New Building Standard (an A+ seismic grade). In addition to the Fluid Viscous Dampers, our team developed a new concrete encased steel (CES) column assessment methodology to better understand and assess the seismic performance of the existing structure and its interaction with the proposed damper strengthening proposal.

This technically challenging project has resulted in significantly improved buildings, not only in terms of appearance and functionality but also in regard to seismic resilience.

40 King Street

40 King Street is an existing 100-year old eight storey office building in central Sydney. Due to a proposed major refurbishment, the building had to comply with the requirements of the current Building Code of Australia. The existing concrete slabs within the building could not comply with the current concrete code requirements due to insufficient concrete cover to the reinforcing bars. To upgrade the existing slabs to comply with the current code requirements would involve the addition of passive fire protection to the slab soffit; this would not only have been costly but time consuming and would damage the existing heritage fabric of the building.

Holmes carried out advanced analyses to determine the inherent fire resistance of the existing slab. The analysis demonstrated that the existing slab had enough inherent fire resistance to withstand a realistic fully developed fire, thereby negating the requirement to apply additional passive fire protection or to thicken the slab to meet the prescriptive requirements of the Code and Standards. This provided significant cost savings to the project and minimised disruption to the fabric of the existing building.

Christchurch Justice and Emergency Services Precinct

As the first ‘anchor project’ delivered in the rebuild of the Christchurch CBD after the 2010 and 2011 earthquakes, the Christchurch Justice and Emergency Services Precinct will always be remembered as a project of national significance. It is the first multi-agency government co-location project in New Zealand’s history. The forward-thinking design brings together all of the region’s critical services, including the Ministry of Justice, New Zealand Police, Department of Corrections, New Zealand Fire Service, St John New Zealand, and the Ministry of Civil Defence and Emergency Management, to name a few—and accommodates an estimated 2,000 workers daily.

Holmes provided the fire and structural engineering for this innovative new precinct.

Fire Engineering

Holmes carried out not only the general fire engineering services for the team but also advanced structural fire analyses for the project, specifically the Justice Building. The fire engineering team who delivered the project remained together for the entire five year design and construction period. This continuity of service typifies Holmes’ approach to major projects and allowed the Client (Ministry of Justice) to achieve a fantastic result with continuity of the design and consultancy team.

From a structural perspective, the building has stringent requirements of structural robustness for seismic and fire resistance, due to the Emergency Operations Centre located in the Emergency Services Building – this is the centre for emergency response and coordination in the event of a natural disaster. The design of an Emergency Communications Centre (effectively a nationwide 111/000/911 call centre) was also required to have continuous occupation and operation in the event of a fire within any other part of the building.

A series of advanced analyses using non-linear finite element analysis was carried out by Holmes to test the robustness and stability of the structure in fire conditions. The analysis consisted of 3D modelling of the structural frame under exposure of a realistic fire, looking at its effect on each structural component. Unique and specialist 3D modelling inputs allowed the structural design to be safely optimised, whilst avoiding over-design. The resulting analysis demonstrated that the concrete filled steel hollow section columns and the secondary steel beams did not require additional passive fire protection. This provided significant cost savings for the project through the reduction of passive fire protection to the beams and columns.

This structure needed to not only resist fire but also be immediately operational post-emergency events. As a specialist design and project for Holmes, the technical detail of the fire safety of its smoke control system throughout the five level atrium, through to its specialist structural fire analysis is an exemplary example of how consultancy can be co-ordinated and managed to offer the most advanced fire safety response to serve an advanced function in not only its building design, but its users.

Structural Engineering

The precinct consists of four, four storey towers supported on a common base isolated podium structure. The base isolated podium we designed aims to mitigate structural and non-structural damage following a major earthquake and ensure continued functionality of the facility. This was an extremely challenging design brief that we were delighted to take on—an important and positive project in Christchurch’s rebuild.

Commercial Bay | Te Toki i te Rangi

Commercial Bay is the largest mixed-use development ever undertaken in Tāmaki Makaurau (Auckland) CBD. The project combines two existing office towers with a new three level high-end retail complex and a new 39 level commercial tower—all above three levels of basement car parking and two train tunnels, with associated major complexities and structural transfers. Holmes was the Lead Structural Engineer on this important project, as well as providing fire and infrastructure engineering.

Structural Engineering 

The architecture of the flagship 39 level Commercial Bay tower in downtown Tāmaki Makaurau celebrates and showcases the structural form of the building. Working closely with the architect and the wider project team, Holmes designed visually striking columns and diagonal braces, which are clad to express and accentuate the structure. The structural system of the tower consists of a diagrid structure, featuring composite concrete filled hollow section steel tube columns and braces and long span beams.

In a large complex project with many stakeholders and challenges, the Commercial Bay tower is an example of a well-coordinated structure, underpinned by great BIM execution and a willingness for project partners to work through challenges collaboratively. This result was achieved through excellent continuous ongoing collaboration and communication between project stakeholders—particularly the architect and the structural engineers. Weekly exchanges of Revit files via a shared FTP site ensured well-coordinated Revit models and delivered a clear accurate picture of progress.

The penetrations through the floor slab were modelled in the structural slab, and penetrations for building services were incorporated into the structural steelwork floor beams. Across the project, regular meetings, ongoing communication and open, positive discussions ensured alignment and synergy through the design process.

With a premier site overlooking the harbour, Commercial Bay is already an iconic landmark on the Tāmaki Makaurau foreshore and skyline.

Fire Engineering

Holmes provided fire engineering advice for the entire development, including master-planning to allow for future subdivision of the entire block into four discrete separate properties. The fire engineering allows for separate phased evacuation and independent commissioning and ownership of fire protection systems serving the retail centre and the office tower. Holmes was also engaged to provided advice to almost all of the retail and office tenants, to integrate their specific tenancy fitout design with the overall base building fire engineering strategy.

Holmes was also engaged to provide specialist structural fire engineering services to rationalise the passive fire protection requirements of the entire tower. Advanced finite element modelling was undertaken to analyse the response of the whole floor and megaframe in fire. The analysis demonstrated the robustness of the whole structural frame in resisting a full burnout fire. The resulting analysis showed the composite columns and secondary beams did not require passive protection and a reduced FRL could be applied for the primary beams. The analysis was peer reviewed by Professor Jose Torero who is a renowned international expert in structural fire engineering.

This resulted in major savings on site with regard to project timeframes, labour and material costs, and the improved aesthetic and air quality within the space. The costs savings in fire proofing alone was estimated to be approximately NZ $4M.

City Rail Link Tunnels

The City Rail Link (CRL) runs beneath the Commercial Bay site on the Auckland CBD waterfront. Holmes, as part of a Fletcher Construction Design and Build Team, were responsible for the structural engineering design and documentation of the portion through the Commercial Bay site for the owner Precinct Properties and key stakeholder Auckland Transport. This separate CRL tunnel portion ties into the two adjacent enabling C1 contracts, C1 (Britomart Station) and C2 (Albert St).

The two box tunnels are on a curved alignment and merge into a twin tunnel box within the site. Separation of the tunnels from the surrounding development and the transfer of loads from the multi-storey office tower above were among the considerable challenges involved. The CRL box tunnels are constructed within the Commercial Bay basement area, with the structure of the development forming an enclosure over the top of them. Tension piles resist hydrostatic pressures on the base of the tunnels. The cast insitu tunnel base, walls and roof were formed using moveable formwork. The tunnels were designed for IL3 loads, with a 100-year design life.