2018 Hirepool Construction Excellence Awards

Rescuing a vital container wharf

HEB Construction won the 2018 Cat 2 Construction Excellence Awards with a project that put a busy and commercially vital container wharf back into service.

The Kaikoura Earthquake in 2016 destroyed CentrePort Wellington’s Thorndon Container Wharf.

As a busy and vital part of the North Island’s logistic network, a large number of regional and local businesses and suppliers rely on CentrePort’s operations for importing and exporting goods.

The wharf is solely used for container trade operations, with two 750 tonne ship-to-shore (STS) cranes loading and unloading container boxes from berthed vessels. The reclaimed land behind the wharf also provides space for the storage and distribution of shipping containers and act as an empty container depot facility.

The M7.8-scale earthquake severely damaged the wharf, which was subsequently declared a destroyed asset. Its structure could not resist further gravity or earthquake loads, having moved laterally up to one metre in some places, which meant the STS cranes could not be operated or moved. The wheel bogies on the seaward side of both cranes had also derailed from the crane rail, which posed a significant risk for their stability in the event of further aftershocks, and significant risk to personnel and equipment. The earthquake also caused liquefaction and lateral spreading of the reclamation, pushing the wharf 200mm to 750mm towards the sea in the vicinity of the cranes. Wharf displacements up to a maximum of one metre seaward were measured in sections further to the south. The ground level behind the wharf also settled by approximately 500mm compared to pre-earthquake levels.

CentrePort made the decision to return the 600-metre long 25-metre wide, wharf and the cranes to service on a temporary basis for a period of three years.

The project scope

The $19 million project had to be carried out with considerable urgency as every day out of operation had a huge impact on regional and local commerce.

The project went to HEB, which has built up a reputation for constructing innovative marine engineering solutions for the Ports of Auckland, Tauranga, Napier, Nelson, Otago and the Chatham’s (Contractor June 2018).

On the back of this reputation, HEB was contracted immediately following the February 2011 earthquake in Christchurch by the Port of Lyttelton to secure and strengthen the Cashin Quay Coal Wharf and to demolish and replace the damaged Cashin Quay 2’s wharf.

HEB was engaged in an ‘Early Contractor Involvement’ arrangement, and a formal contract was issued under the NZS 3910:2013 Conditions of Contract – Cost Reimbursement procurement model.

The terms of the contract were as set out in the Contract Agreement, NZS 3910:2013 (General Conditions), Schedules 1 and 2 (Special Conditions), other Schedules, and other documents described in or incorporated during negotiations.

BondCM was engaged by CentrePort as the independent estimator to confirm and verify rates provided for the completion of the works.

Subsequent independent cost audits were completed by Deloitte on behalf of CentrePort.

The project team

HEB formed part of a collaborative team together with the designers, port operations staff and other specialist contractors, with each party selected on the basis of their expertise and capability to deliver extremely complex solutions in nine months, in the most challenging of conditions.

A skilled team was put together who included: Rafael Sierra-Ballen, as senior project manager; Simon Gard, operations manager; Bernard Kopke, area manager who had led the team on the Port of Lyttelton after the Christchurch earthquake; Scott Vallely, contract manager, who had also been heavily involved in the post-earthquake work on Cashin Quay; Bennie Vorster, estimator, who prepared management plans and procured plant and materials prior to the Christmas shutdown; and James Lake, project manager, who established the construction operation on January 9, and led the site team until completion of the works.

The project design

Severe structural damage to the wharf piles was evident at the pile head connections to the transverse wharf deck beams. Piles toward the landward side of the wharf suffered concrete crushing and complete disengagement of piles from the wharf beams that was caused by lateral movements and the effect of the raker piles along the landward edge.

This had caused multiple pile failures in the first two rows of piles, with the piles structurally disconnected at the underside of the wharf beams.

Vertical and horizontal offsets – in the order of hundreds of millimetres – were observed in some of these landward-side piles. Further analysis indicated that the observed magnitudes of movements recorded at the heads of the piles would have also likely caused pile flexural failures at depth.

Consequently, the full extent of the wharf damage was difficult to assess, as no access below the wharf was possible, and temporary securing works had to happen from above or behind the wharf deck.

To protect the project team, a 87-metre wide “exclusion zone” was put into place both landward and seaward of the STS cranes.

A mobilisation strategy was put together within a very short timeframe with logistical planning and securing of resources made over the traditional Christmas shutdown, between December 22, 2016 and January 3, 2017. The company was able to secure specialised piling equipment within days of the contract award, prepared it over the Christmas break and had it on site by mid-January 2017.

A team of 20 specialised construction staff were onsite within the first month, and the labour force expanded to 60 within three months.

Piling materials and steel plate and casings are typically imported for such a project and can take up to four months to arrive from confirmation of order. Through its supplier contacts and knowledge of Kiwi-based materials, HEB took delivery of steel pile sections within two weeks of setting up the site. The first steel pile was fabricated to length and installed within the first three weeks, even as the overall design was being finalised.

A challenging environment

Due to the proximity of the project to a coastal marine environment and the nature of the works (piling, gravel columns construction, earthworks), an environmental management plan was developed.

HEB has extensive experience working around and over water and with an Environmental Management System certified to AS/NZS ISO 14001:2004.

Not only was the coastal environment sensitive, but the project was subjected to tidal influences and the infamous Wellington wind, which could carry construction noise to sensitive neighbours.

The project was also exposed to the elements, and the team contended with gale force winds, rain, and ongoing earthquakes, and high winds suspended crane operations from time to time. The site was also surrounded by precariously stacked and fallen containers.

Environmental measures taken included a floating silt boom made ready for deployment if required; daily visual checks for discolouration of water determined no visible sediment loss to the sea; and bunded fuel storage and fueling procedure area.

As it was also a very tightly constrained site, with plant and people operating on a variety of tasks within a very limited space, the workflow and tasks were staged to avoid congestion. Consultation with the STS crane manufacturer Liebherr determined likely modes of crane collapse during the temporary works installation phase, and a construction sequence was developed to incrementally decreased the risk of crane collapse.

Some works were carried out over water, so handrails were placed to working areas wherever practicable. In addition, staff were issued with lifejackets, and a rescue boat was on standby at all times.

Wharf-based construction activities were not permitted until gravel columns, ties and landward wharf underpinning were in place. Only essential inspections on, or beneath the wharf, were undertaken and planned to minimise the time workers were exposed. Drones were also used where practical.

The wharf was monitored for lateral movement and wind speeds, and work stopped when wind exceeded thresholds. If any wharf movement was identified, work stopped and the cause identified and responded to.

Set back distances were set from the reclamation edge for tracked construction crane loading. These were relaxed as the risk of aftershocks attenuated, and stabilising works were put in place.

Mitigation measures were developed for reducing the risks associated with crane stability and support, including construction of a concrete plinth behind the landward edge of the wharf to provide an increased bearing width for the landward crane wheels, and replacing the seaward crane legs onto the crane rails.

Emergency access up onto the STS cranes was permitted, following a risk assessment process, to allow works to secure loose items at a height that could potentially fall from the cranes above the wharf.

The wharf piles could no longer be relied upon to safely support the operational weight of the cranes, so a key challenge was restoring vertical support to the landward legs of the cranes.

As the condition of the structure meant that it was not safe enough to allow construction workers to be under the wharf for long periods of time, an innovative solution was developed to provide the necessary support to the landward longitudinal capping beams, involving installing rows of tension and compression piles at each bent location behind the wharf.

A fabricated cantilever steel beam across the tops of these piles extended to support the existing longitudinal capping beam. The cantilever beam also engaged the landward longitudinal capping beam to resist further seaward displacements of the wharf.

A similar cantilevered beam system was installed to support the seaward crane beam. A tubular steel pile was installed at each bent location through a hole formed in the deck.

A steel beam supported over this pile, cantilevered out to underneath the seaward longitudinal capping beam and back to the existing transverse capping beams to resist the uplift loads. These new piles and beams were manufactured in New Zealand specifically for the project

New wharf support piles

HEB had to find a way to mitigate risk to the workforce due to potential future seismic events until the wharf was fully supported by the temporary works.

By using the existing precast form of deck construction, it was able to cut out sections of the wharf deck, install new piles and support beams, then replace the sections of wharf so that they were resting on the existing pile caps below. This approach meant that considerable time and cost in re-casting the deck sections was avoided.

The primary reason for adopting this method was to create full access to the new pile-to-wharf connections without using a workboat, which would not be able to evacuate from under the wharf in a seismic event due to the congestion of existing wharf piles. The wharf sections removed were three metres by three metre sections, allowing room to escape if required.

A steel ‘C- Hook’ platform was fabricated to allow safe access at just above sea level. The platform could withstand a reasonable amount of wave action.

In addition, real-time monitoring initially used at Lyttleton was there to warn the workforce of potential instability to the wharf structure. This involved 10 GPS transmitters fixed to the edge of the wharf and wired back to a solar-powered data logger that was wirelessly connected to the WSP- Opus research centre in Petone. This system also included a siren alarm that would warn the workforce to evacuate as soon as trigger levels were reached.

An unintended benefit of the system was that several evacuations were undertaken due to wharf movement caused by piling activity. In these instances, the intensive driven pile operation was causing the wharf to temporarily move by up to 20 mm.

As the workforce evacuated to the assembly point, the HEB site engineers were able to discuss and agree changes to the piling sequence with the Holmes Engineers and then redeploy the workforce with minimal disruption.

In this way, HEB and the designers were well informed to mitigate further damage to the wharf, disruption to the project programme and exposure to harm by the workforce.

Conclusion

HEB had the advantage of ‘self-performing’ the works, which reduced reliance on the availability of other contractors and time-consuming procurement periods.

The results spoke for themselves in that the STS cranes became operational again within 10 months of works starting on site, and achieved without incurring a significant safety incident.

While a fixed completion date was not required by the client, HEB had to commit to a completion date eight weeks in advance so that ships could be booked for arrival at port, and other operations could be planned.

Even with scope creep, the HEB team was able to forecast and maintain an early September completion date that was four months in advance of ‘practical completion’.

The port’s container business was recovered to pre-earthquake levels within three months from the STS crane operations re-commencing, with the wharf and STS cranes returning to service for container handling operations in mid-September 2017.

The tendered value was $17,240,000.77 (based on a few concept sketches) and the final cost, $19,214,495, due to scope re-definition because of the emerging development of the operational requirements, and the emergency nature of the works.

The 2018 Excellence award judges declared this winning project an outstanding example of innovative design and construction within an immensely challenging and evolving operational environment.

Such is CentrePort’s confidence in HEB that it has gone on to use the company for demolition of the redundant 300 metres length of Thorndon Container Wharf, a part demolition of Kings Wharf, and other small projects.