Public reports

Concept design including costs

The concept design stage for a new underpass began in September 2018. It focussed on determining where the underpass could actually fit without impacting the huge number of underground services that were extremely complicated or could not be moved (eg, the main gas supply line for Mount Maunganui).

The concept design identified the best alignment for the underpass between Owens Place and Bayfair and the design requirements to mitigate the issues of personal safety that were prevalent in the old underpass. As part of the concept design a construction methodology was developed together with the estimated cost. This estimate was based on a number of assumptions, which were then tested during the detailed design stage.

NZ Transport Agency scope approval

In November 2018, the Transport Agency announced a scope change to include a new underpass in the BayLink project. The initial cost for the new underpass was estimated to be $13 million, with the final cost to be determined once the detailed design was completed.

Detailed design 50%

Based on the selected alignment the detailed design process confirmed the construction of an underpass would be more complex than originally assumed, particularly in regard to the ground improvements required and the waterproofing, buoyancy, and the complex sequencing for the modified in-situ construction sequencing. This also identified significant programme and extra contractual costs that exceeded the available funding.

The total cost to the project was costed at $33 million, and the complexity of the work required would add more than two years to the construction timeline. The Transport Agency has a responsibility to ensure that whatever is built meets value for money outcomes. The new price of $33 million means that the underpass no longer meets this requirement.

Detailed design cost

The detailed design cost reflects the total cost impact for the project including increased cost of the complexity of the design, additional costs from temporary works and the complex staging sequence, and the costs associated with the extended time impact of the construction.

The detailed design costs were independently reviewed to ensure that they were robust. The parallel estimate process confirmed the cost proposal was robust and within the lower end of the expected pricing.

NZTA decision not to progress

The Transport Agency made the decision not to progress with an underpass because at $33m it did not deliver value for money outcomes.

Road safety audits

Road safety audits (RSAs) of the entire project are undertaken at various stages of the project life cycle including the investigation phase when we develop the scheme options; the specimen design and consenting phase; the tender phase; and the construction phase. During a design and construct contract the tender design is developed into a final design as the physical works on site progresses.

Safety auditors make recommendations and it’s up to the project designers and managers to consider these recommendations along with all the other factors, such as value for money, and decide which solution the Transport Agency will adopt.

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