Napier outfall repair complete - replacement challenges loom

A boat works on the Napier city wastewater outfall off the Awatoto coast. Photo / Paul Taylor

Contractors employed by the Napier City Council have completed repairs to the leaking underwater Awatoto wastewater outfall pipe in a four-month project which originally was planned for just one month.

The weather-dependant project, for which the council set a budget of $500,000, began in September, with hopes it would be complete by the end of October.

Council Sustainable Napier committee chairman Cr Keith Price said when the New Zealand Diving and Salvage Ltd crew got on site, it was clear the design solutions would need to be modified.

Further time was needed for parts to be specially made by Whakatu firm Warner Engineering, and Hawke's Bay Regional Council extended its approval of a variation to the outfall's resource consent to accommodate the evolving plan.

Price said it's "wonderful" to see this project completed, but there is still "plenty of work to be done" in the plan to replace the outfall, including what options there are for treatment and disposal – part of a replacement project that could cost up to $40 million.

The current resource consent for the discharge expires in 2036, setting a timeline for replacement, although the goal is much sooner. Further information, including estimated costs, is expected to be included in the next Long Term Plan later this year.

Price told Hawke's Bay Today: "I don't think we'd get away with what we've got now."

The next major wastewater project is the construction of ponds next to the treatment plant. They may need to be used during future shutdowns for maintenance, if repairs are needed and to take any overflow on standby for stormwater events.

"We will also continue to develop our plan to replace the outfall," said Price, who is now in his 14th year on the council.

Staff will continue to monitor the pipe's performance with drone and dive inspections.

Not including the repair project, council has spent close to $1 million on proactive maintenance of the outfall in the past two financial years, according to a council media release.

The outfall was constructed in 1972 and the repaired leaks were both discovered during routine inspections, the first discovery in 2018 being 700m offshore at a point where the pipe was joined. It was followed by the discovery of another closer to shore in April last year.

The first was at the point of a fibreglass joint installed in 1984.

Last June the council adopted a series of wastewater related resolutions, including bringing forward the replacement of the outfall, and increasing levels of service and linking this to improvements to the wastewater treatment plant.

The Wastewater Treatment and Outfall Masterplan has been developed and will help to determine future requirements for the full replacement of the outfall.

It could cost between $20m and $40m, and a detailed investigation needs to be carried out to both make sure the preferred option is the right one, and council has a more accurate cost estimate.

The repair and wastewater storage projects have been funded from reserves so there is no effect on rates.