Stories of the decade: Wastewater caused a big stink in Whanganui

The treatment plant design was a "hybrid" that never worked properly. Photo / File

As we enter a new decade, we take a look back at some of the biggest stories that hit the headlines in Whanganui over the past 10 years.

One issue this decade created an almighty stink - literally.

Whanganui's wastewater treatment plant, which began operating in 2007, ran into major problems in late 2012, resulting in a terrible stench over the city and surrounding area and the city being labelled "Ponganui" by some.

During the weekend of December 8-9, 2012, residents in the Kaitoke and Marybank area reported feeling unwell, having washing tainted by the smell and having to close their windows and doors to keep the smell out of their homes.

Whanganui District Council's infrastructure manager, Mark Hughes, said the plant had "suffered from a major intake of protein material through the Beach Rd pumping station" that weekend, causing a huge decrease in oxygen levels in the plant, halting the bioaugmentation digestion process and causing excessive odours.

The plant was partially shut down in an effort to reduce the smell and deal with the unexpected amount of waste dumped into it.

It was only the beginning in the city's latest wastewater woes.

A few days later the offensive smell had spread across the city and after a week of odour complaints, Horizons Regional Council slapped the district council with an official warning for breaching air quality rules.

The district council tried various means to solve the stinky problem, including inspecting the outfall pipe, installing different types of aerators on the treatment pond, putting in filtering equipment, using sucker trucks to remove solids from the pond, chemical dosing, installing an "odour fence" to try to contain the smell, using a helicopter to drop lime slurry on the pond.

Methods to try to stop the smell included dropping lime slurry on the pond. Photo / File

In mid-January 2013 Horizons issued an abatement notice, a legal directive requiring the district council to cease causing an objectionable odour beyond the boundary of its plant within the next four weeks.

Mayor Annette Main said the plant simply couldn't cope with the level of waste discharge from six wet industries, and after five years sludge in the ponds was at a level it should have been after 25 years. She warned there would be no "quick fix" to the problem.

International wastewater experts Cardno BTO were engaged to see whether the plant could be saved. The council was told it had never met its resource consent conditions, its "unique" design was faulty and reports on its non-compliance had never been sent to Horizons.

In March 2013 Horizons applied for an enforcement order from the Environment Court to help fix the odour issues as strong smells continued to affect residents.

In late April Cardno estimated it would cost $24 million to fix the plant, using some of the existing infrastructure in a reconfigured design. In June the council voted to conduct an independent inquiry into the defective plant, with the likelihood of legal action to follow.

In August the council chose a design with a $20.75m price tag for the new plant and in September filed court proceedings against engineering consulting company MWH Global for its involvement in the concept and final designs of the original plant. MWH countered that it believed the council did not properly operate and maintain the facility.

In September work began to bypass the settling pond by diverting the city's waste directly from the upper main pond to ultraviolet light sanitisers before pumping it into the sea. That would allow the remaining sludge to be removed from the smaller settling pond, dried and put back into the main pond which would be covered and capped. The community was warned to expect even more pong while the sludge was removed and over the summer while work continued.

Sucker trucks were used to remove sludge from the pond. Photo / File

Come January 2014, the council was seeking tenders to build the plant as well as considering whether to pursue its compensation claim against MWH.

By February, wastewater was being pumped out to sea.

On June 19, 2014, the council signed off on the redesign of the plant which factored in potential industrial growth in the city, and the following week announced that Hawkins Group had been chosen to build the new plant.

But in December 2014 there was another spanner in the works, with a potential blowout in operating costs forcing the council to delay the upgrade until more investigations were done. Again, the sludge was the issue. Peer reviewers AECOM and CH2Beca both predicted sludge quantities would increase more than estimated.

By March 2015 the cost of rebuilding the plant had blown out to $38m, and in July the council decided to add a dryer to the treatment process to reduce costs and give more sludge disposal options.

In September that year a High Court judge ordered MWH into mediation with the council and said the company must make a bone fide effort at mediation which began on October 15.

At the end of October the council decided to get another report on the new design, specifically whether it was the "optimum process when considering the environmental and cost issues of the plant".

In February 2016 the council said the legal stoush with MWH had, to the end of December, cost $860,000 in legal fees. The exact amount the council was seeking in compensation had not been publicised, but earlier it was considering claims of up to $10m.

The council said in late February it had settled its legal action against MWH but the terms of the settlement were confidential.

On March 10, 2016, the council gave the green light for a replacement plant but it still needed to sort out how much domestic and trade waste users would pay and secure a resource consent for the plant's marine outfall off South Beach. The cost was estimated at $38m and construction would be spread across three years.

In May 2016 the council released a previously confidential report by Humphrey Archer of CH2M Beca, that formed part of its legal case against MWH, which concluded that the MWH-designed plant was never going to work properly.

Major wet industries were not happy with the new plant and associated trade waste charge increases, with Affco telling the council in June that it wouldn't be using the new plant. Tasman Tanning urged the council to consider other option.

On July 1 the council amended its 10-year plan, opening the door to changing the design of the treatment plant and meeting concerns of trade waste users. A few days later it signed off on a full inquiry into the circumstances and council processes which led to the failure of the treatment plant. Robert Domm was later named the inquiry head.

The Cardno BTO-designed plant got the go-ahead in August 2016. Because Affco had not signed a letter to say they were out of the scheme, the council had to proceed as if they would be a user.

In early September Domm presented his damning report to the council. It found that staff had misinformed the council at critical decision-making meetings in 2004, known risks were downplayed by staff and cost-cutting was a key driver, resulting in a "hybrid" plant, designed by council staff and consultants, that was untried and untested anywhere in the world.

Later in September a contract was signed with Hawkins Infrastructure for construction of the new plant within a guaranteed maximum price.

Just when it seemed the new plant construction was all systems go, the design was back on the council's agenda following the October 2016 election. Six councillors - including four new councillors who stood on a ticket opposing the plant - wanted a review of the Cardno BTO design and its cost, particularly the impact on residential ratepayers if trade waste users didn't join the scheme.

Weeks of workshops, meetings and debate followed until in December 2016 the treatment plant again got the go-ahead, despite the misgivings of seven councillors, and construction got under way.

In January 2018 the Ombudsman ruled that the council's settlement with MWH should remain confidential after the Chronicle challenged it. The council said the out-of-court settlement resulted in it receiving "an amount in excess of [both] the total costs associated with the litigation, including legal costs and expert fees, and the professional fees paid to MWH New Zealand Ltd in connection with the wastewater plant".

The covered main pond was on view for visitors to the new plant's open day in March 2018. Photo / File

In March 2018 a valve was opened and all Whanganui's effluent was let into the new treatment plant for the first time, meaning raw sewage was no longer going out to sea. An open day at the plant attracted about 1000 visitors.

The council revealed in June 2018 the total cost for the facility was projected to be $40.57m. The main construction bill came in at $38.9m, $2.3m under budget, with extra costs for investigating alternative design options and additional site works.