Water supply and sanitation in the Wellington region

The water supply to the region is also at significant risk because of the high rate of leakage, and it is also vulnerable during a severe earthquake, although some projects are underway to improve resilience.

[2] The assets in the region covered by these six councils includes 6,300 km of pipes, 138 reservoirs, 249 pump stations and four drinking water treatment plants.

[4] In 2024, a Wellington Regional Councillor expressed the view that the deterioration of the three waters infrastructure had reached a state of "network fault runaway", where there was more expenditure on repairs than planned replacements.

[24] A National Performance Review published by Water New Zealand for the 2019 financial year showed that daily residential consumption in the Wellington metropolitan region was about 226 litres per person.

[33] During March and April 2021, the Carterton District Council issued three separate "boil-water" notices, following the discovery of low levels of E.coli in the town's drinking water.

[36] The 2018/19 National Performance Review published by Water New Zealand compares the average stormwater pipeline age and condition across networks.

[45] The 2018/19 National Performance Review published by Water New Zealand compares the average wastewater pipeline age and condition across networks.

In November 2021, Wellington City Council announced that it was considering installing a new technology thermal drying plant at Moa Point to treat sewage sludge.

[46][47] In March 2020, Wellington Water reported the discovery of severe corrosion in the large main trunk sewer (the interceptor) over a length of 250 m in a section close to the treatment plant near Moa Point.

However, the area of the inner harbour from the Whairepo Lagoon entrance past the dive platform to the Clyde Quay wharf remained off-limits because of a “separate network issue”.

[54] Willis Street was eventually re-opened at the end of March 2020, after the permanent replacement had been installed beneath the road, and the temporary above-ground pipe removed.

[55] In January 2020, there was a failure of pipelines carrying sludge pumped at high pressure from the Moa Point treatment plant to the landfill at Carey’s Gully.

Specialists from the manufacturer flew to New Zealand to assist in the installation, but were required to spend 14 days in isolation because of the border restrictions imposed in response to the COVID-19 pandemic.

[62] The WWTP was officially opened in September 1989, ending the continuous discharge of untreated wastewater that had occurred at Rukutane Point since the sewage network was constructed in 1951.

Discharge of untreated sewage from these overflow points occurs when the total flow exceeds the capacity of pipes and pumping stations, typically during periods of heavy rain or where there is large amounts of infiltration from groundwater.

[63] In February 2020, the Mayor of Porirua announced the establishment of a roving team to search for issues such as cross connections in stormwater and sewage pipes that contribute to overflows and pollution of waterways.

[66] In August 2021, the Porirua City Council approved a process to designate land adjacent to State Highway 1 and the North Island Main Trunk railway for the construction of a $42.9 million wastewater tank.

[69] In June 2024, Wellington Water advised that there had been two instances in the year to date of overflows of untreated wastewater from the Rukutane Point pump station.

[72] In October 2018, a series of errors and omissions in the management of the Porirua WWTP led to a spill of approximately 5000 cubic metres of wastewater and solids from the outfall at Rukutane Point adjacent to Titahi Bay beach.

However, the Porirua City Council decided to establish a roving water quality team to specifically search for causes of sewage pollution arising from network faults.

Local residents including the Tītahi Bay Surf Life Saving Club complained about the failure, and also the lack of warnings given to swimmers.

In June 2023, a panel of commissioners reviewing the consent application on behalf of Greater Wellington Regional Council granted an 18 year renewal, despite overwhelming opposition in written submissions.

Prior to 2001, wastewater from the entire Hutt Valley was screened and then pumped without any further treatment via a 18.3 km (11.4 mi) pipeline to an ocean outfall near the harbour entrance at Pencarrow Head.

The temporary discharges cause pollution in the lower reaches of Waiwhetū Stream and in the estuary of the Hutt River, making it unsafe to collect shellfish, fish or swim in the area.

Wellington Water advised that the existing pipeline could be relined to allow it to operate at higher pressure, but that this would require discharge of treated sewage via a temporary outfall for an extended period.

[105] The underground wastewater pipe network in Featherston has significant issues with infiltration of stormwater, and this leads to pollution when there are overflows at the treatment plant.

[108] The council also purchased two plots of land, Hodders Farm and Featherston Golf Course, covering a total of 200 hectares (490 acres), as future sites for land-based discharge of treated wastewater.

Almost half a million litres of partially and fully treated wastewater was discharged into the Ruamahanga River in two incidents in January 2020, as a result of issues at the treatment plant.

[114][115] A report issued in 2022 stated that the design of the scheme was insufficient to achieve compliance requirements, with breaches of consent conditions relating to the rate and quality of effluent discharge to both land and water.

[105] In May 2023, the South Wairarapa District Council announced a sudden halt on new connections to the sewage network, because the existing treatment plan was at the limits of its design capacity.