water supply and sanitation in the wellington region water supply and sanitation in the wellington region water supply and sanitation in the wellington region involves the provision of the "three waters" – drinking water, stormwater, and wastewater services in the greater wellington region. water supplies to the wellington metropolitan area meet the requirements of the health act and conform with drinking water standards. however, for some of the towns in the kapiti coast and wairarapa regions, there have been occasional non-conformances with the required standards for drinking water quality and safety. the challenges for managing the three waters in the wellington region include the deteriorated condition of pipelines in the wellington metropolitan area. the pipelines are in significantly worse condition than those in other large networks nationwide, and there has been a recent history of serious failures. the water supply to the region is also at significant risk during a severe earthquake, although some projects are underway to improve resilience. asset ownership and service provision the three waters assets in the wellington metropolitan area are owned by five councils: wellington city, hutt, upper hutt and porirua city councils, and the greater wellington regional council. however, the water assets of these councils are managed by an infrastructure asset management company, wellington water. from 1 october 2019, wellington water also became the asset manager of the water assets of the south wairarapa district council. wellington water is jointly owned by all six councils. 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. three waters services for the remaining parts of the greater wellington region are provided by the kapiti coast district council, the carterton district council and masterton district council. asset management and investment planning benchmarking data published by water new zealand as part of their 2018/19 national performance review showed that capital expenditure on three waters assets in the wellington region is well below the average of the expenditure on networks in most other major centres, and for the wastewater network, expenditure was the lowest out of the seven large networks in the review. approximately 200 kilometres of the city's pipes were laid before the outbreak of world war i, and more than half of all the city's pipes will need replacing in the coming three decades. $578 million is required to fix a backlog of existing issues as at 2020. the forecast costs for new investment just to cope with expected population growth range from $2 billion to $4.5 billion. in a comment about the asset management challenges for the three waters nationwide in february 2020, water new zealand’s technical manager, noel roberts said that problems with wastewater assets in wellington are not unique to the capital city. he noted that each household in wellington currently pays $459 a year on wastewater but this is below the national average of $492 per year. spending on wastewater in wellington has lagged behind investment in drinking water, particularly with the city’s recent focus on improving resilience. wellington city councillors commented at about the same time that the city was already spending a third of its annual budget on water systems. councillor sean rush said that prioritisation of expenditure had to change from age-based replacement to where the consequences of failure would be the worst. long term estimates prepared in 2020 for the water infrastructure in lower hutt indicated that expenditure of $1.3 billion is required over 30 years to deal with ageing infrastructure. porirua city may require investment of $1.8 billion over the same period. in may 2021, the wellington city council approved a 10 year plan that included expenditure of $2.7 billion on water pipe maintenance and upgrades in wellington city, and an additional $147 to $208 million for plant upgrades at the moa point wastewater treatment plant. in june 2021, a report released by wellington water gave estimates for investments in water infrastructure that could be required to meet forecast population growth to 2050. the report indicated that total new investment for growth could reach $3.6 billion. the estimated cost of upgrade per new dwelling varied widely across the region, from $70,000 to $520,000. drinking water regional water supply networks weir and water supply intake on hutt river at kaitoke upper macaskill lake the supply of reticulated drinking water is regulated under the health act, and suppliers are registered and subject to a testing regime. the main registered water suppliers for the greater wellington region are greater wellington regional council, wellington city council, porirua city council, hutt city council, upper hutt city council, kapiti coast district council. masterton district council, carterton district council and south wairarapa district council. water sources for wellington metropolitan area water supply for the wellington metropolitan area comes from three sources: te awa kairangi / hutt river wainuiomata and ōrongorongo rivers waiwhetu aquifer up to 150 million litres of water per day may be diverted from the hutt river, provided an adequate flow is maintained downstream of the weir. the hutt river water supply provides about 40 percent of the water used in the wellington metropolitan area each year. there are times each year, particularly during summer months, where the total demand is greater than can be supplied from the three sources. there are two large storage lakes that can be used to supplement the supply during these periods. water sources for remaining areas the water sources for the south wairarapa district council area are the waiohine catchment for featherston, the kuratawhiti street bore for greytown residents, and the herricks bore field for users in martinborough. water supplies for the kapiti coast region are sourced from combination of bores and surface water from the waikanae river. water supply for the carterton district comes from the kaipatangata stream and two underground bores. masterton's drinking water is sourced from the waingawa river, about 10 km west of masterton. water treatment the reticulated water supply to the wellington metropolitan area is all chlorinated. drinking water in lower hutt, porirua, upper hutt and wellington city is also fluoridated. the only exceptions are petone and korokoro. these suburbs historically had an unfluoridated water supply and this has continued following a public survey in 2000. there are four water treatment plants located in the hutt valley (te mārua, waterloo, gear island and wainuiomata). these plants supply water for use in upper hutt, lower hutt, porirua and wellington cities. the treatment processes at the four treatment plants differ based on the characteristics of the incoming water. the gear island and waterloo plants both treat water that is drawn from the waiwhetu aquifer. water supply pipeline age and condition the 2018/19 national performance review published by water new zealand compares the average pipeline age and condition across water supply networks. the data for the wellington water supply network shows that 20% of the pipelines are in poor or very poor condition. the wellington network ranks the worst on this measure out of the six large supply networks nationwide. the review also includes average pipeline age. the wellington network has an average age of 43 years, and ranks as the second oldest of the six large supply networks. consumption, losses and metering 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. by way of comparison, daily residential water use in auckland and tauranga was significantly lower at about 156 and 189 litres per person respectively. both auckland and tauranga have water metering in place for all residences, but in wellington only around 1% of residential supplies are currently metered. water meters in march 2020, it was reported that wellington city council was considering installing water meters for all domestic consumers. at the time of that report, only 1,200 residential properties in wellington were using water meters. in december 2017, the kapiti coast district council reported that there had been a drop in consumption of more than 26% since water meters were installed in july 2014. quality and safety drinking water is subject to a regime of testing under the health act to verify that the water meets standards. results of compliance testing are published by the ministry of health. waiwhetu aquifer up until late 2016, bores in the waterloo well field were considered to be secure. however, a rising trend in bacterial count and e.coli detections triggered a review. at that stage, about half the customers supplied from the waterloo treatment station received unchlorinated water. during 2016 and 2017, water supply businesses throughout new zealand became aware of the severe public health consequences of the havelock north drinking water contamination incident and the subsequent government inquiry that recommended all drinking water supplies should be chlorinated. in 2017, a decision was made by greater wellington regional council to chlorinate all the water drawn from the waiwhetu aquifer. martinborough there were two periods during early 2019 when a "boil water" notice was issued to the residents of martinborough. carterton 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. wellington metropolitan area bulk water supply pipeline across hutt river at silverstream bridge the supply of water to the wellington region is potentially vulnerable to significant disruption in the event of failures caused by a major earthquake. an application in 2017 by wellington water for an easement for a storage reservoir referenced a 2009 study conducted by gns science of possible earthquake damage to the water network. this study estimated that for a magnitude 7.5 richter scale earthquake, there would be about 30 breaks on the main trunk pipelines and 60 breaks on the smaller branch lines. there could be as many as 8,000 breaks in the wellington city local supply network. bulk water supply and treatment facilities are also expected to suffer damage requiring repair. wellington water and greater wellington regional council estimated that it would take around 60‐70 days to restore bulk water supply to parts of the wellington metropolitan area. it could take several years to fully repair damage to the local water distribution network resulting from a severe earthquake, as much of the network may have to be rebuilt. a wide range of projects are being undertaken to improve resilience, including the construction of additional reservoirs. stormwater stormwater pipeline age and condition the 2018/19 national performance review published by water new zealand compares the average stormwater pipeline age and condition across networks. the data for the wellington water network shows that 16% of the pipelines are in poor or very poor condition. the wellington stormwater network ranks the worst on this measure out of the six large networks nationwide. the review also includes average pipeline age. the wellington stormwater network has an average age of 49 years, and ranks as the second oldest of the six large networks. porirua stormwater improvements in june 2020, the porirua city council announced that work was underway to increase the resilience and capacity of the local stormwater network. the scope includes the creation of a new wetland. wastewater petone esplanade central - wastewater pumping station properties in urban areas in the wellington region are generally all connected to a wastewater system via a gravity sewer. pumps are used to supplement the gravity sewers, by pumping wastewater to a treatment plant, or lifting wastewater from lower level drains into a higher elevation gravity sewer so that it can flow to a treatment plant. wellington's population grew rapidly in the late 19th century after it became the capital city in 1865. there were increasing cases of typhoid and cholera which were attributed to poor sanitation. in 1879 there were 75 deaths in wellington from typhoid, diphtheria, scarlet fever, measles and cholera – mostly in the central te aro area. after some political deliberation, construction of a city wastewater network began in 1893. it cost £175,000 and was completed by 1899. there are four separate wastewater catchments in the wellington metropolitan area: wellington city (extending as far north as johnsonville) porirua (from northern johnsonville to pukerua bay) karori hutt valley the catchments drain mostly via gravity, but there are approximately 170 wastewater pumping stations.