Enhancing city’s resilience with new reservoir

Construction is underway on the Mount Cook reservoir, which will more than double the drinking water storage capacity for the city’s CBD and low-lying suburbs.

The 35 million-litre reservoir is part of Wellington City Council and Wellington Water’s wider programme of work to improve the resilience of the region’s drinking water network.

The seismically resilient reservoir will be fully buried underneath the hillside above Prince of Wales Park, in the Town Belt, and make the water supply more resilient for both normal operational needs and in the event of natural disaster or disruption.

Council Chief Infrastructure Officer Tom Williams says Omāroro Reservoir is a critical new piece of infrastructure for the growing city.

“We know the city’s water infrastructure needs investment – here’s a $68m example that will have multiple benefits for Wellington.

“It will ensure we can continue supplying customers with fresh, safe drinking water as our population grows, and take us from having less than a day’s worth of supply to about 48-hours’ worth if there’s any disruption to our supply or a natural disaster, like an earthquake.

“This is going to make our city more resilient. So far it’s been great to see so many members of the local community get involved in the project, and we look forward to continuing to engage with the community as construction moves forward.”

A total of around 44,000 cubic metres of material will be excavated, more than half of which will be stored on the site and used to bury and cover the reservoir site once construction is completed.

The site will then be revegetated, landscaped and restored, in accordance with the Wellington Town Belt Act, to ensure this precious regional resource is protected.

Safeguarding the Town Belt’s natural values has been a key focus for Council and Wellington Water’s project team and contractor HEB Construction.

A special lizard habitat created by volunteers.

The priority before any work started was taking care of the native lizards and skinks. Special habitats were created near the site, with help from Department of Conservation, community volunteers, and students from Wellington High School.

Around 26 lizards were safely captured and relocated to their new habitats in October, allowing arborists to work on removing the large old pine trees and other vegetation, which were then chipped for use in sediment control during construction.

The community also pitched in on a sunny spring Saturday to gather native trees, shrubs and ferns from the site and transplant them in other parts of the Town Belt.

Significant work has also gone into protecting the local stream and surrounding environment, with erosion control systems and two sediment ponds. These will collect runoff from the reservoir site during construction and the water collected in the ponds will be used for dust control on site.

Before any work on the Town Belt site could begin, detailed management plans addressing more than 190 consent conditions were completed.

Wellington Water Major Projects Stephen Wright says the organisation has brought together teams of experts from around the region to progress this critical project through extensive phases of planning, solution design, consenting and community engagement.

The reservoir site earlier this year before construction began. 

“Since May when the project got that final tick of approval, HEB has completed all the site preparations including establishing a residents’ parking area, fencing, access tracks, sediment ponds and erosion control and is now well into the excavation process," Stephen says.

To mark the start of excavation work, a community barbecue was hosted that saw more than 60 members of the community turn out, despite the rain.

The project has been recognised for its community engagement programme with two awards – the 2019 International Association of Business Communicators Gold Quill Award, and an IAP2 Core Values Award for small budget.

The project’s engagement initiatives include the Omārōrō Community Reference Group, a proactive forum for keeping the community informed and involved, and HEB's full-time community liaison representative, who is on hand to support the community and address any concerns for the entire three-year construction programme.

Enabling works for the reservoir were completed in June, with the construction of the major new pipeline corridor along Wallace Street that will connect the reservoir to the water network.

Over the next six months, HEB’s crews will be turning a lot of sod with the full excavation of the site and laying the inlet and outlet pipes across the upper field that connect to the main pipeline corridor.

The project is set for completion in late 2023. Over its construction period, the reservoir project will have more than 30 people working on the project at its peak.