Why Central Interceptor?
In older parts of central Auckland, wastewater and stormwater flow into a combined network of pipes. When it rains heavily, stormwater can overwhelm these pipes. Unfortunately, this means that wastewater overflows with stormwater into our creeks and streams.

We’re building a $1.2 billion wastewater tunnel across central Auckland called the Central Interceptor (CI). We also have other projects in the western isthmus, such as separating the stormwater and wastewater pipes. Together, the Central Interceptor and our western isthmus strategy will significantly reduce wastewater overflows in the area.

Main Tunnel:
The Central Interceptor (CI) tunnel is 4.5 metres in diameter and will run for 14.7 kilometres from Grey Lynn under central Auckland and the Manukau Harbour to Māngere. The tunnel will lie between 15 and 110 metres below the surface. Along with two smaller link sewer tunnels we are building, the main CI tunnel will collect wastewater from the existing network and take it to the Māngere Wastewater Treatment Plant.

Central Interceptor Construction sites:
We have 16 construction sites along the tunnel route.  The visit will be on Mangere Pump Station.

Te Toka Tumai | Auckland is the largest Hospital in New Zealand and is one of two major trauma centres serving the Auckland region. Over 100,000 patients are seen across the Auckland City Hospital and Starship Hospitals emergency departments making the Auckland campus one of the busiest in Australasia. In the case of an emergency there is no doubt this is a critically important facility to remain operational.  

The new Central Plant building that this project relates to will house essential services including power, water, chilled water, medical gas, and diesel to service the Te Toka Tumai campus. It is a key piece of infrastructure to enable the wider campus to function.  

Due to the critical importance of the Central Plant building to enable the campus to function, coupled with the importance of the hospital to the wider Auckland community it supports, the facility is being designed to a very high level of resilience as an importance level 4 structure with a 100 year design life. It is a concrete framed structure for improved durability and on triple friction pendulum base isolators for improved seismic resilience. 

The brownfield site is home to a live 24/7 hospital environment and is on a congested and relatively steeply sloping site. It is a very complex environment to build such a major piece of infrastructure through that has required considerable planning and a collaborative and competent team to implement. 

The Central Plant and Tunnel Project comprises of establishment of the following key components of new buildings, services tunnel and associated infrastructure for Te Toka Tumai and is the largest project within the Facilities Infrastructure Remediation Program to replace and upgrade critical infrastructure at Auckland City Hospital, Starship Hospital and Greenlane Clinical Centre: 

• A new 240m long 4m wide x 3.5m high (internal clear dimensions) service tunnel network linking existing Building A01 plantroom basement to the new Central Plant Building. The works include large diameter retaining piling, bracing, deep excavation and large in-situ reinforced concrete sections. 
• New Central Plant Building (A40) spanning 6 levels, 5230m2 and housing major new electrical, mechanical, hydraulic and medical gas central plant and associated distribution infrastructure. The building will include one floor for offices, two lifts and a mix of curtain wall and precast panel facade. The building has piled foundations ranging from 7.5m to 26m and also includes double-height spaces for the large chiller and generator halls, plus a roof level double-height cooling tower enclosure. 
• Construction of critical services infrastructure that will replace ( or enable phasing out of ) existing aged/ end-of-life plant, while provisioning the campus for anticipated growth in demand in the next 50 years