Environmental and Social Protection
NZ Transport Agency is working to protect and enhance the natural, social and physical environment around the project area.
Environment
Despite the urban location, the natural environment is a major factor in the planning and completion of the project. The work area lies within the catchment of the Puhinui Stream and the proposed motorway route crosses the stream in seven different locations.
The Puhinui stream flows out into the Manukau Harbour and any damage to the freshwater stream can have a serious effect on the marine environment.
Considerable effort has gone into ensuring that the stream's ecosystem is not damaged by any sediment run-off that may discharge into its water way.
Careful planning has been key to the ongoing successful environmental management of the project. Engineers work with the environmental management team and use established project procedures to ensure that no detail is missed.
The result is a network of bunds, silt fences and channels that guide sediment carrying "dirty" water away from clean water such as streams, and into sediment ponds. In the sediment ponds the material is allowed to drop to the bottom and the water can continue in a clean state.
The effort to maintain the natural environment has been recognised with the SH20 Manukau Extension project winning the 2008 New Zealand Contractors Federation Auckland Region Award for Environmental Management for projects over $10 million.
The SH20 Manukau Extension project was also commended in the 'Sustainable Business' category at the 2007 Auckland Regional Council (ARC) Sustainable Environment Awards.
Landscape / Urban Design
The completed motorway will include extensive landscaping that will reflect local Polynesian and Maori cultures, as well as the native flora and fauna of the area.
Among the features will be provision for 'Te Ara O Puhinui', a footpath that will follow the Puhinui Stream from the sea to its source, providing a vital connection to the environment, for the local community.
Construction Effects
NZTA and Leighton Works (the contractor) comply with consent conditions to ensure the construction impacts of noise, traffic and dust are minimised.
The project team uses detailed management plans to deal with each impact and zone of construction. During summer, the team limits the effects of dust by dampening haul roads and open areas with water trucks.
During construction, most road closures will be restricted to night time to minimise the impact on local residents and businesses. Any closures will be notified by advertising, to ensure stakeholders and members of the public are aware of the closure.
Stormwater
Landscaped stormwater treatment ponds will treat stormwater run-off from the motorway and add landscape features.
Seven stormwater ponds are being constructed to manage run-off from the motorway and also the surrounding land owned by Manukau City Council.
