Environment


Environmental impact

This section provides information on how the project developed to minimise any adverse affects on the local environment.

Noise & Vibration

Environmental protection

The location of the Busway project presented a number of environmental challenges. The project works were located adjacent to a number of sensitive habitats. The Hillcrest Creek, that runs through the centre of the southern part of the project discharging to the Waitemata Harbour via Shoal Bay, is home to a number of threatened shore birds species. In addition, various water courses, a remnant of native bush and residential properties, schools and rest homes all lie within or very near the work area.
 
Every effort was made to ensure as little impact as possible was made on the environment throughout construction.
 
Below are examples of the measures taken to protect the natural environment:
 

Noise & vibration

Noise is almost always a challenge when building a major roading project close to residential areas. For the busway project, ‘noise’ was defined as either:
  • Short term construction noise
     
  • Long term increases in noise from vehicles using the motorway
Transit’s noise guidelines outline the predicted noise levels in the area for the next 10 years. Noise levels are measured one metre from the most exposed façade.
 
During construction, noise was mitigated through:
  • The use of temporary noise walls.
     
  • Timing work to have as little impact on residents as possible.
     
  • Use of specific noise reducing materials.
Standards were also applied to the levels of vibration permitted. This covered two aspects of the project: the effects on people in buildings adjacent to the busway now it is built, and effects on buildings due to environmental vibration resulting from construction.  
 
Technical studies and reports indicate that the busway is only likely to increase permanent noise slightly in some areas. The increase is only likely to be noticeable by those in the immediate area. 
 
The project team has devised noise mitigation plans, approved by North Shore City Council as the regulatory authority, to deal with noise effects. 
 

Land

A large proportion of the land required to build the busway was already owned by Transit and set aside for expansion of the Northern Motorway (SH1). As well as some privately owned properties, land was purchased from North Shore City Council, the Ministry of Education and other parties.
 
Key areas included:

  • Some Westlake Girls High School land required for the busway and Smales Farm Station.

  • Land from Smales Farm for Smales Farm Station and the access road, Shakespeare Road Extension. The land was vacant and used for grazing. 

  • Land from Barry’s Point Reserve for Akoranga Station and associated access roads from Fred Thomas Drive.

  • Beecroft Park, a recreational park used for a variety of sporting activities provided some land, with no adverse affect on sporting activities. Access to the park was unaffected.

  • Land from Westlake Boy's High School northern playing fields. Transit and the school agreed on a plan to reinstate the fields now construction is complete.

  • Takapuna Normal Intermediate was affected by construction only. No land has been permanently taken from the school.

Bird life

Various native species were identified as potentially being affected by construction.
  • Northern New Zealand Dotterels
  • Variable Oystercatchers
  • Caspian Terns
In May 2003, in partnership with the Auckland Regional Council and Department of Conservation, Transit moved some 200 cubic metres of shell into the City of Cork shell bank, located alongside the motorway just south of Esmonde Road, to create new nesting sites for the dotterels.
 
In the past, some dotterel pairs attempted to breed on or near to the motorway verges around the Esmonde Interchange. The verges were not safe from disturbance or predators, but nevertheless some of the nests here have been partially successful with one or two chicks having fledged on occasion.
 
The City of Cork shell bank had been used by two pairs of dotterels during the breeding season. However, due to king high tides, which cover the majority of the shell bank on a regular basis, the area was unable to cater for more nesting sites.
 
Under the supervision of the Shore Bird Technical Working Group, five new nesting sites have been established. The creation of new nesting sites is not a physical relocation of the birds (which would be unlikely to succeed), but rather an inducement to nest at alternative sites through “encouragement” and “discouragement”. The new sites have been designed to entice and encourage the birds to move, and grass mowing around the Esmonde Road Interchange was stopped in the breeding season.

The conditions created by construction activities e.g. bare areas, rock and hay mulch, replicated the preferred dotterel nesting habitat. During the breeding season construction workers found they were sharing their work areas with amorous dotterel pairs! In many situations the birds were left to nest – the noise, vibration and nearby activity seem to have little effect on them. However in areas that are programme critical, mitigation to dissuade nesting activity was deployed. Methods included: “flame sticks” e.g. stakes with silver/red metallic streamers; hawk kites; and shade cloth fences to break up areas and reduce the 360 vision of nesting birds.
 

Smith’s Bush Scenic Reserve

Smith’s Bush is a reserve of remnant mature native forest on both sides of the Northern Motorway, just south of the Northcote Road Interchange. Most of Smith’s Bush is located on the western side of the motorway and is unaffected by the project.

A small section of bush (3-4m) on the eastern side was directly affected. Before clearance the project funded local community and iwi groups to come in and collect cuttings and small plants and ferns for relocation. In addition, skinks (ornate and copper) were captured and relocated. Prior to felling Ngati Whatua O Orakei blessed the area. Works were closely supervised by an experienced arborist and all significant trees were returned to the marae for carving.

Following clearance, mulch and branches where placed back into the new bush edge to create new refuges and habitats for skinks. The skinks were then released, with the help of the local intermediate school, shortly after clearance. Once completed a wind fence was erected to encourage plant growth along the new edge.

Hillcrest Creek

Although Hillcrest Creek is deemed a ‘watercourse’ as far down as Esmonde Road and not a coastal marine area, it is tidal and does have the ecological and physical characteristics of a coastal marine area.
 
The creek has been affected in several ways, mainly by new structures built over the creek and the increased stormwater run-off. This has a minimal effect on the mangroves.
 
During construction a 100m section of the creek was diverted to allow the culvert to be extended on the eastern side of the motorway. Before construction began, eels and other freshwater fish were relocated. None of the works at Hillcrest Creek, or in its vicinity, have had more than a minor adverse effect on the ecology of the creek.
 
All waterways were monitored throughout construction.

Stormwater

All works during construction were covered by a regional council approved erosion and sediment control plan with the site monitored weekly by a council compliance officer. Sediment treatment devices utilised on site include sediment retention ponds, silt fences and decants. In addition, erosion was reduced by staging works, reducing earthworks during the winter months, and stabilising bare areas with hay, stone or geotextile.
 
Long-term drainage and treatment facilities have been built to cater for the future. These controls ensure stormwater discharges do not have any adverse ecological effects. This is particularly the case with flows discharging to Shoal Bay. The Bay is well flushed, as it is exposed to wind and wave action, which rapidly disperses pollutants from the upper shore area. Discharges into the more sheltered inlets of Shoal Bay are more problematic. However, the only inlet to receive additional stormwater is Hillcrest Creek.
 
In the Hillcrest Creek to Northcote Road area, major pipes were relocated as part of long-term treatment of sediment going into the creek. The project incorporated the joint building of a treatment plant by North Shore City Council and Transit New Zealand.
 
Between the Exmouth Road footbridge and the Tank Farm culvert, an improved stormwater system has been built as part of the solution to a major settlement problem under the existing motorway and new busway. The new stormwater system will be a long-term solution to the soft marine mud that causes settlement on drainage.
 
A new stormwater treatment system near Smales Farm Station takes increased discharge and exiting discharge from Smales Farm and Westlake Girls High School into the Wairau Creek.
 
Culverting open drains at both Tristram and Sunnynook presented challenges due to the lack of room to divert flows. Before construction began, experienced sediment control consultants and the regional council sediment control team met to discuss methodologies and mitigation. As a result, fish were safely relocated and vegetation disposed of in liaison with the biosecurity team.

Ground conditions

Some of the new structures on the busway were built on or over soft foundations. Marine mud was being taken into consideration as, if not allowed for, had the potential to cause long term settlement issues. At Onewa Road Interchange lightweight polystyrene fill has been used to compensate for soft foundations. This is the first time it has been used on a project of this size in New Zealand.

Lightweight fill was also used in the Exmouth Road footbridge and Tank Farm culvert area, which also has long-term settlement problems due to soft foundations of marine mud.

Two link roads, Fred Thomas Drive and Akoranga Station, were both built across the old Takapuna landfill. In order to make the landfill suitable for a road, the project team used ‘dynamic compaction’. This process involved a big block of concrete being dropped repeatedly from a height onto the landfill to compress it and prevent future settlement and subsidence.