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Metro Tunnel

EES assessment of noise and vibration impacts

Construction of the Metro Tunnel will result in some areas of Melbourne being exposed to noise and vibration above existing levels.

Specialist investigations assessed existing levels of noise and vibration, and considered potential impacts on people, buildings, and sensitive equipment across the proposed project area.

The impact assessment undertaken for the Environment Effects Statement (EES) demonstrated the project could be constructed and operated in compliance with applicable noise and vibration regulatory standards and guidelines.

What we heard

Key feedback relating to noise and vibration included:

  • Concerns about sustained noise and vibration near homes and hospitals.
  • Request for noise and vibration mitigation for homes near construction work sites and suggestions for potential truck curfews to reduce traffic noise.
  • Concerns about tunnel depths and impacts of vibration on property, buildings and medical equipment.

Measuring noise and vibration

Melbourne is a busy city with building construction and works on tramways, roads and other public infrastructure happening regularly. To understand the potential impacts of the project, noise and/or vibration measurements were taken at over 60 locations along the project's proposed alignment.

These measurements captured existing conditions. A range of construction activities with the potential to generate noise and vibration were assessed in the EES including tunnelling, demolition works, excavation works, rock breaking, blasting, bored piling and the construction of station boxes and other structures.

Noise and vibration impacts associated with completion and operation of the Metro Tunnel, including impacts on the wider Sunbury to Cranbourne / Pakenham rail line, were also considered.

Noise levels

Noise impact depends on the source of the noise and proximity of the receiver to it. People have varying reactions and sensitivities to noise.

The amount of noise generated by construction activities for the Metro Tunnel will vary depending on the site and the type of work being carried out. For instance, noise levels from above ground activities such as demolition and removal of excavated material will be different to noise from underground activities such as tunnelling.

Regardless of the source of noise, activities will need to meet set guidelines, particularly for works undertaken outside Normal Working Hours.

Guideline working hours for airborne construction noise

Normal working hours 7am to 6pm Monday to Friday
7am to 1pm Saturday
Weekend / evening work 6pm to 10pm Monday to Friday
1pm to 10pm Saturday
7am to 10pm Sunday and Public Holidays
Night works

10pm to 7am Monday to Sunday

Due to the scale of the project, some sites will need to operate up to 24 hours a day, seven days a week. Specific mitigation measures will be proposed for these sites. This may involve building high performance acoustic construction sheds over tunnel boring machine (TBM) launch sites, shafts and station entrances, or installing temporary noise barriers around work sites to ensure the project meets applicable noise criteria.

From time to time, certain unavoidable activities undertaken outside normal working hours may create noise levels that are considered undesirable. Early consultation with potentially affected residents, businesses and facilities will be used to determine ways to avoid or mitigate impacts. Measures may include temporary relocation for residents, if required.

Noise from construction vehicles, such as trucks, could at times impact residents living near work sites. The use of designated traffic routes, restricting the use of local roads to normal working hours where possible, and minimising night time movements will help to reduce potential impacts.

Vibration guidelines

The project has adopted the conservative German DIN 4150 guideline targets for managing the potential impacts of vibration on structures.

With more stringent targets than the equivalent British Standard (BS 7385), applying DIN 4150 demonstrates our commitment to managing impacts.

The project's stations and tunnels will be constructed using TBMs, road headers and other plant, which could generate ground-borne noise and vibration. At different stages, there is potential for this to have an impact on the comfort of people living or working near construction sites.

Humans can be sensitive to vibration and can detect vibration levels that are well below the threshold for causing any risk of damage to buildings.

At certain stages of building the Metro Tunnel, temporarily elevated vibration levels around construction, demolition and tunnelling sites may trigger additional mitigation measures.

We are committed to managing the impacts for communities and will look at further mitigation measures, which may include offering temporary relocation or respite if vibration or ground-borne noise levels are considered unacceptably intrusive.

Protecting buildings

The predicted levels of vibration indicate that no structural damage, even for older or heritage buildings, will be expected as a result of tunnelling and station construction activities.

Nevertheless, property condition surveys will be undertaken before works begin to record the existing condition of buildings and houses within close proximity of tunnels and surface works.

Hospitals, universities and research facilities contain vibration sensitive equipment. Modified construction techniques together with specific mitigation measures will be applied in these areas. For example, at Parkville the vibration assessment showed that using controlled charges may assist in limiting the duration of vibration impacts during the excavation of the station box.

Operational noise and vibration

While trains will mostly travel underground using the new tunnels, changed rail conditions near tunnel entrances have the potential to generate noise and vibration once the new line is operational.

Although the western and eastern tunnel entrances and the western turnback are located within existing rail corridors, the project will look to install noise barriers where required to ensure compliance with noise criteria.

Inside the tunnels, treatments will be applied to the rail tracks to reduce noise and vibration to ensure guideline targets are met when trains are travelling underground.

Managing impacts from noise and vibration

A number of mitigation measures have been identified in the project's EES to avoid, reduce or offset environmental impacts. These measures form the basis of the recommended Environmental Performance Requirements for the Metro Tunnel and have been recommended by specialists through the EES process.

Some of the recommended Environmental Performance Requirements to manage noise and vibration impacts include:

  • Meeting the Environment Protection Authority's guideline noise levels and other relevant noise and vibration standards.
  • Developing a relocation management framework.
  • Undertaking property condition surveys before construction begins to record the existing condition of all potentially impacted buildings, including older/heritage homes, hospitals and major institutions.
  • Implementing a communications plan to liaise with potentially affected community stakeholders and land owners regarding potential noise and vibration impacts prior to works occurring.
  • Implementing management actions as determined with potentially affected land owners to protect amenity and the operation of sensitive equipment.
  • Managing potential increases in operational noise and vibration created by additional rail services, and associated with fixed infrastructure (e.g. ventilation fans), in accordance with the relevant policies.

Terminology

Air-borne Noise: Noise may be continuous, impulsive or intermittent, and may contain high pitch or low dominating tones. The perception of noise by people can vary widely and depends upon many factors. Noise is measured by a sound meter using the decibel scale.

Vibration: Vibration is the movement of an object back and forth which occurs when it is displaced from its original position and returned to it. Vibration may be expressed in terms of displacement, velocity or acceleration. Construction vibration is often measured as vibration velocity (Peak Particle Velocity in mm/s) using an accelerometer or geophone. Vibration Dose Value is a metric used to accumulate vibration energy over a day or night time period to determine its impact on human comfort.

Ground-borne noise: Ground-borne noise is noise heard within a building that is generated by vibration transmitted through the ground into a structure. It is typically heard as a low frequency "rumbling" and is often referred to as "regenerated noise". Ground-borne noise is measured by a sound meter.