Monitoring the impact of major infrastructure construction – Noise and Vibration

As development continues and the population in major cities grows, construction noise may affect a greater number of people. For these reasons, the construction industry needs to respond by appropriately managing noise and vibration issues.

Construction often generates community noise/vibration complaints despite the limited time frame over which it takes place. Complaints typically arise when the community has no clear understanding of the extent or duration of the construction. Misunderstandings can arise when the contractor is considered to be insensitive by the community even though he believes he is in compliance with local regulations. This situation emphasizes the need for early identification and assessment of potential problem areas.

In addition, community consultation is an essential part of managing noise from a construction project. As part of a community consultation strategy, neighbouring premises should be given written notification of the project. The information should outline the type and duration of works, likely noise impacts, and provide contact details for feedback and/or complaints resolution.

With the recent announcement that the East West link tunnel project has been approved by the government, numerous stakeholders are probably wondering what the impact of this construction will be.

The residents being expropriated have been quite vocal in recent weeks, and they are the first and most obvious impact of this major project. But what about the hundreds of other residents in close proximity to the construction works? How will they be impacted? This question can be asked at the start of any major infrastructure project.

For a tunnel project in particular we would consider that noise and vibration should be monitored before, during and after the construction phase. By doing so, we will ensure that we have a clear understanding of both operational and construction impacts of the new tunnel.

There is no legislation for construction noise levels in Victoria. The relevant guidelines are the Environmental Guidelines for Major Construction Sites (February 1996) and the Noise Control Guidelines Publication 1254 (October 2008), published by the Victorian EPA.

The main requirements of these guidelines are to implement measures to control noise emission from construction sites, initiate community consultation, and to restrict construction hours.

Detailed requirements for construction noise management in accordance with these guidelines will be addressed in the construction environmental management plan (CEMP) drafted by the contractor with input from an acoustic consultant.

Vibration from construction works has the potential to impact on sensitive receivers near tunnels. There are two aspects that need to be considered, human comfort and building damage.

Since human response to vibration is much more sensitive than the structural sensitivity of buildings, construction vibration impacts are usually limited to some subjective discomfort for occupants in nearby buildings. The risk of cosmetic or structural damage to buildings is only found to be due to extreme vibration levels, relative to what humans would find tolerable. Appropriate guidelines for vibration due to construction activities, based on potential effects on human comfort and building damage, are discussed in detail below.

Humans are capable of detecting vibration at levels, which are well below those causing risk of damage to a building.

Guidelines for acceptable levels for human exposure to vibration in buildings are provided in Australian Standard AS 2670.2[1]. Guidelines are given in terms of satisfactory vibration levels related to the minimum adverse comment level by building occupants. AS2670.2 provides the vibration limits for both continuous and intermittent vibration to prevent adverse comment in residential buildings.

More recently, the New South Wales Department of Environment and Conservation (NSW DECC) has adopted a dose-based approach, using the vibration dose value (VDV) as documented in its vibration assessment guideline[2] and BS6472[3].

Vibration criteria that have been set with consideration to the BS 6472 are recognised as the preferred standard for assessing the “human comfort criteria” for residential building types. The standard defines vibration limits in terms of Peak Particle Velocity (PPV) (mm/s). These values are limits that may cause loss of amenity to the occupant. BS 6472 also recognizes that higher vibration levels are tolerable for short-term construction projects as undue restriction on vibration levels can significantly prolong construction works and result in greater annoyance.

Another British Standard that contains human response criteria for construction activities and utilises the most practical unit of measurement, which is peak particle velocity is BS 5228-2[4].

The degrees of perception for humans are also suggested by the continuous vibration level categories given in DIN 4150 Part 2[5].

There is little reliable information on the threshold of vibration-induced damage in buildings. Although vibrations induced in buildings by ground-borne excitation are often noticeable, there is little evidence that they even produce even cosmetic damage (such as small cracks in plaster)[6]. This lack of data is one of the reasons why the British Standards Institution (BSI) did not provide guidance before 1992 and why there is still no International Organization for Standardization (ISO) guidance limits. It also indicates that damage solely attributable to vibrations is not common. Some European countries have provided quantitative guidance in their codes for some years.

Nonetheless, there are several standards that can be refer to.

The relevant British standard is BS7385: Part 2:1993[8]. This standard was developed form an extensive review pf UK data, relevant national and international documents and other published data, which yielded very few cases on vibration damage in structures. Part 2 of the standard gives specific guidance on the levels of vibration below which building structures are considered to be at minimal risk.

The standard states in Annex A, that, ‘the age of the existing condition of a building are factors to consider in assessing the tolerance to vibration. If a building is in a very unstable state, then it will tend to be more vulnerable to the possibility of damage arising from vibration or any other ground-borne disturbance”.

There is no specific Australian Standard referring to structural vibration in buildings. However, Appendix J of AS 2187.2 – 1993[9] recommends maximum peak particle velocities measured at the ground surface due to blasting. The lower recommended peak particle velocity is 5 mm/s. The standard states however, that structures, which may be particularly susceptible to ground-borne vibration, should be examined on an individual basis. It is suggested that in the absence of a particular site-specific study then a maximum peak particle velocity of 5 mm/s is used.

Blasting may be necessary to remove rock in some areas of the alignment. Ground vibration and airblast (also called blast over pressure) are two environmental impacts from blasting. The airblast is generally more notice able than the ground vibration. High levels of vibration transmitted through the ground and the airblast could annoy residents, or in extreme circumstances, cause damage to buildings or structures.

There is no specific guidance for noise and vibration from blasting during construction in

Victoria. However, Appendix J of AS2187.2 provides general guidance on appropriate limits for ground vibration and airblast overpressure from blasting based on limiting the human response impacts of blasting. This is expected to be below the level likely to cause structural damage.

Major infrastructure construction is part and parcel of a growing nation. There are numerous benefits including generation of employment and economic stimulus, as well as savings in travel times and minimisation of air pollution. There are however some obvious detrimental effects, such as disturbance of the public and nearby residents.

With large infrastructure projects being constructed in densely populated areas, the need for control of construction noise and vibration has become increasingly important. However, there is a practical limit to the level of control that can be implemented on most projects.

Telemetrix is able to provide advice on likely noise and vibration levels to be generated and methods of reducing these levels to comply with limits set by authorities and to meet community expectations. The firm can also provide noise and vibration monitoring services for construction projects, both attended or unattended monitoring.

Monitoring the levels of noise and vibration before, during and after the construction of these projects is an essential part of managing these disturbances. By keeping unbiased independent records of these three parameters, what can easily become an emotional argument is kept scientific and objective.

For more detailed information on environmental monitoring systems, acoustic and vibration solutions, contact Mr Xavier Delattre at Telemetrix on 0449 851 971.

REFERENCES:

[1] AS2670.2-1990 “Evaluation of human exposure to whole-body vibration – Continuous and shock induced vibration in buildings (1 to 80 Hz)”.

[2] Assessing vibration: A technical guideline, NSW DECC, February 2006.

[3] BS6472-1992 “Evaluation of human exposure to vibration in buildings (1-80 Hz)”.

[4] BS 5228.2-2009 “Code of practice for noise and vibration control on construction and open sites – Part 2: Vibration” – Appendix B.

[5] DIN 4150.2 1999 “Structural vibration —Human exposure to vibration in buildings”.

[6] Building Research Establishment (1995), ‘Damage to Structures form Ground-borne Vibration’, BRE Digest.

[7] DIN 4150-3 (1999-02) Structural vibration – Effects of vibration on structures.

[8] BS7385: Part 2: 1993 Evaluation and Measurement for vibration in Buildings: Guide to damage levels from ground-borne vibration

[9] AS2187.2 – 1993 Explosives – Storage, transport and use. Part 2: Use of explosives