Why Monitor? 

The role of environmental monitoring in construction in the UK has become more and more important in the last 10 years. This is partly due to legislation related to planning and the advances in available technologies in power, communications, sensors and the use of visualisation platforms. At the present, there are no definitive best practice guidance available to the construction industry for the placement, use, setting of trigger levels and interpretation of sensors measuring vibration, noise, dust and other parameters. This has led to varying levels of quality as to how the sensors are deployed and the reasons that they are deployed on construction sites. 

Simon Perry, Sigicom, and Gary Evans, PC monitoring, have set out to explore the growing requirement for monitoring of environmental effects of construction alongside the more established structural and geotechnical monitoring. They look at the current legislation, standards, guidance and provide an example of how best practice has been used. They also explore the challenges that have been encountered due to the way that specifications have been generated based on the current available standards, ideas and beliefs related to environmental monitoring.

Noise Monitoring

It is common practice that the noise limits are set either by the Local Authorities or on a project level for major infrastructure works. This practice has developed over time and been led by the following legislation and guidance.

Noise from construction activities was first introduced to the UK by the Wilson Committee presented to parliament in 1963 which went on to inform the Advisory Leaflet 72 (AL72) in 1968 which was subsequently revised in 1976 which proposed fixed noise limits based upon empirical evidence. The Control of Pollution Act 1974 provided legal mechanisms to control and manage noise from construction activities in Sections 60 and 61 (S60 and S61). 

S61 provides a mechanism for prior approval of works as an alternative to S60. Using this method, the contractor can apply to the Local Authorities for approval of their proposed method of works identifying the BPM to be applied, once approved as long as the agreed methods are used works can proceed uninterrupted.

It is now common to include detailed noise predictions in S61 applications. Major projects in built up areas typically follow the S61 route. This legislation is still in force, there is no explicit requirement for monitoring, however, this is likely a reflection of the technology available at the time of writing. It is important to consult the Local Authorities before submitting a S61 application, for example the City of London (2019) “does not advise the use of Section 61 consents but it does support a system of prior agreement on similar lines, as this allows a much more flexible approach of greater benefit to the Contractor”.

S60 provides the Local Authority with the necessary powers to impose noise limits and Best Practicable Means (BPM) upon construction activities if they are considered to be unacceptably noisy. In these situations, a stop notice can be served requiring all works to stop until appropriate actions have been undertaken as stipulated.


Noise Monitoring

What is noise?

Further guidance on the management and control of noise arising from construction sites is provided in BS5228 – 1. This was first published in 1975 and has most recently been revised in 2009. This document provides guidance on the determination of BPM, different mitigation methods as well as three methods for setting noise thresholds; one based upon the absolute levels set out in AL72 and two based upon the pre-existing ambient noise levels. 

Vibration Monitoring

Vibration arising from construction impacts both the human receptors and surrounding sensitive structures. These are generally considered separately, however, it should be noted that the human response to vibration is in part linked to the perceived risk of structural damage.

BS7385 provides guidance on the level of vibration at which damage may occur in structures. It sets out the factors to be considered and provides two guidance lines for the onset of cosmetic damage; Line 1, for reinforced structures, a fixed limit of 50mm/s PPV (Peak Particle Velocity) and Line 2 for unreinforced structures, starts at 15mm/s PPV increasing to 50mm/s PPV at high frequencies to reflect the sensitivity of these structures to low frequency vibration.

The above limits do not describe the onset of human response to vibration. Guidance for this is provided in two standards BS5228-2, which provides guidance on the likelihood of complaint in terms of PPV see Table 1 below, and more recently some major projects have begun to reference BS6472-1.

You can see from Table 1 that the levels at which complaints will begin to occur are significantly below the thresholds for possible cosmetic damage to buildings as such these levels typically form the basis of project vibration limits. Utility assets owners such as Thames Water and BT Openreach prescribe a PPV limit of 10mm/s to 15mm/s. Whilst, rail asset owners have a limit of only 5mm/s.


Vibraton Monitoring

What is the right way to measure vibrations?

BS6472-1 considers vibration as a dose value, Vibration Dose Value (VDV). This measures the overall vibration dose received by the human receptor to vibration across a day (07:00 – 23:00) and a night time (23:00 – 07:00) period. This has been used when considering vibration from sources such as rail in the planning process, although, this is a good descriptor of human response across a day and night to vibration the practicality of monitoring this in occupied properties limits its application in practice.