Mitigating the impact of construction works on your project using monitoring surveys

“Any customer can have a car painted any colour that he wants as long as it is black”, Henry Ford

Belonging to the Thames Water Basin, London sits mainly on former deposits of the River Thames. The London Clay Formation is a sensitive type of soil, which particularly requires special attention through displacement and deformation monitoring during demolition and construction works. A well-known fact is that any removal of soil or application of additional loads can result in soil destabilisation. Therefore, within almost every type of demolition or construction works, the feasibility study emphasizes the necessity to implement a movement monitoring strategy in accordance with the site-specific conditions. Right from the planning stage, the monitoring strategy is one of the main concerns of the planning consultants and construction contractors.

How can we mitigate the impact of construction works on a specific project and how do we know what’s right for the project?

The answer to this question is to be provided in the early stages of the project planning and feasibility study by a specialised team of geotechnical, structural and surveying consultants who would evaluate the existing site conditions and the potential risk of the development and would make some recommendations. Based on the existing geotechnical and structural information, a monitoring regime will be recommended for the duration of the project which may be extended even after project completion. The monitoring strategy will depend on the site-specific conditions: location, soil type, existing surrounding buildings or services, be it in the vicinity of Thames Water Assets, Transport for London Assets, historical buildings or even other construction sites.

It is then our responsibility to carry out an initial assessment and clarify the scope. This can be a very challenging task as many of the monitoring specifications can be quite ambiguous. We will be looking at the site particularities, elements of the asset(s) to be monitored, access issues, type of movement and accuracy required, duration and frequency, proposed methodology, data management system and reporting, trigger levels and alerts. When all the puzzle pieces come together, we will be able to identify the most time and cost-effective solutions to meet the project requirements. The Client’s support is critical through this process which involves filling the blanks and clarifying specific requirements, as well as obtaining all the necessary permissions prior to mobilisation.

Assuming all the above information is available, we will be developing an operational strategy, which consists of selecting the appropriate monitoring system and method, mobilisation, installation, baseline observations, data processing and reporting, maintenance and service interventions, decommissioning.

How do we respond to challenges?

Monitoring strategies are designed to establish the current status and future trends, in order to predict and mitigate the associated risks. Complex monitoring schemes are to be found on large scale projects in London, comprising of environmental and movement monitoring. On a major project with high risk potential, it is vital that all the parameters are monitored continuously, regardless it’s air, noise, vibration, displacement or deformation, so that any changes or unusual variations are kept under specialised observation. It is very common that the monitoring strategies include for environmental monitoring via sensor equipment, providing real time data with permanent remote access via web based service. This enables trigger levels to be set and alerts to be received in real time when trigger levels are exceeded, which allows immediate actions to be initiated.

More information on innovative monitoring strategies will be subject to future posts.

All in all, any customer can have whatever monitoring he/she wants as long as it’s the right one for the project. Simple as that.

For further information, contact Operations Director, Clif Webb or Senior Survey Manager Georgiana Rusu

*Written by Georgiana Rusu, London Senior Survey Manager.