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Reinforcing the Waal dike poses a possible risk of damage and inconvenience to buildings and objects in the vicinity. In order to identify the possible risks and adjust the implementation method accordingly, BouwRisk carries out the structural inventory at an early stage and a structural survey just before implementation. During the execution, the buildings and objects in the risk areas are continuously monitored in order to make timely adjustments. And this is not only done remotely.
Already since 2019, semiannual elevation measurements have been conducted by BouwRisk to assess the impact of autonomous subsidence on properties and
mapping objects. “We initially took accurate measurements of all 280 properties and 17 objects that are close to the work,” says Frenk Schaap, project manager at BouwRisk, an expertise agency specializing in environmental impact. “By doing all the necessary fieldwork well in advance of the work and repeating it every six months, a picture is obtained of the autonomous subsidence, the effect on the buildings and pre-existing structural defects.”
Based on the preliminary survey, semi-annual monitoring measurements and the nature of the work in the field, BouwRisk created a risk inventory and wrote a monitoring plan. “We then established an active and passive zone,” Schaap explains. By this he is referring to the distance from homes and objects to the locations where, among other things, the sheet pile walls are being vibrated in. “In these zones, there is a risk of damage to adjacent properties and objects, and inconvenience to residents. The properties and objects located within the active zone boundaries immediately adjacent to the work will be intensively monitored. The properties and objects in the underlying passive zone will be monitored, but at a slightly lower frequency. Because the project is being phased, we perform additional measurements in a particular cluster just before work begins. That way we always have a recent of the current state of the buildings. If damage is suspected as a result of the work, we can make a proper analysis. That is very pleasant for all parties.”
The two risk zones are continuously monitored during the work. Schaap: “Our monitoring plan stipulates that the properties located within the active zone are not only monitored remotely, but that a specialist from us is always on site during the work. This way we create a real-time interaction with the team of combination De Betuwse Waard and immediate adjustments can be made in case of excessive vibrations. At the end of the day, after the last sheet pile has been installed, the buildings are also checked for settlements. In this way we try to have a timely insight into the risk of possible damage and thus keep the chance of damage as small as possible. This makes the residents feel safe. And should damage nevertheless occur, we are the intermediary between the contractor combination, residents and the damage expert. Fortunately, we have not yet had to fulfill this role to date, and this is mainly due to thorough preparation and the fact that we are so responsive.”
With an office in Amsterdam and in Eindhoven, BouwRisk operates virtually throughout the country. “We have all the expertise in house to recognize environmental risks, analyze our measurement data in detail, advise our clients on that basis, and thereby control the potential risks. This varies from providing only architectural recordings or vibration measurements to intensive projects such as here at Wolferen-Sprok
in which we think along beforehand, advise, manage risks and monitor both before, during and after execution. Finally, we settle any damages with the damage expert,” Schaap concludes.
