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Waar graaf ik mijn proefsleuf? De ontwikkeling van een beslissingsondersteunend model voor locatiebepaling van proefsleuven

To dig or not to dig? Improved strategies, logic and decision support for selecting test trench locations 

Paulina Racz, PDEng trainee University of Twente, department of Construction Management and Engineering

Figure1. Test Trench (in Dutch: proefsleuf)

The underground space is increasingly busy. The subsurface contains not only precious fauna, flora, and archeological findings but also many cables and pipes. For modern city engineers, it is, therefore, challenging to conduct their work in a way that will not damage underground infrastructure. Data from the Dutch Kadaster (Cables and Pipes Information Agency in the Netherlands), shows that 33,000 damages to underground utilities were reported in 2015. Only the direct costs of this damage are up to 30 million euro. 
To avoid damages, excavation processes must be preceded by the exact confirmation of the location of utilities. They, therefore, use utility maps (KLIC-tekeningen) and detection tools to address the question: To dig or not to dig? However, those tools do not guarantee absolute certainty since some utilities can be located inaccurately on maps, or may be missing completely. Also, detection tools may show incorrect information due to positioning failures, and difficulty of locating utilities in all soil types. To cope with these problems, test trenches (Figure 1) are dug to update or confirm (the accuracy of) underground utility information. 
The combination of techniques such as, maps analysis, detection systems and test trenches can decrease the risk of damage. Practice shows, however, that test trenches are often located randomly based on the personal judgment of individuals. Unquestionably, the experience of these specialists is an important asset in the decision-making process. It should, however, be used correctly to determine a suited location for a test trench. To date, such knowledge is not used systematically adequately. 

University of Twente, Reggefiber and other partners created the ReDUCE program (Reduction of Damage to Utilities and Careful Excavation; Dutch: ZoARG). Within this program, many projects are centered on careful excavation approaches. My project is part of this program and is entitled, Improved strategies, logic and decision support, for selecting test trench locations. It focuses on the problem outlined above.
The aim of my work is to develop a Decision Support System (DSS) that helps make faster and more reliable decisions about the location of a test trench. I started my project in November 2015 and I plan to finalize it by November 2017. During the first year, I conducted several interviews and workshops (see Figure 2) to gather data, identify problems, specify requirements, and to study the designers’ and contractors’ behavior. 
First results indicate multiple strong and weak points of the current practice. Weak points are, for example: (1) insufficient or incorrect information on utilities maps, (2) differences between required number of test trenches, (3) incorrect risk assessment, (4) difficulty in dealing with large amounts of data, (5) misunderstanding between contractors and (6) insufficient use of experience. While developing the DSS I will, therefore, focus on the consequent elements: (1) data collection, (2) risk assessment, (3) experience sharing, (4) visualization and (5) multi-criteria analysis. Improvements of those elements hopefully help designers and contractors to make informed decisions about the location of test trenches, and ultimately help reduce the number of excavation damages.