The Hans Cloos Lecture (HCL) 2024 was delivered by the first author Niek Rengers, in an abridged version, during the opening session of the 4th EurEngeo conference of the International Association for Engineering Geology and the Environment (IAEG), in Dubrovnik, Croatia, October 10th, 2024. Niek Rengers looks back on his personal involvement in more than 60 years of study, teaching, and research in engineering geology, and, with the team of authors, they focus on the main activities of the Dutch engineering geological community during the five decades since 1973. A brief description is given of the challenges of civil engineering over the past 2,000 years in once marshy land, below high tide sea level, with soft soils, and subject to flooding by the sea and the main rivers Rhine and Meuse. Dutch engineers tackled these challenges by dike construction, land reclamation in polders, and the use of pile foundations for building on soft soils. They so gathered over the ages a wealth of practical experience with soft soils. Based on this practical expertise, Dutch engineers developed a sound basis for theoretical and experimental Soil Mechanics. However, in the early seventies, it became clear that a thorough knowledge of the geological structure of the underground was indispensable for adequate geotechnical analysis and modelling. This led to the founding of the Dutch National Group of the IAEG in 1974. Since 1972 the International Institute for Aerospace Surveys and Earth Sciences (ITC) offered full year university level courses in engineering geology. The Mining Engineering faculty of the Technical University Delft followed in 1975. In close cooperation and with extensive staff exchange, both institutions have further developed engineering geological education and research programs leading to MSc and PhD degrees. A summary description is given of these developments during the last 5 decades.

Scientific literature is rather scarce as comes down on how to deal with Scope Creep (not be confused with Scope Changes) in Infrastructure Projects. However various studies and consulted practitioners in this study have pointed out that Scope Creep is often a root cause of project delay, cost overrun, and poor quality. Project Management faces considerable challenges to deal with the causes and consequences of Scope Creep. Scope Creep is by its (creeping) nature difficult to notice timely and therefore difficult to control. Scope creep deviates in this respect from 'normal' scope changes that can be identified and controlled through regular project scope change processes. In particular in Infrastructural Projects that are realized through means of fixed-price contracts scope creep can become hazardous. Therefore, this research was executed with an objective of investigating tools, techniques, and approaches which will potentially help practitioners in minimizing/mitigating scope creep causes and dealing with scope creep consequences. Based upon the identified causes of scope creep in literature, a scope creep management model was proposed for large infrastructure projects which are executed on lump sum price contracts by design and engineering consultancies. This model has divided the management processes into two groups namely planning process group i.e. project front end loading phase and monitoring & controlling process groups i.e. project execution phase. The distinction between these two groups is vital as they require different set of tools, techniques, and approaches to control the occurrence of scope creep and change. The workability and effectiveness of the developed model were validated and optimized by a focus group of experts. Further research is suggested to investigate the application of the model and its relation to project performance.