Earth filled embankment dams are the most common form of dams. They raise the standard of living and are part of our surroundings. Despite their importance and risk, they are often not generally perceived as complex engineering structures which, like the rest of the built infrastructure, are subject to ageing, external factors and other time-related processes. With good design, maintenance, and monitoring, they can remain an unnoticed part of our everyday life. Indeed, some large dams and reservoirs have been with us for decades. The task of our profession is to make sure that large dams provide the required operational safety throughout their lifetime. The work within the thesis was carried out in stages, characterized by the identification the condition and failure modes of embankment dams, which are the basis for providing the operational safety of embankments In the first part of the thesis, based on the literature review, the potential failure modes of earth embankment dams were examined and identified. We focused on the Slovenian area and considered the Drtijščica dam as a case study. We conducted visual inspections on the dam, reviewed the available technical documentation about the structure, held professional conversations with those responsible for the dam, and studied the relevant literature. This was followed by a critical assessment of the dam condition. We analysed the current status of the dam and highlighted the main risks and shortcomings for the operational safety of the Drtijščica dam. All of the above was documented and described in the thesis. Based on the review the spillway is identified as the main source of risk for the dam. Furthermore, we focused on finding suitable solutions. We propose a solution, where the existing central spillway is sealed and replaced with a new concrete spillway located on the right side of the embankment dam. The spillway is equipped with a flap gate to enable manipulation at the outlet from the reservoir. At the toe of the dam a new stilling is designed, several solutions were envisaged and explained. In the thesis we also design the connection of the overspilling water downstream to the natural bed of Drtijščica River. The steps of the execution, the phasing and placement are also explained and presented.
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