Summary:

The construction process begins with the formulation of an idea for the project and finishes with the final commissioning. This consists of many stages, the most important of which is the construction of the buildings for the facility. This results from the specific features of the construction project, such as its long duration, its uniqueness, the seasonality of the work, dependence on weather con-ditions, and the necessity of interfering with the environment. There are many more factors, and when we consider the construction of a treatment works plus the sewerage system itself, we must also take into account any special requirements connected with their function in the local water and sewage management system. All these factors generate the risk exposure. Such risks should be included in the initial project-costing, schedule planning, and establishing the duration of the work. Events which can occur during the building of the sewage treatment works and the sewerage system have been detailed in this paper. Such events can lead to cost overruns and the prolonging of the construction phase. The method known as
expert interview was used to establish whether the pre-prepared list contained the most important sources of risk. The specialists, all with long experience in the construction of sewage treatment plants and sewerage systems, were asked for their expert opinions. Subsequent research enabled preparation of a list consisting of
24 events potentially generating risk to both costs and the construction schedule during the building of sewage treatment works and sewerage systems. Eight of these events were indicated by every expert. This shows that these events have a high probability of occurrence. The prepared list can be used to create a risk management plan for projects that are aimed at the improvement of sewage man-agement systems. It can also lead to an increased awareness of pre-existing risk factors and their consequences during construction. It should also focus attention on the necessity of a systemic approach to all issues of risk assessment and man-agement in a public works project.