Background. The implementation of alterations to project documentation is the modification of certain solutions, assumptions or requirements. It mostly involves the verification or the specification of project documentation with regard to the actual conditions of execution or the investor’s expectations. The management of alterations in a construction project is aimed at predicting any negative consequences caused by changes in the investment process and their prevention or mitigation. Previous experience indicates that alterations to project documentation introduced during the execution of the work are widespread. They contribute to loss of time and increase in the cost of the project. For this reason, it is necessary to develop and implement an effective model for the management of such alterations.Research aims. The project manager, before construction, should be aware of any alterations to the project documentation that may have occurred during its execution, and their possible consequences. The aim of the study is to identify the causes, the structure and the consequences of alterations to project documentation with regard to water supply and sewerage construction.Methodology. The basis of the research and analyses constitute a detailed review of documentation compiled from eight projects in water supply and sewerage. Among the documents concerned, the “Records of Necessity” and “Records of Negotiations” were especially valuable for conducting the analysis.Key findings. The research conducted indicated the crucial role of the investor in the process of managing alterations to project documentation. The research revealed that proper preparation of the investment process, i.e. recruiting the best designers to prepare the project documentation, tracking changes in the nearer and farther surroundings, may significantly contribute to reducing or even eliminating many alterations to project documentation during the execution of the work
