In this diploma paper the subdrilling technology called Horizontal Directional Drilling – HDD is presented. In the Slovenian region it is increasingly used for carrying out boreholes as an alternative to classical constructions with tunnelling which are also presented in continuation. HDD technology is presented on three different projects which were carried out for three different sewerage systems: gravity, pressure and vacuum. With the mentioned sewerage systems of drainage also basic features and their operating principles are described.
When carrying out drainage sewerage system by using HDD technology different conditions have to be fulfilled to carry it out. The main assumptions for a HDD borehole are an acceptable drilling radius depending on the borehole diameter, the geological soil formation, the types of built-in pipes, an adequate area size for setting up the drilling equipment, a minimum borehole depth and the existing infrastructure. In the final part all three sewerage systems were compared in several sections which essentially influence the choice of the system. Sections, such as the diameter of the built-in pipeline, the level of the groundwater, water tightness, minimum falls, investment and operation costs as well as the complexity of the work performance were compared. Furthermore, a comparison of costs between classical construction and HDD technology was prepared based on the work performances on the projects. So findings were established which help to choose the more optimal and adequate work performance for each particular sewerage system.