The bachelor thesis with theme of slope stability was separated in to two parts. Based on technical literature, in the first part the solving of the slope stability was described. In second part of the thesis wast theoretical knowledge applied to Assessment of the slope stability of the ash settling pit. For the first, manual calculation of assessment for slip surface had to be done. Then, manual calculation was checked by the software GEO 5.16 -- datadisc slope stability. In second step, based on slope stability analysis, water levels in dam's system were determined (allowed and critical water levels).Assessment of the stability of the ash settling pit was solved with in degrees of stability and for comparation, the assessment was solved also according to limiting states.