## 3 Results
### Szalejow Gorny Reservoir  
Figure 18 shows profiles illustrating the depth of the Cretaceous layer (sandstone or marl) in a cross-section, based on the original investigations (D1-D10) and follow-up investigations (C1-C16). Furthermore, each point is labelled with the compressive strength (Rc) and Rock Quality Designation (RQD) values obtained at the depth of the layer closest to the roof. To illustrate the nature of the rock cores in the control survey, Figures 19 and 20 show the soil extracted at points C2 and C3 from the top of the marl or sandstone layer. Figure 17: Photograph of excavation pit wall R3, Krosnowice reservoir. Figure 18: Depth of the Cretaceous layer roof determined in the original and follow-up cross-sections in the dam body area of Szalejów Gorny [25]. As in the case of the Krasnowice reservoir, the difference in the depth of the Cretaceous layer roof in the three compared profiles is undeniable. Based on the results of the follow-up investigations, the rocks (marl or sandstone) in profiles C8 to C7 are located on average 3.46 m lower than in the original investigations, with the greatest difference of approx. 18.9 m at point C6. In the C9-C16 profile, the average is 3.01 m, with the greatest difference being 16.9 m at point C15. In this case, there is a noticeable difference between the eastern and western parts of the dam. In the former, the follow-up investigations indeed indicated a significantly deeper position of the rock formations. On the opposite side, however, the situation is reversed, with the marl or sandstone roof being located 6.75 m and 1.8 m (for points C1 and C9, respectively) above the levels determined in the original investigations. In this case, it is also important to take note of the lack of a clear boundary between the rock debris and the highly fractured marl or some differences in the interpretation of the soil type in the obtained samples. The compressive strength values from the original investigations are higher than those determined in the follow-up investigations; however, they still indicate very low rock strength in the upper zone of the layer [31]. The RQD parameter was not determined during the original investigations; it was established for the samples from the test boreholes. Highly variable, the results show no clear correlation,  
Figure 19: Rock core at the C2 borehole point, Szalejów Gómy reservoir. Figure 20: Rock core at the C3 borehole point, Szalejów Gómy reservoir. confirming the complex geological structure beneath the dam body and indicating that the roof of the Cretaceous layer may locally have both very good and very poor rock mass quality. Figures 21-23 provide an overview of selected results of the geological surveys of deposits in the Szalejow Gorny reservoir basin, categorised by two different technologies: boreholes drilled at the project planning stage and excavations serving as follow-up investigations [33; 34]. To illustrate the nature of the soil in the deposits, a photograph taken in excavation R4 is shown in Figure 24.  
Figure 21: Soil investigation results at points 1 and 2 within the Szalejów Gorny reservoir basin. Figure 22: Soil investigation results at points 3 and 4 within the Szalejów Gorny reservoir basin. Although a significantly higher number of exploratory boreholes were drilled in the basin area of the Szalejow Gorny reservoir and directly on the deposits, the compiled results of the investigations (obtained using different technologies) exhibit noticeable differences in the type of soil at given depths, as is the case with the Krosnowice reservoir. Whereas in location no. 2, the difference relates mainly to the depth of the silty loam bottom, in points 1 and 3, the presence of material contaminated with cobbles and boulders in excess of 50% was detected almost directly below the ground surface, something that was not revealed by the original measurements. Such layers are not suitable for any reasonable use in the construction of a dam body embankment.