EN
The multi-annual research cycle aimed to analyse the impact of a local, point source of pollution, the now closed municipal waste dump, on the quality of underground waters in this area. The waste dump was located in an unsealed working of the openpit chalky clay mining spot and used for over 50 years. The Turonian and Cenomanian underground waters can be found within the sphere of the waste dump impact. The study presents the most characteristic changes in the selected physical and chemical indicators on the water quality. Even though 13 years have passed since the closure of the dump, it still remains the main point source of pollution for underground waters. The analysis of the results indicates that the Turonian-level waters, leaching the dump's bowl, are still characterised by very low quality and pose a potential threat to the lower-lying Cenomanian level, which is in part the water-bearing level for the city of Opole.