The most significant element of the municipal landfill is storage yard leak-proof assurance, which reduces the negative influence of waste on the environment. Tightness is achieved by means of independent protective barriers in the form of geological barriers, artificial sealing layers, mineral soil liners and covers, and sidewall sealing. Some years ago, construction and exploitation of landfill sites in Poland took place without any guidelines and legal regulations. Landfills, especially situated in rural areas, were quite often constructed directly on the grounds, e.g. in excavation after the exploitation of aggregate, without any protection. Examples of the municipal landfills, located in the sites of adverse geological conditions, were presented in the paper. In every case, a subsurface water-bearing layer was deposited directly under the stored landfills. An effect of existence or absence the geological barriers on the groundwater quality was carried out. In the water samples following indicators were analysed: reaction pH, proper electrolytic conductivity, total organic carbon, heavy metals (Cu, Pb, Zn, Cd, Cr, Hg), and total polycyclic aromatic hydrocarbons. In all the tested landfills, higher concentrations of groundwater pollution indicators were found in landfill monitoring wells located on the outlet of these waters, in comparison to the landfill monitoring wells located on their supply. In the case of the landfills situated directly on the soils of high hydraulic conductivity, the indicators of negative influence of deposited landfills increased even after the closing of the landfill sites. Subsurface water-bearing layer is a kind of "indicator" giving information about the harmful effect of landfills on the environment, and the need to take remedial actions.

DOI: https://doi.org/10.3846/enviro.2017.063