Shal low site in ves ti ga tion of Qua ter nary sands in side and in the vi cin ity of a sink hole in the for mer lig nite min ing area in Zielona Góra (west ern Po land). Geo log i cal Quar terly, 59 (2): 347-357, doi: 10.7306/gq.1193 The pa per pres ents a brownfield site in ves ti ga tion of the area where lig nite was for merly ex ploited with an un der ground mining method. The Mio cene lig nite seams were folded by gla ciers and cov ered with a layer of highly com pacted sed i ments with sands on top. Yet eighty years af ter the ex trac tion ceased, new sink holes still de velop. The aim of this work is to de ter mine both the me chan i cal pa ram e ters of soil in the area of sink holes and the changes in the val ues of these pa ram e ters in duced by the pro cess of sink hole for ma tion. The ap plied meth od ol ogy in volves in situ in ves ti ga tions. Soil state and strength pa rame ters were ex am ined with the use of CPTU and DPL tests, while stiff ness pa ram e ters were de ter mined in the SDMT test. The eval u ated pa ram e ters of soil may pro vide data for nu mer i cal mod el ling of the pro cess of sink hole for ma tion and may sig nif icantly sim plify fu ture in situ in ves ti ga tions in the area where the soil pro file shows high nat u ral change ability of state. The knowl edge of val ues of pa ram e ters in a sink hole and out side it en ables eas ier dif fer en ti a tion be tween the zones of un disturbed soil and zones where sink holes formed in the past (and were then back filled) or where the sink hole for ma tion pro cess is cur rently in prog ress. Key words: sink holes, aban doned lig nite min ing, in situ test ing, soil pa ram e ters.

The paper presents history of one of the largest mines in the Lubusz Land, namely the Oskar Mine in Smogóry near Ośno Lubuskie. The mine operated between 1860 and 1945 under the name of Oskar and later as Smogóry until 1961. The paper focuses on the detailed pre-war history of the Oskar Mine, shows its mining area, location of shafts and descending galleries. Available data about the amount of extraction and employment level are presented. The paper is based on remaining German archived materials (Main Mining Office) and on Polish documents. The paper describes briefly the discovery of lignite deposits in the 19th century near Ośno Lubuskie. Underground room and pillar retreat mining used in this mine is also characterized. Complicated lignite bed structure, ­resulting from geological conditions (glaciotectonic deformation), is discussed. The geological structures is illustrated by a few geological cross-sections.

The influence of sludge on the groundwater’s quality has been shown on the bases of the agricultural exploitation of the sludge from a sewage-treatment plant. Little thickness of unsaturated zone (8.8 m) is not effective protection against the infiltration of the pollution from the surface. Unsaturated zone consist of sand of permeability coefficient k=0,68 m/h. The time of the vertical infiltration into the aquifer has been estimated at t=14,4 days. The investigations carried out during fertilization with the sludge have revealed an undoubted increase in the concentration of some ions as well as the increase in pH of the groundwater. The increase in the amount of some ions (e.g. N-NO3, SO4, Zn) as well as detergents indicates the possibility (as function of time) of reaching higher values than the ones permissible for drinking water. The phenomenon of the increase in the concentration of the particular ions will be accelerated after depletion of sorption of the soil in the unsaturated zone. The time can be estimated for not more than several years, taking into account a small area of the fertilized fields and high contents of “pollution” in the sludge (the total of the heavy metals reaches up to 1,5 g/kg)

In paper an influence of waste dump “Chrobrów” on groundwater and tributary of the Bóbr river was described. This waste dump was installed in former gravel excavation. For first 10 years it had no leak stopper and sewage water could freely infiltrate. Geological structure of the waste dump subsoil is unfavourable because garbage are directly stored on gravels with high filtration coefficient which make migration of pollutants easy. At the moment the waste dump has a leak stopper made from bentonite composite but there are still polluted groundsunderneath. In this paper was analyzed data about ground- and surface water quality from years 1994 – 2004. It was found that the quality of groundwater deteriorated, especially in years 1999 and 2002. The most worsening was noted in case of chlorides, ammonia nitrogen, sodium and potassium. Unfortunately there is no data before 1994 so there is no information about hydrogeochemical background. Increased values of all groundwater components infirst period of investigation are results of exploitation in years 1984 – 1994, when waste dump had no leak stopper.But later deterioration of groundwater quality can not be explained in this way. It should be drawn a conclusion that the seal of waste dump bottom does not work correctly. It was found that there is no negative impact of waste dump on surface water what is caused by absence of hydraulic contact between river and groundwater on investigated area.