Warunki hydrogeochemiczne na obszarze objętym wpływem odwodnienia złóż węgli brunatnych w rejonie bełchatowskim

Abstract

HYDROGEOCHEMICAL CONDITIONS IN AREA AFFECTED BY DRAINAGE OF BROWN COAL DEPOSITS IN THE BEŁCHATÓW REGION Summary According to the design of exploitation of the brown coal deposit, Quaternary, Tertiary, Cretaceous and Jurassic rocks will be steadily drained down to 300 m depth. In the Bełhatów area, ordinary water, i.e. water with mineralization below 1 g/dm3, occurs down to about 700 m depth (Fig. 1). Water with mineralization below 500 mg/dm3 predominates throughout the area of forecasted influence of drainage and in the zone of the designed depressional cone, except for the neighborhood of salt dome (Table l; figs. 2, 3, 4), The estimation of influence of the salt dome on natural hydrochemical background and changes in chemical composition of water pumped out of the mine is very important. Water occurring in Quaternary deposit above the salt dome does not show any increase in mineralization nor content of chlorides in relation to that found beyond the dome. Mineralization is found to be increased in water occurring below the top surface of the dome, in its direct neighborhood (at distance not greater than 150-200 m) (Fig. 1). Cap rock of the dome is characterized by very low permeability and low collector properties. Low permeability is also typical of rocks overlaying the cap. Therefore, drainage may result in infiltration of water from the cap rock but on a very small scale (in amounts not over a few m3/24 h). In suitable drainage system, the water may be drained off separately.