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HYDROLOGY OF MEZICA (SLOVENIA) LEAD AND ZINC MINE DEWATERING AFTER MINE CLOSURE

AUTHOR/S: M. MAVC, J. PRESTOR, S. F. STRUCL
Sunday 1 August 2010 by Libadmin2009

9th International Multidisciplinary Scientific GeoConference - SGEM2009, www.sgem.org, SGEM2009 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 14-19, 2009, Vol. 2, 207-210 pp

ABSTRACT

Mining in upper Meža valley had more than 350 years of tradition. Lead and zinc ore
deposit was developed in the triassic carbonate layers on the area of 64 km2. Until 1994,
when the mining process was stopped, miners excavated about 19 million tons of lead
and zinc ore and over 1000 km of galleries and pits. A crucial aspect of the Mežica mine
was the dewatering issue.

Mežica ore deposit is developed in Triassic carbonate rocks – limestone and dolomite.
The area is of rough mountainous relief rising from 500 m a.s.l. to 2.126 m a.s.l (Mt.
Peca). The hydraulic barriers of the depression cone are well known to the northern and
southern side, where there are outcrops of practically impervious rocks. Boundary
conditions to the east and west side could not be well defined, because there is no
evident geological barrier.

The mine was excavated 250 m below the regional groundwater level at 520 m a.s.l.
Carbonate rocks are fissured and karstified. Catchment area is quite big 83 km2
extending over high mountains Peca, Mala Peca and Šumahov vrh.

A volume of 1,7 million m3 of mine galleries was excavated below groundwater level
and on the other hand a volume of 360.000 m3 of flotation mud was deposited in those
galleries.

The inflowing water would make mining impossible if not dealt with properly. The
discharge of groundwater to the mine was approximately 35 m3/min (580 l/s). During
mining under the groundwater level the inflowing water had to be pumped, so the
regional depression cone with radius between 1.300 and 5.140 m was formed.