Coal seams in the Maritsa Iztok basin are located relatively low at 6-10 m to 110 – 120 m below the surface. The total thickness of the coalfield complex is some 35 – 40 m, divided by clay layers into three seams. The medium (second) seam is the main coal carrier with an average thickness of 15 – 25 m. The first seam has no industrial significance with its thickness of about 0.5 to 1 m.
The deposit is operated by three opencast mines - Troyanovo-1, Troyanovo-North and Troyanovo-3 – without technological pillars between them. That allows the significantly better extraction of the reserves in the basin and the implementation of state-of-the-art equipment and technology.
The horizontal coal seams allow the continuous single-board extraction method. Troyanovo-1 and Troyanovo-3 mines work in parallel on a common mining front moving eastwards, whereas Troyanovo-North works together with Troyanovo-1 but in the opposite direction - to the west -and currently the two mines pass each other by cutting the pillar between them. The total length of the extraction longwall in the three mines is about 10 km.
There are two extraction faces at Troyanovo-1 and Troyanovo-North mines, whereas at Troyanovo-3 there is one. Overburden removal in the three mines is performed at five excavation horizons by continuous operation of bucket wheel excavators, rubber-belt conveyors and belt spreaders.
The ratio of the volume of overburden deposited into the internal and the external dumps is 1:1, and the trend is to increase the volume of overburden dumped at the internal sites and shorten the transportation distance.