Table 2: Rock groups of carbonate rocks (marble and limestone) with possible karstification along the twin Access Tunnels (total length of each of the two tunnel is 17.5km)

Yantang formation Baishan formation Zagunao formation SUM
East-side tunnels 4.5km 5.0km – 9.5km
West-side tunnels – 3.2km 2.7km 5.9km