The Seoul metropolitan city government concluded that the reduced water level in Seokchon Lake in southeastern Seoul was mainly due to the construction of Subway Line No. 9 and the new Lotte World Tower.
But it said the construction works had no direct causal relationship with sinkholes found since last year near the lake. The city government announced on August 6 the results of investigation commissioned to the Korea Rural Community Corp. in August last year.
Seokchon Lake is an artificial reservoir created when the city government reclaimed the wetland near the Songpa River, a tributary of the Han River. For about two years between October 2011 and October 2013, the lake's water level fell precipitously. The average water level of the lake was 4.68 meters in 2010, but it declined to a low of 4.17 meters in 2013.
The city government explained, "During this period, large-scale construction projects were under way that caused the groundwater to seep out in addition to the natural seepage." During the two-year period, as many as eight construction projects were undertaken near the lake, including the subway line and the Lotte World Tower.
The city government also said that according to a simulation test the rate of water loss is likely to slow down and the nearby groundwater level would recover to the previous level once the construction on the tower and the subway are completed.