Groundwater decrease and contamination around subway tunnels in a coastal area of Busan City, Korea

Groundwater decrease and quality deterioration are common phenomena at coastal areas with subway tunnels in the world. This study investigated the problems in Busan Metropolitan City of Korea, using the integrated techniques of hydrogeological, hydro-geochemical, geostatistical, multivariate statistical and isotopic analyses. Groundwater around the subway was heavily discharged, and the groundwater level around the subway was fallen to −25.3 m on basis of mean sea level. The deep drawdown of groundwater level spurred the induction of seawater and salinized river water toward the inland area, and the groundwater was contaminated around the subway. This study identified that groundwater-level largely descended due to the excessive utilization of groundwater and the severe groundwater discharge from the subway tunnels, and that seawater and salinized river water intruded the inland groundwater and contaminated the groundwater around the subway. It is considered that this study will contribute to the investigation for the causes of groundwater decrease and contamination around subway tunnels in the worldwide metropolitan cities as well as the Busan City of Korea.