Disturbance of groundwater table by subway construction in the Seoul area, Korea

Changes in groundwater table due to dewatering of excavations at the subway pumping station in Seoul were investigated. There are total 8 subway lines in the Seoul area, the total length of 173 km; Line 1-8 are on operating. To lower the groundwater table beneath the subway tunnel, groundwater is extracted by the rate. The 1-5 lines subway network drains groundwater at the rate of 78,417 m(3)/day. The tunnels of lines 6-8 are located lower than lines 1-5 and they are needed groundwater extraction more than those of lines 1-5. Total groundwater extraction along the all subway lines is estimated to be approximately 200,000 m(3)/ day. The groundwater monitoring data along the subway route shows the line type drawdown pattern. Monitoring data on the decline of water table along the subway route and basic data on hydrogeologic properties are used to analyze the spatial disturbance range of groundwater systems due to the subway tunnels.