[en] This report has following contents: ·Estimation of vertical hydrological gradient and the leakage in the case of EL. 10 m of injection water pressure and EL. 0 m of MCT supplement water pressure ·Undertaking the groundwater flow modeling of Case 1 and Case 2, which are based on the results of MCT supplement test The results of this project have following contents: ·Case 1 : EL. 10 m of injection water head and , EL. -5 m of MCT supplement water head ·Case 2 : the same condition as case 1 except EL. 0 m of MCT supplement water head ·Calculation of water head distribution, vertical hydro-gradient and amount of leakage - (Case 1-1 and Case 2-1) atmospheric pressure of storage cavern - (Case 1-2 and Case 2-2) 2.0 kg/cm2.Abs of storage cavern - (Case 1-3 and Case 2-3) 0.5 kg/cm2.Abs of storage cavern ·Groundwater head change is not sensitive - Distribution of vertical hydro-gradient - Case 1-1 and Case 2-1: 1.5 ∼ 2.8 - Case 1-2 and Case 2-2: 1.4 ∼ 2.6 - Case 1-3 and Case 2-3: 1.7 ∼ 3.0 ·Estimated water leakage during the operation - Case 1-1 and Case 2-1: 932 ∼ 943 m3/d - Case 1-2 and Case 2-2: 812 ∼ 819 m3/d - Case 1-3 and Case 2-3: 1,022 ∼1,030 m3/d ·It is estimated that the gas tightness can be secured as 1.4 ∼ 2.6 range of vertical hydro-gradient and the expected amount of leakage may be 850 ∼ 950 m3/d (average)