The Yangyang Pumped Storage Power Plant is being constructed by Korea Electric Power Corporation in Namdae-Chun River, Korea. The Yangyang Pumped Storage Power Plant has 1000MW capacity with upper reservior, lower reservior, hydrauric tunnel and underground power plant facilities. But NGO(Non Governmental Groups) and residents are worried about the power plant construction because of some problems, as follows. (1) Namdae-Chun River is principal salmon returning river in Korea. (2) Namdae-Chun River is main water supply source of the Yangyang country. So, brief explanation of Environmental Impacts Assessment executed by Korea Electric Power Corporation, main environmental impacts and countermeasures will be introduced.