Various methods were investigated to confirm the clogging of the drain hole of the concrete dam and recover it. The effects of drainage holes were investigated through re-drilling at the two locations.

• 오병현(K-water 수석연구원, 공학박사) | Oh, Byung Hyun
• 장봉석(K-water 책임연구원, 공학박사) | Jang, Bong Seok 교신저자