1, In that excavation, however, the water was not drained from the cofferdam.

2, When one of the cofferdams sprang a huge leak, it was plugged with old mattresses.

3, When the cofferdams were finished, the engineers turned to the next task-stripping the canyon abutments to expose fresh clean solid rock.

4, The canyon walls were finally clean, the abutments sculpted, the cofferdams in place.

5, It was found that the flood, coming from the modern glacier area of the source, was caused by breaking of ice-dam and coffer-dam lakes formed by blocking of river with glacier movement.