21. One of those has given way and flooded ( a ) section of the cofferdam . 22. The treasure-hunters were hampered in their efforts by an improvised cofferdam that leaked. 23. This reduces the requirements for a cofferdam during construction and the sizing of the spillway. 24. Due to a structural inadequacy, the cofferdam washed out on October 31, 1970. 25. Fieldwork was completed by May 1997, after which the cofferdam was disassembled and sold. 26. The cofferdam was winched up tightly against the ship with the assistance of Navy divers. 27. The ships were equipped with cork cofferdams . 28. One of our cofferdams has collapsed, 29. In such cases the cofferdam is fabricated from sheet steel and welded into place under water. 30. On 13 February 1912, the engineers let water back into the interior of the cofferdam .
