31. A cofferdam was constructed for excavation of the tailrace and spillway channel, and subsequently removed. 32. Cofferdams are usually employed to ensure oil or other chemicals do not leak into machinery spaces.33. A cofferdam was placed around each pier site, before excavating and then filling with concrete. 34. Consequently, a cofferdam was constructed, behind which of rock and of soil were excavated. 35. A watertight internal cofferdam , filled with cellulose, was mostly unprotected by the side armor. 36. Once the caissons were filled, water would begin to be drained from inside the cofferdam . 37. A further 160 temporary anchor piles and ties were installed to provide restraint for the cofferdam wall. 38. Tankers generally have cofferdams forward and aft of the cargo tanks, and sometimes between individual tanks. 39. The cofferdam was pumped out to expose the bedrock, upon which the masonry courses were laid. 40. So the owners dug a slip for a barge and protected it from the river with a cofferdam .
