Seawalls Groynes and Breakwaters Questions and Answers

Answer: C

Correct answer: used in the core of the breakwater enclosing it

Dredged material from the basin is generally unsuitable as armour but perfectly good as core, so it is placed inside the breakwater under the underlayers and armour. This kills two costs at once - the material need not be disposed of, and core need not be imported - and it is why the excavation and the breakwater are normally planned together as one earthworks balance.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason states the double saving. Marine disposal requires a licence, a haul to the disposal ground and the vessel time to get there; imported core requires quarrying, haulage and placing. Using the excavated material in the works avoids both, and on a large harbour the sums involved are a substantial fraction of the contract. It is the marine equivalent of balancing cut and fill on a road scheme.