Decide whether the following statements are true or false according to the text.

1) A timber crib dam is made of timber bolted into cribs and filled with earth.

2) The life of timber dam is limited to 10 years.

3) Cedar, redwood, cypress are the most permanent timbers.

4) A cofferdam must be relatively low in cost but as hermetic as possible.

5) For depths over about 5 ft sheet-pile dam are commonly used.

6) A mixture of clay and sand is the worst filler.

7) The simplest embankment often requires too much place because of the large base width.

Answer the following questions.

1) What is a timber crib dam made of?

2) What does the life of a timber dam depend upon?

3) What are the most durable timbers?

4) What are cofferdams used to?

5) A cofferdam must be relatively low in cost but as watertight as possible, mustn’t it?

6) What is the simplest type of cofferdam?

7) Where can it be only used?

8) Why is the mixture of clay and sand the best filler?

9) Does the simplest embankment often require too much room? Why?

Make а short outline of the text.