ABSTRACT
Immersed tunnel proposals are sometimes erroneously dismissed or disregarded in favor of other forms of waterway crossing because the construction techniques and methods to mitigate environmental impact are less familiar or not fully understood. In this chapter, the various environmental impacts that can arise are discussed along with the methods that are usually adopted to mitigate against them. An immersed tunnel is intrinsically no worse or better than any other form of crossing. The issues will be different compared with bridges and bored tunnels and, depending on the specific site and project circumstances, one type of crossing will be favored over another. The key to making the decision as to which is right is dependent on fully understanding the issues for each so that a fair and balanced evaluation of the options can be made.
