Construction of river crossings on National Road Schemes has the potential to impact on sensitive river ecosystems containing protected species particularly those prone to siltation. These impacts can occur during the construction phase and to a lesser extent during the operational phase through routine maintenance activities. The NRA is encountering situations where bridge crossings are in SACs more frequently on many road schemes and this has significant implications for the planning process. A review of construction techniques and guidance for contractors as to how to avoid any pollution events would be beneficial in dealing with situations where these species are known to occur. The research will look at sensitive river ecosystems, e.g. Special Areas of Conservation (SACs), containing protected species such as freshwater pearl mussel, lamprey, and white-clawed crayfish as well as salmon spawning grounds and examine the methods of watercourse crossings construction that will significantly reduce environmental impacts on these sensitive ecosystems.
The research will examine the effects on water quality and flow regime resulting from different construction techniques. A best practice guideline document on methods of construction and their environmental effects will be produced.
The research augmented the Irish National Road Authority's watercourse crossing guidelines and fulfilled the objectives of stage 4 of the environmental integration model. A guidance document was produced that will assist in the planning and construction process and provide a useful reference for responding to ecological objections on national road schemes.