Water quality monitoring during the construction of the M3 motorway in Ireland

The M3 motorway in Ireland was constructed between the years 2007 and 2010. The motorway crosses the River Boyne, which is a designated salmonid water under the EU Freshwater directive, and its tributaries. The paper describes the measures taken to mitigate any potential impacts which the road scheme might have had on the aquatic environment and the water quality of the Boyne watercourses before‐, during‐ and post‐construction. The success of the mitigation measures undertaken is assessed by: (a) comparing pre‐construction, during‐construction and post‐construction water quality data, (b) comparing measured water quality with relevant standards, (c) comparing water quality data upstream and downstream of river crossings, (d) the establishment of a pilot‐scale real‐time water quality monitoring station at the downstream end of the works before discharge into the river Boyne. The study concluded that the measures taken have been successful in minimising the water quality impacts associated with the road scheme.