Information Update on S2S Sea Defence Wall

27 Aug 2015

The following information is an update from Dublin City Council regarding the construction of the sea defence wall as part of the S2S Interim Scheme. The information has been provided by the Elaine Mulvenny Assistant Area Manager for Dublin City Council, following a number of queries from residents. 

The S2S project is an interim scheme comprising elements of two projects, the Dollymount Promenade & Flood Protection Project (DPFPP) and the North City Arterial Watermain (NCAM), both of which have planning approval from An Bord Pleanála. Subsequent to the planning approval by An Bord Pleanála, of the DPFPP in December 2011, Dublin City Council (DCC) and the National Transport Authority (NTA) received Part 8 Planning approval for an Interim scheme in May 2013.

The scope of works includes the construction of two new sections of retaining wall and improvements to the existing sea defence wall. These works include height adjustments to the existing sea wall to ensure a statutory minimum level of flood defence is provided, the 200 year tide level plus an allowance for global warming sea level rise to the end of the century. 

A brief description of the adjustments to the wall heights are detailed in the bullet points below:

  • Wooden Bridge to Seafield Road East JunctionThe first 25m of existing sea wall will not be adjusted in height. The section north of the 25m will be raised slightly but will not exceed the level already in place for the first 25m of the wall. The wall height adjustment varies from 30cm to 45 cm. The height of the new wall will be approximately 62.5cm above the completed footpath.
  • Seafield Road East Junction to Dollymount Avenue JunctionThe height of the southern section of wall along this section will be adjusted upwards with a maximum height increase of 27cm above the existing sea wall height. Along the existing green area where no sea defence wall currently exists, a new sea defence wall will be constructed adjacent to the lagoon and an amenity space created. This new wall will have a height of approximately 56cm above the completed footpath level. The new sea defence wall ties in with the existing sea wall just north of the existing pump house and the new wall will tie in at the same height as the existing sea wall already in place opposite Dollymount Avenue. 
  • Dollymount Avenue Junction to Mount Prospect Avenue JunctionThe southern section of wall (incorporating the access point to the lagoon) will be adjusted upwards by up to 20cm to the location where there is an existing height change in the existing wall opposite 411 Clontarf Road. The existing wall height will be maintained from this point North to Mount Prospect Avenue. The 300m section of existing wall is approximately 80cm above the existing footpath and this will be reduced slightly once works are complete.
  • Mount Prospect Avenue to St. Anne's Carpark

The existing road carriageway level alongside St. Anne's Park is lower than the existing Clontarf Road south of Mount Prospect Avenue. Therefore, the existing sea wall adjacent to St. Anne's Park will be adjusted by up to 70cm to provide the proposed level of flood protection. At the northern end of the section of works, a new sea wall is currently being constructed. Once completed, the height of this section of wall will be approximately 85cm above the finished footpath level. Due to the existing incline on the James Larkin Road at this bend and the fact that the wall has yet to be backfilled and the footpath completed; the current height of the wall appears greater than what it will be when the works are completed. 

The existing road pavement levels will also be altered upwards by approximately 2-4cm, which will to some degree mitigate the increase in the seawall height. As can be seen from the heights of the wall above the proposed footpath level the height of the completed wall alongside St. Anne's Park will appear higher than the completed sea wall south of Mount Prospect Avenue due to lower road levels alongside St. Anne's Park.