Welcome to the second update of 2015 for the Greater Dublin Drainage Project (GDD) – the development of a new regional wastewater treatment facility for the greater Dublin area.

Greater Dublin Drainage involves a new wastewater treatment plant at Clonshagh (Clonshaugh); an underground orbital sewer and two pumping stations; and an outfall pipeline discharging to the Irish Sea (1km north-east of Ireland’s Eye). The project is vital to safeguard public health, improve and protect the environment, and facilitate employment, social progress and economic growth in the wider Dublin Region.

This update contains information about forthcoming marine environment surveys being undertaken as part of the preparation of a planning application for the GDD project (envisaged to be submitted in late 2016). The project team is also holding a number of information events in Howth, Baldoyle and Portmarnock in July and further details are provided below. 

Marine Environment Surveys
Following a statutory public consultation process, a Foreshore Licence (reference 2015/02242) has been granted by the Department of the Environment, Community and Local Government (DECLG) which permits Greater Dublin Drainage to undertake investigative marine surveys in the Irish Sea in the vicinity of Baldoyle and north of Ireland’s Eye. Conducting these necessary environmental surveys will help to ensure that the GDD project is developed in a way that safeguards the quality of the marine environment, our beaches and our bathing waters.

Map of Proposed Marine Outfall for GDD Project

Marine Ground Investigations
A marine ground investigation is required in order to inform the preparation of a construction methodology for the outfall pipeline. This survey, which will assess the composition of the sea bed, involves using a jack-up platform (as shown in the image below) in order to make a number of boreholes along the route of the proposed marine outfall.  The platform will be visible from the coastline over a four week period from mid-July into August. A notice to mariners will be issued to ensure that other water users are aware of the survey.

Jack-Up Platform

Jack-Up Platform

One borehole will be undertaken on Velvet Strand, Portmarnock (using equipment similar to that shown below). This part of the survey is scheduled to take place in September (weather permitting) in order to minimise any potential impact for beach users. The survey is envisaged to take 2-3 days and the beach will continue to remain open during the survey.

Borehole Tripod

Borehole Tripod

Other environmental surveys which are taking place in the coming months include

  • Bathymetry Survey and Sub-Bottom Profiling
    These surveys will be completed over a four month period and will consist of side scan sonar surveys, seismic refraction techniques and magnetometer surveys. Side scan sonar is used to create images of the seafloor, seismic refraction is used to create images of layers below the sea bed and the magnetometer survey will investigate if there are any metallic artefacts such as from previous ship wrecks present.








  • Underwater Noise Survey
    This survey will involve the collection of underwater noise data at the outfall location in order to establish a baseline dataset.
  • Reef Habitat Survey
    A survey of the reefs around Ireland’s Eye will consist of habitat mapping using acoustic sampling, scientific divers and high resolution still photography.


  • Surface Sediment Survey
    This survey will consist of surface sediment sampling on an extended study area from Lambay Island to Howth.
  • Archaeological Geophysical Survey
    This survey will utilise bathymetry data, sub-bottom data and magnetometer data to look for the presence of any items of potential archaeological interest along the outfall pipeline route.


3D Hydrodynamic Model
The results of the marine ground investigation will be supplemented with the above suite of survey results and other completed marine survey findings to build a 3D hydrodynamic model of the marine environment. This tool will be used by the project team to inform the detailed design and construction method for the marine outfall.

Upcoming Information Events
The GDD project team invites you to attend the following forthcoming information events:

  • Wednesday 15th July Howth Yacht Club                                10am – 2pm
  • Wednesday 15th July Portmarnock Hotel & Golf Links      4pm – 8pm
  • Thursday 16th July Baldoyle Library                                  3.30pm – 7.30pm

Members of the project team will be available to provide further information and to answer any questions about the marine surveys taking place or any other aspect of the project.

As always, you are most welcome to contact the Project Team with any feedback or questions, using the contact information below.