Highly innovative micro-tunnelling technology is to be used in the delivery of EirGrid’s Powering up Dublin grid upgrade project. The project involves the installation of underground electricity cables running between Finglas and North Wall, North Wall and Poolbeg, Carrickmines and Poolbeg, and Inchicore and Poolbeg along with the development of a new substation at East Wall and upgrades to other substations.
The Inchicore to Poolbeg circuits presented the most significant challenges. Three options for the two cables required to connect the Inchicore substation with the Poolbeg substation were presented for feedback as part of a public consultation in 2024. One of them was discounted due to the discovery of several significant technical, environmental and historical constraints.
Extensive surveys and assessments determined that a traditional trenched solution for replacement of the cables was not feasible due to the density of existing utilities in the road network along the route.
“Imagine what traditional trenching along this route in a busy congested city would be like,” says EirGrid interim chief infrastructure officer onshore Siobhán O’Shea. “We decided to construct a micro-tunnel to accommodate the two circuits. We did a lot of work researching micro-tunnels in the UK and further afield. This is the first time this has been done in Ireland. We are trying to be as innovative as possible to minimise disruption while developing the grid in a seriously congested part of the country.”
RM Block
The three-metre diameter micro-tunnel will run at depths of between 15 and 60 metres, well below any services and utilities along the route. This will also mean it can take a more direct route, shortening the 15km involved for the existing two cables to just 10.5km.
“This is a significant benefit,” says O’Shea. “Instead of a total of 30km for the two cables the micro-tunnel will be just 10.5km in length. It will carry two 220kV cables with the capability of upgrading them to 400kV to meet future demand.”
The exact route of the micro-tunnel is still to be determined. However, insofar as it is possible, the tunnel will run beneath the Grand Canal and other publicly owned green spaces to minimise disruption for people living along the route, she adds. Access shaft locations will also be chosen on the basis of least disruption to the public.
“EirGrid will continue to engage with stakeholders to determine a feasible route and will publish that route, along with shaft locations, in the coming months,” she says.
The overall project is required to upgrade Dublin’s ageing electricity infrastructure, which is reaching the end of its life, O’Shea adds. “Work must be done now to transform and modernise the city’s infrastructure so Dublin can continue to develop and thrive, while increasing the power from renewable sources. Dublin needs a strong and reliable power network, and we need to add capacity to meet the needs of the growing population and the expanding economy. The electrification of the economy will increase demand as well.”
A route has been finalised for the Finglas to Poolbeg element of the project and it is now progressing through the final step of EirGrid’s six-step process for grid development – construction, energisation and benefit sharing.
The Finglas to North Wall section of that route has been classified as exempted development and planning permission is not required. Planning permission and maritime area consent (MAC) will, however, be required for the final section of the route, connecting North Wall to Poolbeg. EirGrid is currently working with the Maritime Area Regulatory Authority (MARA) to obtain the MAC and progress this section of the route.
A route for the Carrickmines to Poolbeg element has also been finalised, and the project is progressing to the final step of grid development process. The onshore section of the route between Carrickmines and Blackrock Park has been classified as exempted development, meaning that planning permission is not required. Offshore licences and planning permission will be required for the final section of the route, which will travel across Dublin Bay from Blackrock Park to Pigeon House substation. EirGrid is currently progressing MAC and planning applications to both the MARA and to Dublin City Council to obtain the relevant statutory consents.
The next stage of the project will see the Finglas to Poolbeg and Carrickmines to Poolbeg elements handed over to ESB Networks for construction once all necessary permits and consents are in place. It is anticipated that the Finglas to North Wall section will commence construction in 2026.
For Carrickmines to Poolbeg, it is expected that a construction contract will be awarded in 2026 for the onshore element of the route, while EirGrid will continue to liaise with the MARA and other relevant stakeholders as work progresses on the offshore cable. EirGrid will provide an update on project progress in the new year.
“The proposed route for the Inchicore to Poolbeg micro-tunnel is still in development and will be published for consultation in 2026,” O’Shea says.
