Fugro's South Coast survey is done — now EirGrid has to turn seabed data into a deliverable grid

Fugro has closed out the 2026 marine and coastal survey campaign for EirGrid's Powering Up Offshore – South Coast programme: close to 70,000 survey hours over 2,337 km of maritime area, covering the 900 MW Tonn Nua offshore wind area off County Waterford and other potential south-coast projects. The data feeds engineering, environmental and planning assessments for offshore substations, subsea export cable corridors and onshore grid connections.

The completion is a routine milestone in itself. What makes it worth reading is the sequencing: the TSO's enabling studies are landing at the same time as a twelve-week public consultation (to 8 December 2026) on connection options, in a market where the last offshore auction cleared with no competition at all. EirGrid is effectively deciding route and landfall in public while the seabed evidence that constrains those choices is still being interpreted.

The survey is no longer reconnaissance

Comparing the two phases is the most informative number in the announcement.

(Intensity figures are my calculations from the reported totals; the two phases use different units — man-hours versus survey hours — so they should be treated as indicative, not a like-for-like benchmark.)

Even allowing for that caveat, the shift in labour per kilometre is roughly threefold. That is consistent with a programme moving from broad-area reconnaissance — widely spaced geophysical lines over a large search area — to high-resolution work on narrowed corridors and substation footprints: dense side-scan and sub-bottom profiling, magnetometer runs for unexploded ordnance and archaeology, geotechnical sampling and CPTs for foundation and cable-burial design, benthic and metocean work. Boreholes and cone penetration tests consume vessel-days, which is where survey hours go when the survey stops being a map and starts being a design input.

It is also worth noting that the 6,107 km of the two phases combined (2,337 km in 2026, 3,770 km in 2025) is not a measure of unique area surveyed. Overlapping, differently resolved coverage is exactly what staged site investigation looks like.

Two platforms says more about the electrical design than the press release does

EirGrid's own programme documentation specifies two offshore substation platforms within Maritime Area A (Tonn Nua) in the South Coast Designated Maritime Area Plan, linked to landfall by offshore transmission cables, with new onshore substations, underground cable connections to landfall, and loop-ins to the existing transmission network in Cork and Waterford/Wexford.

Two platforms for 900 MW is a design hint. A single HVDC converter pair would normally be the answer if the export distance pushed you to direct current; a two-platform configuration is the classic arrangement for HVAC export with the capacity split across two substations and two cable systems, providing redundancy and reducing losses on each circuit.

That is an inference, not a stated fact — neither voltage level, technology nor MW split has been published in the material available. But it matters downstream: HVAC export at 220 kV means two three-core cable orders rather than one converter station pair, a different onshore footprint, and a completely different steel and fabrication demand profile. European 220 kV export cable capacity is among the tightest links in the offshore supply chain, which makes the technology decision a scheduling question as much as an engineering one.

A seven-year framework built to straddle the investment decision

The commercial architecture is equally revealing. Fugro was appointed under a seven-year framework agreement for South Coast site investigations — if it began in 2025, it runs to roughly 2032 — while FID on Tonn Nua is anticipated around 2031 and first power in the mid-2030s.

The framework therefore spans the entire pre-FID development period and reaches the cusp of construction. That is a deliberate choice by EirGrid: a single multi-year geoscience contract covering survey, geotechnical and environmental monitoring avoids re-tendering at each design gate, and it keeps a consistent data set across the programme rather than project-by-project studies in incompatible formats.

Fugro is also running marine mammal monitoring under a separate two-year contract — eight seabed stations with underwater acoustic sensors for cetaceans. That is a small, targeted array, appropriate to baseline and construction-noise monitoring for protected species rather than a wide-area ecological programme. It is the kind of work that becomes a condition of consent, so getting the baseline established early is a permitting strategy, not just science.

The grid, not the wind farm, is the constraint

The division of responsibility is the part the industry should focus on. The ESB–Ørsted joint venture, awarded Tonn Nua in Ireland's second offshore wind auction in November 2025, develops the generation asset. EirGrid, as transmission system operator, delivers the offshore substations, export cables, onshore substations and loop-ins.

That is Ireland's plan-led model working as designed. It also concentrates risk in one place: the developer's FID around 2031 depends on the TSO having a consented, costed and buildable connection by then. Every month of consultation slippage, landfall dispute or route change pushes into the same window the developer is using to make its investment case.

Ireland's auction record sharpens this. The first auction (ORESS 1) in 2023 cleared more than 3 GW across four projects at an average of €86.05/MWh. The second round produced a single 900 MW award. A programme that has to deliver almost one million homes' worth of power from one project on the south coast is not a portfolio — it is a single point of dependency, and the transmission infrastructure behind it has to work first time.

What to watch

The consultation closing on 8 December will show whether landfall and corridor options survive contact with landowners, fisheries and coastal communities — the categories EirGrid explicitly names as stakeholders. The next readable signals are less about survey kilometres and more about decisions: the chosen landfall locations, the export voltage and technology, and the point at which geotechnical results harden into foundation and cable-burial specifications that fabricators and cable suppliers can price.

For the metals and fabrication side, the steel content sits in the two offshore substation topsides and foundations and the onshore substation structures — none of it yet specified, and all of it gated behind design decisions the survey data is only now enabling. Fugro's 2026 campaign did not build anything. It removed uncertainty from a programme that has very little room left for it.