Updated 9 August 2026: This article was first published in July 2024 when the Environment Agency opened public consultations on two construction-phase environmental permit applications for Sizewell C. At that point, the project was still moving through early regulatory and enabling stages. Two years later, the position is fundamentally different. Sizewell C has passed Final Investment Decision, reached financial close and is now a live construction programme on the Suffolk coast. Thousands of workers and suppliers are already engaged, major logistics and enabling packages are progressing, and environmental permitting has expanded from the original water-discharge and temporary-generation applications into a wider sequence of drainage, flood-risk, habitat, abstraction and watercourse approvals.
The regulatory lesson from the original 2024 consultations has therefore become clearer: on a project of this scale, environmental permits do not sit outside construction delivery. They directly influence how compounds are drained, where water can be discharged, how temporary power is generated, how excavations are dewatered, how watercourses are crossed and how the main construction platform is protected from flood risk. While Sizewell C's Final Investment Decision removed the biggest funding uncertainty surrounding the project, London Construction Magazine analysis shows that the construction programme still depends on a continuing chain of regulatory approvals governing temporary power, water management, flood risk, site access and environmental mitigation before individual packages can move safely into physical delivery.
Photo: London Construction Magazine / Mihai Chelmus.
By the Numbers: Sizewell C in 2026
| Sizewell C Indicator | Latest Confirmed Position | Construction Meaning |
| Generating capacity | 3.2GW | A nationally significant nuclear programme capable of supplying electricity equivalent to around six million homes once operational. |
| Target construction cost | Around £38bn in 2024 prices | One of the largest live infrastructure construction programmes in the UK. |
| Final Investment Decision | 22 July 2025 | The project moved from development and financing uncertainty into committed delivery. |
| Financial close | 4 November 2025 | The financing structure, debt package and investor arrangements were formally locked in. |
| Workers on site | More than 2,000 by January 2026 | The project is already operating at substantial construction scale, with workforce numbers expected to rise further during peak delivery. |
| UK suppliers | More than 1,000 by May 2026 | The construction supply chain extends well beyond the Suffolk site into engineering, manufacturing, logistics and specialist contracting nationwide. |
| Original temporary generator capacity | Up to 123.2MWth | The 2024 construction permit application illustrates the temporary-energy demand required before permanent site electrification. |
What the Original 2024 Permit Consultations Covered
The original article reported two Environment Agency consultations opened on 9 July 2024. The first concerned application EPR/RP3820SH/A001 for construction water discharge activities. Sizewell C proposed a network of water-management zones and effluent-treatment units with nine discharge points serving the main construction site. Those discharges were intended to manage groundwater from excavations and rainfall captured during construction, directing treated water through controlled discharge arrangements to receiving environments including coastal and inland water bodies.
The second application, EPR/GP3226SQ/A001, covered electricity generation during the construction phase before full site electrification. Sizewell C proposed both static and mobile liquid-fuel generators with a combined installed thermal input of up to 123.2MWth. Because the overall capacity exceeded the relevant regulatory threshold, the generating plant required an environmental permit. The original public consultations closed on 6 August 2024. The significance today is not the consultation deadline itself, but what these applications revealed about the scale of temporary infrastructure required before the nuclear power station's permanent systems are operational.
Sizewell C Is Now a Construction Programme, Not a Future Proposal
Since the original article was published, Sizewell C has passed the two milestones that most clearly separate a major proposed infrastructure scheme from committed delivery. The Government confirmed Final Investment Decision on 22 July 2025, committing the project to construction under a financing structure combining public and private investment. Financial close followed on 4 November 2025, including £5bn of export-credit-backed debt and a £500m working-capital facility alongside the wider Regulated Asset Base financing structure.
The Department for Energy Security and Net Zero now describes Sizewell C as an asset under construction. Its 2025/26 accounts recorded the Sizewell C asset under construction at approximately £7.8bn, compared with around £3.5bn in the previous year. That shift is visible physically as well as financially. By January 2026, Sizewell C reported more than 2,000 workers on site. Works at the Main Construction Area included installation of sheet piling for the Temporary Sea Defence and construction of a bridge connecting the Main Construction Area with the Temporary Construction Area.
The supply chain has also expanded rapidly. By May 2026, Sizewell C said more than 1,000 UK suppliers had benefited from project work, with UK expenditure approaching £5bn. The Civil Works Alliance involving Balfour Beatty, Laing O'Rourke and Bouygues Travaux Publics is positioned to deliver the project's main civil works, further demonstrating the transition from enabling activity into a much larger construction phase.
Environmental Permitting Has Expanded With Construction
One of the strongest lessons from the updated project is that environmental permitting has not disappeared because the main project received funding approval. Instead, the number and type of construction-related permit applications has expanded as physical works have spread across the main site and associated infrastructure.
During 2025 and 2026, the Environment Agency has processed or consulted on applications covering:
• construction-site water discharges;
• drainage associated with the Sizewell Link Road;
• temporary and permanent watercourse crossings;
• works within river floodplains;
• Temporary Sea Defence structures;
• surface-water outfalls;
• habitat-compensation works;
• water abstraction;
• and modifications to existing flood-risk permits.
In April 2026, for example, Sizewell C applied for a flood-risk activity permit to construct a surface-water outfall into the Leiston Drain from a Temporary Construction Area water-management catchment. A May 2026 application sought to vary an existing abstraction licence by increasing its annual abstraction allowance from approximately 101,495m³ to 219,000m³, while retaining the existing hourly and daily limits. The stated uses include process water and dust suppression.
The Environment Agency also consulted in May 2026 on a variation allowing permanent ground raising within the Leiston Drain floodplain. The proposed perimeter bund forms part of the foundations of the Main Construction Area embankments and is intended to isolate the working platform from the fluvial floodplain before further construction progresses. These are highly practical construction controls. They affect earthworks sequencing, temporary works, water treatment, drainage design, dust control and access to working areas.
Water Management Is Now a Core Construction System
The original 2024 water-discharge permit might have appeared to be a narrow environmental compliance issue. In reality, it sits at the centre of the construction methodology. A project of Sizewell C's scale creates enormous temporary water-management requirements before permanent drainage and operational systems exist. Excavations can intercept groundwater. Rainfall has to be captured and managed across large working platforms. Roads and compounds generate runoff. Earthworks require dust suppression. Water used in construction processes has to be separated, treated or controlled before discharge.
The construction problem is therefore not simply getting water off site. It is determining where the water originated, what contaminants it may contain, what treatment is required, which discharge point can receive it and what monitoring must demonstrate before it leaves the controlled construction area. That can affect programme directly. An excavation cannot always progress independently of dewatering capacity. A construction platform cannot simply discharge rainfall into the nearest ditch. A haul route or compound can require attenuation and treatment infrastructure before its drainage system becomes operational. For civil-engineering contractors, environmental permits therefore become part of the temporary works and logistics sequence rather than a separate paperwork exercise.
Temporary Power Shows the Scale of Early Construction Demand
The original combustion permit provides another useful indicator of the scale of infrastructure required before the permanent project systems are available. Construction operations can require substantial temporary electrical capacity for site accommodation, workshops, pumping, treatment systems, lifting operations, tools, lighting, ventilation and specialist plant. The 2024 application anticipated both static and mobile generators before site electrification, with a total installed thermal input of up to 123.2MWth.
That figure illustrates why temporary power on a megaproject should be treated as an engineered utility rather than a collection of individual generators. Fuel storage, generator location, emissions, redundancy, cabling, distribution, fire risk, maintenance and transition to permanent or grid-connected supplies all become programme interfaces. For contractors, it also means temporary-energy requirements have to be understood early enough to avoid construction sequencing becoming dependent on infrastructure that has not yet been permitted or installed.
Logistics Are Scaling With the Workforce
Environmental permitting is only one part of Sizewell C's rapidly expanding construction logistics system. In February 2026, the first engineering train reached the project's Ancillary Construction Area following upgrades to the Sizewell branch line. Sizewell C intends to move approximately 60% of construction materials by rail or sea, reducing dependence on HGV movements through surrounding communities. The programme is also developing large-scale worker transport infrastructure. In July 2026, Sizewell C appointed Specialist Passenger Solutions to operate park-and-ride and workforce transport services using a fleet of approximately 150 hydrogen and electric buses.
At peak construction, the project expects roughly 8,000 workers on site. Kier has separately been appointed to build the North Plaza, a 15-hectare main entrance incorporating bus interchanges, security infrastructure, delivery facilities and new internal roads supporting the transition into large-scale construction. The message for the wider construction industry is clear: a megaproject's enabling infrastructure is itself a major construction programme.
The Friction Layer: Every Major Package Has Regulatory Interfaces
Sizewell C demonstrates why major infrastructure programmes cannot be assessed solely through headline funding approvals or main-contract values. A civil package may depend on a watercourse permit. Earthworks may require an approved flood-risk arrangement. Excavations may depend on licensed abstraction and discharge systems. Access routes can require ecological mitigation. Temporary power may need environmental controls before equipment is commissioned. Logistics compounds can require new drainage, security and transport infrastructure.
Each interface can sit on the critical path even where the wider project is fully funded. That does not mean environmental regulation is inherently causing delay. In many cases, early permitting can reduce later programme uncertainty by defining the conditions under which construction can proceed. The stronger delivery model is therefore to integrate permits into design and construction planning rather than treating them as approvals to be obtained after the methodology has already been fixed.
This principle also applies far beyond nuclear construction. Water discharge, temporary power, flood-risk activity, dust control and ecology increasingly shape the mobilisation of major UK infrastructure schemes before the permanent asset itself begins to dominate the site. The full contractor implications, sequencing risks and mitigation strategies are included in today’s London Construction Magazine briefing.
Evidence-Based Summary
The Sizewell C article originally published in July 2024 covered two Environment Agency consultations for construction water discharge and temporary electricity generation. By August 2026, Sizewell C has moved decisively into delivery following Final Investment Decision and financial close, with more than 2,000 workers recorded on site in early 2026 and more than 1,000 UK suppliers involved by May. The Environment Agency continues to process construction-related applications covering water discharge, abstraction, flood-risk works, drainage, watercourses and habitat mitigation. The construction lesson is that environmental permitting remains a live programme control throughout delivery: it influences dewatering, temporary power, earthworks, drainage, logistics and access even after the project's financing and strategic approvals are secured.
Source Context & Editorial Update
This article was originally published on 9 July 2024 and substantially rewritten on 9 August 2026. The original report concerned two public consultations opened by the Environment Agency on construction water-discharge application EPR/RP3820SH/A001 and construction-phase generation application EPR/GP3226SQ/A001. The original applications were checked against the Environment Agency's July 2024 consultation announcement and the associated permit records.
Current project status was checked against official UK Government Sizewell C documentation and current Sizewell C project updates. Final Investment Decision was confirmed in July 2025 and financial close in November 2025. Current environmental permitting was checked against Environment Agency applications published during 2025 and 2026, including surface-water, flood-risk and abstraction proposals. Permit applications or consultations described in this article should not be interpreted as granted permits unless the Environment Agency has published a corresponding decision.
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
