Infrastructure Planning Blog

This week’s entry looks at the finally announced proposals for how biodiversity net gain (BNG) will apply to nationally significant infrastructure projects (NSIPs), accompanied by a further six-month delay. It also covers guidance on archaeology and solar farms, and a Supreme Court decision about tax allowances for windfarms.

BNG for NSIPs delayed but revealed

The obligation to provide at least 10% biodiversity net gain for nationally significant infrastructure projects was consulted upon last year and at that point was delayed from the original target of November 2025 to May 2026.  Late on Wednesday 15 April, the government responded to the consultation but delayed the introduction further to apply to applications made on or after the more precise date of Monday 2 November 2026.

The consultation response document can be found here. Here is a summary of what is now proposed:

• Draft legislation will be published in May
• The regime will be consistent across NSIP types, with no special considerations. The 'Biodiversity Gain Statement', which has the status of a National Policy Statement (NPS), and has been rewritten as an appendix to the consultation response, will be formally published in May 2026.  This will apply to all DCO applications from 2 November, even those without an existing NPS applying to them.
• A smaller 'BNG boundary' within the order limits excluding 'unimpacted habitats' is to be allowed for baseline calculations, although I don't see the point in that: why do you have habitats you know are unimpacted in your boundary? Anyway, no harm done.
• I suggested in my consultation response that a two-stage process was necessary due to the use of order limits, where you don’t know where your development is actually going to go and this might mean including a huge amount of habitat that is never touched (but not known to be unimpacted at application stage). In fact, there will be a three-stage process:
  
  • Outline Biodiversity Gain Plan submitted with application.
  • Final Biodiversity Gain Plan submitted (to the Local Planning Authority (LPA), or for multi-LPA projects, the Secretary of State) post-consent and pre-commencement.
  • Where you still don't quite know where the development is going, Updated Biodiversity Gain Plan before operation to address any remaining shortfalls.
• I suggested that onsite temporary land not count as 'significant' i.e., not needing to be legally secured so that when returned it isn't restricted for 30 years. That has been taken up. The 10% gain on top will still need to be calculated and provided somehow, though.
• Many consultees suggested relaxing the "temporary land counts as 'retained' if fully restored within two years" rule. It is to be relaxed, for very low and low distinctiveness habitats only, to restoration within five years.
• The biodiversity hierarchy is to be relaxed so that onsite and offsite gains are equivalent.
• Multiple host LPAs and National Character Areas are all treated as one big area for spatial multiplier purposes.

A host of legislation and guidance will follow over the coming months, watch out for further webinars on this issue.

No Diggity

The Chartered Institute for Archaeologists (CIfA) this week published a good practice guide for archaeology and solar farms (a copy can be accessed via the CIfA website here). The guidance emphasises the need for a proportionate approach to be taken to archaeological analysis in the context of solar schemes, with a clear steer towards non-intrusive investigation except where this is insufficient to provide clarity about the archaeological potential of a site.

Here are the headlines:

• Phased Assessment: developers should use non-intrusive investigative methods early in the process, starting with desk-based assessments and geophysical surveys to identify high-sensitivity zones.
• Proportionate Evaluation: intrusive methods such as trial trenching should be targeted specifically at areas of high impact or where non-intrusive data is inconclusive. On the other hand, the guidance says: “areas of the site where no ground disturbance will occur can, in all but exceptional circumstances, be scoped out of further evaluation”. The guidance says that there could be circumstances where it would be appropriate for any or all trial trenching requirements to be moved to the post-determination stage, secured by a condition or requirement.
• Iterative Design: archaeological data should be used to inform the site layout. For example, creating "no-dig" zones or moving infrastructure away from sensitive remains can help to ensure they are preserved in situ.  Consents need to include flexibility in how and where infrastructure is sited to allow for this.
• Minimal Ground Disturbance: solar farms often have lower impacts than other permanent forms of development which are typically characterised by larger areas of dispersed, relatively low-intensity ground disturbance. In addition, piling for mounting structures will generally have limited impacts as the foundations are shallow.
• Public benefit and knowledge: the guidance states that “dissemination of knowledge gained through investigation should be woven into proposals”.  It gives the example of public rights of way located within or on the edges of solar farms, which may present options to disseminate archaeological information to the public.
• Grid connection programme: the guidance quite helpfully notes that “the process of delivering [a grid connection] is currently subject to widely publicised delays. These delays are often due to the need for broader grid reinforcement works that are outside the control of the developer of any particular solar project”. Intrusive archaeological investigations should therefore be scheduled to align with the anticipated grid delivery schedule to minimise disruption to land earlier than necessary.

Taxing provisions

Finally, there was an infrastructure-planning-related decision handed down by the Supreme Court this week. It can be accessed here. The judgment considers whether pre-construction surveys can count towards capital allowances (tax reliefs which allow businesses to deduct the cost of qualifying capital assets from taxable profits) or not – Orsted was trying to claim the allowances in relation to four offshore windfarms.

To qualify for capital allowances under section 11(4) of the Capital Allowances Act 2001, certain conditions have to be met. In this case, the key condition under consideration was whether the spend on surveys was capital expenditure “on the provision of plant”.

The court held that the connection between the spend and the plant (i.e., the wind turbines) was too remote to fall within the scope of section 11. The survey costs provided Orsted with advice about how to choose or design plant but it was not expenditure on the plant itself. If the section covered expenditure “in connection with” or “relating to” or “with a view to” the provision of plant, the outcome might have been different – but it did not.

This publication is intended for general guidance and represents our understanding of the relevant law and practice as at April 2026. Specific advice should be sought for specific cases. For more information see our terms & conditions.