Written scheme of investigation: what it must contain

A written scheme of investigation is the document that turns an archaeological planning condition into a programme of work with a start date, a method and an end point. It is written by the archaeological contractor you appoint, approved by the council's archaeological adviser, and it binds you for everything that follows, including the post-excavation work that happens long after the houses are sold.

Developers underestimate two things about it. The first is that the condition usually prevents any development until the scheme is approved. The second is that archive deposition, right at the end of the process, is now the hardest part to arrange.

What the condition actually requires

The standard condition comes in two or three parts.

Part one requires a written scheme of investigation to be submitted to and approved in writing by the local planning authority before development begins. Part two requires the development to be carried out in accordance with the approved scheme. Part three, where used, requires the post-excavation assessment, analysis, publication and archive deposition to be completed within a stated period.

Read the trigger wording carefully. A condition worded "no development shall take place" catches site clearance, demolition and even the digging of a service trench, because those are operations comprised in the development. Where you need to strip topsoil or demolish before the archaeological work can sensibly be designed, ask for wording that permits those specific operations under archaeological supervision. That is a negotiation to have before the decision is issued, not afterwards.

National policy expects developers to record and advance understanding of the significance of any heritage assets to be lost, and to make that evidence publicly accessible. That expectation is what the third part of the condition delivers, and it is the reason a scheme that stops at the end of fieldwork will not be accepted.

Who writes it and who approves it

You appoint the contractor. The council approves the scheme, normally on the advice of a specialist adviser: a county archaeologist, a shared archaeological advisory service, or in London the Greater London Archaeological Advisory Service within Historic England.

Choose a contractor registered with the Chartered Institute for Archaeologists, and check that the specialists named in the scheme are real and available. The adviser reads a lot of these and recognises a template with the previous site's research aims left in it.

Talk to the adviser before the scheme is drafted. A 20 minute conversation about trench positions and the level of investigation expected saves a revision cycle, and advisers are generally willing to say what they will and will not accept.

Where the site includes a scheduled monument, planning permission is not enough. Scheduled monument consent is a separate application to the Secretary of State, advised by Historic England, and no amount of archaeological method statement substitutes for it.

Research aims and the regional framework

A scheme that lists methods without aims will come back marked for revision.

Research aims explain why the work is worth doing. They should draw on the site-specific evidence in the Archaeological Desk-Based Assessment and on the published regional research framework for the area, which sets out the questions the archaeological community regards as open for each period.

Good aims are specific and testable. Establishing whether an enclosure identified on aerial photography is Iron Age or Romano-British is an aim. Understanding the archaeology of the site is not.

Where an Archaeological Field Evaluation has already been carried out, the aims for the mitigation stage should follow from what the evaluation found. A scheme that ignores the evaluation results reads as though nobody has looked at them.

Fieldwork methodology and sampling

This is the technical core, and it should be precise enough that a different contractor could execute it.

Cover:

1. The area to be investigated, with a plan showing trenches or strip areas against the development layout and the levels at which work will stop.
2. The excavation method, including machine type, bucket type, supervision arrangements and the depth to which machining continues.
3. The hand excavation sampling strategy, expressed as proportions of linear features, discrete features and structures.
4. The recording system: context recording, plans and sections at stated scales, photographic record, survey control.
5. The environmental sampling strategy, including bulk sample sizes, the circumstances in which samples are taken and who processes them.
6. Finds retrieval, on-site conservation, storage and the treatment of unstratified material.
7. Contingency arrangements for unexpected discoveries, including who is notified and what happens to the programme.

Add health and safety and the position under the Construction (Design and Management) Regulations 2015, along with any contamination constraints from the ground investigation. Archaeologists working in a live construction site need the same controls as anyone else, and the adviser will look for evidence that the point has been considered.

Human remains, finds and the legal add-ons

Three legal regimes sit alongside the planning condition and each needs to be named in the scheme.

Human remains cannot be removed without authority. Exhumation from a burial ground normally requires a licence, and the scheme should identify the route to be followed, the standards for excavation and recording of remains, the arrangements for analysis, and what happens at the end, whether reburial or retention.

Objects of gold or silver, and certain groups of coins and prehistoric metalwork, are potentially treasure under the Treasure Act 1996 and must be reported to the coroner within the statutory period. The scheme should state who reports and when.

Ownership of the remaining finds is a matter for agreement between the landowner and the receiving museum, and the usual arrangement is a transfer of title to the museum so the archive can be accessioned. Sort that out at scheme stage rather than at deposition stage.

Post-excavation, archive and the museum problem

Fieldwork is often the shortest part of the programme.

After it comes assessment, which reports what was found and what analysis is justified, followed by an updated project design, then analysis, then publication at a level proportionate to the results. Everything is recorded on the national online index for archaeological investigations so the work is discoverable.

Then the archive. This is the part that goes wrong. Museum storage across England is under real pressure, and some museums have closed to new deposits entirely. A scheme that names a receiving museum without a confirmed accession number and a written agreement to accept the archive is storing up a problem, because the condition cannot be discharged until deposition is arranged.

Ask three questions before the scheme is approved. Which museum will take it. Has an accession number been issued. What is the deposition charge, and who is paying it.

Where a building rather than a buried deposit is affected, the equivalent output is a Historic Building Recording to the appropriate level, and the same archive questions apply.

Discharging the condition without stopping the build

Programme the archaeology as a construction activity, because that is what it is.

Four things keep it off the critical path.

Do the evaluation before the application where the desk-based assessment shows real potential. Knowing what is there before determination lets you design around it, and mitigation in situ by preserving deposits under open space usually costs far less than excavating them.

Split the condition. Ask for fieldwork and post-excavation to be dealt with separately, so that the build can proceed once the fieldwork is complete rather than waiting for publication.

Give the adviser the notice period the scheme requires before work starts, and build the monitoring visits into the programme.

And allow contingency. Every experienced developer has a story about a well, a cellar or a burial found on the last day of the strip. The scheme should say what happens when that occurs, so that the answer is a procedure rather than a negotiation.

Enter your postcode on PlanScope to see which heritage and archaeology documents your site is likely to need.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. Archaeological work is normally expected from a suitably qualified and registered author. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.