The archaeological potential section of a desk study

The potential section is the part of an archaeological desk-based assessment that the county archaeologist actually reads, because it is where the evidence turns into a recommendation. Everything before it, the historic environment record search, the map regression, the geology and the site history, exists to support one judgement: how likely is it that archaeological remains of a given period survive here, at what depth, in what condition, and over how much of the site.

Get that judgement right and the recommendation follows itself. Get it wrong in either direction and you either buy an evaluation you did not need or lose three months when the curator asks for one after determination.

What potential means and how it is expressed

Potential is a statement of likelihood, not a prediction of what is there. It should be expressed by period, with a clear term such as low, moderate or high, and it should say what is meant by the term rather than leaving the reader to guess.

The better assessments add three things to the likelihood. The expected depth of any remains, taken from local comparanda and geotechnical data. The expected condition and survival, which is where truncation comes in. And the confidence in the judgement itself, because a high potential inferred from a single antiquarian reference is a different thing from a high potential inferred from two excavations on the adjoining plot.

Vague potential is the commonest failing. A section that assigns moderate potential to every period from the Mesolithic to the twentieth century tells the curator nothing and invites a blanket evaluation condition.

Sources consulted and search radius

The evidence base has to be stated so it can be checked. The historic environment record search with its radius and date, the National Heritage List for England, historic map regression from the earliest available edition, aerial photographs and lidar where relevant, geotechnical logs and British Geological Survey mapping, records of previous investigations, and any archive material specific to the site.

Search radii are usually 500 m or 1 km, and the right one depends on the site and the period. A 250 m radius on an urban plot in a Roman town core may be more useful than a 1 km radius that sweeps in unrelated rural findspots. Agree the radius with the curator where the site is sensitive.

Say what you did not consult and why. An assessment that omits a lidar review on a rural site will be asked about it, and a sentence explaining that the area is under woodland with no available coverage closes the point. Our note on sources and consultation in an archaeological desk study covers the search itself in more detail.

Previous ground disturbance and truncation

Truncation is the strongest argument an applicant has, and it is the one most often asserted without evidence.

Real truncation evidence looks like this: as-built drawings of an earlier basement with levels, borehole and trial pit logs showing made ground to a stated depth, historic Ordnance Survey editions showing a building footprint and its later removal, records of quarrying or mineral extraction, and utility records showing the depth and corridor of services.

Present it spatially. A plan showing the footprint of the former basement over the proposed development, with the archaeological horizon level noted, does more than a paragraph. Where truncation is partial, say which parts of the site remain undisturbed, because a recommendation of no further work across a whole site rarely survives when half of it was open ground.

The reverse argument matters too. Made ground can protect deposits as well as destroy them, and a deep post-medieval build-up over a Roman horizon is a reason to expect good survival rather than none.

Expressing potential by period

Period by period is the discipline that forces real thought. Prehistoric activity is often diffuse and hard to predict from maps, so it usually rests on geology, topography and nearby findspots. Roman and medieval potential in a historic town core rests on the known street pattern and on the burgage plot layout. Post-medieval potential is usually well documented on maps and is frequently the period the developer cares about least and the curator cares about most on an industrial site.

Say where the periods interact. A medieval horizon sealed beneath a post-medieval yard surface is a different survival proposition from one cut through by nineteenth-century cellars, and that distinction changes the mitigation.

Name the specific asset types you expect: pits, ditches, structural remains, burials, industrial features, waterlogged deposits. Waterlogged organic deposits in particular change the entire mitigation strategy, because their preservation depends on the groundwater regime being maintained.

Linking potential to a recommendation

The recommendation should read as a consequence of the potential, not as a separate opinion. Four outcomes cover most sites: no further work, a watching brief during ground works, field evaluation by trial trenching or test pits before or after determination, and a design-led mitigation such as preservation in situ.

Each needs a reason tied to the section above it. Recommending no further work because the site was truncated to 2.5 m below the archaeological horizon is defensible. Recommending it because the historic environment record has no entries within the red line is not, since absence of record is not absence of remains.

Where evaluation is recommended, say what it should target. A trenching layout aimed at the part of the site that was open ground, at the depth the potential section identified, is far more useful than a percentage sample scattered across a car park. The Archaeological Field Evaluation then has a brief rather than a formula.

Where an assessment overstates or understates

Overstatement is usually defensive. An author uncertain of the evidence writes high potential everywhere, the curator conditions an evaluation, and the developer pays for trenches that find made ground.

Understatement is more damaging. It usually comes from relying only on mapped records, ignoring the possibility of unrecorded remains in areas that have never been investigated, or treating a negative watching brief nearby as though it proved a wider absence.

The honest position, and it is one worth stating plainly in the report, is that a desk study can reduce uncertainty but cannot remove it. Where the potential is uncertain and the ground has never been tested, say so and recommend evaluation rather than manufacturing a conclusion.

How the county archaeologist reads it

They read the potential section first, then work backwards to see whether the evidence supports it, then check the recommendation against their own knowledge of the area. What persuades them is specificity: named sites with their record numbers, dated map editions, borehole references, and a plan that shows where on the site each conclusion applies.

What loses them is a report that reads as though the recommendation was chosen first. If the conclusion is no further work, the evidence for truncation needs to be the strongest part of the document.

An Archaeological Desk-Based Assessment should be written to the recognised professional standard, and councils expect a suitably qualified author. PlanScope drafts the structure and policy framing, and a qualified archaeologist should review it before submission.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.