Survey effort tables in an archaeological field evaluation

The archaeological evaluation survey effort table is the first thing a county archaeologist looks at, and often the only thing they look at closely before deciding whether the evaluation is adequate. It answers the question the rest of the report cannot: how much of the site was actually examined, and how much was not.

An evaluation with twelve trenches and a clear effort table reads as controlled work. An evaluation with twenty trenches and no table reads as a collection of holes, because nobody can tell what proportion of the site they represent or whether the distribution was designed or opportunistic.

Why the effort table is read first

A curator is deciding one thing: whether the evaluation provides enough information to inform a planning decision and, if mitigation is needed, to specify it.

That decision depends on coverage and distribution rather than on the finds. A site where three per cent of the area was trenched across an even distribution and nothing was found supports a different recommendation from one where the same percentage was concentrated in the one corner the groundworks could reach.

So the table has to let a reader reconstruct the coverage without reading the trench descriptions. Put it near the front, not in an appendix.

Trench numbers, dimensions and sample percentage

State all of it, and state it in the same units throughout.

Report the sample percentage twice, against the whole application area and against the area that could realistically be trenched. The second figure is the honest one, and quoting only the first understates the coverage achieved on a constrained site.

The sample percentage expected is set by the curator rather than by a national rule, and it varies with the archaeological potential identified in the desk-based work. Say in the report what figure was specified and what was achieved, and if the two differ, say why in the same paragraph.

Trench dimensions deserve the same discipline. A schedule listing each trench with its planned and as-dug dimensions, and a reason for any shortfall, pre-empts the question. Trenches shortened by services, a tree or standing water are normal. Trenches shortened with no explanation are not.

Relating effort to the written scheme of investigation

The written scheme of investigation is the agreed specification, and the evaluation report is the account of whether it was followed.

Set out a direct comparison: what the scheme required, what was done, and where the two diverge. Divergences are not failures if they were agreed, so record the agreement, the date and who gave it. A phone conversation with the curator confirming a trench could move 15 metres is a material fact and belongs in the report.

The professional standard for archaeological field evaluation expects the methodology to be stated and deviations recorded, and a report that quietly presents the as-dug position as if it were the plan loses the reviewer's confidence for the rest of the document.

Where the evaluation follows an Archaeological Desk-Based Assessment, cross-refer to the specific predictions it made. An evaluation designed to test three identified areas of potential should report against those three, not simply across the site.

Areas not evaluated and why

This is the section most often missing, and the one a curator will ask for.

Produce a plan showing the excluded areas shaded, with a key giving the reason for each. Then list them in the table with areas in m².

Reasons that are routinely accepted:

1. Live services, with the utility search or scan result referenced
2. Standing buildings and hardstanding that could not be broken out
3. Tree root protection areas where the arboricultural constraint prevailed
4. Ground contamination or unstable ground preventing safe access
5. Areas outside the applicant's control at the time of the evaluation
6. Statutory constraints such as a scheduled monument, where consent was not sought

What matters is that the reason is specific and verifiable. "Not accessible" is not a reason. "Occupied by the existing warehouse, scheduled for demolition in phase two" is.

Then say what follows. If an unevaluated area carries potential, the recommendation should address it, usually by proposing evaluation after demolition or a watching brief secured by condition.

Recording negative results properly

A negative evaluation is a positive result if it is recorded well enough to be relied on.

The elements that make it reliable: the natural geology or other terminal surface recorded in each trench with its depth, a description of the overburden and any made ground, evidence of truncation whether by ploughing, terracing or previous development, a statement of the visibility conditions during excavation, and the presence or absence of artefacts in the subsoil as distinct from in features.

Photographs of representative trench sections, with scales, do more for a negative result than any amount of prose. So does a section drawing showing the stratigraphic sequence.

What undermines a negative result is silence. A trench recorded as "no archaeology present" with no depth, no geology and no section is unusable, because a reviewer cannot tell whether the trench reached a level where archaeology would have been visible.

Confidence in the conclusions

Include a short confidence statement. Three or four sentences covering the coverage achieved, the conditions during the work, the limitations arising from the unevaluated areas, and the resulting level of confidence in the conclusions.

This is a professional judgement and it should read like one. "The 4.1 per cent sample across the available area, with even distribution and good visibility in dry conditions, supports a conclusion of low archaeological potential across the trenched area. Confidence is lower in the northern third, where live services prevented trenching within 8 metres of the boundary." That is a sentence a curator can act on.

Avoid stacking hedges. One honest limitation stated clearly carries more weight than a paragraph of qualification.

How the table supports a mitigation recommendation

The recommendation has to follow from the coverage, and the table is what connects them.

Where the evaluation found nothing across a good sample with even distribution, a recommendation of no further archaeological work is supportable. Where it found features in two trenches, the recommendation moves to further evaluation, targeted excavation or preservation in situ depending on the significance. Where coverage was poor for reasons outside the archaeologist's control, the honest recommendation is further work after the constraint is removed, and saying so protects everyone.

A recommendation that does not match the effort reported is the thing reviewers notice. An Archaeological Field Evaluation concluding no further work after a one per cent sample on a site of high potential will be rejected, and the reviewer will cite the table in doing so.

Where recording of standing fabric is also required, keep that effort reporting separate, because Historic Building Recording works to its own level definitions and mixing the two confuses both.

Councils expect a suitably qualified author for archaeological work, and professional review is strongly advised. Reviewers can be found through the professional directory. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.