Archaeological Field Evaluation: the report structure

An archaeological evaluation report has one job: to say what is under the site, how important it is, and what has to happen about it before the scheme can proceed. Everything in the structure below serves that. A trial trench evaluation that describes forty contexts in careful detail and then offers three lines of recommendation has failed the developer who paid for it.

Evaluation sits between the desk-based assessment and any mitigation. It is fieldwork, usually trial trenching, carried out to a written scheme of investigation agreed with the council's archaeological adviser, and reported to the standards published by the Chartered Institute for Archaeologists.

Aims carried forward from the desk-based assessment

The report opens by restating the archaeological potential identified earlier and the specific questions the evaluation was designed to answer.

Those questions should be concrete. Is the Roman road alignment shown on the historic mapping present within the site, and if so at what depth? Does the medieval settlement extend beyond the scheduled area? Has nineteenth century quarrying removed earlier deposits across the northern half?

Where the Archaeological Desk-Based Assessment identified potential that the trenching did not test, say so here rather than in a footnote. An evaluation that leaves part of the site unexamined is a normal outcome and an undisclosed one is a problem.

Trench layout, sampling rate and justification

The trench plan needs a reason, and the reason belongs in the text.

Sampling is usually expressed as a percentage of the developable area, agreed in advance with the archaeological adviser, and delivered either as a regular array covering the site evenly or as targeted trenches over anomalies identified by geophysical survey. Most evaluations use a combination.

The report should give the agreed sampling rate, the rate actually achieved, and the reason for any difference. Trenches moved or shortened because of live services, tree root protection areas, standing structures or contamination are routine, and each move needs recording on the plan with a note of why.

Where geophysics preceded the trenching, include the survey plot with the trenches overlaid. That single figure answers most of the questions a reviewer will have about whether the evaluation was targeted sensibly.

Stratigraphic description and context recording

The descriptive core runs trench by trench, using single context recording and a continuous context numbering sequence.

Each trench gets its dimensions, orientation, ground level and reduced levels, the depth of the deposits removed by machine, the horizon at which hand cleaning began, and a description of each context with its stratigraphic relationships. Plans and sections at stated scales sit alongside, with levels to Ordnance Datum.

Two things make this section usable. A trench summary table at the front, giving each trench's dimensions and a one line result, so a reader can see the shape of the site without reading forty pages. And a matrix or equivalent showing the stratigraphic sequence where it is complex.

Negative trenches matter as much as positive ones. A trench with nothing in it is evidence, and reports that skate over the empty trenches tend to overstate the significance of the rest.

Finds and environmental assessment sections

Specialist assessments are reported separately and then drawn into the interpretation.

Finds are quantified by context, by material type, by count and by weight, with spot dating where the material allows it. Pottery, ceramic building material, animal bone, metalwork and industrial residues each get their own note from the relevant specialist, and each should state whether the assemblage warrants further analysis.

Environmental sampling covers bulk samples processed for charred plant remains, charcoal, small bones and molluscs, with an assessment of preservation and of radiocarbon dating potential. Where waterlogged deposits are present, say so prominently, because organic preservation changes the significance assessment and the cost of any mitigation.

Every specialist contribution should end with a recommendation: no further work, further analysis, or a specific programme. That is what a developer's cost plan needs.

Human remains deserve separate mention. Where burials are encountered, a licence is required before they are disturbed, and the programme, the cost and the sensitivity of the work all change. An evaluation that turns up a burial in a trench will usually stop that trench, record the position and report it rather than proceeding.

Interpretation and significance of the remains

This is where the report earns its fee, and where weak reports go quiet.

Interpretation sets out what the remains represent, their date range, their extent within the site and their likely extent beyond it, and their condition. Significance is then assessed against national policy, which treats archaeological interest as part of the significance of a heritage asset, and distinguishes assets of demonstrably equivalent significance to scheduled monuments from those of lesser importance.

Say plainly where the remains sit on that scale and why, using the criteria that apply: period, rarity, documentation, group value, survival and condition, fragility, diversity and potential. A report that describes remains as being of local significance without saying against what measure is not giving the council anything to work with.

Where the assessment is honestly uncertain, say that too. Inspectors and officers respond better to a stated uncertainty than to confidence that evaporates under questioning.

Recommendations for mitigation

The recommendation section should give the council's adviser something to condition and the developer something to price.

The options are preservation in situ, achieved through layout changes, raised ground levels, foundation redesign or piling with a reduced footprint; preservation by record, through open area excavation, strip map and sample, or targeted excavation of defined areas; or a watching brief where the potential is low but not nil.

Each recommendation needs an area, a method and an indication of scale. A recommendation that says "further archaeological work will be required" without saying how much is the single most common complaint developers make about these reports.

Where preservation in situ is proposed, set out what the design would have to do, and be realistic about whether a scheme with a basement can deliver it. Where preservation by record is proposed, the post-excavation and publication programme is part of the cost and belongs in the recommendation rather than appearing later.

Archive and reporting commitments

Finally, the housekeeping that the council's adviser will check.

The report should confirm that an entry has been made in the national online index of archaeological investigations, that a copy will be deposited with the local Historic Environment Record, and that the site archive will be prepared to the relevant standard and deposited with a named receiving museum. Museum deposition arrangements should be confirmed before fieldwork starts, because several museums have closed to new archive deposits and the alternative arrangements take time.

Copyright, confidentiality and the timetable for the digital archive all sit here too.

Timing is worth a note of its own. Where the council's archaeological adviser asks for evaluation before determination, the scheme cannot be decided until the report is in, and trial trenching needs dry enough ground, a machine, a fenced compound and sometimes a licence to work near protected species. On a greenfield site that programme can run to several weeks before a spade goes in the ground.

Developers who leave evaluation until after a refusal on archaeological grounds pay twice: once for the fieldwork and once for the delay.

An Archaeological Field Evaluation has to be carried out and reported by suitably qualified archaeologists, and councils expect a registered organisation or an appropriately accredited author. PlanScope can draft the reporting structure, the policy framing and the significance narrative, and the fieldwork, the specialist assessments and the professional judgement must come from that archaeologist. The same division applies to other survey-led documents, as the piece on the Agricultural Land Classification survey sets out, and to the recording work that follows consent, covered under Historic Building Recording.

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