What Happens If Trial Trenching Finds Archaeology

What if the result is negative or inconclusive?

A negative evaluation records what was found in the agreed sample; it is not a guarantee that no archaeology survives elsewhere. Submit the report through the agreed review route and obtain the site's required confirmation before assuming the obligation is complete. Inconclusive results may need clarification or further targeted work before a mitigation position can be agreed.

A positive result is information, not a stop notice

Trial trenching exists to establish whether archaeological remains are present, where they are, how significant they are and how extensive they might be. A positive result converts an open-ended risk into a defined scope of work that can be priced and programmed.

In much of Cambridgeshire — the gravel terraces, the fen edge, the chalkland — a positive result should be the working assumption on greenfield land. Schemes that budget for it are rarely derailed by it.

What the authority does with the result

The evaluation report goes to the local planning authority's archaeological advisor, who assesses the significance of what was found and the impact the development would have on it. From that assessment comes a mitigation requirement: which areas need further work, and broadly by what method.

Significance is a judgement, and judgements are made on evidence. A well-executed evaluation that properly characterises and dates what is present gives you the basis to argue for a proportionate requirement. A thin one invites a cautious, and therefore expensive, response.

The options that follow

Broadly, four routes exist, and most sites end up with a combination of them.

• Preservation in situ: adjust layout, levels or foundation design so the significant remains are not disturbed. Cheapest where achievable, and only achievable while the masterplan can still move.
• Targeted excavation: full excavation of the defined significant areas before construction. The standard route on most development sites.
• Strip, map and sample: wider controlled stripping with sampling, suited to dispersed or uncertain remains.
• Watching brief: monitoring of groundworks where residual risk is low. Rarely sufficient where evaluation found substantial remains.

How to keep your options open

The practical lesson is about timing rather than archaeology. If evaluation results arrive before the layout is fixed, design-led avoidance is genuinely available and can remove large parts of the recording requirement. If they arrive after reserved matters are approved and the S106 is signed, the only remaining lever is how efficiently the excavation is delivered.

That is the whole argument for pre-determination evaluation on sensitive sites: not that it avoids archaeology, but that it keeps the cheap options on the table.

What it means for cost and programme

Cost follows area, feature density, deposit depth and the level of analysis required. Programme follows the same variables plus plant and staffing availability. Neither can be quoted honestly without the evaluation data — which is why a contractor giving you a hectare rate before seeing the report is telling you about their sales process, not your site.

The decision sequence after the evaluation report

A positive report does not move straight to excavation. It first has to become an agreed planning response. Treat the sequence as a set of commercial gates: report acceptance, significance and impact discussion, mitigation brief, contractor method, authority approval, then mobilisation.

The fastest programmes overlap preparation without pre-empting the authority. A draft mitigation scope can be priced while the evaluation report is under review, but fieldwork should not start until the required written scheme has been approved.

• Confirm which evaluated areas are affected by the current layout, levels, drainage, roads and compounds
• Separate areas that can be preserved from areas where disturbance makes excavation unavoidable
• Ask for the mitigation boundary and method to be expressed spatially, not only in narrative
• Build authority review, mobilisation, fieldwork, interim sign-off and reporting into the programme as separate gates
• Define the evidence needed for phased release so completed areas can pass to construction

What a mitigation tender needs before it can be compared

Issue the evaluation report, trench plan and data, the proposed development impact plan, the authority brief or correspondence, access constraints and the required construction handover dates. Without those, bidders are not pricing the same archaeological problem.

Ask each bidder to state field team size, plant assumptions, spoil movement, contingency for feature density, reporting and specialist allowances, archive obligations, programme basis and what constitutes completion. The cheapest total is not meaningful until those assumptions are aligned.