Mitigation
Archaeological mitigation strategy and delivery
Once evaluation has defined what is present, mitigation determines how much of the site has to be excavated, in what order, and at what cost. The strategy is where the money is decided — not the fieldwork.
- Stage
- Post-evaluation, pre-construction
- Methods
- Targeted excavation, strip/map/sample, watching brief
- Agreed with
- Local authority archaeological advisor
- Drives
- Programme, cost and construction sequence
The next decision
Mitigation choices follow significance, impacts and accepted evidence. Preservation, targeted recording and monitoring are options to justify—not automatic outputs from landscape or area.
Compare options before committing the scope
Overlay deposit levels with foundations, drainage, landscaping and temporary works. Preservation needs evidence that the design avoids harm; open space or a shallow-looking plan alone does not demonstrate it.
Where recording is required, define area, sampling, discovery escalation and reporting. Cost each accepted option’s construction interfaces and residual obligations, then obtain the required approval before delivery.
- Cambridgeshire County Council: Archaeological advice for planning developments ↗
- UK Government: Historic environment planning guidance ↗
Content updated .
Strategy
Proportionate mitigation is negotiated, not assumed
A mitigation requirement is a professional judgement about significance and impact. Where the evidence supports a narrower scope, that case has to be made deliberately, with the evaluation data behind it.
- Testing whether design change can preserve remains in situ and reduce the area requiring excavation
- Focusing full excavation on the areas of genuine significance rather than the whole footprint
- Applying lighter-touch methods where the evaluation shows low density or heavily truncated deposits
- Setting realistic sampling and analysis levels at the outset, with assessment and any provisional analysis allowance distinguished
Methods
Mitigation methods and when each is appropriate
- Targeted excavation
- Full excavation of defined areas of significant archaeology identified at evaluation. The standard response where remains are substantial and cannot be avoided.
- Strip, map and sample
- Controlled topsoil removal across a wider area, rapid mapping of what is exposed, then sampling of features. Suited to sites with dispersed or uncertain remains.
- Preservation in situ
- Design-led avoidance through foundation solutions, raised levels or repositioned open space. Its feasibility and total cost must be assessed against deposit levels and construction design.
- Archaeological watching brief
- Monitoring of groundworks by an archaeologist where the risk is low but not negligible. The lightest option, and rarely sufficient on high-potential sites.
- Post-excavation
- Assessment, specialist analysis, publication where required, and archive deposition. A real cost and duration that must sit in the programme.
Delivery
How mitigation is delivered on a live site
- 01
Strategy and approval
Mitigation strategy and Written Scheme of Investigation prepared, negotiated and approved before any plant is booked.
- 02
Mobilisation
Resourcing, plant, welfare and site access confirmed, and interface with the contractor's programme agreed.
- 03
Fieldwork
Excavation and recording to the approved scheme, with progress reported against the agreed programme and variations flagged as they arise.
- 04
Reporting and discharge
Post-excavation assessment and reporting, then submission of the evidence required to discharge the condition.
Common questions
Mitigation: common questions
What does archaeological mitigation actually mean?
Mitigation is the work agreed to offset the harm a development causes to buried archaeological remains. In practice that means either avoiding the remains through design, or recording them through excavation before they are destroyed. Most development-led mitigation in Cambridgeshire is recording rather than avoidance.
Can mitigation be reduced or avoided?
Sometimes, and it is always worth testing. Preservation in situ through foundation design, level changes, or moving open space onto the most significant area can reduce the recording requirement substantially. This only works if it is raised while the layout is still capable of changing.
Who decides what mitigation is required?
The local planning authority, advised by its archaeological advisor, sets the requirement and must accept the approach before it is implemented. Our role is to put forward a proportionate, evidence-based strategy and to agree it in writing before mobilisation.
Can mitigation be phased around construction?
Usually yes, and on large sites it should be. Mitigation can be split to follow plot release or infrastructure phasing, provided the phasing is agreed with the authority in the approved scheme rather than improvised on site.
Project review
Send us your evaluation results
If you have an evaluation report and a mitigation requirement, send them over. We will set out what we think a proportionate strategy looks like and what it means for your construction programme.