Archaeological Evaluation

Archaeological evaluation can take several forms but each one is important in understanding the significance of any heritage assets on a site. Evaluation is commonly undertaken at the pre-application stage in order that the results, in the form of an illustrated report, can accompany a planning application. The purpose of this is to enable the Local Planning Authority (LPA), on the advice of the county Historic Environment Service (HES), to take an informed decision on the implications and impact of a development proposal on any archaeological remains. This is in accordance with paragraph 189 of the National Planning Policy Framework (NPPF).


One of the most common types of archaeological evaluation is trial trenching and this combines machine and hand excavation. Trial trenching is designed to be a rapid sampling exercise and routinely comprises a series of linear trenches spread across a proposed development site. The purpose is to investigate an area where existing information indicates that there may be some archaeological potential but there is limited or no evidence for it on the site itself. Sampling ratios vary but are commonly anywhere between 2-5% of the proposed site area or impact zones.


For medium to large sites, trial trenching can often be preceded by other evaluation techniques, the most common of which is geophysical survey. This is a very efficient and effective method of establishing the presence of buried archaeological remains across larger open areas and the results are used to target zones of highest potential for trial trenching. As geophysical survey is an evaluation technique in its own right, there is often a dispensation to carry out less trial trenching if these methods are used in combination. This is also the most cost-effective solution in most scenarios.


In most cases, we will prepare an evaluation strategy for you and this is included in a Written Scheme of Investigation (WSI) for approval by the HES. This document sets out in detail the rationale and methodology for the project and, as such, we take great care to ensure that this meets its objectives in the most professionally robust, efficient and cost-effective manner possible.