Evaluating evaluation trenching in archaeological projects

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Historic environment assets, whether designated or not, are significant material consideration in the planning process. Archaeological Written Schemes of Investigation (WSIs) are produced as part of the development process and follow a generalised workflow from Desk based Assessments, Geophysical Survey, Evaluation Excavation, Mitigation Excavation, Post Excavation Assessment and Analysis, through to Reporting and Publication. Although each of these steps is important, arguably the phase of Evaluation Excavation (trenching) is pivotal. Not only is it the first time archaeologists investigate the nature of the deposit sequences and archaeological remains, but more critically, it provides the data on the nature and distribution of historic environmental resources, which determines the methodology of the full mitigation excavation. Despite the prominence of evaluation excavation within the archaeological process, scant research has been undertaken on the effectiveness of current strategies for the detection of archaeological remains, and the importance of different depositional environments (e.g. urban, alluvial) to the process. An often quoted figure of 5% by area of a development site is derived from an early study (Hey and Lacey 1999), and a 5% sample is a typical figure promoted as an archaeological condition. However, given the development of methods of geoprospection for shallow environments (e.g. large area magnetic surveys on chalklands), and a much improved strategy for the deposit modelling of deeper accreting sediments (e.g. urban, alluvial environments), it is time to revisit the process of evaluation trenching. Ultimately, the effectiveness of evaluation strategies needs to be analysed and its application within the archaeological process refined.Research questionsThe aim of this PhD is to assess the usefulness and limitations of evaluation trenching in different environment types, for the detection of different archaeological resources. This can then allow the development of better strategies of evaluation trenching, and possibly a clearer relationship between different evaluation designs and other archaeological methods, e.g. gradiometry or deposit modelling. Ultimately, this will lead to better holistic archaeological programmes within the developer funded sector and better yields from archaeological programmes.The aims of this PhD will be addressed through five fundamental research questions (i-v)i. What evaluation trenching strategies are suitable in complex (accreting) depositional environments and how much evaluation excavation is required in conjunction with a deposit modelling framework for these environments?ii. What evaluation trenching strategies are suitable for archaeological detection on dryland (shallow bedrock sites, e.g. chalk) and how should it be applied in conjunction with shallow geoprospection methods suitable for dryland shallow bedrock areas?iii. What are there different practices for evaluation trenching and how do these compare in their effectiveness for the identification of historic environmental resources?iv. What is the ability of evaluation trenching to detect small, less obvious archaeological features from earlier periods, e.g. Creswellian flints, Mesolithic features?v. Is the 'industry standard' of 5% evaluation excavation strategy effective?