QMark - archaeological remains and EIA

16th December 2016

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Stephen Williams

Rosey Meara, principal heritage consultant at Pegasus Group, explains how to identify archeological remains on proposed development sites.

This article considers the identification of archaeological remains within the EIA process. This is often undertaken in conjunction with assessment of the wider cultural heritage resource including built heritage and historic landscape features.

The identification and management of archaeological remains often involves a staged process including one or more of the following:

• archaeological desk-based assessment;

• geophysical survey;

• trial trench evaluation;

• archaeological excavation; and

• watching-brief.

Of these, archaeological desk-based assessment, geophysical survey and trial trench evaluation are most commonly used to inform EIA. Requirements for archaeological excavation or watching-brief are commonly attached as a condition to any permission granted for sites which impact the archaeological resource.

An assessment of the potential archaeological resource most often begins with an archaeological desk-based assessment. This will review the known resource informed by sources including: (for England)

• Historic England National Heritage List of Designated Heritage Assets;

• the County Historic Environment Record for information on known monuments and previous archaeological works, including development control site reports;

• Historic England Archives Monuments Information England database for additional records of known monument or archaeological works;

• aerial photographs, such as those held at the Historic England archives in Swindon, for identification of cropmarks or earthworks of potential archaeological interest or evidence of previous ground disturbance which may have impacted the below-ground archaeological resource;

• the County Archives for historic maps and documentary sources; and

• a site visit to review any extant archaeological features or evidence of previous disturbance.

While archaeological remains may include extant features such as earthworks, it is below-ground archaeological remains, or the potential for these remains, which are the most common focus of EIA assessment.

Where desk-based assessment identifies potential for archaeological remains it may be appropriate to undertake further surveys, with the most common being geophysical survey.

Detailed magnetometry is the type of geophysical survey most usually employed as it is good at identifying potential cut features, such as pits and ditches, and can cover large areas relatively economically.

Less commonly resistivity, which can be most successful at identifying buried walls, or ground penetrating radar, suitable for built up areas, may be used.

Where geophysical survey identifies potential archaeological features, the presence of below-ground remains may be tested by trial trench evaluation. Trial trench evaluation is commonly employed on a percentage basis, such a 2%, 4% or 5% sample. The layout of trenches can be targeted on geophysical anomalies or a standard grid-array can be used.

Trial trench evaluation is designed to characterise the nature of the below-ground archaeological resource while not compromising the integrity of the archaeological record. Within the EIA process, it is important to have an ongoing dialogue with the county archaeologist to keep them abreast of progress and to agree your approach to investigative work with them to keep timescales as concise as possible.

Where undertaken, the results of the desk-based assessment, geophysical survey and trial trench evaluation will normally form technical appendices to the Environmental Statement (ES). The key findings of the archaeological surveys will be considered within the ES, along with appropriate mitigation.

Where archaeological remains of the highest significance are identified (of a significance commensurate to a Scheduled Monument) preservation in situ will normally be necessary (except in wholly exceptional circumstances, c.f. paragraphs 132 and 139 of the National Planning Policy Framework).

This can be achieved through their removal from an application area or, in certain circumstances, they may be preserved within a scheme as part of an area of open space. Some schemes may choose to preserve archaeological remains of less than the highest significance in situ for example where the cost of archaeological excavation is viewed as prohibitive.

Where preservation in situ is not deemed necessary, and the archaeological resource will be removed by a proposed development, it is common for a condition requiring further archaeological works to be attached to any planning permission granted.

This condition usually requests a programme of archaeological works to be agreed with the archaeological advisor to the local planning authority. Such works are most commonly open-area excavation, which is the most intensive and also most expensive of the intrusive archaeological techniques, or watching brief.

In certain cases there may be targeted open area excavation of the most sensitive areas followed by a watching brief for remaining areas. Importantly conditions will typically require post-excavation assessment (specialist analysis) and reporting.

For works with remains of limited or modest interest, a grey literature report, which is a typescript report deposited with the local Historic Environment Record, and a note in a County Journal may suffice.

Where important archaeological remains are identified, publication will usually include an article in a county journal and/or, in the most interesting cases, a monograph.

Throughout the EIA process, it is key to start your consultation with the relative advisors at the earliest stages possible. This will ensure that the assessment and application timelines are progressed as smoothly and as expediently as possible.


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