Cable routes are often given secondary consideration when developing renewable energy infrastructure due to their relatively small area compared to the overall development. However, the length and linearity of cable routes (and pipelines) mean that they are no less likely to interfere with buried archaeology, and it is as important to assess the archaeological potential along a cable route as it is across the main development site.
Traditionally, archaeological geophysical surveys were a laborious process, which tended to lead to relatively narrow survey corridors. Narrow survey areas present two problems:
1) Archaeological Context
Anomalous geophysical responses indicating archaeology can still be identified within a narrow survey corridor; however, the extent of such a feature and its relationship with the broader area will not be obvious.
2) No room to manoeuvre
If archaeology is encountered, an alternative route may need to be sought. A narrow corridor will not provide enough area to alter the cable route; however, with a wider area surveyed, a different alignment can be designed that would satisfy the requirement to safeguard any identified archaeology.
Modern, multi-sensor towed arrays, such as the Sensys MXv4, mean that cable route surveys are no longer constrained to narrow corridors, enabling much wider swathes to be acquired in less time. TerraDat recommends that a minimum 60 m wide swathe be surveyed along cable routes to ensure adequate coverage for both interpretation and route design flexibility.
In the image above, the left-hand cable route has a survey corridor that measures 10 m across. Several linear features cross the corridor; however, it is impossible to discern what the features are from such a narrow strip. When the width of the survey corridor is extended to 60 m, it becomes apparent that the two linear features in the centre of the route are, in fact, the sides of a bivallate ring ditch. Not only does the wider corridor enable interpretation, but it also provides sufficient data to propose an alternative route that avoids this ancient monument.
For help designing and conducting a suitable geophysical investigation of your site, call us on +44 (0) 2920 700127 or email web@terradat.co.uk