An Evaluation of In situ Preservation Potential and Monitoring Strategies at the Sites of the Sweet Track, and Glastonbury Lake Village, in the Somerset Levels, UK Louise Jones Collaborative Research Studentship: An Evaluation of In Situ Preservation Potential and Monitoring Strategies at the Sites of the Sweet Track, and Glastonbury Lake Village, in the Somerset Levels, UK. In situ preservation is a central strategy for the conservation and management of archaeological sites, and is an important part of government archaeological policies, and heritage organisation guidelines. For example, in situ preservation is referred to in Report 1 of the National Heritage Science Strategy (Williams, 2009), and is designated by Planning Policy Guidance Note 16 (PPG 16) (DOE, 1990:6) as the ‘preferred’ option for archaeological conservation. It cannot, however, be assumed that artefacts or structures are preserved purely because they are in situ beneath the ground surface. It is necessary to both determine the current preservation state of any inorganic and organic remains, and also to monitor a site in order to characterise the nature of the burial environment, and identify any potential threats to preservation.
the AHRC and EPSRC under the Science and Heritage Programme. The research presented here documents the results of the intensive field and laboratory work, as well as in situ monitoring and subsequent data analysis, undertaken between 2008 and 2012, at two internationally important archaeological sites; the Iron Age site Glastonbury Lake Village, and a section of the Sweet Track located within the Shapwick Heath National Nature Reserve (outside the bunded area), in Somerset. Both of these sites are Scheduled Ancient Monuments. The broad aim of the project was to determine through intensive monthly monitoring, and the subsequent analysis, integration and discussion of the data, whether in situ preservation is an appropriate conservation strategy at these sites. Seven different parameters were monitored, including water table depth, groundwater chemistry, redox potential, pH, conductivity, ditch water levels, and soil moisture levels using Time Domain Reflectometry (the latter parameter only at Glastonbury Lake Village).
Installing a Time Domain Reflectometry access tube
The findings of the MARISP project were the catalyst for this independent PhD research project based at the University of Reading. This research was funded by
The monitoring strategy and results for the Sweet Track site were relatively straightforward, in contrast to the more complex monitoring project and datasets at Glastonbury Lake Village. Overall, the research undertaken at each site has, however, been successful. Recording water table levels has proved to be the most valuable monitoring technique at both sites in terms of identifying a clear threat to preservation from the low summer drawdown in the water table. Notably, at Glastonbury Lake Village groundwater levels fell between 21 and 35 cm lower in 2010, than were recorded at the three locations monitored to the south of the site during the MARISP project in 2004. This has put more of the archaeological deposits at risk of oxidation, desiccation and microbial decay. It is, however, important to highlight the findings of the soil moisture analysis. Using this data the depth of the capillary fringe above the water table has tentatively been identified. The depth of the capillary fringe appears to be highly variable, and reflects differences in stratigraphy across Glastonbury
AHRC/EPSRC SCIENCE & HERITAGE PROGRAMME • SUSTAINING THE IMPACT OF UK SCIENCE AND HERITAGE RESEARCH
The Monuments at Risk in Somerset’s Peatlands (MARISP) project was established in 2004 because of an awareness of the threats to wetland sites, both nationally, and in Somerset (Brunning et al., 2008). Over 12 months monitoring and small scale excavations were conducted at 13 sites, including Glastonbury Lake Village. Although Glastonbury Lake Village was identified as the best preserved site, a clear threat to preservation was nevertheless identified in terms of the drawdown in the water table during the summer.
Recording soil moisture levels
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