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The Sweet Track was a raised plank walkway that ran across a reed swamp over a distance of two kilometres, joining an island in the swamp to a ridge of high ground to the south. Tree-ring evidence has shown that it was built in 3806 BC, and was being repaired and maintained at least until 3800 BC. In 1983 a grant was obtained from the National Heritage Memorial Fund to purchase an area of land on Shapwick Heath as a Nature Reserve and to install a water pumping and distribution system along a 500m stretch of the trackway to ensure its preservation. This is the longest running scheme for the active preservation of waterlogged remains in the British Isles and is still one of very few in Europe. EH commissioned Somerset County Council Archaeology Section to review the condition of the trackway and the effectiveness of the management regime.
This review consisted of four keyhole excavations to permit removal of wood samples and an environmental sample column for determination of their respective levels of decay. In addition a new monitoring system was installed to study water levels, water quality, and the nature of the burial environment around the trackway over a twelve month period. The monitoring shows that water levels have remained consistently above the top of the trackway and that the burial environment is reduced or highly reduced at track level, ensuring that no significant decay by micro-organisms operating in aerobic conditions is likely to occur. The ground water quality and flow should also pose no threat to the structure.
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Excavation showed that the trackway timbers still retain the same visual appearance which they had during their initial exposure by the Somerset Levels Project in the 1970s and 1980s. The upper components of the structure were soft and had very poor surface detail while the lower elements appeared to be in better condition and retained good surface detail such as toolmarks. Detailed analysis of the wood samples, however, showed that all parts of the structure were very badly degraded, with exceedingly high moisture contents and very low specific gravities. This, together with the evidence of previous studies suggests that the present condition of the timbers is a result of rapid decay during and immediately after the active use of the structure combined with very slow degradation over thousands of years by bacteria operating in micro-aerobic or anaerobic conditions. The variation in visual appearance is probably a result of the nature of the initial decay, while the subsequent decay caused the greater loss in cell mass. The assessment has shown that the present water management system is succeeding in maintaining the condition of the trackway and its associated palaeo-environmental record, but that there are important lessons for future preservation and monitoring projects, including the need for quantifiable baseline data to be recorded at the earliest possible opportunity, as well as the potential benefits of joint projects with nature conservation bodies. Reconstruction of the trackway has been made in a reed bed on the reserve and it is hoped that a study of its decay during the next few years may provide some answers to the remaining questions about the Sweet Track and its survival over 5,803 years.