Microbial degradation of wooden foundation piles in urban context – causes and concerns

Abstract

Modern infrastructural projects can endanger historical piled foundations supporting cultural heritage buildings, as groundwork can affect the subsurface environment by lowering the local groundwater level and increasing oxygenation in the soil. Wooden foundation piles are thereby placed at risk, as the durability of buried wood material is dependent on a stable, waterlogged, and anoxic environment. In this thesis, microbial wood degradation is explored, both in historical wooden piles and in proxy samples deployed in field and laboratory experiments. Observed degradation rates by erosion bacteria and soft rot fungi are related to burial conditions, with the aim to identify environmental parameters that promote wood degradation rates. To explore the complex interactions, an interdisciplinary approach was taken, and considerable effort was placed on experimental design with a focus on ease of measurement. In conclusion, maintaining a high and stable groundwater level appears to be the best protective measure, along with covering soils to reduce evaporation. Implications for stakeholders during ongoing infrastructure work are summarized and ways in which to reduce the risk of increased wood degradation rates during construction are suggested. Further studies are proposed to develop a guide for best practice when performing groundwork in areas with wooden foundations that are sensitive to degradation.