Maple Lodge Sludge Treatment Works, Maple Cross, Hertfordshire Palaeoenvironmental Assessment

Wessex Archaeology was commissioned by Stantec UK Ltd to undertake a palaeoenvironmental assessment of samples taken during Ground Investigation (GI) works at Maple Lodge Sludge Treatment Works (STW), Maple Lodge Close, Rickmansworth, Maple Cross, Hertfordshire. The Site is centred on National Grid Reference 503988, 192206 (TQ 03988 92206). This report follows on from geoarchaeological monitoring of GI works and deposit modelling, which identified a Quaternary sequence of fluvial sands and gravels, organic gravels, a Holocene alluvial sequence including organic alluvium and peat deposits, capped by made ground. The organic gravels, organic alluvium and peat deposits were assigned a high geoarchaeological potential to provide information on the later Pleistocene and Holocene environment at the Site. The principal aim of this palaeoenvironmental assessment is to determine the age, nature and depositional history of deposits recovered from Maple Lodge STW. The results will be used to assess the preservation potential of palaeoenvironmental remains, and to reconstruct past environments and landscapes change associated with local and regional archaeological records and settlement histories. Radiocarbon dating of the organic sequence places the timing of organic gravel deposition in the Middle Bronze Age (1490-1290 cal. BC), with a broadly comparable date for the organic alluvium (1430-1230 cal. BC) and with peat formation spanning the Late Iron Age to medieval periods (cal. AD 890-1020). The top of the alluvial sequence was dated to the 11th-12th century AD (cal. AD 1000-1160). A sample from the peat deposit within WS03 produced a modern date (cal. AD 1960-1970) and is assumed to be the result of contamination via bioturbation. Preservation was assessed for all palaeoenvironmental proxies. Poor preservation was typically observed for plant macroremains and pollen, reflecting either aerobic conditions during/following deposition, or reworking of older organic material. Molluscs were absent from the assessed samples, which may reflect unsuitable conditions for deposition or preservation of molluscs, or post-depositional processes resulting in the degradation of mollusc shells. Given the poor preservation of palaeoenvironmental proxies, any reconstruction of past environments should be tentative. During the Middle Bronze Age there is evidence for mixed pine-hazel woodland, with scattered clearings present, consistent with other records from the Colne Valley. During the Late Iron Age to medieval periods, the dryland consists of deciduous woodland, dominated by hazel, with occasional clearings present. The wetland consists of damp areas colonised by sedges/rushes, with shallow pools/slow-flowing water and frequent alder trees. There is limited evidence of human activity within the record at the Site, but the palaeoenvironmental record provides information on the resources available to human communities within the area. Given the poor preservation of palaeoenvironmental proxies, and limited evidence for human activity, no further palaeoenvironmental analysis is recommended for the Site.