A suite of archaeological investigations were undertaken in advance of, and during construction of a new Sewage Treatment Works (STW), associated outfall pipe and permanent access road on land adjacent to the River Thames within Beale Park, West Berkshire. The archaeological investigations comprised trench evaluation in advance of construction followed by archaeological monitoring and recording during construction. Two main phases of activity, separated by a period of alluvial deposition, were identified. Evidence of transient or low-intensity prehistoric activity was identified throughout the scheme in the form of cut features (possible hearths, pits, and tree-boles) and both worked and burnt flints. In particular, a pair of tree-boles, located beneath the lowest alluvial layer, was found to contain in-situ flint knapping debitage of apparent Mesolithic date. Further tree boles, pits, postholes and fire pits, also located beneath the lowest alluvial layer, are likely to be early prehistoric in date. A ditch, apparently associated with a previously undated double-ditched cropmark enclosure (lying outside and to the north of the STW development area), was investigated and proven to be of late Bronze Age or early Iron Age date.