Monitoring window samples showed historic made ground above alluvial clay and Kempton Park Gravels Member late Pleistocene deposits (levels of The nature and level of natural topography was Holocene clay alluvium to 1.28m OD, overlying Pleistocene Terrace gravel (Kempton Park Gravels Member) to 0.43m OD. The surface of both deposits varied which may indicate natural processes such as tidal creeks, as well as human interventions such as digging clay for brickmaking. 3.3.3 The earliest deposits identified were alluvial deposits which, by analogy with local sites, may also contain prehistoric and Roman remains. The latest deposits identified are ground-raising dumps characterised by the presence of coal ash and dated from the second half of the 17th century to the middle of the 19th century. Modern disturbance varied between 0.15m and 0.8m in areas not reworked by former asbestos investigations, that may be as deep as 1.7m. However, these were all in open areas and where buildings have basements and deep foundations deposits may be reworked or removed to Terrace Gravel levels. There is a large main sewer that traverses the site which also will have disturbed deposits and may have been constructed in a trench with battered sides.
Dave Sankey (Tue,) studied this question.