Published online by Cambridge University Press: 09 November 2011
The site of the Nash Waste Water Treatment Works (hereafter called WWTW) lies on the northern bank of the Severn Estuary, 4 km south of Newport (Casnewydd) (NGR ST 337 840), on the flood plain of the Severn, at the mouth of the River Usk (FIG. 1). The area forms part of the coastal wetlands of the Gwent Levels. Alluvial silts, the result of sediment deposition associated with post-glacial sea-level rise, are interleaved with layers of peat, characterised as the Wentlooge Formation, and overlie Triassic Mercia Mudstone bed-rock.