Archaeological monitoring was undertaken during site investigation and groundwork associated with the refurbishment of a Rotating Biological Contactor site at Thorney Sewage Treatment Works (STW), Nottinghamshire. Archaeological monitoring was undertaken during the excavation of 3 trial pits within the site in April 2010, and during the subsequent groundworks carried out in March 2011. Each trial pit was machine excavated to a depth no greater then 3.5m in order to ascertain ground conditions. The main groundworks comprised the topsoil stripping of a 400m2 area to a depth of 0.5-0.8m, and the further excavation of a 44m2 area to a depth of 1m for the new sewage treatment tank. Archaeological monitoring during the groundworks did not identify any evidence of human activity prior to the modern period.