This collection comprises reports, images, and a finds database from a multi-phase watching brief carried out by Wessex Archaeology as part of the Boston Barriers Tidal Scheme between 2018 and 2021. The watching brief was split into two phases. The first phase monitored construction dredging and cofferdam installation between 12 November 2018 and 18 April 2019 located on the mud bank against the south bank of the tidal River Witham downstream of the Grand Sluice. The second phase was a programme of archaeological and geoarchaeological monitoring of the excavation works between the pile walls for tie rod installation along the south bank of The Haven. This was undertaken between 20 April 2020 and 04 May 2020. Further dredging operations were undertaken between March 2021 and April 2021 along the south bank of The Haven within the swinging hole area opposite the dock entrance to the Port of Boston. Much of the excavation for the second phase was within modern made ground (up to 2m in thickness) comprised of redeposited material dredged from the river in the 20th century, overlaying dark grey in-situ river silts.