Thames Water ALF pipeline Phases 1 & 2, River Darent, Kent (KT-PIP02 & KT-FRA02)

Clients: Thames Water plc

Author: Elizabeth Howe

Site supervisors: Tony Mackinder, with Elaine Eastbury, Kevin Appleton and Paul Thrale

MoLAS was commissioned by Thames Water to carry out an archaeological watching brief or strip map and sample investigation along the route of the ALF (alleviation of low flows) pipeline in the Darenth Valley. Although the pipeline is `permitted development´ and does not require planning permission, Thames Water adheres to the terms of the Code of Practice on Conservation, Access and Recreation, published as a result of the 1989 Water Act, insofar as its activities may affect the historic landscape.

The Darenth Valley contains many archaeological sites, in particular Roman villas and bathhouses, and Anglo-Saxon cemeteries. The route passed by a number of Scheduled Monuments including Roman villas at Darenth, Franks and Farningham.

The route of the Phase 1 pipeline, c 3.9km in length, extended from the A2 near to Bean and south to the outfall into the River Darent adjacent to the Darenth Roman villa. The Phase 2 pipeline started from Roman Villa Road near to the Darenth villa and extended south past Horton Kirby to the M20 by Farningham, a total length of 7km. The archaeological watching brief comprised the monitoring of topsoil/subsoil stripping of the 20m-wide easement, with additional monitoring of the pipe trench excavations, and took place in January–February 2002 and June–July 2002. Isolated archaeological features were rapidly recorded and investigated as the stripping progressed along the route. The archaeological features were planned by MoLAS surveyors using Pen Map, a computerised recording system, and the areas of investigation located by GPS. A team of six MoLAS archaeologists carried out the monitoring.

Significant archaeological remains were uncovered where the route passed to the north of the Darenth Roman villa. A four-week excavation with up to six archaeologists recorded late Roman activity. This included a road surface, ditches, postholes and pits, suggesting activity was taking place in the fields outside the villa complex. There was also evidence of Anglo-Saxon occupation, dating from the mid 5th to early 6th century, with a rubbish pit, an inhumation burial of a child and an occupation deposit.

The Phase 2 works took place over the summer of 2003, following fieldwalking and geophysical surveys along selected parts of the route. Although passing by several SAMs and potential archaeological sites, the pipeline produced very little archaeological activity. Significant sections of the route were located on thick colluvial deposits, which even the trench excavations did not fully penetrate, therefore preserving potential archaeological remains in situ. One significant archaeological feature was a very large Iron Age pit.

This site report is extracted from MoLAS 2003: annual review