NHER 66829 (Monument record) - Surviving Holocene peat and alluvial deposits and potentially associated evidence for prehistoric activity

June 2011 and January 2012. Desk-based Assessment and Ground Penetrating Radar Survey.
Review of historic land use in order to identify potentially surviving underground obstructions that could hinder the proposed redevelopment of the site. This study was focused on the potential for remains associated with the coal power station (NHER 55410), the gas production facility (NHER 55530) and the gas turbine power station (NHER 55411).
The coal power station was constructed c.1922, extended in 1938 and demolished c. 1981. Potentially associated underground structures include a concrete pad foundation for the original part of the power station, pile foundation for the extension and a water supply chamber that had lain on the south side of the power station. It is possible that a basement was also present, although there is only one reference to this in the available historic information. It appears that the concrete floor to the power station has already been removed.
The gas production facility was constructed during the 1960s and mostly demolished prior to 1989, although some of the site is still operational. A review of the historic records identified no high risk items, although gas pipes will run across the site and several associated large pits were noted during the walkover survey undertaken as part of this study.
The gas turbine power station was constructed c.1965 and decommissioned and demolished in 2000. Surviving sub-surface remains are likely to include the foundations and ground floor slab the power station, as well as a cable culvert and buried (potentially still oil-filled) cables.
It is noted that the ground level is believed to have been raised at some time in the past, with the uppermost deposits therefore comprising made ground.
A ground penetrating radar survey of part of the site was deemed to have had mixed success, although it did succeed in identifying the foundations for the coal-fired power station.
See report (S1) for further details, including plans and photographs of the former industrial buildings and various photographs of surviving structures taken during the walkover survey of the site.
P. Watkins (HES), 17 March 2023.

December 2011. Desk-based Assessment.
Assessment of potential archaeological impact of large proposed development.
This study identified the potential for prehistoric remains and/or artefactual material to survive at depth, beneath alluvial deposits. The potentially for significant Roman remains to be present was also noted.
Large part of the site will though have a degree of disturbance as a result of 20th-century industrial activity.
See report (S2) for further details.
P. Watkins (HES), 17 March 2023.

July 2015. Trial Trenching and Borehole Survey.
Evaluation of large proposed development site.
A total of eight trenches were excavated, which were widely dispersed across the proposed development area.
As expected the three trenches excavated in the western half of the site revealed evidence for considerable recent disturbance, with various made-ground, industrial waste and demolition deposits recorded. The earliest deposit encountered was an alluvial layer containing bands of black organic material exposed at a depth of 0.59m OD in the south-westernmost trench.
Similar modern deposits were also exposed in the five trenches excavated in the eastern half of the site. In one of the trenches this material was seen to lie above a probable alluvial deposit and in another a bright white chalk interpreted as a natural deposit was encountered at a depth of 1.61m OD.
The only feature recorded was a modern construction cut. A fragment of modern glass was the only find.
As part of this evaluation geoarchaeological boreholes were excavated at one end of four of the trenches. These allowed a programme of deposit modelling, which integrated the results of these boreholes with evidence from previous geotechnical investigations. The basal unit overlying the bedrock chalk is a horizon of sand and gravel recorded at between -4.37 and 1.20m OD, which is likely to represent material deposited within a high energy braided river system during the Late Devensian period (c.10-15,000 years BP). A depression recorded in one borehole may represent a former tributary to the main river channel to the south-east. In places, particularly where the gravel is at its lowest in the southern and eastern parts of the site it is directly overlain by peat. Elsewhere the gravel is overlain by a horizon of generally sandy or silty alluvium, which was in turn overlain by peat in most boreholes. The peat is recorded at elevations of between -3.4m and c.0.6m OD, with an indication in several locations of two distinct episodes of peat formation separated by a mineral-rich alluvial sediment. These peat horizons are indicative of periods of semi-terrestrial conditions, which would have enabled the growth of wetland vegetation and potentially allowed the utilisation of the area by prehistoric people.
The peat is overlain by a thin horizon of generally silty and clayey alluvium that is indicative of an inundation of the peat surface. This deposit lies directly beneath modern made ground deposits and corresponds with material observed in the base of two of the excavated trenches.
Information from draft report. Final version awaited.
P. Watkins (HES), 17 March 2023.