Case Studies

The site is currently used a further education facility and has extensive areas of soft landscaping. However, it had previously been part of the Ford Dagenham motor works and whilst remediation of the site had taken place, there were concerns over the potential ongoing issues specifically related to shallow soils. The remediation had consisted of a shallow capping layer over approximate 10m of made ground which is thought to have originated from nearby foundry operations. The capping layer consisted of site won materials that had been screened during remediation.

The purpose of the investigation was to establish whether a risk was present to users of the site as a consequence of contaminants in the shallow soils used for capping and whether there may be a risk to the wider environment as a consequence of contaminants present within the made ground. Unusually for a Phase 1 investigation, we did not consult historical maps, geological and environmental data due to the large number of site investigations that had previously been carried out along with details of remediation. This was used along with a visit to the site to carry out a visual inspection to produce a conceptual model and preliminary risk assessment. This determined that the main risk to site users resulted from the potential presence of asbestos in shallow soils. It was also considered that the risks to controlled waters were minimal.

This allowed us to constrain the scope of the intrusive investigation that followed to investigating shallow soils i.e. depth of investigation was restricted to 1m below ground level. This in turn meant that costs could be restricted for this phase.

A site investigation was required to satisfy a planning condition. Wesson Environmental carried out a desk top study in the first instant. This concluded that the risk to future site users and the wider environment was negligible.

However, the environmental health officer felt a potential risk may still remain as a consequence of waste on the site and from potential gas arising from infilled ground.

The desk top study and conceptual model was revisited. This concluded that the waste materials present on the site were unlikely to pose a risk due to their constituents. Furthermore, because of the presence of hardstanding throughout the development, even if contaminants had been present, there would be no contaminant pathway impacting site users. Furthermore, infiltration would have been reduced making leaching of contaminants from soils unlikely and therefore mitigating impacts to controlled waters. Furthermore, it was considered that if land had been filled that putrescible waste would have been used and that low permeability deposits would be present that would mean that migration of landfill gas would be minimal in any case.

The environmental health officer reviewed the additional information and was satisfied that the additional information was sufficient to show that risks to site users and the wider environment were negligible. Consequently, no further investigation measures were necessary.

Prior to the sale of the site we carried out a desk top study to determine potential future liabilities arising from contaminated soils on the site due the former uses. A potential risk was identified from potential contaminants in site soils to both future site users and to controlled waters. Consequently, an intrusive investigation was recommended to be carried out to further clarify the potential risks from contaminants in site soils.

It was evident from the history of the site, that it had been used for military purposes. Therefore, an unexploded ordnance (UXO) risk assessment was carried out to determine the potential presence of UXOs on the site. This indicated that it had been used as a Royal Ordnance Depot and by American forces during WWII. Therefore, during advancement of boreholes, it was necessary to employ UXO support personnel to clear each exploratory location which required co-ordination between our site engineer, drilling crews and the UXO specialist.

Drilling proceeded across the site using windowless sampling techniques to allow soils to be samples, strata to be logged and groundwater monitoring wells to be installed. On site screening of soils for volatile organic compounds (VOC) and petroleum hydrocarbons (TPH) was carried out using a photo-ionisation detector. This enabled us to reduce the amount of sample undergoing laboratory analysis for these contaminants to a minimum which reduced analysis costs substantially whilst still allowing screening of samples from across the site. No evidence of UXOs was encountered during the site investigation and risks from this source were determined to be negligible. Analysis of soils indicated that only nickel exceeded the relevant Generic Assessment Criteria (GAC) for a commercial land use in a single location, whilst asbestos fibres were detected in a single location. In the case of the former, it was recommended that soils be excavated and disposed of in the hotspot area with risks being considered minimal if hardstanding was present. Risks from asbestos were considered to be negligible due to the presence of hardstanding in this location. Limited groundwater was present in the monitoring wells that were installed and whilst concentrations of TPH compounds were elevated compared to the selected water quality standard, it was concluded that because of the geology encountered on the study site, it was unlikely that the soils posed a risk to controlled waters.