Redeveloping brownfield land
The construction of the highway was the centrepiece of the first phase of the project. This involved significant earthworks operations, including the excavation of several embankments to allow the new road to follow the line of the river.
As a brownfield site, however, there were challenges to be overcome in readying it for development. The area was previously occupied by a number of industrial facilities, including power stations, a railway line, gas and sewage works, quarries, and fuel storage tanks. This meant that soil in certain areas of the site could be significantly contaminated.
To remove any risk to the adjacent river and the underlying chalk aquifer, as well as addressing health and safety needs, ESG was engaged to provide support in making safe any soil found to be contaminated as part of the redevelopment.
Laying the groundwork
Prior to ESG’s involvement, an initial study of the soils on the site suggested that large amounts of material would have to be disposed of or treated to mitigate the risk of contamination before the development could be completed. As part of the site was situated over a natural chalk aquifer – designated a Source Protection Zone 1 drinking water reservoir by the Environment Agency – extra care was needed during remedial work to maintain the quality of the local water supply.
With these challenges in mind, the initial study recommended carrying out cement stabilisation for the soils across the site to remove the risk of contaminants being released into the environment. ESG, however, was asked to provide a more precise solution to identify and remediate contaminated soils more effectively and allow cleaner materials to be reused. To achieve this, ESG advised on the remediation and re-use potential of soil from the site, and provided analysis on site as the works progressed.
Analysing the soil
ESG set up two mobile laboratories on site to allow its consultants to rapidly test and classify soil samples. These were crucial, as they helped to significantly reduce turnaround times for material analysis, and allowed the development of a safe soil re-use strategy for the site.
In the first laboratory, ESG undertook chemical analysis of soil samples. The results from this were used to carry out a detailed quantitative risk assessment of data from both the previous investigation and from the new samples. A grid plan of the site was created to map contamination hotspots in a 3D format. This was used to locate and segregate soils in need of treatment from those free from significant contamination. This helped ensure remediation could be carried out as effectively as possible, while identifying material that could be safely re-used in the earthworks for the highway.
The second laboratory was established on site to carry out geotechnical classification of soils intended for use in constructing the highway. Using this information, ESG was able to assess the quality of the materials to be used as part of the construction project.
During the course of ESG’s analysis, lead and oils, as well as other hydrocarbons, were detected in soil from certain areas of the site. The former is a toxic metal that, in high concentrations, can cause acute problems with the nervous system. The latter are carcinogenic and can give rise to health concerns at low concentrations.
With ESG’s guidance and support, it was possible to safely remediate all the soil containing contaminants, removing the risk to the general public and the wider environment.
The contamination management methodology that ESG recommended helped the remediation project to meet the strict requirements of the Environment Agency, as it ensured the on-going quality of the drinking water in the aquifer below.
The benefits of support
Thanks to the support offered by ESG, the initial remedial work within the highway corridor has now been completed, and the customer’s site is now safe for development. The new highway has recently opened, marking the end of the first phase of the project. The construction of homes and commercial premises on the land is due to begin in the near future.
Paul Tilley, operations director, Infrastructure Services at ESG, concluded: “Developers and contractors need to have the right information about the nature and location of any contamination on their site. This information can ensure remediation work is carried out as safely and effectively as possible.
“With comprehensive support from expert consultants and technicians working on site, ESG was able to advise on a contamination management and remediation method statement that met the strict requirements of the EA and the local authority. The presence of mobile laboratories on the site significantly reduced testing turnaround times for the customer, helping to keep the project on schedule.”
For more information on our mobile laboratories, please click here or contact us.