Previous ground investigations had identified the impaction of both soils and groundwater with potential contaminants associated with previous site usages and the associated reports had recommended significant (and costly) soil and groundwater remediation at the site.

Crossfield Consulting was appointed by the design and build contractor to review the factual data and to provide geotechnical and environmental advice.  The contractor was also responsible for the discharge of the ground related planning conditions for the site, which required a site investigation, a remediation strategy, the validation of any remedial works and a piling risk assessment.  

Following a review of the available desk study and ground investigation data, Crossfield Consulting Limited formed a preliminary ground model for the site.  It was identified that supplementary investigation works would be required to satisfy the planning conditions.  It was also noted that, by undertaking additional ground investigation and testing, detailed quantitative risk assessments could be undertaken to potentially reduce the scope of the previously recommended remedial works required at the site.

Crossfield Consulting designed and supervised logical and phased ground investigations to collect the required data to enable detailed quantitative risk assessments to be carried out.  To avoid programme delays, the majority of the works were undertaken whilst the site was still operational and included works both inside and outside of the existing buildings.

Services were present beneath the site and the desk study highlighted a risk associated with unexploded World War II ordnance.  The investigation phase used service tracing and magnetometer surveys to identify service locations and any risks that might apply.  Dynamic sampling, percussion boreholes, trial pits and static cone penetration tests were all used to obtain the necessary environmental and geotechnical data.

Our design of the ground investigation enabled us to produce detailed ground and groundwater models for the site.  Detailed qualitative and quantitative risk assessments were undertaken and Crossfield Consulting demonstrated that there were no significant risks to human health or the water environment.  Following the risk assessments, there was no requirement to remove soils or remediate groundwater to permit the development.

The required remediation at the site was limited to borehole decommissioning, tank removal, the provision of barrier pipes for the water supply and a simple cover system in landscaping areas. Crossfield Consulting produced a Remediation Method Statement for the site detailing how the remedial works should be undertaken and supervised and verified all of the recommended remedial works.  Liaison with the regulators, including the Environment Agency, ensured that our assessment and remediation proposals received timely approvals.

In addition to the environmental assessments, Crossfield Consulting also provided earthworks, retaining wall, foundation and floor slab advice and design parameters.  Due to the site’s environmental setting, it was important that any recommended geotechnical solutions did not create new pollutant linkages.  All solutions were also designed to avoid unnecessary waste disposal costs.  Crossfield Consulting also provided a Piling Works Risk Assessment that was accepted by the Local authority, without the requirement for on-going monitoring.  A piling platform was also designed using site-won materials.

Crossfield Consulting also assisted in the design of the drainage system on this project by designing a soakaway drainage detail that permitted the use of soakaways at the site, without creating new pollutant linkages.  Without the use of soakaways, large and costly attenuation systems would have been required.

Our designed ground investigations and detailed risk assessments demonstrated that the extensive remedial works recommended by others was not required resulting in significant cost and programme savings to our Client.

Liaison with the regulators, including the Environment Agency, ensured that our assessment and remediation proposals received timely approvals and did not delay the works.

All geotechnical solutions provided were designed to minimise waste and to avoid creating pollutant linkages.

Our work ensured that significant cost and programme savings were made with respect to potential ground-related problems.