Client – Homes and Community Agency

Principal Contractor – Lumsden and Carroll

Consulting Engineer – Halcrow

Location – Stockton-on-Tees

Contract Value – £400K

The North Shore project is located on the north bank of the River Tees adjacent to the Infinity Footbridge in Stockton-on-Tees. Diesel oil based contamination had been detected in the River Tees and investigation identified the source as a number of underground fuel tanks. The diesel was migrating through the groundwater and Ash Remediation Management installed a groundwater treatment barrier to sever the pollution linkage pathway.

Each barrier system installed by Ash Remediation Management is bespoke and numerous design parameters are taken into account prior to installation. Variables considered include its position and depth in relation to the contaminant source, treatment capabilities and design life. These important design decisions are augmented with groundwater modelling and column testing. Prior to the installation of the North Shore barrier, the final design was agreed with the consulting engineer and Environment Agency.

The resulting design was applied using the soil mixing capabilities of a piling rig. The treatment slurry was produced in an automated batching plant and delivered to the rig via a semi automated pumping system. As the auger rotated slurry was injected through the modified drilling head and mixed with the surrounding media. During the mixing process the rig’s on board computer generated real time drilling data which enabled the driver to ensure equal dispersion and homogenisation of the slurry. Drilling data was recorded daily and used in the quality control process.

On completion of installation the regulator approved monitoring scheme commenced. Monitoring wells upstream and downstream of the barrier were sampled for a period of two years. Upstream wells provided data on water quality impacting upon the barrier and those installed downstream illustrated the quality of water migrating through.

The monitoring demonstrated the success of the barrier system and the associated report produced by Ash Remediation Management was approved the Environment Agency.

The project was completed on time, on budget with a zero accident record.

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