Lagoon Sediment Encapsulation & Restoration

The remediation design was developed and implemented by Soilfix within a highly complex site setting including adjacent rivers, a railway, smooth newt protected habitats and further sensitive site ecology. The subject lagoon, could not be dewatered in advance, as modelling indicated that this had the potential to mobilise naphtha tars with unacceptable potential impact on the adjacent ASSI, SPA and RAMSAR sites.   The works presented complex site health & safety challenges, including the placement  / removal of a 22 tonne long-reach excavator onto a floating pontoon and vapour emissions from an aquatic environment.

OUR SOLUTION:

Works developed and delivered by Soilfix included the following works:

· Deployment of a floating silt curtain and oil absorbent boom across the lagoon to protect the downgradient Natural Treatment System;

· Controlled placement of Organoclay Reactive Core Mat® (RCM-OC) panels across 5,500m² of tar impacted lagoon sediments, using a long-reach excavator fixed to a floating pontoon;

· Controlled placement of RMC-OC across 1,000m² of tar impacted berms located centrally within the lagoon;

· RCM-OC rolls deployed via a spindle and held in place by a support excavator working from the waterside – each roll was aligned using GPS equipment and sunk using ballast bags through up to 10ft of water column;

· RCM-OC rolls  anchored using a bespoke approach using geo-socks filled with ballast, and a nominal 200mm thickness of imported clean ballast emplaced across the entire base to protect the RCM-OC and provide a suitable strata for benthic organisms to grow; and,

· Bespoke verification of roll installation and capping layer placement using underwater cameras, GPS enabled plant and pre/post bathymetric surveys; and,

· Capping 2nr berms containing residual tars with lapped rolls of RCM-OC fixed in place, sealed around the edges with Organo-clay AquaBlok® pellets and capped with ballast.

Successful installation of combined remediation technologies rarely utilised in UK / Ireland with a bespoke, innovative and robust site verification process. The works were delivered to programme with Zero lost time accidents and Environmental incident.