Permeable Reactive Barrier (PRB) Decommissioning, South Eastern UK

Client: Pharmaceutical Sector
Date: 2019 – 2020
Nature of works: Permeable Reactive Barrier (PRB) Decommissioning
Contract Value: £600k

Soilfix were contracted to carry out the decommissioning of Europe’s longest Permeable Reactive Barrier (PRB) at a former pharmaceutical manufacturing plant.

The Challenge
An 800m long PRB was installed directly adjacent to a live railway along the site boundary in 2000, prior to the cessation of site operations activities in 2013.  The system was designed to treat a suite of groundwater contaminants of concern and reduce the potential for their off-site migration while site-wide remediation works were carried out.

Following confirmation that groundwater quality had improved to an acceptable standard, the PRB became redundant and required decommissioning in a safe, sustainable and cost-effective manner.

Our Solution
Soilfix designed and implemented a multi-disciplinary decommissioning scheme, including:

• Dewatering, excavation and breakout of 22nr. concrete treatment chamber caissons housing the GRP treatment vessels;
• Dewatering, cleaning and removal of equipment from 20nr. further recharge chambers;
• Pumping of 300 tonnes of spent granular activated carbon (GAC) from treatment vessels and removal off-site for sustainable regeneration;
• High-pressure cleaning of caissons, cutting of pipework /infrastructure and grouting all inlets under confined-space entry procedures;
• Safe lifting and high-pressure cleaning of the GRP treatment vessels prior to off-site disposal once rendered ‘environmentally clean’;
• Breaking through the low-permeability barrier to re-establish groundwater flow at 19 locations;
• Import/placement of clean permeable backfill to meet the client’s strict compliance criteria;
• Disposal of all soils, contaminated liquids/sediments off-site under full Duty of Care; and,
• Health, Safety & Environmental controls to meet the client’s exacting standards.

All works were completed on programme and to budget, with zero lost-time incidents/accidents, in spite of significant hazards including solvent contamination, confined space entry, temporary works, lifting operations and the adjacent live railway.