Tipner, Portsmouth

The Approach

Cognition was contracted by SEEDA to remediate site soils and groundwater in order to reduce the health risk to future residents. The key elements of these works included;

• Remediation trials investigating a range of treatment options including Soil Vapour Extraction (SVE), Multi-Phase Extraction (MPE), soil washing, chemical oxidation, soil stabilisation/encapsulation and permeable reactive barriers;
• Detailed studies investigating several bioremediation additives;
• Concrete slabs broken out and trial pits excavated to delineate contamination;
• Excavation, chemical testing and delineation of contamination;
• Ex-situ bioremediation using cultured indigenous bacteria, biosurfactants, soil enhancers and nutrients;
• Additional chemical additives applied to soils with a high BTEX concentration;
• Groundwater and surface water treatment;
• Pre-processing/screening of soil;
• Soils stabilised prior to backfill and compaction with upper layers forming piling mats;
• Environmental monitoring and controls put in place to manage dust and odour;
• Clean capping installed across site to protect workforce during construction phase.

The Outcome

Cognition processed 80,000m3 of soil with 30,000m3 successfully bioremediated to meet the agreed re-use criteria and backfilled. Other remediation techniques such as groundwater treatment and a PRB were employed on the site to aid remediation. Treatment and re-use delivered significant savings over conventional disposal, as well as other benefits such as reducing site traffic and disruption in the local area.