The Olympic Delivery Authority scooped the award for the Best use of a combination of remediation techniques at the BB Remediation Awards 2008 for the Olympic Park Project.
The Olympic Park is being remediated by the ODA on behalf of the London Development Agency. The project aims to use sustainable treatment technologies, minimise disposal to landfill, recover materials for re-use and support legacy development.
The technologies being used to achieve these goals are: soil washing, chemical stabilisation, geotechnical stabilisation/solidification, bioremediation, complex sorting, in-situ pump and treat groundwater, simple/primary screening, crushing, and invasive species treatment and on-site burial.
This combination has resulted in over 250,000m3 of material being processed in the last seven months, with around 300,000m3 still to be processed. Its achievement of 80% of soil reuse from excavation and 90% reuse from demolition crushed hard materials exceeds current best practice.
Treatment hubs
The Park is the first to design, procure and maintain a Soil Treatment Centre (hub) within the UK, dedicated to receiving and cleaning/recycling site-derived materials from within the Park's multiple construction zones.
The treatment centres were set up as a single soil washing plant in July 2007 and the main hubs following in January 2008, with soil washing and soil stabilisation equipment common to both the north and south sections of the site. One bioremediation bio-pile system was also set up. Five soil washing plants are in use - the first time that so many plants have been brought together for a single scheme in the UK.
The design of the plants has been continuously under review, as the site-derived materials have varied. High levels of technical support and lab trials have been required to provide recommendations for modifications within the equipment, or changes in water flush rates/volumes and modifications in the density separation additives used within the process.
Further processes
Chemical soil stabilisation has to date processed 35,000m3 of soils, with around 65,000 m3 still to process. Soil stabilisation of river silts and soft alluvium, for material strength enhancement is also being undertaken using in-situ techniques, with up to three specialist Wirgen machines.
Complex sorting machinery designed uniquely for the conditions of one area of the site, a historic landfill, enabled the separation of soil from landfill materials and has been refined and used for the manual abstraction of low grade exempt radiological wastes and asbestos materials.
A bioremediation system has been established in to allow for the processing of soft alluvium or cohesive materials with principally hydrocarbon contamination. Demolition materials in the form of brick and concrete are recycled using a combination of crushing and screening. Site clearance materials are processed on site or sent off site for recycling into new tarmac and compost/chippings.
Groundwater treatment
To treat groundwater, a recirculating pump and re-injection system treats the shallow groundwater from the river terrace gravels for ammonia and hydrocarbons. A light hydrocarbon skimming system, in combination with secondary injection of oxygen release compounds enhances the natural attenuation of residual contamination.
"A hub site on a massive scale, truly taking forward the principle of combining sites and soils and treating through treatment trains." Phil Crowcroft
