Soil Remediation for The London 2012 Olympic Games Damilola Sunmonu and Amy Wright

The Vision of the London Olympic Park

On the 27th July-12th August 2012 the Olympic Games will be hosted at the Olympic Park in Stratford, London. The site selected as the main focus for key infrastructure will house the new Olympic Stadium seating people, aqua-park and velodrome amongst others. London 2012 Olympic Games

Key Facts £9.3 billion total project cost £800 million total soil remediation project cost Site is 2.5km 2 in area A high-tech laboratory has been set up on the Olympic Park Approximately 3000 site investigations carried out 2,000,000m 3 contaminated earth moved 80% of 1,000,000m 3 of contaminated soil cleaned and reused on site Over 20,000,000 gallons of contaminated groundwater on site

Soil Contamination The site became heavily contaminated as a result of historic industrial activities over hundreds of years Previous uses since Victorian times included landfilling, a soap factory, gas works, the Hudson Bay Fur Deposit and a number of heavy industrial operations Contaminants of most concern included: Heavy Metals such as lead, arsenic and chromium Organics such as fuel oil, tar and bitumen Other materials such as ammonia and localised chlorinated hydrocarbons

Land Contamination

Remedial Options Removal of contaminated soil hotspots Groundwater remediation down to river alluvium Improvement of soil quality through enabling works including: Soil Sorting – 2,000,000 tonnes Soil Flushing Soil Washing – 1,000,000 tonnes Bioremediation (large scale composting) – 50,000 tonnes Chemical Stabilisation

First Step - Soil Sorting Finer soils were screened out Waste was handpicked to remove wood, leather and material sources Oversized items including bottles, bricks and concrete were crushed and re-used around the park for temporary works such as roads and piling mats During the process all precautions were taken to ensure the site remained safe in the event that thorium was found, but luckily the soil contained no radioactive material

Site Flushing Site flushing was used in specific areas to remove Non-Aqueous Phase Liquids (NAPL) which include substances such as oil A large volume of water and chemicals was used to raise water table in a sectioned area Advantages Relative fast and inexpensive In situ Disadvantages Can be expensive/difficult if many wells/chemicals needed Handling chemicals can be dangerous Chemicals left behind after cleanup may be harmful

5 on site soil-washing machines have cleaned almost 1,000,000m 3 of soil The machines add water to soil and separate it from contamination by either shaking or leaving it to settle and filtering out clean sand or gravel that is safe to reuse The washing process works by stripping the contamination away from the larger particles and concentrating it in the finer silts and clays Further testing and treatment minimises the amount of material that has to be sent to landfill because it can’t be reused The soil washing machine also uses powerful magnets to draw scrap metals out of the contaminated soil, which is often found in ground that has been 'made' from rubble or landfill. Soil washing

Soil Washing

Bioremediation The use of microorganisms to attack specific contaminants It is being used in support of soil washing Natural microorganisms -Fungi - Bacteria Short term process Benefits New high tech sustainable method of cleaning Disadvantages Not all contaminants can be treated using bioremediation such as heavy metals

Chemical Stabilization Used to trap contaminants under the ground An additive is added to the soil to chemically bind with the contaminant Micrometer iron based additives have been developed - iron and iron oxide The contaminants are chemisorbed by the oxide and the metallic iron crystallizes around them to lock them away. By reducing their solubility and bioavailability, the contaminants can become chemically benign in the soil

Other Potential Methods Flowers- Planting of specific varieties of flora which will absorb contaminants over time Dig and Dump- dig up the contaminated soil and take it away to landfill Thermal Treatment- can be used as a larger scale bioremediation technique

Conclusion The combinations of techniques used allowed: The site clearing operation to finish earlier than planned The construction phase to begin ahead of schedule Transportation costs to be kept to a minimum (in-situ methods used) Environmentally friendly (minimum amount of waste taken to landfill)

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