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Greenwich Peninsula.

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Presentation on theme: "Greenwich Peninsula."— Presentation transcript:

1 Greenwich Peninsula

2 The Site 300 Acres East London
Now the location of the Dome and the millennium village

3 Site History Heavy industrial use Ordnance factory Power station
Bronze foundry Lime works Largest gasworks in Europe Built in 1884 Production ended in 1977 Tar distillation Benzol plant Chemical works Power station Steel processes plant Domestic waste landfill

4 Contaminants Present Coal tars Polyaromatic hydrocarbons Phenols
Benzene and other VOC’s Cyanides and heavy metals Sulphur compounds Ammonia Structural debris 130 underground tanks upto 36m diameter, 8m depth

5 Spread of Contaminants
Increasing levels of industrial pollution further north Abandoned industrial structures ‘Hotspots’ across the site Tar well 36m diameter, 8m deep full and capped BTEX, cyanide and PAH also present Several remediation methods used

6 Remediation Began in 1996 Scale of the work 4 Years, total cost £202 m
Site was designated as the area for the national millennial exhibition British Gas required to undertake statutory remediation clear target contaminants that would pollute 3rd party land and aquifers English Partnerships followed with development remediation Scale of the work “probably the largest single remediation of a single site undertaken in this country”(ICE newsletter for the north western local assoc, 1998) 4 Years, total cost £202 m

7 Remedial Techniques Off-site disposal Containment
Dry processing Containment laterally and vertically Soil & Gravel washing Soil vapour extraction Groundwater treatment

8 Off-site Disposal & Dry Processing
m3 removed to landfill To minimise disposal m3 dry-screened Courser fractions tend not to contain contaminant Only contaminated fines were landfilled

9 Soil & Gravel Washing Theory Ex-situ process Principal processes:
mechanical separation/aqueous leaching, to remove contaminants from sediment Principal processes: removal of surface bound and absorbed contaminants into a treatable aqueous medium separation of contaminated particles from the soil matrix for treatment/disposal exploits tendency for contaminants to absorb on to silts and clays

10 Soil & Gravel Washing 22 000 m3 contaminated soil processed
65% reused Cutoff size 2mm diameter Material < 2mm put through washing process Material > 2mm relatively clean so was reused without further treatment Material processed Material excavated Products from on-site crushing of old foundations

11 Soil Vapour Extraction
Theory in-situ technique induce airflow through soil to enhance the volatilisation and aerobic biodegradation of contaminants The problem VOCs were concentrated mainly in made ground of 1-4m depth spread laterally on contact with underlying clays The solution 300 wells sunk and pumps set to work Measurements showed a 90% reduction in contamination

12 Containment The Problem
Impossible to remove all contamination from the site Necessary to ensure that remaining contaminant could not effect… River Thames Underlying aquifer People using the site Therefore barriers constructed to stop lateral and vertical migration

13 Containment Tar well River Thames
Shallow bentonite slurry cut-off wall, 100m diameter, keyed into clay, constructed around well. Contents removed & hydrocarbon plume extracted This groundwater was treated before discharge into public sewers 50 000m3 contaminated water treated across the site River Thames Bentonite slurry wall constructed 15m back from the river

14 Containment Upward Migration
orange plastic layer installed as a visual aid to limit of contaminated zone 200mm capillary breaking layer of crushed rock layer of low permeability London clay 1.5m clean soil

15 The Result Remedial work has now finished
English Partnerships and Bovis Lendlease are continuing to regenerate the site A third commercial centre for London? A key drive for the transformation of the Thames Gateway

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