Environmental Geotechnics Case Study

1. Environmental Geotechnics Case Study WWII Mustard Gas Factory at Ergethan in the Former East Germany Environmental Geotecnics

2. Site Description • WWII Chemical weapons factory • Site in the state of Saxony-Anhalt • Approx 3 Km NNW of the town of Strassfurt • 5.14 Hectares • Former salt mine • Present uses • Dry Cleaning • Steel Fabrication Environmental Geotecnics

3. Introduction • Munitions factories destroyed by Allies at end of war • Many underground tanks missed and have subsequently leaked • Raw materials poorly stored • Bombing destroyed storage and hence caused contamination • Reunification of Germany in 1990 saw the beginning of environmental assessment Environmental Geotecnics

4. Contamination • Complicated cocktail of contaminants • Mustard Gas • Tear Gas • Arsenic • Extractable Organic Halogens (EOX) • Trichloroethane (dry-cleaning) • Zinc • Present in soil, soil gas & groundwater phases Environmental Geotecnics

5. Arsenic Main raw material Values up to 53,500 mg/Kg (ie 5%!) Clean up required at >200mg/Kg for As Extractable Organic Halogens (EOX) Values up to 395 g/Kg Extremely contaminated material Significant clean-up required Primary Contaminants Environmental Geotecnics

6. Proposed Clean-up methods • Inventory of all possibly contaminated sites from archives • Analysis using RAF war-time photographs followed by walk-over surveys • Site survey & sampling (soil, water & gas phases) • Detailed investigation ( including risk analysis) • Remediation & long term monitoring of ground water & aquifers Environmental Geotecnics

7. 20% of site (10,000m2 to a depth of 6m) requires remediation to remove arsenic & associated contaminants Total excavation of site Carried out under full pressure suit conditions Cost of £10 million Subsequent burial of hazardous waste in secure landfill another £25 million Soil Washing (cost of £15million) Recommended Remediation Work Options Environmental Geotecnics

8. Soil Washing • Water-based process for scrubbing soils ex-situ to remove contaminants • Contaminants removed in 1 of 2 ways: • Dissolving or suspending soils in the wash solution (sustained by chemical manipulation of pH for a period of time) • Concentrating soils into smaller volume of soil through particle size separation, gravity separation & attrition scrubbing Environmental Geotecnics

9. Particle Size Separation • Most organic or inorganic contaminants bind chemically or physically to clay or silt particles • Washing separates small Clay & silt particles from larger particles • Effectively reducing volume of contaminated soil Environmental Geotecnics

10. Gravity Separation Removes high or low specific gravity particles E.g. heavy metal-containing compounds (lead, radium oxide) Attrition scrubbing Removes adherent contaminant films Works best on coarser soils Can increase fines in soils Gravity Separation & Attrition Scrubbing Environmental Geotecnics

11. Chosen Remediation • Recommended remediation work: • further detailed investigations as to extent of contamination • Complete site encapsulation & long-term monitoring • Chosen remediation • Site fenced off at cost of £3/metre • Simply waiting for money to materialise to clean-up the site Environmental Geotecnics

12. Thank you Any Questions??? Environmental Geotecnics