Environmental Geotecnics1 Environmental Geotechnics Case Study WWII Mustard Gas Factory at Ergethan in the Former East Germany

Environmental Geotecnics2 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 Geotecnics3 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 Geotecnics4 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 Geotecnics5 Primary Contaminants  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

Environmental Geotecnics6 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 Geotecnics7 Recommended Remediation Work Options  20% of site (10,000m 2 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)

Environmental Geotecnics8 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 Geotecnics9 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 Geotecnics10 Gravity Separation & Attrition Scrubbing  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

Environmental Geotecnics11 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 Geotecnics12 Thank you Any Questions???