1. Characterization & Remediation of Contaminated Sites Aim To illustrate the role of Site Investigations in : Risk Assessment (Site Prioritisation) and Risk Management (Remediation process selection and validation). Risk Assessment –Site Investigation Risk Management –Remediation Objectives –Process Selection

2. Assessing the Risks from Contaminated Land Tools are needed to determine whether: The soil is uncontaminated. (safe) The soil is contaminated but presents no unacceptable additional risks to the specified target. (safe) The soil is contaminated and may present additional risks to the specified target. (further investigation) The soil is contaminated and presents an unacceptable risk to the defined target. (remediation required)

3. Overview of Risk Assessment Phased Approach Collection of Data Conceptual model (source-pathway-receptor linkages) Identify and assess Hazards (Site Characterization) Evaluate and Quantify Risks posed by Hazards –Professional judgement –Generic Guidelines or screening values –Models (site-specific characteristics) Prioritise sites –fair and transparent process

4. The Role of Site Investigations in the Remediation Process Identification of Site Preliminary Investigation Planning of Investigation – possible Exploratory Investigation Main Investigation (Detailed Investigation) Hazard & Risk Assessment Identification of Remedial Options Selection of Preferred Remedial Strategy Monitor Implementation Validation Long-Term Monitoring Phases

5. Preliminary Investigation Desk Study –Current Layout - buildings, drains, process areas, plant, services. –Materials - feedstocks, products, wastes –History of the site Industrial uses previous incidents Disposal records –Geology and Hydrology desk study information obtained from: –Maps, photographs, local history, directories, Technical Literature, Local / Government Bodies, residents, workers

6. Preliminary Investigation Site Reconnaissance (Site Walkover) –External observation of acute hazards (ruptured tanks, etc) –Visual inspection for Contamination discoloured soil, deposits, odours, gas (detection tubes) vegetation - chlorosis, stress condition of fences, metal structures seepage through river banks, land drains –Activities on neighbouring land (on-going) –Confirms Desk Study details (e.g buildings / services/ plant location) –Produce Photographic Evidence Planning of Subsequent Investigations –Best estimation of the extent of contamination on the site

7. Exploratory Investigation Used to confirm presence of contamination where the Preliminary Investigation is inconclusive –Informed sampling locations Geophysical techniques –Sampling locations can form Stage 1 of the Main Investigation –Composite samples (surface grab samples) –Soil depth profile samples (Window sampling) –Restricted range of chemical analysis (targeted e.g. BTEX) –helps with Planning of the Main Investigation

8. Main Investigation Planning –Safety Procedures exploring the unknown –Environmental Protection dust suppression, Wheel wash, decontamination Sampling –Data Requirements specific requirements of Regulatory bodies informed sampling strategy (preliminary investigation) –Methods augering, window, trial pits and trenches, boreholes

9. Main Investigation Chemical Analysis –Quality Assurance NAMAS (National Measurements Accreditation Service) –Standard Suites (ICRCL) –Site Specific Contaminants Interpretation of Data –quantitative risk analysis, prioritisation, remedial targets Cd Pb As Cr Zn Hg Chloride Sulphate Sulphide Cyanide sulphur pH Phenols Toluene extractable Matter (TEM) coal tars mineral oils PAH, PCB, BTEX

10. Remediation target values are set by: Guideline Values (e.g. Background or Threshold) Site-Specific Risk Values –CLEA Model –ConSim Model Practical Considerations include: Cost Time Required Technical Feasibility The opinions of the Regulator (LA or EA) Remediation Targets

11. Guidelines and Standards Standards –system of fixed, legally binding values (not particularly relevant to the soil situation. Why?) Guidelines values to be applied with Professional interpretation and judgement. –ICRCL (Interdepartmental Committee on the Remediation of Contaminated Land) –BRE (Building Research Establishment) –Dutch Intervention and Target Values

12. Guidelines and Standards ICRCL 58/93 Contaminant Complex Cyanides PAH Proposed Uses Domestic gardens, allotments Landscaped Areas Buildings, hard cover Domestic gardens, allotments, play areas Landscaped areas, buildings, hard cover Threshold 250 50 1000 Action 1000 5000 no limit 500 10,000 Trigger Values (mg/kg air-dried soil)

13. Quantitative Risk Assessment Human Health –CLEA Model (Contaminated Land Exposure Assessment) –C-soil Model (Netherlands) Groundwater (Dispersion) –ConSim Model (Environment Agency)

14. Human Health Contaminated Land Exposure Assessment (CLEA) Site Specific Data –Contaminant concentrations –Climate - precipitation, wind –Soil Properties physico-chemical, pH, redox particle size distribution permeability organic content –Site Use user activity patterns (visit frequency/duration) –Monte Carlo Exposure Estimate Probability Density Functions (PDF) compare with Tolerable Daily Intake (TDI)

15. Risk to Groundwater ConSim Model (Environment Agency) Determines whether contaminant is likely to exceed WQS value at several locations in the aquifer Multi-Tiered Approach –(i)Leaching - (ii) Migration - (iii) Dispersion/Diffusion –Tier (iv) for complex geology Monte Carlo model –input data as PDF (Skill !) –addresses element of uncertainty –decay and biodegradation are calculated –output data graphical

16. CONTAMINATED SOIL Level 1 Level 3 Dilution Dispersion Biodegradation Level 2 Unsaturated Zone Retardation Simulated Leach Data Theoretical Leach Properties If Concentration < WQS STOP If Concentration < WQS STOP AQUIFER VADOSE ZONE Multi-Tiered Approach of the ConSim Model

17. Level 1 Level 2 Level 3 Vadose Zone Saturated Zone Multi-Tiered Approach of the ConSim Model Contaminant

18. Remediation Strategy Source –permanent reduction of risks –numerous technical approaches Pathway –risks managed in short to medium term –several different engineering approaches Target –not usually applicable or practicable

19. Remediation Technologies non-technical high technology Soil Disposal Off-Site –Excavation, Landfill Containment –Capping, Barriers Restructuring –Redistribution and Dilution of Material Contaminant Stabilisation, Removal and Destruction –Numerous Biological, Physical, Chemical, Thermal Methods Relatively low cost, and simple. Considerable experience. Expensive, complex, Emerging Technologies

20. Remediation Technologies In-Situ Treatment without physically removing the soil –Advantage - less disturbance, emissions, buildings, buried services –Disadvantage - out of sight, monitoring, heterogeneity of contamination, soil structure (occluded clay lenses), mass transfer limitations, toxic hot-spots. Ex-Situ Treatment after physical removal of soil –Advantage - Mixing distributes contaminants, mass transfer, process control, treat graded fractions, representative sampling, improved rate, protects groundwater. –Disadvantage - more work, space requirement, emissions, avoid buried services, aesthetic appearance

21. Remediation Technologies Intensive Process –Aim to achieve a rapid rate of remediatiohn –uses complex equipment –consume considerable resources power, reactants, labour, monitoring –Generally detrimental to soil structure –Examples - Soil Washing, Incineration Extensive Process –Slower to Work –Low capital and Maintenance Costs –Soil Structure retained (Improved) –Examples - Phytoremediation, Bioremediation