petroleum hydrocarbons in groundwater: review …...petroleum hydrocarbons in groundwater: review...
TRANSCRIPT
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Petroleum Hydrocarbons in Groundwater: Review and Application of CL:AIRE Guidance
Duncan Cartwright CGeol CSci
Presentation Overview
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• Provide a brief overview of the guidance and its’ objectives
• Outline the key elements of the guidance
• Highlight some aspects that provide clarity for the risk assessment process
• Provide some insight into application of the guidance
CL:AIRE 2017 - Petroleum Hydrocarbons in Groundwater
Guidance on assessing petroleum hydrocarbons using existing
hydrogeological risk assessment methodologies
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CL:AIRE 2017 - WHAT’S IT FOR?
Petroleum Hydrocarbons • Wide range of constituent
compounds (complex) • Ubiquitous (often the risk
driver)
Complements EA Guidance (RTM, 2006) and Groundwater Protection Principles and Position Statements
Hydrogeological Risk Assessment • Effective • Reliable • Consistent
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SUPPORT & ENDORSEMENTS
Broad Industry Body and Regulator Support
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ELEMENTS OF THE GUIDANCE
CHARACTERISATION and CONCEPTUALISATION SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN ASSIGNING WATER QUALITY TARGETS EVALUATION OF BIODEGRADATION
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THE HARD WORK
A MERE TRIFLE
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CHARACTERSATION AND CONCEPTUALISATION
Constituent Compounds (Mixtures) • Representative Components Physical Properties • Density • Viscosity • Solubility Phases • Vapour • Mobile NAPL • Residual NAPL • Sorbed • Dissolved aqueous phase
Source Specific Factors Geology
• Granular/cohesive • Superficial/bedrock • Layering • Fraction Organic Carbon Hydrogeology • Depth to groundwater • Layered aquifers • Gradients (horizontal/vertical) • Permeability Receptors • Type and distance
A Robust characterisation and conceptual understanding is the foundation to any risk assessment
Site Specific Factors
After CL:AIRE 2014
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CHARACTERSATION AND CONCEPTUALISATION
Constituent Compounds (Mixtures) • Representative Components Physical Properties • Density • Viscosity • Solubility Phases • Vapour • Mobile NAPL • Residual NAPL • Sorbed • Dissolved aqueous phase
Source Specific Factors Geology
• Granular/cohesive • Superficial/bedrock • Layering • Fraction Organic Carbon Hydrogeology • Depth to groundwater • Layered aquifers • Gradients (horizontal/vertical) • Permeability Receptors • Type and distance
A Robust characterisation and conceptual understanding is the foundation to any risk assessment
Site Specific Factors
After CL:AIRE 2014
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SELECTION of CoPC TARGET THE RISK DRIVER CONSTITUENTS
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Relatively Soluble in Water Relatively Mobile Applicable Water Quality Standards
ELIMINATE THE CONSTITUENTS THAT POSE MINIMAL RISK Low Solubility Low Mobility
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WATER QUALITY STANDARDS
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ELIMINATE THE CONSTITUENTS THAT POSE MINIMAL RISK
7x102 (ii)
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WATER QUALITY STANDARDS
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WHO Criteria for TPHCWG – Drinking Water Guide Values
What about risks to surface waters?
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APPLICATION – WHAT TO MODEL?
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INDIVIDUAL COMPOUNDS – INDICATOR COMPOUNDS – CARBON BAND RANGES? PRAGMATIC AND ROBUST – both INDIVIDUAL COMPOUNDS and CARBON RANGES
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APPLICATION – MULTIPLE RECEPTORS
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• Groundwater Resources – Applicable Compliance Point (EA), Drinking Water Standards
• Surface Water Receptors – Distance between Source and Receptor (+Dilution?), Environmental Quality Standards
After SEPA 2014 WAT-PS-10-01
IF NECESSARY MODEL EACH SCENARIO INDEPENDENTLY
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BIODEGRADATION
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Biodegradation is of crucial importance – robust and effective assessment and remediation strategies
Lines of Evidence Approach – Primary (CoPC Concentrations)
– Secondary (Geochem Indicators)
– Tertiary (Microbial Assays)
Environment Agency Guidance R&D 95, 2000
Where demonstrated – natural attenuation of hydrocarbons can result in orders of magnitude difference in Remedial Target Concentrations
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DEMONSTRATING BIODEGRADATION
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Primary Lines of Evidence
Attenuation along the groundwater flow pathway
Attenuation at an individual location (regression analysis) METHODOLOGIES DETAILED IN R&D 95 APPENDICES
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DEMONSTRATING BIODEGRADATION
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Secondary Lines of Evidence
Correlations between Geochemical indicators and CoPC concentrations Assess biodegradation capacity of aquifer (mass consumption over time)
METHODOLOGIES DETAILED IN R&D 95
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DEMONSTRATING BIODEGRADATION
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Tertiary Lines of Evidence
Stable Isotope Probing - Baiting with rare ‘heavy’ C13
CoPC and analysing incorporation into biomass
DNA Quantification Analysis – Are specific genes present and viable
Image courtesy of Microbial Insights Europe www.microbe.com
Image courtesy: Microbial Insights Europe www.microbe.com
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SUMMARY
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Published Guidance is our Friend – Let’s use it CL:AIRE 2017 – Provides the Framework and Key Signposts for Robust, Effective and Consistent Hydrogeological Risk Assessment of Hydrocarbons CHARACTERISATION and CONCEPTUALSIATION is a CRUCIAL part to quantitative assessment FOCUS on the RISK DRIVERS – ELIMINATE the immobile constituents Apply RELEVANT water quality standards and model each source-pathway-receptor pathway INDEPENDENTLY Make use of the TOOLS and METHODS available to DEMONSTRATE Biodegradation
ROBUST, DEFENSIBLE, ACHIEVABLE RISK ASSESSMENT TARGETS
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THANK YOU
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