Petroleum Hydrocarbons in Groundwater: Review …...Petroleum Hydrocarbons in Groundwater: Review and Application of CL:AIRE Guidance Duncan Cartwright CGeol CSci Presentation Overview

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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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