contaminated land: dealing with hydrocarbon contamination

Contaminated land: dealing Contaminated land: dealing with hydrocarbon with hydrocarbon

contaminationcontamination

Assessing risks to other Assessing risks to other receptorsreceptors

Environmental Simulations International

Contents of Contents of presentation presentation

Risk assessment for controlled Risk assessment for controlled waterswaters

Risk assessment for ecological Risk assessment for ecological receptorsreceptors

Risk assessments of hydrocarbon Risk assessments of hydrocarbon impact on buildings and servicesimpact on buildings and services


Risk assessment for Risk assessment for controlled waterscontrolled waters

Environment Agency Remedial Targets Environment Agency Remedial Targets Methodology (R&D 20)Methodology (R&D 20)– A tiered (4) methodology for assessment A tiered (4) methodology for assessment

of risk to aquifers and surface water of risk to aquifers and surface water bodiesbodies

Deterministic and probabilistic at different tiersDeterministic and probabilistic at different tiers

– Applied in Part IIA assessments, planning, Applied in Part IIA assessments, planning, etc. when such receptors are identified by etc. when such receptors are identified by the conceptual model as being at riskthe conceptual model as being at risk

– Requires a robust conceptual modelRequires a robust conceptual model


The tiersThe tiers

““in moving through from in moving through from Tier 1 to Tier 4 the data Tier 1 to Tier 4 the data requirements and requirements and resources required resources required increase, but the degree of increase, but the degree of conservatism in the conservatism in the approach decreases and approach decreases and the cost-effectiveness of the cost-effectiveness of the final remedial solution the final remedial solution is likely to improve”is likely to improve”

Dat

a re

quir

emen

ts

Conservatism


Key definitionsKey definitions

Soil Source

GW Source

Compliance Point

Target Concentration

Source Areas

Compliance Point:Compliance Point: Point along pathway where target Point along pathway where target concentration should not be exceededconcentration should not be exceeded

Target Concentration (CTarget Concentration (CTT):): The concentration at the The concentration at the compliance point that should not be exceeded (normally compliance point that should not be exceeded (normally water quality standard or background)water quality standard or background)


Key definitionsKey definitions

Remedial Target:Remedial Target: Source concentration above Source concentration above which remediation is requiredwhich remediation is required– LTC - Liquid Remedial Target (porewater in soil source)LTC - Liquid Remedial Target (porewater in soil source)– STC - Soil Remedial Target (soil source)STC - Soil Remedial Target (soil source)

Soil Source

GW Source

Compliance Point

Target Concentration

RemedialTarget

Concentration


Setting target Setting target concentrations concentrations

Consider: Consider: – Requirements of EU and UK Requirements of EU and UK

Law (e.g. Groundwater Law (e.g. Groundwater Directive)Directive)

– Background water quality of Background water quality of water resourceswater resources

– Whether receptor is a resourceWhether receptor is a resource– Targets should be set to Targets should be set to

provide greatest provide greatest appropriateappropriate level of protectionlevel of protection

EQS, DWS, others?EQS, DWS, others?


Assessment of soil Assessment of soil sourcessources

Effect of soil Effect of soil contamination on:contamination on:– Previously Previously

uncontaminated uncontaminated groundwatergroundwater

– Downgradient receptor Downgradient receptor viavia groundwater groundwater pathwaypathway



Tier 1Tier 1– Are soil pore water concentrations acceptable?Are soil pore water concentrations acceptable?

Tier 2Tier 2– Will the site-specific dilution factor (DF; usually Will the site-specific dilution factor (DF; usually

in groundwater immediately below the source) in groundwater immediately below the source) result in acceptable concentrations?result in acceptable concentrations?

Tier 3Tier 3– Applies attenuation factor (AF) between source Applies attenuation factor (AF) between source

and receptor (downgradient groundwater or and receptor (downgradient groundwater or surface water receptor)surface water receptor)



Tier 4Tier 4– Develops Tier 3 using Develops Tier 3 using

a more detailed and a more detailed and accurate (custom) accurate (custom) simulation of simulation of subsurface processes subsurface processes and geometry to and geometry to determine determine concentrations at the concentrations at the receptorreceptor


Assessment of Assessment of groundwater sourcesgroundwater sources

Effect of groundwater Effect of groundwater contamination on:contamination on:– Previously Previously

uncontaminated uncontaminated groundwatergroundwater

– Downgradient receptor Downgradient receptor viavia groundwater groundwater pathwaypathway


Assessment of Assessment of groundwater sourcesgroundwater sources

Tier 2Tier 2– Is observed groundwater already acceptable?Is observed groundwater already acceptable?

Tier 3Tier 3– Applies attenuation factor (AF) between Applies attenuation factor (AF) between

source and receptor (downgradient source and receptor (downgradient groundwater or surface water receptor)groundwater or surface water receptor)

Tier 4Tier 4– Develops Tier 3 using a more detailed and Develops Tier 3 using a more detailed and

accurate (custom) simulation of subsurface accurate (custom) simulation of subsurface processes and geometry to determine processes and geometry to determine concentrations at the receptorconcentrations at the receptor


Particular hydrocarbon Particular hydrocarbon assessment issuesassessment issues

NAPL phase determinationNAPL phase determination- And will it migrate?- And will it migrate?

Numerous componentsNumerous components– Key representative compoundsKey representative compounds– InteractionsInteractions

History of source and migrationHistory of source and migration– WeatheringWeathering

Past and futurePast and future

– Short circuitingShort circuiting Also by vapourAlso by vapour


Some software toolsSome software tools Remedial Targets MethodologyRemedial Targets Methodology

– Tiers 1-3 onlyTiers 1-3 only ConSim / LandSimConSim / LandSim RAMRAM RBCA Tool KitRBCA Tool Kit RISC WorkbenchRISC Workbench Groundwater modelling packagesGroundwater modelling packages

See benchmarking study in: Whittaker et al., 2001


Why ecological risk Why ecological risk assessment?assessment?

Prevention of significant harm to Prevention of significant harm to designated locationsdesignated locations– Part IIA, EPA 1990Part IIA, EPA 1990– IPPC regimeIPPC regime– Waste Management Regs.Waste Management Regs.– COMAH – limit consequences of major COMAH – limit consequences of major

hazards on the environmenthazards on the environment


What is significant What is significant harm?harm?

Substantial, irreversible impact on ecological Substantial, irreversible impact on ecological system function and endangerment of long-system function and endangerment of long-term maintenance of a populationterm maintenance of a population

Part IIAPart IIA [Impacting] the coherence of its ecological [Impacting] the coherence of its ecological

structure & function, across its whole area, structure & function, across its whole area, that enables it to sustain the habitat, that enables it to sustain the habitat, complex of habitats and/or the levels of complex of habitats and/or the levels of populations of the species for which it was populations of the species for which it was classifiedclassified

PPG9PPG9


A selection of A selection of designated locationsdesignated locations

Sites of Special Sites of Special Scientific Interest Scientific Interest (SSSIs) (SSSIs)

National Nature National Nature Reserve (NNR)Reserve (NNR)

Marine Nature Marine Nature Reserve (MNR) Reserve (MNR)

Other Nature Other Nature ReservesReserves

(candidate) (candidate) Special Areas for Special Areas for Conservation Conservation (cSAC)(cSAC)

Special Special Protection Areas Protection Areas (SPAs) (SPAs)

Areas of Special Areas of Special Protection for Protection for BirdsBirds


Potential receptorsPotential receptors

Soil fertilitySoil fertility– Ability of soil to support plant Ability of soil to support plant

growth and soil fauna critical to growth and soil fauna critical to maintenance of food websmaintenance of food webs

Surface waters and associated Surface waters and associated sedimentssediments– Rivers, streams, ponds, lakes……Rivers, streams, ponds, lakes……

Terrestrial habitatsTerrestrial habitats– Marshland, meadows……Marshland, meadows……

Specific protected speciesSpecific protected species


Principles and Principles and challengeschallenges

The concept of “harm”The concept of “harm”– How to define and quantify harm?How to define and quantify harm?– Which test methods are appropriate?Which test methods are appropriate?– How to define significance?How to define significance?– How do you deal with natural perturbations?How do you deal with natural perturbations?– How do you handle the effects of mixturesHow do you handle the effects of mixtures

Based on source-pathway-receptor linkageBased on source-pathway-receptor linkage– Need conceptual site modelNeed conceptual site model– Identify plausible exposure scenariosIdentify plausible exposure scenarios

Tiered approach/cost-benefit evaluationTiered approach/cost-benefit evaluation


Ecological risk Ecological risk assessment guidanceassessment guidance

Developing but at presentDeveloping but at present– Environment Agency guidanceEnvironment Agency guidance

Tier 1. ScreeningTier 1. Screening Tier 2. Testing and detailed evaluationTier 2. Testing and detailed evaluation Tier 3. Detailed testing and evalationTier 3. Detailed testing and evalation

– SNIFFERSNIFFER Worksheets for numerical targets (NTWorksheets for numerical targets (NTFF, ,

NTNTSS)) Broadly similar to Tier 1Broadly similar to Tier 1


Risk assessment to Risk assessment to structuresstructures

Buildings, foundations, Buildings, foundations, underground servicesunderground services– See Environment Agency R&D report See Environment Agency R&D report

P5-035/TR/01P5-035/TR/01– Particular issues with hydrocarbonsParticular issues with hydrocarbons

Diffusion into water pipesDiffusion into water pipes Entry into sewersEntry into sewers Attack on plasticsAttack on plastics Softening of asphaltSoftening of asphalt


ConclusionsConclusions

The risk assessment frameworks have common The risk assessment frameworks have common basisbasis– Source-pathway-receptorSource-pathway-receptor– Tiered assessmentTiered assessment

All risk assessment frameworks have equal All risk assessment frameworks have equal applicability in Part IIA assessments and applicability in Part IIA assessments and planning processplanning process– It’s more than just CLEAIt’s more than just CLEA

Hydrocarbon is no different in principle to other Hydrocarbon is no different in principle to other contaminationcontamination– But some specific properties need to be consideredBut some specific properties need to be considered

contaminated land: dealing with hydrocarbon contamination

Documents

source concentration

assessment of risk

acceptable concentrations

surface water receptortier

servicesrisk assessment

water quality standard

source result

attenuation factor af