Contaminated Land Remediation Goals James Potter BSc, MSc, SiLC, - - PowerPoint PPT Presentation

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Contaminated Land Remediation Goals James Potter BSc, MSc, SiLC, - - PowerPoint PPT Presentation

Jan 10, 2023 239 likes •601 views

Contaminated Land Remediation Goals James Potter BSc, MSc, SiLC, CIWM, CEnv Delivering sustainable solutions in a more competitive world Introduction to James Potter James has over 13 years experience in contaminated land investigation,

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Delivering sustainable solutions in a more competitive world

Contaminated Land Remediation Goals

James Potter BSc, MSc, SiLC, CIWM, CEnv

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Introduction to James Potter

  • James has over 13 years experience in contaminated land

investigation, risk assessment and remediation.

  • He worked for 7 years with the UK Environment Agency as Thames

Regional contaminated land officer and was involved in the implementation of the Contaminated Land Regulations.

  • He has worked as a consultant since 2001 and has been involved in

the investigation and remediation of contaminated land sites, including the 2012 London Olympics site and sites in China, Hong Kong and the Philippines.

  • He is a registered Specialist in Land Condition (SiLC). One of only

120 and the only one in Asia. (www.silc.org)

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Content of the presentation

  • What is risk?
  • Obtaining data to calculate risk
  • Remediation Goals
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Risk based approach

  • Standard global approach
  • Pollutant linkage - SOURCE of contamination is

causing (or potentially may cause ) a significant impact to a RECEPTOR via a PATHWAY

  • Conceptual site model
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Conceptual model varies for each site

Future use Ground surface? Industrial use Ecological? Groundwater / surface water Humans ? Basements?

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Risk to humans

  • How toxic is the contaminant
  • Exposure factors – ingestion, dermal and

inhalation based on human behaviour

  • Risk threshold – chance / probability
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Exposure pathways – humans

  • Ingestion
  • Inhalation particulates
  • Dermal contact
  • Volatiles (entry into buildings)

Volatiles from groundwater Volatiles from soil

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Sources of information

  • Toxicity data / generic soil data / exposure data–

US EPA, DEFRA, TPH criteria working group, WHO

  • Site specific data
  • CISED
  • PBET
  • Cropping trials
  • Input data into chosen model
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Toxicity / model values

  • Critical health effects – threshold ? Tolerable daily

intake

  • No threshold – index dose, increased level risk to

health

  • Authoritative organisations –
  • World Health Organisation,
  • Joint Food and Agricultural Organisation
  • USEPA (USA)
  • American Society Testing and Materials (ASTM)
  • DEFRA (UK)
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Chemometric identification of substrates and element distributions (CISED)

  • SITE SPECIFIC
  • CISED tests provide information on chemical

forms of potentially harmful elements

  • Arsenic study – found two major categories of

components in soil

  • Soil calcium dominated
  • Soil iron dominated
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Soil calcium dominated

  • Found a general trend of increasing extractable

arsenic with increasing extractable calcium

  • Calcium components are relatively soluble under acid

conditions

  • Acidic conditions are found in the human gut thus

arsenic associated with the calcium carbonate component is likely to be highly bioaccessible and as such may be more available for adsorption into the body.

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Iron dominated components

  • In the samples where most of the arsenic was

associated with the less soluble iron components

  • Arsenic mobility is lessened and is likely to be less

accessible

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Physiologically based extraction test (PBET tests)

  • SITE SPECIFIC
  • Bioaccessible fractions of contaminant
  • PBET tests simulates gastrointestinal tract

conditions in humans

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PBET findings

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PBET

  • The maximum top soil bioaccessibility factors

ranged from 6% to 54% whilst those for the made ground ranged from 1% to 47%. There was no relationship observed between the maximum PBET derived bioaccessibility factors and either the total soil arsenic or sample depth.

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Cropping Trials – site specific

  • Consumption homegrown vegetables forms a

potentially significant exposure pathway

  • Significance increases as bioaccessibility via

direct soil ingestion decreases

  • Compare Conversion Factor for Root and

CF Leafy with defaults in your model

  • Refinement of CF values was obtained, reducing

the As exposure via homegrown vegetables.

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Use of data used

  • Use in model to calculate your exposure

concentration

  • Calculation of site specific targets – SSAC often

not practical or possible

  • Use available toxicity data to calculate targets for

the proposed FUTURE USE of the site

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Hong Kong - land use scenarios - what is the future use of the site going to be ?

  • Urban residential - high rise, landscaped, children
  • Rural residential - low rise, soil contact, vegetable

consumption

  • Industrial Scenario – adult receptors, industrial

estates

  • Public parks - open space, children, hardstanding

with landscaped soil. Volatiles indoors not considered

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Risk based Remediation Goals

  • Developed by ERM for EPD for use in HUMAN

HEALTH RISK ASSESSMENT

  • Dutch B not applicable
  • Not applicable to other receptors
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Developing RGRB’s

  • Toxicity source data – international and local

sources

  • Model equations
  • USEPA / ASTM
  • Building – ventilation , volatilisation – Johnson and

Ettinger 1991

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Developing RBRG’s

  • Exposure concentrations = RBRG
  • Exposure factor = how humans exposed
  • Toxicity = chemical toxicity of chemical of concern
  • Risk = level of risk perceived to be acceptable

Risk = exposure concentrations x exposure factors x toxicity

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Development of RBRG’s

  • Chemicals of concern
  • 15 metals
  • 13 volatile organic compounds
  • 19 semi volatile organic compounds
  • 2 dioxins and poly chlorinated biphenols
  • 3 total petroleum hydrocarbon ranges
  • Free cyanide
  • Tributyl-tin oxide
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Development of RBRG’s

  • Physical and chemical properties
  • Toxicity data
  • Based on this data the parameter values for each

receptor could be assessed

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Development of RBRG’s

  • Calculations based on
  • Soil threshold for adult ( dose above which an

effect is seen)

  • Soil non threshold for adult / child (as dosage

increase likelihood of effect expected to increase)

  • Using ingestion, dermal inhalation in combination

with body weight, exposure frequency

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Models – similar approach

  • Target value for soil involves
  • Dividing values derived from receptor information (

body weight / averaging time, Exposure frequency/ duration) BY

  • Soil ingestion ( ingestion rate / oral absorption

factor / oral reference dose (RfDo) plus

  • Dermal pathway (skin surface area/soil to skin

adherence/ dermal absorption factor / RfDo

  • Inhalation – particulates / vapour (soil density /

porosity factors / inhalation reference dose

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RBRG’s

  • Soil RBRG – all land use / receptor categories
  • Groundwater – indoor air RBRG –risk from

volatiles

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RBRg’s and NAPL

  • NAPL may be present – site observations
  • Can compare against Csat and Solubility values

generated to determine if further action is required.

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Receptors other than humans

  • Groundwater
  • Surface water
  • Ecosystems – flora and fauna
  • Buildings
  • Commercial crops - timber / grains
  • Cattle / other
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Groundwater risk assessment

  • Groundwater is very precious in some countries

and vital source of drinking water

  • In UK if groundwater considered a receptor would

compare against Drinking Water Standards

  • Then undertake Tier 1, 2 and 3 assessment
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Groundwater remedial targets - SOIL

  • Tier 1 - pore waters / soil eluate / perched water

quality.

  • Tier 2 – attenuation in soil / unsaturated zone and

dilution by groundwater under site

  • Tier 3 – attenuation between source and

compliance point

  • Tier 4 – dilution in receptor / compliance point
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Groundwater remediation targets – groundwater

  • Tier 1 – not applicable
  • Tier 2 – groundwater data is compared directly

with the target concentrations

  • Tier 3 – attenuation between site and

downgradient receptor / compliance point

  • Tier 4 – any dilution effects at receptor
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Ecological risk assessment

  • Tier 0 – pollutant linkage
  • Tier 1 – initial screening does contamination

present an eco-risk

  • Tier 2 – site specific characterisation – biologically

based – bioavailability (cropping / PBET/other )

  • Tier 3 – specific additional measurements to

characterise risk – MAGNITUDE OF RISK

  • Tier 4 – risk un-acceptable management action

required

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Other receptors

  • Building standards – e.g. sulphate / manganese

levels – foundations designed appropriately

  • Commercial crops and herds – similar to

ecosystems

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end of overview

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