Risk Assessment Contaminated Land

Risk Assessment Contaminated Land

• Objectives– to know the characteristics of soil and chemical

contaminants affecting risk assessments of contaminated land.

– to know the practical steps involved in identifying and quantifying the pollutant hazards

– to know the risk assessment tools and frameworks used to manage contaminated land

• References• Nathanail, Paul.: Reclamation of contaminated land / Paul Nathanail, Colin

Ferguson and Paul Bardos 2003• BURA Breaking old ground: BURA guide to contaminated land assessment and

development 2001• Petts, Judith. Risk-based contaminated land investigation and assessment 1999• Nathanail, C. P Introduction to contaminated land management 1999• Risk assessment for contaminated sites in Europe Nottingham : LQM Press, 1998 • Vol. 1. Scientific basis -- Vol. 2. Policy frameworks 628.5094 RIS• Cairney, T. The re-use of contaminated land : 1995• Environment Agency and DEFRA Websites –

Risk Management of Contaminated Land

1. Introduction

• Subsurface Characteristics - Soils and Contaminants

2. Site Investigation (Hazard Assessment)

3. Interpretation of data (Risk Assessment)

4. Regulatory Frameworks (Risk Management)

5. Remediation (Risk Management)

Course Structure

The Contaminated Land Legacy

Parliamentary Office of

Science and Technology

1993

Expert Estimates:-• 50,000 to 100,000

potentially contaminated sites in UK

• 100,000 to 300,000 hectares

• (significantly less which pose risk to human health)

Type of contaminant Industry/Activity Principal hazards

Toxic metals e.g. Metal mines, iron and Harmful to health cadmium, lead, arsenic, steel works, foundries, of humans or animals mercury. smelters. Electroplating, if ingested directly anodising and galvanising. or indirectly. Other metals e.g. copper, Engineering works, May restrict or nickel, zinc. e.g. shipbuilding. Scrap prevent the growth yards and ship breaking of plants. sites. Combustible substances, Gasworks, power stations, Underground fires. e.g. coal/coke dust. railway land. Flammable gases Landfill sites, filled Explosions within or e.g. methane. dock basins. beneath buildings. “Aggressive” substances “Made ground” including Chemical attack on e.g. sulphates, chlorides, slags from blast furnaces. building materials acids. e.g concrete foundations. Oily and tarry substances, Chemical works, refineries, Contamination of phenols. by-products plants, tar water supplies by distilleries. deterioration of service mains. Asbestos. Industrial buildings. Dangerous if Waste disposal sites. inhaled. (Source: ICRCL Guidance Note 59/83)

Potentially Contaminating Industries

Landfill and other waste disposal sites.

Gas works, coal-carbonization plants and ancillary by-product works.

Sewage works and farms.

Scrapyards.

Railway land, especially large sidings, depots and breaking yards.

Roads, airports and abandoned wartime airfields.

Docks, canals and abandoned or infilled port ancillaries, shipbreaking yards.

Oil refineries, petroleum storage and distribution sites.

Metal mines,, foundries, steelworks, metal finishing works.

Mineral extraction sites not yet infilled (quarries, coal)

Glass works.

Chemical works.

Munitions production and testing sites, wartime installations.

Asbestos works and building incorporating asbestos.

Tanneries and fellmongeries.

Paper and printing works.

Industries making or using wood preservatives, herbicides and pesticides.

Cotton and other textile mills and bleach works.

Metal plating works and yards.

Brickworks, potteries and ceramic works.

Nuclear power stations, radioactive storage/disposal installations .

Law & Legislation

•Common Law (Civil Law)•case law, not specific to CL

•Statutory Law•new regulations specific to CL

Common Law (Civil liability )

Law of Tort (breach of legal duty) i.e. Case Law• Rylands v. Fletcher 1866

– A person bringing a dangerous item or substance onto his own land does so at their own risk

– strictly liable for the consequences of any escape onto another’s land

– substance must be ‘unnatural’ or ‘unnaturally there’– damage must be reasonably foreseeable– conduct of the defendant is irrelevant

• Trespass

– direct, unauthorised interference with another’s property– could cover spillage or deposit of pollutants– not yet tested in the courts

Common Law (Civil liability )• Negligence

• fault based - failure to take care in situations in which damage is reasonably foreseeable

• “care” extends to ‘future users’

• liability is variable depending on the amount of care taken

• does not cover purely economic losses

• Nuisance (interpretation of degree of harm)

• activity that interferes with another’s enjoyment of land

• On-going interference - can obtain an injunction

• Concluded interference - can obtain damages

• foreseeable “omission to do what a reasonable person would do”

• Time Limit - 6 Years

– (begins from time of discovery)

Cambridge Water (CW) v.Eastern Counties Leather (ECL) Ltd

• Perchloroethylene solvent escaped from tannery

• Contamination of groundwater

• Water company failed new EC standards

1. CW failed in High Court

– case of negligence, nuisance, Rylands v. Fletcher dismissed as tanning was not unnatural

2. Prosecution upheld in Court of Appeal

– ECL deemed liable, £1m damages (focused on Nuisance)

3. House of Lords Decision (in favour of ECL)

– reversed the Court of Appeal decision

– no liability under Rylands v. Fletcher as “not foreseeable”

Contaminated land - Disasters

• Love Canal, USA (1978)– Hooker Chemical Company 1942 - 1953

– Building in 1950’s (despite caveat in deeds)

– illness, genetic disorders, residents evacuated

• Lekkerkerk, Netherlands (1978)– building on reclaimed site

– 1600 illegally dumped drums

– drinking water polluted, residents evacuated

• Eastern Counties Leather vs Cambridge Water Co (UK 1993)

Nature of the Pollution

• Some important factors which determine the fate of chemicals in soil.– Organic or Inorganic

– Charge (ions)

– Volatility, Molecular weight

– Solubility, Hydrophilic character

– Functional Groups, affects solubility (polar character)

– Hydrophobic character, interaction with soil colloids

– Quantity or Concentration

– Toxicity and Biodegradability

– Density (Specific Gravity), Viscosity

Soil Structure and Hydrology

• Soil Depth and Horizons

• Organic Matter content– Plant Residues

– Humic Acids, Fulvic Acids, Humin.

• Particle size distribution– Sand, Silt and Clay Fractions

• Soil Permeability

• Groundwater, Water-table– Vadose (unsaturated) zone

– saturated zone

Movement in the Soil

Liquids• Gravity

– vertical movement until sorption by soil matrix dominates.– LNAPL - as far as Capillary Zone or Water Table– DNAPL - through water table, stops at Impermeable Layer

• Advection– transported by the flow of the bulk liquid (water) if dissolved

Vapours• Diffusion

– random molecular movement

• Advection– transported by bulk flow of soil vapour

Movement of Contaminants within an Aquifer

Vadose Zone

Saturated Zone(Aquifer)

Soil Surface

Capillary Zone

LNAPL

Spill

DNAPL

Plume of solublecomponents

Spill

Spill

Potential Outcomes for Contamination in Soil

• Hazard stays fixed in soil matrix = MINIMAL RISK

• Hazard stays fixed in soil matrix but site has receptors = RISK

• Hazard moves into groundwater and is transported towards receptor. = RISK

• Dust and Volatilisation give rise to subsequent Air Contamination. = RISK

Which Are relevant to the site?

REMEDIATION eliminates or minimises RISKS

Typical effects of Hazards

Toxicity to Human Health

– Uptake of contaminants by crops

– Ingestion

– Inhalation

– Skin Contact

• Contamination of water resources (Groundwater)

• Toxicity to Ecosystems / Wildlife

• Fire and Explosion

• Chemical attack on buildings, materials and property

For a contamination to present a risk there must be:

• a potentially harmful Source• a Pathway along which the contaminant can travel.• a Receptor• a plausible Pollution Linkage.

SOURCE RECEPTOR

PATHWAY

Risk Management

Technical Approach to Risk Management of Contaminated Land

What are the key stages in the process?

• Identify and assess Hazards

– Collection of Data

– Conceptual model (source-pathway-receptor linkages)

• Evaluate and Quantify Risks posed by Hazards– Professional judgement– Generic Guidelines or screening values– Models (site-specific characteristics)

• Prioritize sites (Local Authority)– fair and transparent process – Consider consequences of a change in use– force remediation of sites with “Risk”

2. Site Investigation

(Hazard Assessment)

Objectives and Purpose of Site Investigation

• Determine Contamination– nature, source, distribution, extent

– acute effects (structures, biota)

• Geotechnical Information– subsurface structures, cables, pipes, drains

– soil properties, site geology

• Water Environment– groundwater level and composition, local abstraction use

– site run-off to surface waters

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

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/ etc)– Produce Photographic Evidence

• Planning of Subsequent Investigations– Best estimation of the extent of contamination on the site

Exploratory Investigation

• Confirms presence of contamination where the Preliminary Investigation is inconclusive– neither investigation can prove the Absence of contamination

– Informed sampling locations

– Sampling locations can form Stage 1 of the Main Investigation

– Composite samples

– Soil profile samples (depth)

– Restricted range of chemical analysis (targeted e.g. BTEX)

– helps with Planning of the Main Investigation

Main Investigation

• Planning– Site Access

– Safety Procedures • clothing, respiratory, hygiene, confined space.

• sample labelling, transport

• Accident Procedure, First Aid.

– Environmental Protection• dust suppression, Wheel wash, decontamination

– Data Requirements• specific requirements of Regulatory bodies

• sampling and analysis strategy

– Long Term monitoring Requirements

Main Investigation - Sampling Strategy

Requirements to be addressed:• Nature of sample

– air, water, soil

• Sample Type and Size– spot, or composite (mixed)

• Collection and Storage– containers, temperatures

• Method of sampling– surface– augering– Trial pits and trenches– Boreholes - soil, water, gas

• Depth

• Pattern and Frequency of sampling

Main Investigation - Sampling Strategy

Grid Size

Site Size Grid Size

(hectares) (m)

0.5 10

5 20

16 30

Number

Site Size Number

(hectares) of Samples

0.5 5

1 9

5 20

Main Investigation - Chemical Analysis

• Quality Assurance– NAMAS

• National Measurements Accreditation Service

– Accuracy• Submit a prepared control sample (known value)

• Scope– Specific Analysis

• based on Exploratory Investigation or Desk Study

• Standard Suites

Cd BPb HgAsCrZn

ChlorideSulphateSulphideCyanidesulphur

pHPhenolsToluene extractable Matter (TEM)coal tarsmineral oilsPAH, PCB, BTEX

Main Investigation - Gas Analysis

• In-Ground Gases

– methane, hydrogen sulphide

– VOC

• On-site Methods

– Geophysical (conductivity/magnetic field)

– Remote Imaging (IR for methane)

– Spot Sampling• Portable Instruments (GC, IR)

• Detection Tubes (Drager)

• Laboratory Analysis

– sample collection (Tedlar bags)

– standard analytical equipment

3. Interpretation of Contamination Data

(Risk Assessment)






• Evaluate and Quantify Risks posed by Hazards– Professional judgement– Generic Guidelines or screening values– Models (site-specific characteristics)

• Prioritize sites (Local Authority)– fair and transparent process – Consider consequences of a change in use– force remediation of sites with “Risk”

Risk Assessment

Tiered “Risk Assessment Framework”

• Tier 1– Risk screening or Preliminary Risk Assessment

• Desk study information

• Tier 2– Generic Quantitative Risk Assessment

• Uses Generic Assessment Criteria (GAC)– i.e. SGV for “typical standard site”

• Tier 3– Detailed Quantitative Risk Assessment

• requires modelling tools (CLEA)

Guidelines and Standards

• Standards– system of fixed, legally binding values

(not particularly relevant to the soil situation. Why?)

• Soil Guideline Values– ICRCL (Interdepartmental Committee on the Redevelopment of

Contaminated Land)

– BRE (Building Research Establishment)

– Dutch Intervention and Target Values

– New UK CLEA derived SGVs

Soil Guideline Values (SGV)

Different “typical land uses” defined

• Residential (with and without vegetable growing)

• allotments

• Commercial / industrial

Certain circumstances are not covered by SGVs and require Tier 3 risk assessment (i.e. CLEA modeling)

• Playing fields

• Schools

• Complete cover by hardstanding

Guidelines 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

250

250

50

1000

Action

1000

5000

no limit

500

10,000

Trigger Values (mg/kg air-dried soil)

Guidelines Examples of SGV (CLEA)

Standard Land Use Cadmium

(mg/kg)

Mercury

(mg/kg)

Arsenic

(mg/kg)

Residential (with plant uptake) 130 8 20

Residential (without plant uptake) 200 15 20

Allotments 130 8 20

Commercial 5000 480 500

Toxicological Data

• TOX Reports (use in CLEA model)– Arsenic, Benzo(a)pyrene, Cadmium, Chromium, Inorganic CN,

Lead, Mercury, Nickel, Phenol, Selenium, Dioxins, PCB, Benzene, Toluene, Ethyl Benzene, Xylene, Vinyl chloride, tetrachloroethane, 1,1,1, trichloroethane, 1,2dichloroethane, tetrachloromethane, Naphthalene, PAH.

• Soil Guideline Value Reports (set the SGV)– Arsenic, Cadmium, Chromium, Inorganic Mercury, Nickel,

Selenium, Lead, Benzo(a)pyrene, Benzene, Ethylbenzene, Toluene, Xylene, Phenol, Naphthalene.

SGV (from CLEA)

• SGV assume a standard site defaults conditions for:– Receptor behaviour

• Age, weight height, skin area

• Exposure frequency, soil ingestion rate, vegetable consumption rate, time on site

– Land Use• Residential, Allotment, Commercial/Industrial

– Depth of Soil• 0.5m for ingestion

• 0.5m for plant uptake

• 0 – 0.1 m for dust inhalation

• 1m for vapour inhalation

Quantitative Risk Assessment

• Human Health– CLEA Model (Contaminated Land Exposure Assessment)

– RISC-HUMAN (C-soil model Netherlands)

• Groundwater (Dispersion)– ConSim Model (Environment Agency)

• Ecosystems

– currently excluded

– wildlife, biodiversity, HC50

– research needed

Human HealthContaminated Land Exposure Assessment (CLEA)

• Site Specific Data– Chemicals

– Climate - precipitation, wind

– Soil Properties• physico-chemical, pH• particle size distribution• permeability• organic content

– Site Use• user activity patterns (vegetable consumption)• building type

– Monte Carlo probabilistic model• Probability Density Functions (PDF)

• compare with Tolerable Daily Soil Intake (TDSI)

Risk to GroundwaterConSim 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

• addresses element of uncertainty

– decay and biodegradation are calculated

– output data graphical, probabilities of exceeding WQS

CONTAMINATEDSOIL

Level 1

Level 3Dilution

DispersionBiodegradation

Level 2Unsaturated

Zone Retardation

SimulatedLeach Data

TheoreticalLeach

Properties

If Concentration

< WQS STOP

If Concentration

< WQS STOP

AQUIFERVADOSEZONE

Multi-Tiered Approach of the ConSim Model

Level 1

Level 2

Level 3

VadoseZone

SaturatedZone

Multi-Tiered Approach of the ConSim Model

Contaminant

Assumptions for Guidelines and Models

• Validity of analytical data– sample errors, heterogeneity of contamination

• Toxicological and Ecotoxicological Reference Dose– databases incomplete

• Predicted No Effect Concentration (PNEC)• Maximum Permissible Risk Concentration (MPC) • Tolerable Daily Intake (TDI)• Negligible Risk Concentration (NC) • Lowest (& No) Observable Effect Concentration (LOEC, NOEC)• Reference Dose (USEPA for carcinogens)

• Uncertainties– contaminant transfer, uptake, availability, synergistic effect,

metabolic detoxification, receptor behavior, soil properties (adhesion), dermal resorption data, average values representing statistical distributions of the exposure factors.

4. Regulatory Frameworks

(Risk Management)






• Evaluate and Quantify Risks posed by Hazards

– Professional judgement

– Generic Guidelines or screening values

– Models (site-specific characteristics)

• Prioritize sites (Local Authority)

– fair and transparent process

– Consider consequences of a change in use

– force remediation of sites with “Risk”

History of Contaminated Land Policy

USA– CERCLA 1980 (SUPERFUND)– SARA 1986

Netherlands– Soil Clean-up Act 1982– policy reversal 1987

UK– ICRCL 1976 (guidance)– EPA 1990 (STATUTORY LAW)– 1993 “consultation”– EA 1995 (STATUTORY LAW)– PPC Regulations (2000) (STATUTORY LAW)

Framework Policy Objectives

• Prevent new contamination

• Deal with unacceptable risks to human health and the environment (Environmental)

• Bring contaminated land back into beneficial use(Economic)

• to limit cost burdens to proportionate, manageable and economically sustainable levels (Social)

(Sustainable Development)

Contaminated Land Regime

Environment Act 1995• Section 57 (EA 1995) inserts Part IIA into

the Environmental Protection Act 1990• Local Authority responsible• LA to formulate Strategy by mid-2002• LA actively identify contaminated sites &

cause them to be remediated

Definition of Contaminated land

• “Contaminated land is any land which appears to the regulatory authority, by reason of substances in, on or under the land, that:

a) significant harm is being caused or there is a significant possibility of such harm being caused; or

b) pollution of controlled water is being, or is likely to be caused” (Environment Act 1995)

“harm to the health of living organisms or other interference with the ecological systems of which they form part, and in the case of man, includes {harm to} his property”.

EA 1995 Enforcement Responsibilities

Duties Tasks

• Cause their area to be inspected to identify Contaminated Land

• To determine whether a particular site is “contaminated”

• To Act as enforcing authority for contaminated sites (other than Special Sites)

• Establish responsibility for remediation.

• Determine what remediation is required and to ensure that it takes place.

• Arbitrate on the who bears what proportion of consequent liability.

• Record and maintain prescribed information in a Public Register.

Powers of Inspectors

Section 108 Environment Act 1995 :-• enter at any reasonable time• make any examination or investigation

necessary• take photographs or samples• require the giving of information• order that premises or parts be left undisturbed

EA 1995 Information and Inspection

L.A’s may derive information form a number of

sources to enable an assessment to be made

• Other Statutory Bodies

• Its own Land Use records

• Public Complaint

• Land Owners

Prioritisation/Categorisation

• Part I AssessmentPreliminary prioritisation of sites

into groups for Part II Assessment

under the following headings.

• Development

• Surface Waters

• Groundwater

(This will comprise a desk top study

and can be carried out by

non- specialist personnel)

• Part II AssessmentSites in each group will be

categorised using individual risk

assessment• Priority given first to

“Development Group A”• Site information examined• Site Visit• Establish contaminants, pathway

and risk• Detailed exploratory survey where

indicated

(Expert help will be required)

Part I Assessment

Residential development, school playground or allotment within 50 m

Industrial, commercial development within 50 m or residential within 250 m

Site in agricultural or amenity use including Parks and playgrounds

GROUP AYES

Not KnownNO

GROUP B

NO

YES

Not Known

YES Not Known

NO GROUP C

Appropriate Person

• CLASS “A”

Any person who

causes or knowingly

permitted contaminating

substances to be IN, ON

or UNDER the site

• CLASS “B”

Where reasonable enquiry

has failed to identify a

person fitting the definition

of “Class A”, the owner or

occupier of the land

If no Class A or Class B then site is an Orphan Site (ownership passes to LA)

Appropriate Persons - Exclusions

• Class A – for abandoned mines

• Class B - where pollution is to controlled water

• Class B – for contaminants escaping to adjacent land

• Class B - when they act in official capacity e.g. ‘insolvency practitioners’, ‘official receiver’

• Class A – where land was sold with ‘information’ regarding level of contamination

Apportionment of Liability

Inherited Problems

• “Person A” causes contamination of “Contaminated Land X”

• Innocent “Person B” becomes owner/occupier of “Contaminated Land X”

• “Person B” not liable to remediate “Adjoining Land Y” unless they had knowledge of the contamination at purchase (Caveat emptor)

migration

Adjoining LandContaminated land

X Y

Contaminant

Special Sites

Environment Agency becomes the enforcing authority after LA designates a site as a Special Site on the basis of:

• Water Pollution Cases– Controlled water used for Drinking Water abstraction– Ecologically important sites (SSSI, reserves)– Major Aquifers

• Industrial Cases– Pollution from sites involving Acid tar, Oil, Explosives, and

Nuclear (excludes coal processing)• Defence Cases

– Army, Navy, Airforce, Weapons Testing sites

Extends to contaminated sites adjacent to above cases

EA 1995 Remediation Notices

Where Pollution Linkage is confirmedRemediation Notice served on each “appropriate person”

• Can cover assessing site condition (detailed intrusive Site Investigation), preventative works, remediation and monitoring

• Must be “reasonable” having regard to cost and seriousness of harm/pollution

• Must be preceded by consultation (an opportunity for voluntary action)

Attributing Costsfor Remediation Actions

• Single-Linkage Action• Shared-Action (when more than than one pollution-linkage)• Single Liability Group• Multiple Liability Groups

Complex Variable Attribution of Responsibility. The costs may be shared:– Equally– In proportion to capital assets in the land (multiple Group B)– In proportion to costs relating the contamination caused be each member (multiple Group A)– As the enforcing authority sees as just and fair

Non-Compliance withRemediation Notice

• Enforcing Authority can carry out the remediation and recover costs.

• Non-compliance is a criminal offence, punishable by imposition of a fine of up to £20,000 plus £2,000 a day.

Recovery of Costs

Local Authorities must take into account:

• HARDSHIP

LA must consider any hardship that may be caused.

• BUSINESS CLOSURE OR INSOLVENCY

Where remediation costs would make a business insolvent, the authority should consider a reduction in costs. The main aim is to recover as much cost as possible without causing insolvency.

EA 1995 Public Registers

Will be maintained to include:

• Remediation notices and appeals.

• Remediation work carried out following a remediation notice.

• Conviction for offences.

EA 1995 Conclusion

• CL Regime brought into force 2000.

• Local Authorities published Strategy 2002

• New regime extremely complex and bureaucratic

• Lack of significant new resources

• Responsibility for “orphan sites”

Pollution Prevention & Control (PPC) Regulations 2000

• IPPC Directive (96/61/EC)

– enacted in UK as “The Pollution Prevention and Control (England and Wales) Regulations 2000”

– Contaminated land covered under requirements for ‘Site Reports’

– Regulator is ‘Environment Agency’


Principle of PPC

• Specific Industrial Sectors are regulated

• Aim to preserve land quality rather than deal with Historic pollution (I.e. stop

future pollution)

• Linked to Permit Application

– authorises the site (or installation) to conduct specified industrial activity

• Process requires ‘Site Report’

– a detailed investigation of current state of the land that acts as a ‘baseline’

• Closure of Site (or Change of Use)

– Cessation Site Report compared with Original Site Report

– Site must be remediated to ORIGINAL CONDITION and not ‘Suitable for use’


• Purpose of a Site Report

– To document the condition of the site with particular reference to substances in, on or under the land that may constitute a pollution risk

– All land of the installation is covered

• Phased approach

– 1a Desk Study (Conceptual Model)

– 1b Further Desk Study and Exploratory Investigations

– 2 Main Intrusive Investigation

– Complex activities may be zoned

– Technical Content• presentation of lateral and vertical distribution of contaminants

• Site Report sent to LA (as statutory consultee)

– Data can be used by LA under Part IIA EA 1995 legislation

5. Site Remediation

(Risk Management)

Risk Management 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

Remediation of Contaminant Source

• Removal– excavation and landfill (dig and dump)

• Degradation– Bioremediation, Chemical and Thermal destruction

– Natural Attenuation

• Extraction– Soil washing, Vapour Extraction

Remediation - Contaminant Pathway

• Engineering Methods– In-ground Barriers

– Surface Covers• hard cover

• vegetation

– Solidification and Stabilization

– Groundwater pumping

Contaminated land Remediation

• Multifunctionality Approach– always apply highest technical level of clean-up

• Suitable For Use – clean-up level determined by land use– favoured approach based on the “risk-environmental benefit”

residential with gardens residential without gardens parks and recreational areas agricultural industrial and commercial

Risk Based Corrective Action (RBCA)

• The "formal" definition of RBCA is as follows:

“A streamlined approach in which exposure and risk assessment practices are integrated with traditional components of the corrective action process to ensure that appropriate and cost-effective remedies are selected, and that limited resources are properly allocated.”

• The goals of a RBCA process are: – Protection of human health and environment

– Practical and cost-effective application of risk-based decision-making

Natural Attenuation• Spontaneous process

– mostly biological– BTEX half life (chemical =108 yr , biological = <1 yr)

• Long Term

• Risk Based Corrective Action (RBCA)– Environmental benefit v. Cost– may be better to address consequences than to treat the source (e.g.

borehole contaminants)– Lines of Evidence

• Primary

(concentration v. time, concentration v. distance)

• Secondary (supportive)

(DO level, pH, electron acceptors, active microbes)

Monitored Natural Attenuation

• Not a “Do-Nothing” Option– quantify the natural breakdown process

• Monitor Plume– position of the 10 ppm threshold

Receptor

Monitoring wells

Sentinelwell

flow

Documents

Risk Assessment Contaminated Land