117623084 002 r rev2 7000 roar 16042012 final[1]

16 April 2012

REMEDIATION OPTIONS APPRAISAL REPORT

Former ChlorAlkali Plant, Orica Botany, NSW

REP

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Report Number. 117623084_002_R_Rev2_7000_ROAR

Submitted to:Orica Australia Pty Ltd 16-20 Beauchamp Road Matraville NSW 2036

FCAP - REMEDIATION OPTIONS APPRAISAL

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Table of Contents

1.0 INTRODUCTION ........................................................................................................................................................ 1

2.0 BACKGROUND AND PREVIOUS ASSESSMENTS AND REMEDIATION WORKS ............................................... 1

2.1 Human Health and Environmental Risk Assessment (HHERA) .................................................................... 1

2.2 Determination of Contamination Significant Enough to Warrant Regulation ................................................. 2

2.3 Contaminant Fate and Transport Modelling .................................................................................................. 2

2.4 Remediation Technology Assessment (RTA) ............................................................................................... 2

2.5 Remediation Action Plan, 2011 .................................................................................................................... 5

2.5.1 Remediation Objectives .......................................................................................................................... 5

2.6 RAP Implementation Program ...................................................................................................................... 5

2.7 RTA Revision ................................................................................................................................................ 6

3.0 NSW EPA MANAGEMENT ORDER, JANUARY 2012 ............................................................................................. 7

3.1 Remedial Options Appraisal ......................................................................................................................... 7

3.2 Management Order Intent ............................................................................................................................. 7

3.3 Land to Which the Order Applies .................................................................................................................. 8

4.0 SITE SETTING AND FEATURES .............................................................................................................................. 8

4.1 Surrounding Infrastructure ............................................................................................................................ 8

4.2 FCAP Features ............................................................................................................................................. 9

4.2.1 Block G ................................................................................................................................................... 9

4.2.2 Blocks M, L and A ................................................................................................................................... 9

4.3 Summary of Extent of Soil Contamination .................................................................................................... 9

4.3.1 Block G ................................................................................................................................................... 9

4.3.2 Block M ................................................................................................................................................. 10

4.3.3 Block L .................................................................................................................................................. 10

4.3.4 Block A .................................................................................................................................................. 10

4.4 Groundwater ............................................................................................................................................... 10

5.0 REMEDIAL OPTIONS APPRAISAL APPROACH .................................................................................................. 11

5.1 Technical Feasibility ................................................................................................................................... 12

5.2 Effectiveness .............................................................................................................................................. 12

5.3 Sustainability .............................................................................................................................................. 12

5.4 Protection of the Environment .................................................................................................................... 13


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5.5 Cost ............................................................................................................................................................ 13

6.0 SOURCE REMOVAL ............................................................................................................................................... 14

6.1 Technology Description .............................................................................................................................. 14

6.1.1 Remediation Action Plan (URS, 2010) .................................................................................................. 14

6.1.2 Extent of Remediation ........................................................................................................................... 14

6.2 Option Review ............................................................................................................................................ 15

6.2.1 Technical Feasibility .............................................................................................................................. 15

6.2.2 Effectiveness ......................................................................................................................................... 17

6.2.3 Sustainability ......................................................................................................................................... 18

6.2.4 Protection of the Environment ............................................................................................................... 18

6.2.5 Cost ....................................................................................................................................................... 18

6.3 Off-Site Disposal ......................................................................................................................................... 19

6.3.1 Technology Description ......................................................................................................................... 19

6.3.2 Option Review ....................................................................................................................................... 20

6.3.2.1 Technical Feasibility .......................................................................................................................... 20

6.3.2.2 Effectiveness ..................................................................................................................................... 20

6.3.2.3 Sustainability ..................................................................................................................................... 20

6.3.2.4 Protection of the Environment ........................................................................................................... 21

6.3.2.5 Cost ................................................................................................................................................... 21

6.4 Off-site Disposal with Stabilisation .............................................................................................................. 21


6.4.2 Options Review ..................................................................................................................................... 22


6.4.2.2 Effectiveness ..................................................................................................................................... 24

6.4.2.3 Sustainability ..................................................................................................................................... 24


6.4.2.5 Cost ................................................................................................................................................... 24

6.5 Ex Situ Thermal Technologies .................................................................................................................... 24


6.5.1.1 Ex Situ Thermal Desorption (ESTD) .................................................................................................. 25

6.5.1.2 Batch Retorting .................................................................................................................................. 26

6.5.1.3 Incineration ........................................................................................................................................ 27

6.5.1.4 Other .................................................................................................................................................. 27


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6.5.1.5 Vapour Treatment .............................................................................................................................. 27

6.5.1.6 Technology Summary ........................................................................................................................ 28

6.5.2 Option Review ....................................................................................................................................... 29


6.5.2.2 Effectiveness ..................................................................................................................................... 32

6.5.2.3 Sustainability ..................................................................................................................................... 32


6.5.2.5 Cost ................................................................................................................................................... 33

7.0 IN SITU THERMAL TECHNOLOGIES .................................................................................................................... 34


7.1.1.1 TCH ................................................................................................................................................... 34

7.1.1.2 ERH ................................................................................................................................................... 34

7.1.1.3 Others ................................................................................................................................................ 35

7.1.1.4 Vapour Treatment .............................................................................................................................. 35

7.1.2 Option Review ....................................................................................................................................... 35


7.1.2.2 Effectiveness ..................................................................................................................................... 38

7.1.2.3 Sustainability ..................................................................................................................................... 39


7.1.2.5 Cost ................................................................................................................................................... 40

8.0 ON-SITE CONTAINMENT ....................................................................................................................................... 41


8.1.1.1 Technology Summary ........................................................................................................................ 42

8.1.2 Option Review ....................................................................................................................................... 43


8.1.2.2 Effectiveness ..................................................................................................................................... 46

8.1.2.3 Sustainability ..................................................................................................................................... 47


8.1.2.5 Cost ................................................................................................................................................... 48

9.0 REMEDIATION OPTIONS ASSESSMENT ............................................................................................................. 49

9.1 Assessment Criteria .................................................................................................................................... 49

9.2 Evaluation ................................................................................................................................................... 49

9.2.1 Technical Feasibility .............................................................................................................................. 49


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9.2.2 Effectiveness ......................................................................................................................................... 50

9.2.3 Implementation and Treatment Time .................................................................................................... 51

9.2.4 Financial ................................................................................................................................................ 52

9.2.5 Sustainability ......................................................................................................................................... 52

9.2.6 Protection of the Environment ............................................................................................................... 53

9.2.7 Institutional Feasibility ........................................................................................................................... 54

9.2.8 Stakeholder Acceptance ....................................................................................................................... 54

9.2.8.1 Community Consultation .................................................................................................................... 54

9.2.8.2 Regulator ........................................................................................................................................... 55

9.3 Ranking ...................................................................................................................................................... 55

9.3.1 Method A ............................................................................................................................................... 56

9.3.1.1 Approach ........................................................................................................................................... 56

9.3.1.2 Outcome ............................................................................................................................................ 57

9.3.2 Method B ............................................................................................................................................... 57

9.3.2.1 Approach ........................................................................................................................................... 57

9.3.2.2 Outcome ............................................................................................................................................ 58

10.0 PREFERRED TECHNOLOGY IDENTIFICATION ................................................................................................... 60

11.0 REFERENCES ......................................................................................................................................................... 61

12.0 LIMITATIONS .......................................................................................................................................................... 64

TABLES

Table 1: Ex Situ Thermal Treatment Options Summary .................................................................................................... 28

Table 2: Containment Options Summary .......................................................................................................................... 42

Table 3: Ranking Criteria Descriptors ............................................................................................................................... 56

Table 4: Remediation Option Ranking – Method A ........................................................................................................... 57

Table 5: Criteria Categories Summary .............................................................................................................................. 57

Table 6: Remediation Option Ranking – Method B ........................................................................................................... 58

FIGURES (IN TEXT)

Figure A: System Processes at an ESTD plant in Herne, Germany (SITA)

FIGURES (ATTACHED)

Figure 1: Site Location

Figure 2: Impacted Area presented in RAP

Figure 3: Impacted Area presented in RAP


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APPENDICES

Appendix A: Assessment of Costs


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GLOSSARY OF ABBREVIATIONS AND TERMS

Abbreviation/Term Description

AHD

Australian Height Datum - a standard reference point for the elevation of a location.

ANZECC Australian and New Zealand Environment Conservation Council

bgsl Below ground surface level

BIP Botany Industrial Park

Botany Sands The stratigraphic name given to unconsolidated sediments comprised predominantly

of sand which underlie the Orica Plant site and adjoining areas

CAP ChlorAlkali Plant. A chemical plant manufacturing chlorine, caustic soda, and sodium

hypochlorite

CH4 Methane

CFS Chemical fixation and solidification

CHC Chlorinated Hydrocarbon

CLC Community Liaison Committee. The committee established in 1993 in response to the

discovery of groundwater contaminated with chlorinated hydrocarbons beneath BIP

and nearby areas. The CLC is made up of a wide range of members including

technical experts, representatives from the local community and industry,

environmental groups, local councils, state government agencies and other interested

authorities.

CLM Act Contaminated Land Management Act 1997

CO2 Carbon dioxide

CO2-e Carbon dioxide equivalents. Includes the ‘global warming potential’ of methane and

nitrous oxide.

CoBB Council City of Botany Bay Council

DCP Development Control Plan

DoP Department of Planning, NSW (Previously known as DIPNR and DUAP); now known

as Department of Planning and Infrastructure)

DoPI Department of Planning and Infrastructure, NSW (Previously known as Department of

Planning)

DP Deposited Plan

EA Environmental Assessment

ECH Electrical conductive heating

ECS Emission Control System

EMP Environmental Management Plan. Can mean either: a management plan (or series of

plans) prepared by the Remediation Contractor to document proposed environmental

control measures and monitoring programs to the implemented during the remediation

works or a long term EMP (LTEMP) to address the integration of environmental

mitigation and monitoring measures for residual contamination, following remediation

action, throughout an existing or proposed land use

EPA Environment Protection Authority

EPL Environment Protection Licence

ESTD Ex situ thermal desorption


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FCAP

Former ChlorAlkali Plant

GAC

Granular activated carbon

Groundwater Water beneath ground surface

GTP Groundwater Treatment Plant- A chemical treatment plant required to be constructed

for the ex situ treatment of groundwater from hydraulic containment as required by the

Notice of Clean Up Action (NCUA)

ha Hectare

Hazardous Waste Material classified as Hazardous Waste in accordance with the DECC NSW (2009)

Waste Guidelines

Hg The chemical symbol for mercury

Hg0 Elemental mercury

HgO Mercury oxide

HgS Mercury sulphide

HHERA Human Health and Environmental Risk Assessment

Huntsman Huntsman Corporation (Australia) Pty Limited. A BIP company which manufactures

surfactants and other associated products such as brake fluids

Hydrogeology The study of the interrelationships of geological materials and processes with water,

especially groundwater

Inorganic A chemical substance that does not contain carbon

ISTD In situ thermal desorption

LGA Local Government Area

Lithology The geological (physical) character of a rock or soil

LIQUID BOOT® A cold, spray applied, water based membrane containing no VOCs, which provides a

seamless, impermeable barrier against vapour intrusion into structures

Management Order Management Order Number 20111406, Declaration Number 21074, Area Number

3203 issued to Orica under Section 14 of the CLM Act 1997.

Materials Either Imported Materials or Materials excavated from the FCAP.

m bgl Metres below ground level

m bgsl Metres below ground surface level

mg Milligrams

mg/kg Milligrams per kilogram

mg/L Milligrams per litre

microgram (µg) One thousandth part of a milligram (mg) one millionth part of a gram (g); one billionth

part of a kilogram (kg)

NHMRC National Health and Medical Research Council

NSW New South Wales

N2O Nitrous Oxide

O&M operation and maintenance


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OEH Office of Environment and Heritage, which includes the NSW EPA

OH&S Occupational Health and Safety

Organic Compound A compound containing carbon

Orica Orica Australia Pty Limited

PCA Primary Containment Area. Located on Southlands

PCBs Polychlorinated biphenyls

Physical Soil Washing An ex situ soil treatment process during which soils are washed, typically with water, to

remove contaminants using physical means alone. The wash water is treated and

recycled.

POEO Act Protection of the Environment and Operations Act 1997

Qenos Qenos Pty Limited. A chemical refiner located on BIP and providing ethylene to the

site for the manufacture of polyethylene plastic and ethylene oxide (a base chemical

used by Huntsman for the manufacture of surfactant products)

RAP Remediation Action Plan

RBC Risk Based Criteria

Restricted Solid Waste Material classified as Restricted Solid Waste in accordance with the DECC, NSW

(2009) Waste Guidelines

RTA Remediation Technology Assessment. Technology assessment completed by Orica

and reported in: Orica (2010a) Orica Botany, Botany Transformation Projects.

Remediation Technology Assessment for the Remediation of Mercury Contaminated

Soils

SCA Secondary Containment Area - The area defined in the NCUA as “the location where

the EPA approved contaminant containment works up gradient of Botany Bay and

Penrhyn Estuary, for the interception and containment of contaminant plumes that

have migrated or may migrate beyond the primary containment area, are carried out”.

SEPP 55 State Environmental Planning Policy No.55 – Remediation of Land

SEWR Significant Enough to Warrant Regulation. As assessment of contamination to

determine whether it is significant to warrant regulation under the CLM Act 1997.

SIA Specific Immobilisation Approval no. 2010-S-08 – Orica Australia Pty Limited Mercury

Impacted Waste – SITA Environmental Solutions, dated 11 August 2010

Site The land area to which the Management Order refers. This comprises the FCAP.

Site Audit Site auditors review the work of contaminated site consultants. The CLM Act calls

these reviews ‘site audits’ and defines a site audit as an independent review:

(a) that relates to investigation or remediation carried out (whether under the CLM Act

or otherwise) in respect of the actual or possible contamination of land, and

(b) that is conducted for the purpose of determining any one or more of the following

matters:

(i) the nature and extent of any contamination of the land

(ii) the nature and extent of the investigation or remediation

(iii) whether the land is suitable for any specified use or range of uses

(iv) what investigation or remediation remains necessary before land is suitable for any

specified use or range of uses

(v) the suitability and appropriateness of a plan of remediation, a long term

management plan, a voluntary investigation proposal or a remediation proposal


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The main products of a site audit are a ‘site audit statement’ and a ‘site audit report’.

Site Auditor An independent third party technical reviewer (for land contamination issues) who is

accredited by the EPA, NSW under the Contaminated Land Management Act 1997

Site Audit Statement A site audit statement is the written opinion by an accredited site auditor, on a EPA,

NSW approved form, of the essential findings of a site audit. There are two types of

Site Audit Statement (Section A or Section B) that can be prepared.

A Section A Site Audit Statement is used where site investigation and/or remediation

has been completed and a conclusion can be drawn regarding the suitability of the

land use(s)

A Section B Site Audit Statement is used when the audit is completed to determine the

nature and extent of contamination and/or the appropriateness of an investigation or

remediation action or management plan and/or whether the site can be made suitable

for a specified land use or uses subject to the successful implementation of a remedial

action or management plan

SPSS Sulfur Polymer Stabilisation/Solidification

t/d Tonnes per day

t/h Tonnes per hour

t/m3 Tonnes per cubic metre

TCLP US EPA toxicity characteristics leaching procedure.

TECE Temporary Emissions Control Enclosure. Temporary structure erected on Block G to

enclose active remediation excavations, soil treatment plant and materials stockpiles

to minimise mercury vapour emissions

US EPA United States Environmental Protection Agency

Validation Inspection and testing of remediation to ensure it meets the validation requirements of

the Remediation Action Plan

VMP Voluntary Management Proposal. A voluntary proposed action plan made to EPA,

NSW and approved under Section 17 of the CLM Act to formally regulate the mercury

remediation and/or management of significant contamination

Volatile Compound Chemical with sufficiently high vapour pressure to become a gas at room temperature

WARR Act Waste Avoidance and Resource Recovery Act 2001

Waste Guidelines DECC, NSW (2009) Waste Classification Guidelines: Part 1 Classifying Waste.

During April 2008 the DEC NSW Environmental Guidelines: Assessment,

Classification and Management of Liquid and Non-Liquid Wastes (2004) were

replaced by these guidelines. The 2008 Waste Guidelines were revised in 2009


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1.0 INTRODUCTION Golder Associates Pty Ltd (Golder) prepared this Remedial Options Appraisal Report (ROAR) on behalf of Orica Australia Pty Ltd (Orica) to assist Orica in addressing its obligations under the New South Wales Environment Protection Authority’s (NSW EPA) Final Management Order (#20111406) (the Order) for the Former ChlorAlkali Plant (FCAP) located at Botany Industrial Park (BIP), Matraville, NSW (the site).

2.0 BACKGROUND AND PREVIOUS ASSESSMENTS AND

REMEDIATION WORKS The FCAP area is located on land owned by Orica within the BIP at 16-20 Beauchamp Road, Matraville, NSW, which comprises part of Lot 11 in Deposited Plan (DP) 1039919 in the local government area of City of Botany Bay (CoBB) Council. The site is illustrated on Figure 1.

Orica used elemental mercury at their FCAP in an electrolytic process which operated from 1944 until 2002, after which it was replaced with a membrane cell electrolytic plant.

Environmental investigations completed between 2004 and 2008 identified significant concentrations of mercury in soil and groundwater at, and down gradient of, the FCAP.

In response to the findings of the soil and groundwater investigations, Orica committed to the NSW EPA and the Community Liaison Committee (CLC) to remediate the mercury soil contamination at the FCAP to the maximum extent practicable.

2.1 Human Health and Environmental Risk Assessment (HHERA) URS prepared a quantitative assessment (URS, 2008) of potential risks to human health and the environment associated with mercury contamination at and in the vicinity of the FCAP. More specifically, the HHERA considered:

Block G – Cell Block;

Block L – Chlorine Liquefaction and Chlorine Storage Area;

Block M – Hydrogen and Brine Treatment Area; and

Block A – Caustic Soda Filtration and Storage.

Assessment of Risks – Human Health

Assessment of possible risks to workers on FCAP identified potential exposure to elevated mercury concentrations and unacceptable risks to human health. The unacceptable risk was dominated by the inhalation of elemental mercury (Hg0) vapour pathway with a lower contribution from ingestion of inorganic mercury in soils.

Potential risks to human health in the down-gradient off-site areas associated with the presence of mercury in groundwater were considered to be acceptable. The assessment included consideration of exposures associated with beneficial use of the groundwater for industrial purposes, but noted such use was restricted by the declaration of a groundwater management zone by the (now) NSW Office of Water

Assessment of Risks - Environment

The HHERA noted that, based on data available at the time of preparation, mercury impacted groundwater had not discharged to any receiving environment, but also identified that mercury in soils and groundwater beneath FCAP provided an ongoing source to groundwater.



It recommended that mercury be included as an analyte in ongoing groundwater monitoring programs. It also recommended that any risk management measures at FCAP should include consideration of the mercury contamination (beneath FCAP) as a source to groundwater.

2.2 Determination of Contamination Significant Enough to Warrant Regulation

In July 2009 the NSW EPA determined1 the FCAP mercury contamination as Significant Enough to Warrant Regulation (SEWR) under the Contaminated Land Management (CLM) Act 1997.

Orica, in response to NSW EPA’s determination, acknowledged that mercury in soil at the FCAP represents a contaminant source that is likely to continue to impact groundwater quality and proposed to formalise its previous commitment to remediate mercury in soil through preparation of a Voluntary Management Proposal (VMP) under Section 17 of the CLM Act.

2.3 Contaminant Fate and Transport Modelling Fate and Transport modelling of the mercury in groundwater plume down gradient of the FCAP completed by A.D. Laase Hydrologic Consulting in 2010 (A.D. Lasse, 2010) indicated that:

Assuming the absence of a degradation mechanism, mercury would continue to migrate in groundwater away from the FCAP;

Noting the effect of salinity on mercury migration, migration rates would likely be variable along the plume flow path due to variations in salinity;

The model suggested that the mercury plume would pass beneath Springvale Drain (assuming continued operation of the existing Orica hydraulic containment pumping system) and would be captured by the Primary Containment Area (PCA) (Southlands) and Secondary Containment Area (Foreshore Road) extraction wells;

Without source removal, time for mercury in the groundwater plume to reach the containment extraction wells (PCA) was noted to be salinity dependent but was modelled at between 5 and 100 years; and

Assuming source removal, it was predicted that mercury in the groundwater plume would reach the containment extraction wells (PCA) at between 60 and more than 100 years.

2.4 Remediation Technology Assessment (RTA) Orica completed a mercury in soil remediation technology review to establish viable options with consideration of site-specific selection criteria. Orica’s review is presented in the following document:

Orica Botany, Botany Transformation Projects. Remediation Technology Assessment for the Remediation of Mercury Contaminated Soils dated 2010 and referred to as the Orica (2010) “RTA”.

The Orica (2010) RTA identified the remediation goal as being ‘....to remediate the contaminated Soils and Concrete, using commercial technologies with the lowest environmental impact, in order to maximise the potential reuse of Soils and Concrete on site and minimise disposal to landfill and, by so doing, make the land suitable for ongoing use as an industrial / commercial site’.

While the Orica (2010) RTA did not evaluate groundwater clean up or containment technologies it noted the remediation of soils and concrete would reduce the residual mercury concentrations in soils to a level below the risk based criterion calculated in the HHERA (URS, 2008) for the protection of groundwater.

A separate report entitled “A Review of Treatment Technologies for Mercury Contaminated Groundwater at Botany Industrial Park”, that was prepared by Workplace Risk Management Pty Ltd for Orica Australia Pty

1 Letter correspondence to Orica Australia Pty Ltd - Determination of Contamination Significant Enough to Warrant Regulation, 10 July 2009



Ltd, and dated March 2011” assessed various groundwater treatment technologies and concluded that “as long as the mercury contamination in groundwater at Botany continues to cause no unacceptable risk to human health and the environment, then MNA [Monitored Natural Attenuation] is the most sustainable and appropriate option.”

The RTA considered two main technology groups – Immobilisation Technologies and Recovery (Separation) Technologies. The following table provides a summary of the technologies considered under each of these headings and provides a short definition for each.

RTA - Summary of Immobilisation Technologies

Amalgamation Mercury is removed from soils by forming a semisolid alloy with another metal as a solid solution.

Stabilisation Chemical reaction to reduce the hazard potential of a contaminated material by converting the contaminants into less soluble, less volatile, less mobile, or less toxic forms.

Solidification Encapsulation of the contaminant, to form a solid material that physically immobilizes hazardous constituents but does not necessarily include a chemical reaction between the contaminants and the solidifying agents.

CFS (Chemical Fixation & Solidification

Combined use of stabilisation and solidification.

Vitrification High temperature process that immobilises contaminants by incorporating them into a vitrified matrix which is durable and leach resistant.

Containment Isolation of existing contaminated areas in the subsurface from the surrounding uncontaminated environment.

Entombment Immobilisation of contaminated material in an engineered landfill (monocell).

Encasement Immobilisation of contaminated material in an impermeable and engineered container.

RTA – Summary of Recovery (Separation) Technologies

Thermal High Temperature Incineration Heating materials in order to remove contaminants.

Thermal desorption (TD)

In situ TD In situ heating of contaminated soils causing direct volatilisation – removal of volatilised products through soil vapour extraction.

Ex situ TD Thermal Desorption (continuous ex situ)

Ex situ thermal desorption is a continuous process normally conducted in rotary kilns (or equivalent).

Retorting (batch) Ex situ batch process where contaminated soils are heated in a controlled manner – volatilising contaminants (e.g. mercury) which is then recovered from the off-gases.

Chemical Soil washing (Ex situ) Ex situ aqueous process that uses a leach solution to ‘solubilise’ contaminants (e.g. mercury) and remove it from the waste matrix for later treatment.

Electrochemical / electrokinetic recovery In situ process where an electric field is applied across a section of contaminated soil to facilitate the



RTA – Summary of Recovery (Separation) Technologies

migration of contaminants towards one of the electrodes for recovery.

Physical Physical soil washing Ex situ technique where soils are ‘washed’, generally with water. Wash water can then be treated and recycled.

Soil vapour extraction In situ process in which a vacuum is applied to the vadose zone to remove volatile (and some semi-volatile) compounds. Off-gas may be treated to recover or destroy contaminants.

Biological Bioremediation Application of certain plants or bacteria to assimilate or accumulate contaminants

Phytoremediation Use of plants to uptake/ remove, transfer, stabilize and destroy contaminants in soil and sediment.

The technologies summarised above were assessed by Orica against selection criteria using a scoring system which ranged between very negative (-2) and very positive (+2). Selected criteria were identified as ‘critical’, including:

Capacity of the technology to:

Be technically applicable to the project;

Meet the remediation criteria for material to be re-used on site as defined in HHERA;

Treat friable materials; and

Maximise the tonnage of materials reused on site and to minimise the tonnage sent to landfill (including consideration of the bulk-up factor).

The attributes of the technology are that it:

Is commercially demonstrated and available;

Has acceptable inherent process safeguards against potential hazards;

Has environmental issues (if any) that are manageable;

Has a likelihood of BIP acceptance; and

Has a likelihood of public acceptance.

As part of a preliminary screening assessment, technologies were rejected where a ‘-2’ score was assigned against any of the critical criteria. The majority of the technologies were rejected on this basis.

Only two technologies – immobilization (monocell entombment) and recovery (physical soil washing) – passed the preliminary screening assessment. These two technologies were then assessed against all criteria and further reviewed. The key issues from the detailed review were:



Soil washing would result in a significant amount of soil which could be reused on site but would also produce materials in which high levels of mercury are concentrated that require disposal;

Soil washing had a limited ability to treat concrete; and

Entombment in a monocell would meet the site-specific remediation criteria but would require a significant volume of landfill space and pose potential risks during removal and transport.

On this basis it was decided that the preferred technology would be a combination of the two options with the hope that advantages can be reinforced and disadvantages could potentially cancel out.

2.5 Remediation Action Plan, 2011 A remediation approach was developed in parallel with the Orica (2010) RTA and documented in a Remediation Action Plan (RAP) prepared by URS (URS, 2011).

The RAP covered the remediation of mercury contaminated soil (and concrete) at two discrete locations (Blocks G and M) within the foot print of the FCAP. It also captured the proposed relocation of the salt (sodium chloride) stockpile, used by the current Orica ChlorAlkali Plant (CAP) facility, to address its potential impact on groundwater quality.

The URS (2011) RAP presents the preferred treatment technology for the mercury contaminated soils as excavation and on-site physical soil washing, for on-site reuse, combined with entombment of selected wastes to an off-site engineered and licensed monocell.

2.5.1 Remediation Objectives The objectives for the remediation of soil and groundwater in the vicinity of FCAP (Blocks G and M) were stated in the RAP as:

Substantial mercury source removal – the reduction of mercury source areas identified as contributing to soil and groundwater contamination;

Salinity source removal – relocation of a salt stockpile, used by the current CAP facility, to address potential impacts to groundwater;

Minimisation of soil vapours – the substantial removal of soil/ fill materials contaminated with mercury that could potentially be an ongoing source of mercury vapours to air; and

Rendering the site suitable for reuse (protective of human health) – for the proposed industrial land use exposure scenarios.

2.6 RAP Implementation Program On 1 June 2011, the NSW EPA approved a VMP (Notice No. 20111711) under the CLM Act 1997 for the management of mercury at the site. The VMP included implementation of the RAP which commenced at the site in 2011. The excavation and soil washing components were undertaken within a purpose built Temporary Emission Control Enclosure (TECE) equipped with two Emission Control Systems (ECSs) to treat mercury vapours in air extracted from the enclosure prior to discharge to atmosphere.

Although the soil washing treatment process successfully removed some mercury from soils beneath Block G, the process proved inefficient and during August 2011 it was determined by Orica that the treatment process being implemented at Block G was not sufficiently addressing the remediation objectives set out in the VMP.

On 19 August 2011 Orica announced its intention to the NSW EPA to suspend the mercury remediation work on the understanding that it would be re-evaluating remediation options to meet the objectives of the VMP.

Following the decision to discontinue the soil washing component of the remediation program, Orica undertook a process of consultation with stakeholders including the NSW EPA, the Orica appointed NSW



EPA Accredited Site Auditor for the site (Chris Jewell) and the wider community. In parallel with this process, Orica also investigated the viability of another RTA remedial option which was based on a ‘capping and containment’ approach involving the construction of a cement-bentonite cut-off wall around the perimeter of Block G.

In December 2011 Golder prepared (on Orica’s behalf) a position paper (Golder, 2011), which summarised the outcomes of the regulatory and community consultation process to date and documented a proposed revision to the remediation strategy. It was noted that given soil washing had proven unsuccessful for the conditions at FCAP, the remaining viable option from the RTA was off-site entombment (monocelling). The paper provided an outline strategy for such an approach and foreshadowed preparation of a revised RAP following stakeholder input/concurrence.

2.7 RTA Revision A revision to the RTA issued by Orica in December 2011 (Orica, 2011) reviewed the available remediation technologies in light of experience gained from the inability to meet the remediation objectives of the VMP in a timely manner using the soil washing technology in full scale operation.

The revised RTA concluded that off-site entombment or entombment in situ were the preferred available technologies.



3.0 NSW EPA MANAGEMENT ORDER, JANUARY 2012 On 9 January 2012 the NSW EPA issued a Management Order (Order Number 20111406; Declaration Number 21074; Area Number 3203) to Orica under Section 14 of the CLM Act 1997. The EPA concurrently withdrew its approval of the VMP.

3.1 Remedial Options Appraisal Under the first of ten actions identified in the Management Order, Orica was directed to prepare a detailed written remedial options appraisal report (this ROAR). The Management Order stated that the report must:

a) Specify and describe options to remove to the maximum extent practicable the risk to human health and environment from mercury at the Land and prevent ongoing contamination of the groundwater by the end of 2014.

b) Assess each of the following remedial options, including any possible combinations of those options;

i) In situ thermal technologies

ii) Ex situ thermal technologies

iii) on-site containment

iv) off-site disposal, including consideration of the requirements for stabilisation of the contamination prior to transportation off site.

c) Compare the technologies available for the management of the contamination in terms of:

i) the effectiveness in cleaning up the contamination;

ii) long term sustainability;

iii) protection of the environment;

iv) the cost of the technology in the short and long-term, including sufficient details to enable a review and independent verification of any such cost comparison.

It is also noted that the Management Order required Orica to ‘engage an independent expert, approved by the EPA, experienced in the remediation of mercury contaminated soils and submit a copy of the remedial options appraisal report to that person for peer review’. Orica provided the appointed expert, Mr. Kendrick Jaglal of AECOM Technical Services Northeast, Inc., with a draft copy of the ROAR dated 28 February 2011. Subsequent input and discussions with the appointed expert have been incorporated herein, as directed in the Management Order.

3.2 Management Order Intent In directing Orica to prepare this ROAR the NSW EPA requires the appraisal of the four remediation options presented in direction (b) of the Management Order within the assessment framework outlined in direction (c).

It is Orica’s and Golder’s understanding, through clarification discussions with the NSW EPA2, that the overall intent of the Management Order is to facilitate identification of the most viable remediation option to address the ‘source’ contamination beneath FCAP and to complete remediation in a timely manner. This identified option should achieve the short term objective of rendering the FCAP land suitable for continuing industrial/commercial land use, whilst also providing longer term improvement to the down gradient groundwater quality and general environment.

2 James Stening (Orica) and Niall Johnston (NSW EPA) telephone discussion dated 15 February 2012



Risk Based Criteria The quantitative remediation objectives for the FCAP were derived in the HHERA (URS, 2008), and also presented in the RAP (URS, 2010). It was noted (URS, 2010) that these risk-based criteria (RBC) were dominated by the potential for elemental mercury vapour migration and intrusion.

Two RBC were derived ‘for the protection of long term off-site workers’ and included:

RBC for total mercury in soil assuming buildings for human occupation are permitted on the site of the FCAP = 90 mg/kg;

This RBC envisaged redevelopment of the FCAP to include construction of a new occupied building. It was assumed that such a building would be constructed as slab on grade with no basement, consistent with other industrial buildings on the BIP; and

RBC for total mercury in soil assuming no buildings for occupation are constructed on the site of the FCAP = 200 mg/kg;

Assumes an open area with no buildings or other significant ground cover.

Another mercury RBC for soils (455 mg/kg) was derived to be protective of downgradient groundwater and was based on a target concentration in groundwater derived to be protective of beneficial use (industrial use). It was also associated with a leachable concentration of 13 mg/L of mercury. This RBC was not used as a target value when implementing the RAP.

3.3 Land to Which the Order Applies A site plan attached to Part 2 of the Management Order is understood to identify the Land to which the Management Order applies. The Land includes the areas of the FCAP known as Blocks A, G, L and M. A site plan is presented in Figure 1.

The land to which the Management Order applies is owned by Orica3. Orica representatives have indicated they currently have no intention or plans to divest the property in the foreseeable future. Golder understands that the existing CAP is expected to remain operating for many years to come, as is the Groundwater Treatment Plant (GTP) that Orica also owns and operates elsewhere on BIP. Furthermore, there is a range of other land contamination issues on BIP that Orica is committed to managing, which will take substantial time to remedy.

4.0 SITE SETTING AND FEATURES As stated under Australian and New Zealand Environment and Conservation Council (ANZECC) & National Health and Medical Research Council (NHMRC) (1992), the appropriateness of a particular remediation option is likely to depend on a range of local factors and site-specific constraints.

4.1 Surrounding Infrastructure The FCAP is located at the southern end of BIP and is surrounded by chemical manufacturing operations or chemical storage facilities, with the exception of Blocks A and L, which are bounded to the south west by a goods railway shunting yard.

More specifically the operational FCAP is located to the west, the Huntsman Surfactant Plant to the north and east and Quenos operations (Site Utilities, Olefines, Alkathene and Alkatuff are located further north. The Orica Groundwater Treatment Plant (GTP) is also located to the north.

Residential areas are located on the eastern side of nearby Denison Street, which runs down the eastern side of BIP. The site location, surrounding features and approximate locations of the four Blocks (A, G, L and M) are shown on Figure 1.

3 A portion of Block M, inferred to be not impacted by mercury, is owned by Huntsman Corporation Australia Pty Ltd



Site specific constraints associated with the surrounding infrastructure and community include:

Occupational health and safety considerations associated with undertaking remediation works adjacent to operational chemical manufacturing plants;

Local sensitive receptors, in particular Denison Street residents and the associated requirements for minimising noise, air and traffic impacts; and

Requirements not to impact on adjoining CAP operations. For example, access to the salt stockpile located adjacent (to the north-east of) Block G, is to be maintained.

4.2 FCAP Features 4.2.1 Block G Block G was decommissioned and demolished to concrete slab level between 2004 and 2007.

A Temporary Emissions Control Enclosure (TECE) was constructed on Block G to house excavations and soil washing processes in 2011. The TECE is equipped with two Emission Control Systems (ECS).

While a portion of the concrete slab was removed during the soil washing remediation program, a significant portion of concrete slab and footings are understood to remain across Block G. The concrete slab and its steel reinforcement bars were generally noted during the works to contain prills of elemental mercury attached to the surfaces. It is also understood that the thickness of the slab and its footings are variable and can be quite thick (>1m), for example beneath former infrastructure. Remediation of the concrete remains a major consideration in assessing suitable remediation approaches for FCAP Block G.

4.2.2 Blocks M, L and A Operational CAP infrastructure is located across Block M of the FCAP and includes the adjoining sulphuric acid storage, a product loading area, a cooling tower and hazardous goods and mercury storage. Access is required to the salt stockpile located to the north-east of Block G.

Block L houses storage and operational facilities and Block A contains several operational above ground storage tanks as well as the garden area fronting the control building for the current CAP.

4.3 Summary of Extent of Soil Contamination A précis of the extent of mercury impacts in soil at the FCAP provided in the RAP (URS, 2010) and augmented based on more recent investigations by Golder is presented below. Figure 2 and 3 present the extent of contamination considered in the RAP.

4.3.1 Block G Mercury concentrations exceeding the RBCs for continued industrial and open space uses (refer Section 3.2) were identified across Block G, but in particular beneath the former cell rooms within soil and fill materials, concrete slabs and footings. The depth of mercury impacts was reported to be relatively shallow, generally less than 1.5 m below existing ground surface level (BGSL).

More recent investigations by Golder assessed the depth of mercury contamination beneath two identified ‘hot spots’ of localised mercury contamination in soils beneath Block G that were identified during excavation for the soil washing exercise. The results indicated that in these ‘hot spot’ areas moderately elevated concentrations of total mercury in soils (>200 mg/kg) are located to a maximum depth of approximately 3 to 5 m BGSL, but that mercury concentrations exceeding 90 mg/kg (but less than 200 mg/kg) are present at greater depths (to approximately 18 m bgsl).

Given the nature of the contaminant and its potential for vertical (and lateral to a lesser extent) migration, particularly along preferential pathways presented by concrete footings and other former structural features, the precise extent of deeper mercury impacts to soil within Block G.



Visible elemental mercury was also identified in brick footings, concrete slabs and underlying soil and fill associated with the former cell rooms and related infrastructure beneath the cell blocks.

4.3.2 Block M Concentrations of mercury exceeding RBCs were recorded in shallow (generally less than 1.5 m BGSL) soil and fill materials at several locations across Block M. However, the vertical extent of mercury impacts to soil within the affected area in Block M has not been fully defined.

Elemental mercury was also identified beneath the area formerly occupied by the mercury retort and in the vicinity of the hydrogen compressors (in very shallow fill).

4.3.3 Block L One of the investigations identified shallow soil contamination at one location beneath a raised concrete platform.

No elemental mercury was reported in the Block.

4.3.4 Block A An elevated mercury concentration (>1,000 mg/kg) was detected in a shallow soil sample collected from a garden area adjacent to the control room of the current CAP.

Based on the concentration detected it was considered likely that elevated concentrations of total mercury could also be present within other, inaccessible areas of Block A.

4.4 Groundwater The HHERA noted that, based on data available at the time of preparation, mercury impacted groundwater had not discharged to any receiving environment, but also identified that mercury in soils and groundwater beneath FCAP provided an ongoing source to groundwater. In relation to mercury in groundwater at and downgradient of the site, it is noted that:

Given the site history, it is probable the mercury contamination dates back to early operation of the plant (possibly as early as the 1940s). Furthermore, the mercury plumes in the downgradient groundwater have been monitored for some time but have not travelled appreciable distances during the temporal extent of the monitoring program;

The concentration gradients are relatively steep, supporting the lack of travel across appreciable distances;

Modelling has indicated, that without source removal, an approximate timeframe in the order of 5 to 100 years before the plumes reach the existing Orica groundwater extraction wells in the Primary Containment Area (PCA) and Secondary Containment Area (SCA);

Orica have proposed relocation of a salt (sodium chloride) stockpile, used by the current Orica Chlorakali Plant (CAP) facility, to address its potential impact to groundwater.

There have been no indications of surface water impacts.



5.0 REMEDIAL OPTIONS APPRAISAL APPROACH A primary review of available remediation technologies was conducted by Orica as described in Section 2.4. This section of the ROAR presents a review of the four potential remediation options for the site identified in the Management Order. The review includes an appraisal of the practicability of each of these options in addressing the remediation objectives with consideration of the following:

technical feasibility based upon site specific hydrogeological conditions, the nature and distribution of the mercury contamination present and site constraints. This also includes the ability to implement institutional controls. It is noted that these factors were not included in the list of considerations set out in the Management Order, but are nevertheless essential in assessing the relative merits of the remedial options being appraised;

effectiveness in achieving the remediation objectives

sustainability;

protection of the environment; and

relative cost.

Stakeholder acceptance, in particular community consultation, is not assessed for each remediation option, but is discussed in general terms in Section 9.2.8.

NSW EPA’s preferred position on the selection of remediation options, as stated in the NSW EPA (then NSW DEC (2006)) Auditor Guidelines, is based on the policy of the then ANZECC and NHMRC on the remediation of contaminated sites as published in the Australian and New Zealand Guidelines for the Assessment and Management of Contaminated Sites (ANZECC & NHMRC, 1992). ANZECC & NHMRC (1992) specify the preferred order of options for site soil remediation and management to be as follows:

On-site treatment of the soil so that the level of contaminant is either destroyed or the associated hazard is reduced to an acceptable level; and

Off-site treatment of excavated soil, which, depending on the residual levels of contamination in the treated material is then returned to the site, removed to an approved waste disposal site or facility or used as fill for landfill.

Should it not be possible for either of these options to be implemented, ANZECC & NHMRC (1992) specify other options that should be considered as including:

Removal of contaminated soil to an approved site or facility, followed where necessary by replacement with clean fill (if needed);

Isolation of the soil by covering with a properly designed barrier;

Choosing less sensitive land use to minimise the need for remedial works which may include partial remediation; and

Leaving contaminated material in situ providing there is no immediate danger to the environment or community and the site has appropriate controls in place.

If remediation is likely to cause a greater adverse effect than leaving the site undisturbed, remediation should not proceed.

ANZECC & NHMRC (1992) also emphasise that:

The appropriateness of any particular option will vary depending on a range of local factors; and



Acceptance of a specific option or mix of options in any particular set of circumstances is a matter for the responsible authority.

Each of the remediation technologies is assessed in the following sections against the required criteria listed above and described below. It is noted that three technologies, off-site disposal, off-site disposal with stabilisation and ex situ thermal treatment, are presented and evaluated as alternatives for material management following excavation (i.e. Source Removal). Regardless of the material management alternative selected, the impact of removal on the site would still be the same.

5.1 Technical Feasibility Technical feasibility includes the ability and timeframe to implement and maintain the remediation option, and the availability of equipment and technical expertise. This is largely based on technology status, case studies, implementability at the FCAP and site constraints.

Institutional implementability includes the ability and effort required to obtain approvals from regulatory agencies (e.g. planning and environmental). Although the regulatory and planning requirements for each of the remediation options have not been ascertained at this stage, given the regulation under the Order, it is likely that all remediation options will necessitate similar institutional processes, although the level of effort required may vary. Nevertheless, ongoing management of residual mercury at the FCAP will be required for all remediation options considered. Institutional implementability is discussed in general terms in Section 9.2.7.

5.2 Effectiveness Evaluation of the effectiveness of the remediation options includes assessment of the remediation option to meet the remediation objective, that is, to mitigate to the extent practicable potential risks to human health (for on-site workers and local residents) and the potential environment (particularly with regard to groundwater and atmospheric emissions) from mercury at the FCAP and prevent ongoing contamination of the groundwater by the end of 2014. In relation to NSW EPA Auditor Guidelines and ANZECC and NHMRC Guidelines for the Assessment and Management of Contaminated Sites, it is noted that in relation to remediation of mercury:

Mercury cannot be destroyed. The remediation options either transfer the mercury from the site to a more manageable form or location, or leave the mercury at the site but control exposure pathways thereby mitigating risks to human health and the environment.

It is likely that residual mercury will remain at the FCAP with all remediation options, which will require ongoing management in order to ensure there are no unacceptable risks to receptors in the long term.

5.3 Sustainability A remediation option that is technically feasible and effective (i.e. has a site benefit) may have detrimental effects on the wider environment or society.

An objective of the preferred remediation option should be a net benefit to the environment and community via achieving a balance between environmental, social and economic factors. This includes consideration of:

waste generation

impacts on other segments of the environment;

energy consumption;

resource consumption;

greenhouse gas emissions; and

other stressors to the local ecology and/or community.



In the appraisal of options, green house gas emissions are calculated based on the following general assumptions (DCCEE, 2010):

Greenhouse gases considered are carbon dioxide (CO2) methane (CH4) and nitrous oxide (N2O).

A ‘global warming potential factor’ of 1, 21 and 310 for CO2, CH4 and N2O, respectively, in order to determine the CO2 ‘equivalent’ (CO2-e)

An emission factor of 2.7 kg CO2, 0.01 kg CH4 and 0.02 kg N2O per litre diesel fuel. This equates to approximately an emission factor of 8.9 kg CO2-e per litre diesel fuel.

An emission factor of 1000 kg CO2-e per megawatt-hour electricity4.

In particular, the remediation option should, to the extent practicable, minimise the requirement for off-site waste disposal. In NSW achieving a reduction in waste generation and turning waste into recoverable resources is a priority for NSW EPA. Waste avoidance and resource recovery is promoted under the Waste Avoidance and Resource Recovery (WARR) Act 2001. A remediation option with a low energy requirement is also preferable.

In summary, an objective of the preferred remediation option should be a net benefit to the environment and society. This should include consideration of impacts on other segments of the environment including energy consumption and the objectives of minimising carbon emissions and conserving fossil fuels.

Stakeholder acceptance, in particular community consultation, is discussed in general terms in Section 9.2.8

5.4 Protection of the Environment Protection of the environment considerations include assessment of environmental risks that the remediation option presents either during implementation (short term) or after the active remediation has been completed (long term).

Environmental benefits (which represent one of the remediation objectives) are assessed as part of effectiveness as discussed in Section 5.2.

As discussed in Section 2.1, the HHERA (URS, 2008) identified that there were no unacceptable risks to human health or the environment associated with mercury in groundwater downgradient of the site, but mercury in soils and groundwater beneath FCAP provided a seemingly ongoing source to groundwater. As discussed in Section 2.3, fate and transport modelling (Laase, 2010) indicates that mercury impacted groundwater will be intercepted by PCA and SCA containment lines within 5 to 100 years (depending on attenuation rates). Remediation solutions which control mercury sources at the FCAP will likely result in more rapid mitigation of mercury concentrations in the plume (estimated to be within 60 to 100 years) than with no source control.

5.5 Cost The objective of the cost evaluation is to eliminate from consideration those remediation options with costs that are grossly excessive for the net benefit they provide. Considering that this document contemplates a series of conceptual approaches to remediation, the associated capital and operation and maintenance (O&M) costs are relative order of magnitude costs. Should the conceptual approaches become more detailed and preliminary designs begin to take shape, the costs can be refined further. However, since the relevant assumptions, unit costs and general approach for all the alternatives are similar in this document, these costs are adequate to facilitate a relative comparison between the alternatives. Assessment of relative costs for each of the remediation options is presented in Appendix A.

4 A value used by Origin Energy



6.0 SOURCE REMOVAL Source removal involves excavation of mercury impacted materials and, since mercury cannot be destroyed or degraded, management of the excavated materials in a manner that is protective of human health and the environment. Sections 6.1 and 6.2 assess the source removal remediation option, while latter sections assess management options for removed mercury source, including the following:

Off-site disposal (Section 6.3)

Off-site disposal with stabilisation (Section 6.4)

Ex situ thermal treatment (Section 6.5)

6.1 Technology Description The specifics of a viable remediation strategy and methodology for the excavation and materials handling of mercury impacted concrete and soil at FCAP (Block G) have been detailed as part of the previous remediation program in the RAP (URS, 2010).

6.1.1 Remediation Action Plan (URS, 2010) The source removal strategy described in the RAP was aimed at removing identified mercury and chloride source areas, thereby removing potential ongoing contamination sources groundwater.

Accordingly, the remediation goal was to render the FCAP suitable for the proposed ongoing industrial land use whilst both:

Ensuring the residual vadose zone soils would no longer be considered a source of significant groundwater contamination or a risk to on-site human health via inhalation (vapour) or contact/ingestion (dust) pathways; and

Reducing the potential for ongoing mobilisation of mercury sources through removal of a substantial chloride source.

The strategy detailed in the RAP focussed on Blocks G and M of the FCAP. While another area of contamination (Block A) was indentified, it was considered that extent of contamination and corresponding concentrations were negligible in comparison with the potential contribution from Blocks G and M (URS, 2010). In addition, several operational constraints made the impacted portion of Area A inaccessible.

The proposed lateral extent of remediation included the entire footprint of Block G and a portion of the footprint of Block M, and focussed on the removal from these areas of soil and fill materials onto which free elemental mercury and other forms of mercury were adsorbed. Surface and near surface contaminated concrete slabs were also included as they contained significant amounts of elemental mercury trapped in pores, cracks and historically repaired areas. The lateral remedial extents are presented in Figure 2.

The proposed vertical extent was identified as a maximum target depth of 1.5 m below existing (pre-remediation) ground surface level (bgsl) based on available information.

6.1.2 Extent of Remediation The source removal approach considered in this ROAR, is largely similar in terms of the extent described in the RAP (URS, 2010). However, removal of relatively minor volumes of impacted materials located in the affected area at Block M and the accessible portion of Block A have also been considered.

While mercury impacts have been identified in largely shallow soils (less than 1.5 m bgsl), given the nature of the contaminant and its potential for vertical migration, in particular along preferential pathways presented by concrete footings and other former structural features, it is considered deeper (>1.5 m bgsl) excavation to extent of contamination or extent practicable would be warranted in some areas (‘hot spots’) within Block G, or at least that provision should be made for such requirements in any remediation estimations.



The extent of remediation would likely encompass a general target depth of 1.5 m bgsl across the area of Block G (approximately 100 m by 100 m), but would also include provision for deeper excavation at localised ‘hot spots’ to the extent practicable, based on the concentrations of total mercury in soils (>200 mg/kg) which were recorded between approximate depths of 3 to 5 m bgsl in recent investigations by Golder5. Mercury concentrations exceeding 90 mg/kg (but less than 200 mg/kg) are present at depths to approximately 18 m bgsl, which are likely to be impracticable to excavate. Removal of shallow soils to the extent practicable in the impacted area at Block M and the accessible portion of Block A should also be considered.

On this basis it is likely that an in situ volume of approximately 20,000 m3 should be considered for the purposes of considering remediation extent for source removal.

6.2 Option Review 6.2.1 Technical Feasibility As described in Section 2.6 and above, limited excavation of mercury impacted soils and concrete have been undertaken successfully within the TECE as part of the soil washing remediation program. It is being assumed that further excavation of impacted materials at the FCAP would be conducted in a similar manner.

Implementation

Excavation at Block G would be performed in the existing TECE in order to contain potential fugitive dust and mercury vapour emissions. The TECE is equipped with two Emission Control Systems (ECS), which treat the indoor air and thereby mitigate potential external human health and environmental risks during remediation. If impacted materials from outside the footprint of Block G are to be excavated (e.g. at Block M), a temporary enclosure could also be required.

Experience gained during the soil washing remediation program has provided several insights into the practicability and challenges of excavation in a temporary enclosure.

Experience has indicated that the operating capacity of the ECSs, in processing mercury impacted vapours generated during excavation, is a significant limiting factor in the overall excavation rate. At a minimum, it is likely that staging of the excavation work would be required to moderate emission rates from excavations and stockpiles so as to minimise the potential for overloading the ECSs and to maintain an occupationally safe working environment. In the event that overloading occurs, work stoppages and delays eventuate while waiting for vapour levels to return to satisfactory concentrations.

Accordingly, the environmental management section (Section 12) of the RAP stipulates several controls and measures that are required to minimise the generation of dusts and mercury vapour emissions during the works. Even so, up to 2000 µg/m3 of mercury vapour was observed during the soil washing programme, which is 80 times the occupational TLV of 25 µg/m3.

Disturbance of mercury-containing soil can create a very adverse atmosphere within the TECE. As such all works within the TECE are required to be undertaken in full PPE, including Tyvek suits and air purifying breathing apparatus. During the hotter summer months, the progress of the overall program is further limited by difficulties associated with working in extreme heat and the associated requirements for scheduling frequent recovery breaks. During the frequently needed breaks personnel have to fully exit the TECE and complete full decontamination protocols each time. Under such conditions efficiency is effectively around 60% of that during normal conditions, given that each two hour shift inside the TECE requires full decontamination procedure and rest periods, which together take at least one hour.

Using equipment (mobile or stationary) with internal combustion engines inside the TECE generates potentially harmful combustion gases including carbon dioxide, carbon monoxide and oxides of nitrogen. These gases are not removed by the filters used in the air purifying breathing apparatus. Therefore controls such as limiting the use of mobile equipment and piping exhaust of fixed plant

5 The results of these investigations have been consulted in preparation of this report but have not yet been published.



outside the TECE must be employed to ensure safe working conditions inside the TECE. Otherwise supplied air respirators, which will further impede worker efficiency, must be employed.

In the case of preparing materials for off-site disposal, (or for transport to another part of BIP for treatment (as may be required with ESTD, for example) all excavated materials need to be placed into lined and sealed containers (skips) for dispatch. Once prepared, the skips would be transferred into and loaded inside an air-sealed loading bay of the TECE, which is of limited capacity. Orica has indicated that only up to four skips could be processed at any one time, which places further constraints on the rate of throughput.

The nominal height of the roof of the TECE is 8 m, which limits the height of equipment (such as pile drivers) that may be used inside the TECE. The inability to use pile drivers inside the TECE eliminates options for shoring up deeper excavations.

Based on experience with the soil washing remediation program, it is likely that excavation would take a period of up to 6 months.

Constraints

Assuming excavation would continue within the existing TECE, it is noteworthy that various structural elements of that enclosure have to date limited the practical lateral extent of excavations.

The current site surface contains significant concrete slabs, footings and demolition waste. These must be removed (and treated or disposed) prior to excavation of soil.

Observations during remediation works performed to date at FCAP have shown that a significant mass of elemental mercury (prills) attached to contaminated materials, or located in the immediate vicinity of concrete slabs, drains and footings. Demolition and pre-processing (e.g. crushing to a uniform and manageable size) of concrete rubble and debris would be required prior to excavation of the soil and fill lying beneath.

While it is envisaged that some source reduction could be achieved through excavation at FCAP, given the pervasive nature of mercury and its behaviour in the subsurface, it is unlikely the full lateral and vertical extents of the mercury can be accessed. Furthermore, difficulties in effectively excavating mercury impacted materials were experienced during the remediation excavation works undertaken at the Block G during the 2011 soil washing remediation works. The distribution of free phase mercury was observed in several locations to have been influenced by subsurface structures, principally comprising brick and concrete foundations and drains. The edges of residual in-ground structures appeared to have provided preferential pathways for migration of elemental mercury to greater depths in the subsurface. Disturbance/ removal of the residual foundations would appear to present a risk of mercury mobilisation along these pathways. Accordingly, there is an inherent limitation in the overall effectiveness of any technology involving excavation, whether followed by disposal or ex situ treatment.

Since it is likely to be impracticable to excavate all impacted soil and there is uncertainty in vertical distribution of mercury due to the nature of the contaminant and its potential for vertical (and lateral to a lesser extent) migration, it is likely that longterm management of residual mercury contamination will be required following completion of any excavation and removal of impacted soils to the extent practicable. Given the constraints imposed by the structure of the TECE and localised deep penetration of mercury along preferred flow pathways, as discussed above, mean that validation of the removal of mercury impacted soils could not likely be achieved in all the excavated areas.

In summary, while completed works have demonstrated that excavation to the variable target depth within the TECE is achievable, there are several logistical factors that will result in relatively slow progress in safely completing the works and that will require careful planning and oversight to achieve and document. In addition, excavation will not reach the extremities of the impacted area in Block G and there are several practical limitations in this regard. While these issues would not prevent this remedial approach, they require careful consideration in assessing the relative merits of available approaches.



6.2.2 Effectiveness Removal of mercury from shallow soils at FCAP will likely provide some degree of long-term protection to human health and benefits to the environment. The potential benefits of excavation of mercury impacted concrete and soils at the site include:

Human health:

Reduction in unacceptable risks to site workers by prevention of direct contact with impacted soils and inhalation of impacted dust from the removed materials.

Reduction in unacceptable risks to site workers by prevention of mercury vapour emissions (assuming vapours from residual mercury below depth of excavation do not represent an unacceptable risk) from the removed materials.

Environmental:

Excavation and off-site disposal of mercury impacted shallow soils and concrete would result in removal of a substantial portion of mercury from the excavated area, significantly reducing (but perhaps not entirely eliminating) the ‘legacy’ issues associated with the mercury contamination beneath the FCAP.

Since mercury is removed from shallow soils (but unlikely all the way to the water table at approximately 5 m bgsl) any rainwater infiltration into the subsurface (although the overlying surface is targeted for paving as part of salt pile relocation) will be reduced as a mechanism for mercury impacts to groundwater in the treated area, thereby reducing impacts to downgradient groundwater.

The HHERA (URS, 2008) concluded that there were no unacceptable risks to the environment associated with mercury in groundwater downgradient of the site. However, with source control, restoration of mercury impacted groundwater downgradient of the site has been predicted to occur at the PCA and SCA more rapidly (within 60 to 100 years) than with no source control. Since excavation results in mercury removal from shallow soils, (but unlikely all the way to the water table at approximately 5 m bgsl), any rainfall infiltration into the subsurface will be reduced as a mechanism for mercury impacts to groundwater in the remediated area, thereby reducing impacts to downgradient groundwater and decreasing the time for aquifer restoration.

These benefits would also be achieved with the capping of the area when the salt slab is relocated (see Section 2.5).

The potential limitations in effectiveness of excavation of mercury impacted concrete and soils at the site include:

The potential for direct exposure of workers to mercury vapours and direct contact or inhalation of soil/dust is substantially increased during remediation. Although this can be mitigated by performing excavation works within the TECE and successful implementation of appropriate occupational health and safety controls.

The potential for direct exposure of local residents to mercury vapours and dust during remediation. This can be mitigated by performing the excavation works within the TECE and limiting the scale of the operations to ensure that the capacity/capability of the ECSs is not exceeded.

Since only shallow soils are practicable to excavate and manage, residual mercury currently present below anticipated excavation depths and in the saturated zone would not be addressed, which may still represent a potential subchronic risk to intrusive maintenance workers.

The potential to mobilise elemental mercury – especially downwards – by disturbing the source areas. It would not be possible to limit downward migration other than to rely on naturally-occurring low



permeability layers such as peat layers and the underlying clay and sandstone bedrock, although at these layers lateral migration may then occur.

Mercury present in shallow soils outside the area of treatment and deeper soils, and associated risks to human health and the environment, will not be addressed.

Although reduction in infiltration will reduce ongoing impacts to shallow groundwater, it is noted that dissolution of elemental or previously sorbed inorganic mercury will still occur as groundwater passes through soils beneath the source area.

6.2.3 Sustainability As discussed in Section 5.3, an objective of the preferred remediation option is to attain a net benefit to the environment and community by achieving a balance between environmental, social and economic factors. This should include consideration of impacts on other segments of the environment, energy consumption, consumption of other resources, greenhouse gas emissions and other stressors to the ecology and/or community.

The main considerations in terms of energy and fuel consumption include:

Operation and maintenance of the TECE and its ECSs; and

Operation of any mobile plant within the TECE for the duration of the excavation programme.

The spent filters from the ECS require transport to and disposal at an off-site facility, most likely to monocell. Water generated during decontamination and PPE and associated waste would also need to be disposed. On-site treatment of concrete slabs and foundations might not be practicable, so these might also require transport to and disposal at an off-site facility, most likely to monocell

On the basis that operation of three mobile pieces of heavy equipment would be required for excavation, stockpiling and loading impacted materials at the FCAP, and assuming a fuel usage of 100 litres of diesel per day per plant, the total fuel consumed over the course of the program would be in the order of 50,000 litres.

The “carbon footprint” of off-site disposal is in the order of 450 tonnes of CO2-e based on the assumption that processes considered were limited to fuel consumption for excavation and loading of impacted materials at the FCAP.

6.2.4 Protection of the Environment The various scenarios of excavation of mercury sources at the site include the following environmental considerations:

Risk of fugitive mercury vapour emissions and dust generation during excavation and handling of materials. This can be mitigated by utilising the TECE building currently constructed over Block G. However, with air concentrations up to 2000 µg/m3 within the TECE any accidental breach could pose a substantial threat to nearby residents and others in the area; and

Following completion of an aggressive removal program, residual mercury and mercury outside the area of treatment (including that which might be mobilised outside the treatment area by the excavation works) will still persist. This residual mercury would contribute to potential risks to human health and the environment and will therefore still require ongoing management, most likely in the form of a management plan and ongoing monitoring.

6.2.5 Cost Assessment of relative costs of source removal is included with the relative costs for the different management options presented in Appendix A.



6.3 Off-Site Disposal 6.3.1 Technology Description The excavated materials would be transported from the site to an off-site waste facility licensed to receive mercury impacted wastes for disposal. A review of former Chlor-alkali plant sites in North America indicates that although removal of mercury impacted soils or sediments (via excavation or dredging) is commonly conducted, the main remediation remedy most often involves on-site containment, including capping and/or consolidation and on-site disposal of impacted materials in an engineered landfill, including at the following sites:

Alcoa/Lavaca Bay Superfund Site, Texas, USA

Holtra Chem Superfund Site, North Carolina, USA

LCP Chemicals Superfund Site, Georgia, USA

Berlin Former Chlor-Alkali Facility Superfund Site, New Hampshire, USA

Georgia-Pacific West Corporation Chlor-Alkali Plant, Washington, USA

Occidental Chemical Corporation Chlor-alkali Plant, Delaware, USA

Olin McIntosh Superfund Site, Alabama, USA

Weyerhaeuser Longview Chlor-alkali Plant, Washington, USA

Hanlin-Allied-Olin Superfund Site, West Virginia, USA

Olin Saltville Waste Disposal Ponds Superfund Site, Virginia, USA

It is noted that the extent of remediation at these sites was generally relatively large scale (e.g. of the order of 10,000 to 100,000 m3 of impacted materials and/or exceeding several hectares of impacted land) and was conducted in multiple stages over long time periods with multiple remedies. For example, off-site disposal of 150,000 tonnes of higher concentration mercury impacted materials excavated at the Nexan Former Chlor-alkali Plant in British Columbia was combined with other on-site remedies.

Waste Classification Framework

The majority of the wastes generated during the remediation works would be classified as Hazardous Waste in accordance with the NSW EPA Waste Guidelines (DECC, 2009). Hazardous Wastes are generally not suitable for disposal to landfill in NSW without ‘immobilisation’ in order to avoid release of contaminants into landfill leachate. To enable the wastes to be landfilled, the NSW EPA may grant an immobilisation approval. Immobilisation approvals will only be issued where it is not possible to reuse, recycle or reprocess the waste. Where feasible, treatment to remove or destroy the contaminants is preferable to immobilisation. The reagent added for the immobilisation also also takes up additional landfill space.

Under the immobilisation option off-site macro encapsulation is possible (i.e. containment within a monocell). As part of the soil washing remediation program, Orica applied for a specific immobilisation approval under Section 50 of the Protection of the Environment Operations (Waste) Regulation 2005 in order to dispose of the mercury impacted Hazardous Wastes to a licensed landfill facility. A Specific Immobilisation Approval (SIA)6 was issued for the off-site monocell disposal of Hazardous Wastes generated during the FCAP soil washing remediation program performed in during 2011. This approval involved the construction of an encapsulation cell on the floor of a new industrial waste cell constructed at Sita’s Kemps Creek facility. Waste shipments had to be staged to facilitate the correct layout within the cell.

Special conditions of the SIA included:

6 SIA 2010-S-08 – Orica Australia Pty Limited Mercury Impacted Waste – SITA Environmental Solutions, dated 11 August 2010



The waste subject to the approval must not be mixed with any other waste streams when transported off site or emplaced in the monocell;

Visible free mercury must be separated from the waste prior to disposal off site; and

Any visible free mercury must be disposed of separately.

The availability of this or another similar monocell with the required capacity would need to be secured.

6.3.2 Option Review

6.3.2.1 Technical Feasibility It is considered that disposal of excavated mercury impacted materials is feasible at the Kemp’s Creek monocell provided the waste meets the conditions of the SIA and is received within the availability time frame of the monocell.

However, there are several site specific factors which would also need to be considered.

Implementation

As discussed above (Section 6.2.1) there are several logistical constraints associated with excavating impacted soils and concrete within the TECE. Included in these is the likely requirement for all materials being dispatched for off-site disposal to be placed into lined and sealed containers, most likely skip bins.

Assuming 12 m3 skip bins could be used, the estimated volume (20,000 m3) of materials involved (Section 6.1.2), would require approximately 1,650 skip bins ‘movements’. This would require a considerably higher number of vehicle movements compared to the use of double compartment trucks traditionally used in bulk waste transfer (approximately 25 m3) that would require in the order of 800 roundtrip vehicle movements.

Based on its experience with the soil washing remediation, Orica has indicated that the preparation of skips (i.e. lined and sealed) for off-site transport to monocell would significantly limit the overall rate of remediation. Orica has indicated that a maximum of 4 skip bins could be processed (i.e. lined and sealed) within the available space in the loading bay in the TECE at a given time. On this basis it is likely that between 8 and 12 skips could be processed in a working day. At this rate, the remediation timeframe would be of the order of 6 to 8 months and would likely extend to the hotter summer months thereby exacerbating mercury volatilisation rates and worker risk. . Management of a rotation process would be required to allow delivery of sufficient numbers of skips to the TECE to cater for the through put of excavated materials, while also considering the limited space for storage and manoeuvring of skips on site.

If the SIA for off-site disposal at the Kemps Creek monocell were to be an extension of or similar to the one issued by the NSW EPA for the soil washing remediation project, then a means to separate visible free mercury from the Hazardous Waste would need to be employed prior to loading into the lined skips. No effective method for separating visible free mercury from bulk soil other than physical soil washing or ex situ thermal treatment has been identified. The former has already been unsuccessfully employed, and the latter, which is discussed in this ROAR, could possibly achieve the soil reuse criteria thereby rendering off-site disposal of soil unnecessary.

6.3.2.2 Effectiveness The effectiveness of source removal was described in Section 6.2.2. The off-site management method (i.e. off-site disposal) of removed mercury does not affect the on-site effectiveness of the remedy, as the excavated source material will have been removed from the site. However, there would be no reusable soil available so clean fill would need to be imported to the site.

6.3.2.3 Sustainability The sustainability of source removal was described in Section 6.2.3.

Disposal of mercury impacted materials excavated at the FCAP into Kemps Creek monocell does not satisfy the objective of waste avoidance and resource recovery. Approximately 20,000 m3 (in situ volume) of



mercury impacted materials together with waste activated carbon (generated over 6 to 8 months) from the ECS would require disposal at the monocell. Additional disposal of any recovered free-flowing mercury would also be needed.

As outlined above, based on the required use of skip bins instead of trucks, some 1,600 to 1,800 vehicle movements would be involved in transferring the excavated waste materials to the Kemps Creek monocell. The distance from Orica BIP to the Kemps Creek monocell is approximately 50 km, or 100 km round trip, equating to more than 165,000 km distance over the course of the program.

Assuming a fuel economy in the order of 50 litres of diesel per 100 km for the type of trucks required to carry a 12 m3 skip, the total fuel consumed over the course of the program would be in the region of 80,000 to 90,000 litres.

Importation of clean fill would also require a large number of truck movements. Assuming the use of double compartment trucks traditionally used in bulk transfer (approximately 25 m3), approximately 800 vehicle movements would be required. Assuming a similar haulage distance of 100 km per round trip, the total fuel consumed over the course of the program would be in the region of 40,000 litres.

The “carbon footprint” of off-site disposal is estimated to be in the order of 1000 tonnes of CO2-e based on the assumption that processes were limited to fuel consumption associated with transport of waste to the monocell and clean fill to the site.

6.3.2.4 Protection of the Environment Potential environmental risks associated with source removal were described in Section 6.2.4.

Environmental issues associated with mercury impacted materials removed from the FCAP are transferred to the disposal site (i.e. Kemps Creek monocell), which is designed to manage Hazardous Waste (assuming the restrictions on visible free mercury can be adequately addressed). There is also an environmental risk during transport of impacted materials to the Kemps Creek monocell, though this can be minimised through administrative and engineering controls (e.g. use of lined and sealed skips). However, the potential for accidents, associated losses of containment and vapour emissions is still present.

6.3.2.5 Cost Assessment of relative costs for each of the four remediation options is presented in Appendix A.

6.4 Off-site Disposal with Stabilisation The excavated materials would be stabilised at the FCAP and transported to an off-site waste facility licensed to receive mercury impacted wastes. Stabilisation of the waste prior to transportation off site could be used to reduce human health and environmental risks during transport and allow a portion of impacted materials a lower waste classification. Stabilisation might also be used to address restrictions on visible free mercury in Hazardous Waste being sent to a monocell.

6.4.1 Technology Description A specific requirement of the Management Order is to consider “the requirements for stabilisation of the contamination prior to transportation off site”.

Solidification and stabilisation can be used to treat elemental mercury and inorganic mercury in soil and sludge. Stabilisation can reduce the mobility or volatility of mercury in the media by inducing chemical reactions, while solidification physically binds or encloses the contaminated media within a stabilised mass. Amalgamation, the dissolution of mercury in other metals (e.g. zinc or copper) and solidification to form a semi-solid alloy called an amalgam, is often used for elemental mercury. Solidification and stabilisation does not reduce the total mercury content of the media, but aims to reduce the leachability and volatility of mercury to facilitate disposal or containment of the waste.

Solidification and stabilisation is generally conducted ex situ but can also be conducted in situ. However, in situ stabilisation is not considered further based on the likely difficulty of implementing in situ stabilisation at



the site (e.g. using soil mixing technologies) due to the presence of subsurface structures and significant amount of mercury associated with these structures, uncertainty over the efficacy and long term stability of stabilised inorganic and elemental mercury (see Section 6.4.2.1) and the risk of downward mobilisation of elemental mercury in the soil profile.

The solidification and stabilisation process involves mixing the contaminated media with binders such as Portland cement, sulphur polymer cement, anhydrous calcium sulphate, magnesium oxides, cement kiln dust and resins, and reagents including pH adjustments, and sulphide and phosphate compounds. Conventional solidification and stabilisation using Portland cement cannot effectively reduce the leachibility or volatility of mercury (see Zhang et al, 2009; Orica, 2011). Thus, most attention has been on using stabilising reagents in conjunction with cement for improved solidification and stabilisation of mercury. Many reagents studied for stabilisation of mercury are sulphur based, since sulphur can form relatively stable mercury precipitates (e.g. mercuric sulphide) under certain pH and redox conditions.

6.4.2 Options Review

6.4.2.1 Technical Feasibility

Technology Status

Solidification and stabilisation has been implemented at pilot scale and commercially at full scale. The Unites States Environmental Protection Agency (USEPA) (2007) identified that solidification and stabilisation is the most frequently used technology for soil and waste mercury contamination in Superfund projects reviewed. Though solidification and stabilisation is generally used for the treatment of low inorganic mercury contamination (less than 260 mg/kg), it has been used ex situ for treatment of wastes of higher mercury concentrations and elemental mercury. Solidification and stabilisation is commonly applied ex situ, with stabilised waste disposed in a capped containment cell on site (USEPA 2007).

With the opportunity to dispose of mercury contaminated media in appropriate off-site disposal facilities diminishing in recent years, a number of reagents have been assessed to be effective for solidification and stabilisation of mercury wastes at laboratory and pilot scale, including:

Sulphur compounds, including sulphide (Piao and Bishop, 2006), sulphur polymers (Bowerman et. al., 2003) and nanoscale iron sulphide (Xiong et al, 2009).

Zeolites: A laboratory study by Zhang et al. (2009) demonstrated effective reduction in leachability of mercury from waste using natural zeolites amended with the thiol group (-SH) through formation of HgS complexes and sorption to the zeolite.

Aluminium water treatment residual sludge was hypothesised as a reagent for stabilisation of mercury in soils by Hovsepyan and Bonzongo (2009).

Processed used tyre rubber (Meng et al., 1998; Manchon-Vizuete et al., 2005).

Full scale commercial applications of S/S to treat mercury waste include (USEPA, 2007) the following:

Use of proprietary polymer based solidification and stabilisation for ex situ treatment of mercury contaminated soil (23,000 m3) prior to off-site disposal and capping at Bunker Hill Mining and Metallurgical Complex.

Use of sulphur cement based solidification and stabilisation for ex situ treatment of mercury contaminated soil (20,000 m3) prior to off-site disposal and capping at Rocky Mountain Arsenal.

Ferric sludges (assumed to contain iron oxyhydroxide) and Portland cement were used to stabilise mercury in soils, concrete fines and brine sludges (several thousand tonnes) at a former chloralkali plant site (Zhuang et al., 2003).

All of the studies noted above were performed in the laboratory and/or in the field at small scales (i.e. volumes of waste orders of magnitude less than potentially present at the FCAP) and have not been



demonstrated commercially at full scale. Also, the long term stability of stabilised media is uncertain or has not been assessed with some reagents.

Solidification and stabilisation of inorganic mercury has been shown to be ineffective using a phosphate binder and an inorganic sulphide stabilisation product (USEPA, 2004c). Orica (2011) described an unsuccessful trial of solidification and stabilisation to treat elemental and inorganic mercury in soil at the Orica Yarraville site in Victoria using a sulphide reagent and MgO binder. The trial, undertaken by Entech (Entech, 2007), found that solidification and stabilisation did not achieve long term stabilisation of mercury.

Key considerations for performance and cost of solidification and stabilisation treatment of mercury in soils include (USEPA, 2007):

Mobility of mercury (including form and speciation of mercury, pH of media);

pH of environment (mercury may be more leachable at low and high pH);

Media properties including pH, particle size, presence of organic compounds and moisture content;

Type of binder and reagent;

Mixing of waste and binder; and

Initial volume of waste and volume increase of stabilised waste.

The concentration of elemental mercury would also affect the potential for stabilisation as free elemental mercury is potentially mobile and is significantly less reactive than many forms of inorganic mercury.

Implementation

Under the Management Order the NSW EPA requires consideration of the requirements for stabilisation of the contamination prior to transportation for off-site disposal. While ex situ solidification and stabilisation has been commercially applied at full scale to treat mercury impacted soils, treatability testing would be required to ascertain site-specific leachability, and durability of the stabilised media, reagent selection, reagent dose and processing requirements. Treatability testing would also need to consider site constraints such as high and low pH and chloride, all of which can potentially negatively affect mercury stabilisation.

Stabilisation of the waste prior to transportation off site could be used for the following purposes:

Lower waste classification: solidification and stabilisation may potentially enable a portion of impacted materials a lower waste classification (e.g. restricted solid) compared to disposal as Hazardous Waste at Kemps Creek monocell. Any stabilised materials would require a specific immobilisation approval from the NSW EPA for disposal at landfill facilities as lower category (e.g. restricted solid) waste. However, it is likely that a significant portion of stabilised excavated material would still be classified as Hazardous Waste based on total mercury concentrations exceeding criteria in DECC, NSW (2009), and solidification and stabilisation of this waste would result in an increase in volume. Stabilisation of waste containing total mercury concentrations less than the Hazardous Waste criterion but high leachable concentrations, could potentially enable disposal as Restricted Waste, though this material would not necessarily require removal from the FCAP (being less than 200 mg/kg), and would likely be suitable for reuse on site. Stabilisation will also ‘dilute’ (though not affect mass of mercury) mercury concentrations due to the increase in waste volume from stabilisation chemicals (by a factor of up to two), though this is not considered an appropriate mechanism for solidification and stabilisation.

Reduce risks during transport - transport risks with contaminated mercury have been satisfactorily managed without stabilisation, thus far.

Enable off-site reuse – As discussed above, solidification and stabilisation will result in reduced total mercury concentrations due to the ‘dilution’ effect from added chemicals. However, dilution is not considered an appropriate remediation mechanism.



Stabilisation of excavated materials prior to disposal is unlikely to significantly reduce disposal volume or the requirement to dispose stabilised waste at the Kemps Creek monocell. It is more likely to result in increased disposal volumes, potentially by up to a factor of two, due to bulking effects of stabilisation.

6.4.2.2 Effectiveness The effectiveness of source removal was described in Section 6.2.2. The off-site management method (i.e. ex situ stabilisation and off-site disposal) of removed mercury does not affect the on-site effectiveness of the remedy.


Disposal of mercury impacted materials excavated at the FCAP at Kemps Creek monocell or Restricted Waste landfill does not satisfy the objective of waste avoidance and resource recovery. Although solidification and stabilisation could potentially result in a reduction in the volume of Hazardous Waste, the overall waste volume would increase significantly. On the assumption that a bulking factor of 1.5 occurs due to solidification and stabilisation, the total volume of mercury impacted materials may exceed 30,000 m3, though a portion of this could potentially be disposed of as Restricted Waste. Waste activated carbon from the ECS would also require disposal at the monocell.

As outlined above, based on the required use of skip bins instead of trucks and bulking factor due to solidification and stabilisation, some 2,400 to 2,700 vehicle movements would be involved in transferring the excavated and stabilized waste materials to the Kemps Creek monocell or Restricted Waste landfill. The distance from Orica BIP to the Kemps Creek monocell is approximately 50 km, or 100 km round trip, equating to at least 240,000 km distance over the course of the program.

Assuming a fuel economy in the order of 50 litres of diesel per 100 km for the type of trucks required to carry a 12 m3 skip, the total fuel consumed over the course of the program would be of the order of 120,000 litres.

Importation of clean fill would also require a large number of truck movements. Assuming the use of double compartment trucks traditionally used in bulk transfer (approximately 25 m3), approximately 800 vehicle movements would be required. Assuming a similar haulage distance of 100 km per round trip, the total fuel consumed over the course of the program would be in the region of 40,000 litres.

The “carbon footprint” of off-site disposal was estimated to be in the order of 1,400 tonnes of CO2-e based on the assumption that processes were limited to fuel consumption associated with transport of waste to the monocell. No activities associated with backfilling the excavation with clean fill were factored either.


Environmental issues associated with mercury impacted materials removed from the FCAP are transferred to the disposal site (i.e. Kemps Creek monocell), which is designed to manage Hazardous Waste.

Stabilised waste may represent a reduced risk during transport of impacted materials to the Kemps Creek monocell, transport risks with contaminated mercury have already been satisfactorily managed thus far without stabilisation through administrative and engineering (e.g. use of lined and sealed skips) controls. However, the potential for incidents, associated losses of containment and vapour emissions is still present


6.5 Ex Situ Thermal Technologies 6.5.1 Technology Description Thermal treatment involves physical application of heat and reduced pressure to volatilise contaminants (including mercury) from contaminated soils, sediments and wastes. While thermal treatment is generally



more widely applied to volatile and semi-volatile contaminants in soils, the boiling point of elemental mercury (350° C at 1 atmosphere pressure) allows its volatilisation by thermal processes. However, thermal removal of mercury chloride complexes and mercury bound to organic material can occur at lower temperatures, ranging from 173-193 oC and 200-373 oC, respectively (Comuzzi et al, 2011). A review conducted by Hinton et. al. (2006) suggests a temperature of 250 oC may be sufficient for volatilisation of most mercury in wastes. Thermal treatment of soil and waste that contain mercury has been applied at full scale and tested at the pilot scale (USEPA, 2007).

Ex situ thermal treatment should be considered as a two-step remediation option involving the excavation of contaminated soil from the source zone followed by application of the thermal treatment technology. The excavation step constitutes a generic remediation approach which applies to other ex situ remediation treatment and/or management options, and is evaluated in Section 6.2.

Pre-treatment of contaminated media is required to achieve a uniform waste feed by removal of rubble, extraneous matter such as plastic or rubber, and dewatering to achieve suitable moisture content. Particular effort would be required for pre-treatment (such as segregation and crushing) of mercury impacted concrete at the FCAP. Thus, ex situ thermal treatment is typically part of a treatment train.

Waste streams generated in thermal processes which require treatment include:

Wastewater from condensation of vaporised water in the treated material.

Mercury vapours.

Volatilised organic compounds and thermal degradation compounds (if present in material).

Treated materials.

Vapour treatment may include condensers, scrubbers, filters and sorption columns. Liquid elemental mercury collected from vapour treatment condensers can be treated for disposal or reused.

Treated material can potentially be reused as fill depending on reuse criteria and treatment efficiency.

Key factors influencing the applicability of thermal treatment of mercury contaminated soil include (USEPA, 2007):

Material type, size and volume

System throughput

Presence of extraneous materials

Presence of organic compounds

Particle size

Moisture content

Mercury form and concentration

Required residence time

Ex situ thermal desorption, retorting and high temperature incineration are potentially applicable ex situ thermal treatment methods for mercury.

6.5.1.1 Ex Situ Thermal Desorption (ESTD) Thermal desorption is a treatment technology which is designed to remove contaminants from solid media by volatilisation or decomposition and then removing the volatilised products without combustion of the media or contaminants. Thermal desorption uses rotary kilns and indirectly heated screw or auger systems and is



generally a continuous process more suited to large treatment volumes than retorting and incineration methods. Pre-treated feed material is delivered to the desorber by conveyor or equivalent, and the movement of the rotary drum or auger agitates the waste, promoting mixing and uniform heating. A typical thermal desorption unit for mercury removal would operate at temperatures ranging from 320 to 700 °C (USEPA, 2007). A vacuum can be applied to some systems to increase mercury volatilisation and reduce off-gas volume.

ESTD has been commercially used to treat waste materials which contained low concentrations of mercury (in the order of 1 mg/kg) at volumes similar to that of the FCAP, and small volumes of wastes containing higher concentrations of mercury at trial and laboratory scale. An ESTD treatment plant in Herne, Germany operated by Sita (see Figure A) is capable of treating waste materials containing up to 1,500 mg/kg mercury. No full scale projects have been identified which have treated soils contaminated with elemental mercury using thermal desorption.

The dry and sandy impacted materials, and mercury concentrations, at the FCAP would likely be suitable for treatment and mercury recovery using thermal desorption.

ESTD of mercury impacted materials excavated from the FCAP would be expensive, have high energy requirements, require vapour treatment, and be technically difficult to operate. The advantages of thermal desorption over retorting and incineration include a higher treatment capacity (i.e. shorter remediation time and lower cost), potentially lower energy requirements and potentially lower off gas volumes requiring treatment for indirectly gas fired systems (directly gas fired systems may have more off gas volumes).

6.5.1.2 Batch Retorting Retorting is a batch process, where small quantities of contaminated media are heated in ovens, which are heated either electrically or with fuel burners. Retort ovens typically operate at temperatures of 425 to 540°C and under a vacuum to increase mercury volatilisation and reduce off-gas volume (USEPA, 2007).

Retorting is generally used in industry for recovery of mercury from small volumes of wastes such as sludges generated in chemical manufacture and mining industries, and from industrial equipment. Retorting is mentioned as a potential method of thermal treatment for mercury contaminated materials by USEPA (2007) and is listed by the USEPA as Best Demonstrated Available Technology for high concentration mercury wastes (>260 mg/kg).

While some examples of thermal treatment are illustrated at full and pilot scale, these were chiefly using rotary kilns and desorbers. A small retort was historically operated at FCAP (on part of Block M), ceased to be used in the late 1980s. The retort was used to treat small volumes of solid waste and reportedly had a capacity of one to two tonnes per day. It used hydrogen gas for directly-heated thermal desorption, and water-cooled heat exchangers for mercury recovery. A commercial mercury retort facility operated in southern France until it was shutdown in 2010 as it did not meet its permit requirements (Mavesa Environment, 2012).

The dry and sandy impacted materials, and mercury concentrations, at the FCAP would likely be suitable for treatment and mercury recovery using retorting.

Orica has employed mercury abatement technologies – injection of powdered activated carbon into the baghouse and addition of trimercaptotriazine to the off-gas scrubber solution – at the directly-heated thermal desorption plant treating contaminated soils at the Car Park Waste Encapsulation at BIP. However, the mercury is not one of the primary contaminants and typically is managed at around 5 mg/kg in the feed material.

However, based on case studies batch retorting is limited to treatment capacities of the order of one to five tonnes per day, and has not been demonstrated for treatment volumes similar to those potentially required at the FCAP (USEPA, 2007), most likely due to the significant handling effort and time required for batch processing large waste volumes. Retorting of mercury impacted materials excavated from the FCAP would be expensive, have high energy requirements, require vapour treatment, and require significant handling



effort and long treatment times (in the order of five to ten years based on capacity in the order of 5 tonnes per day), which suggest that implementation of batch retorting at FCAP would not be practicable.

6.5.1.3 Incineration Incineration involves direct heating of materials to destroy contaminants, generally organics, at temperatures higher than retorting through combustion. Incineration is generally applied to relatively small volumes of waste materials to treat organic contaminants potentially with relatively low levels of mercury (USEPA, 1998b), and is not considered practicable for large volumes of heavily impacted materials. Mercury is an element, so it will not be destroyed by incineration.

While commercial incinerators may have treatment capacities of up to 35,000 tonnes per year (e.g. the SAVA plant in Europe (SAVA, 2012)), they are generally limited to low concentrations of mercury (e.g. less than 10 mg/kg) as most incinerators may not be equipped to recover high concentrations of mercury in the off-gas stream. The technology suitable for wastes containing high mercury concentration is not available in Australia.

6.5.1.4 Other Other ex situ thermal treatment methods include microwave heating, infrared heating and steam stripping. These technologies have not been commercially demonstrated for treatment of large volumes of materials of the same scale as required at the FCAP, or are not suitable for mercury treatment, and are not considered further.

6.5.1.5 Vapour Treatment Off-gas treatment would consist of two general stages – the first to cool the vapour stream to recovery the bulk of mercury as condensate and recover heat; the second to further cool the vapour stream and remove particulates and any remaining mercury vapours prior to stack emission. Water vapour condensate would also form in the first stage. Processes and equipment would include quenchers and condensers in the first stage, and heat exchangers, scrubbers, particulate filters and carbon sorption columns. An example of vapour treatment system processes of an ESTD plant are presented in Figure A.



Figure A: System Processes at an ESTD plant in Herne, Germany (SITA)

6.5.1.6 Technology Summary A summary of ex situ thermal treatment technologies is provided in the table below.

Table 1: Ex Situ Thermal Treatment Options Summary

Technology Option

Description Comments

Ex situ thermal Desorption

A continuous ex situ thermal soil treatment process conducted in rotary kilns where sufficient heat is applied to desorb contaminants. Off- gas is produced and requires treatment.

Generally applied to larger volumes of contaminated material (in comparison with retorting or incineration) or where mercury is one of several potential contaminants (i.e. waste materials).

Retorting A batch ex situ process where sufficient heat is applied to desorb contaminants in retort ovens. Off- gas is produced and requires treatment.

Retorting is similar to thermal desorption but is a batch process. However, the batch nature of the process means it is impracticable to treat large waste volumes due to handling effort and extended treatment time frame.

High temperature incineration

Direct heating of materials to destroy contaminants, generally at temperatures higher than retorting through combustion.

Generally applied to waste materials with organic contaminants, potentially with relatively low levels of mercury. Mercury cannot be destroyed. Not considered suitable for high volumes of heavily impacted materials.



Technology Option

Description Comments

Other Microwave heating, infrared heating, steam stripping These technologies have not been commercially demonstrated for treatment of large volumes of materials of the same scale as required at the FCAP.

Based on the above discussion, ex situ thermal desorption is considered the most likely potential ex situ thermal treatment option for remediation of mercury impacted materials at the site.

The following sections review the suitability of the ESTD technology in treating (removing and recovering) mercury from excavated contaminated soil separate from the requirements of the excavation step. An evaluation of excavation of mercury impacted soils is included in Section 6.2.

6.5.2 Option Review


Technology Status

ESTD has been commercially applied a few times to treat the volumes of mercury impacted soils and sludges similar to that potentially required at the FCAP. However, there is no evidence that ESTD has been applied at full scale to large volumes at the concentrations of mercury reported in shallow soils at the FCAP. Thus, application of this technology at the site may require significant lead time to conduct treatability and feasibility assessments. By way of comparison the initial Feasibility Assessment Report for the Orica Car Park Waste Encapsulation project at BIP was published in 2005, including detailed mass and energy balance data, and vendor input. Project commencement occurred six years later in 2011 after extensive community consultation and a lengthy statutory approval process. For a similar thermal treatment plant planned for the Orica Villawood, NSW site, the time from completion of the RAP to commencement of treatment works on site is anticipated to be in the order of six years.

USEPA (2007) identified three full-scale and five pilot-scale projects where ESTD has been applied. However, the thermal treatment references cited by the USEPA are generally not recent examples (projects conducted around 1995), which would suggest that implementation of ESTD is limited. The three full-scale examples included an industrial landfill, a pesticide manufacturer and a metals recycling facility where large volumes (28,000 to 88,000 tonnes) of low level mercury contaminated soils (less than 1.0 mg/kg) had been effectively treated. These sites contained a range of contaminants and it appears that mercury may not have been the primary contaminant of concern. Thermal treatment of mercury impacted soils and sediments have not been utilised as the remediation remedy for identified former chlor-alkali plant Superfund sites (see Section 6.3.1).

An ESTD system in Herne, Germany operated by SITA accepts waste containing up to 1500 mg/kg of mercury, and is likely the only thermal desorption unit accepting mercury waste in Northern Europe (Mavesa Environmental, 2012). The unit is contained within a building to control fugitive emissions. This unit was used to treat materials excavated from a landfill in France which contained low concentrations of mercury (not defined), with treatment costs a factor of 1.5 to 2.0 times compared to typical unit rates.

No full scale projects have been identified which have treated soils contaminated with elemental mercury using thermal desorption.

A range of laboratory- and pilot-scale studies have been conducted on the application of ESTD for treatment of mercury in soils, sludges and wastes. However, the ability to apply these results to full scale at the FCAP without significant further technology development and a site-specific field trial is uncertain. Notable studies include:

The pilot-scale applications of ESTD involved treatment of low volumes (less than 70 tonnes) of soils and sludges with high mercury concentrations (up to 5,000 mg/kg) (USEPA, 2007) to residual concentrations of the order of 10 mg/kg mercury or less.



Chang and Yen (2006) conducted a pilot scale trial of ESTD to treat approximately 4,000 m3 of soils containing approximately 95 mg/kg mercury to residual concentrations of less than 1 mg/kg. ESTD was conducted using a batch process at a rate of 8 tonnes per day.

Comuzzi et al. (2011) studied thermal desorption of mercury from soils and sludges at laboratory scale.

Kunkel et al (2006) demonstrated in laboratory-scale experiments (aimed at application of in situ thermal desorption) that thermal desorption can remove elemental mercury from sands at temperatures ranging from 244 to 259°C (i.e. at temperatures lower than the boiling point of mercury) and in a relatively short period of time.

Though not strictly relevant to thermal desorption Busto et al. (2011) studied the effects of treatment temperature and time on both residual mercury levels and leachability at laboratory scale. A muffle furnace was used to simulate retorting conditions on two composite samples of sludge collected from a former chlor-alkali plant. They demonstrated that treatment for 1 hour at 800°C allowed removal of mercury while treatment at 400°C allowed reduction of leachable mercury.

ESTD has been commercially applied more frequently at full scale to treat volatile and semivolatile organic compounds (such as the Car Park Waste Encapsulation at BIP).

Some key advantages of ESTD (excluding those already discussed associated with source removal) include:

ESTD may be effective in removing elemental and inorganic mercury to lower residual concentrations.

Treated materials may potentially be reused (depending on treatment efficacy).

Greater control over the heating process (compared to in situ thermal treatment) means there is less risk of not meeting treatment goals.

Excavated sandy soils from the site would likely be amenable to application of ESTD.

Key disadvantages of ESTD (excluding those already discussed associated with source removal) include:

Pre-treatment of mercury impacted materials would be required.

Although ESTD has been demonstrated commercially at full-scale for mercury remediation, this has been at relatively low mercury concentrations (i.e. in the order of 10 mg/kg). Applications to mercury concentrations similar to those in shallow soils at the FCAP have only been identified for low volumes of materials (i.e. less than of the order of 100 tonnes).

Treatment of elemental mercury using ESTD at full scale has not been demonstrated.

Large energy consumption. Soil heat capacity, soil type, and degree of saturation affect energy requirements.

Fugitive emissions of mercury vapour must be controlled, with consideration of the close proximity of residential and commercial / industrial areas, and health risks to workers. This is considered a significant risk because of the proximity of the site to residential areas.

Elemental and inorganic mercury captured in the vapour treatment system must be managed via recovery and/or disposal, possibly at a monocell. This represents a significant (in terms of mercury mass) waste stream. Mercury recovered by condensation might be able to be sold for reuse.

Operation and maintenance of the thermal unit and associated pre-processing and vapour treatment systems would likely be technically difficult.

Secondary treatment of wastewater streams from condensed water sourced from the soil would be complex.



Although site investigations at FCAP have not indicated significant concentrations of chlorinated hydrocarbon compounds (which are found in the subsurface to the north of the site – see Orica (2012)), consideration of organic contaminants, their potential combustibility, their potential degradation products (e.g. dioxin formation) and their potential management in the vapour stream would need to be undertaken.

Lead time for planning consent would be up to six years based on similar scale thermal treatment plants in NSW.

Implementation

ESTD treatment would require the following general processes and significant equipment/infrastructure:

Pre-processing – Observations during remediation works performed to date at FCAP have shown that significant mass of elemental mercury (prills) is attached, or in the immediate vicinity of, concrete slabs, drains and footings. Demolition and pre-processing (e.g. crushing to a uniform and manageable size) of concrete rubble and debris would be required prior to thermal treatment. There may be other treatment options for large structures of mercury impacted concrete, such as washing or physical removal of mercury, and these have been discussed in the current RAP (URS, 2010). Equipment and infrastructure may include sieves, screens, shredders and storage areas.

A building to control fugitive emissions - An ESTD unit would likely need to be inside a building to control fugitive emissions of dust and vapours containing mercury during pre-processing and thermal treatment. Provided a full scale ESTD system could be operated within the TECE building currently constructed over Block G, the building could potentially be used to mitigate short-term vapour risks from thermal treatment. However, moving the plant within the TECE to allow staged excavation, including requirements for plant foundations, would be logistically difficult and probably prohibitive. Practical operation and maintenance of a full scale ESTD within a TECE is unlikely to be successful. Because of the presence of fired gas, the TECE would probably require safety modifications (e.g. blast relief walls); and asphyxiation risks with flue gas processing (condensation) inside the TECE would need to be addressed. It is not best practice to operate fired equipment in a fully enclosed building, though ESTD units have previously been used inside large buildings (Mavesa Environmental, 2012). Heat management of the working environment inside the TECE would also be technically challenging.

Thermal desorber unit – This may include pre-dryers, the kiln or combustion chamber, and a cooling kiln for treated materials. Thermal desorber units are most commonly either indirect or directly fired rotary, or heated screw systems. Although a unit similar to the system currently being used by Thiess to treat semivolatile organic contaminants in the Botany area would be used, this actual unit is reportedly not suitable for treating mercury wastes at the FCAP. Thus, an ESTD system would likely be imported from overseas and constructed and commissioned at the site. On completion of remediation decommissioning (including dismantling and decontaminating) the system and return back overseas would be required, which, based on liabilities associated with decontaminating thermal units used to treat polychlorinated biphenyl contaminated materials in Europe, would be technically and financially difficult (Mavesa Environmental, 2012).

Off-gas treatment – Off-gas treatment may include quenchers to remove the bulk of mercury as condensate, heat exchangers, particulate filters and carbon sorption columns.

Mercury recovery – Elemental mercury condensate would be recovered in initial stages of off-gas treatment. Further treatment of recovered mercury may be required to meet end-user requirements. The mercury must be handled, stored and transported using appropriate containers and methods. It is estimated that in the order of 10 tonnes elemental mercury may be recovered and need to be reused or sold.

Solid and liquid waste management – Mercury sorbed to activated carbon in the off-gas treatment will require disposal. Water condensate from vapour treatment may contain mercury and must be treated or disposed of appropriately.



Treated materials management – Treated soil would be classified and reused on site if validated to meet on-site reuse criteria, most likely as excavation backfill. A method to cool the soil – incorporating mercury abatement for the off-gas – would need to be developed. Orica intends to construct a concrete slab over this area for the new salt pad.

Given that energy requirements may be in the order of several hundred kilowatt hours per cubic metre of soil treated (USEPA, 2004b) (i.e. in the order of several gigawatt hours would be required), consideration of new electrical and gas supplies to the site must be made.

Mercury Recovery and Vapour Treatment

While vaporisation of mercury from impacted materials is likely feasible, recovery of mercury from the vapour phase and meeting allowable limits for air emissions is likely to be technically difficult, especially considering the likely low air emission limits (0.18 µg/m3 organic mercury and 1.8 µg/m3 inorganic mercury at one atmosphere and 273 K) and reliability (99.9 percent of the time) (URS, 2010). It is estimated that a total in the order of 10 tonnes elemental mercury may be recovered and need to be reused or sold. The bulk of the mercury would likely be recovered in the initial condensation treatment phase.

The TECE uses two Emission Control Systems (ECSs), each consisting of a treatment train of particulate bag houses and sulphurised activated carbon, to treat air within the building. Although this system could be used to continue to treat low-level fugitive emissions of mercury from excavation, pre-processing and materials handling, it would not be suitable to treat off-gas from the ESTD unit which will be of high temperature and contain high mercury loads.

Although site investigations at FCAP have not indicated significant concentrations of chlorinated hydrocarbon compounds (which are found in the subsurface to the north of the site – see Orica (2012)), consideration of organic contaminants, their potential combustibility, their potential degradation products and their management in the vapour stream must be made.

Waste streams from the vapour treatment unit would include recovered elemental mercury, treated (meeting air emission criteria) off-gas, activated carbon containing sorbed mercury, and water condensate containing mercury and potentially other contaminants.

6.5.2.2 Effectiveness The effectiveness of source removal was described in Section 6.2.2. The management method (i.e. ex situ thermal treatment and on-site reuse) of excavated material does not affect the remediation effectiveness. However, ESTD represents a greater risk to surrounding human health receptors (workers and residents) due to the higher potential for mercury vapour emissions from the thermal treatment unit. Although mitigation will reduce the probability of emissions external to the site, the scale of conversion of liquid mercury to vapour at the Botany site is probably unprecedented and the consequences of even a small release may be cause for significant community alarm.


In addition to fuel and energy use for source removal, application of ex situ thermal treatment technologies consumes a significant amount of energy. Heating energy requirements for ex situ thermal treatment may be less than for ISTD (Section 7.1.2.1), but additional energy for excavation and pre-processing is required. Ex situ thermal treatment systems have significant energy requirements, possibly in the order of several hundred kilowatt hours per cubic metre of soil treated (USEPA, 2004b) (i.e. in the order of several gigawatt hours would be required).

The “carbon footprint” of ESTD is of the order of several 1,000 tonnes of CO2-e based on the following assumption:

Processes considered in this analysis were limited to electricity consumption associated with thermal treatment. The carbon footprint associated with source removal was discussed in Section 6.2.3. The carbon footprint associated with management of treated materials was not included.



Provided treated materials are reused on site, ex situ thermal treatment will result in significantly lower volume and mass of mercury impacted material required to be disposed. On the assumption that in the order of 10 tonnes of mercury is removed from the FCAP via excavation and approximately 80 % is recovered via ESTD and reused or sold, the mass of mercury requiring disposal may be in the order of two tonnes. This mercury mass requiring disposal as Hazardous Waste would largely be sorbed to activated carbon used in vapour treatment and may be in the order of 20 tonnes7 rather than in the order of 30,000 m3 of impacted materials. Wastewater condensate impacted by mercury would also require treatment.

The reduced volume of impacted materials requiring disposal would have a commensurate reduction in vehicle movements and corresponding fuel use. Significant fuel use for transport of ESTD equipment to and from FCAP from overseas would be required.


Ex situ thermal treatment would result in a net removal of a substantial portion of mercury from the environment (by being recovered and reused). Although off-site reuse of treated material could be maximised and off-site disposal volumes reduced, a lower volume of mercury impacted materials would still require disposal and condensate wastewater would require treatment.

ESTD results in an increased risk of fugitive mercury vapour emissions from vapour treatment system. Thermal treatment is the one option that requires the conversion of all mercury to vapour. This can be mitigated using appropriately designed and operated vapour treatment system but remains a high residual risk because of the proximity of the plant to residential areas.


7 On the basis of an effective sorption capacity of 100 kg mercury per tonne of carbon.



7.0 IN SITU THERMAL TECHNOLOGIES 7.1.1 Technology Description In situ thermal remediation approaches involve the application of energy to the subsurface to heat impacted materials, promoting desorption and volatilisation of contaminants. Vapour extraction and control measures, including vapour extraction wells and a vapour cap at ground surface, ensure volatilised contaminants are removed from the subsurface, which can then be captured and treated. Degradation of organic contaminants will also occur. Although electrical current is typically applied to heating elements in the subsurface, steam injection into the subsurface can also be used. Liquid extraction may be required depending on depth of treatment required and when groundwater flow rates are high and/or when the contaminant being recovered is of low volatility. The key design criteria include contaminant type, remediation goals and site hydrogeology.

Of the available in situ thermal treatment methods, in situ thermal desorption (ISTD) is relevant to treatment of mercury. The two most commonly applied types of ISTD technologies include in-situ thermal conductive heating (TCH) and electrical resistance heating (ERH). Other options include radio-frequency heating, and vitrification.

Extent of Remediation

ISTD would target the most significant accessible mercury source areas, namely Block G. ISTD could potentially be applied in this area under two scenarios:

ISTD targeting mercury in the vadose zone only.

ISTD targeting mercury in the vadose and saturated zones (i.e. to bedrock).

7.1.1.1 TCH TCH is the application of thermal energy to in situ contaminated soils, using an array of electrical resistance heaters or conductive rods placed in wells. Heat is transferred from heating wells to the subsurface via thermal conduction and radiant heat transport. As the soil temperature increases to 100 oC, pore water vaporises, and there is also a contribution through convective heat transfer from the steam. With TCH the soil temperature can be varied based on energy applied, and bulk soil temperatures of the order of 600 °C can be achieved. Since there is low variability in thermal conductivity of different soil types, TCH is not significantly influenced by soil type, but heat transfer to groundwater can be significant depending on groundwater flux. Heating times of several months may be required to achieve target temperatures, and heating periods for contaminant removal of up to nine months may be required depending on contaminant type (i.e. longer periods for low volatility recalcitrant compounds), remediation goal and site geology. Typically, an array of closely spaced (of the order of metres) heater and vacuum wells are installed, though surface heater blankets can be used to treat shallow soils.

Volatilised contaminants are collected by a soil vapour extraction system which applies a vacuum to create a vapour capture zone. Off-gas is captured above ground and treated. A surface seal is also typically required. Degradation of organic contaminants can also occur, particularly in the vicinity of heater wells. Vapour extraction wells are heated to avoid condensation.

TCH has been applied to treatment of volatile and semivolatile organic contaminants (Stegemeier and Vinegar, 2001), and is potentially applicable for treatment of mercury in the subsurface at the site based on the similar volatility of mercury to some organic contaminants such as polychlorinated biphenyls (PCBs). A minimum treatment temperature of the order of 300 to 350 oC would likely be required for desorption and volatilisation of elemental mercury and inorganic mercury.

TerraTherm is the sole commercial vendor for ISTD using TCH.

7.1.1.2 ERH ERH involves the application of electrical currents through impacted subsurface between an array of electrodes, with the resistivity of the soil causing heat generation and volatilisation of contaminants. This



approach is limited by the boiling temperature of water (100 oC) (Kunkel et al. 2006). Once the soil pore water has been boiled off, the electrical conductivity of the soil becomes negligible and only minimal heating is achievable.

Since the required temperature for mercury vaporisation is in the order of 350 oC, ERH is not likely applicable to remediation of mercury and is not considered further. Furthermore, the targeted source area is in the unsaturated zone, where electrical conductivity is very low.

7.1.1.3 Others Radio-frequency heating used in conjunction with soil vapour extraction is not considered further as it is in developmental stage.

In situ vitrification is not considered further as it is likely to have significant risks associated with controlling fugitive emissions, and risks of detrimental impacts on geotechnical properties of the subsurface and surrounding infrastructure.

Steam or hot air heating, combined with soil vapour extraction, is not considered further as the heating temperature would likely be insufficient to volatilise mercury in the subsurface.

7.1.1.4 Vapour Treatment Recovery of mercury and treatment of the captured vapour stream would be required. The recovery and treatment process would be similar to that for ESTD described in Section 6.5.1.5, although vapour stream temperatures would be lower, in the order of 350 °C.

7.1.2 Option Review The following section presents an assessment of the potential application of the ISTD remediation option (using ECH technology) at the site.


Technology Status

Golder is not aware of ISTD technology being applied to mercury soil remediation at full-scale, thus, ISTD is considered in the developmental stage for application to mercury. The only known applications of ISTD to treat mercury have been at laboratory and field-trial scales (Hinton and Veiga, 2001; Kunkel et al. 2006; Seibert, 2005). Kunkel et al. (2006) demonstrated in laboratory-scale experiments that ISTD can remove elemental mercury from sands at temperatures ranging from 244 to 259 °C (i.e. at temperatures lower than the boiling point of mercury) and in a relatively short period of time, and some inorganic compounds (e.g. HgS) may volatilise at lower temperatures (e.g. 200 oC) (see Hinton and Viega, 2001) (though HgO may be less volatile). This is consistent with thermal desorption removal of semivolatile compounds (e.g. PCBs) at temperatures lower than the contaminant’s boiling point (Kunkel et al., 2006).

ISTD has been used frequently to treat volatile organic compounds at full-scale (e.g. USEPA, 2004b), and less frequently used to treat low volatility organic contaminants such as PCBs (which have a similar volatility as mercury) at pilot- and full-scale (e.g. Baker et al., 2006; Vinegar et al., 1997; USEPA, 2004a). However, many of these applications were for relatively small treatment volumes (less than 1000 m3) relative to the volume of mercury impacted soils at the FCAP. Notable full-scale ISTD projects of similar scale to the FCAP for low volatile organic compounds, which may be relevant to potential implementation at FCAP, include:

Alhambra, CA – Former Pole Yard / Creosote Site: 12,000 m3 silty, sandy soil to 32 m depth was treated using ISTD. The first stage of treatment involved seven months of heating (soil temperatures ranging from 260 – 400°C).

Rocky Mountain Arsenal Hex Pit – Approximately 2,000 m3 soil impacted by residuals from pesticide manufacturing was treated by ISTD. Although the target treatment temperature of 325 oC was reached after 85 days, treatment was ceased due to corrosion of heater elements. Wastes were excavated and capped.



The key advantages of ISTD at the site include:

Excavation and disposal of mercury impacted soils is not required.

Mercury is removed from the subsurface and can be recovered. Though not demonstrated at full-scale, laboratory and field-trial studies show that ISTD may be effective in removing elemental mercury to low residual concentrations (i.e. below 90 mg/kg).

Key constraints of implementation of ISTD at the site include:

Not demonstrated commercially or at full-scale for mercury remediation.

Efficiency of removal of inorganic mercury is not certain. Since ISTD of mercury does not result in degradation or destruction of mercury (as occurs for organic contaminants), but rather a transfer from solid to vapour phase, extended heating period may be required in order to ensure even heating of the treatment zone and sufficient time for diffusion out of soil pores to achieve low residual concentrations. Geological heterogeneities could result in uncertainty in vapour migration pathways and physical entrapment of mercury vapours.

Some inorganic forms of mercury at the site (e.g. HgO) may be more difficult to volatilise.

There is a very high potential for lateral and particularly vertical (downward) dispersal of elemental mercury at the condensation front of the ‘steam zone’ (i.e., at the outer edge of the heated zone). As the temperature increases, the properties of elemental mercury (e.g. viscosity) may also change, facilitating lower pore entry pressures and potentially increasing mobility. It is possible that the mass movement of liquid elemental mercury through desiccated silica sand will be greater than mass removal by volatilisation. The likely downward extent of mercury mobilisation is unknown. No low permeability zones have been identified above the water table and it would be likely to exacerbate mass transfer into (i.e. contamination of) groundwater. This could only be controlled with a low permeability cut-off wall (which would render partial source removal by thermal treatment obsolete).

Potential changes to structural properties of the subsurface, such as drying and cracking of peaty/clay layers, due to elevated temperatures for prolonged periods is a potential (although unlikely) risk to surrounding infrastructure associated with operating industrial facilities. Drying out and cracking of the subsurface may also generate preferential pathways for pooled mercury migration.

Observations during remediation works performed to date at FCAP have shown that significant mass of elemental mercury (prills) is attached, or in the immediate vicinity of, concrete slabs, drains and footings. The effectiveness of ISTD to volatilise this elemental mercury associated with concrete is uncertain given its close proximity to the surface, highly heterogeneous nature of the concrete structures and rubble, low thermal conductivity and limited vapour pathways to effect mass transfer.

ISTD would require a large energy consumption. Soil heat capacity, soil type, and degree of saturation affect energy requirements. In the saturated zone, the largest contribution to the initial energy requirement is the heat capacity (latent heat of vaporization) of water, though heat losses to groundwater flowing through the area will be significant. For application in the vadose zone, energy for vaporisation of soil moisture and heat losses to ground surface will be significant.

Fugitive emissions of mercury vapour must be controlled, with consideration of the close proximity of residential and commercial / industrial areas, and health risks to workers. This requires a surface vapour barrier and a vapour extraction and treatment system. Control of fugitive emissions would likely be more complex and difficult than control of fugitive emissions from source removal and ESTD options due to possibility of preferential vapour migration pathways.

Elemental and inorganic mercury captured in the vapour treatment system must be managed via recovery and/or disposal, possibly at a monocell. This represents a significant (in terms of mercury mass) waste stream.



Hydraulic control may be required to minimise groundwater flow through the treatment area if the treatment zone extends below the water table. Due to the difficulty in treating extracted groundwater impacted with mercury, a low permeability cut-off wall would likely be a more practicable hydraulic control method.

Significant volumes of mercury contaminated carbon would be generated by secondary treatment of the air stream after condensation of mercury, and treatment of the aqueous condensate.

Secondary treatment of waste water streams from condensed water sourced from the soil would be complex.

Installation of deep wells (for heating, liquid/vapour extraction and monitoring) in the treatment zone (i.e., inside the TECE) could be significantly impeded by the roof of the TECE, which is nominally 8 m high.

Implementation

ISTD could potentially be applied in this area under two scenarios:

ISTD targeting mercury in the vadose zone only (i.e. 5 – 6 m bgsl): This would be simpler and less costly to construct. Heater wells, a vapour barrier and vapour extraction wells would be required. However, the risk of lateral and vertical mobilisation of mercury at the condensation front within the aquifer is considered significant.

ISTD targeting mercury in the vadose and saturated zones (i.e. to bedrock 20-25 m bgsl): This option would have higher cost and necessitate construction of a containment wall in addition to the ISTD infrastructure (heater wells, vapour barrier and vapour extraction wells). However, the risk of mobilisation of mercury within the subsurface is greatly reduced due to heating of the entire depth of aquifer (below identified mercury impacts) and containment wall which would limit vertical and lateral movement of mercury, respectively.

The sandy soils underlying the site are amenable to application of ISTD in that installation of heater and vacuum wells is feasible and high permeability sands are ideal for vapour extraction (provided a vapour capture zone can be established). It is noted that in situ thermal treatment has previously been considered for use in treating chlorinated organic compound source areas at the Botany Industrial Park, but was found to be not practicable (Orica, 2012). Given that ISTD treatment of mercury has not been proven at commercial full-scale projects, it is likely that a field trial to assess feasibility of application at the site and removal efficiency would be required.

The current site surface contains significant concrete slabs, footings and demolition waste. These may be required to be removed prior to installing heating and vapour extraction wells and a surface vapour barrier, or could be capped.

ISTD is proprietary technology and control systems and heater wells would likely be imported from overseas. The majority of other equipment and infrastructure may be sourced locally. On completion of remediation, decommissioning of ISTD infrastructure would be required, which may include disposal of mercury impacted equipment and materials.

Treatment time is uncertain, however based on ISTD treatment times for PCBs, may be in the order of up to six or nine months.

A vapour capture system would be required, including vapour extraction wells and a surface vapour barrier (similar to as described in Section8.0). Treatment of extracted vapour (e.g. condensers, heat exchangers, filters and carbon sorption columns) would also be required. Captured elemental mercury and mercury on sorption media must be managed, most likely via disposal at a monocell.

Golder assumes that the TECE building currently constructed over Block G would need to be dismantled to enable site access and an alternative vapour management system installed.



Elemental mercury condensate would be recovered in initial stages of off-gas treatment. Further treatment of recovered mercury may be required to meet end-user requirements. The mercury must be handled, stored and transported using appropriate containers and methods. It is estimated that in the order of 10 tonnes elemental mercury may potentially be recovered and reused or sold.

If ISTD is applied to the saturated zone, hydraulic control using groundwater extraction and treatment would likely be required. Given the high permeability of the Botany Aquifer, extracted groundwater volumes would be significant (i.e. of the order of hundreds of kilolitres per day), which would have to possibly be treated and then disposed of appropriately. For this reason, if hydraulic control is required, a low permeability cut-off wall (see Section 8.0) would be preferable.

Solid and liquid waste management requirements include mercury sorbed to activated carbon in the off-gas treatment which will require disposal. Water condensate from vapour treatment may contain mercury and must be treated or disposed of appropriately.

Given that energy requirements may be in the order of several hundred kilowatt hours per cubic metre of soil treated (USEPA, 2004b), in the order of several gigawatt hours would likely be required for treatment of shallow soils and tens of gigawatt hours would likely be required for treatment to depth. A new electrical power supply to the site would likely be required.

Mercury Recovery and Vapour Treatment

While vaporisation of mercury from impacted materials is likely feasible, recovery of mercury from the vapour phase and meeting allowable limits for air emissions is likely to be technically difficult especially considering the likely low air emission limits (0.18 µg/m3 organic mercury and 1.8 µg/m3 inorganic mercury at one atmosphere and 273 K) and reliability (99.9 percent of the time) (URS, 2010). It is estimated that a total of in the order of 10 tonnes elemental mercury may be recovered and need to be reused or sold. The bulk of the mercury would likely be recovered in the initial condensation treatment phase.

The TECE uses two Emission Control Systems (ECSs), each consisting of a treatment train of particulate bag houses and sulphurised activated carbon, to treat air within the building. Although this system could be used to continue to treat low-level fugitive emissions of mercury from excavation, pre-processing and materials handling, it would not be suitable to treat off-gas from the ISTD unit which will be of high temperature and contain high mercury loads.

Although site investigations at FCAP have not indicated significant concentrations of chlorinated hydrocarbon compounds (which are found in the subsurface to the north of the site – see Orica (2012)), consideration of organic contaminants, their potential combustibility, their potential degradation products and their management in the vapour stream must be made.

Waste streams from the vapour treatment unit include recovered elemental mercury, treated (meeting air emission criteria) off-gas, activated carbon containing sorbed mercury, and water condensate containing mercury and potentially other contaminants.

7.1.2.2 Effectiveness Although ISTD has been shown to be effective at removing elemental mercury at a laboratory scale, efficiency of removal of inorganic mercury and at full-scale is less certain (though it is noted that ESTD has been shown to be effective at removing mercury from soils – see Section 6.5.2.1). Provided ISTD is shown to be effective, removal of elemental and inorganic mercury from the source area will likely provide long-term protection to human health and the environment.

The potential benefits of ISTD treatment of mercury source areas at the site include:

Human health:

Mitigation of unacceptable risks to site workers by prevention of direct contact with impacted soils and inhalation of impacted dust.



Mitigation of unacceptable risks to site workers by prevention of mercury vapour emissions (assuming vapours from residual mercury below depth of excavation do not represent an unacceptable risk).

Thermal treatment of mercury impacted soils is expected to result in removal of a substantial portion of mercury from the treated area, significantly reducing (but perhaps not entirely removing) the ‘legacy’ issues associated with the mercury present beneath the FCAP.

Environmental:

Treatment to bedrock would remove residual mercury currently present in the saturated zone, thereby reducing dissolution of secondary mercury sources in the saturated zone and reducing impacts to downgradient groundwater.

The HHERA concluded that there were no unacceptable risks to the environment associated with mercury in groundwater downgradient of the site. However, with source control, modelling predicts that capture of mercury impacted groundwater downgradient of the site will occur at the PCA and SCA more rapidly (within 60 to 100 years) than with no source control. Since ISTD results in mercury removal from the source area, rainfall infiltration into the subsurface will no longer act as a mechanism for mercury impacts to groundwater in the treated area, thereby reducing impacts to downgradient groundwater and decreasing the time for aquifer restoration. Treatment to depth of aquifer would have the greatest environmental benefit.

ISTD represents a potentially greater risk to surrounding human health receptors (workers and residents) due to the higher potential for mercury vapour emissions from the thermal treatment unit. Although mitigation will reduce the probability of emissions external to the site, the scale of conversion of liquid mercury to vapour at the Botany site is probably unprecedented and the consequences of even a small release may be cause for significant community alarm.

Other potential limitations of ISTD application at mercury source area at the sites include:

ISTD application will significantly increase the potential for direct exposure of workers to mercury vapours during remediation.

In the application of ISTD to the vadose zone only:

Mercury present in shallow soils or saturated zone outside the area of treatment, and associated risks to human health and the environment, will not be affected.

Although reduction in infiltration will reduce ongoing impacts to shallow groundwater, it is noted that dissolution of elemental or previously sorbed inorganic mercury will still occur as groundwater passes through the source area.

There is a significant risk of causing lateral and vertical mobilisation of mercury during implementation of ISTD in the vadose zone only.

Employing ISTD through the full depth of the aquifer beneath Block G (or at least from below the source area) will mitigate downward mobilisation, but not necessarily lateral migration.

7.1.2.3 Sustainability ISTD has significant energy requirements (possibly in the order of tens of gigawatt hours for the vadose zone).

On the basis that operation of two heavy equipment units (e.g. drill rig and excavator) would be required for installation of the below ground ISTD system at the FCAP, and assuming a fuel usage of 100 litres of diesel per day per equipment unit, the total fuel consumed over the course of the installation (approximately two months) would be in the order of 12,000 litres.



The “carbon footprint” of ISTD is estimated to be in the order of 1,000 tonnes of CO2-e for treatment of vadose zone and in the order of 10,000 tonnes CO2-e for treatment to depth. This estimate is based on the assumption that processes considered were limited to installation of a below ground ISTD system and electricity consumption associated with thermal treatment.

Provided treated materials are reused on site, ex situ thermal treatment will result in significantly lower volume and mass of mercury impacted material required to be disposed. On the assumption that in the order of 10 tonnes of mercury is vapourised and removed from the FCAP using ISTD, of which approximately 80 % is recovered via vapour treatment and then reused or sold, the mass of mercury requiring disposal may be of the order of two tonnes. This mercury mass would largely be sorbed to activated carbon used in vapour treatment, which may be in the order of 20 tonnes8 waste material. Mercury impacted activated carbon would likely require disposal as Hazardous Waste at a monocell. Wastewater condensate impacted by mercury would also require treatment.

The reduced volume of impacted materials requiring disposal would have a commensurate reduction in vehicle movements and corresponding fuel use. Significant fuel use for transport of ESTD equipment to and from FCAP from overseas would be required.

7.1.2.4 Protection of the Environment Short-term environmental considerations include:

Increased risk of lateral vapour (and consequently condensate) migration particularly in the unsaturated zone if the vapour capture system is not effective.

ISTD results in an increased risk of fugitive mercury vapour emissions from the vapour treatment system. Thermal treatment is the one option that requires the conversion of all mercury to vapour. This can be mitigated using appropriately designed and operated vapour treatment system but remains a high residual risk because of the proximity of the plant to residential areas.

Significant risk of increased lateral and vertical mobilisation of mercury during soil heating.

Management of elemental mercury and sorbed mercury captured in the vapour treatment system.

ISTD would result in removal of a substantial portion of mercury from the treated area, significantly reducing (but perhaps not entirely removing) the ‘legacy’ issues associated with the mercury present beneath the FCAP. However, these issues are transferred to the captured elemental mercury and mercury containing treatment media, which must still be managed.

7.1.2.5 Cost An assessment of relative costs is presented in Appendix A.

8 On the basis of an effective sorption capacity of 100 kg mercury per tonne of carbon.



8.0 ON-SITE CONTAINMENT 8.1.1 Technology Description On-site containment of contaminated materials and source areas is a mature remediation technology that has been widely applied in Australia, Europe and North America. Contaminated materials remain on site but risk of exposure to humans is significantly reduced and environmental risks are mitigated via minimising migration of contaminants and likelihood of direct exposure to receptors. Containment methods include vertical and horizontal barriers or caps. Institutional controls generally are used in conjunction with containment to further limit the potential for unintended access to the contained materials.

Containment of contaminated materials is recognised as an appropriate remedial response when other treatment technologies are not practicable for the following reasons (USEPA, 1997a/b):

Treatment technologies are not technically feasible, are excessively costly or are not available within a reasonable time frame.

Large volume or area of materials or complexity of the site may make implementation of the treatment technologies impracticable.

Implementation of a treatment-based remedy would result in greater overall risk to human health and the environment due to risks posed to workers, the surrounding community, or environment during implementation (to the degree that these risks cannot be otherwise addressed through implementation measures).

On-site containment remediation alternatives identified include:

Capping: Capping mercury impacted areas can reduce human health risks from direct exposure to impacted soils and dust, and vapour emissions. Capping can also result in environmental benefits by prevention of rainfall infiltration, which is a potential source of mercury to groundwater, and by controlling erosion. Given the intended ongoing industrial site use, a concrete slab will be incorporated into the cap suitable for use as a new pad for the salt stockpile.

Low Permeability Cap. Includes concrete slab and/or low permeability clay layer to prevent direct exposure to impacted soils and dust, and limit the potential for erosion and dispersal of impacted soils. A low-permeability cap could also restrict ingress of rainwater infiltration which could leach mercury from the shallow soil. Depending on the cap thickness, vapour emissions due to attenuation and dispersion mechanisms may also be mitigated.

Vapour Barrier. Includes synthetic liner or sealant (e.g. ‘Liquid Boot’ type product) installed beneath a cap to restrict mercury vapour egress. Could also restrict ingress of rainwater infiltration which could leach mercury from the shallow soil.

Low Permeability Cap and Vapour Barrier. A multi-layered cap incorporating a vapour barrier.

Containment: Barriers can minimise ongoing contamination of groundwater by mercury contaminated soils by reducing the movement of contaminated groundwater off-site or limiting the flow of uncontaminated groundwater on site. Barriers at the site could also minimise lateral movement of elemental mercury and control vapour diffusion in the vadose zone. Examples of containment technologies include:

Vertical Barriers. Includes slurry walls, grout curtains, sheet-pile walls, and geomembrane walls extending downward from the ground surface and keyed into bedrock or low permeability residual clays at the base of the aquifer.

Groundwater Gradient Control. Includes both up gradient and down gradient controls such as interceptor trenches and/or groundwater extraction wells to prevent or minimise migration of groundwater through the source area or capture of impacted groundwater down gradient of the source area. This approach requires active groundwater extraction/treatment.



Horizontal barriers. Construction of an in situ horizontal barrier could prevent further vertical migration of elemental mercury or inorganic mercury. However this is not considered an established technology, would be difficult to implement and have limited benefit to mitigating human health risks.

Cap and Containment: A combination of capping and passive hydraulic control of groundwater.

8.1.1.1 Technology Summary Containment technologies are summarised in Table 2 below.

Table 2: Containment Options Summary

Technology Option Description Comments

Capping

Low Permeability or Multilayered Cap

Various types of multilayered caps which consist of an upper layer (most likely cement slab suitable for ongoing industrial use), a drainage layer and geomembrane or compacted clay liner.

This alternative would include additional site grading in addition to multilayer cover construction. May require a vapour barrier or vapour extraction and treatment system.

Vapour Barrier A low permeability layer (synthetic liner or sprayed coating) to control vapour egress. Ventilation and management of vapour emissions may be required.

A low permeability cap would also be required.

Vertical Barriers

Slurry Wall (trench) Excavation of trench, typically 0.6 m to 1.2 m wide, using conventional trenching techniques, filling trench with bentonite slurry to maintain trench wall stability, then backfilling with a soil – bentonite, soil-bentonite-cement or bentonite-cement mixture.

A slurry wall could be utilised for groundwater containment around the perimeter of the mercury source area. A soil-cement-bentonite slurry wall may be preferable at the site due to its structural properties. The wall will also restrict lateral migration of mercury vapour in the vadose zone.

Cutter soil mixing (CSM) In-ground mixing process. Purpose-made 2.5 m x 0.6 m soil cutter device cuts itself into the ground to full wall depth. Wall is formed by controlled injection and mixing of cement and bentonite grouts into the soil during the descent and extraction of the cutter device. Wall comprises overlapping panels so constructed in segments.

Similar end product to soil-cement-bentonite slurry wall. Process can be varied with depth to provide different wall material mix in vadose versus saturated zone.

Slurry wall (vibrating beam) A steel H-beam is vibrated into the ground and slowly withdrawn. As the beam is withdrawn cement grout or bentonite is injected into the void forming a thin wall. Wall is built up with closely spaced, overlapping treatments.

This option will probably not be as effective as the trench slurry wall due to the thickness of the wall and lack of continuity.

Grout Curtain Chemical grout or polymers are injected into the soil to fill voids to form a barrier wall.

Insufficient actual experience available to use as basis for design. The success of this option is not as predictable as it is for a slurry wall.

Sheet Piling Prefabricated steel or geomembrane panels that interlock to form a continuous wall.

Installation of these systems would likely be feasible but may be difficult to depth (approximately 20 m) and in the dense sands encountered at the site. Increased corrosion of carbon steel without cathode protection or coatings may occur in brine plume.

Gradient Control



Technology Option Description Comments

Extraction Wells Extraction wells are installed to control groundwater gradients such that the migration of impacted water is reduced or eliminated. Treatment of extracted groundwater would be required.

This alternative would only restrict groundwater flow through the source area or control off-site migration of impacted groundwater. This alternative is technically feasible based on existing use of groundwater extraction for hydraulic containment in the Botany aquifer. However, the high permeability of the aquifer means that high extraction rates would be required. The complexity of treatment of both chlorinated hydrocarbons and mercury requires evaluation. This option alone would not control potential vapour diffusion in the vadose zone.

Collection Trenches Groundwater collection trenches would be excavated perpendicular to the direction of groundwater flow and backfilled with gravel or stone. Groundwater would be collected in sumps and extracted for treatment.

Collection trenches are not considered the most efficient method of gradient control at the site given the required depth of a trench, waste soil generated by trench construction and feasibility of gradient control using groundwater extraction bores.

Preferred Option

Based on the above table, a multilayered low-permeability cap with vapour barrier, suitable for ongoing industrial site use, with or without a low-permeability vertical slurry or CSM cut-off wall is considered the most appropriate potential containment technologies to meet the remediation objectives for the site.

Although localised ‘hotspots’ of mercury impacted soils have been identified in accessible areas at Block M and Block A, shallow soils at Block G are inferred to contain the most significant mass of mercury compared to other Blocks within the site. It may, however, be practical to place Block M contaminated soils in Block G for containment. A containment approach would target the greater area of Block G as summarised below:

A cap (with vapour barrier) would be installed above the inferred mercury source area to address potential unacceptable risks to human health, with the design to incorporate ongoing industrial site use. A cap would also control infiltration, thereby restricting mobilisation of mercury in shallow soils, which are inferred to be a potential significant source of mercury to groundwater.

A cut-off wall installed around the perimeter of the inferred source area (four-sided) or a three-sided cut-off wall along the upgradient groundwater boundary to bedrock (approximately 20 to 25 m bgsl) would act as a hydraulic barrier below the groundwater table. This would minimise mercury impacts to downgradient groundwater quality. Such a wall may also function as a vapour/diffusion barrier in the vadose zone and restrict potential lateral migration of elemental mercury.

The combination of the cap with cut-off wall may negate the need for groundwater extraction from within the containment area to maintain appropriate hydraulic heads.

Mercury impacted soils excavated from hotspots at other areas, such as Block M, could be placed within the containment area rather than disposed of off site.

A cut-off wall could be combined with other remediation options, such as select excavation and off-site disposal.

8.1.2 Option Review


Technology Status

Surface caps and low permeability cut-off walls are mature technologies and have been widely applied in Australia, Europe and North America. Capping and containment systems have been applied to control



mercury sources at former chloralkali sites (e.g. Ulrich et al., 2007), mercury in waste soil and sludges (e.g. USEPA, 1997) and contaminated groundwater (e.g. Ryan and Spaulding, 2007; Spaulding, 2007), and is a common technology used to manage large areas or volumes of contaminated soils (USEPA, 1997a). A review of former Chlor-alkali plant sites in North America indicates that the main remediation remedy for soil and sediment impacted by mercury involves on-site containment, including capping and/or on-site disposal in an engineered landfill, including at the following sites:

Alcoa/Lavaca Bay Superfund Site, Texas, USA

Holtra Chem Superfund Site, North Carolina, USA

LCP Chemicals Superfund Site, Georgia, USA

Berlin Former Chlor-Alkali Facility Superfund Site, New Hampshire, USA

Georgia-Pacific West Corporation Chlor-Alkali Plant, Washington, USA

Occidental Chemical Corporation Chlor-alkali Plant, Delaware, USA

Olin McIntosh Superfund Site, Alabama, USA

Weyerhaeuser Longview Chlor-alkali Plant, Washington, USA

Hanlin-Allied-Olin Superfund Site, West Virginia, USA

Olin Saltville Waste Disposal Ponds Superfund Site, Virginia, USA

Containment technology is locally available, commercially demonstrated, and has a relatively short lead and implementation time.

Vapour barriers have had less widespread use at contaminated sites in Australia, though they are commonly installed at landfills and have been used to control vapour emissions at many sites in Europe and North America. There are several commercially available vapour barrier products (e.g. Cetco’s ‘Liquid Boot’ system), as well as geomembrane systems that have been widely used to control methane emissions at landfill sites in Australia and worldwide. Combining a cap with vapour barrier and a cut-off wall has had less widespread application at contaminated sites.

Some key advantages of capping and containment of mercury source areas at the site include:

Commercially available and demonstrated technology.

Relatively simple and rapid to implement.

A variety of barrier materials are available and easily attainable.

Uses standard construction equipment and labour.

Surface caps and vertical barriers can be more economical than excavation and removal of waste, and thermal treatment.

Caps and vertical barriers can be applied to large areas or volumes of waste.

Avoids use of monocell space and risks associated with removal and transport.

Provides a total remedy that addresses all mercury present in the targeted area.

Provides a relatively passive system that does not rely on active management (assuming vapour treatment is not required).



Once in place, a cap and containment system could aid application of future treatment technologies by mitigating possible risks associated with potential source mobilisation.

Disadvantages of capping and containment of mercury source areas at the site include:

Access issues including concrete foundations, debris, overhead services, below ground utilities and restricted work areas would need to be considered in the implementation of the containment remediation option.

Design life is uncertain.

Certain compounds and water quality conditions can affect soil or cement bentonite barriers. The durability and permeability of bentonite may be impacted when exposed to low pH or high concentrations of some volatile organic compounds and inorganic salts. However, effects of these conditions can be mitigated by conducting treatability tests and tailoring the backfill mix to site conditions. It is noted that slurry containment walls have been used extensively at coastal contaminated sites with groundwater of high salinity and various organic contaminants (e.g. Ullrich et al., 2007; Ryan and Spaulding, 2007).

Mercury may eventually diffuse through the cut-off wall, though this would be over a very long timeframe and likely represent a small mass flux. This can be mitigated with a contingency of wall replacement if required.

This approach does not involve treatment, therefore mercury remains on site, however, potential risks posed by the mercury are addressed.

Long-term inspection, maintenance and monitoring is required and the site must be amenable to these requirements.

Institutional controls (e.g. site management plan) are required with possible restrictions for certain future uses and activities.

Implementation

Preliminary feasibility studies assessing geological and geotechnical information to aid with constructability assessment and design of a slurry or CSM cut-off wall remediation option at the site have been conducted by Golder on behalf of Orica in 2011. Preliminary findings suggest that installation of a soil-bentonite or cement-bentonite slurry or CSM cut-off wall to bedrock around the perimeter of Block G is technically feasible. Site geological conditions of unconsolidated sands with bedrock at depths of up to 25 m bgs is suited to conventional trench excavation techniques.

A containment cut-off wall could potentially be installed without demolition of the TECE building currently constructed over Block G. The cut-off wall could be installed around the outer perimeter of the TECE. Avoiding disturbance and handling of soil from the source area minimises exposure risks to workers.

A minor quantity of excess material (caused by replacement with bentonite grout) which may be impacted by mercury would be generated. The volume of excess soil would vary depending on the containment wall technology used, but would range from minimal volume to 20 % of the cut-off wall volume which equates to a maximum volume of waste spoil of approximately 1,200 m3. This would either be placed within the containment area and capped on site or require off-site disposal at an appropriate facility (e.g. monocell).

Caps are commonly installed at landfill sites. Construction of a cap at the site would be undertaken in a similar manner. Above grade concrete foundations and structures within the cap area may have to be demolished to ensure future cap integrity and the cap would have to be designed with consideration of future site use, likely as hardstand for site material storage. The TECE building would require demolition to construct a cap. Exposure risks could be mitigated by installing a temporary cover (e.g. plastic sheeting) over the source area prior to the TECE being demolished.



8.1.2.2 Effectiveness Containment of mercury source areas at the site is expected to provide long-term protection to human health and the environment provided ongoing management measures are implemented. The benefits of capping and containment of the mercury source area at the site include:

Human health:

Mitigation of unacceptable risks to future site workers by prevention of direct contact with impacted soils and inhalation of impacted dust.

Mitigation of unacceptable risks to site workers by prevention of mercury vapour emissions.

Mitigation of unacceptable risks to site workers by avoidance of disturbing soils in the source area.

A barrier constructed to the ground surface would also act to control potential unacceptable risks associated with lateral vapour migration in the vadose zone.

Environmental:

With source control, modelling predicts that capture of mercury impacted groundwater downgradient of the site will occur at the PCA and SCA more rapidly (within 60 to 100 years) than with no source control. Thus, a cap will control mobilisation of mercury in the vadose zone to groundwater, and a low-permeability cut-off wall installed to bedrock will control the flux of mercury currently in the saturated zone to downgradient groundwater, thereby decreasing the time for aquifer restoration.

The cap will restrict rainfall infiltration into the subsurface, which is a potential mechanism for transport of mercury from shallow soils to groundwater at the site, thereby reducing impacts to downgradient groundwater.

A cap, without cut-off wall would control mobilisation of mercury in the vadose zone to groundwater, thereby decreasing the time for aquifer restoration. Secondary mercury sources, if present, within the saturated zone in source areas would continue to contribute to the groundwater plume. Lateral migration of mercury vapour in the vadose zone and potential lateral migration of elemental mercury would not be controlled.

A cap and cut-off wall installed to the groundwater table would have similar environmental benefits to that of a cap, however, lateral vapour migration in the vadose zone and potential lateral migration of elemental mercury would be controlled.

A low permeability barrier installed around the perimeter of Block G would prevent impacts to the down gradient environment by significantly reducing dissolution of secondary mercury sources in the saturated zone to groundwater.

The limitations of capping and containment of mercury source area at the site include:

Mercury remains on site and there is no reduction of toxicity or mass of mercury. This represents a potential risk should containment fail.

Subchronic exposures of future site workers to mercury vapours and direct contact with impacted soils during intrusive maintenance (beneath the cap) would need to be addressed. These activities, expected to be rare (if any) and of limited duration, would require ongoing management. Golder understands that FCAP site activities and associated risks to workers are currently managed under a site management plan.

Construction of the cap and cut-off wall may increase the short-term potential for direct exposure of construction workers to impacted soils. This could be mitigated by installing the cut-off wall around the outer perimeter of the TECE (i.e., outside the known source area), and by installing a temporary cover (e.g., plastic sheeting) over the source prior to demolition of the TECE.



Over the long term, diffusion of mercury through the cut-off wall is possible, however, the mass flux of diffusion would be relatively very small compared to the current advective flux. This could also be mitigated by a contingency of wall replacement if required.

Mercury present in shallow soils or saturated zone outside the area of containment will not be affected.

8.1.2.3 Sustainability An objective of the preferred remediation option should be a net benefit to the environment and community by achieving a balance between environmental, social and economic factors. This should include consideration of impacts on other segments of the environment, energy consumption, consumption of other resources, greenhouse gas emissions and other stressors to the ecology or community.

Capping and hydraulically containing mercury sources has minimal energy and resource consumption compared to the thermal treatment options. Significantly less waste than generated by excavation and disposal is required to be managed. The need for expensive vapour and water treatment systems during implementation, as required by thermal treatment, is negated. Some very limited vapour treatment might be required to manage sub-cap vapour accumulation.

Capping and hydraulically containing the mercury sources retains the legacy issue on site and does not move it elsewhere. Long term groundwater and vapour monitoring programs are expected to continue.

On the basis that operation of three heavy equipment units (e.g. excavators, crane and loader) would be required for installation of the cut-off wall and cap at the FCAP, and assuming a fuel usage of 100 litres diesel per day per equipment unit, the total fuel consumed over the course of the program (approximately three months) would be in the order of 25,000 litres. Additional fuel consumption for transport of 1,200 tonnes of waste to the monocell would equate to approximately 8,000 litres.

The “carbon footprint” of cap and containment is estimated to be in the order of 290 tonnes of CO2 based on the assumption that processes considered were limited to fuel consumption for heavy equipment required for installation of the cutoff wall and transport of the minor excess spoil to a monocell.

8.1.2.4 Protection of the Environment The HHERA concluded that there were no unacceptable risks to the environment associated with mercury in groundwater downgradient of the site. However, fate and transport modelling (URS, 2008; Laase, 2008) indicates that without control of sources to groundwater, mercury impacted groundwater will continue to migrate towards the southwest. With continuing operation of the GTP system, mercury impacted groundwater will be intercepted by PCA and SCA containment lines within 5 to 100 years (depending on attenuation rates).

Environmental considerations during implementation of the remediation option include:

Containment remediation would minimise disturbance of mercury in the subsurface, and potential mobilisation of mercury prills, relative to more active remediation options.

A low permeability barrier (cut-off wall) will change the groundwater flow regime, although considering the high permeability of the aquifer, potential changes are likely to be localised. Changes in local groundwater flow directions could influence migration of constituents (if present) in groundwater outside the barrier perimeter.

Excavated soil from the trench will be mixed with bentonite and/or cement and reinstated. However, excess excavated soil will require management. The quantity of excess soil may vary substantially depending on the specific cut-off wall construction method employed.

Mercury would remain on the site and would require future management. This is common to similar installations, and at the Botany site future management and monitoring for environmental issues (groundwater) is ongoing. Orica currently owns all the affected land and is in a position to perform the required activities over the long term.



8.1.2.5 Cost Assessment of relative costs for each of the four options is presented in Appendix A.



9.0 REMEDIATION OPTIONS ASSESSMENT This section presents the criteria against which the technologies are to be assessed. It provides a qualitative evaluation of the technologies and presents two alternate ranking methodologies.

9.1 Assessment Criteria Remediation options have been evaluated based on consideration of the following criteria:

Feasibility (Technical) – Considers the degree of difficulty for implementation, operation and maintenance of the remediation option within the context of the site location, infrastructure and facilities, hydrogeological setting and nature of the contaminant. Also considered are the availability of equipment and technical expertise. Effectiveness – An overall assessment of whether the technology can meet remediation objectives, including mitigating human health and environmental risks.

Time Requirements (Implementation) – Presents an indication of the relative duration for full scale implementation of the technology. This includes time required for investigative works to address data gaps and pilot phase testing prior to full-scale application. It does not consider additional time that may be required for planning and permitting.

Time Requirements (Treatment) – Presents an indication of time required to meet the remediation objective, from commencement to cessation of operation.

Financial (Capital) – Includes a qualitative estimate of relative capital (short term) costs. Relative cost has been estimated from available background, supporting documentation and industry experience. Some adjustments have been made for scale and for fluctuations in the Consumer Price Index, but not for changes in commercial/market rates. (It is noted actual costs may vary significantly.)

Financial (O&M) – Includes a qualitative estimate of operations and maintenance expenditure. Relative cost has been estimated considering industry experience. Some adjustments have been made for scale and for fluctuations in the Consumer Price Index, but not for changes in commercial/market rates. (It is noted actual costs may vary significantly.)

Sustainability – An objective of the preferred remediation option should be a net environmental benefit. The sustainability assessment considers impacts on other segments of the environment including energy consumption, resource consumption, waste minimisation and the objectives of minimising carbon emissions and conserving fossil fuels.

Protection of the Environment – This considers potential risks to the environment associated with performing the remediation activities. Includes consideration of short term risks during implementation of the remediation action and longer term risks after implementation.

The following criteria are assessed separately and in general terms:

Feasibility (Institutional) – Considers planning and permitting requirements which may be required by the NSW OEH (EPA and NSW Office of Water), the Accredited Site Auditor, Botany City Council, NSW Department of Planning and Infrastructure and other stakeholders.

Stakeholder (Regulator and Community) Acceptance – Considers stakeholder perception of the remediation approach and the potential response of the community. Consideration has been given to the NSW OEH (EPA and NSW Office of Water), the NSW EPA Accredited Site Auditor, and the community at large (both local and peripheral).

9.2 Evaluation 9.2.1 Technical Feasibility Excavation and off-site disposal of impacted materials is considered a technically feasible option since it is a commonly applied soil remediation technique and uses readily available equipment and technical expertise.



Furthermore, the TECE is already present at the site and an off-site disposal facility (monocell) is understood to be currently available. However, as discussed in Section 6.2.1, the logistics of managing excavated soils within the TECE, as well as transporting soils in lined and sealed skips through the loading bay, would likely be difficult, time consuming and require significant planning and oversight. Excavation of a portion of mercury impacted materials at the site has already been conducted during implementation of the former RAP.

Incorporation of solidification and stabilisation prior to disposal is considered less technically feasible due to uncertainty in effectiveness and long term stability of treated material, though treatability studies may address these uncertainties.

Design and installation of a cap and containment wall is also considered technically feasible since these are technologies commonly applied to landfills and contaminated sites and use readily available expertise, equipment and materials. Integration of a cap and vapour barrier with a containment wall is less commonly applied, and may present greater technical difficulties than cap and/or containment alone.

ESTD is considered technically feasible though has added complexity compared to the excavation and disposal option due to need for procurement, commissioning pre-treatment processing and operation of the thermal treatment plant. It is noted that while the understanding of ESTD by local technology providers has improved with several thermal treatment projects for organic contaminants being undertaken in NSW in recent years, much of this experience is unlikely to be relevant to mercury. Equipment and technical expertise may not be locally available and may have to be imported from overseas. It is expected the greatest technical difficulties would be associated with recovery of mercury and treatment of off-gas.

Within the required timeframe for the project, ISTD is considered to be effectively infeasible as commercial implementation has not been demonstrated at full scale and accordingly there is a significant uncertainty in performance. Equipment and technical expertise is not locally available, would have to be imported from overseas and developed locally. It is noted that assessment methodologies that use ‘Threshold’ ranking categories (refer to Section 9.3 would generally reject technologies that, as is the case with ISTD, have not been demonstrated as being technically feasible or would have a lengthy and challenging development requirement prior to full-scale implementation. However, for consistency with the Management Order, this technology has been retained through the ranking procedures outlined below.

9.2.2 Effectiveness Implementation of the presented remediation options will likely provide long-term protection to human health and benefits to the environment, including:

Human Health:

Direct Contact

Source removal (followed by off-site disposal or treatment using ESTD) would be the most effective means of ensuring mitigation of unacceptable risks to site workers by prevention of direct contact with impacted soils and inhalation of impacted dust. ISTD will potentially have the same benefit, though the certainty of achieving this outcome is less. Capping will also have the same benefit, though because mercury impacted materials will remain in place, management measures and institutional controls will be required for maintenance of the cap and to control ongoing site activities.

Vapour Inhalation

Removal of mercury impacted materials (at concentrations exceeding the RBC) either via excavation and disposal or treatment using ISTD, will provide mitigation of unacceptable risks to site workers by minimising mercury vapour emissions. Excavation with disposal or treatment using ESTD will provide the most certainty in achieving this outcome for the required extent of remediation. However, residual mercury will likely remain at the site, which may require ongoing management. Residual mercury (not accessible by excavation) could result in recurrence of vapour



risks in the longer term. Capping would have similar benefits, although a containment wall at least in the vadose zone (i.e. above the water table) may be required to mitigate the potential for lateral vapour migration. Application of ISTD to depth or capping combined with a containment wall, would provide the greatest benefits to mitigating vapour risks provided ongoing management for maintenance of the cap and control of ongoing site activities are implemented.

During remediation, thermal treatment options represent a greater risk to surrounding human health receptors (workers and residents) due to the higher potential for mercury vapour emissions from the thermal treatment unit. (Although mitigation will reduce the probability of emissions external to the site.)

Environmental:

Since mercury is removed from shallow soils through excavation and ISTD remediation options, rainwater infiltration into the subsurface will no longer act as a mechanism for mercury impacts to infiltrate groundwater in the treated area. However, it is unlikely the full extent of the contamination will be addressed using these approaches and mercury remaining below the depth of remediation (i.e. inaccessible, marginal or recalcitrant areas of mercury) may still present a low level source to groundwater if mobilised by infiltration, likely requiring long term monitoring and management.

Capping will provide greater potential benefit to the environment since infiltration is effectively prevented in the remediation area, however, mercury present in the saturated zone will remain a potential source to groundwater. The potential for lateral vapour diffusion would also remain.

Capping combined with a containment wall would overcome these issues as the source is effectively contained and fully separated from the saturated formation and ongoing infiltration of rainwater is prevented.

While a shallow implementation of ISTD would remove mercury from the unsaturated and potentially the upper portions of the saturated zones, a significant risk of lateral and vertical (and ultimately downgradient) migration of ‘liberated’ mercury would remain. Because of this risk, implementation of ISTD to depth and in combination with a containment wall would likely be required.

9.2.3 Implementation and Treatment Time The Management Order identifies that remediation objectives should be met by the end of 2014. Based on Orica’s experience on other ESTD projects, a lead time (including planning, permitting, design and construction) in the order of five years would likely be required for ESTD. A similar lead time for ISTD may also be expected.

Based on information on thermal treatment projects in the literature (Sections 6.5 and 0) treatment time would be in the order of six months for ESTD and one year for ISTD. Even with a more optimistic lead time of three years, the completion date of thermal remediation options would be approximately 2016 to 2017.

Cap and containment approaches would require feasibility studies (some of which have already been conducted by Orica) prior to design and implementation. However, given that these technologies are well understood and use commercially available equipment, a lead time in the order of one to two years (assuming planning and permitting time of up to one year) and implementation time in the order of three to six months would be expected. Thus, completion of remediation by cap and containment could potentially be achieved in the required timeframe (by the end of 2014).

Excavation and disposal would involve a relatively short lead time (of the order of six months) since many of the planning and management measures (e.g. the current availability of the monocell and TECE at the site) required were also required for the previous remediation program. Stabilisation would require additional lead time in the order of six months to conduct treatability studies and in the order of one year for planning and permitting (e.g. obtaining an immobilisation exemption for mercury stabilised material). Treatment time would



be in the order of six months. Thus, completion of remediation by excavation and disposal could potentially be achieved by the end of 2014, though incorporation of stabilisation would require additional time.

9.2.4 Financial An assessment of relative costs for each of the four remediation options is presented in Appendix A and indicates that ISTD treatment to depth has the highest cost. Source removal with off-site disposal with or without stabilisation, and ESTD options, also have high capital costs. Cap and containment options have the lowest capital costs.

The assessment of relative costs for each of the four remediation options presented in Appendix A indicates that ongoing O&M costs represent a small portion of total lifecycle costs for all options. Total O&M costs for disposal and thermal treatment options are less than 2 % of total lifecycle costs, whereas total O&M costs represent less than 4 % of total lifecycle costs for cap and containment options.

9.2.5 Sustainability Mercury cannot be degraded or destroyed, thus, the remediation options do not change the mass of mercury associated with the site, but either involve transferring the mercury from the site to a location or form where it can be managed, or controlling the exposure pathways to human and environmental receptors. However, implementing the remediation options will impact on other segments of the environment due to resource use, energy consumption, carbon emissions, fossil fuel use and waste generation.

Waste Generation

Disposal options simply result in transfer of mercury from the site, to a monocell where the risks associated with mercury impacted soils can be managed appropriately. Excavation and disposal does not result in a decrease in volume of mercury impacted materials. Stabilisation would result in an increase in volume of waste requiring disposal (although this may be as Restricted Waste rather than Hazardous Waste).

Thermal treatment options result in transfer of mercury from impacted soils to the vapour phase, from which it is captured as either elemental mercury or concentrated in sorption media. While there is reuse potential for captured elemental mercury, sorption media will require disposal at a monocell. However, the volume of material requiring disposal will be significantly less than for the excavation and disposal option.

Installation of a cap and vapour barrier will result in minimal waste generation, though mercury vapours may potentially need management. Construction of a containment wall will result in a relatively small volume (less than 5 % of that for excavation/disposal) of excess material requiring disposal.

Fuel Use and Energy

Excavation and disposal is energy intensive primarily due to fuel use for heavy equipment and transport. This is compounded by the need to import clean fill to the site for reinstatement in the excavation.

Thermal treatment options are the most energy intensive options due to significant power usage. Ex situ thermal treatment also relies on fuel use for heavy equipment and pre-treatment processing.

Cap and containment options represent the least energy intensive options.

Greenhouse Gas Emissions

Thermal treatment options are associated with the highest greenhouse gas emissions. Cap and containment options generate the least greenhouse gas emissions.

Consumables

Off-site disposal requires clean fill to be imported to the site for reinstatement in the excavation. Landfill facilities are also a resource; off-site disposal consumes some of that non-renewable resource. Stabilisation will require use of significant volumes of binding and stabilising chemical agents (e.g. sulphide compounds and Portland cement). Thermal treatment options will require sorptive media (e.g. activated carbon) for vapour treatment, and ISTD will require use of numerous wells and thermocouples which will require disposal. Capping will require a relatively small mass of geosynthetic membranes and natural materials (e.g.



sand and gravel), while containment walls are generally constructed from natural materials (e.g. bentonite, a natural clay).

9.2.6 Protection of the Environment

Short Term Effects

The main short-term environmental considerations during implementation of the remediation options include:

Disturbance of mercury in the subsurface and potential mobilisation of mercury prills, due to activities such as excavation and demolition. Thus, remediation options which disturb the most heavily impacted materials (i.e. excavation and installation of wells for ISTD) have the greatest potential for further mobilisation of elemental mercury and associated environmental risk during implementation.

Potential for formation of a mercury condensation front at the periphery of the heated area with ISTD and increased mobility of elemental mercury within the subsurface would significantly increase the risk of lateral and vertical movement of elemental mercury. For this reason, application of ISTD to bedrock and installation of a containment wall would be required to mitigate these risks.

Increased risk of mercury vapour discharge whether from the subsurface if the vapour capture system (ISTD) or barrier is not designed correctly, or vapour treatment system (ESTD and excavation/disposal options).

Environmental risks associated with handling and off-site transport of mercury impacted materials are highest for excavation options. ESTD and solidification and stabilisation options have decreased risk associated with transport of mercury impacted good due to reduced volume (ESTD) or potentially lower vapour emissions and waste classification (solidification and stabilisation). Capping and containment have the least risk associated with transport of contaminated materials.

Environmental risks associated with management of elemental mercury and sorbed mercury captured in the vapour treatment system for thermal treatment options.

Changes in local groundwater flow directions caused by a cut-off wall could influence migration of any constituents present in groundwater outside the barrier perimeter.

In summary, although administrative and engineering controls can be implemented to mitigate risks associated with many of these considerations (e.g. vapour treatment, conducting treatability trials to ascertain optimal treatment parameters), the capping option represents the least risk to the environment in the short term as it involves relatively less site disturbance, minimises the risk of further mobilising mercury within the subsurface, minimises handling of mercury impacted materials and does not require vapour treatment as part of remediation implementation. Containment is similar, but involves additional site disturbance and potentially handling of relatively small amounts of mercury impacted materials.

Long-Term Considerations

All options result in benefits to the environment due to removal or isolation of a significant portion of mercury at the FCAP, thus controlling further impacts to groundwater and vapour emissions to atmosphere. Treatment or containment of the source area to bedrock would provide additional benefit by controlling migration of mercury already present in the saturated zone of the source area in groundwater. However, it is important to note that given the uncertainty in distribution of mercury at the FCAP and practicability of remediation options, long-term management at the site will likely be required for all options.

Mercury present in a containment cell at the site represents a greater potential long term environmental risk than other options which result in removal of a substantial amount of mercury. However, with disposal and thermal treatment options the long term environmental risk is not eliminated but transferred to the monocell disposal facility. Prolonged monitoring and potential management of vapour may be required for a cap and vapour barrier system.



9.2.7 Institutional Feasibility Institutional implementability considers planning and permitting requirements which may be required by the NSW OEH (EPA and NSW Office of Water), the Accredited Site Auditor, Botany City Council, NSW Department of Planning and Infrastructure and other stakeholders. Although the regulatory and planning requirements for implementation of the remediation options have not been ascertained at this stage, it is likely that each remediation option will necessitate similar institutional processes, although the level of effort required may vary. Nevertheless, ongoing management of residual mercury at the FCAP will be required for all remediation options.

Accordingly, this criterion is kept somewhat separate from the numerical rankings and is considered a ‘modifying’ criterion (see Section 9.3.2).

9.2.8 Stakeholder Acceptance

9.2.8.1 Community Consultation A range of community involvement activities in relation to remediation activities at the FCAP have been conducted to solicit community input and to ensure that the public remains informed about site activities throughout the site remediation process. Outreach activities have included public notices and communication via the Community Liaison Committee (CLC) on cleanup progress and activities.

During the course of the soil washing programme the CLC was updated on progress and performance during routine CLC meetings.

On 21 November 2011, Orica held an extraordinary meeting with the CLC to inform them of the decision to suspend the soil washing project. In the meeting Orica representatives explained the reasons behind its suspension, set out an interim program for management of ongoing emissions and outlined their plan for selection of a new technology.

On 13 December 2011, as part of a general CLC meeting, Orica hosted a workshop aimed at presenting and discussing the relative merits of two alternative remediation options to the CLC. These options included excavation and disposal, and on-site containment. Peter Nadebaum, an independent expert, contributed to the workshop by presenting a matrix of considerations for the options. The matrix was used to capture the questions and feedback from the community and included consideration of air quality, groundwater, surface water, human health, social, transport and duration, and documented the CLC’s queries and independent expert’s responses.

The queries and concerns were mainly focussed on:

Potential for escape of vapour emissions;

Potential for migration into groundwater should a containment option be selected or should ‘hotspots’ of contamination remain after excavation and disposal;

Potential for mercury to reach stormwater bodies;

Exposure of the public and workers to vapours both in the TECE during excavation works, as well as at the receiving landfill (monocell);

Impacts to local amenity and environment associated with transport of materials to a landfill;

Perception of concern relating to the effectiveness of a containment approach;

Risks to the community around the receiving landfill;

Accidental ‘losses’ during transport (such as crashes) and increased traffic volumes; and

Duration of the works.



A further meeting was held on 20 March 2012. Orica presented a summary of the content and implications of the Management Order, which was issued on 9 January 2012. The timeframes required in the Management Order were outlined, including the proposed dates for ongoing CLC meetings.

At this meeting it was minuted that the matrix of considerations prepared during the previous meeting had been circulated in draft form to the CLC in December 2011 but that no responses from the community had yet been received. Discussion in this meeting was largely related to the thermal options included in the Management Order. Orica indicated that the matrix had been forward to Kendrick Jaglal, the appointed Independent Expert from the United States and also indicated that any further comments received from the CLC would be taken into consideration during the development of the remedial options appraisal.

Orica has indicated that, to date, one public respondent had registered feedback via email on 4 April 2012. The content of the feedback included:

Consideration that the potential short term risks to the community and to workers associated with ‘experimental’ thermal remediation should effectively rule out this option;

Consideration that application of thermal remediation to another parts of the BIP site had resulted in breaches of licence conditions for vapour emissions;

Concern over short term dust and vapour risks during source removal;

Consideration that a site containment approach results in retention of legacy issues associated with residual mercury and results in complications for future change of land use; and

Concern that the community liaison process was overly reliant on the CLC specifically and did not cater for the wider community.

It is understood the liaison process will continue after submission of this document and will include an invitation by Orica to the community to provide feedback. Given the complexity involved in interpreting the community’s perception of risk, this criterion (stakeholder acceptance) is kept somewhat separate from the ranking process and is considered a ‘modifying’ (qualitative) criterion.

Accordingly, it is noted that in general, remediation approaches that would achieve removal of mercury from the site would appear to be deemed more acceptable to the community than those which leave mercury impacts at the site. However, the issues associated with dust and vapour releases also appear to be very significant factors in the public’s perception of risks.

The materials collated to date suggest key consideration is also being given to associated environmental (e.g. potential risks associated with capture and treatment of mercury vapours), sustainability (e.g. increased greenhouse gas emissions) and social (e.g. increase in truck movements) issues.

9.2.8.2 Regulator Based on experience of other ESTD projects by Orica, a lead time of the order of five years may be required for planning approval. A similar lead time for ISTD may be expected. This does not meet EPA expectations as presented in the Management Order, and is unlikely to meet expectations of the local community.

9.3 Ranking Several remediation option ranking methods have been developed across the industry in recent years and are subject to continuous change and development. Where quantitative assessment is applied, numerical methods can include application of weighted scoring systems or relative ranking systems.

In this section, two such methodologies (Methods A and B respectively) are applied separately. The outcomes are then compared and discussed in the following sections.



9.3.1 Method A

9.3.1.1 Approach Ranking of shortlisted technologies was undertaken against the criteria presented above and quantified using a weighted scale as detailed in Table 3.

Criteria ranking factors are weighted, to consider the relative importance of certain factors over others. For example technical feasibility and effectiveness of a remediation option is considered more important than the level of effort required for institutional controls (e.g. planning and permitting). It is recognised that the weighting of criteria is subjective and may vary according to people’s points of view. The weighting assigned below attempts to reflect a balanced approach.

Table 3: Ranking Criteria Descriptors

Criteria Rankings Criteria

Weighting (A)

Ranking Factor

(B)

Weighted Ranking Factor (A x B)

Feasibility (Technical)

Strong Technical Feasibility

15%

10 15

Moderate Technical Feasibility 5 7.5

To be validated (or not favourable) 1 1

Effectiveness (Human Health)

Highly effective

20%

10 20

Moderately effective 5 10

Poorly Effective 1 1

Effectiveness (Environmental)

Highly effective

15%

10 15

Moderately effective 5 7.5

Poorly Effective 1 1

Time Requirement (Implementation)

Short time for implementation (prior to end-2012)

10%

10 10

Moderate time for implementation (end-2013) 5 5

Long time for implementation (after end-2014) 1 1

Time Requirements (Treatment)

Short time for treatment (<6 months)

5%

10 5

Moderate time for treatment (1 year) 5 2.5

Long time for treatment (>2 years) 1 0.5

Financial (Capital) (Indicative only)

Low Capital Costs (<$5M)

10%

10 10

Moderate Capital Costs ($20M) 5 5

High Capital Costs (>$40M) 1 1

Financial (O&M) (Indicative only)

Low O&M Costs (<$50k/annum)

5%

10 5

Moderate O&M Costs ($100k/annum 5 2.5

High O&M Costs (>$150k/annum) 1 0.5

Sustainability

High Sustainability

10%

10 10

Moderate Sustainability 5 5

Low Sustainability 1 1

Protection of the Environment

High Environmental Benefit

10%

10 10

Moderate Environmental Benefit 5 5

Environmental Risk 1 1



9.3.1.2 Outcome The remediation options have been ranked according to the criteria outlined in Section 9.1 as presented in Table 4.

Table 4: Remediation Option Ranking – Method A

Ranking Criteria

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Feasibility (Technical) 13 10 9 4 4 13 13 15

Effectiveness (Human Health) 16 16 15 9 16 16 18 20

Effectiveness (Environmental) 10 10 10 2 11 11 13 15

Time (Implementation) 7 6 1 1 1 5 5 10

Time (Treatment) 5 5 5 3 2 5 5 5

Financial (Capital) 1 1 1 6 1 10 5 10

Financial (O&M) 5 5 5 5 4 2 3 5

Sustainability 2 2 2 3 1 9 8 10

Protection of the Environment 6 6 6 2 6 7 8 10

Rank (Total Score) 65 61 54 35 46 78 78 100

Installation of an on-site cap and vapour barrier, with or without a containment wall around the perimeter of Block G, is the highest ranked remediation option based on Method A ranking. This is primarily due to the lower capital cost, short implementation time and more sustainable attributes of this option when compared to the thermal, excavation and off-site disposal options.

9.3.2 Method B

9.3.2.1 Approach This approach is based on a USEPA developed methodology for use in feasibility studies at Superfund sites in the United States (USEPA, 1988). The USEPA method is a largely qualitative process whereby remedial alternatives are evaluated against three categories of criteria termed Threshold, Balancing and Modifying. The threshold criteria must be met while the balancing criteria provide the basis for the relative evaluation of each alternative. The modifying criteria are applied to the remedy after it is selected based on the criteria in the first two categories.

The following table summarises the three criteria, the common attributes of each and the selected criteria for this project.

Table 5: Criteria Categories Summary

Category Attributes Criteria

Threshold

Overall protection of human health and the environment; Compliance with chemical target concentrations (i.e. RBC)

Feasibility (Technical)

Effectiveness (Human Health)

Effectiveness (Environmental)

Balancing Long-term effectiveness and permanence Reduction of toxicity, mobility or volume through

Feasibility (Institutional Control)



treatment Short-term effectiveness Implementability Cost

Financial (Capital)

Financial (O & M)

Sustainability

Protection of the Environment

Time (Implementation)

Time (Treatment)

Modifying Regulator acceptance Community acceptance

Stakeholder Acceptance

In adopting this approach the ranking criteria have been categorised under the three identified headings, however, the approach has been modified to include a numerical ranking (1 to 7) against each category, where 1 is the least favorable and 7 the most. To provide an overall relative ranking, the cumulative ranking of threshold criteria are used to weight (by multiplication) the cumulative ranking of balancing criteria.

9.3.2.2 Outcome The remediation options have been ranked according to the criteria outlined in Section 9.1 as presented in Table 6.

Table 6: Remediation Option Ranking – Method B

Ranking Criteria

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Feasibility (Technical) 7 4 3 2 1 6 5

Effectiveness (Human Health) 5 4 3 2 1 6 7

Effectiveness (Environmental) 3 4 2 1 6 5 7

Subtotal (A) 15 12 8 5 8 17 19

Balancing Criteria

Financial (Capital) 3 2 4 5 1 7 6

Financial (O&M) 7 6 4 5 3 1 2

Sustainability 3 4 5 2 1 6 7

Protection of the Environment 4 5 3 1 2 6 7

Time (Implementation) 7 6 3 2 1 4 5

Time (Treatment) 5 4 3 2 1 7 6

Subtotal (B) 29 27 22 17 9 31 33

Overall Rank (A) x (B) 435 324 176 85 72 527 627



The outcome of ranking Method B has indicated the on-site containment options are more favourable, primarily based on considerations of feasibility, effectiveness, sustainability and environmental factors.

Thus the outcome of Method B is similar to the outcome of Method A, although the determining factors are somewhat different.



10.0 PREFERRED TECHNOLOGY IDENTIFICATION Of the four options identified in the Management Order, the on-site containment option, incorporating capping, vapour barrier and containment wall at Block G is considered the most appropriate remediation approach for the Orica FCAP site. This is based on the evaluation and assessment presented herein, which included a review of the remediation technology status, identification of relevant case studies and a comprehensive evaluation of site-specific considerations including:

Technical feasibility of implementing the remediation options.

The effectiveness in meeting the remediation objectives.

Sustainability of the options in terms of resource consumption, energy use, ‘carbon footprint’ and waste generation.

Potential detrimental impacts to human health and the environment during implementation of the options.

Cost of implementing the remediation options.

These criteria were further assessed using established ranking methods. Stakeholder acceptance, including community consultation, and the regulatory and planning requirements to implement the remediation option, were also considered.

The remediation options considered would all have a residual legacy of mercury in soil and groundwater, and require ongoing management of the site.

On-site containment is considered the most appropriate remedial approach for the Orica FCAP site since it is based on technologies that are fully developed and readily implementable in this country, is considered feasible for application at the site and could be applied within the timeframe envisaged in the Management Order (subject to detailed design and approvals process). On-site containment with a cap and full-depth cut-off wall can isolate the source material beneath Block G, thereby achieving the remediation objectives relating to:

Reducing risks to human health and the environment from mercury to the extent practicable.

Reducing ongoing impacts to groundwater to the extent practicable

During remediation, this on-site containment option is considered to present the lowest risk of dispersal or emission of mercury to the surrounding environment and the lowest risk to human health (residents and workers) as it minimises disturbance of, and need to transport, mercury impacted materials. On-site containment is the most sustainable approach in that it will generate little waste, will use relatively few resources and has the lowest carbon footprint.



11.0 REFERENCES ANZECC/NHMRC (1992). Guidelines for the Australian and New Zealand Assessment and Management of Contaminated Sites. Australian and New Zealand Environment and Conservation Council (ANZECC) and National Health and Medical Research Council (NHMRC).ASSMAC (1998) Acid Sulfate Soil Manual. Acid Sulfate Soil Management Advisory Council. http://www.asris.csiro.au

Baker, LaChance, Heron. (2006). In-Pile Thermal Desorption Of PAHs, PCBs And Dioxins/Furans In Soil And Sediment International Symposium and Exhibition on the Redevelopment of Manufactured Gas Plant Sites (MGP2006), Reading, England, April 4-6, 2006

Bowerman, Adams, Kalb, Wan, LeVier (2003). Using the Sulfur Polymer Stabilization/Solidification Process to Treat Residual Mercury Wastes from Gold Mining Operations Society of Mining Engineers Conference Cincinnati, OH, February 24-26, 2003

Busto, Cabrera, Tack, Verloo (2011) Potential of thermal treatment for decontamination of mercury containing wastes from chlor-alkali industry. Journal of Hazardous Materials 186 114–118

Chang, Yen (2006) On-site mercury-contaminated soils remediation by using thermal desorption technology Journal of Hazardous Materials B128 208–217

Comuzzi, Lesa, Aneggi, Dolcetti, Goi (2011) Salt-assisted thermal desorption of mercury from contaminated dredging sludge Journal of Hazardous Materials. 193,177-182

DCCEE (2010). National Greenhouse Accounts (NGA) Factors. Department of Climate Change and Energy Efficiency. July 2010

DEC, NSW (2006). Guidelines for the NSW Site Auditor Scheme (2nd Edition).

DECC, NSW (2009). Waste Classification Guidelines. Part 1: Classifying Waste (the Waste Guidelines)

Entech 2007. Entech Industries, Chemical Immobilisation Treatment, Report for Orica’s Yarraville Mercury Contaminated Soil under Cell Block Building, Orica Pilot Scale Trial. March 2007

Golder (2011). Former Chloralkali Plant (FCAP), Orica Botany, Proposed Remediation Strategy. Golder Associates Pty Ltd, 117623084-001-L-Rev1, dated 22 December 2011.

Hinton, Veiga (2001). Mercury Contaminated Sites: A Review of Remedial Solutions Proc. In. NIMD (National Institute for Minamata Disease) Forum 2001. Mar. 19-20, 2001, Minamata, Japan.

Hovsepyan, Bonzongo, (2009), Aluminium drinking water treatment residuals as sorbent for mercury: Implications for soil remediation J. Haz. Mat., 164, 73-80.

Kunkel, Seibert, Elliott, Kelley, Katz, Pope (2006). Remediation of Elemental Mercury Using in Situ Thermal Desorption (ISTD) Environ. Sci. Technol. 2006, 40, 2384-2389

Laase (2010) Contaminant Fate and Transport Modelling. A.D.Lasse Hydrologic Consulting, February 2010

Manchon-Vizuete, Macias-Garcia, Nadal Gisbert,(2005). Adsorption of mercury by carbonaceous adsorbents prepared from rubber of tyre wastes, J. Haz. Mat., B119, 231-238.

Mavesa Environment (2012). Personal communication via email with Maxence Vermersch, 2 April 2012.

Meng, Hua, Dermatas, Wang, (1998). Immobilization of mercury (II) in contaminated soil with used tire rubber. J. Haz. Mat., 57, 231-241.

Orica (2010) Orica Botany, Mercury Remediation Project – Remediation Technology Assessment for the Remediation of Mercury Contaminated Soils and Concrete, Orica Australia Pty Ltd, 30 June 2010

Orica (2011) Orica Botany, Mercury Remediation Project – Remediation Technology Assessment for the Remediation of Mercury Contaminated Soils and Concrete, Orica Australia Pty Ltd, 22 December 2011



Orica (2012). See site documentation at (accessed 20 February 2012): http://www.oricabotanytransformation.com/index.asp?page=117&project=27

Piao, Bishop, (2006). Stabilization of mercury-containing wastes using sulphide. Env. Pollution, 139, 498-506.

Ryan (1985) Slurry Cutoff Walls: Application in the Control of Hazardous Wastes. In, Hydraulic Barriers in Soil and Rock. ASTM STP 874. American Society for Testing and Materials, 9-23

Ryan (1987) Vertical Barriers in Soil for Pollution Containment. Geotechnical Practice for Waste Disposal, GSP No. 13, Woods, R.D. Ed., American Society of Civil Engineers, Ann Arbor, MI, June 1987.

Ryan, Spaulding (2007). Vertical groundwater barriers for contaminated site reclamation. Proceedings of the 10th Australia New Zealand Conference on Geo-Mechanics, “Common Ground” Brisbane Australia, October 2007

SAVA (2012) http://www.sava-online.com/english/index.html - Instruction sheet No 1. Accessed 9 April 2012.

Seibert (2005). In situ thermal desorption of mercury-contaminated soil: Laboratory-scale and numerical simulation study. M.S. Thesis, University of Texas at Austin, Austin, TX, 2005.

Spaulding (2007). Soil Bentonite Cut-off Walls for Confinement of Existing Landfills: Tempe Tip A Case Study. XVIth Asian Conference, NSW, Australia, February 2007.

Stegemeier, Vinegar (2001) Thermal Conduction Heating For In-Situ Thermal Desorption Of Soils In: Hazardous & Radioactive Waste Treatment Technologies Handbook, Ch. 4.6-1, Oh, Chang H. (Ed.) CRC Press, Boca Raton, Florida

Ullrich, Ilyushchenko, Kamberov, Tanton. (2007) Mercury contamination in the vicinity of a derelict chlor-alkali plant. Part I: Sediment and water contamination of Lake Balkyldak and the River Irtysh. Science of the Total Environment, 381:1–16

URS (2008). Final Report: Human Health and Environmental Risk Assessment, Former Chloralkali Plant, Botany Industrial Park, 21 August 2008.

URS (2010). Remediation Action Plan, Former ChlorAlkali Plant, Orica Botany, NSW, 28 July 2010

USAEC (2006). Remediation Technologies Screening Matrix and Reference Guide 4th Edition. U.S. Army Environmental Center, January 2002. Accessed on 20 February 2012 at http://www.frtr.gov/

USEPA (1988). Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA – Interim Final

USEPA (1997a). Rules of Thumb for Superfund Remedy Selection. Office of Solid Waste and Emergency Response, United State Environment Protection Agency. EPA 540-R-97-013

USEPA (1997b). Technology Alternatives for the Remediation of Soils Contaminated with As, Cd, Cr, Hg, and Pb. Office of Solid Waste and Emergency Response, United State Environment Protection Agency. Engineering Bulletin, EPA/540/S-97/500. August 1997.

USEPA (1998a). Presumptive Remedy for Metals-in-Soil Sites. Office of Solid Waste and Emergency Response, United State Environment Protection Agency. EPA 540-F-98-054

USEPA (1998b). Analysis of Alternatives to Incineration for Mercury Wastes Containing Organics July 6, 1998

USEPA (1998c). On-Site Incineration: Overview of Superfund Operating Experience

USEPA (2004a). Field Evaluation of TerraTherm In Situ Thermal Destruction (ISTD) Treatment of Hexachlorocyclopentadiene, Innovative Technology Evaluation Report July 2004 EPA/540/R-05/007



USEPA (2004b). In Situ Thermal Treatment of Chlorinated Solvents: Fundamentals and Field Applications March 2004 EPA 542-R-04-010

USEPA (2004c). Stabilization of Mercury in Waste Material from the Sulfur Bank Mercury Mine. EPA/540/R-502a, July 2004

USEPA (2005). Economic and Environmental Analysis of Technologies to Treat Mercury and Dispose in a Waste Containment Facility United State Environment Protection Agency. EPA/600/R-05/157. April 2005

USEPA (2007). Treatment Technologies For Mercury in Soil, Waste, and Water, August 2007

Vinegar, Rouffignac, Rosen, Stegemeier, Bonn, Conley, Phillips, Haley and Aldrich, Hirsch, Carl, Steed, Arrington, Brunette, Mueller, Siedhoff (1997) In Situ Thermal Desorption (ISTD) of PCBs HazWaste / World Superfund XVIII. Washington, DC, December, 1997

Xiong, He, Zhao, Barnett. (2009). Immobilization of mercury in sediment using stabilized iron sulphide nanoparticles. Water Research, 43, 5171-5179.

Zhang, J. Bishop P.L. (2002). Stabilization/solidification (S/S) of mercury-containing wastes using reactivated carbon and Portland cement. Journal of Hazardous Materials, B92, 199–212

Zhang, X., Wang, Q., Zhang, S., Sun, X., Zhang, Z (2009). Stabilization/solidification of mercury-contaminated hazardous wastes using thiol-functionlized zeolite and Portland cement. J. Haz. Mat. 168, 1575-1580.

Zhuang, Walsh, Lam, Boulter. (2003). Application of ferric sludge to immobilize leachable mercury in soils and concrete. Environ. Technol. 24(11):1445-53.



12.0 LIMITATIONS This Document has been provided by Golder Associates Pty Ltd (“Golder”) subject to the following limitations:

This Document has been prepared for the particular purpose outlined in Golder’s proposal and no responsibility is accepted for the use of this Document, in whole or in part, in other contexts or for any other purpose.

The scope and the period of Golder’s Services are as described in Golder’s proposal, and are subject to restrictions and limitations. Golder did not perform a complete assessment of all possible conditions or circumstances that may exist at the site referenced in the Document. If a service is not expressly indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any determination has been made by Golder in regards to it.

Conditions may exist which were undetectable given the limited nature of the enquiry Golder was retained to undertake with respect to the site. Variations in conditions may occur between investigatory locations, and there may be special conditions pertaining to the site which have not been revealed by the investigation and which have not therefore been taken into account in the Document. Accordingly, additional studies and actions may be required.

In addition, it is recognised that the passage of time affects the information and assessment provided in this Document. Golder’s opinions are based upon information that existed at the time of the production of the Document. It is understood that the Services provided allowed Golder to form no more than an opinion of the actual conditions of the site at the time the site was visited and cannot be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings, or any laws or regulations.

Any assessments made in this Document are based on the conditions indicated from published sources and the investigation described. No warranty is included, either express or implied, that the actual conditions will conform exactly to the assessments contained in this Document.

Where data supplied by the client or other external sources, including previous site investigation data, have been used, it has been assumed that the information is correct unless otherwise stated. No responsibility is accepted by Golder for incomplete or inaccurate data supplied by others.

Golder may have retained subconsultants affiliated with Golder to provide Services for the benefit of Golder. To the maximum extent allowed by law, the Client acknowledges and agrees it will not have any direct legal recourse to, and waives any claim, demand, or cause of action against, Golder’s affiliated companies, and their employees, officers and directors.

This Document is provided for sole use by the Client and is confidential to it and its professional advisers. No responsibility whatsoever for the contents of this Document will be accepted to any person other than the Client. Any use which a third party makes of this Document, or any reliance on or decisions to be made based on it, is the responsibility of such third parties. Golder accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this Document.



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GOLDER ASSOCIATES PTY LTD

Dr Andrei Woinarski Gavan Butterfield Senior Environmental Engineer Principal Environmental Scientist

GJB/AZW

A.B.N. 64 006 107 857

Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.

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SCALE (at A3)Coordinate System: GDA 1994 MGA Zone 56

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NOTES

COPYRIGHT1. Aerial Photography Copyright NearMap Pty Ltd. Image dated 2011.10.23. Sourced with permission from Nearmap on 2011.11.16. Image Georeferenced by Golder and intended for indicative purposes only. More information can be found here: http://www.nearmap.com/

2. Base map data copyright MapInfo Australia Pty Ltd

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G_TP063.29No

G_TP192.95No

G_TP2710.1No

G_TP28*128No

G_TP24829Yes

G_TP2551.2No

G_TP22615Yes

G_TP132.81No

G_TP147.07No

G_TP2122.7No

G_TP017.97No

G_TP261.76No

G_TP0323.8No

G_TP104.01No

G_TP084.81No

G_TP07417Yes

G_TP0516.6No

G_TP0412.6No

M_TP03226Yes

G_TP173560Yes

G_TP20*8070Yes

G_TP1814500Yes

ORICA FCAP BLOCK G

ORICA AUSTRALIA PTY LTD

PROPOSED REMEDIATION EXTENT - RAP (URS, 2010)

FIGURE 2

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BOTANYHILLSDALE

EAST BOTANY

BANKSMEADOW

EASTGARDENS

File Location: J:\GIS\Jobs\ORICA\ORICA BOTANY\117623084_OricaFCAPContainmentAdvice\Workspaces\117623084_F0004_Figure2.mxd

117623084

GB

16/04/2012FA

LEGEND

#*Previous Soil Assessment Location (URS 2006)

!( Existing Monitoring Well!( Test Pit Locations (URS 2008)

!(Soil Delineation Location (URS 2010)

!(Previous Visual AssessmentLocation (URS 2007)

")Previous Soil Assessment Location (URS 2007)Current Salt Stockpile DrivewayProposed Extent of Remediation

SCALE (at A3)DATUM GDA 94, PROJECTION MGA Zone 56

1:6000 5 10 15 20 252.5 metres

COPYRIGHT1. Aerial Imagery sourced from Google Earth 20102. Base plan derived from URS Final Report. Report Title: Remediation Action Plan Former ChlorAlkali Plant, Orica Botany, NSW dated 28 July 2010.

PROJECT:

CHECKED:

DATE:DRAWN:

¸ ¹

¸ Plant North

Mercury Concentration (mg/kg)0.92Elemental Mercury Identified in the SoilYES/NO

Sample unable to be collected due to auger refusalNS

Inform

ation

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M_TP0710.8No

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G_TP2122.7No

G_TP017.97No

G_TP261.76No

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G_TP0412.6No

M_TP0536.4No

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M_TP0210.5No

M_TP082190Yes

M_TP1179.5Yes

G_TP173560Yes

G_TP20*8070Yes

ORICA FCAP BLOCK G

ORICA AUSTRALIA PTY LTD

PROPOSED REMEDIATION EXTENT - RAP (URS, 2010)

FIGURE 3

!

!

!

!

!

!

BOTANYHILLSDALE

EAST BOTANY

BANKSMEADOW

EASTGARDENS

File Location: J:\GIS\Jobs\ORICA\ORICA BOTANY\117623084_OricaFCAPContainmentAdvice\Workspaces\117623084_F0005_Figure3.mxd

117623084

GB

16/04/2012FA

LEGEND

#*Previous Soil Assessment Location (URS 2006)

!( Existing Monitoring Well!( Test Pit Locations (URS 2008)

!(Soil Delineation Location (URS 2010)

!(Previous Visual AssessmentLocation (URS 2007)

")Previous Soil Assessment Location (URS 2007)Current Salt Stockpile DrivewayProposed Extent of Remediation

SCALE (at A3)DATUM GDA 94, PROJECTION MGA Zone 56

1:6000 5 10 15 20 252.5 metres

COPYRIGHT1. Aerial Imagery sourced from Google Earth 20102. Base plan derived from URS Final Report. Report Title: Remediation Action Plan Former ChlorAlkali Plant, Orica Botany, NSW dated 28 July 2010.

PROJECT:

CHECKED:

DATE:DRAWN:

¸ ¹

¸ Plant North

Mercury Concentration (mg/kg)0.92Elemental Mercury Identified in the SoilYES/NO

Golder Associates Pty Ltd

124 Pacific Highway

St. Leonards, New South Wales 2065

Australia

T: +61 2 9478 3900

117623084 002 r rev2 7000 roar 16042012 final[1]

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