Federal Register of Legislation - Australian Government

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Measures as amended, taking into account amendments up to National Environment Protection (Assessment of Site Contamination) Amendment Measure 2013 (No. 1)
Administered by: Agriculture, Water and the Environment
Registered 03 Jun 2013
Start Date 16 May 2013

Commonwealth Coat of Arms

National Environment Protection (Assessment of Site Contamination) Measure 1999

as amended

made under section 14(1) of the

National Environment Protection Council Act 1994 (Cwlth), the National Environment Protection Council (New South Wales) Act 1995 (NSW), the National Environment Protection Council (Victoria) Act 1995 (Vic), the National Environment Protection Council (Queensland) Act 1994 (Qld), the National Environment Protection Council (Western Australia) Act 1996 (WA), the National Environment Protection Council (South Australia) Act 1995 (SA), the National Environment Protection Council (Tasmania) Act 1995 (Tas), the National Environment Protection Council Act 1994 (ACT) and the National Environment Protection Council (Northern Territory) Act 1994 (NT)

Compilation start date:                      16 May 2013

Includes amendments up to:               National Environment Protection (Assessment of Site Contamination) Amendment Measure 2013 (No. 1)

This compilation has been split into 22 volumes

Volume 1:        sections 1–6, Schedules A and B

Volume 2:       Schedule B1

Volume 3:        Schedule B2

Volume 4:        Schedule B3

Volume 5:        Schedule B4

Volume 6:        Schedule B5a

Volume 6:       Schedule B5a

Volume 7:       Schedule B5b

Volume 8:       Schedule B5c

Volume 9:       Schedule B6

Volume 10:     Schedule B7 - Appendix 1

Volume 11:     Schedule B7 - Appendix 2

Volume 12:     Schedule B7 - Appendix 3

Volume 13:     Schedule B7 - Appendix 4

Volume 14:     Schedule B7 - Appendix 5

Volume 15:     Schedule B7 - Appendix 6

Volume 16:     Schedule B7 - Appendix B

Volume 17:     Schedule B7 - Appendix C

Volume 18:     Schedule B7 - Appendix D

Volume 19:     Schedule B7

Volume 20:     Schedule B8

Volume 21:     Schedule B9

Volume 22:     Endnotes

 

Each volume has its own contents

 

 

 

About this compilation

The compiled instrument

This is a compilation of the National Environment Protection (Assessment of Site Contamination) Measure 1999 as amended and in force on 16 May 2013. It includes any amendment affecting the compiled instrument to that date.

This compilation was prepared on 22 May 2013.

The notes at the end of this compilation (the endnotes) include information about amending Acts and instruments and the amendment history of each amended provision.

Uncommenced provisions and amendments

If a provision of the compiled instrument is affected by an uncommenced amendment, the text of the uncommenced amendment is set out in the endnotes.

Application, saving and transitional provisions for amendments

If the operation of an amendment is affected by an application, saving or transitional provision, the provision is identified in the endnotes.

Modifications

If a provision of the compiled instrument is affected by a textual modification that is in force, the text of the modifying provision is set out in the endnotes.

Provisions ceasing to have effect

If a provision of the compiled instrument has expired or otherwise ceased to have effect in accordance with a provision of the instrument, details of the provision are set out in the endnotes.

 

 

  

  

  


 

 

National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of Site Contamination) Measure 1999 National Environment Protection (Assessment of

Schedule B1

 

 

 

GUIDELINE ON
Investigation Levels
For Soil and Groundwater

 

 

 

 

 

 

 

 

 

 

 

Explanatory note
The following guideline provides general guidance in relation to investigation levels for soil, soil vapour and groundwater in the assessment of site contamination.

This Schedule forms part of the National Environment Protection (Assessment of Site Contamination) Measure 1999 and should be read in conjunction with that document, which includes a policy framework and assessment of site contamination flowchart.

The original Schedule B1 to the National Environment Protection (Assessment of Site Contamination) Measure 1999 has been repealed and replaced by this document.

The National Environment Protection Council (NEPC) acknowledges the contribution of Queensland Department of Environment and Heritage Protection, Commonwealth Department of Health and Ageing, WA Department of Health, WA Department of Environment and Conservation, CRC Care and enHealth to the development of this Schedule.

 

 


Contents
Investigation levels for soil and groundwater
                                                                                       Page

1                             Introduction                                                    1

1.1             Overview                                                                                     1

1.2             Prevention of site contamination                                               1

1.3             Specialised assessments                                                              1

1.4             Acute hazards                                                                             1

1.5             Mineralised areas                                                                        2

2                             Derivation of investigation and screening
levels                                                               
3

2.1             Introduction                                                                                3

2.1.1                Definitions                                                                        3

2.1.2                Inappropriate use of investigation levels and screening
levels                                                                                
4

2.2             Health investigation levels                                                          4

2.3             Interim HILs for volatile organic chlorinated compounds     5

2.4             Health screening levels for petroleum hydrocarbon
compounds                                                                                 
6

2.4.1                Introduction                                                                     6

2.4.2                HSL methodology                                                            6

2.4.3                Sub-slab to indoor air attenuation factor                        7

2.4.4                Petroleum fuel composition                                             8

2.4.5                The Total Recoverable Hydrocarbons analytical
method                                                                             
8

2.4.6                Petroleum hydrocarbon compounds and fractions         9

2.4.7                Soil texture                                                                       9

2.4.8                Land use                                                                         10

2.4.9                Adjusting  HSLs to site-specific circumstances             10

2.4.10             Biodegradation                                                              10

2.4.11             Direct contact HSLs                                                      11

2.4.12             HSLs and multiple-lines-of-evidence approach             11

2.4.13             Limitations of the HSLs                                                 12

2.5             Ecological investigation levels                                                  13

2.5.1                Introduction                                                                   13

2.5.2                EIL methodology                                                           13

2.5.3                Land use                                                                         13

2.5.4                Levels of protection                                                       13

2.5.5                Ecotoxicity data                                                             13

2.5.6                Depth of application                                                       14

2.5.7                Ambient background concentration                              14

2.5.8                Added contaminant limits                                              14

2.5.9                Ageing of contamination and soil properties                15

2.5.10             Determining site-specific EILs                                       15

2.6             Ecological screening levels for petroleum hydrocarbon
compounds                                                                               
16

2.6.1                Introduction                                                                   16

2.6.2                ESL Methodology                                                          16

2.6.3                Depth of application                                                       17

2.6.4                Soil texture                                                                     17

2.6.5                Fresh and aged contamination                                      17

2.7             Sediment quality guidelines                                                     17

2.8             Groundwater investigation levels                                            17

2.9             ‘Management limits’ for petroleum hydrocarbon
compounds                                                                               
18

3                             Application of investigation and screening
levels                                                             
19

3.1             Recommended process for assessment of site
contamination                                                                          
19

3.2             Tier 1 assessment                                                                      19

3.2.1                Comparison with investigation and screening levels    19

3.2.2                Exceedence of Tier 1 investigation and screening
levels                                                                              
20

3.2.3                Procedure if no generic investigation or screening
levels are available                                                       
20

3.3             Specific considerations for  petroleum hydrocarbons           21

3.4             Considerations for ecological assessment                               22

3.4.1                General                                                                          22

3.4.2                Scope of ecological assessment                                      23

3.4.3                Mobility of contaminants                                               23

3.5             Considerations for groundwater assessment                         24

3.6             Aesthetic considerations                                                           24

3.6.1                Introduction                                                                   24

3.6.2                Circumstances which would trigger an assessment
of aesthetics                                                                   
24

3.6.3                Assessment process for aesthetic issues                        25

4                             Asbestos materials in soil                              26

4.1             Scope of the guidance                                                               26

4.2             Historical use of asbestos in Australia                                     26

4.3             Work Health and Safety                                                          26

4.4             Terminology for asbestos contamination in soil                     27

4.5             Occurrence of asbestos contamination in soil                         28

4.6             Asbestos soil contamination and health risk                           29

4.7             Basis for health screening levels for asbestos in soil              29

4.8             Health screening levels for asbestos in soil                              29

4.9             Process for assessment of asbestos contamination                 30

4.10          Determining asbestos in soil concentrations                           30

4.11          Assessment against asbestos screening levels and
procedure for exceedences                                                      
33

5                             Case Studies                                                  35

6                             Tabulated investigation and screening
levels                                                             
47

7                             Bibliography                                                 75

8                             Glossary                                                         78

9                             Shortened forms                                            81

 

 


1                  Introduction

1.1              Overview

The purpose of site assessment is to determine the human health and ecological risks associated with the presence of site contamination and to inform any remediation or management plan to make the site fit for the current or proposed land use. The appropriate use of investigation levels is an integral component of the assessment process.

 

This Schedule provides a framework for the use of investigation and screening levels. The framework is based on a matrix of human health and ecological soil and groundwater investigation and screening levels and guidance for specific contaminants. The derivation of health-based investigation levels is outlined in Schedule B7, and the risk assessment methodologies are detailed in Schedule B4. Schedule B5a outlines a risk-based framework for site-specific ecological risk assessment. The derivation of ecological investigation levels is outlined in Schedule B5c and the methodology is detailed in Schedule B5b. Reference is also made to the derivation and use of health and ecological screening levels in site assessment.

 

The selection of the most appropriate investigation levels for use in a range of environmental settings and land use scenarios should consider factors including the protection of human health, ecosystems, groundwater resources and aesthetics. The development of a conceptual site model is an essential element of site assessment and should inform the selection of appropriate investigation and screening criteria. A balance between the use of generic soil, soil vapour and groundwater criteria and site-specific considerations is essential practice in site assessment.

1.2              Prevention of site contamination

The National Environment Protection (Assessment of Site Contamination) Measure 1999 (NEPM) does not provide guidance on prevention of site contamination. Owners and occupiers of sites on which potentially contaminating activities are occurring are subject to the environmental protection legislation applying in each jurisdiction. Legislation provides for appropriate controls on potentially contaminating sources, including licensing of industrial activities, to minimise emissions and its application is the principal strategy for prevention of soil and groundwater contamination.

1.3              Specialised assessments

Specialised forms of assessment are required for sites affected by the following types of contaminants:

·         radioactive substances

·         unexploded ordnance

·         pathogenic materials and waste

·         explosive gas mixtures.

In situations where these materials occur on a site under assessment, guidance should be sought from the relevant jurisdictional environmental or health authority for assessment requirements. While the general principles of site assessment are applicable to these contamination types, compliance with specialised safety protocols and assessment guidance is essential to ensure protection of human health and the environment.

1.4              Acute hazards

Risk of explosion or other acute exposure hazards should be addressed immediately and are not within the scope of this guidance document.

Health effects can be broadly separated into acute and chronic effects. The distinction between acute and chronic exposure relates to the duration of exposure and the timing of onset of any health effects. Acute health effects occur within minutes, hours or days of a relatively short period of exposure, while chronic health effects occur as a result of prolonged or repeated exposures over many days, months or years and symptoms may not be readily apparent.

Most contaminated land assessments will be focussed on chronic health effects; however, some sites may pose acute risks. Assessment of sites with petroleum hydrocarbon contamination will need to consider the potential for acute health risks and the risk of fire and explosion from the presence of light non aqueous phase liquids (LNAPLs).

Work health and safety issues should be considered for all sites and managed according to national and jurisdictional legislative requirements.

1.5              Mineralised areas

High levels of metals, metalloids and asbestos can be associated with ore bodies. Soils in mining areas may contain elevated levels of these materials due to natural mineralisation. Some urban areas may be affected by asbestos and various elements including lead, copper, zinc, cadmium and arsenic from the ore bodies, as well as activities associated with mining, smelting and metallurgical industries.

 

Due to the health concerns associated with asbestos, affected areas should be effectively managed in the short and long term. Naturally occuring asbestos is most likely encountered during exploration and mining operations. Management measures similar to those for free fibre usually apply.

 

These environments may require specific prevention measures and community awareness programs when human settlement has occurred, to enable appropriate precautions to be taken (for example, preventing the use of potentially contaminated soil or fill from a mining site for growing vegetables in the home garden, constructing driveways or filling private land and publicly accessible areas). Public information about preventing exposure to mineralised or contaminated soil is an essential component of public health programs to minimise community exposure to these contaminants.

 

Depending on the nature of the contaminants associated with the mining (or quarrying) activity, contaminated soil may be only one of a number of exposure pathways. Local health issues may be more effectively targeted by monitoring key community health parameters such as blood lead or by environmental monitoring of ambient air quality and dust.

2                  Derivation of investigation and screening levels

2.1              Introduction

The purpose of this Schedule is to describe soil, soil vapour and groundwater criteria that can be used to evaluate potential risks to human health and ecosystems from site contamination. Investigation and screening levels are provided for commonly encountered contaminants which are applicable to generic land use scenarios and include consideration of, where possible, the soil type and the depth of contamination.

 

Investigation levels and screening levels are applicable to the first stage of site assessment. The selection and use of investigation and screening levels should be considered in the context of the iterative development of a conceptual site model (CSM) (refer Schedule B2 Section 4) to ensure appropriate evaluation of human health and ecosystem risks.

 

Site assessment should include consideration of all relevant human exposure pathways, ecological risks and risk to groundwater resources.

2.1.1        Definitions

Investigation levels and screening levels are the concentrations of a contaminant above which further appropriate investigation and evaluation will be required.

 

Investigation and screening levels provide the basis of Tier 1 risk assessment. A Tier 1 assessment is a risk-based analysis comparing site data with generic investigation and screening levels for various land uses to determine the need for further assessment or development of an appropriate management strategy. The application of investigation and screening levels is subject to a range of limitations.

 

Ecological investigation levels (EILs) have been developed for selected metals and organic substances and are applicable for assessing risk to terrestrial ecosystems. EILs depend on specific soil physicochemical properties and land use scenarios and generally apply to the top 2 m of soil. Further detail is provided in Section 2.5 and Schedule B5.

 

Ecological screening levels (ESLs) have been developed for selected petroleum hydrocarbon compounds and total petroleum hydrocarbon (TPH) fractions and are applicable for assessing risk to terrestrial ecosystems. ESLs broadly apply to coarse- and fine-grained soils and various land uses. They are generally applicable to the top 2 m of soil. Further detail on their use is provided in Section 2.6 and Warne (2010a, 2010b), available from the ASC NEPM Toolbox.

 

Groundwater investigation levels (GILs) are the concentrations of a contaminant in groundwater above which further investigation (point of extraction) or a response (point of use) is required. GILs are based on Australian water quality guidelines and drinking water guidelines and are applicable for assessing human health risk and ecological risk from direct contact (including consumption) with groundwater. Further information is provided in Section 2.8 and Schedule B6.

 

Health investigation levels (HILs) have been developed for a broad range of metals and organic substances. The HILs are applicable for assessing human health risk via all relevant pathways of exposure. The HILs are generic to all soil types and apply generally to a depth of 3 m below the surface for residential use. Site-specific conditions should determine the depth to which HILs apply for other land uses. Further detail is provided in Section 2.2 and Schedules B4 and B7.

 

Interim soil vapour health investigation levels (interim HILs) have been developed for selected volatile organic chlorinated compounds (VOCCs) and are applicable to assessing human health risk by the inhalational pathway.  They have interim status pending further scientific work on volatile gas modelling from the sub-surface to building interiors for chlorinated compounds. Further detail on their use is provided in Section 2.3 and Schedule B4.

 

Health screening levels (HSLs) have been developed for selected petroleum compounds and fractions and are applicable to assessing human health risk via the inhalation and direct contact pathways. The HSLs depend on specific soil physicochemical properties, land use scenarios, and the characteristics of building structures. They apply to different soil types, and depths below surface to >4 m. Further detail on their use is provided in Section 2.4 and Friebel and Nadebaum (2011a, 2011b & 2011c).

 

‘Petroleum hydrocarbon management limits’ (‘management limits’) are applicable to petroleum hydrocarbon compounds only. They are applicable as screening levels following evaluation of human health and ecological risks and risks to groundwater resources.  They are relevant for operating sites where significant sub-surface leakage of petroleum compounds has occurred and when decommissioning industrial and commercial sites.  Further detail on their use is provided in Section 2.9, including factors to be considered in determining the depth to which they apply.

2.1.2        Inappropriate use of investigation levels and screening levels

Investigation and screening levels are not clean-up or response levels nor are they desirable soil quality criteria. Investigation and screening levels are intended for assessing existing contamination and to trigger consideration of an appropriate site-specific risk-based approach or appropriate risk management options when they are exceeded. The use of these levels in regulating emissions and application of wastes to soil is inappropriate.

 

The use of investigation and screening levels as default remediation criteria may result in unnecessary remediation and increased development costs, unnecessary disturbance to the site and local environment, and potential waste of valuable landfill space. Similarly, the inclusion of an investigation and screening level in this guidance should not be interpreted as condoning discharges of waste up to these levels.

2.2              Health investigation levels

The health risk assessment methodology that forms the basis for calculation of HILs is provided in Schedule B4. The derivation of the HILs is presented in Schedule B7 (and appendices) and uses the Australian exposure factor guidance (enHealth 2012). The derivation of the HILs is illustrated by two worked examples for cadmium and benzo(a)pyrene (refer Schedule B7 Appendix B). The spreadsheet for calculating HILs is included in the ASC NEPM Toolbox (www.scew.gov.au/nepms/assessment-of-site-contamination.html).

 

The HILs are listed in Table 1A(1), found at the end of this Schedule.

 

HILs are scientifically based, generic assessment criteria designed to be used in the first stage (Tier 1 or ‘screening’) of an assessment of potential risks to human health from chronic exposure to contaminants. They are intentionally conservative and are based on a reasonable worst-case scenario for four generic land use settings:

·         HIL A - residential with garden/accessible soil (home grown produce <10% fruit and vegetable intake, (no poultry), also includes children’s day care centres, preschools and primary schools

·         HIL B - residential with minimal opportunities for soil access includes dwellings with fully and permanently paved yard space such as high-rise buildings and flats

·         HIL C - public open space such as parks, playgrounds, playing fields (e.g. ovals), secondary schools and footpaths. It does not include undeveloped public open space (such as urban bushland and reserves) which should be subject to a site-specific assessment where appropriate

·         HIL D - commercial/industrial such as shops, offices, factories and industrial sites.

The land use scenarios are described in detail in Section 3 of Schedule B7. To make generic estimates of potential human exposure to soil contaminants, scientifically based assumptions are made about the environment, human behaviour, the physicochemical characteristics of contaminants, and the fate and transport of contaminants in soil within each of these land use categories. The HILs are derived by integrating these exposure estimates with toxicity reference values, that is, tolerable daily intakes (TDI), acceptable daily intakes (ADI), and reference doses (RfD), to estimate the soil concentration of a substance that will prevent exceedence of the toxicity reference value under the defined scenario. The toxicity reference values are generally based on the known most sensitive significant toxicological effect. Where toxicity reference values come from multiple sources, their underlying assumptions, defaults and science policy should be compatible and generally similar.

 

HILs establish the concentration of a contaminant above which further appropriate health investigation and evaluation will be required. Levels slightly in excess of the HILs do not imply unacceptability or that a significant health risk is likely to be present. Exceeding a HIL means further investigation is required and not ‘risk is present, clean-up required’.

 

The HILs are referred to by regulators, auditors and consultants in the process of assessing soil contamination. HILs apply generally to the top 3 m of soil for residential use. Site-specific conditions should determine the depth to which HILs apply for other land uses.

 

HILs are not intended to be clean-up levels. The decision on whether clean-up is required, and to what extent, should be based on site-specific assessment triggered by an exceedence of the HIL. Health risk assessment is the primary driver for making site decisions. Other considerations such as practicality, timescale, effectiveness, cost, sustainability and associated ecological risk assessment are also relevant.

2.3              Interim HILs for volatile organic chlorinated compounds

Interim HIL soil vapour levels for specific volatile organic chlorinated compounds (VOCCs) have been developed (see Table 1A(2) at the end of this Schedule) to assess the vapour inhalation pathway (also known as the ‘vapour intrusion’ pathway when referring to indoor exposure). The derivation of the interim HILs is presented in Schedule B7 and Appendix A6. The methodology employs a simple though conservative approach using an attenuation factor that relates the concentration of a volatile contaminant in indoor air to the concentration in soil gas immediately below a building foundation slab.

 

The interim HIL values derived for volatile compounds are driven by the vapour intrusion pathway (that contributes >99% of the total risk when all pathways are considered). However, it is noted that there are limitations and uncertainties associated with the assessment of volatile contaminants on the basis of soil concentrations. As these limitations are significant for volatile organic chlorinated compounds, interim HILs for soil have not been derived. Rather it is recognised that where indoor/ambient air data cannot be collected (or the data is adversely affected by background sources), the most relevant approach to the assessment of this pathway is through the collection of soil vapour data. On this basis, interim HILs have been developed for soil vapour.

 

The interim HILs provide Tier 1 guidance for health risks from soil contamination sources and groundwater plumes associated with this group of compounds. The values may be applied for general site assessment and sub-slab environments for evaluation of potential health risks for the 0-1 m sub-slab profile. The interim HILs broadly apply to the same generic land use categories as do the HILs, though  the values for residential A and B are combined as they are based on the same exposure conditions (i.e. the same amount of time spent indoors) for the vapour inhalation pathway.  In addition, secondary school buildings should be treated as residential for the purposes of evaluating risks from vapour intrusion.

 

Biodegradation of VOCCs has not been included in the development of the interim HILs. The biodegradation approach developed for petroleum hydrocarbons (refer Section 2.4.10) is not applicable to the degradation of VOCCs as the mechanism by which degradation occurs is different for most chlorinated hydrocarbons compared with petroleum hydrocarbons.

2.4              Health screening levels for petroleum hydrocarbon compounds

2.4.1        Introduction

Site contamination by petroleum hydrocarbon compounds is frequently encountered. The complex mixtures of aliphatic and aromatic compounds that comprise petroleum hydrocarbon products present human health concerns predominantly through inhalation of vapours from contaminant sources and by direct contact with affected soils and groundwater. Assessment of petroleum impacts should include evaluation of risks via the groundwater pathway (e.g. consumption of contaminated groundwater that is not considered in the HSLs), the risk to groundwater resources and appropriate consideration of aesthetics. The application of relevant ecological and ‘management’ criteria for petroleum compounds is discussed in Sections 2.6 and 2.9.

 

Health Screening Levels (HSLs) for various petroleum hydrocarbon compounds were developed by the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE). The principal reference for the HSL methodology is Friebel and Nadebaum (2011a). In addition to the documentation of the methodology, a detailed application report (Friebel & Nadebaum 2011b) and a sensitivity analysis of the main parameter inputs ((Friebel & Nadebaum 2011c) are available.

 

Predictive modelling of sub-surface vapour movement in soil and penetration of building structures is a field of intensive data collection and research. The most recent research and derivation approaches adopted in developed international jurisdictions have been considered and adapted, as far as is practicable, for Australian conditions, to derive Tier 1 screening criteria for evaluating human health risk from petroleum hydrocarbons.

 

The HSLs’ development was guided by a project advisory group with health, environmental, assessment and remediation, petroleum industry and regulatory expertise. A specialised technical working group provided technical support and review throughout the development process. The HSL methodology was subject to international peer review during its development.

 

Copies of the technical reports can be found in the ASC NEPM Toolbox. Additional information on the development phases of the project, including responses to peer review comments, can be found on the CRC CARE website:

 http://www.crccare.com/publications/technical_reports/hsl_tech_report.html

Assessment of vapour risks is a specialist area. It is the responsibility of contaminated land professionals to become familiar with the limitations of the HSLs and their correct application in site assessment (Friebel & Nadebaum 2011a, 2011b, 2011c).

2.4.2        HSL methodology

The HSLs were developed to be protective of human health by determining the reasonable maximum exposure from site sources for a range of situations commonly encountered on contaminated sites. As there are many parameter inputs to the methodology, very conservative assumptions have not been made for every parameter as this would result in an unrealistic result arising from the compounding of conservatism. Typically the parameter values selected correspond to the mean or median of the available information, with some parameters corresponding to the 95th percentile. For further information on the rationale for each parameter selected, refer to Friebel and Nadebaum (2011a).

 

The HSLs apply to the same land use settings as for the interim HILs for VOCCs and include  additional consideration of soil texture and depth to source to determine the appropriate soil, groundwater and soil vapour criteria for the exposure scenario. As with all modelling approaches, the assumptions made regarding the exposure scenario limit the extent of their reasonable application. The main limitations for the HSLs are summarised in Section 2.4.13.

 

HSLs for soil (Table 1A(3)), groundwater  (Table  1A(4)) and soil vapour (Table 1A(5)) apply to exposure to petroleum hydrocarbons through the dominant vapour inhalation exposure pathway only. Direct contact HSLs have been developed for the incidental soil ingestion, dermal and inhalation exposure pathways. The direct contact HSLs are generally not the risk drivers for further site assessment for the same contamination source as the HSLs for vapour intrusion.  Direct contact exposure should be considered where relevant to the site-specific scenario e.g. an external source in near-surface soils in a residential or recreational setting. Further details can be found in Friebel and Nadebaum (2011a, 2011b, and 2011c).

 

There are many site-specific, soil-specific and building-specific variables that affect the level of the HSLs and these factors should be considered in the site assessment. Detailed information on the model inputs and assumptions (for example, soil properties, sub-slab attenuation factor, organic carbon content, chemical properties, building parameters) and overall limitations are provided in Friebel and Nadebaum (2011a). A sensitivity analysis was used to evaluate the effect that these parameters have on the derived HSLs (Friebel & Nadebaum 2011c).

 

A review of vapour models was undertaken by CSIRO as a precursor project to the development of the HSLs (Davis et al. 2009c). As a result of this review, a modified Johnson and Ettinger vapour exposure model (US EPA 2004) was selected to derive HSLs for the vapour inhalation pathway. The model has been used assuming a finite source for soils equivalent to a source thickness of 2 m which avoids the extreme conservatism associated with assuming an infinite source and reflects empirical field observations. For groundwater and soil vapour, an infinite source (i.e. steady state model) has been assumed as replenishment of vapours may occur by contaminated groundwater flowing beneath the site.

 

It is noted that the Johnson and Ettinger model and other similar vapour intrusion models do not adequately address vapour risk issues where there are preferential vapour migration pathways, where the building structure extends into a saturated contaminated zone (i.e. into the groundwater table) or where biodegradation is of significance (see section 2.4.10 for further information).

 

The soil and groundwater HSLs are based on three-phase equilibrium theory and soil vapour is limited by the maximum solubility limit of the chemical in the soil pore water phase or the groundwater. The soil saturation concentration of a particular contaminant is the condition where pore water is at its solubility limit and soil vapour is at the maximum vapour concentration. When a calculated HSL in soil or groundwater exceeds this limit, the vapour in the soil or above groundwater cannot result in an unacceptable vapour risk and is denoted as NL (not limiting) in the HSL tables (Tables 1 A(3) - 1A(5)). Soil vapour HSLs are based on the vapour pressures of individual chemicals. Calculated soil vapour HSLs that exceed the possible maximums are similarly denoted as NL.

 

The HSLs have been derived using accepted approaches to assessment for non threshold (cancer) risk and threshold (non-cancer) risk. Exposure factors for the individual carcinogenic and non-carcinogenic compounds of concern were derived from a near-final draft of enHealth (2012).

2.4.3        Sub-slab to indoor air attenuation factor

Unlike the derivation of the soil vapour interim HILs, the attenuation factor adopted for petroleum hydrocarbon compounds is not used directly to calculate indoor air concentrations from soil gas concentrations (or vice versa); rather it is used to calculate one of the many input parameters (advective air flow) in the Johnson & Ettinger model. For further information refer to section 7.3.2 of Friebel and Nadebaum (2011a).

 

As for other input parameters, the selected value for the attenuation factor is based on a reasonable assumption rather than the maximum possible exposure and is equivalent to the median of the US EPA 2008 attenuation factor database (US EPA 2008) and lies within the 75th to 95th percentiles of the updated database published in 2012 (US EPA 2012). The selected value of 0.005 was considered to represent the upper value not affected by indoor air sources, background air or other confounding factors.

2.4.4        Petroleum fuel composition

The soil saturation and water solubility limits used in the derivation of the HSLs assume a fixed fuel composition based on fresh petrol and diesel fuels typical of those available in Australia. The HSLs may be applied to other fuel types (e.g. kerosene, aviation fuel and fuel oil) providing that the aliphatic/aromatic speciation is similar to that assumed in the derivation of the HSLs (80:20). Further information on these fuel types can be found in TPHCWG (1998). There are a number of fuel additives, such as MTBE and ethanol, for which HSLs have not been derived. Where these are identified as potential contaminants of concern, then a site-specific risk assessment for these chemicals should be considered.

 

The HSLs apply to petroleum contamination sources and are not applicable to pure compound solvents, as solubility limits incorporated into the HSLs were derived based on typical petrol and diesel fuel mixtures. Equivalent values to the HSLs applicable to pure compounds (rather than fuel mixtures) are available in Friebel and Nadebaum (2011a Appendix C).

2.4.5        The Total Recoverable Hydrocarbons analytical method

The Total Recoverable Hydrocarbons (TRH) method is recommended for the analysis of petroleum hydrocarbon compounds in soil. Detailed information is provided in Schedule B3.

 

The term TRH is equivalent to the previously used total petroleum hydrocarbons (TPH) and represents extracted biogenic (biological) and petrogenic (petroleum) hydrocarbons by selected solvents. The TRH analysis is non-specific and will extract organic compounds such as ethanol, biodiesel compounds (esterised long chain fatty acids), organic acids, sterols and n-alkanes from plant waxes, as well as petroleum hydrocarbons. The sample extraction process may also extract other industrial organic chemicals. When used in the context of a screening assessment for petroleum hydrocarbon contamination, TRH analyses are likely to be conservative when non-petroleum compounds are present.

 

The potential for inclusion of non-petroleum compounds in the results may be relevant for site-specific assessment of petroleum hydrocarbon contamination. For example, the TRH analytical results may be overly conservative if soil organic matter is unusually high, for example from heavy applications of mulch, manure, compost or other natural organic material, or the presence of other synthetic organic compounds which are extractable in the analytical process. To assess potential false positive results, it is recommended that equivalent soil from the site, unaffected by petroleum hydrocarbon contamination, is analysed for comparison.

 

Where there is reasonable doubt as to the nature of the contamination, the sample may be subjected to a silica gel clean-up and analysed by gas chromatography mass spectrometry (GC-MS) (or other appropriate analytical method) to assist with the identification of contamination of petroleum origin. In these cases, an analyst report should be obtained with an interpretation of the chromatogram and the nature and extent of contamination present in the sample.

2.4.6        Petroleum hydrocarbon compounds and fractions

HSLs have been developed for BTEX and naphthalene plus four carbon chain fractions based on the fractions adopted in the Canada-wide standard for petroleum hydrocarbons (PHC) in soil (CCME 2008). The fractions are listed in Table 1 below:

Table 1. HSL fractions and corresponding equivalent carbon range

Fraction number

Equivalent carbon number range

F1

C6 – C10

F2

>C10 – C16

F3

>C16 – C34

F4

>C34  - C40

 

The HSLs are provided in Tables 1A(3) – 1A(5)).

 

BTEX results should be subtracted from the TRH C6 – C10 analytical results for comparison with the HSL for F1. Likewise, naphthalene should be subtracted from >C10 – C16 for comparison with the HSL for F2.

 

Chemicals in the >C16-C34 and >C34-C40 fractions are non-volatile and therefore not of concern for vapour intrusion, however, exposure can be via direct contact pathways (dermal contact and incidental ingestion and inhalation of soil particles). Direct contact HSLs for these fractions can be found in Friebel and Nadebaum (2011a).

2.4.7        Soil texture

HSLs for soil, groundwater and soil vapour have been developed for sand, silt and clay soils based on the US soil texture classification system (Friebel & Nadebaum 2011a). The HSLs assume a uniform soil profile and the soil texture making up the greatest proportion of the soil profile should be used in selecting the appropriate HSLs (Friebel & Nadebaum 2011a and 2011b).

 

For Tier 1 soil assessment, the HSL classifications of sand, silt and clay may be broadly applied to the soil texture classification in Table A1 of Standard AS 1726.

Table 2. HSL soil classification and equivalent soil classification in AS 1726

HSL soil classification

AS 1726 Equivalent

Sand

Coarse-grained soil

Silt

Fine-grained soil - silts and clays (liquid limit <50%)

Clay

Fine-grained soil - silts and clays (liquid limit >50%)

Where there is reasonable doubt as to the appropriate soil texture to select, either a conservative selection should be made (i.e. select coarsest applicable grain size such as sand) or laboratory analysis carried out to determine particle size and hence soil texture sub-class (refer Section 7.3.1 in Friebel and Nadebaum 2011b). If particle size analysis is undertaken then laboratory measurement of additional parameters used in site-specific risk assessment (such as soil moisture content, organic carbon content and saturation porosity - refer Friebel & Nadebaum 2011b for further information) could also be considered if further assessment is possible. If laboratory measurement is undertaken, sufficient samples should be obtained and analysed to determine a representative value for each soil unit of interest for the assessment.

2.4.8        Land use

The HSLs are derived for various depths to source and for the same generic land uses as for the HILs (described in detail in Schedule B7). The values for residential A and B are combined in the HSL tables as they are based on the same exposure conditions for the vapour inhalation pathway (i.e. the same amount of time spent indoors).

 

The HSLs are applicable to ground floor land use. If the vapour exposure is acceptable at ground level, it can be assumed that it is also acceptable for floors above ground level.  For multistorey buildings where non-residential uses (e.g. car parking or commercial use) exist in a basement or at ground level, then land use category D (commercial/industrial) should be applied.

 

Any sensitive land uses e.g. childcare or day care centre will require application of HSL A irrespective of their planning zoning.  Secondary school buildings (as opposed to secondary school grounds) should also be assessed using HSL A.

2.4.9        Adjusting  HSLs to site-specific circumstances

The HSL methodology enables parameter inputs to be changed to more accurately reflect local soil, site or building conditions. Input parameters should be selected to be representative of long-term stable conditions and appropriate to the soil unit/aquifer of concern e.g. moisture content may vary seasonally and may also be different beneath buildings. Where insufficient data is available to establish a representative value, a conservative approach should be taken, for example, by assuming dry soil moisture conditions in sand. The HSL application and sensitivity documents (Friebel & Nadebaum 2011b, 2011c) provide further details. Jurisdictions may also adopt policies to vary the HSLs to account for local conditions.

 

For example, air exchange rates have been set at 0.6 building volumes/hr which may not be appropriate for buildings designed for tropical and cold climates. Similarly, soil moisture has a significant effect on penetration of volatiles into buildings.

 

The HSL derivation has assumed a slab-on-ground construction. Elevated buildings on concrete supports or timber poles with no direct floor contact with the soil and clear underfloor ventilation are at lower risk of penetration of volatiles and the risk decreases with the elevation of the floor above ground. The state of the slab will require consideration if it has deteriorated, as cracks can act as preferential pathways.

2.4.10    Biodegradation

Recent research on underslab biodegradation of petroleum hydrocarbon contamination is reported in Davis et al. (2009a and 2009b). This research identified that the following site conditions are conducive to biodegradation of petroleum hydrocarbon compounds in the sub-surface:

·         the presence of oxygen at concentrations greater than 5% in soil vapour at a depth 1 m below the surface immediately adjacent to the concrete slab

and

·         a maximum slab width of less than 15 m, with oxygen access on both sides of the slab for Tier 1 screening purposes. A distance of 7-8 m from the exposed soil at the slab boundary is considered the maximum lateral underslab penetration of oxygen.

It is noted that the measurement of oxygen in the soil profile can be difficult and care should be taken when using this data to support biodegradation.

 

If these conditions are fulfilled, biodegradation factors can be applied to the vapour intrusion HSLs as follows:

·         factor of x10 for depths to source of 2 to <4 m and

·         factor of x100 for depths to source of 4 m and greater where the vapour source strength is 100 mg/L (100,000 mg/m3) or less.

The biodegradation factors above are not applicable for depths of less than 2 m. For the purpose of this NEPM, assessment including biodegradation of petroleum hydrocarbons is considered a Tier 1 activity.

 

Application of the biodegradation factors described above may result in levels of TPH, BTEX and naphthalene that are acceptable for human health risk from the vapour exposure pathway for the specific land use but which may not be acceptable for protection of the environment or water resources or from an aesthetics perspective. Site results should be considered with reference to relevant ecological and ’management levels‘(refer Sections 2.5 and 2.9) which may become the predominant risk driver. Management levels should be applied after human health, ecological risks and risks to groundwater resources have been assessed.

2.4.11    Direct contact HSLs

Direct contact HSLs have been developed for exposure through dermal contact, incidental oral ingestion and dust inhalation and then combined as a single HSL for direct contact with soil (Friebel & Nadebaum, 2011a).  For most site assessments, the direct contact HSLs are unlikely to become drivers for further investigation or site management as the values are significantly higher than most other soil screening levels and consequently have not been included here.  There are situations where the combined vapour and direct contact pathways can make a difference to the outcome of the assessment. For further information on considering combined vapour and direct contact exposure, refer to Section 3.3 of Friebel and Nadebaum (2011b). The combined HSLs for direct contact can be found in Appendix A of Friebel & Nadebaum (2011a).

 

Contamination at the levels of the direct contact HSLs are likely to present unacceptable aesthetic considerations which should be addressed in accordance with the discussion in Section 3.6.  Exposure to a contaminated surface (other than of short and temporary duration) at the levels of the direct contact HSLs may also cause an unacceptable short-term vapour exposure risk.

2.4.12    HSLs and multiple-lines-of-evidence approach

For an assessor to conclude that the vapour intrusion/emission pathways are unlikely to be active or to present a significant risk, the assessor should undertake a multiple-lines-of-evidence approach. This requires the assessor to present several reasoned lines of evidence as to why the pathway is considered inactive or is unlikely to present a significant risk.

 

The soil and groundwater HSLs provide the principal assessment criteria for open excavations (such as tank removal operations) while greater emphasis is placed on soil vapour HSLs in assessing potential vapour intrusion risks from hydrocarbon sources and groundwater plumes adjacent to or under buildings. In general, evaluating all contaminant phases will provide greater confidence in the outcomes of the site assessment.

 

Soil vapour measurements can provide a more accurate representation of vapour risks (compared with the soil and groundwater HSLs), depending on site-specific conditions e.g. where soil vapour can be measured directly under conditions that are relevant to the future or continuing use of the site. In high moisture conditions, however, such as occur within the capillary fringe or as a result of seasonal watertable fluctuations, it is not possible to obtain reliable soil vapour readings. In these conditions, consideration may be given to obtaining vapour headspace readings from appropriately constructed groundwater monitoring wells fitted with a soil vapour monitoring cap that seals the groundwater well from the atmosphere.

 

Soil vapour measurements are also preferred where contaminated groundwater is present at less than 2 m below the ground or basement foundation, though in fine-grained soils the ability to obtain soil vapour measurements may be constrained by moisture conditions, as the thickness of the capillary fringe increases as the soil texture decreases.

 

Where the watertable rises seasonally to intersect basements or building foundations, indoor air measurements will be required to assess vapour risk. The assessment approach may also include soil vapour measurements taken in the dry season as part of a multiple-lines-of-evidence approach.

 

Additional information on vapour assessment and the multiple-lines-of-evidence approach is provided in Section 9.2 of Schedule B2 and Friebel and Nadebaum (2011a, 2011b).

2.4.13    Limitations of the HSLs

As with all generic screening levels, actual site-specific conditions may mean that the assumptions underpinning the derivation of the screening levels are not valid for the site and consequently a site-specific assessment will be required. The principal limitations applicable to the HSLs are listed in Table 3 below, together with suggested alternative assessment approaches.

Immediate action should be taken where potentially explosive or acutely toxic gas concentrations are present in buildings or in-ground services (e.g. utility trenches, sumps or drains) connecting a vapour source to a building. Emergency management actions, such as relocation of building occupants, should be implemented as necessary.

 

Table 3.  Site scenarios where the application of the HSLs is limited and possible alternative assessment approaches

Site scenario

Alternative assessment approach

The identified contamination has an atypical petroleum composition

 

Site-specific risk assessment including assessment of cumulative effects of chemical constituents

Contaminated groundwater or LNAPL is entering or is in contact with a basement or building foundation

Consider indoor air sampling

Depth to groundwater impact is less than 2 m

Consider soil vapour measurements for vapour intrusion

The impacted soil source thickness is significantly greater than 2 m

 

HSLs may be conservative for thinner soil sources. For thicker soil sources, refer to Section 2.4.7 of the HSLs application document (Friebel & Nadebaum 2011b)

A preferential migration pathway is present that could connect a vapour source to a building interior

Site-specific assessment

 

Hydrocarbon odour present in buildings or in-ground services (not attributable to an indoor or ambient source) which indicates an active preferential migration pathway and potentially an immediate human health risk

Consider indoor air sampling or immediate action in the case of strong hydrocarbon odours

 

2.5              Ecological investigation levels

2.5.1        Introduction

Ecological investigation levels (EILs) for the protection of terrestrial ecosystems have been derived for common contaminants in soil based on a species sensitivity distribution (SSD) model developed for Australian conditions. EILs have been derived for As, Cu, CrIII, DDT, naphthalene, Ni, Pb and Zn.

 

Schedule B5a provides detailed guidance on the framework for ecological risk assessment. The methodology for deriving EILs is described in Schedule B5b and the detailed derivations of EILs for As, Cu, CrIII, DDT, naphthalene, Ni, Pb and Zn are presented in Schedule B5c. A spreadsheet, which may be used for calculating site-specific EILs is included in the ASC NEPM Toolbox.

2.5.2        EIL methodology

The detailed methodology, incorporated in Schedule B5b, was developed by CSIRO using data from various Australasian databases, the Australian National Biosolids Research Program and supplemented by data from the US EPA ecotoxicology database where necessary. The methodology is based on an SSD approach, which considers the physicochemical properties of soil and contaminants and the capacity of the local ecosystem to accommodate increases in contaminant levels (referred to as the ‘added contaminant limit’ or ACL) above ambient background.  Where insufficient data is available for the SSD method to be used, a more conservative method using an assessment factor approach may be adopted.

 

The EILs are derived for specified levels of percentage species protection depending on land use. The approach is analogous to the methodology used for derivation of the Australian water quality guidelines (ANZECC & ARMCANZ 2000).

2.5.3        Land use

EILs have been developed for three generic land use settings:

·         areas of ecological significance

·         urban residential areas and public open space

·         commercial and industrial land uses.

An area of ecological significance is one where the planning provisions or land use designation is for the primary intention of conserving and protecting the natural environment. This would include national parks, state parks, wilderness areas and designated conservation areas.

 

Urban residential/public open space is broadly equivalent to the HIL A, HIL B and HIL C land use scenarios (see Section 2.2 and Schedule B7).

 

EILs are not applicable to agricultural soils, which need evaluation in relation to crop toxicity, plant contaminant uptake and detailed consideration of soil type.

2.5.4        Levels of protection

The protection levels for the generic land use settings are:

·         99% for areas of ecological significance

·         80% for urban residential areas and public open space

·         60% for commercial and industrial land uses.

These protection levels are increased by 5% when biomagnification may occur (refer Schedule B5b).

2.5.5        Ecotoxicity data

The NEPM has adopted lowest observed effect concentration (LOEC) or effective concentration 30% (EC30) data to derive EILs for the land use scenarios.

 

The LOEC is the lowest concentration used in a toxicity test that causes a toxic effect that is significantly different from the control. EC30 data is the concentrations of contaminants that cause an effect on 30% of the test group of an organism after a specified exposure time. The data is drawn from a range of species to derive individual EILs.

 

For further information see Schedule B5b.

2.5.6        Depth of application

EILs apply principally to contaminants in the top 2 m of soil at the finished surface/ground level which corresponds to the root zone and habitation zone of many species. In arid regions, where the predominant species may have greater root penetration, specific considerations may result in their application to 3 m depth.

2.5.7        Ambient background concentration

The methodology assumes that the ecosystem is adapted to the ambient background concentration (ABC) for the locality and that it is only adding contaminants over and above this background concentration which has an adverse effect on the environment.

 

The ABC of a contaminant is the soil concentration in a specified locality that is the sum of the naturally occurring background level and the contaminant levels that have been introduced from diffuse or non-point sources by general anthropogenic activity not attributed to industrial, commercial, or agricultural activities, for example, motor vehicle emissions. Methods to estimate background levels are provided in Schedule B5b.

 

Three methods for determining the ABC are presented in Schedule B5b. The preferred method is to measure the ABC at an appropriate reference site. This approach is essential in areas where there is a high naturally occurring background level such as will occur in mineralised areas.

 

In other situations where an appropriate reference site cannot be determined, the method based on urban metal levels in Olszowy et al. (1995) or the method from Hamon et al. (2004) may be used.

 

In the method of Hamon et al. (2004), the ABC varies (depending on the element) with the soil iron and/or manganese concentration; for example, the ABC for zinc varies from
3 to 62mg/kg in soils with soil iron concentrations between 0.1% and 20%. Alternatively, ABCs for old and new suburbs and high and low traffic areas for New South Wales, Queensland, South Australia and Victoria for Zn, Cu, Ni, Pb, and CrIII are included in
 Schedule B5b and are derived from Olszowy et al. (1995). Values for new suburbs would be appropriate to use for new suburbs or in areas with no known history of contamination for that metal. In old-established urban areas (i.e. suburbs more than 20 years old), it would be appropriate to use the 25th percentile of the ABC values from Olszowy et al. (1995).

 

In some situations the ABC may be comparatively low and have a minor effect on the magnitude of the site EIL.

2.5.8        Added contaminant limits

An added contaminant limit (ACL) is the added concentration (above the ABC) of a contaminant above which further appropriate investigation and evaluation of the impact on ecological values is required. The EIL is derived by summing the ACL and the ABC.

 

ACLs are based on the soil characteristics of pH, CEC and clay content. Empirical relationships that can model the effect of these soil properties on toxicity are used to develop soil-specific values. These soil-specific values take into account the biological availability of the element in various soils. In this approach different soils will have different contaminant EILs rather than a single generic EIL for each contaminant.

 

ACLs apply to chromium III (CrIII), copper (Cu), nickel (Ni) and zinc (Zn) for site-specific EIL determination. The soil properties to be determined for each relevant soil type at the site, are shown in Table 4 below.

Table 4:          Soil properties to be measured for site-specific derivation of ACLs for CrIII, Cu, Ni and Zn

Soil physicochemical property

CrIII

Cu

Ni

Zn

pH

 

P

 

 

CEC

 

P

P

P

% clay

P

 

 

 

 

Insufficient data was available to derive ACLs for arsenic (As), DDT, lead (Pb) and naphthalene. As a result, the derived EILs are generic to all soils and are presented as total soil contaminant concentrations in Tables 1B(4) and 1B(5).

2.5.9        Ageing of contamination and soil properties

In general the toxicity of soil contaminants (both organic and inorganic) will reduce or age over time to a lower and more stable level by binding to various soil components and decreasing their biological availability. Hence, toxicity can be affected by the physicochemical or chemical properties of the soil including clay content, cation exchange capacity (CEC) measured in centi-mole charge/kg (cmolc/kg), pH, iron and organic carbon content.

 

For the purposes of EIL derivation, a contaminant incorporated in soil for at least two years is considered to be aged for the purpose of EIL derivation. The majority of contaminated sites are likely to be affected by aged contamination. Fresh contamination is usually associated with current industrial activity and chemical spills.

 

In some cases insufficient data on aged contamination was available to apply the EIL methodology, and where possible, ageing factors based on relevant studies have been applied to determine a soil value for aged contamination.

 

EIL determination for fresh contamination (that is, present for less than two years) for the relevant contaminants should be site-specifically determined by reference to the relevant tables in Schedule B5c.

2.5.10    Determining site-specific EILs

Detailed information on the derivation of the EILs is provided in Schedule B5c. The following section describes the steps that are taken to derive site-specific EILs. A spreadsheet is included in the ASC NEPM Toolbox which can also be used for calculating site-specific EILs.

A.        EILs for Ni, Cr III, Cu, Zn and Pb aged contamination (>2 years)

Steps 1–4 below describe the process for deriving site-specific EILs for the above elements using Tables 1B(1) – 1B(4), which can be found at the end of this Schedule.

1.         Measure or analyse the soil properties relevant to the potential contaminant of concern (see Table 4). Sufficient samples need to be taken for these determinations to obtain representative values for each soil type in which the contaminant occurs.

2.         Establish the sample ACL for the appropriate land use and with consideration of the soil-specific pH, clay content or CEC. The ACL for Cu may be determined by pH or CEC and the lower of the determined values should be selected for EIL calculation. Note that the ACL for Pb is taken directly from Table 1(B)4.

3.         Calculate the contaminant ABC in soil for the particular contaminant and location from a suitable reference site measurement or other appropriate method.

4.         Calculate the EIL by summing the ACL and ABC:

EIL = ABC + ACL

B.        EILs for As, DDT and naphthalene

EILs for aged contamination for DDT and naphthalene are not available and the adopted EIL is based on fresh contamination taken directly from Table 1B(5). The EILs for As, DDT and naphthalene are generic i.e. they are not dependent on soil type and are taken directly from Table 1B(5). Only EILs for fresh contamination are available for As, DDT and naphthalene due to the absence of suitable data for aged contaminants.

2.6              Ecological screening levels for petroleum hydrocarbon compounds

2.6.1        Introduction

Ecological screening levels (ESLs) are presented based on a review of  Canadian guidance for petroleum hydrocarbons in soil and application of the Australian methodology (Schedule B5b) to derive Tier 1 ESLs for BTEX, benzo(a)pyrene and F1 and F2 (Warne 2010a, 2010b).

 

The Canadian Council of the Ministers of the Environment (CCME) has adopted risk-based TPH standards for human health and ecological aspects for various land uses in the Canada-wide standard for petroleum hydrocarbons (PHC) in soil (CCME 2008) (CWS PHC). The standards established soil values including ecologically based criteria for sites affected by TPH contamination for coarse- and fine-grained soil types.

 

The standard applies to the same four fractions (F1–F4) adopted for the HSLs (refer Section 2.4.5 of this Schedule).

2.6.2        ESL Methodology

The CWS PHC approach uses an SSD method and, when there is insufficient data for the SSD method, applies a weight-of-evidence approach to derive ecologically based ’Tier 1 eco soil contact‘ values for TPH fractions and specific compounds. The overall approach has similarities to the Australian EIL methodology by developing protective criteria based on EC25 toxicity for residential land use and EC50 for commercial/industrial land (cf. Australia EC30 and LOEC data).

 

The Australian EIL methodology was applied to the ecotoxicity data used to derive the Canadian F1 and F2 (eco soil contact) values (Warne 2010a) to produce comparable Tier 1 values for these fractions. Based on the data quality and applicability to the Australian environment, the derived values for F1 and F2 are adopted as moderate reliability ESLs (see Table 1B(6) at the end of this Schedule) and apply generically to fine- and coarse-grained soils.

 

Due to the limited ecotoxicity data for F3 and F4, the Australian methodology was not able to be applied. The data limitations were recognised in the Canadian guidance and an alternative weight-of-evidence approach was used to develop values for these fractions. Consequently, the adopted values for F3 and F4 (see Table 1B(6)) are considered low reliability ESLs for fine- and coarse-grained soils (Warne 2010a, 2010b).

 

A further review of Canadian soil quality guidelines was undertaken for BTEX and benzo(a)pyrene (Warne 2010b) and the Australian methodology applied to the ecotoxicological data as far as possible to derive equivalent ESLs. However, data limitations did not allow the full use of the EIL derivation methodology and the resulting values are adopted as low reliability ESLs in Table 1B(6). Values were derived using the Canadian data reduction methods, the Australian SSD method and employing the Australian levels of protection for various land uses.

 

ESLs for the adopted carbon fraction ranges are based on TRH analysis with F1 being obtained after subtraction of BTEX.

2.6.3        Depth of application

ESLs apply from the surface to 2 m depth below finished surface/ground level, which corresponds to the root zone and habitation zone of many species. In arid regions, where the predominant species may have greater root penetration, specific considerations may result in their application to 3 m depth.

2.6.4        Soil texture

The ESLs are applicable to coarse and fine textured soils equivalent to coarse-grained soils and fine-grained soils in Table A1 of Standard AS 1726:1993. Conservative Tier 1 values (i.e. values for coarse soils) should be applied where site-specific textural information is not available.

2.6.5        Fresh and aged contamination

ESLs were derived on the basis of fresh contamination. GC-MS analysis and examination of the gas chromatogram output can assist in differentiating between fresh and aged TPH contamination.

 

While aged contamination is generally of less human health and environmental concern, sub-surface conditions can preserve some petroleum hydrocarbons for extended periods of time. Consideration should be given to the realistic risk of material being excavated and causing an exposure risk.

2.7              Sediment quality guidelines

Investigation and screening levels developed for soils should not be applied directly to the assessment of sediments.

 

Interim sediment quality guidelines (ISQG) are available in the Australian and New Zealand guidelines for Fresh and Marine Water Quality  (ANZECC & ARMCANZ 2000) for a number of common metal, metalloid and organometallic contaminants and organics, principally PAHs and organochlorine pesticides (OCPs). The ISQG have limitations relating to the availability of appropriate ecotoxicology data and the small number of species on which they are based.

 

Reference to these guidelines, balanced by consideration of their limitations, may have application in the site-specific assessment of sites where contamination may impact aquatic receptors. Guidance on the sampling of sediments can be found in AS/NZS 5667.12:1999 Guidance on sampling of bottom sediments and Simpson et al. (2005).

2.8              Groundwater investigation levels

Site assessment should consider the risks from contaminated groundwater to all potential receptors on and off the site of origin and potential effects on groundwater resources.

 

The Groundwater investigation levels (GILs) are based on the Australian Water Quality Guidelines 2000 (AWQG), Australian Drinking Water Guidelines 2011 (ADWG) and Guidelines for Managing Risk in Recreational Waters 2008 (GMRRW). The GILs are adopted in the NEPM as investigation levels in the context of the framework for risk-based assessment of groundwater contamination (refer Schedule B6) i.e. levels above which further assessment is required.

 

The AWQG provide tabulated values based on percentage species protection for various aquatic environments and water uses. The appropriate settings for current and potential uses of groundwater need to be identified for the aquifer undergoing assessment. The guideline documents should be consulted for appropriate interpretation of guideline values, in consultation with relevant regulatory authorities if necessary.

 

Table 5.  Groundwater environmental values and guidelines for their protection

Environmental value to be protected

Guidelines to apply

Raw drinking water source

ADWG

Agricultural use – stock watering

AWQG

Agricultural use – irrigation

AWQG

Fresh water aquatic ecosystem

AWQG

Marine water aquatic ecosystem

AWQG

Recreational use

GMRRW

 

The GILs provided in Table 1C at the end of this Schedule, define acceptable water quality for various contaminants at the point of use.  Table 1C provides frequently used values for drinking water and protection of fresh and marine ecosystems. Additional GILs applicable to industrial use (aquaculture), agricultural use (stock watering and irrigation) and recreational waters are provided in the referenced documents.

 

The GMRRW recommend applying a multiplication factor of 10 to 20 to the ADWG for assessment of the acceptability of recreational water quality. GILs for other receptors should be obtained directly from the ‘primary industries’ section of the AWQG where relevant. Note that the recreational and aesthetics sections of the AWQG have been superseded by the GMRRW.

2.9              ‘Management limits’ for petroleum hydrocarbon compounds

In addition to appropriate consideration and application of the HSLs and ESLs, there are a number of policy considerations which reflect the nature and properties of petroleum hydrocarbons:

·         formation of observable light non-aqueous phase liquids (LNAPL),

·         fire and explosive hazards and

·         effects on buried infrastructure e.g. penetration of, or damage to, in-ground services by hydrocarbons.

The CWS PHC includes ‘management limits’ to avoid or minimise these potential effects and these values have been adopted as interim Tier 1 guidance. The values are included in Table 1B(7) at the end of this Schedule. A site-specific assessment (Tier 2 or 3) may be preferred where relevant site-specific information is available.

 

Application of the management limits will require consideration of site-specific factors such as the depth of building basements and services and depth to groundwater, to determine the maximum depth to which the limits should apply.  The management limits may have less relevance at operating industrial sites (including mine sites) which have no or limited sensitive receptors in the area of potential impact. When the management limits are exceeded, further site-specific assessment and management may enable any identified risk to be addressed.

 

The presence of site TPH contamination at the levels of the management limits does not imply that there is no need for administrative notification or controls in accordance with jurisdiction requirements.

 

Further information on the consideration of aesthetics with respect to petroleum hydrocarbons is included in Section 3.6.

3                  Application of investigation and screening levels

3.1              Recommended process for assessment of site contamination

The recommended site assessment process is shown in Schedule A of the NEPM. Refer to Schedule B2 for guidance on site characterisation.

Before comparing site data with investigation and screening levels, it is important that  sufficient and appropriate characterisation of the site is carried out to ensure that the comparison is both meaningful and relevant for assessing potential risks to human health and the environment.

A number of cases studies which illustrate the application of the investigation and screening levels in site assessment are included in Section 5 of this Schedule.

3.2              Tier 1 assessment

A Tier 1 (or screening level) assessment comprises a comparison of representative site data with generic investigation levels and/or screening levels for protection of human health and the environment, together with an assessment of any limitations on their use in relation to site-specific conditions. A Tier 1 assessment provides an initial screening of the data to determine whether further assessment is required.

 

Contaminated sites may contain multiple contaminants in soil and groundwater and the risk posed is affected by site characteristics such as soil properties and the depth to the contamination. The selection of the appropriate investigation and screening levels to apply at a particular site should be determined using professional judgement and with reference to the CSM.

3.2.1        Comparison with investigation and screening levels

No single summary statistic will fully characterise a site and appropriate consideration of relevant statistical measurements should be used in the data evaluation process and iterative development of the CSM (refer to Schedule B2, Section 4).

 

The preferred approach is to examine a range of summary statistics including the contaminant range, median, arithmetic/geometric mean, standard deviation and 95% upper confidence limit (UCL). Further information is provided in Section 11 of Schedule B2.

 

At the very least, the maximum and the 95% UCL of the arithmetic mean contaminant concentration should be compared to the relevant Tier 1 screening criteria. However, where there is sufficient data available, and it is appropriate for the exposure being evaluated, the arithmetic mean (or geometric mean in cases where the data is log normally distributed) should also be compared to the relevant Tier 1 investigation or screening level. The implications of localised elevated values (hotspots) should also be considered. The results should also meet the following criteria:

·         the standard deviation of the results should be less than 50% of the relevant investigation or screening level, and

·         no single value should exceed 250% of the relevant investigation or screening level.

The maximum observed contaminant concentration generally provides a conservative assessment of exposure because if estimated risks from the maximum concentrations are not of concern, then the site should be suitable for use under the CSM considered. However, a maximum concentration may not be representative of the source as a whole and may result in an overestimation or underestimation of risk if the data is extremely limited.

 

The mean contaminant concentration can be a suitable metric provided that it can be shown that it adequately represents the source being considered. It is important that small areas of high concentrations or hot-spots are not ignored by averaging with lower values from other parts of the site. The mean value may be more representative of the source as a whole than the maximum, and may provide a better estimation of the actual concentration that a population would be exposed to over a period of time.

 

The 95% UCL of the arithmetic mean provides a 95% confidence level that the true population mean will be less than, or equal to, this value. The 95% UCL is a useful mechanism to account for uncertainty in whether the data set is large enough for the mean to provide a reliable measure of central tendency. Note that small data sets result in higher values for the 95% UCL. Further guidance on the use of 95% UCLs can be found in NSW DECC (2006), US EPA (2006b) and US EPA (2007a).

 

Groundwater data being used to assess exposure should consider a relevant average at the site or off-site (as appropriate based on the CSM) together with a reasonable maximum based on understanding of seasonal and other trends in groundwater quality. Where trends are poorly defined in the early stages of an investigation, greater weight should be placed on the maximum concentration.

 

If air data or soil vapour data is available for the site, then the use of that data needs to be considered within the context of the CSM and the activities at the site or adjacent to the site that may affect the presence of substances in the air, including confounding substances. Consideration of both a reasonable maximum and a relevant average case should be considered where possible.

 

The effects of applying a multiplication factor to account for biodegradation to soil, soil vapour and groundwater HSLs where relevant should be considered in the data analysis. The data should be evaluated for trends and the presence of hot spots prior to the application of any biodegradation factors.

3.2.2        Exceedence of Tier 1 investigation and screening levels

The magnitude of the exceedence should be considered in the context of the CSM (that is, whether the exposure pathways are plausible and whether exposure will result in harm). In cases of minor exceedence of investigation or screening levels, a qualitative risk assessment may be sufficient to evaluate the potential impact.

 

Where exceedence of Tier 1 investigation and screening levels indicates that there is a likelihood of an adverse impact on human health or ecological values for that site, site-specific health and/or ecological risk assessment (Tier 2 or 3) should be carried out as appropriate. This will usually require the collection of additional site data.

 

Alternatively, appropriate management options may be considered such as engaging with landowners and occupants/site users regarding the nature of the contamination and implementing appropriate site management plans. Guidance on community engagement and risk communication is provided in Schedule B8.

 

The nature of the response should be determined on a site-specific basis and be proportional to the potential risk posed to human health and/or the environment.

3.2.3        Procedure if no generic investigation or screening levels are available

Site-specific investigation levels will need to be developed when:

·         investigation or screening values are not available for the contaminants of concern and/or insufficient data is available for the derivation of generic guideline values

·         site conditions, receptors and/or exposure pathways differ significantly from those assumed in the derivation of the generic investigation or screening levels.

Consult Schedules B4 and B7 for guidance on deriving site-specific HILs and on applying the HIL methodology to derive HILs for additional substances.

 

Consult Schedule B5b for guidance on applying the EIL methodology to derive EILs for additional substances. Schedule B5b Appendix B provides guidance using a method of soil-water partitioning coefficients for deriving EILs that are protective of aquatic ecosystems.

3.3              Specific considerations for  petroleum hydrocarbons

The flowchart in Figure 1 (below) provides a general overview of the application of the HSLs and ESLs for petroleum hydrocarbons including linkage to the ‘management limits’ for TPH contamination. Information on these screening levels can be found in:

Human health concerns

·         HSLs check list – ASC NEPM Toolbox

·         Vapour inhalation pathway – HSLs – Section 2.4

·         Direct contact pathways – HSLs – Section 2.4

·         Consumption of groundwater – GILs – Section 2.8 and Schedule B6

·         HILs – Benzo(a)pyrene, total PAH and lead – Section 2.2 and Schedule B7

·         Aesthetics – Section 3.6

·         ‘Management limits’ – Section 2.9.

Ecological concerns

·         ESLs – terrestrial ecosystems – Section 2.6

·         AQWG – aquatic ecosystems - Section 2.8 and Schedule B6

·         EILs – terrestrial ecosystems - lead – Section 2.5.

 

The application of these screening levels is illustrated by the case studies included in Section 5.

In many cases, sites assessed for petroleum hydrocarbon contamination are driven initially by human health concerns regarding volatile components (F1 and F2). In circumstances where the HSLs are modified by biodegradation factors or where the more volatile fractions are absent, then ecological considerations may become the predominant concern, particularly for the longer chain fractions (F3 and F4).

 

There are many HSLs that are denoted as non limiting or NL (refer Section 2.4.2, footnotes to HSL Tables and Friebel & Nadebaum (2011a)) and high levels of petroleum hydrocarbons, including observable LNAPL, may be present at the site without presenting a risk via the vapour inhalation pathway.  The presence of observable and mobile LNAPL in test pits and bores will require careful consideration of health, environmental, fire and explosive risks and aesthetic concerns.  This presentation of LNAPL may lead to active management depending on the current or proposed site use and the extent of the LNAPL. An immediate response may be required where there is penetration of in-ground services or detectable odours in building interiors.  Dispersed droplets of LNAPL that are relatively immobile (e.g. in a clay-rich soil) that are assessed as low risk may not require active management.

 

Figure 1:         Flowchart for Tier 1 human and ecological risk assessment of petroleum hydrocarbon contamination—Application of HSLs and ESLs and consideration of management limits

 

Notes

1.        The CSM should inform the selection and application of human health and ecological screening levels and management limits. Relevant HSLs, GILs, HILs and EILs (e.g. PAHs and lead) should be considered for sites affected by petroleum hydrocarbons.

2.        The limitations of the screening levels and investigation levels should be considered on a site-specific basis.

3.        Petroleum hydrocarbon ‘management limits’ are used to consider the potential effects of LNAPL-related hazards. Refer to Section 2.9 for more information on depth of application. Jurisdictions may have policies applicable to the presence of LNAPL.

4.        The potential for groundwater contamination and impacts on receptors including groundwater resources should be considered and assessed as appropriate in accordance with Schedule B6 and jurisdictional policies for the protection of groundwater resources.

3.4              Considerations for ecological assessment

3.4.1        General

Schedule A provides an overview of the site assessment process and the application of investigation and screening levels for human health and ecological risk assessment. While protection of human health often drives the first stages of assessment, protection of the environment (terrestrial and aquatic) should be a consideration for all site assessments.

 

In assessing the overall risk to the environment from soil contamination the following site-specific aspects should be considered:

·         the location of the contamination in relation to any on-site and off-site sensitive receptors, e.g. watercourses, estuaries, groundwater resources, sensitive ecological areas

·         the existing or proposed land use(s)

·         the presentation of contaminants including areal extent, depth below finished ground level, the presence of barriers or containment that prevents or minimises the migration of contamination or exposure pathways

·         the in situ leaching characteristics of contaminants of concern and the potential for leachate to adversely affect any accessible sensitive on-site and off-site receptors

·         the potential for contaminants to be transported from the site at levels of concern by erosive forces.

3.4.2        Scope of ecological assessment

The relevance and scope of ecological assessment should be considered early in the development of the conceptual site model and data quality objectives. A pragmatic risk-based approach should be taken in applying EILs and ESLs in residential and commercial/industrial land use settings.

 

Site soils may have poor structure and drainage, low organic content, minimal topsoil depth and a limited ability to support plant growth and soil micro-organisms. In existing residential and urban development sites there are often practical considerations that enable soil properties to be improved by addition of ameliorants with a persistent modifying effect or by the common practice of backfilling or top dressing with clean soil. In other cases, all of the site soils will be removed during site development works or relocated for the formation of new land forms. Sites may also be backfilled with clean soil/fill and the fate of any excavated contaminated soil should be considered in the process.

 

Commercial and industrial sites may have large building structures and extensive areas covered with concrete, other pavement or hardstand materials and may have limited environmental values requiring consideration while in operational use.

3.4.3        Mobility of contaminants

When contamination is in a highly leachable form or is incorporated in exposed readily erodible soil, potentially adverse ecological effects may occur some distance from the contaminant source area. The potential for off-site environmental impacts should be considered in the development of the conceptual site model. Methods for determining leachability are discussed in Schedule B3.

 

It is common for established industrial areas to contain higher levels of soil contamination (such as metals) than surrounding areas.  Receptors and soils immediately adjoining older industrial zones may be affected by the accumulation of soil contaminants caused by migration through subsurface contaminant movement and erosion of contaminated soils.

 

For example, a site with lead (Pb), zinc (Zn) and petroleum hydrocarbon concentrations in soil below EILs and ESLs for commercial/industrial land use (where a 60% or 65% species protection level would apply) would be acceptable for the site use. However, if the site adjoined an area of ecological significance, such as a protected wetland, the site assessment should also consider the possibility that contamination may migrate off-site and impact the wetland where 99% species protection limits would apply.

 

In other cases sites may have aged metals and metalloid contaminants with stable, cohesive soils and low in situ leachability and pose a low risk to the ecosystem.

3.5              Considerations for groundwater assessment

When groundwater from a monitoring well contains levels of contaminants above the appropriate investigation levels (Tier 1 assessment), then further investigation (Tier 2 assessment) is required. This may take the form of consideration of site-specific conditions and circumstances which may result in modification of the generic Tier 1 criteria. If no modification of the Tier 1 criteria is applicable, the assessment proceeds directly to Tier 3 where groundwater concentrations at the point of exposure (point of use) are compared with the generic GILs or site-specific response levels. If this indicates that the investigation levels are exceeded at the point of use, or in the discharge environment of the groundwater, then an appropriate response is required. The relevant guideline documents should be consulted for informed interpretation and application of GILs and modified GILs.

 

Groundwater protection may be a particular concern where contamination occurs in sandy soils containing naturally low levels of organic matter, clay and trace elements. In most situations, soil contaminants at levels below appropriate EILs or HILs do not pose a threat to local groundwater sources. However, possible impacts on groundwater should always be considered particularly for sites impacted by petroleum hydrocarbons and halogenated solvents. In some cases the soil may not reveal contaminants of concern while groundwater is affected.

 

It should be noted that some jurisdictions may have groundwater protection policies that require action even where levels do not exceed the AWQG values at the point of use.

3.6              Aesthetic considerations

3.6.1        Introduction

Aesthetic issues generally relate to the presence of low-concern or non-hazardous inert foreign material (refuse) in soil or fill resulting from human activity. Sites that have been assessed as being acceptable from a human health and environmental perspective may still contain such foreign material. Geotechnical issues related to the presence of fill should be treated separately to assessment of site contamination.

 

Various forms of refuse may be identified in bore or test pit logs, for example fragments of concrete, metal, bricks, pottery, glass, trivial amounts of bonded asbestos-containing-materials, bitumen, ash, green waste, rubber, plastics and a wide variety of other waste materials. These materials commonly occur in former industrial and filled sites. Similarly, construction and demolition waste materials, some of which are inert and non-hazardous, are widely distributed in urban areas.

 

Other sites may have some soil discolouration from relatively inert chemical waste (for example, ferric metals) or residual odour (for example, natural sulphur odour).

 

Care should be taken to ensure adequate site characterisation, particularly when there is a diverse range of foreign material and associated fill and an appreciable risk inferred from site history (or lack thereof) for the presence of hazardous contaminants. For example, some ash fill may contain PAHs and metals, while other ash deposits may contain no contaminants of concern.

3.6.2        Circumstances which would trigger an assessment of aesthetics

The following characteristics or presentations are examples of where site assessment may not have detected contamination above investigation or screening levels but where further assessment would be required:

·         highly malodorous soils or extracted groundwater (e.g. strong residual petroleum hydrocarbon odours, hydrogen sulphide in soil or extracted groundwater, organosulfur compounds)

·         hydrocarbon sheen on surface water

·         discoloured chemical deposits or soil staining with chemical waste other than of a very minor nature

·         large monolithic deposits of otherwise low-risk material, e.g. gypsum as powder or plasterboard, cement kiln dust

·         presence of putrescible refuse including material that may generate hazardous levels of methane such as a deep-fill profile of green waste or large quantities of timber waste

·         soils containing residue from animal burial (e.g. former abattoir sites).

3.6.3        Assessment process for aesthetic issues

There are no specific numeric aesthetic guidelines, however site assessment requires balanced consideration of the quantity, type and distribution of foreign material or odours in relation to the specific land use and its sensitivity. For example, higher expectations for soil quality would apply to residential properties with gardens compared with industrial settings.

General assessment considerations include:

·         that chemically discoloured soils or large quantities of various types of inert refuse, particularly if unsightly, may cause ongoing concern to site users

·         the depth of the materials, including chemical residues, in relation to the final surface of the site

·         the need for, and practicality of, any long-term management of foreign material.

In some cases, documentation of the nature and distribution of the foreign material may be sufficient to address concerns relating to potential land use restrictions.

 

In arriving at a balanced assessment, the presence of small quantities of non-hazardous inert material and low odour residue (for example, weak petroleum hydrocarbon odours) that will decrease over time should not be a cause of concern or limit the use of a site in most circumstances. Similarly, sites with large quantities of well-covered known inert materials that present no health hazard such as brick fragments and cement wastes (for example, broken cement blocks) are usually of low concern for both non-sensitive and sensitive land uses.

 

Caution should be used for assessing sensitive land uses, such as residential, when large quantities of various fill types and demolition rubble are present.

4                  Asbestos materials in soil

4.1              Scope of the guidance

This guidance applies to the assessment of known and suspected asbestos contamination in soil and addresses both friable and non-friable forms of asbestos. Most assessments will involve non-friable bonded forms of asbestos-containing-material (bonded ACM) as this is the most common type of asbestos soil contamination in Australia.

 

This guidance is not applicable to asbestos materials which are:

·         wastes such as demolition materials present on the surface of the land or

·         asbestos materials in buildings or structures including operational pipelines.

Transport and disposal of asbestos-contaminated soil should be carried out in accordance with state and territory legislation and guidelines. Soils that are known or suspected to be contaminated with asbestos should not be reused or recycled at other sites.

 

This guidance deals with assessment but is closely linked to remediation, management and protection of human health.

 

An overview of the assessment of asbestos contamination is presented here. More detailed information on site characterisation can be found in Schedule B2 Section 11 and WA DoH (2009, 2012).

Case studies illustrating the recommended approach for site assessment are included in Section 5.

4.2              Historical use of asbestos in Australia

Bonded asbestos products were first manufactured in Australia in the 1920s and were a common component of residential and commercial building materials from the mid-1940s until the late 1980s.  Up to 90% of the asbestos mined or imported into Australia was used for the manufacture of these building products. Australia banned the use and import of building asbestos products in the mid-1980s and, in December 2003, banned import, manufacture and use of all asbestos products (e.g. automobile products).

 

Asbestos has been used in Australia as a reinforcing agent in cement sheeting for walls and roofs and in cement building products, such as pipes, gutters and flooring. Asbestos was also used in combination with other bonding compounds such as vinyl (e.g. for vinyl floor tiles and sheeting) and resin.  Friable (non-bonded) asbestos products include low-density asbestos fibre board, insulating products such as lagging, sprays and asbestos rope gaskets.

 

Many older homes in all Australian communities still contain asbestos cement products, commonly in eaves or cladding of internal and external walls and roofs. When in good condition, bonded asbestos products do not release asbestos fibres into the air and are considered safe for people who are in contact with them, including when carrying and handling these materials (enHealth 2012). If asbestos materials can be maintained in good condition, enHealth (2005, 2012) recommends that these materials are best left alone and periodically checked to monitor their condition.

4.3              Work Health and Safety

Site assessors should be aware of (and where relevant comply with) the requirements of both national and jurisdictional work health and safety legislation and guidance relating to asbestos and its removal, such as:

·         the national model Work Health and Safety Regulations and related jurisdictional legislation and guidelines

·         How to manage and control asbestos in the workplace Code of Practice (Safe Work Australia 2011a)

·         How to safely remove asbestos Code of Practice (Safe Work Australia 2011b)

·         Code of Practice for the Management and Control of Asbestos in Workplaces (NOHSC: 2018 (2005))

·         Code of Practice for the Safe Removal of Asbestos 2nd edn (NOHSC: 2002 (2005)).

State/territory agencies with responsibility for work health and safety should be consulted for specific guidance on what is required in that state or territory.

 

The final prohibition of asbestos in the workplace came into effect on 31 December 2003 but there are a number of exceptions including:

·         genuine research and analysis

·         sampling and identification in accordance with WHS Regulations

·         where the regulator approves the method adopted for managing risk associated with asbestos.

Safe Work Australia (2011a) provides practical advice on how to manage risks associated with asbestos and asbestos-containing-material (ACM) in the workplace. It provides information on how to identify the presence of asbestos at the workplace and how to implement measures to eliminate or minimise the risk of exposure to airborne asbestos fibres.

 

Work involving asbestos-contaminated soil is permitted providing that a competent person has determined that the soil does not contain any visible ACM or friable asbestos; or if friable asbestos is visible, it does not contain more than trace levels of asbestos determined in accordance with AS4964:2004 Method for the qualitative identification of asbestos in bulk samples.

A competent person is defined in Safe Work Australia (2011a) as a person who has acquired through training, qualification or experience, the knowledge and skills to carry out the task.

A competent person in the context of asbestos and the NEPM is a person who has acquired through training, qualification or experience, the knowledge and skills to identify, investigate and assess asbestos in the context of an environmental site assessment. This includes identifying the potential for asbestos contamination from site history information.

If visible asbestos is present and it may be disturbed during work activities, it must be removed. This includes removing visible fragments of bonded ACM from exposed trench faces and those areas of the site where intrusive works may be carried out (e.g. to install utilities). The removal of visible asbestos should be appropriately managed and full details recorded (this information is required for assessing asbestos concentration in soil – refer Section 4.10). Visible asbestos should be removed prior to excavation/construction works commencing. Consult the relevant Code of Practice for more detailed information.

4.4              Terminology for asbestos contamination in soil

For the purpose of assessing the significance of asbestos in soil contamination, three terms are used in this Schedule which are based on guidance developed by the Western Australian Department of Health (WA DoH, 2009). The equivalent terms used in work health and safety legislation are listed in Table 6:

Table 6 Equivalency of terms used in the NEPM, WA DoH (2009) and Work Health and Safety legislation and guidelines

NEPM  terminology (based on WA DoH 2009)

Work Health and Safety terminology

Bonded asbestos-containing-material or ‘bonded ACM’ (referred to as ACM in WA DoH 2009)

Bonded asbestos/non-friable asbestos

Fibrous asbestos, FA

Non-bonded/friable asbestos

Asbestos fines, AF

Bonded asbestos containing material (bonded ACM)

Bonded ACM comprises asbestos-containing-material which is in sound condition, although possibly broken or fragmented, and where the asbestos is bound in a matrix such as cement or resin (e.g. asbestos fencing and vinyl tiles). This term is restricted to material that cannot pass a 7 mm x 7 mm sieve. This sieve size is selected because it approximates the thickness of common asbestos cement sheeting and for fragments to be smaller than this would imply a high degree of damage and hence potential for fibre release.

Bonded ACM is equivalent to ‘non-friable’ asbestos in Safe Work Australia (2011), which is defined therein as ‘material containing asbestos that is not friable asbestos, including material containing asbestos fibres reinforced with a bonding compound’.

Fibrous asbestos (FA)

FA comprises friable asbestos material and includes severely weathered cement sheet, insulation products and woven asbestos material. This type of friable asbestos is defined here as asbestos material that is in a degraded condition such that it can be broken or crumbled by hand pressure. This material is typically unbonded or was previously bonded and is now significantly degraded (crumbling).

Asbestos fines (AF)

AF includes free fibres, small fibre bundles and also small fragments of bonded ACM that pass through a 7 mm x 7 mm sieve. (Note that for bonded ACM fragments to pass through a 7 mm x 7 mm sieve implies a substantial degree of damage which increases the potential for fibre release.)

From a risk to human health perspective, FA and AF are considered to be equivalent to ‘friable’ asbestos in Safe Work Australia (2011), which is defined therein as ‘material that is in a powder form or that can be crumbled, pulverised or reduced to a powder by hand pressure when dry, and contains asbestos’.

4.5              Occurrence of asbestos contamination in soil

Bonded ACM is the most common form of asbestos site contamination across Australia, arising from:

·         inadequate removal and disposal practices during demolition of buildings containing asbestos products

·         widespread dumping of asbestos products and asbestos-containing fill on vacant land and development sites

·         commonly occurring in historical fill containing unsorted demolition materials.

If identified early, i.e. prior to significant soil disturbance or earth movements, dumping and inadequate demolition practices usually only results in surface (or near surface) distribution of bonded ACM fragments.

 

Mining, manufacture or distribution of asbestos products may result in sites being contaminated by friable asbestos including free fibres. Severe weathering or damage (including by vehicle movements) to bonded ACM may also result in the formation of friable asbestos (comprising fibrous asbestos (FA) and asbestos fines (AF)).

4.6              Asbestos soil contamination and health risk

Asbestos only poses a risk to human health when asbestos fibres are made airborne and inhaled. If asbestos is bound in a matrix such as cement or resin, it is not readily made airborne except through substantial physical damage.

This guidance emphasises that the assessment and management of asbestos contamination should take into account the condition of the asbestos materials and the potential for damage and resulting release of asbestos fibres.

Bonded ACM in sound condition represents a low human health risk. However, both FA and AF materials have the potential to generate, or be associated with, free asbestos fibres. As a result, FA and AF must be carefully managed to prevent the release of asbestos fibres into the air.

 

It is an inappropriate response to declare a site a human health risk on the basis of the presence of bonded ACM alone. However, if the bonded material is damaged or crumbling (that is, it has become friable), it may represent a significant human health risk if disturbed and fibres are made airborne.

 

The site-specific assessment of sites contaminated with asbestos in soil should be aimed at describing the nature and quantity of asbestos present in sufficient detail to enable a risk management plan to be developed for the current or proposed land use. The management plan should address potential scenarios for the relevant land use(s) whereby asbestos fibres may become airborne and pose a human health risk.

4.7              Basis for health screening levels for asbestos in soil

In 2009, the Western Australian Department of Health (WA DoH) released Guidelines for the Assessment, Remediation and Management of Asbestos-Contaminated Sites in Western Australia (WA DoH 2009). The WA DoH guidelines are based on research published by Swartjes & Tromp (2008), which is based on an extensive database of field and simulation trials using both bound and friable asbestos.  The trial results indicated that a soil level of 0.01% for friable asbestos should keep asbestos fibre levels in air below 0.001 fibres per millilitre (f/ml) and probably to around 0.0001 f/ml. This corresponds to a lifetime risk of 10-6 to 10-5 in the exposed population from airborne asbestos fibres using WHO (2005) risk figures for mesothelioma (WA DoH 2009). The Netherlands (Swartjes & Tromp 2008) apply an investigation level of 0.01% weight for weight (w/w) for fibrous asbestos and 0.1% w/w asbestos for non-friable asbestos (i.e. bound asbestos in sound condition) in soil.

 

WA DoH has taken a more conservative approach (by a factor of 10) than the Netherlands to take account of the greater dryness and dust-generating potential of many local soils and the practice of treating all forms of asbestos (e.g. crocidolite, amosite, chrysotile and actinolite) as equivalent in terms of human health risk. The WA guidelines apply screening levels of:

·         0.01% w/w asbestos in soil for ACM (being asbestos in bonded ACM) to residential sites equivalent to land use setting HIL A. Additional criteria are provided for other land uses based on the default exposure ratios of the NEPM (1999)

·         0.001% w/w asbestos in soil for FA and AF for all site uses.

4.8              Health screening levels for asbestos in soil

Health screening levels for asbestos in soil, which are based on scenario-specific likely exposure levels, are adopted from the WA DoH guidelines and are listed in Table 7.

 

There are various acceptable means to provide confidence that the soil surface is free of visible asbestos including, but not limited to, multi-directional raking of soil to about 10 cm depth and hand-picking of asbestos fragments or covering with a durable hard cover. The requirement for the soil surface to be free of visible asbestos applies to both assessment and remediation phases.

Refer to sections 4.10 and 4.11 for guidance on determining asbestos concentration in soil and comparison with these screening levels.

Table 7. Health screening levels for asbestos contamination in soil

 

Health Screening Level (w/w)

Form of asbestos

Residential A1

Residential  B2

Recreational C3

Commercial/

Industrial D4

Bonded ACM

0.01%

0.04%

0.02%

0.05%

FA and AF5

(friable asbestos)

0.001%

All forms of asbestos

No visible asbestos for surface soil

 

1.        Residential A with garden/accessible soil also includes children’s day care centres, preschools and primary schools.

2.        Residential B with minimal opportunities for soil access; includes dwellings with fully and permanently paved yard space such as high-rise buildings and apartments.

3.        Recreational C includes public open space such as parks, playgrounds, playing fields (e.g. ovals), secondary schools and unpaved footpaths.

4.        Commercial/industrial D includes premises such as shops, offices, factories and industrial sites.

5.        The screening level of 0.001% w/w asbestos in soil for FA and AF (i.e. non-bonded/friable asbestos) only applies where the FA and AF are able to be quantified by gravimetric procedures (refer Section 4.10). This screening level is not applicable to free fibres.

4.9              Process for assessment of asbestos contamination

The recommended general process for assessment of site contamination, including for assessment of asbestos, is shown in Schedule A to this NEPM. The process starts with a Preliminary Site Investigation (PSI), which may lead to a Detailed Site Investigation (DSI). Depending on the site-specific circumstances and the proposed remediation approach, conservative management of presumed asbestos contamination may avoid the need for a DSI. Where remediation is required, appropriate validation sampling should be carried out to verify the effectiveness of the measures undertaken.

 

It is important to note that inadequate sampling strategies and/or inadequate documentation, rather than lack of accuracy in the adopted analytical methods, characteristically limit the effective evaluation of sites contaminated with asbestos.

 

Further information on the recommended assessment process is provided in Schedule B2.

 

A DSI is not necessary where there is a high degree of confidence that the asbestos contamination is confined to bonded ACM in superficial soil, i.e. the site history can be established with confidence and this clearly indicates that there is no reason to suspect buried asbestos materials and the site inspection confirms that any bonded ACM is in sound condition and only present on the surface/near surface of the site. In these circumstances the assessment can proceed directly to remediation (removal of bonded ACM fragments and ensuring that the soil surface is free of visible asbestos) and validation.

4.10          Determining asbestos in soil concentrations

Bonded ACM is the most common and the most readily quantifiable form of asbestos soil contamination due to its ease of visual detection. Where site circumstances are favourable, bonded ACM in sound condition can be used as the primary means of estimating contamination by subjecting soil samples to on-site sieving and gravimetric procedures as described below.

 

Assessment of bonded ACM is the recommended measure for total asbestos contamination where FA and AF (derived from bonded ACM only) are not likely to be significant as established by the PSI including the site inspection (as a guide, this may be taken to be where FA and AF are likely to make up less than 10% of the total amount of asbestos present).

 

Important considerations in determining asbestos concentrations in soil include:

·         observations and calculations of surface asbestos occurrence/distribution should be recorded on a grid system (a grid of up to 10 m x 10 m is generally reasonable when large surface areas are impacted, however, non-impacted soils should be excluded from calculations to avoid dilution effects)

·         where more than one distinct fill unit or soil stratum/unit is impacted by asbestos materials, separate asbestos determinations should be made for each stratum/unit

·         averaging asbestos concentrations across all soils at a site is not appropriate

·         for sub-surface samples, (e.g. boreholes and trenches) the calculation should be carried out per sample (i.e. not averaged over a grid square)

·         the statistical procedures outlined in Section 3.2 (such as comparing mean concentrations with the screening level and no individual sample concentration exceeding 250% of the screening level) are not appropriate for asbestos

·         a weight-of-evidence approach (refer 4.11), which takes into account field observations and methodology and relevant site history findings (e.g. location and nature of fill and demolished buildings etc.)’ is recommended for determining whether individual or adjacent samples exceeding the relevant screening levels are of concern.

Asbestos in soil concentration by gravimetric approach

Guidance on recommended sampling methods is given in Schedule B2 and is based on the WA DoH guidelines (2009).

 

The asbestos concentration calculations are based on the amount of asbestos equivalent (i.e. asbestos in asbestos-containing-materials) in a measured/estimated amount of soil, expressed as a % weight for weight. The soil volume may be one or more individual 10 L samples from specific soil units or the area of a grid square multiplied by the investigation depth for raking and tilling methods (refer Schedule B2).

 

As outlined in enHealth (2005), the quantity of asbestos in soil may be estimated as follows:

 

%w/w asbestos in soil =   % asbestos content x bonded ACM (kg) /soil volume (L) x

soil density (kg/L)

 

In the example included in enHealth (2005) it was assumed that:

% asbestos content (within bonded ACM) = 15% and soil density (for sandy soils) = 1.65 kg/L

More representative results for asbestos concentration in soil can be calculated if the parameter values are analysed rather than assumed.

 

The assumption of 15% asbestos by weight in bonded ACM for sites contaminated with cement bonded ACM only is acceptable because typical compositions for bonded ACM products used in Australia are 10-15% asbestos by weight. However, other bonded products may contain much larger proportions of asbestos, e.g. asbestos vinyl floor tiles may contain 8-30% asbestos (Workplace Health and Safety Queensland, 2011). The likely presence of bonded materials other than cement products should be addressed in the PSI and site inspection.  If found during sampling, the calculation will need to be adjusted either by making a conservative assumption or based on laboratory analysis of representative material from the site.

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