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Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey Remediation Action Plan - Petroleum Hydrocarbons in Areas SQ0335 and SQ0117 June 2013

Department of Defence

Parsons Brinckerhoff Australia Pty Limited ABN 80 078 004 798

Level 15 28 Freshwater Place Southbank VIC 3006 Australia Telephone +61 3 9861 1111 Facsimile +61 3 9861 1144 Email [email protected]

Certified to ISO 9001, ISO 14001, AS/NZS 4801 A GRI Rating: Sustainability Report 2011 2171372A-RPT-008-B1

2171372A-RPT-008-B1

Revision Details Date Amended By A1 Original 17 May 2013 E Storr

A2 PB Revision 27 May 2013 D Hirth

A3 PB Revision 28 May 2013 J Thrupp/D Hirth

B1 Final 7 June 2013 D Hirth

©Parsons Brinckerhoff Australia Pty Limited [2013].

Copyright in the drawings, information and data recorded in this document (the information) is the property of Parsons Brinckerhoff. This document and the information are solely for the use of the authorised recipient and this document may not be used, copied or reproduced in whole or part for any purpose other than that for which it was supplied by Parsons Brinckerhoff. Parsons Brinckerhoff makes no representation, undertakes no duty and accepts no responsibility to any third party who may use or rely upon this document or the information.

Author: Elyse Storr ......................................................................................

Signed: ........................................................................................................

Reviewer: Daniel K. Hirth ................................................................................

Signed: ........................................................................................................

Approved by: Jeff Thrupp .....................................................................................

Signed: ........................................................................................................

Date: 7 June 2013 ....................................................................................

Distribution: Department of Defence, Parsons Brinckerhoff file ........................

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Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey Remediation Action Plan - Petroleum Hydrocarbons in Areas SQ0335 and SQ0117

PARSONS BRINCKERHOFF 2171374A-RPT-008-B1 Page i

Contents Page number

Executive summary v

1. Introduction 1

1.1 Background 1

1.2 Objective 1

1.3 Scope of works 1

2. Site background information 3

2.1 Site location 3

2.2 Historical land use 3

2.3 Timeline of environmental investigations 3

2.3.1 1991 3 2.3.2 2009 4 2.3.3 2010 4 2.3.4 2011 5 2.3.5 2012 5 2.3.6 2013 6

3. Summary of contamination and potential health risk 9

3.1 Contaminant of interest 9

3.2 Other contaminants of concern 9

3.3 Extent of PSH impacts 9

3.3.1 PSH 9 3.3.2 PSH contaminant mass 10

3.4 Previous natural attenuation monitoring 11

3.5 Potential human health risks 11

3.6 Data gaps and uncertainties 11

4. Site conceptual site model 13

4.1 Site Conceptual Model summary 13

4.1.1 Groundwater flow paths 13 4.1.2 Groundwater extraction 14 4.1.3 Streams 14

4.2 PSH Site Conceptual Model 15


Page ii 2171374A-RPT-008-B1 PARSONS BRINCKERHOFF

Contents (Continued)

Page number

5. Remediation goals and strategy 17

5.1 Regulatory Framework 17

5.2 Remediation objectives 17

5.2.1 Cleanup Goals 17 5.3 Remediation strategy 18

5.3.1 ROFS strategy summary – Petroleum Hydrocarbons in soil 18 5.3.2 ROFS strategy summary – Petroleum Hydrocarbons in groundwater 19

6. Remediation approach 21

6.1 Preliminaries 21

6.1.1 Health, environment and safety plan 21 6.1.2 Notable waste disposal requirements 22

6.2 PSH source area remediation 22

6.2.1 UST decommissioning and removal 22 6.2.2 Excavation of secondary impacts to the extent practical 23 6.2.3 Natural source zone depletion after clean-up to the extent practical 23

6.3 Petroleum Hydrocarbons in groundwater 24

6.3.1 Multi-phase extraction (MPE) 24 6.3.2 Monitored Natural Attenuation after clean-up to the extent practical 25

7. Contingency management 31

7.1 PSH Source Area Remediation 31

7.2 Petroleum Hydrocarbons in groundwater 32

8. References 35

9. Limitations 37


PARSONS BRINCKERHOFF 2171374A-RPT-008-B1 Page iii

List of tables Page number

Table 6.1 Data quality indicators 28 Table 7.1 Contingencies for PSH source area remediation options 31 Table 7.2 Contingencies for petroleum hydrocarbon remediation options 32

List of figures Page number

Diagram 4.1 Conceptual hydrogeologic cross-section diagram 13

Appendices Appendix A Figures Appendix B Relevant ROFS Tables (PB 2013c)


PARSONS BRINCKERHOFF 2171374A-RPT-008-B1 Page v

Executive summary

Parsons Brinckerhoff Australia Pty Ltd (Parsons Brinckerhoff) has been retained by the Department of Defence, Defence Support and Reform Group (DSRG, referred to hereafter as Defence) as Lead Consultant (AZ5293) to provide a remediation action plan for phase separated hydrocarbons (PSH) and dissolved petroleum hydrocarbons at the Army Aviation Centre Oakey (AACO) – Southern Queensland Region, Areas SQ0335 and SQ0117 (Areas C1 and C2).

The objective of the Remediation Action Plan (RAP) is to define an approach and methodology to remove, control or eliminate phase separated hydrocarbons (PSH) and dissolved phase hydrocarbons to levels which are considered safe for human health and the environment. The proposed RAP methods were based on recommendations of the ROFS report (PB 2013c) which screened all applicable technologies with respect to technical feasibility, financial considerations, logistical constraints, on-going management requirements and timing

Remediation goals

The general cleanup goals for hydrocarbons in groundwater are as follows:

Source area remediation of PSH in unsaturated soil beneath failed infrastructure in Area C1.

Mitigation of risk from PSH migration off-site.

Mitigation of risk from dissolve phase hydrocarbon impacts to water supply wells, offsite groundwater and surface water bodies.

Specific soil remediation goals were set to achieve source area hydrocarbon concentrations consistent with adopted national guideline criteria.

Specific groundwater remediation goals for hydrocarbons that manage potential risks to groundwater users have been nominated:

No lateral PSH or dissolved phase hydrocarbon migration beyond Areas C1 and C2 (a compliance boundary indicative of significant plume migration requiring further action).

No dissolved phase hydrocarbon impacts to water supply wells or off-site groundwater.

Petroleum Hydrocarbon Source Area Remediation

The most cost effective means to remediate hydrocarbons in the source area (UST C60) has been identified to be UST and interceptor trap removal, shallow soil excavation followed by natural source-zone depletion for areas which cannot be readily accessed. This combination of activities represents clean-up to the extent practical, given the remediation goals.


Page vi 2171374A-RPT-008-B1 PARSONS BRINCKERHOFF

Petroleum Hydrocarbons in Groundwater Remediation

Consideration of vacuum enhanced recovery for residual PSH in the source area is to be tested in a pilot-trial in order to eliminate a data gap. The contingency for multi-phase extraction is natural attenuation monitoring of PSH and dissolved phase hydrocarbons. Given the nature of site soils and depth to groundwater, extractive pumping technologies are not expected to be viable. Based on the apparent plume stability and review of human health risks for Areas C1 and C2, monitored natural attenuation (MNA) will be pursued as the most cost effective strategy. MNA contingency triggers and measures have been establish to control and mitigate any potential risks.


PARSONS BRINCKERHOFF 2171374A-RPT-008-B1 Page 1

1. Introduction

1.1 Background

Parsons Brinckerhoff Australia Pty Ltd (Parsons Brinckerhoff) has been retained by the Department of Defence, Defence Support and Reform Group (DSRG, referred to hereafter as Defence) as Lead Consultant (AZ5293) to provide a remediation action plan for phase separated hydrocarbons (PSH) at the Army Aviation Centre Oakey (AACO) – Southern Queensland Region, Areas SQ0335 and SQ0117. The AACO was renamed as the Swartz Barracks during 2011; however, it will be referred to as AACO for reporting purposes to provide continuity.

Areas C1 (SQ0335) and C2 (SQ0117), as defined by URS (2010), are aircraft maintenance areas where underground storage tanks have been report to have leaked (Intelara 2009).

1.2 Objective

The objective of the Remediation Action Plan (RAP) is to define an approach and methodology to remove, control or eliminate phase separated hydrocarbons (PSH) and dissolved phase hydrocarbons to levels which are considered safe for human health and the environment. Site-specific clean-up goals are described in Section 5.2.1.

The Remediation Options Feasibility Study (PB 2013c) considered known potential remedial options that may be applied at AACO. All technologies considered were screened with respect to technical feasibility, financial considerations, logistical constraints, on-going management requirements and timing. The recommendations of the ROFS report provided preferred solutions for the remediation of PSH and dissolved hydrocarbons in Areas C1 and C2.

1.3 Scope of works

In general, the PSH RAP is to provide a defined strategy for hydrocarbon impacts in Areas C1 and C2, which would be suitable for defining a future request for tender. The RAP scope of works includes:

a summary of the site condition and surrounding environment;

a summary of the contamination status of the relevant site area (C1 and C2)

assessment of data gaps that may require further investigation;

identification of remediation goals and approach;

site management issues;

contingency management; and

occupational health and safety issues.



2. Site background information

2.1 Site location

The Queensland town of Oakey is located approximately 3 km to the south of the AACO (Figure 1, Appendix A). The land use surrounding the AACO is predominantly agricultural (Rural – R1 planning scheme designation) with the exception of rural residential properties (RR1, Precinct 1 planning scheme designation) and Oakey Showgrounds (council land) to the south and south west. All surrounding properties are within the Toowoomba Regional Planning Scheme. The R1 designation has a 100 hectare minimum lot size, and the RR1 designation has a 4,000 square metre minimum lot size.

Over 2,000 personnel may be present at the site, including Australian Defence Force (ADF) members, civilian Defence employees, civilian logistics and support staff, and members of the Republic of Singapore Air Force. A portion of the site is also used as an aircraft museum that is open to the public. A small and variable percentage of personnel reside on site, where there are food and recreation facilities, including a swimming pool. A large portion of land in the northwest of the airfield is leased for agricultural production (eg. corn, cotton). The agricultural production lies within the AACO perimeter fence (yellow dashed line, Figure 2, Appendix A), but outside the internal airfield security fence (green dashed line, Figure 2, Appendix A). Historical crop types are not known, but crop rotation is expected.

2.2 Historical land use

Based on previous Phase 1 Environmental Site Assessments, the AACO site has been utilised as a military and civilian airport since the 1940s (URS 2010). During World War II, the site was occupied by the Royal Australian Air Force (URS 2010). From 1948 to 1969 the site was used as a civilian airfield, after which, Defence purchased the site for use as AACO (URS 2010). The site has been and is still used for the maintenance of aircraft, fuelling of aircraft and vehicles, as well as other potential polluting military and industrial activities (eg. waste lagoon, landfill, fuel underground storage tanks (USTs), waste hydrocarbon USTs, fire training areas and interceptor traps).

2.3 Timeline of environmental investigations

A summary of the previous environmental investigations that are relevant to this RAP is provided below, where information is known to Parsons Brinckerhoff:

2.3.1 1991

Army Pollution Audits – Queensland, Volume 2, Detailed Report, Kinhill Engineers Pty Ltd 1991.

A site inspection identified a recently installed 1,000L waste oil tank in Area C1 for the collection of hydraulic oil, detergent and fuel. A deficiency was noted that the tank levels were checked manually at the request of the disposal company, and that this could lead to


Page 4 2171374A-RPT-008-B1 PARSONS BRINCKERHOFF

tank overflows. Likewise, a leak would not likely be detected without routine on-site tank monitoring. The report went on to note that substantial ground movements were noted to occur at the site, where cracking of pipes had occurred. A deficiency was noted that specific design measures were required to prevent rupture or disconnect from the Building C2 waste oil UST.

2.3.2 2009

Oakey Base – Buildings C2 oil separator and storage – Report on probable leak and ground contamination, Intelara Engineering, March 2009.

An investigation of potentially leaking infrastructure was organised by Spotless on behalf of Defence. Reports of oil flowing into the oil-water separator outlet connection and oil floating in the adjacent aqueous fire fighting foam (AFFF) storage tank were investigated. Both underground tanks were found to be constructed of reinforced concrete. The causes of the oil ingress were suggested to be caused by subsidence related oil-water separator chamber and pipe cracking, as well as a faulty pipe seal on the AFFF tank. The faulty seal would allow oil that had leaked from the oil-water separator to ingress into the AFFF tank, and may have allowed AFFF waste water to leak into the ground when fluid levels were sufficiently high.

The report recommended the replacement of the oil separator and associated piping from the Building C2 boundary. It also recommended the installation of new connections on the eastern side of the AFFF tank. No recommendations were stated for remediation of the adjacent soil.

2.3.3 2010

Stage 1 and Stage 2 Environmental Investigation at Army Aviation Centre, Oakey, Queensland. URS Australia Pty Ltd, 14 October 2010.

The Stage 1 desktop assessment by URS assessed the potential risks associated with historical and current activities conducted on the AACO by using the Contamination Risk Assessment Tool (CRAT) based on newly established areas of investigation. The area designations are used by subsequent investigations by Coffey and Parsons Brinckerhoff.

As part of the Stage 2 investigation, a total of 17 monitoring wells were installed in the Stage 2 investigation. Results of the well sampling investigation identified PSH in three wells within Area C1. The maximum PSH thickness was measured to be 0.6m. Groundwater impacts by petroleum hydrocarbons exceeded the investigation levels in four areas (C1, C2, C3 and F1). AFFF containing perfluorinated compound (PFC) impacts to groundwater in excess of the investigation levels were identified in 6 wells within Area C1, and 6 wells in Area F1. The PFC constituents of concern are perfluoroctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).

URS noted that two irrigation bores were in operation on-site for the purposes aircraft washing, irrigation and fire training purposes. They also noted that a council bore (36603) was located approximately 900m southwest of the impacted areas.

The report recommended additional assessment of activity areas relating to World War II era land use, as well as analytical testing of the closest hydraulically down-gradient extraction bores.



2.3.4 2011

Stage 2, Part 2 Environmental Investigation Army Aviation Centre Oakey. Coffey Environments Australia Pty Ltd, 9 August 2011.

Coffey advanced 75 soil bores and conducted a groundwater monitoring event utilising 82 wells. Dissolved phase hydrocarbon impacts to groundwater were identified in Areas C1, C2 and C3. Kerosene-like PSH was identified in five monitoring wells up to 2.8m thick. Laboratory analysis confirmed the PSH specific gravity (SG 0.80) and a composition similar to kerosene or jet fuel. Shallow soil impacts of hydrocarbons were not observed, thus a source area for PSH impacts in groundwater could not be identified. A total of 11 of 14 groundwater samples analysed for PFCs exceeded the investigation levels. A source area for PFCs in groundwater was not identified, and delineation of PFC extent was not achieved.

The report recommended removal of faulty underground infrastructure, as identified by Intelara Engineering (2009). The report also recommended investigation of storm water drains for the potential of off-site PFC transport in sediments. It also recommended a human health risk assessment and investigation of on-site extraction bores be conducted.

The CRAT was revised to list Area C1 as the only ‘very high risk’ region of the site.

2.3.5 2012

Environmental Investigation - Stage 3 Risk Assessment and Remediation Design, Army Aviation Centre Oakey (AACO), Parsons Brinckerhoff, August 2012.

A total of 32 monitoring wells were assessed to confirm the extent of PFCs. A lesser number of samples were collected to assess TPH, metals, volatile organic compounds, semi-volatile organic compounds, organochlorine pesticides, PCBs, phenols, and natural attenuation parameters. Results indicated the presence of PFCs and TPH, with similar concentrations and distribution in groundwater to the Coffey (2011) report. There were no new contaminants of concern identified in groundwater.

Significantly elevated PFOS and PFOA impacts were also recorded in Area C3, Area C1 and Area S1. Delineation of the PFC plume in groundwater was not achieved to the west and south.

PSH was identified at three locations up to 3.6m thick. PSH characterisation was performed in Area C1 that confirmed the Coffey (2011) specific gravity measurements and verified that the PSH consisted of aviation fuel only, with no other petroleum products present. PSH bail-down tests were conducted at locations MWC1-B and MWC1-D, which enabled the calculation of PSH transmissivity of 0.00020m2/day and 0.00017m2/day, respectively.

One aquifer test was completed in Area C1 at location MWC1-I provided a hydraulic conductivity rate of 2.6x10-5 cm/sec.



2.3.6 2013

Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey - Groundwater Monitoring Event, December 2012, Parsons Brinckerhoff, February 2013

The primary objective of the groundwater monitoring event was to assess the environmental conditions of groundwater utilising the existing monitoring well network.

Jet fuel impacts

The presence of jet fuel as light non-aqueous phase liquids (LNAPL) was observed in 5 wells in Area C1. The apparent PSH thickness of approximately 3.1 m is greatest at MWC1-F, near the dis-used waste fuel storage tank and interceptor trap. The distribution of LNAPL appears to be consistent with previous observations since 2009. The LNAPL appears to be relatively immobile.

Dissolved phase hydrocarbons associated with the jet fuel include TPHs, benzene and naphthalene in excess of the adopted guidelines. The extent of dissolved phase impacts is limited to the upper alluvial aquifer in the central part of Area C1, and is consistent with previous assessments. The monitoring well MWC1-I is located approximately 100m down hydraulic gradient of the LNAPL in the direction of irrigation bore 35453. Dissolved phase hydrocarbons were not detected at well MWC1-I, which indicates that natural attenuation (low hydraulic conductivity, low PSH transmissivity and biodegradation) has a significant role in limiting the migration of LNAPL and dissolve jet fuel.

Water Supply System Assessments

Several water supply bores used for irrigation (four wells) were identified on-site and assessed for chemical impacts. While PFCs were identified, no petroleum hydrocarbons were detected.

A water supply bore owned by Toowoomba Regional Council (36603) is located approximately 10m west of monitoring location MWA4-A. The laboratory results from well MWA4-A indicated the presence of PFCs in the groundwater, but no petroleum hydrocarbons were detected.

Human Health Risk Assessment, Petroleum Hydrocarbons in Areas C1 and C2 – Stage 3 Risk Assessment and Remediation Design, Army Aviation Centre Oakey, May 2013

The objective of the Human Health Risk Assessment (HHRA) was to assess the potential for unacceptable risks to human health following the:

inhalation of vapours, emitted from petroleum hydrocarbons in soil and/or groundwater by Defence staff in Areas C1 and C2 of the site

inhalation of vapours, emitted from petroleum hydrocarbons in soil and groundwater, by Defence maintenance contractors in a shallow trench in Areas C1 and C2 of the site

direct contact with petroleum hydrocarbons in soil by Defence staff, including Defence maintenance contractors in a shallow trench in Areas C1 and C2 of the site.

A screening approach was adopted for the HHRA and comprised comparison of reported residual petroleum hydrocarbons impacts in soil and groundwater to the CRC CARE Health



Screening Levels (HSLs) for Petroleum Hydrocarbons in Soil and Groundwater (Friebel and Nadebaum, 2011).

The HHRA indicated that residual contaminants of concern impacts in soil and groundwater were below the adopted HSLs. Therefore, based on the information available it was concluded that petroleum hydrocarbons identified by URS (2010), Coffey (2011) and Parsons Brinckerhoff (2012; 2013) in soil and groundwater in Areas C1 and C2 at the site do not pose any unacceptable health risks to onsite Defence staff including Defence maintenance contractors in a shallow trench. This is based on the assumption of a commercial/industrial setting, excluding a basement car park.

As human health risks from identified petroleum hydrocarbon contamination in soil and groundwater in Areas C1 and C2 were concluded to be acceptable.

Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey, Remediation Options Feasibility Study, Preliminary Final 2013.

Part of the scope of the Remedial Option feasibility Study was specified to address hydrocarbons in relation to Area C1 and C2. A summary of the findings relevant to hydrocarbon remediation is presented below:

Petroleum Hydrocarbon Source Area Remediation

It is recommended to include soil excavation with infrastructure removal (underground storage tank and oil separator) in the Remedial Action Plan. Natural source zone depletion will be considered for the unsaturated soil zone between 3.0m below ground level and the water table at approximately 15m below ground level.

Petroleum Hydrocarbons in Groundwater Remediation

Given the low cost of a short-term mobile multiphase extraction (MMPE) equipment, it is recommended that a remediation trial is conducted in Area C1 as part of the Remedial Action Plan to determine the hydraulic and vacuum radius of influence, as well as potential for MMPE use in the area immediately adjacent to the underground storage tank.

Since it is uncertain that multiphase extraction will be feasible at the site, the remedial action plan will also consider natural source zone depletion of the residual PSH mass in groundwater with monitored natural attenuation of the dissolved phase plume. The low PSH transmissivity, observed PSH and dissolved hydrocarbon plume stability indicate that monitored natural attenuation is feasible at the site.



3. Summary of contamination and potential health risk

3.1 Contaminant of interest

The Parsons Brinckerhoff Initial Environmental Assessment report (PB 2012a) confirmed the ongoing presence of jet fuel in upper alluvial aquifer near the Blackhawk helicopter maintenance area (Areas C1 and C2, Figure 2 in Appendix A).

The presence of free-phase jet fuel in groundwater at AACO is the result of leaking waste fuel infrastructure located underground. F-34 jet fuel is stored in large above ground fuel tanks and transferred through underground piping and fuel trucks at the airport. F-34 jet fuel is a military kerosene-type aviation turbine fuel with Fuel System Icing Inhibitor (FSII). FSII is a glycol ether-based compound that is considered unlikely to pose a risk to the environment due to its miscibility in water, biodegradability and low concentration in F-34 fuel (less than 0.15%).

Waste fuel from the Blackhawk maintenance hangar is collected in an interceptor trap and underground storage tank (UST) located within Area C1 (Figure 2, Appendix A). This infrastructure has been identified as the most probable source for jet fuel in groundwater. Upon inspection of the Area C1 (Building C2) waste fuel infrastructure on 13 March 2009 by Intelara Engineering, the use of the tank allegedly ceased (Intelara 2009).

3.2 Other contaminants of concern

Since the site has been in operation as a military base and civilian airport since the 1940s, there have been many different organic and inorganic chemicals utilised at the site. Other potential contaminants of concern include PFCs in AFFF, auto diesel, auto petrol (unleaded (ULP) and leaded (LP)), motor oil, waste oil, solvents, asbestos, unexploded ordinance, paints and metals.

The current and previous investigation of these potential contaminants of concern has not identified significant exceedances of adopted assessment criteria for these chemicals, excluding PFCs. PFCs are known to exist in Areas C1 and C2 and have been subject to further environmental investigation.

3.3 Extent of PSH impacts

3.3.1 PSH

The extent of PSH impacts subject to this RAP is located within Area C1 and C2. The soil and water impacts are primarily restricted beneath the Area C1 parking lot south of Buildings C1 and C2 (Figure 3, Appendix A). Groundwater flow direction and contaminant transport is generally in a westward direction.



3.3.1.1 Transmissivity

Based on review of the PSH bail-down data (PB 2012a), the tested wells were considered to have reliable data. PSH transmissivity of bore MWC1-B is 0.0021 ft2/day (0.00020 m2/day) and bore MWC1-D is 0.0018 ft2/day (0.00017 m2/day). All PSH transmissivity calculations were less than the recently published limits of hydraulic recoverability. A publication by the Interstate Technology and Regulatory Council (ITRC) indicated that a minimum transmissivity of 0.1 to 0.8 ft2/day (ITRC 2009) was required to make hydraulic recover and effective option.

All wells tested for PSH transmissivity returned values below the lower-bound end of the range provided in the literature. The PSH transmissivity values indicate that PSH in the tested wells cannot be efficiently removed by aggressive recovery methods (eg. pump and treat, dual phase groundwater extraction).

This conclusion is consistent with the groundwater aquifer tests that indicated a groundwater hydraulic conductivity of 8.1 m/year (2.6x10-5cm/sec) at MWC1-I. The groundwater hydraulic conductivity indicates a relatively poor aquifer with semi-pervious permeability in the upper alluvial aquifer.

3.3.1.2 Physical characteristics and characterisation

The results of the PSH characterisation (PB 2012a) indicate the presence of a highly refined fuel similar to kerosene with aliphatic and aromatic compounds primarily in the range of TPH C9-C15. No secondary PSH impacts from lubricants, oils or auto fuels were identified. The range of detected hydrocarbon chains lengths and consistent specific gravity (0.80) indicates that the fuel is likely to be F-34 jet fuel, kerosene-type aviation fuel.

The dynamic viscosity of the PSH samples was noted to be slightly higher than 1.0 cP, which is the dynamic viscosity of water. As the maximum kinematic viscosity for readily available passive PSH skimmers is 4cST (approximately 1.25 cP), this indicates that hydrocarbons in this location are physically capable of being pumped, skimmed or passing through permeable PSH recovery membranes (QED 2013).

3.3.2 PSH contaminant mass

The volume of jet fuel that leaked into soil is not known. The operation of the oil separator and UST ended prior to 2009, but the period of operation is unknown. In order to estimate the volume of PSH in the soil and groundwater, the American Petroleum Institute (API) Interactive LNAPL Guide version 2.0.4 software (February 2006) was utilised in the ROFS (2013c).

The API Saturation and Volume Model outputs included:

PSH saturation of up to 28%

contaminant mass of 207,074 kg, which equates to approximately 259,000 litres of jet fuel

residual contaminant mass of 101,047 kg, which equates to 126,000L of jet fuel. Residual mass means the saturation (vol. of NAPL/vol. of voids) at which the NAPL becomes discontinuous and is immobilized by capillary forces under ambient groundwater flow conditions” (Adamski et al 2003); and,



calculated plume velocity (PSH) of 0.5 m/year.

3.4 Previous natural attenuation monitoring

Previous groundwater assessments have noted a very small dissolved phase hydrocarbon plume in the upper alluvial aquifer, immediately down hydraulic gradient of the PSH. The small dissolved phase plume suggests that significant natural attenuation is present. Secondary lines of evidence for biodegradation based on the observed field measurements of dissolved oxygen and oxidation-reduction potential (ORP) suggest that aerobic degradation may be active on the periphery of the LNAPL plume (PB 2013a). The ORP in the centre of the plume is slightly anaerobic which may be indicative of some anaerobic hydrocarbon degradation. Methane was assessed at location MWC1-C (PB 2012a) which indicated methanogenic biodegradation was occurring within and adjacent to the PSH impacted portion of the groundwater plume. Analysis of nitrate and sulphate at locations MWC1-C and MWC1-I (PB 2012a) indicated that nitrate and sulphate reducing bacteria may also be present and are likely to be biodegrading the dissolved phase hydrocarbons originating from the PSH.

3.5 Potential human health risks

The HHRA (PB 2013b) in May 2013 indicated that residual contaminants of concern impacts in soil and groundwater were below the adopted HSLs. Therefore, based on the information available it was concluded that petroleum hydrocarbons identified by URS (2010), Coffey (2011) and Parsons Brinckerhoff (2012a; 2013b) in soil and groundwater in Areas C1 and C2 at the site do not pose any unacceptable health risks to onsite Defence staff including Defence maintenance contractors in a shallow trench. This is based on the assumption of a commercial/industrial setting, excluding a basement car park. As human health risks from identified petroleum hydrocarbon contamination in soil and groundwater in Areas C1 and C2 have been concluded to be acceptable.

3.6 Data gaps and uncertainties

It is not known as to the extent of time that the jet fuel has leaked. The length of the period of operation for the oil separator and UST is approximately 1991 to 2009. Whether or not the UST is entirely empty is not known, therefore it cannot be confirmed that the leaking of waste fuel has ceased. Unpublished defence records from historical site waste management inspections have indicated that the current UST (C60) and interceptor trap may have replaced two 5,000L waste oil tanks at this location. The period of use and fate of the two USTs is not known. It is likely that these tanks may have been in the locations of the AFFF UST (C59) and the waste oil UST (C60).



4. Site conceptual site model

4.1 Site Conceptual Model summary

4.1.1 Groundwater flow paths

The groundwater at the site is part of the Oakey Alluvial Aquifer system which consists of sandy clays that grade to sandy gravels with clay at a depth of approximately 19m below ground surface (BGS). The water table is typically 14.5m below ground level at the site. The upper alluvial aquifer typically exists from 14.5 mBGS to 19 mBGS at the site. In six locations a thin, discontinuous alluvial aquifer (perched aquifer) has been identified at depths varying from 3.3 mBGS to 12.3 mBGS. The discontinuous perched aquifer is a likely result of recent groundwater recharge or utility seepage where the vertical infiltration may be slowed by clay lenses or variably compacted fill material. The perched groundwater is considered separately from the upper alluvial aquifer, and is not considered to be a productive useable aquifer.

The lithology of the lower alluvial aquifer is not well understood due to limitations of drilling methods. It appears that there are discrete discontinuous zones of sand and gravel which are targeted by regional groundwater users. The sand and gravel zones are approximately an order of magnitude greater in hydraulic conductivity, than the upper alluvial aquifer zone (above 19 mBGS). The thickness of the alluvial aquifer increases in a downstream direction from Oakey, to as much as 40 mBGS. Based on observations of contaminants of concern, it is apparent that PFCs have migrated into the lower alluvial aquifer, and petroleum hydrocarbons have been greatly retarded in their movement from the upper alluvial aquifer to the lower alluvial aquifer.

Diagram 4.1 Conceptual hydrogeologic cross-section diagram



The regional groundwater flows westward towards the Condamine River and Oakey Creek. The vertical gradient is very small under natural conditions, but is expected to be highly negative (downward) between the upper and lower zones of the alluvial aquifer during periods of groundwater extraction (eg. during on-site irrigation well operation).

4.1.2 Groundwater extraction

There has been extensive development of water resources in the area since the 1950s to allow for agricultural irrigation and industrial and municipal water supplies. Industrial uses include on-site use of groundwater for landscape irrigation, fire protection, and previously, swimming pool filling. While aircraft cleaning was previously considered as a groundwater use, AACO representatives have indicated that this is unlikely to occur because of the salt content in the irrigation water. Upon provision of a reticulated water supply system at the site and in the surrounding area, many of the registered bores previously used for domestic water supply (c.1943-c.1960) have been abandoned, but not decommissioned. The volume of on-site irrigation water extracted from the two active irrigation bores is not known.

The extent of groundwater use in the surrounding agricultural fields has not been quantified. Two irrigation bores located west of the internal airfield security fence are utilised for crop irrigation. According to the well operator, the bores are utilised continuously for approximately one month per year (January to February period). The water is utilised for crop irrigation that was observed to include corn and cotton, but is likely to change periodically.

Between 1950 and 1971 the local council (now the Toowoomba Regional Council) installed municipal water supply bores on-site and within 1.5km of the site in the lower alluvial aquifer. The council bore (36603) located near the front gate house is known to be utilised during periods of drought to supplement the reticulated water supply system. The extracted water is pumped to the council’s reverse-osmosis treatment plant in Oakey, prior to public use.

4.1.3 Streams

Oakey Creek is deeply incised and is generally considered to be a losing stream that contributes surface water flow to the regional groundwater. Baseflow within the town of Oakey is primarily attributed to discharge of treated municipal effluent. The interaction of groundwater and surface water between the mouth of Oakey Creek and the town of Oakey is likely to act as a groundwater source and a discharge feature during different times of the year. It is unlikely that site contaminants will impact Oakey Creek in measureable quantities due to natural attenuation with biodegradation over 7.2 km between the site and the nearest probable discharge area downstream from Oakey. While it is noted that the creek is located 1.2 km south of the site, groundwater has been observed flowing west along a much longer flow path.

Drainage channels on the north side of the airfield flow toward Doctors Creek. Doctors Creek is an intermittent stream that loses water to the alluvial aquifer when surface water is present. The creek is not incised and occasionally floods the surrounding fields and roads during wet periods. A large sump and stormwater detention pond is located to the north of the site to assist farmers in draining their fields after wet periods. It is likely that this detention pond may act as a seasonal source of groundwater recharge. However, the groundwater mound is unlikely to be noticed during water level monitoring at the site because of the substantial distance from site (over 1km north).



4.2 PSH Site Conceptual Model

Phase separated hydrocarbons, also known as light non-aqueous phase liquids (LNAPLs) are immiscible in water and have a lower density, so they essentially float on the water table. The tendency to float requires the development of a PSH-specific conceptual model to predict PSH behaviour in the environment.

The source area of PSH within Areas C1 and C2 is believed to be the dis-used interceptor trap (C53) and waste fuel underground storage tank (UST; C60) in Area C1 associated with building C2. The infrastructure assessment report by Intelara Engineering (2009) confirmed likely points of oil egress into surrounding soil. The failure points were cited as the UST pipe connection fittings where movement (subsidence or reactive clay) was likely to have occurred. Observations of PSH accumulation on groundwater beneath these infrastructure features indicate vertical migration of PSH to the water table at approximately 15mbgs (URS 2010, Coffey 2011, PB 2012a, PB 2013a).

Since the UST is no longer in-use, the leakage of waste fuel may have ceased. However, Parsons Brinckerhoff has not confirmed that the UST is entirely empty. Over a period of time, most of the PSH will drain from the soil into groundwater, leaving residual PSH in the unsaturated soil beneath the failed infrastructure. The residual unsaturated PSH will slowly dissolve into recharging rainwater (or other through-flow from potentially leaky underground infrastructure) as it flows down to the water table, thereby acting as a secondary source of groundwater contamination for dissolved fuel impacts. While most of Area C1 is covered by hardstand, an appreciable quantity of water may leak from cracks in pavement and recharge groundwater beneath Area C1. It is also recognised that pressurised piping systems and stormwater drains to recharge groundwater beneath the pavement. It was noted in 1991 that utilities at the site are susceptible to cracking from soil movements (Kinhill 1991).

The PSH that reaches the water table will essentially float on the water, given that the specific gravity is 0.80, as measured during 2012 (PB 2012a). It is important to recognise that the aquifer matrix porosity and capillary pressure of the aquifer matrix limit the degree of PSH saturation within the water saturated pores. In aquifers with small grain size matrix, such as that which occurs in the upper alluvial aquifer at the site, the porosity saturation by PSH is typically quite low. The principal descriptor of the relationship between PSH and water saturation is the van Genuchten parameter, which is utilised in later calculations of contaminant mass. In short, the presence of the fine grained aquifer matrix in the upper alluvial aquifer can be expected to have a small portion of measured PSH thickness as pure PSH

The measurement of PSH thickness in wells near the source area indicates as much as 3.1m of apparent PSH thickness. However, the apparent thickness in the well is a poor estimation of PSH mass in the aquifer due to the vertical PSH migration form the surface which leaves a path of residual PSH. Furthermore groundwater table fluctuations lead to residual PSH emplacement above the water table and entrapment below the water table (smear zone).



Groundwater has been observed to fluctuate by up to 0.6 m in Area C1 (as represent by monitoring well MWC1-G). Fluctuation in the primary PSH impacted wells (MWC1-B and MWC1-D) cannot be accurately calculated due to difficulties in obtaining reliable PSH measurements (PB 2013a). It has been noted that in fine-grain soils (clay) water table increases may lead to minor increases in apparent PSH thickness in monitoring wells, which is unrelated to the volume of contaminant mass or mobility within the aquifer (Parcher et al 1995).

PSH transmissivity (a measure of recoverability) was estimated to range between 2.0x10-4 m/day to 1.8x10-3 m2/day (PB 2012a). This value indicates poor recoverability of PSH using traditional extractive technologies (ITRC 2009). Coupled with an average hydraulic conductivity of 0.18 m/day in the upper alluvial aquifer, the low PSH transmissivity also suggests that the mobility of the PSH is low. Horizontal mobility of PSH indicates no

significant observable trend in down-hydraulic gradient movement of PSH (as observed in

monitoring well MWC1-G). Since the PSH is entrapped within the upper alluvial aquifer and

the on-site irrigation supply bores utilise the lower alluvial aquifer, PSH mobility has not been affected by the operation of these bores.



5. Remediation goals and strategy The strategy for remediating petroleum hydrocarbons in Areas C1 and C2 must meet or exceed the existing environmental regulatory framework at the site. The remediation objectives are defined within this Section as clean-up goals based on national guidance documents, where available.

5.1 Regulatory Framework

The Department of Defence operates the site that is located on land owned by the Commonwealth of Australia. Therefore, the management of environmental impacts to the site’s soil and groundwater are not under state or local jurisdiction. The primary regulatory requirements are related to the Environmental Protection and Biodiversity Conservation Act (1999, as amended).

Impacts to off-site properties, including off-site receptors, would be regulated under Queensland’s Environmental Protection Act (1994) that is administered by the Department of Environment and Heritage Protection.

Defence had engaged a Technical Advisor to review the work performed by Parsons Brinckerhoff and other consultants.

5.2 Remediation objectives

Based on the review of the current contamination status of soil and groundwater at the site and the outcome from the indicative HHRA (PB 2013b), phase separated and dissolved phase hydrocarbons identified in groundwater are unlikely to pose unacceptable health risk to the future commercial and industrial site users or to excavation workers via vapour intrusion pathway. Hence, the remediation objective is to ensure the site will continue to be suitable for future commercial and/or industrial use. The assessment of soil vapour risk (PB 2013b) indicated that further consideration of air-phase hydrocarbons was not required at the site.

5.2.1 Cleanup Goals

The general cleanup goals for hydrocarbons in groundwater are as follows:

Source area remediation of PSH in unsaturated soil beneath failed infrastructure in Area C1.

Mitigation of risk from PSH migration off-site.

Mitigation of risk from dissolve phase hydrocarbon impacts to water supply wells, offsite groundwater and surface water bodies.



The specific soil remediation goal is to achieve source area hydrocarbon concentrations below:

Friebel and Nadebaum 2011. CRC CARE Technical Report No. 10, HSL-F (industrial land use) in clay soil; Soil Health Screening Levels for Vapour Intrusion and Direct Contact.

NEPC 1999. HHIL-F, Commercial/Industrial Setting.

NEPC 2013. HSL-D, Commercial/Industrial Setting for soil in Areas C1 and C2.

Specific hydrocarbon groundwater remediation goals that manage potential risks to groundwater users have been nominated:

No lateral PSH or dissolved phase hydrocarbon migration beyond Areas C1 and C2 (a compliance boundary indicative of significant plume migration requiring further action).

No dissolved phase hydrocarbon impacts to water supply wells or off-site groundwater.

5.3 Remediation strategy

Parsons Brinckerhoff has undertaken research into potential remediation technologies using a variety of information sources. A wide variety of common and novel approaches to soil and groundwater remediation for PSH has been considered for the site, with separate technology assessment for each category.

Technical, financial and logistical considerations were considered and compiled for each technology within the Remedial Options Feasibility Study (ROFS, PB 2013c). The definitions and relevance of each consideration are provided below:

Technical considerations include the physical ability to remove contamination within a reasonable time frame. A reasonable time frame is considered to be 5 years, based on CRAT ranking preferences, and 30 years is considered allowable based on principles of intergenerational equity.

Logistical considerations include access, equipment availability, waste disposal and facility operations requirements.

Financial considerations include the capital costs of equipment, installation and commissioning, operations, maintenance and waste disposal.

A summary of the ROFS findings is provided in Section 5.3.1 and 5.3.2 for recommended soil and groundwater remediation strategies.

5.3.1 ROFS strategy summary – Petroleum Hydrocarbons in soil

The most cost effective means to remediate hydrocarbons in the source area (tank C60) was identified to be UST and interceptor trap removal, shallow soil excavation and natural source-zone depletion. This combination of activities represents clean-up to the extent practical, given the remediation goals. Since soil vapour and water supply well impacts by hydrocarbons are not considered to be significant risks, more aggressive remedial methods like in-situ soil heating are not necessary.



Consideration of vacuum enhanced recovery for residual PSH in the unsaturated zone is considered within Section 5.3.2 as a pilot trial.

5.3.2 ROFS strategy summary – Petroleum Hydrocarbons in groundwater

The most cost effective means to remediate hydrocarbons in the Area C1 groundwater was identified to be natural source zone depletion after source area remediation. Natural source zone depletion refers to the gradual reduction in secondary source contaminant mass (ie. PSH on groundwater) and is intrinsically linked to monitored natural attenuation.

Due to a data gap regarding the potential for multiphase extraction to be effective at the site, the RAP for hydrocarbons will include a pilot trial for mobile multiphase extraction (MPE). Based on PSH bail-down tests and observed soil characteristics and water table depth, pump and treat technology will be ineffective for PSH recovery. However, the viability of vacuum enhanced recovery is unknown.

If mobile MPE were trialled successfully, long-term (5-year) operation of a dedicated dual-phase product recovery system was determined to have substantial cost that would likely outweigh the limited benefits. Since there is a large volume of PSH considered to be residual mass within the plume, it is likely that there will be a measureable quantity of PSH thickness remaining at the end of the 5-year program. Reduction of PSH mass is beneficial to reducing the longevity of the hydrocarbon plume, but it does not eliminate the ongoing need for groundwater monitoring presented as part of the monitored natural attenuation program.

Alternatively, if the pilot trial is successful, mobile MPE could be utilised periodically within the former UST system area to attempt to reduce the contaminant mass of PSH on an infrequent basis. The periodic use of mobile MPE would be determined by previous PSH recovery and the rate of PSH thickness rebound. The phase-out of mobile or dedicated MPE should be determined through the use of bail-down test to calculate PSH transmissivity over time. When PSH transmissivity versus time indicates PSH transmissivity reducing at an exponentially decaying rate, further extraction of residual PSH mass is not feasible. It is noted that the existing PSH transmissivity rate was calculated to be less that the published values for successful extraction by pumping without vacuum extraction. No published values of PSH transmissivity for effective MPE remediation currently exist.



6. Remediation approach Based upon the findings of previous environmental site assessments, human health risk assessments and remedial options feasibility studies for the site, the recommended site remediation plans are detailed below.

6.1 Preliminaries

Prior to commencement of the remedial works at the site, all relevant regulatory, Defence and site approvals for the use of the chosen remediation technology need to be completed prior to commencement of the activity.

Defence Environmental Clearance Certificate (ECC).

Environmental Management Plan (EMP).

Site Safety Management Plan (SSMP).

Health, Environmental and Safety plan (HESP), outlined in Section 6.1.1.

All off-site remediation waste transport and disposal requirements, as indicated in Section 6.1.2.

6.1.1 Health, environment and safety plan

A HESP will be prepared prior to performing on-site works associated with this RAP. The HESP will also address the health and safety of site users in defined work areas when considering site security, excavation safety, vibration, noise, odour and dust levels.

Work associated with the remediation of the Site will conform at a minimum, to the requirements of the Commonwealth Work Health and Safety Act 2011 and associated Regulations.

Typically the health and safety plan will address the following issues:

Regulatory Requirements.

Responsibilities.

Hazard Identification and Control.

Chemical Hazard Control including handling, mixing and application of chemical oxidant and oxygen release compounds.

Sample and Chemical Handling Procedures.

Personal Protective Equipment.

Work Zones.

Decontamination Procedures.



Emergency Response Plans.

Contingency Plans.

Incident Reporting.

6.1.2 Notable waste disposal requirements

Off-site disposal of waste soil from remediation activities is regulated by the Queensland Department of Environment and Heritage Protection (DEHP) under the Queensland Environmental Protection Act 1994. Prior to removal of any contaminated soil for off-site disposal, a Contaminated Soil Disposal Permit must be granted by DEHP. As part of the permit application requirements, the site (Lot and Plan identification) of waste origination must be registered on the DEHP Contaminated Sites Register. The site must be identified by Lot and Plan numbers with a Certificate of Title (or allowed equivalent for Commonwealth Land). Sufficient time must be allocated for this process, including approval and assistance of site registration by Defence.

Other waste transport and disposal requirements may be required beyond those listed above.

6.2 PSH source area remediation

An essential element for site remediation is the decommissioning and removal of the UST C60 and associate interceptor trap and piping. Removal of the infrastructure will allow for excavation of secondary hydrocarbon impacts to the extent practical.

6.2.1 UST decommissioning and removal

The UST has been estimated as 1,000L with concrete construction. The system is situated south of Building C2 and next to the large AFFF UST. The initial site works should include the removal of any remaining tank liquids by a suitably licensed flammable liquids transport provider. All UST removal works should be conducted in accordance with the Australian Standard AS4976-2008 The Removal and Disposal of Underground Petroleum Storage Tanks. Further UST decommissioning requirements are outlined in Defence Contamination Directive Number 5, Fuel Farms, Underground Petroleum Storage Systems (UPSS) and Underground Storage Tank (UST) Environmental Management.

The UST and associated systems will be safely excavated for disposal at permitted off-site facilities. Any drain-lines connected to the decommissioned system will be sealed to prevent any accidental wastewater discharges. All soil that is removed from the excavation will be stockpiled on-site in a location pre-approved by Defence. The soil will be stockpiled in a temporary bund and covered by plastic top prevent run-off erosion and odour issues. The stockpiled soil will be sampled at a sufficient rate for classification purposes, and ultimately off-site disposal at a licensed facility. Due to the close proximity of the AFFF UST (C59), it is expected that perfluorocarbon impacted soil may be present in the waste oil UST excavation. The laboratory detection of perfluorcarbons should not preclude the off-site disposal of soil, provided that the receiving licensed waste facility is in agreement.



Clean fill material of a suitable nature for compaction will be utilised to fill the excavation upon completion. Installation of a replacement waste oil/fuel collection system has not been indicated by Defence. Should a new underground petroleum storage system (UPSS) be installed, engineering design considerations should include prevention of unwanted UPSS movement.

6.2.2 Excavation of secondary impacts to the extent practical

Petroleum hydrocarbon impacted soil is likely to exist beneath the UPSS, and is considered to be a secondary source of contamination. After the removal of the UPSS, hydrocarbon impacted soil should be excavated to the extent practical, as indicated in Figure 4, Appendix A. The estimated impacted area is approximately 7.5m by 15m. Detailed soil impact delineation has not been performed. Given that the water table is located at 15 mbgs, the practical limit of excavation depth is approximately 3.0m. Based on these estimations, approximately 250m3 of impacted soil may be recoverable. Consideration for adjacent buildings, waste AFFF UST and other underground infrastructure will limit the depth and lateral excavation distances.

Excavation validation samples will be collected from the horizontal and vertical limits. A single report will be utilised to transmit the assessment and decommissioning information to Defence. Soil contamination classification will be reported in a letter format suitable for distribution to Queensland DEHP and licensed waste facilities.

6.2.3 Natural source zone depletion after clean-up to the extent practical

Since hydrocarbon plume migration is a slow process which can be monitored, natural source zone depletion is considered to be appropriate for soil which cannot be feasibly excavated. However, it is typically not considered an appropriate method for low volatility fuels, as the removal of hydrocarbon mass through volatilisation to soil vapour is relatively low. Natural source zone depletion of jet fuel is dependent on dissolution to groundwater and biodegradation.

Given the absence of unacceptable risk to site workers in the recent health risk assessments (PB 2013b), the driving factor for mitigation of the soil is the potential for off-site hydrocarbon migration or migration to on-site irrigation wells. A groundwater monitoring plan is provided in Section 6.3.2 below. The groundwater monitoring plan provides triggers of contingency actions if contaminant migration or risks are unacceptable.



6.3 Petroleum Hydrocarbons in groundwater

The screening of selected remedial technologies for PSH removal in saturated soil (upper alluvial aquifer) beneath Area C1 identified three options that were suitable for the geology and PSH characteristics of jet fuel (refer to Table 2, Appendix B). These three technologies include:

excavation to the extent practical (approximately 3.0 metres depth)

multi-phase extraction for PSH removal

monitored Natural Attenuation after clean-up to the extent practical.

As excavation to the extent practical was examined in Section 6.2.2, only multi-phase extraction and monitored natural attenuation are discussed below.

6.3.1 Multi-phase extraction (MPE)

Multi-phase extraction (soil vapour, PSH and groundwater through a high vacuum extraction drop-pipe) was considered to be impractical at the site due to the high clay content of the upper alluvial aquifer and depth to the water table. High clay content and low PSH transmissivity suggest that PSH will not readily flow to an extraction well under pumping conditions. Furthermore, vacuum extraction of liquids by itself is unlikely to succeed at water table depths below 10.3 mbgs.

It may be possible to use high vacuum extraction with a drop pipe placed just below the oil surface. It could also be utilised with a single pump to extract the liquids, while the vacuum is applied to remove vapours and increase volatilisation. The utilisation of high vacuum liquid ring pump should increase the radius of influence for PSH recovery in a single-pump with vacuum system. Since the radius of influence on the aquifer by a high vacuum is unknown, a short pilot-trial is proposed to be conducted.

The pilot test may be run over a period of 2 to 5 days depending on the volume of liquids recovered. The mobile MPE equipment can be readily hired and deployed with minimal operational disruption. The outcome of the test will indicate the hydraulic and vacuum radius of influence, as well as potential PSH recovery rates.

The outcome of the pilot test may lead to one of the following outcomes:

Design and implementation of a full-scale vacuum enhanced single-pump MPE system:

includes vapour treatment and wastewater treatment

likely to need a gravimetric means to separate emulsified oils to enable waste stream treatment and quantification of recovered oil; and

potential issues with perfluorcarbons in groundwater that may require additional treatment.

Periodic mobile MPE use at PSH hot-spots where measured thickness exceeds a nominated valued for PSH transmissivity or thickness.

Monitored Natural Attenuation with natural source zone depletion.



Based on the site characteristics, it is expected but unproven that MMPE will have a small radius of influence and recover small, uneconomic quantities of PSH. It is important that the pilot trial tries to incorporate a MMPE system that readily enables the measurement of total PSH collected.

It is recommended that the pilot test occur at one or two monitor wells with the greatest measurements of PSH thickness (monitor wells MWC1-E and MWC1-F). Measurements of vapour pressure and water table depths should be collected at all monitor wells in Areas C1 and C2.

6.3.2 Monitored Natural Attenuation after clean-up to the extent practical

Monitored natural attenuation (MNA) refers to the process of periodic groundwater monitoring necessary to quantify a reduction in quantity or concentration over time. The reduction of contaminants is a result of naturally occurring physical, chemical and biological processes.

The preliminary assessment of MNA was completed within the Remedial Options Feasibility Study (ROFS, 2013c) which considered relevant technical, regulatory, financial and risk issues. The key technical considerations for preliminary approval were focused on remnant PSH in soil and groundwater. At many sites, the presence of significant PSH would preclude the consideration of MNA. Given this site’s unique characteristics, it was determined that MNA after primary source area removal was the most cost-effective long-term solution. Key factors in the MNA decision include:

low apparent PSH mobility

low calculated PSH mobility

lack of a significant dissolved phase hydrocarbon plume

no impacts to on-site irrigation wells

no PSH or dissolved phase impacts outside Areas C1 and C2

no unacceptable risks to site users observed.

The acceptance of MNA as a long-term solution is dependent on further characterisation and demonstration. The characterisation and demonstration will occur as part of the RAP, where primary, secondary and tertiary lines of evidence will be collected to confirm that jet fuel impacts are being attenuated by biodegradation, or other processes.

Primary lines of evidence include continued monitoring for the contaminants of concern to demonstrate plume stability and reduction in concentration over time. Plume stability for petroleum hydrocarbons in groundwater has been observed in previous groundwater monitoring events (PB 2013a, Coffey 2011, URS 2010). Secondary lines of evidence consider changes in geochemistry as a result of biodegradation, as well as the production of any degradation compounds. These parameters are generally considered to be ‘natural attenuation parameters’, which consist of dissolved oxygen, oxidation-reduction potential, sulfate, nitrate, ferrous iron and methane. Tertiary lines of evidence consist of identification of specific beneficial microbes or quantification of microbial processes.



6.3.2.1 Proposed monitoring well network

The existing monitoring wells (Figure 3, Appendix A) located at the site are partly adequate for monitoring the progress of natural attenuation. If any monitoring wells are destroyed during UPSS removal in Area C1, then they will need to be replaced. Likewise, any damage or destruction of monitoring wells in Areas C and C2 from site maintenance or construction will require repair or replacement of equivalent monitoring wells.

In order to build a fully adequate monitoring well network, it is necessary to have monitoring wells situated downgradient along the plume centre-line, source area and one un-impacted upgradient location (Beck and Mann 2010). A list of existing and proposed monitoring well network components is provided below:

Hydraulically Upgradient Monitoring Wells:

MWC1-C (dissolved phase hydrocarbon impacted)

One new hydraulically upgradient well in Area D2.

Source Area Monitoring Wells:

MWC1-B

MWC1-D

MWC1-E

MWC1-F

MWC1-G.

Hydraulically Downgradient Monitoring Wells:

MWC1-A (lower alluvial aquifer)

MWC2-O

MWC2-B

Two new wells in Area C1, located between MWC1-G and MWC1-I.

Sentry Wells:

MWC1-I

MWC2-N

Irrigation well 35453 (Area B3)

Irrigation well 35454 (Area C3).



Monitoring well MWC1-H was excluded from the monitoring plan based on well construction details and water level data which is indicative of a perched groundwater zone. Three new wells are required for installation in the upper alluvial aquifer with well screens from approximately 14m to 18m bgs. New monitoring wells should be installed in accordance with the Minimum Construction Requirements for Water Bores in Australia (NUDLC 2011).

6.3.2.2 MNA groundwater monitoring plan for hydrocarbon impacts in Areas C1 and C2

A proposed MNA plan has been developed to observe seasonal variations and ensure long term monitoring until the remediation goals are met and there is no longer risk to any potential receptors. The plan takes into account principals published by CRC Care (Beck and Mann 2010) as well as Defence Contamination Directive (DCD) 5. As DCD 5 requires more frequent sampling for the first three years after a well has been installed, quarterly sampling rates have been adopted for the first three years of MNA. It is noted that quarterly groundwater monitoring was not previously conducted at any of the site’s monitoring wells.

As indicated in DCD 5, all laboratory analysis must be conducted in accordance with Australian Standard AS 5667.11 Water quality-Sampling, Part 11: Guidance on sampling of groundwaters. All laboratory analysis for primary and secondary lines of evidence must be conducted in accordance with the National Environmental Protection Measures and National Association of Testing Authorities (NATA).

A proposed groundwater sampling plan is provided below:

MNA Year 1 to 3:

Groundwater and PSH gauging: Quarterly, all wells in Areas C1, C2 and accessible bores listed in Section 6.3.2.1. Water supply bores are not accessible for gauging.

Sampling frequency: Quarterly, all bores listed in Section 6.3.2.1.

Quarterly analytes: constituents of concern and natural attenuation parameters.

Annual analytes: tertiary lines of evidence.

MNA Year 4 onwards:

Groundwater and PSH gauging: Annual, all wells in Areas C1, C2 and accessible bores listed in Section 6.3.2.1. Water supply bores are not accessible for gauging.

Sampling frequency: Annual, all bores listed in Section 6.3.2.1.

Analytes: constituents of concern and natural attenuation parameters

The proposed list of analytes for the MNA program is provided below:

Constituents of concern:

TPH C6-C40

Benzene



Toluene

Ethylbenzene

Total xylenes

Naphthalene

Perfluorooctanesulfonic acid (PFOS)

Perfluorooctanoic acid (PFOA).

Natural attenuation parameters (secondary lines of evidence):

pH (field parameter)

Oxidation-reduction potential (field parameter)

Electrical conductivity (field parameter)

Dissolved oxygen (field parameter)

Sulfate

Nitrate

Ferrous iron

Methane.

Tertiary lines of evidence:

Various molecular biological tools, based on availability and not NATA accredited (eg. stable isotope probing and quantitative polymerase chain reaction).

A sufficient number of quality control samples must be collected during each sampling event to meet the data quality objectives of the MNA program. A summary of proposed data quality indicators are provided in Table 6.1.

Table 6.1 Data quality indicators

Item Description

Laboratory accreditation

All the laboratories engaged are accredited by NATA for the analyses to be undertaken, excepting tertiary lines of evidence. All laboratories are to perform their own internal QA/QC programs and will use appropriate detection limits for the analyses to be undertaken.

Field duplicates

Blind and spilt duplicates will be sampled at the rate of

1 in 10 primary samples for intra-laboratory

1 in 20 primary samples for inter-laboratory

Relative percentage difference (RPD) will be calculated for the duplicate samples and compared to likely values (30 -50%) (AS 4482.1-2005).

Rinsate One equipment rinsate will be collected per day of sampling and analysed for contaminants of concern. The rinsate results should have no detections of contaminants of concern.



Item Description

Trip blanks One trip blank (prepared by the laboratory) will be analysed per batch of soil and groundwater samples and analysed for volatile compounds.

The trip blank results should have no detections of volatile hydrocarbons.

Laboratory quality control procedures

The laboratory QA/QC programs will be reviewed upon receiving the analytical results. The following items will be verified:

Surrogates: 70 – 130% recovery

Matrix spikes: 70 – 130% recovery for organics or 80 – 120% for recovery of inorganics Control samples: 70 – 130% recovery for soil; 80 – 120% recovery for waters

Duplicate samples: <4 practical quantitation limit (PQL), +/- 2 PQL, 4-10 PQL, 0 – 25 or 50% RPD; >10 PQL – 0 10 or 30% RPD. Method blanks: 0 to <PQL



7. Contingency management In the event that proposed remediation measures indicate that the site remediation objectives or data quality objectives have not been achieved, contingency measures are to be reviewed and enacted when appropriate. Contingency measures for each remedial activity are provided within this section.

7.1 PSH Source Area Remediation

Contingency plans for anticipated problems that may arise from the PSH Source Area Remediation during the course of the remediation works are presented in Table 7.1 below.

Table 7.1 Contingencies for PSH source area remediation options

Remediation Scenario Remedial Contingencies/Actions Required

UST decommissioning and removal

Additional USTs identified during decommissioning of UST C60.

Unlikely: variation to be sought for additional UST removal.

No significant soil impacts identified during UST removal

Unlikely: variation to conduct detailed soil assessment to identify alternative source area.

Excavation to the extent practical

Hydrocarbon impacted soil above water table, but too deep to excavate

Likely: proceed with natural source zone depletion and MNA to confirm plume stability.

Unable to dispose of soil off-site due to exceedence of criteria for hydrocarbons and/or PFCs.

Unlikely: on-site remediation or on-site reuse if soil lab results do not exceed the adopted industrial soil criteria (eg. NEPC 2013).

Natural source zone depletion (Residual PSH in soil)

PSH plume has indications of unacceptable migration

Unlikely: extend monitoring to include wells outside of Area C1 and C2 and/or off-site wells. Consider implementation of MPE to stop PSH migration and increase plume stability.

Dissolved phase plume has indications of unacceptable migration

Possible: continue and adjust groundwater monitoring. Rex-examine remedial options to mitigate groundwater migration or receptor exposure.

It is considered to be a likely scenario that excavation to the extent practical will be limited by depth due to equipment and site infrastructure. The planned response to the likely scenario is to proceed with MNA to monitor hydrocarbons in groundwater on a quarterly basis. Preliminary indications suggest that PSH plume mobility is low and that dissolved phase groundwater impacts do not present an unacceptable risk. Further discussion of MNA risks is provided in Section 7.2.



7.2 Petroleum Hydrocarbons in groundwater

A key component of the monitoring well network is gauging and sampling of sentry wells along the downgradient boundary of Areas C1 and C2, as well as the operating irrigation wells 35453 and 35454. Should increasing dissolved phase hydrocarbon concentrations or measurable PSH migrate to the sentry wells, then contingency plans must be immediately examined.

Contingency plans for anticipated problems that may arise from the Petroleum Hydrocarbons in Groundwater Remediation during the course of the remediation works are presented in Table 7.2 below.

Table 7.2 Contingencies for petroleum hydrocarbon remediation options


Multi-phase extraction

Unable to effectively extract from the groundwater due to soil type

Likely: utilise natural source zone depletion with MNA

Unable to effectively extract from the groundwater due to depth

Possible: consider use of a groundwater extraction pump with vacuum enhanced extraction.

Extracted PSH is emulsified during extraction. Not possible to measure PSH recovered.

Possible: Separate oil and water with appropriate technology (eg. gravimetric or centrifugal separators)

Unable to effectively extract a sufficient volume of PSH using vacuum extraction and a single groundwater pump during the pilot trial

Possible: utilise natural source zone depletion with MNA

An economical feasible quantity of PSH is extracted in the source area.

Unlikely: Develop remedial design for a full-scale long-term implementation of MPE

Natural source zone depletion (PSH on groundwater)

PSH plume has indications of unacceptable migration




MNA PSH plume has indications of unacceptable migration







In the unlikely event that PSH plume migration is greater than expected (0.5 m/year) and a measureable quantity is detected at a sentry well, then a contingency plan for improving PSH plume stability will be implemented. The PSH migration contingency plan consists of either:

hydraulic control through MPE with a single groundwater pump per extraction point; and/or

decommissioning of an impacted or immanently affected irrigation bore.

In the unlikely event that monitored natural attenuation does not indicate sufficient dissolved plume stability, then remedial options for dissolved plume control should be revisited. Trigger levels for sentry bores include exceedence of the adopted groundwater criteria. The trigger levels for hydrocarbon concentrations from operating irrigation bores is considered to be Australian Drinking Water Guidelines (2011). In the event that a trigger level is exceeded, the sentry bores and any other useful delineation wells should be resampled to confirm the analyte concentration and complete migration pathway. It is important that the migration pathway is understood as there are many other potential sources of hydrocarbon impacts to groundwater exist at the site.

The dissolved phase migration contingency plan consists of either:

hydraulic control through MPE with a single groundwater pump per extraction point; and/or

remedial Option Feasibility Study revision; and/or:

PSH (secondary source) recovery through MPE with a single groundwater pump per extraction point

PSH (secondary source) recovery through in-situ soil heating if risk warrants cost

other unreviewed technologies (e.g. permeable reactive barrier, air sparge with vacuum extraction, enhanced in-situ bioremediation).

decommissioning of an impacted or immanently affected irrigation bore; and/or

review of adopted criteria for irrigation bores based on confirmation of water use, or potential restriction of irrigation water uses (eg. fire emergencies only).



The selection of the Australian Drinking Water Guidelines (2011) as the adopted criteria for irrigation bores is based on the unlikely potential for human consumption of irrigation water on-site. Numerous landscape irrigation taps are located throughout the site and the taps are unlabelled and unsecured. Due to the brackish water quality, it is unlikely that anyone would regularly consume the groundwater at the site. As such, exceedence of the ADWG 2011 trigger levels in sentry wells should be considered as a warning to undertake further assessment.



8. References Adamski, Mark, Cho, Paul, and Kirkman, Andrew 2010. LNAPL Transmissivity as a

Metric.

Midwest Geosciences Group (www.midwestgeo.com), webinar held on 14 April 2010.

ADWG 2011. National Health and Medical Research Council 2011. National Water Quality Management Strategy, Australian Drinking Water Guidelines, Publication 6, 2011.

API (American Petroleum Institute) 2001. Methods for Determining Inputs to Environmental Petroleum Hydrocarbon Mobility and Recovery Models. API Publication Number 471, July 2001.

Australian Government 1999. Environmental Protection and Biodiversity Conservation Act. Act No. 91 or 1999 as amended, 9 November 2012.

Beck and Mann 2010. Technical Report No 15: A technical guide for demonstrating monitored natural attenuation of petroleum hydrocarbons in groundwater, CRC for Contamination Assessment and Remediation of the Environment, September 2010.

Coffey 2011. Stage 2 (Part 2) Environmental Investigation, Army Aviation Centre, Oakey, 9 September 2011.

Friebel, E and Nadebaum, P 2011. Health screening levels for petroleum hydrocarbons in soil and groundwater. Summary, CRC CARE Technical Report no. 10, CRC for Contamination Assessment and Remediation of the Environment, 2011.

ITRC (Interstate Technology and Regulatory Council) 2009. Evaluating LNAPL Remedial Technologies for Achieving Project Goals. LNAPL-2. Washington, D.C.: Interstate Technology and Regulatory Council, LNAPLs Team. www.itrcweb.org.

Intelara 2009. Oakey Base – Buildings C2 oil separator and storage – Report on probable leak and ground contamination. Project Number: 7400.004. March 2009.

Kinhill Engineers Pty Ltd 1991. Army Pollution Audits – Queensland, Volume 2, Detailed Report.

NEPC 1999. National Environment Protection (Assessment of Site Contamination) Measure 1999, National Environmental Protection Council Service Corporation.

NEPC 2013. National Environment Protection (Assessment of Site Contamination) Measure 1999, as amended during 2013, National Environmental Protection Council Service Corporation.

NUDLC 2011. Minimum Construction Requirements for Water Bores in Australia, Australian Government: National Water Commission, February 2012.



Parcher, M.A., J.A. Johnson, and J.C. Parker. 1995. Effects of soil type on separate phase hydrocarbon recovery under fluctuating water conditions. In: Proceedings of the 1995 Petroleum Hydrocarbons and OrganicChemicals in Ground Water: Prevention, Detection, and Remediation Conference and Exhibition, pp. 439-451.

Parsons Brinckerhoff 2012a. Environmental Investigation - Stage 3 Risk Assessment and Remediation Design, Army Aviation Centre Oakey (AACO), August 2012.

Parsons Brinckerhoff 2013a. Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey, Groundwater Monitoring Event, December 2012. 22 February 2013.

Parsons Brinckerhoff 2013b, Human Health Risk Assessment, Petroleum Hydrocarbons in Areas C1 and C2 – Stage 3 Risk Assessment and Remediation Design, Army Aviation Centre Oakey, March 2013, draft.

Parsons Brinckerhoff 2013c, Stage 3 Risk Assessment and Remediation Design at Army Aviation Centre Oakey Remediation Options Feasibility Study, May 2013.

QED 2013. 2” Alpha Ferret In Well Separator Installation and Operation Manual, QED Environmental Systems, 13 March 2008.

URS 2010. Stage 1 and Stage 2 Environmental Investigation at Army Aviation Centre, Oakey, Queensland, 14 October 2010.



9. Limitations This assessment was restricted to the agreed-upon Scope of Services. No representations or warranties are made concerning the nature or quality of the soil and water, or any other substance on the Property, other than the visual observations and analytical data as stated in this report.

On all sites varying degrees of non-uniformity of the vertical and horizontal soil or groundwater conditions are encountered. Hence no sampling technique can completely eliminate the possibility that samples are not totally representative of soil and/or groundwater conditions encountered. The sampling can only reduce this possibility to an acceptable level.

It should also be recognised that site conditions, including contaminant extent and concentrations can change with time. This is particularly relevant if this report is used after a protracted delay, such that further investigation of the site may be necessary.

In preparing this report, Parsons Brinckerhoff has relied upon certain verbal information and documentation provided by the client and/or third parties. Except as discussed, Parsons Brinckerhoff did not attempt to independently verify the accuracy or completeness of that information, but did not detect any inconsistency or omission of a nature that might call into question the validity of any of it. To the extent that the conclusions in this report are based in whole or in part on such information, they are contingent on its validity. Parsons Brinckerhoff assume no responsibility for any consequences arising from any information or condition that was concealed, withheld, misrepresented, or otherwise not fully disclosed or available to Parsons Brinckerhoff.

Within the limitations of the agreed-upon Scope of Services, this assessment has been undertaken and performed in a professional manner, in accordance with generally accepted practices, using a degree of skill and care ordinarily exercised by reputable environmental consultants under similar circumstances. No other warranty, expressed or implied, is made.

This report is based upon the Scope of Services, and is subject to the Limitations defined herein. It has been prepared on behalf of Department of Defence for the benefit of Defence and subsequent tenderers of remedial options described within this report from Defence (‘the Nominated Reliants’). No person or organisation other than the Nominated Reliants is entitled to rely upon any part of the report without the prior written consent of Parsons Brinckerhoff. Any person other than a Nominated Reliant using or relying on this report shall have no legal recourse against Parsons Brinckerhoff or its parent or subsidiaries, and shall indemnify and defend them from and against all claims arising out of, or in conjunction with, such use or reliance.

Appendix A

Figures

Remediation Action Plan

4

Remediation Action Plan

Appendix B

Relevant ROFS Tables (PB 2013c)

Table 1. Remedial Options Screening for Petroleum Hydrocarbons in SoilAACO Area C1 - March 2013

Remediation Technology Advantages Disadvantages

Applicable to fine grain matrix?

Applicable to jet fuel PSH?

Time frame for cleanup Technical Considerations Logistical Considerations Financial Considerations

Excavation 100% removal, time frame

Accessibility, depth, limitations, cost, waste, disposal

Yes Yes very short

Limitations on extent of excavation depth and width. Requires PFC testing because of potential leaks from AFFF tank.

Short term disruption of activities near Bldg C2.

Principal contractor work, estimated cost under $100,000, with an excavation volume up to 250m3.

Natural source zone depletionNo disruption, implementable, low carbon footprint

Time frame, containment Yes Possible very long

Relies upon volatilisation to soil vapour and dissolution to groundwater. Jet fuel has a relatively low volatility. Soil testing necessary after UST removal to confirm sol concentrations and constituents from 3 to 15mbgs.

No disruptions to site activities.

Ongoing monitoring, 4x per year in conjunction with other site environmental activities for groundwater impacts. No additional cost to groundwater program.

Air sparging, soil vapour extractionProven, implementable, vapour control

Does not treat heavy-end LNAPLs/low-permeability soils, off-gas vapour management

No No very long

Not likely to be practical if soil beneath UST contains no coarse grained soil. However, it could be attempted in conjunction with a complimentary groundwater remediation program.

Installation of additional bores for extraction of vapours, and installation of blowers and remediation equipment would require minor disruption to Area C1.

Installation of additional bores for air extraction. Waste gas treatment. Estimated cost in excess of $100,000

Multiphase extraction (one pump)Proven, implementable, hydraulic control

Generated fluids treatment No Yes medium Same considerations as soil vapour extraction.

Same considerations as soil vapour extraction.


Surfactants and cosolvent flushing Time frame, source removal

Hydraulic control required, by-products, cost, dissolved COCs treatment, required homogeneity, water treatment, access

No Yes shortInjection of liquids into the clayey soils would be very slow, with possible surface breaches.

Presence of Bldg C2 limits ability to easily gain hydraulic control. Drilling would be required inside building.

Installation of additional bores for hydraulic control. Specialised surfactant and wastewater treatment. Estimated cost in excess of $150,000

In-situ soil heating

Time frame, source removal, proven, implementable

Hydraulic control required, by-products, cost, vapour generation, access

Yes Yes shortGood potential for success, but implementation may be limited by other underground infrastructure.

Three-phase power or natural gas may not be readily available in Area C1. Equipment limitations in Australia.

Limited equipment availability, high cost for setup and fuel. Estimated cost in excess of $100,000

Table 2. Remedial Options Screening for Petroleum Hydrocarbons in GroundwaterAACO Area C1 - May 2013

Remediation Technology Advantages Disadvantages

Applicable to fine grain matrix?

Applicable to jet fuel PSH?

Time frame for cleanup# Technical Considerations Logistical Considerations Financial Considerations

Excavation 100% removal, time frame

Accessibility, depth, limitations, cost, waste, disposal

Yes Yes very short High technical complexity due to depth.

Significant disruption to Area C1 for a few weeks. Cost prohibitive.

Natural source zone depletion

No disruption, implementable, low carbon footprint

Time frame, containment Yes Possible very long

Relies upon volatilisation to soil vapour and dissolution to groundwater. Jet fuel has a relatively low volatility. Soil testing necessary after UST removal to confirm sol concentrations and constituents from 3 to 15mbgs.

No disruptions to site activities.

Ongoing monitoring, 4x per year in conjunction with other site environmental activates for groundwater impacts. Estimated cost of routine monitoring of a limited number of wells is under $50,000 per year.

In situ chemical oxidation Time frame, source removal

Rate-limited hydraulic control required, by-products, cost, vapour generation, rebound, accessibility/spacing homogeneity

No No very short to short

Presence of significant PSH requires too much oxidant to be injected.

Additional monitoring wells and injection wells required. A disruption to Area C1 activities would be brief, on the order of a few weeks.

Cost prohibitive due to volume of oxidisers required.

Product skimming Proven, implementable

Time frame, limited to mobile LNAPL, ROI No Yes long to

very long

In-well skimming would have an insufficient ROI. Trenching would be impractical due to water table depth. Considered to be technically prohibitive.

Minor routine disruptions to site activities during skimmer inspections.

Cost of skimmers and additional bores, accompanied by monthly site inspections, would be under $75,000 per year.

Air sparging, soil vapour extractionProven, implementable, vapour control

Does not treat heavy-end LNAPLs/low-permeability soils, off-gas vapour management

No No very long

Not likely to be practical if soil beneath UST contains no coarse grained soil. However, it could be attempted in conjunction with a complimentary groundwater remediation program.

Installation of additional bores for extraction of vapours, and installation of blowers and remediation equipment would require minor disruption to Area C1.

Installation of additional bores for air extraction. Waste gas treatment. Estimated cost in excess of $100,000

Multiphase extraction (one pump)Proven, implementable, hydraulic control

Generated fluids treatmentPossible, but uncertain

Yes medium Same considerations as soil vapour extraction.



Surfactants and cosolvent flushing Time frame, source removal

Hydraulic control required, by-products, cost, dissolved COCs treatment, required homogeneity, water treatment, access

No Yes shortInjection of liquids into the clayey soils would be very slow, with possible surface breaches.

Presence of Bldg C2 limits ability to easily gain hydraulic control. Drilling would be required inside building.

Installation of additional bores for hydraulic control. Specialised surfactant and wastewater treatment. Estimated cost in excess of $150,000

In-situ soil heating

Time frame, source removal, proven, implementable

Hydraulic control required, by-products, cost, vapour generation, access

Yes Yes short

Good potential for success, but implementation may be limited by other underground infrastructure.

Three-phase power or natural gas may not be readily available in Area C1. Equipment limitations in Australia.

Limited equipment availability, high cost for setup and fuel. Estimated cost in excess of $100,000

Notes: # indicates approximate gross time for clean-up. The value is not based on site specific calculations, and is provided for high level comparison only.

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