2015 Clean up Project Excellence Award - Enviropacific for "FTA Remediation, Point Cook"
by Damien McKay, Enviropacific Services
Client: Defence Environmental Remediation Programs, Department of Defence
Contractor: Enviropacific Services
Project Value: $32 Million
Senior Project Manager: Damien McKay
Project Manager: Joseph Denham
1. Project background, aims and objectives
1.1 Project background and setting
The remediation of the former Fire Training Area (FTA), RAAF Base Williams, Point Cook was a significant project from both a historical and environmental perspective. Located at the longest continuously operating military aerodrome in the world, the base is included on the Commonwealth Heritage List (CHL), recognising its heritage value and the central role it played in the development of the RAAF. This fact combined with its location in a harsh and environmentally sensitive natural environment made this one of the most complex remediation projects undertaken in Victoria.
The FTA comprised of an area of approximately 27 hectares located south of RAAF Lake, within the Point Cook Coastal Park, south-east of the Williams RAAF base. The base is immediately adjacent to Port Phillip Bay, highlighting the sensitivity of the site to environmental receptors.
Image 1. FTA location relative to Port Philip Bay and RAAF base.
Three decades of firefighting training activities undertaken at the base from the mid-1950s had significantly impacted the underlying soil and groundwater. During that time, firefighting training was undertaken in several ‘burn pits’, where flammable liquids such as aviation fuel and organic solvents from local industry were utilised to create scenarios for firefighting training. Old airframes and drums were ignited, and then doused with extinguishing agents to simulate real events.
While these burn pits were subsequently closed over and backfilled with additional solid and liquid wastes, and the firefighting training at the site was discontinued, the residual contamination remained. The contamination on site comprised of several plumes of approximately 950,000 L of dense non-aqueous phase liquid (DNAPL) as well as light non-aqueous phase liquids (LNAPL) and related dissolved phase contamination. These plumes consisted of over 120 contaminant compounds including chlorinated hydrocarbons. Twelve Primary Contaminants of Interest (PCI’s) were selected as the basis for the remediation works.
Most of the soil between the burn pits and the layer of marine clay at the base of the shallow aquifer contained significant adsorbed contamination, which was similarly transferred to groundwater flowing through this area. Over time, the two factors of erosion along the coastline and movement in natural groundwater flow caused the DNAPL plumes from the former burn pits to migrate towards the bay, as shown in Figure 1. A coastal erosion study conducted in 2009 identified that a single severe southerly meteorological event could result in storm erosion and shoreline recession of several metres, exposing the DNAPL plume. This risk was one of the key drivers for the project.
Figure 1. The site plan shows the position of the original fire training pits (yellow outline) as they were constructed when the site was in use. The red and purple areas show the extent of the NAPL plumes immediately prior to commencement of remediation works. Source: AECOM.
The site brought with it a myriad of challenges, due to its geographical location, position on an active airfield, the contaminant load and the environmental sensitivity of surrounding areas, that all had to be overcome to allow timely completion of the project. Due to the site’s exposed coastal location, gale force winds were regularly experienced, which on several occasions significantly damaged the environmental enclosures, requiring additional air monitoring to be undertaken until they were repaired.
Image 2. Soil properties across the FTA were impacted by a range of contaminants. Source: Department of Defence.
Image 3. RAAF firefighter extinguishes a blaze at a base. Source: ABC
An unknown depth and extent of contamination was another challenge, with surveyed and contractual
source zone extents regularly extended, adding to difficulties with project planning. The unknown volume of groundwater requiring treatment was another challenge, as upwelling and ingress to the excavations far exceeded expectations and initial estimates, putting additional strain on the Water Treatment Plant (WTP).
Additionally, the highly corrosive contaminant load within the gas stream affected almost every internal surface of the Direct-Fired Thermal Desorption (DTD) plant, in many cases eroding 316 stainless steel. Once this was identified, the project team implemented additional control measures and preventative maintenance procedures, such as additional weekly cleaning events, and operational changes to limit the moisture content within some specific DTD components.
The FTA’s location on an active airfield and occupied air base meant that systems to manage unexploded ordinance (UXO) were required and all work needed to be carried out around aircraft and other defence force activities. The highly sensitive surrounding environment required extensive environmental diligence.
1.2 Aims and objectives
Enviropacific was engaged by the Commonwealth of Australia (Department of Defence) in 2013 to undertake the source removal remediation of the FTA. The objectives of the remediation project were clearly defined:
• Prevent the further migration of contamination offsite at concentrations that could adversely impact upon human health or the environment.
• Enable Defence to use the FTA Site for dry surface training with overnight camping.
• Mitigate Defence’s risk and long term liabilities associated with contamination of soil and groundwater at the FTA Site.
To achieve these objectives, the core project scope included:
• Site setup, including establishment of all services, roads and infrastructure on site: 2km high voltage underground cable for electrical power, water supply, site levelling, 3km gravel haul road, site amenities and accommodations.
• Excavation of more than 70,000 tonnes of chlorinated hydrocarbon contaminated soil, including raw DNAPL contamination.
• Construction and commissioning of a 30 tonnes per hour DTD Plant.
• Thermal treatment of soil for 12 Primary Contaminants of Interest to below USEPA Regional Screening Levels.
• Construction and commissioning of a WTP to treat more than 15 million litres of DNAPL, LNAPL and dissolved phase contaminated groundwater.
• Backfill and compaction of treated soil into validated excavations.
• Decommissioning and demobilisation from site.
• Revegetation of the site.
2. Remediation methods
Remediation of the former FTA site involved a complex amalgamation of the three matrices: soil, water and air, with separate and unique treatment systems and remediation
methods to deal with each matrix.
Contaminated soil was excavated within environmental enclosures to manage the contaminated atmosphere created upon commencement of excavation works. This atmosphere
was extracted via large fans, with the subsequent off-gas treated for particulates and organic contaminants before being discharged.
Excavation of the contaminated soil to a depth below the water table and below the level of Port Phillip Bay required the continual removal of contaminated groundwater. More than one kilometer of sheet piles were installed to manage the water ingress and a WTP was constructed to treat the contaminated water.
The close linking of the three matrices ensured all receptors were suitably managed and protected.
• Complex remediation involving three matrices: soil, water and air.
• Unique treatment systems for each matrix.
• Direct-fired thermal desorption (DTD) used to treat 70,000 tonnes of contaminated soil onsite.
• Purpose-built WTP treated more than 15 million litres of contaminated water.
Figure 2. The site, showing location of the DTD plant (soil remediation plant), pre-treatment enclosure, and two contaminated source zones (excavation area), August 2013. Source: Department of Defence.
Direct-fired thermal desorption (DTD) was the remediation method employed to treat the contaminated soil onsite. A counter-current DTD plant (Photo 3) was purpose built for the FTA remediation, allowing the
rapid treatment of the organic hydrocarbon contaminated soil at rates of up to 30 tonnes per hour.
Following excavation, the contaminated soil was transported in articulated dump trucks to the pretreatment enclosure for the purpose of blending, screening and drying. The objective of the pre-treatment works was to remove oversized materials and other waste, provide a consistent feed-stock for the DTD plant, and reduce the moisture content of the soils.
Contaminated soil was then fed into the DTD plant where the recalcitrant compounds were heated in a rotary kiln, to temperatures upwards of 400˚C, to desorb the contaminants from the soil matrix and into a vapour stream, which was then thermally oxidised to destroy the contaminants. Treated soil was discharged from the DTD plant, stockpiled, sampled and validated every 100 m³ to confirm it had been remediated to below adopted site criteria, and then backfilled into the validated excavation cells.
Contaminant levels were removed from levels upwards of 100 ppm to below laboratory detection limits (generally <0.5 ppm), including Vinyl Chloride, Benzene, Chloroform, 1,2-dichloroethane, and trichloroethene.
The DTD plant successfully treated more than 70,000 tonnes of material which was reinstated on site, resulting in zero soil diversion to landfill – a major achievement for a site remediation project of this scope and size.
Image 4. The counter-current DTD plant purpose built for the FTA remediation.
Three separate Emissions Control Systems (ECS) were developed and built for removal and treatment of contaminated soil vapours generated during the excavation works. Soil was excavated inside large environmental enclosures (tents). These tents controlled odours and emissions related to disturbance of
the soil and each tent used a purpose-built ECS to assist with maintaining a safe atmosphere inside and outside the tents.
Following desorption of the contaminants and transfer from the soil matrix into a gas in the DTD plant, the off-gas was passed into a thermal oxidiser under negative pressure, where the gas was heated to temperatures of upwards of 950˚C, destroying the contaminants. This gas then had its temperature rapidly cooled to avoid dioxin formation from 950˚C to 200˚C, was passed through a baghouse to remove the dust and fine particulates, and then finally passed through an acid-gas scrubber. Prior to the scrubber, the gas would be quenched to further drop the temperature to below 100˚C for neutralisation by the addition of caustic soda, bringing the gas to a pH closer to 7 prior to discharge.
Image 5. Environmental enclosures set up to control odours and emissions during excavations
Due to the shallow water table and aquifer, and the requirement to excavate to approximately four metres
below ground level to reach the marine clay layer, water ingress into the excavations needed to be carefully managed. More than one kilometre of sheet piles were installed on site to manage this water ingress, as the risk of rupturing the marine clay and impacting the clean aquifer below were so significant
that an extensive study on the marine clay depth was undertaken to ensure the sheet piles would only key into the clay to a depth of no more than 300 mm.
The purpose-built WTP treated 15,947,348 litres of contaminated water through a complex system of LNAPL/DNAPL separation, silt removal, filtration, air stripping and media based adsorption filtration to allow for discharge on site. Treatment of a further 7,000 kL of DTD plant waste water occurred in parallel with the contaminated water, with treated water meeting regulatory criteria of ANZECC 2000, 95% species protection for a marine setting. Prior to the commencement of treatment and discharge a detailed groundwater model using MODFLOW was commissioned to ensure no adverse impact would occur as a result of the dewatering and discharge of treated water. Ongoing groundwater depth gauging and monitoring was undertaken throughout the project to monitor and confirm that groundwater levels and concentrations were consistent with the model predictions.
Image 6. The secondary water treatment plant (WTP) at the FTA.
3. Risk management
The key risks of the FTA remediation can be considered in terms of risks to on site personnel, the base and the surrounding area, and to the highly sensitive surrounding environment.
3.1 Site personnel
There were a number of major hazards and risks on site that required expert management and controls put in place. Throughout the length of the project there were no lost time injuries (LTI). The project manager and engineer also implemented an inclusive consultation and incident prevention/review process, where near misses or minor incidents as well as general Enviropacific and external safety alerts were discussed.
3.2 Base and surrounding area
The Point Cook base is included on the Commonwealth Heritage List (CHL), recognising its heritage value as the oldest continually operating military airfield in the world and the central role it played in the development of the RAAF. Three of the nine heritage precincts on the base were identified as potentially being affected by the remediation works and access and work around the site had to be managed to prevent disturbance or damage.
Personnel working at the site were required to attend an Enviropacific site Induction that included identification of heritage issues and requirements prior to the commencement of works, visitors and delivery drivers were escorted through a specific gate to the Enviropacific site and only rubber tyred vehicles were permitted to pass through the three heritage precincts.
The closest residential zone areas were more than two kilometres from the former FTA, however risks of noise and dust to the surrounding community needed to be closely managed. These are discussed further in Sections 3.2.1 and 3.2.2.
3.2.1 Noise management
To meet the Noise Management requirements, Enviropacific engaged consultants Marshall Day Acoustics to produce a Noise Management Plan (NMP). The NMP considered the noise impact of operational and construction activities during remediation works. Baseline ambient noise monitoring was undertaken at agreed measurement locations prior to the commencement of any works, in order to provide feedback on any potential noise exceedances and to enable corrective actions to be implemented if required. Noise from remediation activities at the site was governed by State Environmental Protection Policy (Control of Noise from Commerce, Industry and Trade) No. N-1 (SEPP N-1). Noise monitoring was implemented in accordance with the NMP until all soil treatment was complete, with Noise Monitoring Reports being issued monthly to demonstrate compliance. No non-conformances were recorded regarding noise monitoring, confirming Enviropacific complied with its requirements relating to noise management.
3.2.2 Air quality
To meet the Air Quality Management requirements, Enviropacific engaged consultants EML Air (Ektimo) to produce an Air Quality Management Plan (AQMP). The AQMP detailed a monitoring and management process which included the type and frequency of monitoring to be implemented, together with action levels and responses. The monitoring was required to allow a reactive management plan for the control and abatement, and an audit of the effectiveness of the management and control of the various point source and diffuse emissions to air associated with the remediation works.
Baseline monitoring for ambient air was conducted 24 hours a day for a six day period. Baseline monitoring for deposition dust involved 5 samples being collected over a
month long period. All baseline monitoring was carried out prior to any remediation works commencing. Air quality monitoring was implemented until all works at the site had been completed. No non-conformances were recorded regarding ambient and deposition dust monitoring, confirming Enviropacific complied with its requirements relating to air quality monitoring.
The highly sensitive surrounding environment required extensive environmental diligence. The Environmental and Heritage Management Plan outlined the key environmental hazards that required management, including water, air discharge and waste. The proximity of the works to sensitive receptors such as Port Phillip Bay and the RAAF Lake, combined with the large quantity of impacted groundwater encountered during the excavation, made water management one of the most critical aspects of the project. Erosion and siltation controls were developed and modified as the project progressed. The WTP was designed and constructed to manage the impacted groundwater and other waste waters generated
during the works.
Image 7. Contaminated soil was excavated within environmental enclosures to manage the atmosphere.
Key risks of adverse water impacts included:
- Contaminated groundwater from dewatering excavations.
- Contaminated water runoff from wash down areas and wheel wash.
- Contaminated water runoff from DTD concrete slab.
- Water generated from DTD Scrubber.
- General erosion and sedimentation caused by runoff of uncontaminated areas of the site.
- Potentially incomplete treatment of contaminated water prior to discharge or reuse onsite.
- General site wastewater.
- A silt fence along rear of the existing seawall and along the northern boundary of the works area, adjacent to the RAAF Lake.
- Diversion bunds upstream of disturbed area.
- DTD constructed on a concrete slab with integral drains and pumping pits with rain and wash water collected and transferred to the WTP.
- Soil processing enclosure constructed on a concrete slab with integral drainage and pumping pits to transfer leachate and wash waters to the WTP.
To assist in progressing the groundwater reinjection regime proposed for treated groundwater, Enviropacific engaged consultants Senversa to undertake groundwater modelling to assess the potential impact to groundwater, Port Phillip Bay and RAAF Lake from the reinjection of treated groundwater.
A one week long trial injection test was undertaken on site to confirm the hydraulic parameters of the shallow aquifer and assess the feasibility of the reinjection of treated groundwater.
Image 8. The DTD was constructed on a concrete slab with internal drains and pumping pits
4. Environmental footprint and sustainability
A screening of remediation technologies was carried out by AECOM prior to the Project being tendered to determine the best technology to remediate the site. The screening considered the four key parameters required by EPA Victoria – technical, financial, logistical and timing. Sustainability was added as an additional criteria, which assessed the technologies’ relative energy intensiveness (carbon footprint) as well as whether the technology would generate a secondary waste stream which would require subsequent treatment or disposal. This screening process, which also considered the feasibility of each technology, indicated that ex situ thermal desorption would be the preferred technology to meet all these criteria.
The key achievement of this project in terms of environmental footprint and sustainability was that 70,000
tonnes of heavily contaminated soil was treated and reinstated on site, resulting in zero soil diversion to
landfill and more than 15 million litres of heavily contaminated water was treated and discharged on site
resulting in zero water removal from the site.
Historically, recalcitrant compounds in Australian soils have been disposed to landfill and projects have not achieved zero waste. The use of DTD technology in this instance, while being resource intensive, delivered a remarkable environmental result, completely destroying all contaminants in both the soil and water for reuse onsite. As the contaminants were destroyed, rather than immobilised or disposed, the project offered broke the chain of intergenerational transfer at the FTA site. While being a landmark result for a project of this scale in Victoria, it also delivered on the project’s objective to enable Defence to use the FTA Site for overnight camping and dry surface training within two years.
As a further sustainability measure, Enviropacific’s project team had planned to treat the activated carbon
from the water treatment with the DTD plant to further reduce off-site disposal, but at the auditor’s request this had to be disposed off site.
5. Monetary value and cost savings
The total project value was $32 Million. Value for money was delivered to the client by reusing materials wherever possible. This included reusing sheet piles and treated water discharged onsite.
The best value for money delivered to the client was sending no soil to landfill and no contaminated water off site. The cost for Department of Defence in landfill fees to dispose of the soil alone (not including loading, transportation and environmental management) would have been in the vicinity of $70 million, not withstanding the fact that Category A wastes are not permitted to be disposed to landfill. If the water couldn’t be treated within criteria, it too would have been transported offsite at a cost of around $20 million. In this instance, achieving zero waste was not only an environmental achievement but delivered a major cost saving.
6. Regulator and community consultation
Throughout the project, measures were taken to ensure that the treatment process complied with Commonwealth and State regulatory and legislative requirements, which included the ongoing environmental monitoring of emissions to atmosphere, groundwater and soil outlined above. Department of Defence, in consultation with Enviropacific, organised a number of measures to inform and engage the community, both prior to and during the project. Enviropacific were actively involved in the community consultation sessions throughout the project. These sessions, held approximately every six months, provided interested members of the community a chance to learn more about the works and ask questions.
Regular ‘What’s Happening at RAAF Base Williams, Point Cook’ flyers were sent out prior to works commencing on site and during the project, including general information about the
project and an invitation to the next community consultation session. Neighbouring residents could provide their contact details so they could be contacted directly about any works that
may affect them and there was a 24-hour hotline for complaints or questions.
An information hub was set up on the Department of Defence’s website (http://www.defence.gov.au/id/pointcook/Default.asp), to provide ongoing access to all community consultation
documents, Q&As, project updates and key documents. With all these measures in place, and due to the effective management of noise and air pollution at the site, there were no community or environmental complaints throughout the project.
7. Project innovations
The DTD plant used at the Point Cook site was custom-designed to solve the problem of reusing highly contaminated soil on-site. The remediation technology allowed rapid treatment of the organic hydrocarbon contaminated soil at rates of over 30 tonnes per hour. This allowed the site to be remediated and returned to operational use by the Department of Defence within a two year period.
Another innovation that this project required was a plant that could be highly transportable to a remote, environmentally sensitive site. The DTD plant was specifically designed to be set up on sites with limited or no facilities, in close proximity to environmental receptors and local communities, and allowed for zerowaste to landfill.
8. Verification processes
During the excavation process, validation samples and locations were collected by the Technical Advisor, AECOM and reported with results and locations provided in AECOM Remediation Cell Validation Reports. The purpose of the validation samples was to identify the degree of contamination within the marine clay, and to what extent the contamination had been removed.
The following soil validation was carried out as part of the remediation works:
• Excavation validation sampling was conducted after the excavation of the DNAPL impacted soils.
• Treated soil sampling was conducted every 100 m³ for confirmation of removal of contaminants, with a duplicate sample undertaken by the Technical Advisor every 1000 m³.
• Water from the WTP was sampled and analysed twice a week at several points within the system to monitor carbon breakthrough and to demonstrate treatment conformance.
• Imported fill validation sampling was undertaken to confirm that the material being imported to the site was not contaminated and fit for use at the FTA.
In addition to the soil validation sampling, groundwater sampling was conducted as part of the management of the dissolved phase contamination. All samples were collected and analysed in accordance with the requirements outlined in the project Quality Plan and in accordance with industry standard sampling guidelines such as the National Environmental Protection Measures (NEPM) 1999 for Contaminated Land.
Once construction of the DTD plant had been completed, a clean soil run was carried out to ensure all mechanical components of the plant were working as required. Following the clean soil run, Proof of Performance (PoP) testing was successfully undertaken, to demonstrate that the DTD plant was achieving regulatory targets in environmental emissions and treated soil concentrations. Emissions limits were derived by AECOM at the direction of Defence, based on a maximum 50% of the SEPP-AQM schedule A design criteria and schedule E criteria for Ground Level Concentrations. Additional PoP tests were successfully completed throughout the Project including: a second immediately following the initial test, a third test following three months of treatment and a fourth and final PoP test following the commencement of excavation of source zone B, to allow for possible differences in type and concentration of contaminants.
9. Project success measures
The general principle of the remediation was to comply with all Commonwealth regulations, and to meet the spirit and intent of Victorian environmental and OHS regulations, which were all successfully fulfilled. The key objectives for the project, as set by Defence, were all met.
Objective 1: Prevent the further migration of contamination offsite at concentrations that could adversely impact upon human health or the environment. Successfully achieving zero soil or water to landfill on the project meant that the contamination in the soil and groundwater is no longer present and able to impact the environment at the site or elsewhere.
Image 9. Revegetation of the FTA site
Objective 2: Enable Defence to use the FTA Site for dry surface training with overnight camping. After all remediation was complete, revegetation works took place on site. Revegetation included final surface preparation, importation of topsoil and planting of almost 8000 plants specific to the assumed Ecological Vegetation Classes (EVCs). The site is now able to be used for camping and training activities.
Objective 3: Mitigate Defence’s risk and long term liabilities associated with contamination of soil and groundwater at the FTA site.
With the soil and groundwater at the FTA successfully remediated and no contaminants remaining, the area no longer poses a risk to defence personnel or the surrounding area.
In addition to this there were no environmental or community complaints, no LTIs, no noise, air or dust emission complaints or exceedances and all soil was treated to within criteria for reinstatement on site. Four DTD Proof of Performance tests were completed and passed with no issues.
10. Industry knowledge and community engagement
During the project, Enviropacific held several large site visits for industry bodies and students including a visit from Australian Land & Groundwater Association (ALGA), Australian Contaminated Land Consultants Association (ACLCA) Young Professionals and Clean Up 2013 Technical Tour.
A local high school Year 10 class also visited the site for a tour where they were given an introduction to thermal treatment and the project as a whole, and taken for a walk around the site to witness the project in operation.
Enviropacific staff involved in the project have delivered presentations about the project at industry conferences such as Ecoforum and the upcoming Clean Up 2015 including:
• CleanUp 2013, Melbourne: Remediation of former fire training area by direct thermal desorption, RAAF Base Point Cook, presented by Bernie Morris.
• EcoForum 2014, Gold Coast: ‘Case Studies: Thermal Remediation’ session, which included:
a) Cameron McLean, chair and intro.
b) Point Cook Thermal Desorption Remediation Project, presented by Will Magnus.
c) Background on the Department of Defence Point Cook Site, presented by Tai Truong.
• ALGA 2015, Canberra: PFCs – including discussion on FTA WTP, presented by Damien McKay.
• ALGA 2015, Brisbane: PFCs – including discussion on FTA WTP, presented by Damien McKay.
• CleanUp 2015 Melbourne: Point Cook thermal desorption remediation project, to be presented by Will Magnus.