[0001 ] The disclosure relates to a permanent isolation system for hazardous waste, in particular to a geological repository adapted for permanent isolation of hazardous waste.

Background

[0002] The discussion of the background to the disclosure is intended to facilitate an understanding of the disclosure. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

[0003] A hazardous waste, in the Hazardous Waste in Australia 2017 Report, 30 May 2017, prepared for the Department of the Environment and Energy is defined as a waste that, by its characteristics, poses a threat or risk to public health, safety or to the environment. In national reporting this term is taken to correspond with: wastes that cannot be imported or exported from Australia without a permit under the Hazardous Waste (Regulation of Exports and Imports) Act 1989; wastes that any jurisdiction regulates as requiring particularly high levels of management and control, namely: regulated waste (Qld); trackable waste (NSW); prescribed waste (Vic); listed waste (SA and NT); or controlled waste (ACT, Tas and WA); additional wastes nominated as hazardous by the Australian Government. The term‘hazardous waste’ as used herein includes, but is not limited to, hazardous (chemical) wastes and low level radioactive wastes (LLW).

[0004] There are a range of industrial processes and activities that generate hazardous waste, in particular waste which consist of, or are contaminated with, one or more organic compounds, inorganic compounds, or low level radioactive wastes (LLW) such as naturally occurring radioactive materials (NORMs), disused sealed radioactive sources (DSRS) or other radioactive materials. Such processes and activities may include intentional manufacture, or arise as by-products of manufacturing facilities of products and articles such as plastics, paint, ink, pulp and paper, machinery and equipment, upholstery, textiles, packaging material,

electrical/electronic equipment, master batches, pellets, expanded polystyrene materials, paints, glass, fertiliser and agrichemicals, food products, adhesives, wood products and so forth. Hazardous waste may arise in a wide variety of processes including, but not limited to, metal coating and finishing operations, petroleum refining, metal extraction, smelting and refining, coal mining, use of pesticides or herbicides, tanning and wool scouring, fossil fuel electricity generation, meat, poultry and dairy processing.

[0005] In 2014-2015, Australia produced around 5.6 million tonnes of hazardous waste, which is about 9% of all waste generated (64 million tonnes) in this period. Generation of hazardous waste is increasing at a rate of approximately 9% a year.

[0006] Current hazardous waste management options include recycling,

chemical/physical treatment, landfill, biodegradation, incineration and storage or transfer.

[0007] Historically, some hazardous wastes were disposed of in landfills that included regular landfills with no or poorly designed active controls or specially engineered landfills with active controls like a liner and engineered cap barriers.. Landfills with only active controls eventually fail in the geological short term (years or decades) and chemicals can enter into the biosphere, potentially posing a threat or risk to public health, safety or to the environment.

[0008] Although long term storage of hazardous waste in underground pits is known, such facilities are not usually completely isolated from the biosphere. The

underground pits may be capped with aggregate materials through which rain, surface water and groundwater may percolate over time. Alternatively, the underground pits may be capped with concrete blocks, bitumen, high density polyethylene (HDPE) or other plastic material, but these are subject to failure over time and hence ingress of rain, surface water and groundwater.

[0009] As a result of these emerging and widespread environmental, health and safety problems, governments globally are now banning or beginning to ban surface landfill of hazardous waste that only relies on man-made barriers (active controls) and are endorsing geological repositories that rely on both man-made barriers (active controls) and natural barriers (passive control) that together are capable of

permanently isolating waste from the biosphere.

[0010] Geological repositories are facilities that provide the highest level of containment for hazardous waste (chemical waste) and low level radioactive waste (LLW) and isolation from the biosphere over geological time (hundreds of thousands to millions of years.

[001 1 ] Various embodiments of the present disclosure seek to provide an improved geological repository for permanent isolation of hazardous waste, in particular hazardous liquid waste such as organic compounds, inorganic compounds, or low level radioactive waste.

Summary

[0012] The disclosure provides a permanent isolation system for hazardous waste, in particular a geological repository adapted for permanent isolation of hazardous waste..

[0013] In one aspect there is a geological repository adapted for permanent isolation of hazardous waste, the geological repository comprising:

a near surface void having side walls and a floor disposed in a geologically stable formation, the geologically stable formation having low permeability, thereby providing a barrier to ingress of groundwater;

a ramp to the floor of said void for the movement of hazardous material transporting vehicles thereon;

an inflatable cover configured to provide a barrier between said void and a surface environment, the inflatable cover comprising a flexible top layer adapted to extend over the entire area of said void and having outer edge elements forming a plurality of skirt flaps disposed along its perimeter, an anchor to secure said skirt flaps to a surface perimeter of said void so as to maintain a seal between the inflatable cover and said void, one or more sealable access hatches in the inflatable cover to allow access of personnel and hazardous material transporting vehicles between said void and the surface environment; and a fan for inflating the inflatable cover. [0014] The geologically stable formation may comprise one or more layers of geological material, wherein any one of said layers may have low permeability.

Alternatively, cumulatively said layers may have low permeability.

[0015] In one embodiment, the anchor comprises a block with corresponding key elements disposed in opposing sides thereof to facilitate mating of adjacent anchors around a surface perimeter of the near surface void. The key elements may comprise a male element extending from one of the opposing sides and a female element forming a recess in the other of the opposing sides. The male and female elements may be shaped to allow lateral insertion or vertical insertion thereby forming an interlocking arrangement between adjacent anchors.

[0016] In another embodiment, the anchor comprises a block with a connecting plate to facilitate mating of adjacent anchors around a surface perimeter of the near surface void. The connecting plate may comprise a plate extending between and connecting two adjacent blocks.

[0017] In one embodiment, the anchor may be provided with a steel angle fixed on an upper side thereof in parallel alignment with longitudinal sides of the anchor. In use, the skirt flaps may be disposed between the steel angle and the anchor so as to provide a seal therebetween.

[0018] In another embodiment, the geological repository further comprises a biased cable system comprising a plurality of structural cables extending over the inflatable cover, wherein each end of the plurality of the plurality of structural cables is fixed to the steel angle of the anchor.

[0019] In one embodiment, the near surface void may be divided into a plurality of zones, whereby hazardous waste with compatible physico-chemical characteristics is deposited in the same zone and hazardous waste with incompatible physico-chemical characteristics is deposited in different zones spaced apart from one another. The plurality of zones may be laterally spaced from one another and/or vertically spaced from one another. [0020] In one embodiment, when filled with hazardous waste, the near surface void may be provided with a cap comprising a plurality of layers of compacted particulate materials.

[0021 ] In another aspect there is provided a method of permanently isolating hazardous waste from the biosphere, the method comprising:

a) constructing a near surface void having side walls and a floor disposed in a geologically stable formation, the geologically stable formation having low

permeability, thereby providing a barrier to ingress of groundwater;

b) constructing an access road to the floor of said void for the movement of hazardous material transporting vehicles;

c) providing a barrier between said void and a surface environment, the barrier comprising an inflatable cover having a flexible top layer adapted to extend over the entire area of said void and outer edge elements forming a plurality of skirt flaps disposed along its perimeter, said skirt flaps being secured to a surface perimeter of said void to maintain a seal between the inflatable cover and said void;

d) allowing access of personnel and hazardous material transporting vehicles between said void and the surface environment through one or more sealable access hatches; and

e) transporting and depositing hazardous waste on the floor of the near surface void.

[0022] In one embodiment, the method may further comprise the step of sorting and characterising incoming hazardous waste according to one or more physico-chemical characteristics. The hazardous waste may be deposited in said void in an

arrangement in accordance with the one or more physico-chemical characteristics of the hazardous waste material.

[0023] In one embodiment, said void may be divided into a plurality of zones, whereby hazardous waste with compatible physico-chemical characteristics may be deposited in the same zone and hazardous waste with incompatible physico-chemical characteristics may be deposited in different zones spaced apart from one another.

For example acidic hazardous waste will be deposited in one zone of said void spaced apart from another zone holding alkaline hazardous waste to avoid potential leakage, contamination and reaction between the acidic and alkaline hazardous waste. Similarly, acidic hazardous waste may be deposited in a zone spaced apart from another zone holding low level radioactive wastes.

[0024] The plurality of zones may be horizontally spaced from one another and/or vertically spaced from one another.

[0025] In one embodiment, the method may further comprise the step of immobilising the hazardous waste. In one form of the invention, the step of immobilising the hazardous waste may comprise packaging said waste in an impermeable membrane. In another form of the invention, the step of immobilising the hazardous waste may comprise converting said waste into a solid, load-bearing waste material. For example, the hazardous waste may be dispersed in a non-swelling clay, then mixed with a cementitious binder and, optionally, water and allowed to set.

[0026] In one embodiment, the solid load-bearing waste material may be formed as regular shaped bodies. The bodies may be suitably shaped to allow a plurality of bodies to be vertically or step-wise stacked and/or allow the bodies to abut against a plurality of adjacent bodies.

[0027] In another embodiment, the solid load-bearing waste material may be employed to fill voids between adjacent hazardous waste. For the example, pre-set solid load-bearing waste material may be used to fill voids between containers of hazardous waste, pipes, discarded equipment and so forth.

[0028] In one embodiment, after the hazardous waste is deposited in the near surface void, in particular when the near surface void is filled with hazardous waste, the method further comprises capping the near surface void. The step of capping the near surface void may comprise successively depositing and compacting a plurality of layers of particulate materials.

[0029] In another aspect there is provided a system to permanently isolate hazardous waste from the biosphere, the system comprising:

a) a geological repository as defined above;

b) a hazardous waste treatment plant for immobilising the hazardous waste into a solid, load-bearing material; and, c) a hazardous material transporting vehicle to transport and deposit the immobilised hazardous waste into the geological repository.

[0030] An alternative system to permanently isolate hazardous waste from the biosphere comprises:

a) a geological repository as defined above;

b) a hazardous waste receiving plant to characterise and sort incoming hazardous waste according to one or more physico-chemical characteristics; and

c) a hazardous material transporting vehicle to transport and deposit the immobilised hazardous waste into the geological repository in an arrangement determined by the one or more physico-chemical characteristics of the hazardous waste.

[0031 ] The immobilisation of hazardous waste in a form suitable to store indefinitely in a repository at an approved site or facility by the process defined above may comply with the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal and reduces the potential liability and compensation for third party damage or environmental damage.

[0032] Accordingly, in another aspect of the disclosure there is provided a method of issuing a Permanent Isolation Certificate, the method comprising the step of depositing a hazardous waste material in a geological repository as defined above.

[0033] In a further aspect of the disclosure there is provided a method of issuing a Permanent Isolation Certificate, the method comprising the step of permanently isolating hazardous material according to the process defined above.

[0034] In a further aspect of the disclosure there is provided a method of issuing a Permanent Isolation Certificate, the method comprising the step of exploiting a system for permanently isolating hazardous waste as defined above.

[0035] The term‘Permanent Isolation Certificate’ as used herein refers to a document attesting to permanent isolation of a known quantity of hazardous waste. Typically the document is issued in respect of a hazardous waste consignment by an operator of the geological repository to the owner of the hazardous waste

consignment. . “Permanent isolation” means in respect of a consignment of hazardous waste, the indefinite storage and isolation below ground in a manner which separates the hazardous waste from the biosphere for geological periods of time.

Brief Description of Drawings

[0036] Notwithstanding any other forms which may fall within the scope of the system and method as set forth in the Summary, specific embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

[0037] Figure 1 is a plan view of a geological repository adapted for permanent isolation of hazardous waste in accordance with one embodiment;

[0038] Figure 2 is a schematic representation of a front view of the geological repository shown in Figure 1 ;

[0039] Figure 3 is a schematic representation of a side view of the geological repository shown in Figures 1 and 2;

[0040] Figure 4 is a perspective view of an anchor in accordance with one embodiment as described herein;

[0041 ] Figures 4a and 4b are a plan view and an elevation, respectively, of an alternative anchor in accordance with one embodiment as described herein;

[0042] Figure 5 is a schematic representation of an arrangement between the anchor shown in Figure 4 or Figures 4a and 4b and an inflatable cover of the geological repository, so as to secure the inflatable cover to a surface perimeter of geological repository;

[0043] Figure 6 is a detail view of Figure 5;

[0044] Figure 7 is a sectional view of the anchor shown in Figures 5 and 6; and [0045] Figure 8 is a sectional view of the geological repository provided with a cap. Description of Embodiments

[0046] The disclosure relates to a permanent isolation system for hazardous waste, in particular to a geological repository adapted for permanent isolation of hazardous waste.

GENERAL TERMS

[0047] Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms "a", "an" and "the" include plural aspects unless the context clearly dictates otherwise. For example, reference to "a" includes a single as well as two or more; reference to "an" includes a single as well as two or more; reference to "the" includes a single as well as two or more and so forth.

[0048] Each example of the present disclosure described herein is to be applied mutatis mutandis to each and every other example unless specifically stated otherwise. The present disclosure is not to be limited in scope by the specific examples described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the disclosure as described herein.

[0049] The term "and/or", e.g., "X and/or Y" shall be understood to mean either "X and Y" or "X or Y" and shall be taken to provide explicit support for both meanings or for either meaning.

[0050] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. [0051 ] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[0052] The term“about” as used herein means within 5%, and more preferably within 1%, of a given value or range. For example,“about 3.7%” means from 3.5 to 3.9%, preferably from 3.66 to 3.74%. When the term“about” is associated with a range of values, e.g.,“about X% to Y%”, the term“about” is intended ot modify both the lower (X) and upper (Y) values of the recited range. For example,“about 20% to 40%” is equivalent to“about 20% to about 40%”.

[0053] All percentages by weight in the compositions are percentages by weight with respect to the total composition.

SPECIFIC TERMS

[0054] The term‘waste’ or‘wastes’ as used herein refer to substances which are disposed of or are intended to be disposed of or are required to be disposed of by the provisions of national law. The waste may have any one or more hazardous characteristics selected from a group of characteristics comprising: explosive, flammable, liable to spontaneous combustion, emit heat or gases upon contact with water, oxidising, liable to exothermic self-accelerating decomposition (eg, organic peroxides), corrosive, poisonous (acute), toxic (delayed or chronic), ecotoxic, or be capable, by any means, of yielding another material which possesses any of the aforementioned characteristics.

[0055] The term‘kaolin’ or‘kaolinite’ as used herein refers to a clay mineral of the group of industrial minerals having the chemical composition AI ₂ Si ₂ 0 ₅ (0H) ₄ . Kaolinite is typically a layered silicate mineral having one tetrahedral sheet of silica (Si0 ₄ ) linked by oxygen atoms to one octahedral sheet of alumina (AI Ob) octahedra. GEOLOGICAL REPOSITORY

[0056] Referring to Figures 1 to 3, there is shown a geological repository 10 adapted for permanent isolation of hazardous waste. The geological repository 10 includes a near surface void 12 having side walls 14 and a floor 16. The floor 16 of the near surface void 12 may be disposed at a depth of up to 50 m from the surface 18, in particular 20 m to 30 m from the surface 18. The floor 16 may be substantially horizontal with generally rectangular dimensions, for example 150 m x 80 m, although it will be appreciated that the dimensions of the floor 16 may vary. The side walls 14 may be pitched from 10° to 30° from the vertical, in particular about 20° from the vertical. In some embodiments, the side walls 14 may optionally include one or more steps 14a.

[0057] The near surface void 12 is disposed in a geologically stable formation. The term“geologically stable” as used herein refers to an area whose position on a tectonic plate means that it is not subject to earth movement or volcanic activity. It will be appreciated that most embodiments are located thousands of kilometres from the nearest tectonic plate boundary. In some embodiments, it is advantageous if the geologically stable formation is also located in an arid or a semi-arid climate zone or within areas of high surface evaporation, whereby evaporation rates exceed rainfall. The arid zone is defined as an area which receives an average rainfall of 250 mm or less per annum. The semi-arid zone is defined as an area which receives an average rainfall of between 250-350 mm per annum In this way, the potential for ingress of surface water and runoff into the near surface void is minimised.

[0058] The geologically stable formation is selected to provide a barrier to ingress of groundwater. The geologically stable formation may comprise one or more layers of geological material. In situ, any one of said layers may have low permeability.

Alternatively, said layers may cumulatively have low permeability. It may be advantageous if the geologically stable formation is remotely spaced from an aquifer or separated from an aquifer by an aquiclude, which is a solid, impermeable area, such as kaolinised granite or a low permeability clay, overlying the aquifer. In one particular embodiment, the floor 16 of the near surface void 12 may be disposed at least 1 -5 m above a granite formation. [0059] In some embodiments, the geologically stable formation comprises a kaolinite deposit. In contrast to other clay minerals, kaolinite has a low shrink-swell capacity, a low cation-exchange capacity, and may be regarded as self-annealing. Kaolinite deposits may extend to depths of over 250 m, although 30-50 m is more typical.

[0060] In other embodiments, the geologically stable formation comprises a rock salt or halite deposit. Rock salt behaves as an impermeable barrier to liquids and gases. Suitable rock salt deposits may extend to depths of 800 m, and have thicknesses of 250-300 m. Some deposits may have several layers of varying thicknesses from 250- 25 m.

[0061 ] The geological repository 10 may include a ramp 20 leading from the surface 18 to the floor 16 of said void 12 for the movement of personnel and vehicles for transporting hazardous material. The ramp 20 may be conveniently constructed adjacent to the side walls 14 of said void 12, as shown in Figures 1 to 3, so as to maximise storage space in said void 12.

[0062] An outer perimeter 22 of the geological repository 10 is defined by a bund 24 on the surface 18 which is spaced apart from an edge 26 of the near surface void 12. The bund 24 may comprise an earthworks mound. In some embodiments, the bund 24 may be approximately half the wheel height of the largest associated mobile plant vehicle on site. The bund 24 may be spaced apart from the edge 26 of the near surface void 12 by a distance of 10 m to 14 m.

[0063] The geological repository 10 also includes an inflatable cover 28 configured to provide a barrier between the near surface void 12 and a surface environment. The inflatable cover 28 comprises a flexible top layer 30 adapted to extend over the entire area of the near surface void 12. In one embodiment, when inflated, the inflatable cover 28 may have general dimensions of 90 m width, 180 m length and 27 m height above the surface 18. In use, the inflatable cover 28 may be inflated to an inflation pressure of at least 23 kg/m ² , in particular to an inflation pressure of between 40 kg/m ² and 50 kg/m ² .

[0064] The flexible top layer 30 may be a structural rated architectural vinyl coated polyester fabric, optionally coated in a coating such as polyvinylidene fluoride (PVDF) to protect the fabric from weather and wear over time. Seams between adjacent pieces of fabric may be joined by radio frequency welding to ensure that the flexible top layer 30 is capable of withstanding the full building air pressure when inflated and wind loads of 41 m/s with 3 second gusts.

[0065] A lower outer edge 32 of the flexible top layer 30 is provided with an inner skirt flap 34 and an outer skirt flap 36 disposed along its perimeter. The inner and outer skirt flaps 34, 36 are attached to the lower outer edge 32 of the flexible top layer 30 by radio frequency welding to ensure an air-tight seam therebetween. As will be described in more detail below, in use, the inner and outer skirt flaps 34, 36 engage an anchor 38 to secure the inner and outer skirt flaps 34, 36 to the surface 18. In this way, an inner and an outer seal is provided between the inflatable cover 28 and surface 18 proximal to the outer perimeter 22, thereby providing a barrier to the surface environment and the near surface void 12, preventing the ingress of rain and/or surface water.

[0066] In use, a plurality of anchors 38 may be adjacently disposed with respect to one another around the edge of the near surface void 12, spaced apart and proximal to the outer perimeter 22. One embodiment of the anchor 38 is shown in more detail in Figure 4. The anchor 38 is a generally rectangular concrete block 42 with corresponding key elements 44 cast into opposing sides 46 thereof to facilitate adjacent anchors 38 to mate with one another around the surface perimeter.

The key elements 44 comprise a male element 44a extending from one of the opposing sides 46 of the anchor 38 and a female element 44b forming a recess in the other of the opposing sides 46. The corresponding key elements 44 are generally square-shaped so that the male element 44a may be inserted laterally into the female element 44b of an adjacent anchor 38. However, it is within the scope of this description that the corresponding key elements 44 may take on other regular shapes or irregular shapes, or be shaped so that the male element 44a may need to be inserted vertically into the female element 44b thereby forming an interlocking arrangement between adjacent anchors 38.

[0067] In an alternative embodiment, the anchor 38 may be a generally rectangular concrete block 42 with a connecting plate 43 extending from opposing sides 46 to facilitate mating of adjacent anchors 38 around the outer perimeter 22 of the near surface void 12. The connecting plate 43 may comprise a plate such as cast-in steel plates or point lugs extending between and connecting two adjacent anchors 38.

[0068] As shown in Figures 5 to 7, the anchor 38 is provided with a steel angle 48 on an upper side 50 thereof disposed in parallel alignment with longitudinal sides 52 of the anchor 38. The steel angle 48 may be disposed to extend along an edge 54 of the male element 44a as shown in Figure 4. The steel angle 48 may be secured to the anchor 38 with a plurality of spaced apart anchor rods 56 which extend vertically into the anchor 38 through a horizontal side 58 of the steel angle 48.

[0069] In use, the lower outer edge 32 of the flexible top layer 30 is drawn to the anchor 38 so that the inner and outer skirt flaps 34, 36 extend beyond the longitudinal sides 52 of the anchor 38. The horizontal side 58 of the steel angle 48 is then fixed to the anchor 38 with the anchor rods 56, thereby fixing the inner and outer skirt flaps 34, 36 on either side of the anchor 38 and providing a seal therebetween.

[0070] The geological repository 10 also includes a biased cable system comprising plurality of structural cables 60 to provide rigidity and strength to the inflatable cover 28. The biased cable system may be a low bias cable system or a high bias cable system, It will be appreciated by the skilled person that the selection of a low bias cable system or a high bias cable system will be determined by several environmental and climatic conditions of the site, in particular anticipated range of wind velocity and prevailing wind direction at the site. The structural cables 60 extend over the length and width of the flexible top layer 30, as shown in Figures 2 and 3. The structural cables 60 comprise steel cables, such as galvanised steel aircraft cables, having swaged loop ends with thimbles 62. The structural cables 60 may have a diameter ranging from ¼” to 2” with a nominal breaking strength from 3.0 ton to 200 ton. The structural cables 60 may be coated with a polymeric material such as vinyl to protect the flexible top layer 30.

[0071 ] As shown in Figures 5 to 7, an upstanding side 64 of the steel angle 48 is provided with a plurality of spaced apart apertures 66 which are generally regularly spaced between the anchor rods 56. The apertures 66 are provided with respective shackles 68 to engage the thimbles 62 of the swaged loop ends of the cables 60, thereby providing anchor points for the plurality of structural cables 60.

[0072] The inflatable cover 28 includes one or more fans (not shown) for inflating the inflatable cover 28. The fan may be a single stage radial fan having a flow rate of from 30 m ³ /s to 52 m ³ /s and pressures from 250 Pa to 2500 Pa. Such fans are commonly used in underground mines for ventilation.

[0073] A plurality of mechanical dampers may also be provided to allow for increased ventilation during warm weather or to accommodate air change requirements. For example, a common reason to increase ventilation may be to disperse air

contaminants (e.g. diesel exhaust particulates) created by activities within void 12.

[0074] The inflatable cover 28 may also include one or more sealable access hatches 70 to allow access of personnel and vehicles to transport hazardous material from the surface environment to the void. Personnel access hatches 70a may take the form of low-leakage three-leaf revolving doors. Vehicle access hatches 70b may take the form of a steel frame configured to provide a vehicular airlock.

[0075] The access hatches 70 may be fitted with flexible fabric shrouds attached to the flexible top layer 32 by radio frequency welding. The flexible fabric shrouds are configured to withstand the full building air pressure, and to allow for normal building movement without becoming taut between the fixed access hatches 70 and the inflatable cover 28. Generally, the flexible fabric shrouds will be manufactured from the same flexible material as the flexible top layer 32 and may be of double wall construction for insulation. The door openings of the access hatches 70 may additionally be fitted with a plurality of flaps which may be secured open when the structure is in use. The flaps may be laced closed, so that the doors of the access hatches 70 may be removed for repair or service without causing a significant air pressure drop within the geological repository.

[0076] In use, the void may be divided into a plurality of storage zones, whereby hazardous waste with compatible physico-chemical characteristics may be deposited in the same storage zone or an adjacent storage zone, and hazardous waste with incompatible physico-chemical characteristics may be deposited in different storage zones spaced apart from one another.

[0077] The storage zones may be laterally spaced from one another or vertically spaced from one another.

[0078] The geological repository 10 may further include a cap 72 comprising a plurality of layers of compacted particulate materials. The cap 72 may be positioned over the near surface void 12. Referring to Figure 8, the cap 72 includes a plug 74 extending between the side walls 14 of the near surface void 12 and an overlying shallow dome 76. The plug 74 may extend up to 7 m below the ground surface 18 and comprise one or more compacted layers 78 of particulate materials. In the

embodiment shown in Figure 8, the plug 74 includes a lower layer 78a of kaolin waste (i.e. compacted backfill) and an upper layer 78b of mixed laterite and granite. The dome 76 extends over the plug 74 and, optionally, to the bund 24 to cover and seal the near surface void 12. The dome 76 includes a lower layer 80a of low permeability particulate material (e.g. clay) and an upper layer 80b of compactable particulate material (e.g. kaolin) of approximately 3-4 m thick. The dome 76 is shaped to shed any landing rainfall. Following completion of a monitoring period of the site, soil and topsoil may be deposited over the dome to allow for rehabilitation. The soil layers may provide an integral part of the cap 72, providing a‘store-and-release’ function for rainwater.

[0079] Although specific examples of particulate materials have been suggested above, it will be appreciated that other particulate materials or mixtures of particulate materials may be deposited and compacted as contributing layers to the cap. Other suitable examples of particulate materials include, but are not limited to, granite, laterite, silicates, mottled clays, clayey sand and so forth.

[0080] It will be appreciated that, in some embodiments, the inflatable cover 28 may be removed after the plug 74 has been installed so that construction of the overlying shallow dome 76 of the cap 72 may be completed.

[0081 ] The geological repository 10 as described herein is distinguished from landfill. Historically, regular landfill had no or poorly designed active controls, or specially engineered landfills were designed with active controls such as a clay liner and engineered cap barrier. Such landfills relied solely on man-made barriers which inherently fail over geological time, allowing chemicals to enter into the biosphere and potentially posing as a threat or risk to public health, safety or to the environment.

[0082] Moreover, known geological repositories rely solely on passive controls which do not require ongoing monitoring as they can be quantified as being passively safe through geological time.

[0083] In contrast, the geological repository 10 as described herein includes a combination of carefully selected active and passive control measures, which may be referred to as a multi-barrier system that is capable of permanently isolating waste from the biosphere to protect the environment and human health. The geological repository 10 as described herein relies on a plurality of contingency mechanisms underpinned by natural barriers which provide passive control and man-made barriers which provide active control. The man-made barriers (active controls) include processes such as waste acceptance and characterisation, waste segregation, treatment and placement techniques and engineered design such as packaging, cell construction (liners), closure controls (caps), and institutional control period

assurances and insurances. Additionally, the natural barriers (passive controls) include site selection, geology (suitable host rock, low permeability, low erosion rates), environment (semi-arid and separated from groundwater), geologically stable with low earthquake risk that combine to offer superior isolation to active controls over geological time.

METHOD OF PERMANENTLY ISOLATING HAZARDOUS WASTE

[0084] Hazardous waste may be permanently isolated from the biosphere by constructing a geological repository 10 as previously described, and transporting and depositing hazardous waste in the geological repository 10. It will be appreciated that the geological repository 10 may be constructed according to known civil construction techniques using conventional earth moving equipment.

[0085] Incoming hazardous waste may be characterised and sorted according to one or more physico-chemical characteristics. The one or more physico-chemical characteristics may correspond to one or more inherent hazardous characteristics.

For example, the waste may have any one or more hazardous characteristics selected from a group of characteristics comprising: explosive, flammable, liable to

spontaneous combustion or generating heat or gases, poisonous (acute), toxic (delayed or chronic), ecotoxic, radioactive or be capable, by any means, of yielding another material which possesses any of the aforementioned characteristics.

[0086] Alternatively, the one or more physico-chemical characteristics may be selected from a group of characteristics comprising: acidic, basic, radioactive, oxidative, reductive, hydrophilic, hydrophobic, and so forth.

[0087] Prior to transporting and depositing the hazardous waste in the geological repository, the hazardous waste may undergo an immobilisation process. The immobilisation process may be selected to ensure that, over a prolonged period of time (e.g. > 100 years) the hazardous waste cannot leak or be leached from its deposition site within the geological repository 10, and subsequently mix with and react with other hazardous waste within the geological repository 10, or leak or be leached from its deposition site within the geological repository 10 into the biosphere.

[0088] Some types of hazardous waste may be sufficiently immobilised by packaging said waste in an impermeable membrane.

[0089] Other types of hazardous waste, such as liquid hazardous waste, may be immobilised by converting said waste into a solid, load-bearing waste material. For example, the hazardous waste may be mixed with a binder and a setting agent and allowed to set to produce the solid, load-bearing waste material. In some

embodiments, the solid, load-bearing waste material may be formed into regular shaped bodies. Conveniently, when depositing the immobilised waste material into the geological repository 10, a plurality of regular shaped bodies may be stacked vertically or in a step-wise arrangement against the side walls 14 of the near surface void 12 or arranged laterally with respect to one another so that adjacent regular shaped bodies abut one another to maximise the volume of waste deposited and stored in the geological repository 10. [0090] In alternative embodiments, the solid, load-bearing waste material may be deposited in bulk into the geological repository and allowed to set.

[0091 ] In other embodiments, prior to allowing the immobilised waste material to set to a solid, load-bearing waste material, the plastic (flowable) immobilised waste material may be deposited in any gaps between prior deposited packaged hazardous waste or regular shaped bodies of solid, load-bearing waste material to maximise the volume of waste deposited and stored in the geological repository 10.

[0092] It will also be appreciated that non-waste containing cement grout may also be used to fill void spaces within deposited waste materials.

[0093] The step of depositing the hazardous waste may also include compacting the hazardous waste to maximise the volume of waste deposited and stored in the geological repository 10. Compacting the hazardous waste may be achieved by employing conventional earth compacting equipment as used in civil engineering and construction activities.

[0094] As discussed previously, hazardous waste with compatible physico-chemical characteristics may be deposited in the same storage zone or an adjacent storage zone, and hazardous waste with incompatible physico-chemical characteristics may be deposited in different storage zones spaced apart from one another. The storage zones may be laterally spaced from one another or vertically spaced from one another.

[0095] It will be appreciated that when the floor 16 of the near surface void 12 is fully occupied with deposits of hazardous waste, immobilised or otherwise, a subsequent floor may be constructed immediately above said deposits and additional deposits of hazardous waste, immobilised or otherwise may be deposited thereon. Similar placement of compatible and incompatible types of hazardous wastes in appropriate storage zones will also apply, taking into consideration vertical spacing of the storage zones as well as lateral spacing of the storage zones of incompatible waste materials.

SYSTEM FOR PERMANENTLY ISOLATING HAZARDOUS WASTE [0096] The system to permanently isolate hazardous waste from the biosphere may include the geological repository as described previously and a hazardous material transporting vehicle to transport and deposit the hazardous waste, immobilised or otherwise, into the geological repository 10.

[0097] The system may also include a hazardous waste receiving plant to

characterise and sort incoming hazardous waste according to one or more physico chemical characteristics; as described previously. The hazardous waste will be deposited in the geological repository 10 in an arrangement determined by the one or more physico-chemical characteristics of the hazardous waste.

[0098] As will be evident from the foregoing description, hazardous waste may be stored indefinitely in the geological repository 10 as described herein in compliance with the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal which reduces the potential liability and compensation for third party damage or environmental damage.

[0099] A company that generates hazardous waste either directly or indirectly through its operations may transport the hazardous waste to a geological repository as described herein to store, treat or permanently isolate, said hazardous waste material. It will be appreciated that hazardous waste may be‘stored’ in a manner in which it may be subsequently retrieved for recycling or processing to extract one or more valuable components (e.g. metals, energy). Treating hazardous waste may optionally include immobilisation of the hazardous waste as described above. On acceptance of the hazardous waste, a waste acceptance notice is first issued. If a permanent isolation of the hazardous waste service is provided then a Permanent Isolation Certificate is issued in compliance with the Basel Convention, wherein risk and title is transferred to the operator of the geological repository 10. If a storage services is provided then a Storage Certificate is issued and only risk is transferred to the operator of the geological repository 10. For permanent isolation service, the hazardous waste may then be converted to an immobilised waste material as described herein and deposited in the geological repository 10 to permanently isolate the immobilised hazardous waste material. [0100] The Permanent Isolation Certificate may act as documentary evidence for the company’s sustainability reporting, operational auditing and financial auditing, and may assist the company’s entitlement to accounting treatment that allows the removal of contingent liability provisions in respect of the hazardous waste that has been immobilised. For example, under Australian laws, generators of hazardous waste have a“cradle to grave” responsibility for the waste. International (I A) and Australian Accounting Standards Board Provisions, Contingent Liabilities and Contingent Assets (AASB 137) require a waste producer to maintain an accounting provision equal to its best estimate of the future cost of properly disposing of that waste.

[0101 ] That provision represents a liability of the waste generator and a burden on its financial standing. It must be maintained until it is no longer probable that there will be any further cost involved in dealing with the waste. Further the provision must be reviewed periodically to ensure that it is adequate and adjusted if necessary. Following the issue of a Permanent Isolation Certificate, the waste generator no longer has any future costs that would meet criteria for recognition or disclosure under AASB 137. Hence the provision may be reversed.

[0102] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.