WO2005042106A2

WO2005042106A2 - Fire training ground

Info

Publication number: WO2005042106A2
Application number: PCT/GB2004/004508
Authority: WO
Inventors: Quintin Anthony Murfin
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-10-24
Filing date: 2004-10-22
Publication date: 2005-05-12
Anticipated expiration: 2006-04-24
Also published as: GB0324909D0; WO2005042106A3

Abstract

A fire training ground comprising (i) a first zone comprising a fire training rig, fuel distribution means and waste material collection and disposal means connected to an attenuation tank, and (ii) a second zone comprising an evaporative storage cell, natural water supply means and water distribution means, whereby the first and second zones are connected by valved connecting means.

Description

Fire Training Ground

The present invention is primarily directed towards a fire training ground, and in particular one for use at airports. It is also directed towards a water neutral system of operation of a fire training ground. The invention further extends to the provision of a permeable paving system which is capable of supporting repeated heavy loading.

In airports it is necessary to have a full operational fire service on site ready to respond to emergencies. These fire services are required to undertake regular fire training exercises to ensure the maintenance of a high operating standard of both the fire crew personnel and the fire tenders themselves. In many countries this requirement is set out in official aviation policy documents.

In many existing cases, there is little or no control over the flow of liquids from the fire training ground site and therefore water, foam and other contaminants from the training can permeate into the ground and pollute watercourses and aquifers below. With ever more stringent requirements on environmental protection being introduced, there is a need for a system where the flow of "dirty" liquids can be controlled. In addition, the quantity of water required for regular fire training exercises can place a significant strain on the local water distribution system and there is therefore a need to provide means for reducing this strain.

In many airports, fire training facilities consist of training rigs which are located away from the runways and public areas. These training rigs may be specially constructed or comprise old aircraft which are arranged to be set on fire in specific ways under controlled conditions to simulate the different types of fire which may be encountered at an airport. The rigs are generally located on an area of concrete or other suitable material. However, there is little or no control of the water, foam, oil and other contaminants once they leave the concrete area. In many cases, these materials simply flow off the fire training site and drain through the ground and rocks and into the watercourses and aquifers.

Many airport training sites use aeration lagoons with paddles in order that the biological degradation of the used materials may take place. This system of lagoons does not, however, deal with foam that has been used in a fire situation because of its constituent persistent chemicals.

There is therefore a need for greater control of the effluent from a fire training ground. It is an object of the present invention to provide an apparatus and method for the control of liquid flow to and from a fire training ground.

US3831889 shows an airport runway which is arranged over a liquid reservoir. The runway is designed to be suitable for short take off and landing planes. The reservoir includes liquid displacement means such that the level of the liquid may be raised to extend above the grid surface of the runway to clear it of snow and ice.

It is a further object of the present invention to provide an integrated system in which the fire training ground is largely water neutral.

WO96/12067 is directed towards a paving system for spillage and flood management wherein a perforated pavement covers a deep substrate of crushed stone. This system is able to provide temporary storage for a relatively small amount of water in the event of, for example, chemical spillage or a flood before the liquids are dispersed. There is no substantial structural strength to the pavings to enable it to carry heavy vehicles and the s stem is not adapted to store considerable quantities of water for extended periods.

It is another object of the present invention to provide a permeable paving system capable of storing substantial quantities of water and supporting repeated heavy vehicle loading.

According to one aspect of the present invention there is provided a fire training ground comprising: (i) a first zone comprising a fire training rig, water distribution means, fuel distribution means and waste material collection and disposal means connected to an attenuation tank, and (ii) a second zone comprising an evaporative storage cell, natural water supply means and water distribution means, whereby the first and second zones are connected by valved connecting means.

The fire training rig may be of any suitable form either comprising an old aircraft which has been suitably modified for training purposes or a custom made structure designed to simulate one or more aircraft. It may be formed of material which is not substantially damaged by repeated exposure to fire under fire-training conditions such that it may be re-used many times before it requires replacement.

The water distribution means of the first zone may be nozzles for spraying water onto the fire training rig prior to the fuel being ignited. This is known as a drench and is used to douse the rig prior to the fire training to help maintain the structure of the rig for future training. This avoids the need to introduce new rigs on a frequent basis when the previous rig burns out beyond a point where it is safe to use. The water distribution means of the first zone may also include nozzles which spray water down onto the top surface of the ground to assist in breaking up any foam as it is used in the fire training.

The fuel distribution means may comprise any suitable pumps and nozzles to take the fuel from storage vessels located away from the fire training rig to the appropriate part of the rig for the training from where it may be ignited. The fuel may be gas or oil, for example liquefied petroleum gas (LPG) or kerosene.

The waste material collection and disposal means may comprise a drain in the central region of the first zone, and inclined top surfaces of the ground of the first zone leading down to the drain. There may, alternatively, be two or more drains situated around the first zone to collect and transport the waste materials from the fire training rig to the attenuation tank before they can contaminate the surrounding ground.

Alternatively or in addition there may be an external drainage ditch or moat running round the outer perimeter of the first zone such that any waste material which passes outwardly of the fire training rig is collected before it contaminates the surrounding ground.

The attenuation tank may comprise a suitably large volume tank to simultaneously hold the waste material from a number of fire training scenarios. The attenuation tank may additionally have an oil water separator tank directly associated with it to remove any oil or other hydrocarbon contaminants from the waste material. This may be a gravity separator.

The attenuation tank may also have an additional water supply means or it may be directly connected to the evaporative storage cell of the second zone. The additional water supply means may be used to dilute the contents of the waste material before further treatment or disposal. The attenuation tank may have an outlet directly into the local public sewer for discharging the waste material in a controlled fashion once it has been appropriately treated.

The second zone may be located adjacent to the first zone or it may be located at some distance from the first zone but be connected thereto by suitable connecting means, for example pipes. The second zone may extend substantially around the outside of the first zone enclosing it completely. The second zone may, for example, double up as a runway or a taxiway at an airport in situations where space is at a premium. Taxiways take up a considerable amount of space at airports and the planes are only travelling relatively slowly over the surface so that there are not the same issues with surface water as may be present on a runway where planes are taking off and landing at high speeds.

The top surface of the second zone may be permeable to liquids. The top surface may be constructed of any suitable permeable means selected from, for example, a single section which includes holes or slots or grooves, or by the arrangement of a number of paving slabs or pavers which may have holes through them and/or be arranged such that there are narrow channels on one or more sides of each slab or paver.

The evaporative storage cell of the second zone may be located under the top layer of permeable material and may extend across substantially the whole of the area covered by the permeable top surface. The evaporative storage cell may be of such a size that it can hold a substantial quantity of water collected without discharging any of the water. The size and capacity of the evaporative cell may be dictated by the local climatic conditions. The natural water supply means of the second zone may be any means capable of collecting natural precipitation or they may be means for collecting water from the ground, for example through bore holes.

The water distribution means of the second zone may be an outlet directly to the local sewer, pipes connecting the evaporative storage cell to an outlet tap or to the attenuation tank of the first zone, or a series of nozzles arranged to spray the water from the evaporative storage cell on to the top surface of the second zone. The water may be sprayed on to the top surface of the second zone when the prevailing weather conditions are favourable for evaporation of the water, for example when one or more of the following conditions is present: the sun is shining, the air temperature is high, the relative humidity of the air is low and there is a breeze ensuring a good flow of air over the second zone ensuring that the air above the zone does not become saturated.

When the conditions are not suitable for evaporation, which may for example be during the winter months in most temperate climates, the water may either be held in the evaporative storage cell, or used in fire training as the drench water or supply water for the tenders, or fed in a controlled manner to the local sewer. Since the discharge from the evaporative cell to a sewer is controlled, this can be done at times when the sewer is not overloaded, for example during the night.

The valved connecting means between the first and second zones may be one or more pipes controlled by one or more valves. The valve or valves may be open when there is no fire training taking place so that any precipitation which falls on the first zone may be collected in the waste material collection means and diverted before they reach the attenuation tank to pass to the evaporative cell. This uncontaminated water may then be handled in the same way as the water which falls directly on the surface of the second zone.

When fire training is about to take place, the valve or valves may be shut so that the waste material from the fire training does not contaminate the evaporative cell but passes directly to the attenuation tank as described above. The valve or valves can remain closed after the completion of the fire training until measurements confirm that there are no more contaminants on the surface of the first zone or in the waste material collection means.

The operation of the fire training ground may be controlled centrally by control means which co-ordinate the water and fuel distribution in the first zone, the valves in the connecting means between the first and second zones, and the water distribution means from the second zone. The control means may include means for measuring the prevailing weather conditions to determine the appropriate combination of water distribution means from the second zone. In particular, the control means may react to changes in the local conditions and change the combination of water distribution means from the second zone. In the event that nozzles are being used to spray water on to the top surface of the second zone for evaporation, the selection of nozzles is controlled to ensure that, taking into account the prevailing wind, they do not spray outside the zones.

The control means may also store historical meteorological data sixch that they may be operated by remote control or even from off the site. Data may be stored such that, if a wind of a particular strength from a particular direction is measured, the control means can react to open or close nozzles to ensure that sprayed liquid remains within the zones. According to another aspect of the present invention there is provided an integrated system for operation of a fire training ground is largely water neutral, comprising a fire training ground comprising: (i) a first zone comprising a fire training rig, water distribution means, fuel distribution means and waste material collection and disposal means connected to an attenuation tank, and (ii) a second zone comprising an evaporative storage cell, natural water supply means and water distribution means, whereby the first and second zones are connected by valved connecting means, in which natural water is collected in the evaporative cell of the second zone, and the evaporative cell then provides water to the water distribution means for the first zone and any surplus water from the evaporative cell is stored and subsequently disposed of by means of evaporation from the top surface of the second zone.

The optional features discussed above in connection with the fire training ground apply equally to this aspect of the invention.

According to a further aspect of the present invention, there is provided a permeable paving system isolated from the surrounding ground capable of supporting repeated heavy vehicle loading, the paving system comprising, in the following order: (a) a top layer of permeable concrete or clay pavers; (b) a layer of small single size grit laying course material; (c) a thicker layer of Course Graded Aggregate; (d) a substantially thicker layer of larger graded stone; (e) one or more layers of rigid liquid storage cells; (f) a layer of small single size grit bedding course; (g) a film of high density polyethylene (HDPE); (h) a thicker layer of material used as Type 2 bedding stone; and (i) a layer of clay lining (GCL). The depths of the layers may vary and are calculated in relation to the volume of water which may need to be stored. The first four layers are permeable to allow water (and other liquids) to permeate down to the rigid liquid storage cells. The capacity of these rigid liquid storage cells may be such that they can comfortably hold all water collected during wet periods where evaporation is not available as a means to discharge the water. The capacity will therefore vary considerably from location to location.

In some temperate climates, it may be that the capacity of the evaporative cells should be calculated to hold up to half of the average annual rainfall falling on the top surface of the permeable pavers without discharging any of the water. This would then provide sufficient capacity to store the water during the parts of the year when evaporation is not available, for example during the winter. Once the weather warms up, the water may be discharged on to the top surface and evaporated off. During the summer months, when rainfall is lower, the cells may be largely emptied in anticipation of the wetter winter months.

In other climates with mild winters where evaporation may be available for most or all of the year, the capacity of the evaporative storage cell may be substantially smaller thereby incurring lower capital costs.

The permeable pavers may be of a thickness in the range of 50-80mm, for example 65mm thick. They may be made of concrete, clay or any suitable material and they may have one or more holes in them to allow liquid to pass through them. The pavers may be arranged in any suitable pattern which is structurally stable for heavy vehicular use under all normal conditions. The top surface must retain its structural integrity under heavy vehicular usage while driving in straight lines and while turning and therefore applying torque to the pavers. The pavers may be arranged in a herringbone pattern to permit permeability between the pavers while ensuring stability for heavy vehicle usage.

The small single size grit laying course material may be of a size between 4 and 8mm, for example 6mm dimension. The layer may be between 40 and 60mm thick, for example 50mm.

The Course Graded Aggregate may be of a size between 10 and 30mm in dimension, for example 10 to 20mm. The layer may be between 130 and 170mm thick, for example 150mm.

The larger graded stone may be of a size between 40 and 140mm in dimension, for example 50 and 125mm. The thickness of the layer may be between. 1100 and 1500mm, for example 1300mm.

The rigid liquid storage cells may be any suitable honeycomb structure with a large void capacity for storing liquids and high structural strength. A non- limiting example of a suitable material is Permavoid (RTM) storage cells. There may be two or more layers of these storage cells arranged to lay one layer directly on top of the other to provide a larger reservoir for the collection of water. The number of layers will depend on the storage capacity required which will be calculated to take into account the local climate. The cells may each be of a size 100-200mm deep, for example 150mm deep.

The single size grit bedding course may be of the same dimension as layer (b) or it may be different. The thickness of this layer may be between 80 and 120mm, for example 100mm. The HDPE provides a first layer of impermeable material thereby isolating the system from the surrounding ground. The material may be of a thickness in the range of 1.5 to 2.5mm, for example 1.9mm thick.

The material used as Type 2 bedding stone may be recycled material and the layer may be between 250 and 350mm thick, for example 300mm thick.

There may be a second layer of impermeable HDPE to ensure isolation from the surrounding ground. This may be placed between the layer of Type 2 bedding stone (layer (h)) and the GCL (layer (i)). This additional layer may be of the same thickness as layer (g). The layer of GCL may have a thickness in the range of 5 to 7mm, for example 6mm.

The system may additionally include woven geotextile layers between one or more of the layers to prevent materials from one layer intruding into another. In particular, there may be a woven geotextile layer between layers (d) and (e) above. Further, there may be a woven geotextile layer between layers (f) and (g) above. The woven geotextile layer may be any suitable material.

Such a paving system is completely isolated from the surrounding ground, is permeable to precipitation from above which lands on the top surface, has means to collect and store the natural water and is also capable of withstanding repeated heavy vehicle loading. For example, the paving system may withstand the operation of 32t three axle fire tenders with little or no maintenance over a 25 year period.

Normally, trafficked areas have to be specifically designed to avoid the ingress of moisture since conventional road construction materials lose much of their strength when saturated. The additional challenge for the present inventors was to design a structure which was capable of holding substantial quantities of water underground (for example up to 2200m of water) but which was still capable of supporting the regular use of heavy vehicles, for example multiple fire tenders.

In a specific embodiment of the present invention there is provided a permeable paving system isolated from the surrounding ground capable of supporting repeated heavy vehicle loading, the paving system comprising, in the following order: (a) a top layer of 65mm of permeable concrete or clay pavers; (b) a 50mm layer of 6mm single size grit laying course material; (c) a 150mm layer of 20mm to 10mm Course Graded Aggregate; (d) a 1300mm layer of 125-50mm graded stone; (e) woven geotextile material; (f) two layers of 150mm deep Permavoid (RTM) Storage Cells; (g) a 100mm layer of 6mm single size grit bedding course; (h) woven geotextile material; (i) a 1.9mm thickness of HDPE; . (j) a 300mm layer of recycled material used as Type 2 bedding stone; (k) a 1.9mm thickness of HDPE; and (1) a 6mm thickness of GCL.

In some locations, layer (k) may not be necessary with one layer of HDPE providing sufficient impermeability from the surrounding ground.

The invention may be put into practice in a number of ways and one specific embodiment is shown here by way of example with reference to the following figures, in which: Figure 1 is a plan view from above of a fire training ground according to the present invention;

Figure 2 is a simplified block diagram of a water neutral water handling system according to the present invention; Figure 3 is a schematic cross section of a permeable paving system according to the present invention.

Figure 4 shows graphically the results of the heavy vehicle loading test on the permeable paving system shown in figure 3 and the shape of the deformed surface after full scale testing; and Table 1 shows the results across the test area which formed the basis for the graph of figure 4.

Figure 1 shows a fire training ground 1 in which the first zone 3 is an inner zone which includes the fire training rig 5, and the second zone 7 is an outer zone which completely surrounds the first zone. The inner zone is contoured inwardly to a drain at the centre (not shown). The fire training rig also has water and fuel supply means which extend from the evaporation cell below the ground in the outer zone and from the fuel tanks 9.

The drains in the inner zone are connected by means of pipes to an attenuation tank 11 which is shown to be outside the outer perimeter of the outer zone, but could equally be positioned under the inner zone. The attenuation tank is linked to a water oil gravity separator 13 which in turn is linked to a pump 15 which controls the discharge from the attenuation tank 11 to the sewer 17.

The outer zone 7 has a permeable upper surface leading to evaporative storage cells which are capable of holding up to half of the average annual rainfall falling on the top surface of this zone without discharging any of the water. This has been calculated for Jersey airport where the evaporative cell has been sized to accommodate the highest recorded annual rainfall period from April 2000 to March 2001; a cell volume of 2200m³ achieved this.

The outer zone also includes a number of nozzles 19 which are shown systematically arranged around the exterior of the zone, but they may be arranged appropriately for the geological location of the fire test rig. Their location and operation will be determined by the prevailing conditions, in particular the wind direction. The evaporative storage cell may also collect and store water from the surrounding ground through one or more boreholes, with the flow of water being controlled by scavenge pumps 21.

The overall operation of the fire training ground is controlled by control means located on site at 23. These control means may include means for taking meteorological measurements to help control the use of the nozzles 19. The system is therefore able to react to changes in the weather. If there is substantially no wind, it may be appropriate to have all the nozzles activated to spray water on to the top surface of the outer zone. However, if the wind is blowing from a particular direction, some nozzles may not be activated, as any water they spray would be blown away from the outer zone and outside the control of the system. If the wind direction changed, the selection of nozzles would change and the control system is set up to do this automatically. The system stores historical data of wind conditions (speed and direction) and of groupings of nozzles appropriate for the conditions and reacts to any changes in the prevailing conditions. This may even be done by remote access away from the fire training ground.

Around the outer perimeter of the outer zone 7 runs an impermeable skin which effectively cups and insulates the complete fire training ground, the skin extending below the bottom of both the evaporative storage cell and the attenuation tank. This ensures that the system is completely isolated from the surrounding ground except where there are controlled inlets (from the boreholes) or outlets (to the sewers).

Figure 2 shows a simplified block diagram of a water neutral water haαdling system as exemplified by a fire training ground according to the present invention. As described above, there are two zones, a first zone 3 and a second zone 7. They may be arranged as an inner and an outer zone or they may be separated by some distance and linked by suitable piping. The second zone may, for example, be located under the taxi way of an airport, thereby making more efficient use of that space.

The second zone includes an evaporative storage cell beneath a permeable top surface. This enables the cell to collect natural water from precipitation 20 and by means of water collected from bore holes as controlled by scavenge pumps 21. If the level of groundwater is too high and the capacity of the cell to accept more water is low, the scavenge pumps can feed this water directly into the sewer 17.

The evaporative cell has the capacity to store significant quantities of water without discharging any water for an extended period. For example, as described above, in Jersey the cell has been sized to accommodate and deal with the highest recorded annual rainfall period with a cell of capacity 220Om³. However, the system will, in operation, have a regular flow of water into and out of the system. During the warmer months, a substantial portion of the stored liquid will be sprayed onto the top surface of the second zone and will be allowed to evaporate. This minimises the duty on the local sewer system. The stored water may also be used all year round as both a drench 16 for the fire training rig and as a water supply 18 for the fire tenders who are taking part in the training exercise. This avoids, or at least minimises, the call on the local public water distribution system and is known as "rainwater harvesting".

If the level of the water in the cell becomes too high and cannot be discharged by any of the means discussed above, then it can be fed (in a controlled manner) to the public sewer 17. However, the control of this discharge means that the water can be fed to the sewer at times when it is not already overloaded, for example during the night.

The first zone 3 is fed with drench water 16 from the evaporative cell and also by water and foam from the fire tenders 6. This contaminated material (which may also include oils and other hydrocarbons) is collected and fed to the attenuation tank 11. This tank may also be fed by water 12 from the evaporative cell or from the boreholes/scavenge pumps 21. The waste from the first zone which enters the attenuation tank may be high in BOD (Biological Oxygen Demand) due to the presence of fire fighting foam. Holding this material in the attenuation tank 11 allows the material to settle and thereby avoid problems with foaming, and also to be diluted with water to reduce the BOD load before it passes through the oil water separator 13 to a pump 15 where it is pumped at a controlled flowrate into the public sewer. There may be further additional treatments included after the oil water separation to further cleanse the waste material before it is passed to the local sewer.

The usage of the fire training ground will vary with the size of the fire service(s) using it, as well as the training activity being carried out. It is likely that it will not be in use every day and there may well be relatively large periods of time where the water being collected in the first zone by means of the drain and moat is not contaminated. Accordingly, the system includes a switch valve 14 to allow flow of this non-contaminated water from the first zone into the evaporative cell of the second zone. From there it may be handled in the same way as before - evaporation, used as a drench, supply to fire tenders, or passed to the attenuation tank to dilute the BOD or passed directly to the sewer as appropriate.

This system accordingly does not draw on the local water distribution system to support the considerable requirements to run fire training. It also does not pollute the natural environment as the discharge from the fire training ground is collected and treated before it is discharged into the local sewer system under controlled conditions.

Figure 3 shows, in cross section, a permeable paving system and evaporative storage cell according to an embodiment of the present invention. In particular, this may be used in the second zone of a fire training rig. The permeable paving system 50 comprises a number of layers of different material which when taken together provide the necessary porosity, storage capacity, strength and insulation from the surrounding ground.

Starting from the bottom, the complete paving system 50 is completely insulated from the surrounding ground by the HDPE liner 52 bedded on the GCL 6mm (51) which acts as a secondary liner and is a layer which is impermeable to liquid. This prevents either ingress or egress of liquid from the paved area to the surrounding ground.

Above the first layer of HDPE 52 is a 300mm thickness of recycled material used as Type 2 bedding stone 53. This provides solid foundations for the materials above. Above this is another layer of 1.9mm thickness FJDPE 54 which also extends to the ground surface. There is then a layer 55 of woven geotextile material. This layer and the other geotextile layer 58 are present to prevent materials from one layer staying into another and thereby compromising the structural stability of the system.

Above the geotextile layer 55 is a 100mm thickness of 6mm single size grit bedding course 56. This provides the support structure for the installation of a first layer of Permavoid (RTM) cells 57. This is a proprietary material which is both strong and hollow, having 90% void. It is therefore capable of holding a considerable quantity of liquid. The Permavoid units are installed row by row and the units are clipped together to further enhance the strength of the layer as a whole. A second layer of Permavoid cells is laid directly on top of the first layer. Each layer is 150mm thick and for an upper surface area of about 5300m² this provides a water holding capacity of approximately 2200m³.

Above the Permavoid a second layer of woven geotextile material 58 is laid above which is a 1300mm thickness of 125-50mm graded stone 59. This is preferably laid in layers of thickness 400mm to 500mm to permit compaction of each layer. In tests it was found that thinner layers would not readily accept compaction. Above this layer a 150mm thickness of 20mm to 10mm Coarse Graded Aggregate to BS 882 (layer 60) was installed.

The paving zone has a top layer of permeable pavers 62 which are kiln baked clay brick pavers of 65mm thickness and include two holes extending through each paver. In this example they are arranged in a herringbone pattern. The pavers allow the infiltration of water both through square holes in the pavers and through the joints between adjacent pavers.

The pavers are laid on a 50mm thickness of screeded and pre-compacted 6mm single size grit laying course material 61 which in turn lies on the layer 60 of Coarse Graded Aggregate. This single size grit laying course material is also swept and vibrated into the joints from the surface. This material in the joints provides an important component in the development of an interlock between the pavers, which provides the surface stability even when subjected to substantial torque from heavy vehicles turning.

The paving system was tested for structural strength after use by heavy vehicles. For example, a fire tender filled with water to ensure that the axle loads were at the maximum value and highway truck loaded to imitate a fire tender were driven over the same path at approximately 15mph (24kph) for 1800 cycles to simulate 25 years operation on a fire training ground. After the trafficking the shape of the surface was measured to check whether the deformation was acceptable. Nomially, a road would be considered to be serviceable is the deformation were less than 40mm. As shown in table 1 and figure 4 the maximum deformation was less than 20mm even with no maintenance of the area, well within the acceptable limits.

The structure has been shown to be structurally sound over an extended lifetime even when subjected to heavy vehicle loading, and is also capable of holding substantial quantities of water. Even after 1800 passes over the same path there was little deformation either vertically or horizontally. Analysis of the cross section of materials after the tests revealed that the materials installed beneath the pavers, in particular pavers 61, 60 and 59 remained as distinct layers which were open graded to allow the passage of water without transporting fine material.

As stated above, the specific sizes and depths of the layers for this example were calculated to meet the requirements of Jersey, but the principles may be applied to other locations with different weather patterns.

Claims

1. A fire training ground comprisin : (i) a first zone comprising a fire training rig, fuel distribution means and waste material collection and disposal means connected to an attenuation tank, and (ii) a second zone comprising an evaporative storage cell, natural water supply means and water distribution means, whereby the first and second zones are connected by valved connecting means.

2. A fire training ground as claimed in claim 1 in which the fire training rig is an old aircraft suitably modified for training purposes or a custom made structure designed to simulate one or more aircraft.

3. A fire training ground as claimed in claim 1 or claim 2 in which the fire training rig is formed of a material which is not substantially damaged by repeated exposure to fire under fire training conditions.

4. A fire training ground as claimed in any preceding claim in which the water distribution means comprise nozzles.

5. A fire training ground as claimed in claim 4 in which the nozzles are directed both onto the fire training rig arid onto the top surface of the ground.

6. A fire training ground as claimed in any preceding claim in which the fuel distribution means comprises pumps and nozzles.

7. A fire training ground as claimed in any preceding claim in which the fuel is a gas or an oil.

8. A fire training ground as claimed in claim 7 in which the fuel is liquefied petroleum gas (LPG) or kerosene.

9. A fire training ground as claimed in any preceding claim in which the waste material collection and disposal means comprises a drain in the central region of the first zone, and inclined top surfaces of the ground of the first zone leading down to the drain.

10. A fire training ground as claimed in any one of claims 1-8, in which the waste material collection and disposal means comprises two or more drains situated around the first zone to collect and transport waste materials from the fire training ground to the attenuation tank.

11. A fire training ground as claimed in claim 9 or claim 10, in which there is additionally an external drainage ditch or moat running round the outer perimeter of the first zone.

12. A fire training ground as claimed in any preceding claim in which the attenuation tank comprises a suitably large volume tank to simultaneously hold the waste material from a number of fire training scenarios.

13. A fire training ground as claimed in claim 12, in which the attenuation tank additionally has an oil-water separator tank directly associated with it.

14. A fire training ground as claimed in claim 13 in which the oil- water separator is a gravity separator.

15. A fire training ground as claimed in any one of claims 12-14, in which the attenuation tank has an additional water supply means.

16. A fire training ground as claimed in any one of claims 12-14, in which the attenuation tank is directly connected to the evaporative storage cell of the second zone.

17. A fire training ground as claimed in any one of claims 12-16 in which the attenuation tank has an outlet directly to a local sewer.

18. A fire training ground as claimed in any preceding claim in which the second zone is located adj acent to the first zone.

19. A fire training ground as claimed in any of claims 1-17 in which the second zone is located at some distance from the first zone and is connected thereto by connecting means.

20. A fire training ground as claimed in claim 18 or claim 19 in which the second zone extends substantially around the outside of the first zone enclosing it completely.

21. A fire training ground as claimed in any preceding claim, in which the top surface of the second zone is permeable to liquids.

22. A fire training ground as claimed in claim 21, in which the top surface is constructed of a single section which includes holes or slots or grooves, or an arrangement of a number of paving slabs or pavers which may optionally have holes through them and/or be arranged such that there are narrow channels on one or more sides of each slab or paver.

23. A fire training ground as claimed in any preceding claim in which the evaporative storage cell of the second zone is located under the top layer of permeable material.

24. A fire training ground as claimed in claim 23, in which the evaporative storage cell extends across substantially the whole of the area covered by the permeable top surface of the second zone.

25. A fire training ground as claimed in any preceding claim, in which there are central control means which coordinate the water and fuel distribution in the first zone, valves in connecting means between the first and second zones, and water distribution means in the second zone.

26. An integrated system for operation of a fire training ground which is largely water neutral, comprising a fire training ground comprising: (i) a first zone comprising a fire training rig, water distribution means, fuel distribution means and waste material collection and disposal means connected to an attenuation tank, and (ii) a second zone comprising an evaporative storage cell, natural water supply means and water distribution means, whereby the first and second zones are connected by valved connecting means, in which natural water is collected in the evaporative cell of the second zone, and the evaporative cell then provides water to the water distribution means for the first zone and any surplus water from the evaporative cell is stored and subsequently disposed of by means of evaporation from the top surface of the second zone.

27. A permeable paving system isolated from the surrounding ground capable of supporting repeated heavy vehicle loading, the paving system comprising, in the following order: (a) a top layer of permeable concrete or clay pavers; (b) a layer of small single size grit laying course material; (c) a thicker layer of Course Graded Aggregate; (d) a substantially thicker layer of larger graded stone; (e) one or more layers of rigid liquid storage cells; (f) a layer of small single size grit bedding course; (g) a film of high density polyethylene (HDPE); (h) a thicker layer of material used as Type 2 bedding stone; and (i) a layer of clay lining (GCL).

28. A permeable paving system as claimed in claim 27 additionally including woven geotextile layers between one or more of the layers.