WO2005102462A1

WO2005102462A1 - Contaminated structure coating process

Info

Publication number: WO2005102462A1
Application number: PCT/AU2005/000569
Authority: WO
Inventors: David Guthrie
Original assignee: Poly Tech 5000 Pty Ltd
Priority date: 2004-04-23
Filing date: 2005-04-26
Publication date: 2005-11-03

Abstract

The present invention resides in a method providing a protective surface coating to a contaminated surface of a structure (20). The method comprises the steps of removing relatively loosely attached portions (21) from the contaminated surface (22). Applying a first layer of elastomeric material (26) to the contaminated surface (22) so as to contain the contaminated surface (22) on the structure (20); and coating the first layer. of elastameric material with a protective surface coating (28).

Description

"Contaminated structure coating process"

Field of the Invention

The present invention relates generally to a method of externally coating and protecting a contaminated surface of a structure so as to isolate and contain the contaminated surface. In particular, the present invention relates to a method of providing a protective exterior coating to a metal structure, such as a bridge or the like, to prevent exposure to lead based paint present thereon.

Background of the Invention

Prior to the 1970's, lead based pigments were commonly used in the formulation of paints due to the beneficial properties of lead. White lead (basic lead carbonate) was found to have particularly good external weathering characteristics when combined into a paint solution, whilst paint combined with red lead pigment was found to exhibit particularly good rust inhibiting-characteristics. In this regard, most external steel or iron structures, such as bridges, water towers and building structures, had a lead based paint applied to its surface to ensure corrosion protection and longevity of the structure.

Over time, the public has become increasingly aware of the harmful affects of exposure to lead, and particularly paint containing lead based pigments. It has been found that the lead contained in paint is not only dangerous when the paint itself peels from the surface of the structure, but the lead is known to leach or separate from the surface of the paint in the form of dust which can contaminate the surface of the structure and the surrounding environment. Should an individual inhale the dust or otherwise ingest the lead through contact with the dust or loose scraps of paint, the lead can enter the individual's blood stream and be stored within the body for slow release over time. There are both acute and chronic effects of lead exposure, depending upon the intensity and duration of the exposure, which can lead to a variety of conditions including coma, respiratory arrest, and in some cases death.

In this regard, most national governments have recognised the hazards associated with human and animal contact with lead based paint and have issued various regulations and guidelines to prevent further use of lead based paints and products and to control the manner in which existing lead contaminated material is handled. This is particularly an issue in external structures such as bridges and the like where a large percentage of the structures still contain lead based paint coatings, but also require significant corrosion protection to ensure that they perform their essential function. Further, such structures require regular servicing and maintenance to ensure their longevity, and hence continual contact with the contaminated surfaces by the maintenance workers needs to be safely controlled.

In this regard, one way in which to deal with the contaminated surfaces of such structures has been to remove the lead based paint from the surface of the structure. The most common method of doing this has been open (nozzle) abrasion, whereby an abrasive material, generally steel shot/grit, sand or slag, is forced by compressed air through hoses onto the surface of the structure thereby removing the layer(s) of paint. Other methods of paint removal such as vacuum blast cleaning, wet abrasive blast cleaning, and chemical cleaning are also used. In order to contain and control the airborne concentration of the abrasive dust and the lead particles, containment structures are erected, in the form of tarpaulins and the like, which fully enclose the structure being treated. Typically, the containment structures employ large air movement structures which create a negative pressure inside the containment to remove the lead dust from the worksite. In this regard, the workers operating the machinery must be provided with full protective equipment, including respirators so that they are not exposed to any contact with the lead dust.

In such arrangements, extensive pre and post testing of the workers and the work area must be performed to ensure that contamination of the workers and the environment does not occur. As can be appreciated, in order to satisfy the necessary health and safety standards, the costs associated with performing such a treatment are exorbitant and require the presence of a number of health and safety professionals to oversee the process. As such, the duration and costs of performing simple routine maintenance on such structures becomes a significant drain on the resources of the responsible body, resources which are becoming increasingly under pressure, particularly as structures age and governments review their budgets.

More recently, methods have been proposed which are directed towards applying an encapsulating layer of material over a surface of a lead contaminated item in an attempt to encapsulate the lead beneath the coating. Such methods, such as that described in U.S. Patent No. 6,666,938, employ a foil-type layer that is placed over the contaminated surface of the structure to bond thereto. The foil layer prevents lead from leaching from the contaminated surface of the structure and prevents flakes of the paint from peeling off the structure and releasing into the environment. However, such a method is not readily adapted for use on an external structure such as a bridge or the like and requires significant time and expertise in applying the foil layer. Further, such a system does not provide a surface that can be continually painted or treated which ensures the integrity of the original layer of encapsulating material.

There is therefore a need to provide a system for treating a contaminated surface of a structure such as a bridge or the like which prevents contact with contaminated pre-existing surfaces and which is stable and provides a re-treatable surface for continual painting/maintenance.

Summary of the Invention

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.

According to a first aspect, the present invention is a method of providing a protective surface coating to a contaminated surface of a structure, comprising: removing at least some of the relatively loosely attached portions of the surface from the contaminated surface; applying a first layer of elastomeric material to the contaminated surface so as to contain the contaminated surface on the structure; and coating the first layer of elastomeric material with a relatively protective surface coating. In one embodiment, the step of removing relatively loosely attached portions from the contaminated surface comprises scraping the contaminated surface to dislodge some or all of the relatively loosely attached portions therefrom. Following removal of the relatively loosely attached portions, the dislodged portions may be collected for disposal to prevent human contact with the dislodged portions and to prevent environmental contamination. In one form of the invention, the collection of the dislodged portions of the contaminated surface may occur simultaneously with their removal. In this regard, a region of relatively lower pressure may be provided to ensure appropriate collection of the dislodged portions. In another form, a vacuum suction scraper may be employed to perform the dislodgement and collection of the relatively loosely attached portions.

In yet another embodiment, in some environments, such as seaside environments where the structure is exposed to salt spray and other environmental deposits, it may be necessary to clean such deposits from the surface following removal of the relatively loose portions. In this regard, the surface can be washed with freshwater applied with absorbent sponges and the like, to remove the undesired deposits from the surface.

In another embodiment, prior to the step of applying the first layer of elastomeric material, at least some or all of the contaminated surface may be wiped to reduce, or more preferably remove, moisture from the contaminated surface and enhance the subsequent adhesiveness of the contaminated surface with the first layer. In this regard, the contaminated surface may be wiped with a solvent solution. The solvent solution may be a polyurethane thinner or an acetone. In another form, solvent solution may be applied to the contaminated surface by a gun wash. In either form, the wiping of the contaminated surface may remove calcification and other imperfections from the contaminated surface without requiring removal of any of the contaminated surface.

The contaminated surface may be a surface of a structure comprising a paint containing lead-based pigments. In this regard, the structure may be a bridge, such as a railway or vehicle bridge. Alternatively, the contaminated surface may be a surface of a structure containing asbestos, or an arsenic treated timber. In this regard, the structure may be a building or any other similar construction. The elastomeric material may be a polyether based urethane elastomer. In this regard, the elastomeric material may be a two part urethane elastomer wherein one part of the elastomeric material comprises a glycol blend and the other part of the elastomeric material comprises an isocyanate. The isocyanate may comprise diphenylmethane 4.4 diisocyanate and reaction products with hydroxylated compounds. In one form, the glycol blend and the isocyanate can be mixed together to a proportion of 100:114 m/m to form the elastomeric material. In one embodiment, the step of applying the first layer of elastomeric material to the contaminated surface may comprise spraying the elastomeric material on the contaminated surface. The elastomeric material may be sprayed at a relatively low pressure, for example, a pressure of between about 10 to 40 psi. In another embodiment, the step of applying the first layer of elastomeric material to the contaminated surface may comprise painting the material onto the surface by a brush, a roller or other suitable applicator. The first layer of elastomeric material may be applied to the contaminated surface so as to form a dry film thickness of elastomeric material of between 1500 to 5000 microns. In this regard, the first layer of elastomeric material fully encapsulates the contaminated surface beneath the elastomeric material. In another embodiment, the step of coating the first layer of elastomeric material with a protective surface coating may comprise spraying the protective coating on the elastomeric material. In another embodiment, the protective surface coating may be applied to the elastomeric material by painting the coating on the elastomeric material using a brush or roller. The protective surface coating may be applied to achieve a dry film thickness of between 75 to 100 microns. In this regard, the protective surface coating can be at least substantially UN impermeable thereby forming a barrier against destructive UN rays which may damage the layer of elastomeric material due to gradual breakdown of the layer, thereby exposing the contaminated material. The protective surface coating also provides decorative colour finishing of the structure 20. Examples of suitable protective coatings include paints, such as commercially available paints such as Dulux Weathershield (TM) or an equivalent solar reflective paint.

The present invention provides a method of protecting and encapsulating an existing surface of contaminated material without the need to further disturb the contaminated material, other than to remove relatively loose or flaking portions from the surface thereof.

According to a second aspect, the present invention is a structure having a protective surface coating as applied using the method of the first aspect of the invention. According to a third aspect, the present invention is a protective surface coating for a structure applied using the method of the first aspect of the invention.

According to a fourth aspect, the present invention is a method of encapsulating a contaminant on a surface of a structure, comprising: mixing together a two part elastomeric material; and applying said elastomeric material to said surface of said structure to encapsulate said contaminant thereon. In one embodiment of this aspect, the two part elastomeric material is a 100% solids, polyether based urethane elastomer. The elastomeric material may have a first part consisting of a glycol blend and a second part consisting of an isocyanate. In this regard, the first and second parts may be mixed together to a proportion of 100:114 m/m. In one embodiment, the mixing may occur at a nozzle of a spray gun, and the elastomeric material may be applied to the structure surface immediately following mixture.

Brief Description of the Drawings By way of example only, preferred embodiments of the invention are now described with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram showing some of the steps of the method of providing a protective coating to a contaminated surface of a structure, according to one embodiment of the present invention;

Fig. 2A is a partial cross-sectional view of a contaminated surface of a structure;

Fig. 2B is a partial cross-sectional view of a step of removing loose or relatively loose portions of a contaminated surface of a structure in accordance with an embodiment of the present invention;

Fig. 2C is a partial cross-sectional view of a contaminated surface of a structure encapsulated by an encapsulating coating in accordance with an embodiment of the present invention; and Fig. 2D is a partial cross-sectional view of a protective surface applied to an encapsulating coating which encapsulates a contaminated surface of a structure in accordance with an embodiment of the present invention.

Preferred Mode of Carrying out the Invention

The present invention is directed towards retaining the beneficial properties of the original lead-based paint of a structure, namely the improved weather resistance and rust proofing characteristics, by sealing the existing surface within an encapsulation layer such that repainting of the structure is possible by applying a fresh coating of paint to the outer surface of the encapsulating layer. Such an arrangement enables continuing routine maintenance of the structure without exposure to the contaminants contained therein and preserves the longevity of the structure. Whilst the present invention will be described in relation to its application to a bridge structure, it will be appreciated by those skilled in the art that the invention could be readily applied to a variety of different steel or iron structures or fabrications, each having a contaminated surface coating. With reference to Fig. 1 and Figs. 2A - 2D, some of the steps of the method according to one embodiment of the present invention are shown.

In Fig. 2A, there is shown a portion of a steel or iron structure 20, such as a portion of a bridge, having an external coating of lead-based paint 22. Whilst lead- based paint has been shown to exhibit good weather resistant properties and rust proofing characteristics, over time the surface of the coating 22 can deteriorate, exposing loose or relatively loose portions 21 which can readily separate from the surface of the existing coating. Such portions 21 have been shown to pose a risk to individuals if ingested or inhaled and can cause pollution to the surrounding environment by releasing into the soil and waterways.

In step 12 of Fig. 1 and as shown in Fig. 2B, in order to prevent such loose or relatively loose portions 21 from separating from the surface 22 of the structure 20, and to prepare the surface 22 such that it can be isolated from further wear and human contact, at least some and preferably all of the loose or relatively loose portions are removed are removed from the surface 22. The step of removing the loose or relatively loose portions 21 of the existing contaminated surface 22 is a relatively gentle process which is not directed at attacking or physically removing the existing contaminated surface 22. In this regard, a device such as a vacuum suction scraper 24 is passed over the surface of the structure, scraping away the loose or relatively loose portions 21 and collecting them in a collection bag through the action of the vacuum. Upon collection of the loose portions 21 of contaminated material they can be disposed of in accordance to the various EPA and regulatory requirements. Such a device is well known in the art and is capable of operating at a rate of 300 m³/min and collecting particles up to around six inches in diameter. It will also be appreciated that other types of devices could also be used in this step, such as hand scrapers, wire brushes and the like, in combination with a vacuum system which collects the removed pieces of surface coatings. It will be appreciated that in this step, there is no need for traditional surface preparation and paint removing procedures such as abrasive blasting and/or high pressure water blasting which are directed at removing the existing contaminated surface layer 22. Only those portions of the surface 22 which are loose or relatively loose are removed and the structure of the existing surface 22 remains generally intact. Hence, relatively little or no dust or fine water-borne particles of lead are created and as such there is no need to fully enclose the bridge structure and stringently monitor the surrounds as is typical when such high pressure blasting systems are employed to prepare bridges and the like for painting. The step 12, merely removes the flaking particles leaving behind a relatively smooth surface 22, free from flaking material, upon which to apply further treatment.

An alternative method of preparing the surface to remove the loose or relatively loose surface portions 21 from the contaminated surface 22, is to apply an initial sacrificial coating of an elastomeric material to the surface 22. The elastomeric material may be the elastomeric material described below in relation to step 16, or may be an elastomeric material having lesser adhesion properties. In this regard, the sacrificial coating is applied and allowed to cure on the contaminated surface 22, after which it is torn away from the surface 22. In the act of tearing away the coating from the surface, any loose or relatively loose portions 21 are adhered to the sacrificial coating and removed, leaving behind a surface 22 devoid of such loose portions 21. Such a method ensures that no airborne particles are released from the surface 22 and provides one-step removal and collection of the contaminated portions 21.

In some environments, such as seaside environments where the structure 20 is exposed to salt spray and other environmental deposits, it may be necessary to clean such deposits from the surface following removal of the relatively loose portions 21. In this regard, the surface can be washed with freshwater applied with absorbent sponges and the like, to remove the undesired deposits from the surface 22. In step 14, the prepared surface 22 is then wiped with an appropriate solvent to at least substantially, and preferably wholly, remove moisture from the surface and to reactivate the adhesiveness of the external surface 22. It is common for bridge surfaces having a lead based paint coating to have a degree of calcification upon the surface 22, which represents a "chalk-like" coating, and in step 14, this coating is removed.

The solvent used to wipe the surface 22 of the structure is dependant upon the type of paint system previously used to coat the surface. Typically, a polyurethane thinner or acetone is applied upon the surface of the structure, however other solvents may also be used as appropriate. For example, in instances where an acrylic paint has been previously applied to the surface 22, the solvent may be applied to the surface by a "gun wash".

Whilst step 14 is provided to clean and remove moisture from the surface 22 of the structure, during this process the adhesiveness of the surface 22 is also improved or reactivated to receive further coatings, as will be discussed below. It will also be appreciated that in this step, there is no intensive labour and minimal safety practices are required as the surface is merely wiped and no dust or waste water is produced which could be ingested or inhaled by the workers or leach into the environment. It will also be appreciated that steps 12 and 14 form preparation steps and could be performed at or around the same time.

In step 16, the prepared surface 22 of the structure is completely covered with an encapsulating coating 26, which seals the surface 22 and the associated contaminants.

The encapsulating coating 26 is a 100% solids, two component, polyether based urethane elastomer system which, when applied over the existing surface 22, fully encapsulates the hazardous material, preventing any further loss or environmental degradation of the surface 22. In this regard, the pre-existing surface 22 is still present on the surface of the raw steel or iron structure 20, thereby providing the benefits of improved corrosion and weathering resistance inherent with traditional lead-based paints, whilst an additional protective jacket 26 is provided over the structure which protects the structure 20 against the elements, ensuring that the life of the bridge, and the resulting transport infrastructure is maximised.

The encapsulating coating 26 provides excellent adhesion, durability and water impermeability under a range of extreme climatic conditions, and embodies itself in the exact same shape as the shape of surface 22.. The coating 26 exhibits high tensile strength and flexibility which is important for use on structures such as bridges and other external structures, as the structure can experience movement due to thermal expansion and the like and the coating can move with the structure to provide complete protection and isolation of the underlying surface layers. In this regard, the elongation/flexibility properties of the coating 26 can be readily adjusted to match the environmental conditions of the structure to which it is to be applied. For example, for bridges located in regions that experience both temperature extremes, namely very low temperatures in winter and very high temperatures in summer, the coating 26 may be blended to enable a larger degree of elongation/flexibility than may be required in regions that experience mild and consistent yearly temperatures.

It will be appreciated that the coating 26 is a 100% solids coating applied directly to the surface of the structure and has sufficient adhesion and structural stability to bind together without the need for intermediate mesh or foil binding layers or glass or sand particles interspersed therein. Such additives can greatly reduce the thermal expandability and elongation/flexibility of the coating 26, making the application of the coating layer more difficult, and ultimately less likely to cope with variations in temperature cycles. The coating 26 is also resistant to corrosion causing chemicals, oils, fuels and solvents, flame mould mildew and fungus, which make it particularly applicable to its use on bridges and other external structures. The coating 26, when applied, also has good thermal stability and remains elastomeric at temperatures between around -20° C and 80° C, and is resilient to abrasion, cutting and gouging. An example of the general mechanical and physical properties associated with a particular blend of the coating 26 are summarised in the table below.

As mentioned previously, the encapsulating coating 26 is in the form of a two part urethane elastomer. Part A of the urethane elastomer coating is a glycol blend which is mixed with Part B to a proportion of, for example, 100:114 m/m. Other proportions are also possible depending upon the optimal properties required. Part B of the urethane elastomer coating is an isocyanate comprised of Diphenylmethane 4.4 diisocyanate and reaction products with hydroxylated compounds. Following mixture of the parts, the coating 26 forms a solution that can be readily applied to the surface 22 of the structure to form a tough, homogeneous, and seamless coating having a fast gel time.

In this regard, parts A and B of the encapsulating coating 26 are only mixed immediately prior to application to the surface 22. This is achieved by separately supplying parts A and B to a spray application gun such that the two parts only become mixed at the nozzle at which point they are directly applied to the surface 22. Following mixture and application of the two parts, the mixture has a gel time of around 30 seconds. Such a fast gel time without the need to apply further adhesives or catalysts or heating to initiate curing, provides a surface which can be further processed almost immediately. Due to the properties of the coating 26, the spray can be applied by a low-pressure pump, at a 1:1 ratio to volume, at about 20 psi. This contrasts significantly to the pressures at which normal spray paints and the like are applied, typically between 2000 - 6000 psi thereby significantly reducing atomisation and facilitating a consistent spreading rate and coating thickness to achieve a minimum dry film thickness (DFT) of at least 1500 microns. Ideally, the desired DFT is between 1500 microns and 5000 microns, depending on the environmental conditions of the structure and as the wet film thickness (WFT) and the DFT are substantially the same, by controlling the thickness of the applied coating, the thickness of the final, dry coating 26 is also ensured.

As discussed, the coating 26 can be applied to the bridge structure 20 in step 16 by spraying, and also by brushing, painting, or rolling. In this regard, the regions of a bridge structure 20 which are easily accessible are sprayed with the encapsulating coating 26, whilst the difficult to access areas are brush or roller coated. Typically, only a single coating is required, however it may be necessary in some cases to stripe coat regions of the structure with a brush or roller and follow-up with a spray coating of the region.

To ensure optimum coating of the existing surface 22 of the structure 20, at the time of application of the coating 26, the ambient temperature of the surface 22 of the structure should be no less than about 5°C and no greater than about 60°C. The relative humidity in the vicinity of the structure 20 should also not exceed about 85%.

Following the application of the encapsulating coating 26 to the surface 22 of the structure at step 16, a finishing coating 28 is then applied to the surface of the encapsulating coating 26 at step 18. The finishing coat 28 can be applied almost immediately following the application of the encapsulating coating 26, due to the relatively fast curing time of the encapsulating coating 26.

The finishing coating 28 generally performs a duel function. Firstly, it provides a desired colour finish to the structure 20 thereby fulfilling an aesthetic function. Secondly, it acts as a barrier to provide suitable protection from the weather and from harmful UN rays which, over time, may act to break down the encapsulating coating 26, as the encapsulating coating 26 is intended to last the lifetime of the structure 20 to provide permanent encapsulation of the lead based paint. In this regard, the finishing coating 28 may be in the form of a water-based single-pack acrylic, UN stable, industrial grade finish paint that is spray applied over the surface of the protective coating, by conventional methods, to a DFT of between 75 - 100 microns. The finishing coating 28 could be a commercially available paint such as Dulux Weathershield (TM) or an equivalent solar reflective paint. Due to the particularly good adhesion and wrapping characteristics of the encapsulating coating 26, the finishing coating 28 can be readily applied, to form a strong bond therewith. In this regard, as the finishing coating 28 deteriorates over time, for instance following the expiration of the warranty of the finishing coating 28, the outer surface of the structure 20 can be merely washed down and repainted. As the lead-based paint is encapsulated within the coating 26 there is no longer a need to directly handle the lead based paint surface and thereby a stable, uncontaminated external surface of the structure is provided for future maintenance programs. With regard to ongoing maintenance of a bridge structure being treated with the method of the present invention in comparison to a bridge structure being treated by a conventional method, it has been estimated that over a 60 year period, the present invention provides significant cost and time savings. In this regard, the conventional method has been taken to comprise a method requiring a full enclosure of the bridge with removal and replacement of the existing surface coatings, and the estimation has been made based on a 10,000 m steel bridge having a heavily pitted condition with a rusted existing lead based paint coating.

It has been estimated that using the conventional method, following the initial treatment, a maintenance treatment is generally conducted every 10 years. The maintenance treatment generally requires full or spot blasting of the bridge to remove the existing paint layer, together with site enclosure and dust extraction, as well as re- applying a primer and top-coat of paint. Therefore, over a 60 year period this results in 7 treatments at a considerable cost.

In comparison, by employing the method of the present invention, following the initial treatment there is only required a maintenance treatment every 15 years, typically at the expiration of the warranty of the finishing coating. All that is required in the following maintenance treatments is a washing of the external surface of the bridge structure and the application of a new finishing coating. Therefore over a 60 year period, a total of 5 treatments are required resulting in costs of around 20% of those estimated using the conventional method. Therefore the present invention provides significant savings in both time and associated costs. Whilst the above embodiment has been described in relation to the encapsulation of lead-based paints, it will be appreciated that the invention could be readily adapted to provide encapsulation of other contaminated surfaces. For example, asbestos sheets used in construction and the like, and timber products treated with copper chrome arsenate (CCA) could equally be treated by the above described method.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive .

Claims

CLAIMS:

1. A method of providing a protective surface coating to a contaminated surface of a structure, comprising: removing at least some of the relatively loosely attached portions from said contaminated surface; applying a first layer of elastomeric material to said contaminated surface so as to contain the contaminated surface on the structure; and coating said first layer of elastomeric material with a relatively protective surface coating.

2. A method according to claim 1, wherein the step of removing relatively loosely attached portions from the contaminated surface comprises scraping said contaminated surface to dislodge only the relatively loosely attached portions therefrom.

3. A method according to claim 2, wherein following removal, the dislodged portions are collected for disposal.

4. A method according to claim 3, wherein as the dislodged portions of the contaminated surface are removed, they are collected for disposal.

5. A method according to claim 4, wherein said dislodged portions of the contaminated surface are collected by a vacuum.

6. A method according to claim 3, wherein a vacuum suction scraper is used to dislodge the relatively loosely attached portions from the contaminated surface and to collect the dislodged portions.

7. A method according to claim 1, wherein prior to the step of applying the first layer of elastomeric material, the contaminated surface is wiped to remove moisture therefrom and enhance the adhesiveness of the contaminated surface.

8. A method according to claim 7, wherein the contaminated surface is wiped with a solvent solution.

9. A method according to claim 8, wherein the solvent solution is a polyurethane thinner.

10. A method according to claim 8, wherein the solvent solution is acetone.

11. A method according to claim 7, wherein the contaminated surface is wiped with a gum wash.

12. A method according to any one of the preceding claims, wherein the contaminated surface is a surface comprising a paint containing lead-based pigments.

13. A method according to any one of the preceding claims, wherein the contaminated surface is a surface containing asbestos.

14. A method according to claim 1, wherein the elastomeric material is a polyether based urethane elastomer.

15. A method according to claim 14, wherein the elastomeric material is a two part urethane elastomer.

16. A method according to claim 15, wherein one part of the elastomeric material comprises a glycol blend.

17. A method according to claim 15 or 16, wherein one part of the elastomeric material comprises an isocyanate.

18. A method according to claim 17, wherein the isocyanate comprises diphenylmethane 4.4 diisocyanate and reaction products with hydroxylated compounds.

19. A method according to claim 18, wherein the glycol blend and the isocyanate are mixed together to a proportion of 100:114 m/m to form the elastomeric material.

20. A method according to claim 1, wherein the step of applying the first layer of elastomeric material to the contaminated surface comprises spraying the elastomeric material on the contaminated surface.

21. A method according to claim 20, wherein said elastomeric material is sprayed onto said contaminated surface at a pressure of between about 50 to 120 psi.

22. A method according to any one of claim 1, wherein the step of applying the first layer of elastomeric material to the contaminated surface comprises brushing the elastomeric material onto the contaminated surface.

23. A method according to claim 1, wherein the step of applying the first layer of elastomeric material to the contaminated surface comprises rolling the elastomeric material onto the contaminated surface.

24. A method according to any one of claims 20 to 23, wherein the first layer of elastomeric material is applied to the contaminated surface to form a dry film thickness of elastomeric material of between 1500 to 5000 microns.

25. A method according to claim 1, wherein the step of applying the first layer of elastomeric material to the contaminated surface comprises fully encapsulating the contaminated surface beneath the elastomeric material.

26. A method according to claim 1, wherein the step of coating the first layer of elastomeric material with a protective surface coating comprises spraying the protective coating on the elastomeric material.

27. A method according to claim 1, wherein the step of coating the first layer of elastomeric material with a protective surface coating comprises painting the protective coating on the elastomeric material by a brush.

28. A method according to claim 1, wherein the step of coating the first layer of elastomeric material with a protective surface coating comprises painting the protective coating on the elastomeric material with a roller.

29. A method according to any one of claims 26 to 28, wherein the protective surface coating is applied to a dry film thickness of between 75 to 100 microns.

30. A method according to claim 29, wherein the protective surface coating is substantially UN impermeable.

31. A structure having a protective surface coating as applied using the method of any one of claims 1 to 30.

32. A protective surface coating for a structure applied using the method of any one of claims 1 to 30.

33. A method of encapsulating a contaminant on a surface of a structure, comprising: mixing together a two part elastomeric material; and applying said elastomeric material to said structure surface to encapsulate said contaminated material.

34. A method according to claim 33, wherein said two part elastomeric material is a 100%o solids, polyether based urethane elastomer.

35. A method according to claim 34, wherein said elastomeric material has a first part consisting of a glycol blend and a second part consisting of an isocyanate.

36. A method according to claim 35, wherein the first and second parts are mixed together to a proportion of 100: 114 m m.

37. A method according to claim 35, wherein said mixing occurs at a nozzle of a spray gun, and said elastomeric material is applied to the structure surface immediately following mixture.