Containment membrane

Abstract

A liquid resistant containment membrane and which is durable enough to remain in place during the drilling and fracking phases to eliminate the delay and cost of replacement or can be relocated from site to site, has a slip resistant top surface, is a flexible membrane, and/or which top portion of the containment membrane does not absorb liquids. The containment membrane comprises a polymer waterproof layer and a reinforcement layer. The reinforcement layer is connected to a bottom side of the polymer waterproof layer.

Claims

1. A method for protecting an area of ground in a worksite by forming a containment system comprising the steps of: providing a plurality of strips of a liquid-proof containment membrane capable of blocking contaminants from seeping therethrough, each strip of said containment membrane having a top and bottom surface and comprising a polymer waterproof layer forming said top surface of said container membrane and a reinforcement layer that is at least partially embedded in said polymer waterproof layer, said reinforcement layer positioned below said top surface of said containment membrane, said polymer waterproof layer has a thickness that is greater than a thickness of said reinforcement layer, said top surface of said polymer waterproof layer having a textured surface to form a non-smooth surface to form a slip-resistant top surface for improving foot traction when wet; arranging said plurality of strips of containment membrane on the worksite to cover a top surface of the worksite and to cause adjacently positioned strips of said containment membrane to overlap at a side edge of each of said adjacently positioned strips of said containment membrane, said bottom surface of each strip of containment membrane facing said top surface of the worksite; and, forming a liquid-proof or liquid-resistant heat-created melted seam or a liquid-proof or liquid-resistant adhesive bond between said overlapped side edges of said adjacently positioned strips of said containment membrane to form said containment system on said worksite.

2. The method as defined in claim 1, wherein said reinforcement layer is a woven fabric material.

3. The method as defined in claim 2, wherein said polymer waterproof layer has a thickness of about 40 to about 80 mils, said reinforcement layer has a thickness of about 10 to about 15 mils.

4. The method as defined in claim 2, wherein said polymer waterproof layer is greater than 70% of a thickness of said containment membrane.

5. The method as defined in claim 1, wherein said polymer waterproof layer includes polyvinyl chloride, said reinforcement layer comprising a fabric of woven fibers.

6. The method as defined in claim 1, wherein said textured surface has a R.sub.a of at least 20 m.

7. The method as defined in claim 1, wherein said containment membrane is a flexible, waterproof and durable membrane, said containment membrane having a breaking strength of about 55-100 lbs. as tested per ASTM D 751 Procedure B, said containment membrane having an elongation of about 35-70% when tested per ASTM D 751, said containment membrane having a low temperature flexibility of at least 10 F. when tested by ASTM D 2136, said containment membrane resisting tearing at force of at least 20 lbf. as measured per ASTM D 751.

8. The method as defined in claim 1, wherein said step of forming forms said liquid-proof or liquid-resistant heat-created melted seam.

9. The method as defined in claim 1, including the step of adding a curb to at least a portion of a perimeter of said containment system, a top of said curb having a height of at least two inches above a top surface of said containment membrane, said curb creating a liquid-proof or liquid-resistant barrier with said containment membrane.

10. The method as defined in claim 9, wherein said step of adding said curb including the steps of: i. providing a compressible material that is compressible when a compression force is applied to said compressible material and which also retains is original shape after said compression force is removed from said compressible material; ii. positioning said compressible material on a top surface of said containment membrane near a perimeter of said containment system; iii. folding a side portion of said containment membrane over and about said compressible material and overlapping a portion of said side portion with a top surface of said containment membrane; and, iv. securing said overlapping portion of said side portion to said top surface of said containment membrane.

11. The method as defined in claim 10, wherein said compressible material is a high-density foam material.

12. The method as defined in claim 10, wherein said step of securing is by a heat process to form a melted seam.

13. The method as defined in claim 10, wherein said overlapped portion of said side portion overlaps at least two inches of said top surface of said containment membrane.

14. The method as defined in claim 1, wherein said strips of containment membrane are sloped on said site to direct liquids spilled on said top surface of said containment membrane toward internal drains in said containment system.

15. The method as defined in claim 1, wherein said liquid-proof or liquid- resistant seam between said overlapped side edges of said adjacently positioned strips of containment membrane has a seam strength of at least about 50 lbf. before the watertight integrity of said seam is compromised per ASTM D 751.

16. The method as defined in claim 1, wherein said adjacently positioned strips of containment membrane are overlapped by at least two inches.

17. The method as defined in claim 1, wherein said top surface of the polymer waterproof layer includes a textured pattern to form a slip-resistant surface, said textured pattern having a roughness average (R.sub.a) in m is 15-80.

18. A containment system comprising a plurality of strips of a liquid-proof containment membrane that are positioned on a worksite, said containment membrane capable of blocking contaminants from seeping therethrough, said containment membrane having a top and bottom surface and comprising a polymer waterproof layer forming said top surface of said container membrane and a reinforcement layer that is at least partially embedded in said polymer waterproof layer, said reinforcement layer positioned below said top surface of said containment membrane, said polymer waterproof layer has a thickness that is greater than a thickness of said reinforcement layer, said top surface of said polymer waterproof layer is textured to form a non-smooth surface to form a slip-resistant top surface for improving foot traction when wet, said containment system further comprising adjacently positioned strips of said containment membrane having overlapping side edges that are overlapping by at least two inches, said overlapping side edges connected together by a liquid- proof or liquid- resistant seam formed by an adhesive or a melted bond, said liquid- proof or liquid- resistant seam having a seam strength of at least about 50 lbf. before the watertight integrity of said seam is compromised per ASTM D 751, said bottom surface of each strip of containment membrane facing a top surface of the worksite.

19. The containment system as defined in claim 18, wherein said reinforcement layer is a woven fabric material.

20. The containment system as defined in claim 19, wherein said polymer waterproof layer has a thickness of about 40 to about 80 mils, said reinforcement layer has a thickness of about 10 to about 15 mils.

21. The containment system as defined in claim 19, wherein said polymer waterproof layer is greater than 70% of a thickness of said containment membrane.

22. The containment system as defined in claim 18, wherein said polymer waterproof layer includes polyvinyl chloride, said reinforcement layer comprising a fabric of woven fibers.

23. The containment system as defined in claim 18, wherein a top surface of said polymer waterproof layer has a textured surface having a R.sub.a of at least 20 m.

24. The containment system as defined in claim 18, wherein said containment membrane is a flexible, waterproof and durable membrane, said containment membrane having a breaking strength of about 55-100 lbs. as tested per ASTM D 751 Procedure B, said containment membrane having an elongation of about 35-70% when tested per ASTM D 751, said containment membrane having a low temperature flexibility of at least 10 F. when tested by ASTM D 2136-02, said containment membrane resisting tearing at force of at least 20 lbf. as measured per ASTM D 751.

25. The containment system as defined in claim 18, including a curb positioned about at least a portion of a perimeter of said containment system, a top of said curb having a height of at least two inches above a top surface of said containment membrane, said curb creating a liquid-proof or liquid-resistant barrier with said containment membrane.

26. The containment system as defined in claim 25, wherein said curb formed of a compressible material that is compressible when a compression force is applied to said compressible material and which also regains its original shape after said compression force is removed from said compressible material, a majority of said compressible material encircled by said containment membrane, overlapping portions of said containment membrane sealed together to secure said at least partially encircled compressible material in position.

27. The containment system as defined in claim 26, wherein said compressible material is a high-density foam material.

28. The containment system as defined in claim 26, wherein said overlapping portions of said containment membrane that are sealed together are sealed together by a melted seam, said melted seam having a width of at least two inches.

29. The containment system as defined in claim 18, wherein said top surface of the polymer waterproof layer includes a textured pattern to form a slip-resistant surface, said textured pattern having a roughness average (R.sub.a) in m is 15-80.

30. A method for protecting an area of ground in a worksite by forming a containment system comprising the steps of: providing a plurality of strips of a liquid-proof containment membrane capable of blocking contaminants from seeping therethrough, each strip of said containment membrane having a top and bottom surface and consisting of a polymer waterproof layer forming said top surface of said containment membrane and a reinforcement layer that is at least partially embedded in said polymer waterproof layer, said reinforcement layer positioned below said top surface of said containment membrane, said reinforcement layer is a woven fabric material, said polymer waterproof layer has a thickness that is greater than a thickness of said reinforcement layer, said polymer waterproof layer is greater than 70% of a thickness of said containment membrane, said polymer waterproof layer includes polyvinyl chloride, said reinforcement layer comprising a fabric of woven fibers, said top surface of said polymer waterproof layer textured to form a non-smooth surface to form a slip-resistant top surface for improving foot traction when wet, said containment membrane is a flexible, waterproof and durable membrane, said containment membrane having a breaking strength of about 55-100 lbs. as tested per ASTM D 751 Procedure B, said containment membrane having an elongation of about 35-70% when tested per ASTM D 751, said containment membrane having a low temperature flexibility of at least 10 F. when tested by ASTM D 2136, said containment membrane resisting tearing at force of at least 20 lbf. as measured per ASTM D 751; arranging said plurality of strips of containment membrane on the worksite to cover a top surface of the worksite and to cause adjacently positioned strips of said containment membrane to overlap at a side edge of each of said adjacently positioned strips of said containment membrane, said bottom surface of each strip of containment membrane facing said top surface of the worksite; and, forming a liquid-proof or liquid-resistant heat-created melted seam between said overlapped side edges of said adjacently positioned strips of said containment membrane to form said containment system on said worksite.

31. The method as defined in claim 30, including the step of adding a curb to at least a portion of a perimeter of said containment system, a top of said curb having a height of at least two inches above a top surface of said containment membrane, said curb creating a liquid-proof or liquid-resistant barrier with said containment membrane, said step of adding said curb including the steps of: i. providing a compressible material that is compressible when a compression force is applied to said compressible material and which also retains its original shape after said compression force is removed from said compressible material; ii. positioning said compressible material on a top surface of said containment membrane near a perimeter of said containment system; iii. folding a side portion of said containment membrane over and about said compressible material and overlapping a portion of said side portion with a top surface of said containment membrane; and, iv. securing said overlapping portion of said side portion to said top surface of said containment membrane by a heat-created seam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Reference may now be made to the drawings, which illustrate various embodiments that the invention may take in physical form and in certain parts and arrangements of parts wherein:

(2) FIG. 1 is a perspective illustration of a containment membrane according to one non-limiting aspect of the present invention in use at a site such as for example an oil fracking site;

(3) FIG. 2 is a cross-sectional view of the curb detail taken from line 2-2 of FIG. 1;

(4) FIG. 3 is a cross-sectional view of the curb detail demonstrating a vehicle moving over said curb;

(5) FIG. 4 is a top-view perspective illustration demonstrating the textured surface of the top surface of the polymer waterproof layer;

(6) FIG. 5 is a cross-sectional view taken from line 5-5 of FIG. 4;

(7) FIG. 6 is a top plan view of the reinforcement material used in the containment membrane; and,

(8) FIG. 7 is a cross-sectional view taken from line 7-7 of FIG. 1.

DETAILED DESCRIPTION OF NON-LIMITING EMBODIMENTS

(9) An exemplary non-limiting embodiment of the present invention includes a liquid-resistant membrane, suitable for use as a containment membrane in various types of application. One non-limiting application is in the fracking industry and the use of the containment membrane will be described with particular reference for use in fracking applications; however, it will be appreciated that the containment membrane can be used in many other applications where it is desirable to contain liquids, contaminants and the like.

(10) Referring now to FIG. 1, an oil fracking site or other fluid containment area 10 is bound by a containment system that is formed by a plurality of strips of containment membrane 12 that are connected together at a seam 70 (as best illustrated in FIG. 7). As will be described in more detail below, seam 70 is typically a liquid-proof or liquid-resistant seam. The containment membrane is a waterproof membrane that is a configured to form a containment system to prevent a liquid spill (not shown) from seeping into the ground. The containment membrane is also durable to resist tearing and other types of damage when large vehicle and humans move over the surface of the containment membrane. A curb 32 can be formed in the containment system to create an outer raised perimeter in the containment system to facilitate in maintaining spilled liquids in the containment system. The curb can be formed about the complete perimeter of the containment system or on a portion of the containment system.

(11) One non-limiting method for installing the containment system at a particular site is as follows:

(12) 1. Verify that the site wherein the containment system is to be installed is ready to receive the containment system. For example, the site should be cleared of vehicles, equipment, vegetation, etc. that would interfere with the installation of the containment system at the site.

(13) 2. Verify that the containment site is relatively smooth and free of depressions, sharp projections and that the site is sloped properly to allow drainage to the designated drainage areas.

(14) 3. Lay one or more strips of containment membrane on the surface of the site. The containment membrane can be provided in rolls, thereby allowing each strip of containment member to be rolled out on the site. The textured top surface of the containment membrane should be facing upwardly from the ground surface of the site. When two or more strips of containment membrane are laid in the site, the side edges of adjacently positioned strips of containment membrane are overlapped with one another. The amount of overlap is generally 1-10 inches (an all values and ranges therebetween), typically 2-8 inches, and more typically 3-6 inches (e.g., 4 inches). As such, when the seam is formed between the overlapped strips, the width of the seam is generally at least 1 inch and typically 1-10 inches.

(15) 4. Form a liquid-proof or liquid-resistant seam 70 between the overlapped edges of adjacently positioned containment membranes. The liquid-proof or liquid-resistant seam is typically formed by use an adhesive or by forming a melted seam. Prior to forming the seam, it is desirable to remove any moisture that may be present in the area of the seam to be formed. Also, the area to be seamed should be cleaned of dirt, debris or other foreign materials that could adversely affect the formation of the seam. When a melted seam is to be formed, such seam can be formed by a heated iron or by hot air welding. The hot air welder should be operated at the proper air temperature and speed to ensure a continuous waterproof weld along the entire seam between two adjacent containment membrane strips. The hot air welded seam should be free of fish mouths or otherwise areas void. The adjacent containment membrane strips should be overlapped while being hot air welded such that water moves over the lapped joint in a shingle fashion to prevent water being trapped in the seam area. The seam strength is generally at least about 60 lbf. before the watertight integrity of the seam is compromised per ASTM D 751.

(16) A curb can also be installed around the complete perimeter or a portion of the perimeter of the containment system. One non-limiting method for installing the curb is as follows:

(17) 1. Position a berm or curb at or near the perimeter of the containment system.

(18) 2. Secure the berm or curb to the containment membrane. The berm or curb can be secured to the containment membrane by an adhesive, melted seam, or some other means. Alternatively, a portion of the containment member can be folded back over the berm or curb and the edge of the folded back portion can then be secured to the top surface of the containment membrane by use of a connection arrangement 24 form by an adhesive, melted seam, or some other means.

(19) In the event that the containment membrane is torn or otherwise damaged, a patch can be placed over the damaged area. Generally, the patch is formed of the same material as the containment membrane. The area to be patched is generally cleaned so that the patch can be properly secured over the damaged area. The connection between the patch and the damaged containment membrane is generally a liquid-proof or liquid-resistant seam. Such a seam can be formed by an adhesive, a melted sea, or some other means.

(20) Referring now to FIGS. 2 and 4-6, the containment membrane 12 is formed of a first layer 14 and a second layer 16 (see FIGS. 2 and 5). The first layer is a polymer waterproof layer. The second layer is a reinforcement material.

(21) As illustrated in FIG. 4, the top surface of the polymer waterproof layer 14 is textured with a plurality of slip-resistant surface projections, one of which is indicated as 42 for the purpose of improving foot traction when wet. The textured pattern in the top surface of the polymer waterproof layer is non-limiting.

(22) The polymer waterproof layer can be a high-density polyethylene (HDPE) plastic, a low-density polyethylene (LDPE) plastic, a rubber material, polyvinyl chloride (PVC), various types of resins, various types of resin epoxies, polyester, polypropylene, polyurethane, polyacrylate, and copolymers thereof, etc. Additives to enhance the properties of the polymer waterproof layer may also be used (e.g., fire and flame retardants, colorants and pigments, ultraviolet absorbers and stabilizers, biocides, fillers, extenders, anti-oxidants, impact modifiers, etc.). The thickness of the polymer waterproof layer is generally about 30-80 mils. The reinforcement layer is illustrated as a woven fabric material. The reinforcement layer is connected to a bottom side of the polymer waterproof layer. As illustrated in FIG. 5, the top surface of the polymer waterproof layer is absent the reinforcement layer. The texture of the reinforcement layer can generally be felt or visually seen in the bottom of the containment membrane as is illustrated in FIG. 5, but generally cannot be felt on the top of the polymer waterproof layer. The reinforcement layer is generally fully coated with the polymer waterproof layer; however, this is not required. The reinforcement layer is illustrated as being formed by a plurality of woven fibers, non-woven fibers or some mixtures thereof. The reinforcement layer may or may not include any stitching of the fibers. The fibers can include materials such as, but not limited to, glass fibers (e.g., silica glass, aramid glass, etc.), carbon fibers, quartz fibers, Kevlar fibers, boron fibers, polyethylene fibers, polyamide fibers, polypropylene fibers, etc. The thickness of the reinforcement layer is generally less than the thickness of the polymer waterproof layer. The thickness of the reinforcement layer is generally 4-20 mils. The polymer waterproof layer generally constitutes 70-98% of the thickness of the overall containment membrane.

(23) The containment membrane can be formed by a variety of processes (e.g., at least a portion of the reinforcement layer is impregnated with the polymer waterproof layer to form the containment membrane, the polymer waterproof layer is applied to the reinforcement layer by a dipping process and/or a spray coating process, the polymer waterproof layer is heated and the reinforcement layer is pressed into the heated polymer waterproof layer, etc.).

(24) The containment membrane is configured to be a flexible, waterproof and durable membrane. The breaking strength of the containment membrane is typically about 55-100 lbs. as tested per ASTM D 751 Procedure B. The containment membrane typically has an elongation of about 35-70% when tested per ASTM D 751. The containment membrane typically experiences less than about 4% loss of mass due to exposure to common chemicals found in the oil and gas environment when tested per ASTM D 5747. The containment membrane has a low temperature flexibility of at least 10 F. when tested by ASTM D 2136-02 without compromising the containment material. The containment membrane resists tearing at force of at least 20 lbf. as measured per ASTM D 751. The containment membrane provides resistance to abrasion such that the containment membrane does not experience penetration of the waterproofing layer when it experiences at least 400 abrasion cycles per ASTM D 3389Method B.

(25) The containment membrane can be formed or cut to form a predetermined width (e.g., 1-20 ft., 6 ft., etc.) and length (e.g., 1-200 ft, 24 ft., etc.) of containment membrane strips which can be rolled and packaged. Generally, the containment membrane has nearly the same tensile strength in all directions and can therefore withstand large deformation, and possesses excellent puncture resistance, while maintaining an impermeable state.

(26) FIG. 5 is a cross-sectional perspective illustration taken along line 5-5 of FIG. 4 demonstrating the woven pattern of the reinforcement layer 16.

(27) FIG. 6 is a perspective illustration demonstrating the woven pattern of the reinforcement layer 16 according to one non-limiting aspect of the present invention. The woven material pattern comprises a longitudinal thread system 62 and a transverse thread system 64. The transverse thread system is woven together with the longitudinal thread system in an interlaced fashion. Thread system 62, 64 can be stitched together, adhesively bonded together, or include melted bonding prior to the reinforcement layer being connected to the polymer waterproof layer; however, this is not required.

EXAMPLES

(28) The following examples are provided to illustrate in detail the materials, methods and techniques of this invention. These examples are illustrative only, and are not intended to limit the application of the present invention.

(29) The thickness of the containment membrane of Example 1 and Example 2 was tested according to ASTM D 1777, Standard Test Method for Thickness of Textile Materials. Breaking strength of the containment membrane of Example 1 and Example 2 was tested according to ASTM D 751 Procedure B, Standard Test Method for Coated Fabrics. Low temperature flexibility of the containment membrane of Example 1 and Example 2 was tested according to ASTM D 2136-02, Standard Test Method for Coated FabricsLow Temperature Bend Test. Elongation, tearing strength and seam strength of the containment membrane of Example 1 and Example 2 were tested according to ASTM D 751, Standard Test Method for Coated Fabrics. Abrasion resistance of the containment membrane of Example 1 and Example 2 was tested according to ASTM D 3389 Method B, Standard Test Method for Coated Fabrics Abrasion Resistance.

Example 1

(30) In this example, a reinforcement layer was adhered to a flexible polymer waterproof layer. The reinforcement layer was 5 mils (0.005) thick and made of polyester. The polymer waterproof layer was 50 mils (0.050) thick and was made from polyvinyl chloride (PVC). The containment membrane was tested for its physical properties listed in Table 1.

Example 2

(31) In this example, a fleece-backed material layer was adhered to a flexible polymer waterproof layer. The fleece-backed layer was 10 mils (0.010) thick and made of woven fleece. The polymer waterproof layer was 50 mils (0.050) thick and made from polyvinyl chloride (PVC). The containment membrane was tested for its physical properties listed in Table 1.

(32) TABLE-US-00001 TABLE 1 Property Test Procedure Example 1 Example 2 Thickness (mils) ASTM D 1777 55 60 Breaking Strength (lbs.) ASTM D 751 130 65 Procedure B Elongation (%) ASTM D 751 50 50 Low Temperature ASTM D 2136-02 30 30 Flexibility ( F.) Tearing Strength (lbf) ASTM D 751 40 25 Seam Strength (lbf) ASTM D 751 250 250 Abrasion Resistance ASTM D 3389 - 1000 1000 (number of cycles) Method B

(33) The examples described herein are not intended to limit the scope of the invention generally disclosed.

(34) Referring now to FIGS. 1-3, a curb 32 can be formed in the containment system. As illustrated in FIG. 2, the containment membrane can be wrapped over a berm or curb 18 so as to provide a dimensional height so that spills and rainwater are retained within the containment perimeter of the containment system. The site upon which the containment membrane lies can be sloped to internal drains which are used to capture the rainwater, any petroleum spills, contaminants, etc. that spill onto the containment membrane. Any fluid can be analyzed prior to pumping out the drains for disposition.

(35) The walls created by the containment membrane and foam berm material can comprise generally vertically-oriented walls which merge continuously with the containment membrane thereby creating a leak-proof containment membrane perimeter.

(36) FIG. 2 is a cross-sectional perspective illustration of a containment membrane curb installation. Generally, containment membrane 12 is laid upon a ground material 20 such that the reinforcement material 16 on the bottom side of the containment membrane is in direct contact with the ground material 20. As such, the polymer waterproof layer on the top side of the containment membrane faces upwardly. A foam berm material 18 is placed upon the top surface of the polymer waterproof layer 14 of containment membrane 12 such that the bottom surface 18a of foam berm material 18 engages directly with the polymer waterproof layer 14. Containment membrane 12 is enveloped (e.g., wrapped) around the foam berm material 18 such that the polymer waterproof layer engages with foam berm edges 18b and 18c and such that the inverted portion 22 containment membrane 12 extends at least partially over the base containment membrane. As such, the reinforcement material layer 16 is exposed outwardly from the foam berm material 18 on sides 18b and 18c and along the upwardly-facing surface of the inverted portion 22 of containment membrane 12. A connection arrangement 24 such as melted seam is used to connect the polymer waterproof layers of containment membrane 12. The width of the overlapping inverted portion 22 is generally about 2-8 inches (e.g., 4 inches). As such, when the seam is formed between the overlapping inverted portion and the top surface of the containment membrane, the width of the seam is generally at least 1 inch and typically 2-8 inches.

(37) FIG. 3 is a perspective illustration demonstrating a vehicle moving over a containment membrane curb. The vehicle (not shown) is traveling in the direction indicated by arrow A such that its wheels are spinning counter-clockwise, the direction indicated by arrow B. As such, when a tire 30 approaches and engages with containment curb 32, oblique forces are generated on containment curb 32 as indicated by arrow C. Foam berm material 18 can retain its original configuration once the vehicle passes over and the forces are released off of containment curb 32.

(38) According to one non-limiting aspect of the present invention, the foam berm material allows for different applied forces. The foam material may compress, but is resilient and returns to its original shape when no force is applied. The foam material can be a high-density foam that has the ability to return its form and shape when compressed by heavy loading.

(39) The containment membrane can be durable and flexible such that when heavy equipment drives over the containment membrane, as well as the berms or curbs (which can also be wrapped by the containment membrane) the containment membrane and berms or curbs retain their original structure.

(40) With reference to FIG. 7, an overlapping containment membrane strip 72 can be joined with an underlapping containment membrane strip 74 at seam 76. Seaming techniques can include use of an adhesive, heat welding and other techniques. The width of the seam is at least about 1 inch, typically at least about 2 inches, and more typically about 2-6 inches (e.g., 4 inches). During seaming, the containment membrane strips are placed reinforcement layer down. The polymer waterproof layer of the overlapping layer can be heat welded directly to the polymer waterproof layer of the underlapping layer.

(41) With continued reference to FIG. 7, underlapping containment membrane layer 74 is joined continuously with overlapping containment membrane layer 72 at seam 76. As such, no cavity or space is formed between the pair of underlapping and overlapping strips.

(42) It will this be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention has been described with reference to preferred and alternate embodiments. Modifications and alterations will become apparent to those skilled in the art upon reading and understanding the detailed discussion of the invention provided herein. This invention is intended to include all such modifications and alterations insofar as the come within the scope of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the intention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.