AU2006202697A1 - Water capture with synthetic turf - Google Patents

Description

3818-1.doc -1- Water capture with synthetic turf Field of Invention This invention relates to rain water collection and more specifically to collection of rainwater falling on synthetic turf, outdoor carpet and other grass replacements, herein after referred to as synthetic turf.

Background In many regions and areas where the look or functionality of a lawn or grass is desired many people lay a synthetic turf, which does not require regular watering.

This is driven partly by the lack of maintenance required but also by factors such as restrictions on use of mains or potable water on gardens and lawns, the lack of sufficient rainfall or irregularity of rainfall. Synthetic grass replacements are also used for some sporting surfaces.

In areas and regions where there exist restrictions on use of mains or potable water on gardens and lawns, the lack of sufficient rainfall, or irregularity of rainfall or any combination of these, many people install rainwater tanks to collect rainwater for subsequent use on their gardens or for domestic use.

Current rainwater collection systems utilise the roof of one or more buildings to collect rain water, which is then passed or diverted to one or more rainwater tanks.

Summary of the Invention In one broad form the invention provides a synthetic lawn, sporting surface or other synthetic grass replacement with water collection means for collecting water that seeps or otherwise passes through the synthetic lawn or runs off the synthetic lawn or both.

3818-1.doc -2- In one form a void forming structure is located beneath the synthetic turf or forms part of the synthetic turf to capture water seeping or otherwise passing through the synthetic turf. Preferably a substantially water impervious barrier is located beneath the void to prevent or substantially lessen seepage of water into the soil.

The impervious barrier and the void forming structure are preferably integrally formed and more preferably formed of a plastics sheet or layer having protrusions, ribs or other structures to space the synthetic turf above the base of the sheet.

Water collected is preferably stored in one or more tanks for later use. The tanks may be located partially or fully under the synthetic lawn or may be located remotely from the synthetic lawn.

In another form the water collection means includes tanks or receptacles located beneath the turf and the tanks are provided with apertures or voids in the top side of the tank, such that water seeping or otherwise passing through the turf passes into the tanks.

The tanks may be provided with a separate top and so the base and side may be formed of concrete and a plastics or metal grid may form the top of the tank.

In preferred embodiments where the tanks are located underground open celled stormwater retention modules surrounded by a water impervious layer are preferred for the tanks. Preferably the water impervious layer is a plastics sheet or film.

The water collection means may include at least one gutter extending along at least part of the periphery of the synthetic lawn. The at least one gutter may be configured to collect surface run off and direct it to one or more collection points.

3818-1.doc -3- When the synthetic lawn is assembled with a water collection void beneath the synthetic turf, the void may drain into one or more gutters located at the periphery of the synthetic lawn.

Brief Description of the Drawings Figure 1 shows a cross sectional side view of a synthetic lawn according to a first embodiment of the invention.

Figure 2 shows a detail of the synthetic lawn structure of figure 1.

Figure 3 shows a plan view of part of a spacer layer used in the figure 1 embodiment.

Figure 4 shows a schematic plan view of a synthetic lawn according to the first embodiment.

Figure 5 shows a schematic plan view of another synthetic lawn according to the first embodiment.

Figure 6 shows a cross sectional side view of a synthetic lawn according to a variation of first embodiment of the invention.

Figure 7 shows a cross sectional side view of a cell wall for use with the invention.

Figure 8 shows a plan view of the cell wall of figure 7.

Figure 9 shows a cross sectional side view of a synthetic lawn according to a first embodiment of the invention.

Figure 10 shows a side view of another spacer layer that may be used in the figure 1 embodiment.

3818-1.doc -4- Figure 11 shows a side view of another spacer layer that may be used in the figure 1 embodiment.

Figure 12 shows a side view of layer of synthetic turf incorporating a spacer.

Detailed Description of Preferred and other Embodiments Referring to figures 1 to 5 there is shown a cross section though a piece of ground upon which is laid a synthetic lawn and water collection system 12.

The upper surface 14 of the ground 10 is preferably graded to lie in a plane and the plane is preferably angled to the horizontal to promote water run off, as will be discussed later.

Laid upon the upper surface 12 of the ground 10 is a spacer layer 16. This layer 16 is preferably water impervious or substantially water impervious and in the preferred embodiment is formed of a single polypropylene layer. The layer 16 has a base 18 extending generally in a plane with a series of protrusions 20 extending upwards from the base 18. In the preferred embodiment shown the layer 16 is a sheet of material with the protrusions 22 being formed of the base and extending upwards to form hollow pillars. Such a structure may be easily made by heating a plastics sheet to a plastic temperature and deforming the sheet whilst plastic. If desired, the protrusions may be solid. Plastics other than polypropylene may be used. The protrusions need not be integral with the base 18 and a separate spacer structure may be used in conjunction with a separate water impervious base layer 18. As will be apparent later, it is merely preferred that there be a substantially impervious layer to trap and direct water and a structure to provide a void 21 into which water may enter and flow.

Laid upon the spacer layer 16 is a layer of conventional synthetic turf 22. The turf layer is normally formed of a woven fabric 24 having many U shaped strands of 3818-1.doc plastics material 26 extending through the fabric 24 to form the "blades" of the synthetic grass. A substantially impervious rubber or rubber like layer 28 is applied to the lower surface of the fabric to secure the strands 26 in position and to provide a desired amount of rigidity to the finished product. The specific construction of the synthetic turf 22 is not important. In the preferred embodiment it is desirable that at least some of any water falling on the turf may pass through the turf layer into the void 21 defined between the underneath of the turf layer 22 and the base 18. In the preferred embodiment drainage holes 30 are provided in the turf layer 22 to allow water to seep into the void 21. It will be appreciated that some synthetic turfs may be manufactured with a base that is sufficiently porous that discrete holes are not required. As will be explained later, it is not critical that all water falling on the turf pass through the turf into the void 21.

As seen in figure 3, the protrusions 20 on the spacer layer 16 are provided in a grid like arrangement and so do not prevent the movement of water in any direction. Other configurations are possible. Whilst a structure that allows water flow in any direction is preferred, this is not critical. For example, the void forming structure may be a series of substantially parallel ribs or similar. The ribs may be arranged so as to allow water flow along only one direction or there may be multiple sets of discontinuous ribs to allow water flow in a number of different directions. A corrugated structure may be used to provide the void forming structure and the impervious barrier.

Referring to figure 10, there is shown a spacer layer 100 having a generally planar base 102 with a series of parallel ribs 104 extending upward from the base 104, preferably perpendicular to the base. The ribs may have a T shaped cross-section, as shown, to provide a greater area to take any load or may have a rectangular cross section.

3818-1.doc -6- Figure 11 shows a spacer layer 110 that is merely a corrugated sheet of water impervious material, such as a suitable plastics material. The peaks 112 of the corrugations support the synthetic turf whilst the troughs 112 of the corrugations provide voids or channels 116 into which water may pass and drain away.

The spacer structure may be incorporated into the synthetic turf rather than being a separate component and figure 12 shows a synthetic turf 120 having strands 122 secured in a fabric layer 124. On the underside of the fabric layer 122 are a series of protrusions 126 that extend downwards so that in use the fabric layer is raised above whatever it is supported on. The protrusions 126 may be discrete legs or pillars, similar to those of the spacer of figure 3, ribs similar to those of figure or a corrugated surface such as in figure 11 or any other suitable construction.

In use a water impervious layer, such as a plastics sheet may be laid upon the ground and the synthetic turf lain on the water impervious layer, so defining a drainage void. It will be appreciated that when using a corrugated layer or similar attached to the underside of the synthetic turf a separate water impervious layer would not be necessary.

The water impervious layer may be attached to or formed integrally with the protrusions so that the synthetic turf incorporates the drainage structure and may be simply laid upon the ground.

The protrusions 20 are preferably spaced sufficiently close to each other such that when the turf is loaded there is insignificant movement of the turf layer 22 and it is not readily apparent that the turf layer 22 is not supported continuously. This is merely preferred for aesthetic and sensual reasons and is not essential to the working of the invention. It has been found that a spacer layer with protrusions on a square grid at about 25 mm centres and with the tops of the protrusions having a diameter of about 9 mm provides sufficient support in most circumstances.

3818-1.doc -7- As mentioned above, the surface 12 of the ground 10 is preferably angled to the horizontal to promote water run off. When the aim is to provide the look of a horizontal surface this slope is in the order of 1 or 2 degrees but this will depend on the nature of the spacer layer 16 and the amount of water flow desired. In areas of high rainfall a larger angle may be desired. It is not critical to the invention that the surface of the turf is substantially horizontal and the invention may be used where the synthetic turf follows the lay of the land. As such the turf may be at angles of 50 or 60 degrees or more to the horizontal.

As will be explained later, it is not critical that all water falling on the turf 22 pass into the void 21. It will be appreciated that the slope of the land need not be consistent and, if desired, the slope may be varied, so long as the general direction is downhill. The ground may even slope uphill for a short section without stopping or substantially limiting run off.

In use, rain falls on the turf 22 and seeps through the holes 30 in the turf into the void 21. The water then flows downhill to a collection point 34. The water is then transferred, directly or via pipe work 36, to one or more holding tanks 38. These holding tanks 38 may be located partially or fully under the turf 22, as shown in figure 1, or may be located remotely from the turfed area, as shown in figures 4 and The tanks hold the water until used and the water may be used on adjacent gardens or the like or used domestically. Water may be supplied using gravity or by use of a pump 40. If desired the tanks may be merely used a temporary holding tanks, with the water being pumped to a larger tank when the amount of water in the tanks exceeds a threshold.

3818-1.doc -8- Depending of the shape of the synthetically turfed area and the terrain the water passing into the void space may be directed to one or more collection points or to a gutter 42 or the like, as shown in figures 4 and Typically an area of synthetic lawn is not a regular shape but is an irregular shape defined by garden beds, paths fences, buildings and the like. Accordingly, it may be necessary to provide different sections of the lawn with different slopes.

In the preferred embodiments the peripheral edges of the synthetic lawn area are bounded by gutters. During heavy rain, not all the water falling on the turf 22 will pass through the turf 22 into the void 21 and instead will remain on the surface of the turf and flow downhill until it reaches an edge of the turf. By placing gutters around the edges of the turf any surface run off may be captured and also directed into the holding tanks. It will be appreciated that the use of gutters or other water capturing devices at the edges of the turf mean that it is not critical how much water flows through the synthetic turf structure into the void space 21.

Referring to figure 4 there is shown a rectangular area of turf 22 that is sloped to a single collection point 34, as indicated by arrow 44. Water flowing in the void or on the surface flows downhill until it reaches a gutter. The void may discharge into the gutter and the water flows in the gutter to the collection point 34. Figure shows rectangular area of turf that is sloped to drain water into a gutter 42, which is then configured to direct water to an outlet 34, as indicated by arrow 46. Arrow 46 represents water flow in the void 21 and on the surface of the turf 22 whilst arrows 47 represent the direction of water flow in the gutters.

The tanks 38 used for water collection may be formed of any suitable material and may be above ground or below ground. As such, the tanks 38 may be formed of concrete, plastics, metal or other suitable materials.

3818-1.doc -9- In the preferred embodiments the tanks are located below ground and formed using open cell plastics structures normally used for stormwater retention and slow water release. A suitable open cell structure is a Versitanktm stormwater tank produced by Elmich Australia Pty Ltd of Concord NSW. Open cell stormwater tanks have open cell walls that allow water to flow into and out of the tank relatively freely whilst providing a reasonably strong box that may support a load placed upon its upper surface. Such stormwater retention tanks are generally modular units that may be placed together to create a larger tank and provide a high volumetric efficiency.

Figures 7 and 8 schematically show a portion of the wall 80 of such an open cell used for the tanks. The wall 80 is formed of two sets of mutually orthogonal walls, 82 and 88. The walls thus define voids 86 between them through which water may flow. It will be appreciated that the specific construction of the wall is not critical.

Whilst stormwater tanks are used to temporarily retain stormwater and release the water into the ground, via seepage, or to a stormwater drain via a controlled flow outlet, in the present invention the aim is to retain the water and prevent seepage into the ground. Referring to figure 6, a storage volume is provided underneath part of the turf layer. Prior to installation of the turf layer 22, the ground is excavated to a suitable depth to form a pit 50. The excavated pit 50 is lined with an impervious material, such as a plastics sheet 52. The sheet 52 needs to have a thickness and durability that small rocks and the like will not normally puncture the sheet material. A suitable plastics sheet material is that commonly used in above ground swimming pools.

The tank modules 54 are placed in the lined pit 50 and the plastics sheet 52 is then wrapped around the sides and top of the tank modules 54 to enclose the modules.

The tank modules 54 are typically about 500 to 600 mm high so the pit 50 does 3818-1.doc not need to be very deep. Any joins and seams are sealed so as to be substantially watertight. This may be by any conventional means, such as by gluing or welding.

The plastics wrapped modules thus form a substantially watertight tank 56. The sides of the excavation are backfilled, so as to provide side support for the tanks and the plastics sheet. The plastics sheets 52 are thus held between the modules and the soil, with the pressure of any water 58 in the tank being transferred to the soil 10 without damage to the plastics sheet.

The spacer layer 16 and the turf layer 22 are then laid on the top of the tank 56 as previously described and water flows to a collection point 60 and then to tank 56, either directly or via pipe work 62.

It will be appreciated that the spacer layer 16 is substantially impervious to water and will prevent water passing through the turf 22 into the tank 56, if it is formed of open cell modules, and so the plastics sheet 52 may be omitted from the top of the tank.

Referring to figures 9, there is shown a second embodiment of the invention, in which water passes through the synthetic turf 22 layer directly into a holding tank One or more holding tanks 70 are located underneath the area to be covered with synthetic turf. The tank 70 is provided with openings 64 in the upper surface 66.

In this regard the stormwater cells wrapped in an impervious plastics sheet as per the embodiment of figure 6 are preferred as the top side of a cell is mainly openings. It will be appreciated that the top of the cells needs to be left uncovered to allow water to enter the tank 70. The tank may be formed of other materials or combinations of materials, so long as the top surface of the tank has apertures to allow ingress of water into the tank. Whilst the plastics cells described have a load rating of up to about 7 t/m 2 higher load ratings may be needed. Thus, for 3818-1.doc 11 example, an open topped concrete tank may be formed or positioned in a pit and provided with a metal grate as its upper surface. Conversely, where no or very minimal load is placed on the tank a tank having minimal load bearing capacity may be used.

The top of the tank is preferably overlaid with a geotextile 68 to prevent the ingress of soil or sediment into the tank. However, as the top of the tank will only be overlaid with synthetic material and no soil, the geotextile maybe omitted. A layer of synthetic turf 22 is then laid directly on the geotextile or the tank top if there is no geotextile. In this embodiment there is no spacer layer as in use water passes through the synthetic turf layer and falls directly into the tank. Any surface run off is collected by gutter 72 and flows into tank 70 via pipe work 72. If desired, a porous material such as sand may be placed between the geotextile 68 and the turf layer 22 to compensate for minor height differences in the tops of the modules.

Since the water passes directly into the tank it is not necessary to have the tank and turf follow any particular slope. If desired the turf may lie in a substantially horizontal plane.

It will be appreciated that in some circumstances it may not be possible or desirable to have the entire turf area underlaid with storage tanks. In such circumstances a part of the turf may be provided with open topped tanks with the remainder supported by an impervious spacer layer as in figures 1 to 5. Depending of the topography the spacer layer(s) may drain into the open topped underground tanks or may drain into another tank or tanks.

The use of direct collection using the open topped tanks has significant advantages for synthetic playing fields. There is no need to provide a slope on the ground to promote drainage and instead the turf may be laid to lie in a 3818-1.doc -12substantially horizontal plane. For those fields that need to be wet when used, such as hockey fields, the use of direct collection can reduce water consumption and aid in recycling whilst minimising concerns for contamination by rubbish, leaves or the like. Water may be pumped from the under turf tanks and sprayed onto the synthetic turf. The water seeps though the turf for reuse. Because the water does not run of into open gutters (although these may be provided) there is no opportunity for rubbish, leaves or the like to enter the system.

It will be apparent to those skilled in the art that many obvious modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention.

Claims (4)

1. 3818-1.doc 13- The claims defining the invention are as follows: 1. A synthetic lawn system having a layer of synthetic turf and water collection means for collecting water that seeps or otherwise passes through or runs off the synthetic turf or both.
2. 2. The synthetic lawn system of claim 1 including a void located beneath the synthetic turf to capture water seeping or otherwise passing through the synthetic turf.
3. 3. The synthetic lawn system of claim 2 wherein the void is at least partially defined by a void forming structure.
4. 4. The synthetic lawn system of claim 2 wherein the void forming structure is formed integrally with the synthetic turf. The synthetic lawn system of claim 3 or claim 4 wherein the void forming structure includes a sheet or layer having protrusions, ribs or other structures to support the synthetic turf. 6. The synthetic lawn system of claim 5 wherein the void forming structure is a corrugated sheet. 7. The synthetic lawn system of claim 3 wherein the void forming structure is also a storage tank. 8. The synthetic lawn system of any one of the preceding claims including at least one tank located beneath the layer of synthetic turf and wherein the at least one tank has apertures or voids in the top side of the tank, whereby water seeping or otherwise passing through the layer of turf passes into the at least one tank. 3818-1.doc 14- 9. The synthetic lawn system of claim 7 or claim 8 wherein the at least one tank includes at least one open celled stormwater retention module. The synthetic lawn system of claim 9 wherein the at least one open celled stormwater retention module is surrounded by a substantially water impervious layer. 11. The synthetic lawn system of any one of the preceding claims including a substantially water impervious barrier located at least beneath the void. 12. The synthetic lawn system of claim 11 when dependent on claim 3 wherein the impervious barrier and the void forming structure are integrally formed. 13. The synthetic lawn system of claim 11 wherein the water impervious layer is a plastics sheet or film. 14. The synthetic lawn system of any one of the preceding claims wherein the water collection means includes at least one gutter extending along at least part of the periphery of the layer of synthetic turf. 15. The synthetic lawn system of claim 14 wherein the at least one gutter is configured to collect surface run off and direct it to one or more collection points. 16. A synthetic lawn system, substantially as herein descried with reference to the drawings. Dated 23 June 2006 William F Rorke By his Patent Attorneys Acumen Intellectual Property