Subsurface drainage system

Abstract

The present invention is directed to a subsurface drainage system for a playing surface. The subsurface drainage system includes a subgrade, an intermediate layer disposed over the subgrade, a layer of semi-permeable filter fabric disposed over the intermediate layer, an upper permeable layer disposed over the layer of filter fabric and on which the playing surface is disposed, and a hydronic piping network disposed in the upper layer near the layer of filter fabric. The layer of filter fabric has a permeability less than the permeability of the intermediate layer and such that the layer of filter fabric functions as a perching layer to support a perched water table above the filter fabric. The hydronic piping network is positioned within the perched water table such that the water of the perched water table functions as a heat exchanger to facilitate heating and cooling of the upper layer upon the hydronic piping network being heated or cooled.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No. 60/600,095, filed Aug. 9, 2004, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a subsurface drainage system for facilitating water drainage from a land surface, and more particularly but not by way of limitation, to improved subsurface drainage system for an athletic field, such as a putting green or football field, which subsurface drainage system is capable of retaining adequate water to facilitate turf growth and temperature regulation while promoting rapid infiltration of water through the subsoil structure.

2. Brief Description of Related Art

Conventionally, drainage for athletic fields, such as football fields and putting greens, has been constructed with the use of a network of drain pipe buried under the playing surface. The drain pipe is provided with a multiplicity of perforations in the circumferential wall thereof. Rainwater or irrigation water penetrating into the playing field is introduced into the drainage pipe through the perforations in the circumferential wall thereof, collected to a trunk pipe, and drained.

Today, most playing fields are constructed to have an intermediate layer comprising gravel and a root zone layer comprised primarily of sand to promote drainage and thus prevent root rot of the turf grass. As such, even a small amount of water rapidly penetrates the root zone layer and passes into the drainage system. Agricultural chemicals or fertilizers that are used to maintain or control the grass also flow out together with the water.

During warm weather months, watering of natural grass playing fields is required for growing and maintaining the grass. With the conventional concentrated drainage system, however, a putting green having a root mix layer comprised primarily of sand would require watering at least about twice per day in summer, even if a water-retaining material such as perlite or pumice is incorporated as an improving material in the root mix. Such watering requires time and labor.

Additionally, temperature variation can cause problems in maintaining healthy grass for certain temperature sensitive grasses. To this end, piping networks have previously been installed in the subsurface in an attempt to regulate the temperature of the root zone layer. The same is true with respect to artificial turf surfaces in attempt to maintain a safe playing surface, one which is not too hot or too cold. The problem encountered with such piping networks is that it is difficult to uniformly heat or cool the root zone layer without employing a dense network of pipes. Obviously, increasing the amount of pipe used increases the cost of the system. It would be preferred to obtain a uniform distribution while using a minimum amount of pipe.

In view of the above-mentioned concerns, a need exits for a subsurface drainage system that is capable of retaining adequate water while promoting rapid infiltration of water through the subsoil structure and which is adapted to uniform temperature regulation. It is to such a subsurface drainage system that the present invention is directed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic sectional view illustrating a subsurface drainage system for natural turf constructed in accordance with the present invention.

FIG. 2 is a schematic sectional view illustrating another embodiment of a subsurface drainage system for natural turf constructed in accordance with the present invention.

FIG. 2A is a top cutaway view of FIG. 2 illustrating a hydronic piping network for natural turf constructed in accordance with the present invention.

FIG. 3 is a schematic sectional view illustrating another embodiment of a subsurface drainage system for natural turf constructed in accordance with the present invention.

FIG. 4 is a schematic sectional view of a subsurface drainage system for artificial turf constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, shown therein is a subsurface drainage system 10 constructed in accordance with the present invention. The subsurface drainage system 10 is similar to that recommended by the United States Golf Association for the construction of putting greens with the exception that the subsurface drainage system 10 includes a semi-permeable filter fabric layer at the bottom of the root zone layer. The 2004 revisions of the USGA Recommendations for a Method of Putting Green Construction is hereby expressly incorporated herein by reference. More particularly, the subsurface drainage system 10 of the present invention includes a subgrade or base 12, an intermediate layer 14, a semi-permeable filter fabric layer 16, an upper or root zone layer 18, and a turf layer 20. Optionally, an impermeable liner 22 is disposed between the base layer 12 and the intermediate layer 14. In instances where it is desirable to allow some permanent deep infiltration of surface drainage, the impermeable liner 22 may be replaced with a semi-permeable geotextile fabric.

The base layer 12 is graded according to methods and designs known in the art to define one or more surfaces sloping down to points or lines of fluid collection (not shown). The base layer 12 should be thoroughly compacted to prevent settling.

The intermediate layer 14 provides a drainage blanket and is therefore formed of materials, such as crushed stone, pea gravel, rubber particles, or combinations thereof. As used herein, “intermediate layer” means a gravel layer or a gravel layer and an intermediate layer as those terms are used by the USGA in its recommendations for a method for constructing a putting green.

The root zone layer 18 is generally comprised of a homogenous mixture of sand, organic matter, and inorganic matter.

The filter fabric layer 16 is interposed between the intermediate layer 14 and the root zone layer 18. When a filter fabric layer 16 is not interposed between the root zone layer 18 and the intermediate layer 14, the sand of the root zone layer 18 can become commingled with the intermediate layer 14 and thereby effect the permeability of the intermediate layer 14 and the water retention capacity of the root zone layer 18. The filter fabric layer 16 will function to prevent particles from the root zone layer 18 from migrating into the intermediate layer 14, thereby maintaining the permeability of the intermediate layer 14.

The permeability of the filter fabric layer 16 is less than the permeability of the intermediate layer 14. As such, the filter fabric layer 16 will function to distribute and support a uniform layer of water above the filter fabric 16 in the form of a perched water table 24. Because the permeability of the filter fabric 16 is substantially uniform, the perched water table 24 will have a substantially uniform height which will promote uniform turf growth. Furthermore, the permeability of the filter fabric layer 16 should be such that static or un-pressurized water in the root zone layer 18 is held up by the perching layer, but upon the turf receiving irrigation water or rainwater, water percolating downwardly through the root zone layer 18 will increase the water pressure on the filter fabric layer 16 and thus cause water to flow freely through the filter fabric layer 16 and the intermediate layer 14. A suitable material for use as the filter fabric layer is a polyester spunbond non-woven fabric having a weight in a range of from about 65 gsm to about 205 gsm, and more preferably in a range of from about 110 gsm to about 150 gsm.

It will be appreciated that the thickness and composition of each of the layers of the subsurface drainage system 10 may be varied widely depending on factors, such as climate conditions, availability of materials, and intended use of the turf.

FIGS. 2 and 2A illustrate another subsurface drainage system 10a which is similar to the subsurface drainage system 10 described above except that a hydronic piping network 30 is shown disposed in the root zone layer 18 near the filter fabric layer 16 so that the hydronic piping network 30 is positioned within the perched water table 24. By having the hydronic piping network 30 positioned within the perched water table 24, the water will function as a heat exchanger to facilitate heating and cooling of the root zone layer 18. Hydronic piping networks and their components are well known in the art. Thus, no further description of its components, construction, or operation is believed necessary in order for one skilled in the art to understand and implement the subsurface drainage system 10a of the present invention.

FIG. 3 shows another embodiment of a subsurface drainage system 10b constructed in accordance with the present invention. The subsurface drainage system 10b is similar to that disclosed above and in U.S. Pat. No. 5,848,856 which is hereby expressly incorporated herein by reference. The subsurface drainage system 10b includes a base layer 40 having at least one sloped surface 41, a drainage collection point (not shown) at the bottom of each sloped surface, and an intermediate layer 42 formed by a drain structure overlying the base layer 40, a filter fabric layer 44, a root zone layer 46, and a turf 48.

The drain structure 42 is a thermoplastic mat with a laterally extensive backing grid having a plurality of struts 43a defining grid openings therebetween and a plurality of spaced tubular support members 43b projecting from the backing grid 43a, whereby fluid may flow through the backing grid 43a and between the support members 43b. The filter fabric layer 44 is a semipermeable geotextile fabric disposed in flush contact upon the drain structure 42, and preferably, but optionally, an impermeable liner 50 is disposed between the base layer 40 and the drain structure 42. In instances where it is desirable to allow some permanent deep infiltration of surface drainage, the impermeable liner 50 may be replaced with a semi-permeable geotextile fabric.

The subsurface drainage system 10b further includes a hydronic piping network 52 disposed in the root zone layer 46 near the filter fabric layer 44 so that the hydronic piping network 52 is positioned within a perched water table 54. By having the hydronic piping network 52 positioned within the perched water table 54, the water will act as a heat exchanger to facilitate heating or cooling of the root zone layer 46, as desired. Hydronic piping networks are well known in the art. Thus, no further description of its components, construction, or operation is believed necessary in order for one skilled in the art to understand and implement the subsurface drainage system 10b of the present invention.

FIG. 4 shows a subsurface drainage system 10c for an artificial turf 68 constructed in accordance with the present invention. The subsurface drainage system 10c includes a base layer 60 having at least one sloped surface 61, a drainage collection point (not shown) at the bottom of each sloped surface 61, and an intermediate layer 62 formed by a drain structure overlying the base layer 60, a filter fabric layer 64, an upper layer 66, and the artificial turf 68. The artificial turf 68 is provided with a porous backing 69 such as a geotextile fabric or fabric with holes formed therein to permit drainage therethrough.

The drain structure 62 is a thermoplastic mat with a laterally extensive backing grid having a plurality of struts defining grid openings therebetween, and a plurality of spaced support members projecting from the backing grid, whereby fluid may flow through the backing grid and between the support members. An impermeable liner 70 is disposed between the base layer 60 and the drain structure 62. In instances where it is desirable to allow some permanent deep infiltration of surface drainage, the impermeable liner 70 may be replaced with a semi-permeable geotextile fabric.

The upper layer 66 may be formed of sand, gravel, rubber, a porous pad, or combinations thereof.

The subsurface drainage system 10c further includes a hydronic piping network 72 disposed in the upper layer 66 near the filter fabric layer 64 so that the hydronic piping network 72 is positioned within the perched water table 74. By having the hydronic piping network 72 positioned within the perched water table 74, the water will act as a heat exchanger to facilitate heating and cooling of the upper layer 66 and thus the artificial turf 68. Hydronic piping networks are well known in the art. Thus, no further description of its components, construction, or operation is believed necessary in order for one skilled in the art to understand and implement the subsurface drainage system 10c of the present invention.

From the above description, it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the invention. While a presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed and as defined in the appended claims.

Claims

1. A subsurface drainage system for a playing surface, comprising:

a subgrade;

an intermediate layer disposed over the subgrade and formed from at least one material to define a drainage blanket layer;

a layer of semi-permeable filter fabric disposed over the intermediate layer, the layer of filter fabric having a permeability less than the permeability of the intermediate layer and such that the layer of filter fabric functions as a perching layer to support a perched water table above the layer of filter fabric;

an upper permeable layer disposed over the layer of filter fabric and on which the playing surface is disposed; and

a hydronic piping network disposed in the upper layer near the layer of filter fabric so that the hydronic piping network is positioned within the perched water table such that the water of the perched water table functions as a heat exchanger to facilitate heating and cooling of the upper layer upon the hydronic piping network being heated or cooled.

2. The subsurface drainage system of claim 1 wherein the layer of filter fabric is a polyester spunbond non-woven fabric having a weight in a range of from about 110 gsm to about 150 gsm.

3. The subsurface drainage system of claim 1 wherein the subgrade is contoured to define one or more surfaces sloping down to points or lines of fluid collection.

4. The subsurface drainage system of claim 1 wherein the intermediate layer is formed at least one material selected from the group consisting of crushed stone, pea gravel, rubber particles, and combinations thereof.

5. The subsurface drainage system of claim 1 wherein the intermediate layer is a thermoplastic mat having a laterally extensive backing grid and a plurality of spaced tubular support members projecting from the backing grid whereby fluid may flow through the backing grid and the support members.

6. The subsurface drainage system of claim 1 wherein the upper layer is a root zone layer comprising at least one material selected from the group consisting of sand, organic matter, inorganic matter and combinations thereof.

7. A subsurface drainage system for regulating the temperature of a root zone, comprising:

a semi-permeable filter fabric having a permeability such that the filter fabric functions as a perching layer to support a perched water table above the filter fabric;

a root zone layer disposed over the layer of filter fabric;

a natural turf layer disposed on the root zone layer; and

a hydronic piping network disposed in the root zone layer near the layer of filter fabric with the hydronic piping network positioned within the perched water table such that the water of the perched water table functions as a heat exchanger to facilitate heating and cooling of the root zone layer upon the hydronic piping network being heated or cooled.

8. The subsurface drainage system of claim 7 wherein the layer of filter fabric is a polyester spunbond non-woven fabric having a weight in a range of from about 110 gsm to about 150 gsm.

9. A subsurface drainage system for regulating the temperature of an artificial turf, comprising:

a semi-permeable filter fabric having a permeability such that the filter fabric functions as a perching layer to support a perched water table above the filter fabric;

a permeable upper layer disposed over the layer of filter fabric;

an artificial turf layer disposed on the upper permeable layer; and

a hydronic piping network disposed in the upper permeable layer near the layer of filter fabric with the hydronic piping network positioned within the perched water table such that the water of the perched water table functions as a heat exchanger to facilitate heating and cooling of the upper permeable layer and thus the artificial turf layer upon the hydronic piping network being heated or cooled.

10. The subsurface drainage system of claim 9 wherein the layer of filter fabric is a polyester spunbond non-woven fabric having a weight in a range of from about 110 gsm to about 150 gsm.