GB2396379A

GB2396379A - Water management system

Info

Publication number: GB2396379A
Application number: GB0400836A
Authority: GB
Inventors: Howard Lloyd Robinson; Colin Andrew Loveday; Nicholas Paul Toy; Benjamin John Sealey
Original assignee: Tarmac Ltd
Current assignee: Tarmac Ltd
Priority date: 2002-07-16
Filing date: 2003-07-16
Publication date: 2004-06-23
Anticipated expiration: 2023-07-16
Also published as: GB2396379B; GB0400836D0

Abstract

The water management system, primarily for managing storm water or spillages on a surfaced area, comprises a permeable surface course 11 of a settable material which is laid on-site in a flowable state, a permeable understructure including a porous foundation layer 20, there being a drainage conduit 25 from the foundation layer to beyond the boundary of the surfaced area, wherein the permeable surface course is provided by porous concrete which is provided by a mix including cement, water and only course aggregate having a minimum particle size of 5 mm. The surface course may include an overlay of porous asphalt and may be textured or coloured. The permeable understructure may include a supporting substrate 12 between the surface course and the foundation layer that may include permeable asphalt and that may comprise upper 13 and lower 14 binder courses where the aggregate of the lower course is coarser than that of the upper course. The system may also include a synthetic geo-textile membrane 16 that permits the passage of water therethrough while preventing the passage of contaminant particles. The foundation may comprise a filter layer.

Description

GB 2396379 A continuation (72) cont Nicholas Paul Toy Benjamin John Sealey

(74) Agent and/or Address for Service: Forrester Ketley & Co Chamberlain House, Paradise Place, BIRMINGHAM, B3 3HP, United Kingdom

Title: Water Management System Description of Invention

This invention relates to a water management system for managing storm water and/or spillage on a surfaced area.

As a result of an increasing proportion of the land surface being surfaced, particularly in urban regions, an increasing proportion of storm water is dealt with by draining immediately directly into man-made drains and into water courses and the like, thus placing a high burden on such drainage systems. In contrast, in unsurfaced areas, the water may pass into and dwell in the ground and seep into water courses and the like over a longer period.

Moreover storm water which runs off surfaced areas is not naturally cleansed by bacteria and the like action as is water which passes into the ground. As a result, water courses and the like can become rich with contaminants which otherwise would have been cleansed from the water.

It has been proposed in GB patent 2294077 to provide a paved surface course through which water may pass into a substrate beneath, with there being a water impermeable membrane beneath the substrate, which membrane contains particles of the substrate in which water passing through the paved surface course may dwell, with there being drains from the substrate for the water. However the use of an impermeable membrane restricts the capacity of the system in that in the event of a particularly heavy fall of water, the volume contained by the membrane may fill up, and thus water will need to be discharged via the drains, thus contributing to the burden imposed on local drainage systems by run- off water from other surfaced areas.

In accordance with the present invention we provide a water management system for managing storm water over a surfaced area, the system including a permeable surface course of a gettable material which is laid on-site in a plowable state, a permeable understructure beneath the surface course, the permeable understructure including a porous foundation layer, there being a drainage conduit from the foundation layer to beyond the boundary of the surfaced area.

With the system of the invention, water may exit the system into the ground beneath the system as well as through the drainage conduit, and thus the system of the invention provides the advantages of the system disclosed in GB-

A 2294077 whilst overcoming a major problem with this system. Furthermore, in GB-A 2294077 the surface course is paved, and such a surface course requires a level of skill and period of time to lay, which is not required by the system of the present invention in which the surface course is provided by a gettable material which is laid on-site in a plowable state.

In one example, the permeable surface course is provide by porous asphalt. The porous asphalt of the surface course may include penetration grade bitumen, such as 100/150 of European Standard EN12591, but preferably, particularly where the surface course is intended to be driven upon by vehicles, the surface course may include penetration grade bitumen modified with fibres and/or polymer modified bitumen. In each case, preferably the porous asphalt includes aggregate the particles of which are all able to pass through a 14mm sieve, and preferably a 1 Omm sieve and more preferably a 6mm sieve.

A top surface of the surface course may be textured/coloured as desired suitable for its particular use, for example to provide for increased skid resistance. The surface course may have a thickness depending upon the use of the system. In one example, e.g. where the system is intended for medium to heavy traffic use and the understructure includes a supporting substrate between the surface course and the foundation layer, the surface course may have a

thickness of about 10 mm to 50 mm and preferably of about 25 mm; in another example, where no such supporting substrate may be provided, e.g. a system intended for only light, pedestrian traffic use, the surface course may have a thickness of between 40 mm and 80 mm.

Alternatively, the permeable surface course may be provided by porous concrete. The porous concrete may be provided by a concrete mix including cement, water and only coarse aggregate, by which we mean aggregate having a minimum particle size of 5 mm, and desirably a maximum particle size of 40 mm and more preferably a particle size between 5 mm and 20 mm. Such a concrete is known as a "no-fines" concrete.

Alternatively, the porous concrete may be provided by a mix including cement, water, and predominantly coarse aggregate. For example, the concrete mix as laid, may include less than 8% by weight of fine aggregate, having a particle size of 3 mm or less. The mix may include additives as required to improve the strength, wear resistance and cohesion of the surface course.

In each case, the permeable surface course may have a thickness of between 100 mm and 300 mm depending upon the traffic for which the system is intended. If desired, to improve ride quality over the system, e.g. to reduce kaffc noise the permeable surface course of porous concrete may include an overlay of porous asphalt.

Where a permeable supporting substrate is provided, this may include permeable asphalt. Particularly, but not exclusively where the permeable surface course is of porous asphalt, a permeable supporting substrate including at least two courses may be provided in which aggregate of the asphalt of the lower of the two courses is coarser than aggregate of the asphalt of the higher of the two courses.

The upper course of such a permeable supporting substrate may be a binder course and may include aggregate all the particles of which are able to pass through 28 mm sieve and preferably a 20 mm sieve, and the permeable

asphalt may contain penetration grade bitumen, such as 100/150 grade bitumen, although again the asphalt may include penetration grade bitumen bound by fibres and/or polymer modified bitumen if desired. The binder course may have a thickness of between 30 mm and 80 mm and preferably of about 60 mm. The lower course of the permeable supporting substrate may be a base layer. Where the permeable surface course is of porous concrete, the permeable supporting substrate may be provided by a base layer alone.

In each case the base layer may include aggregate all the particles of which are able to pass through a 40 mm sieve, and the asphalt may again include a penetration grade bitumen such as 160/220 grade. The base layer may have a thickness of between 30 mm and 80 mm and preferably of about 70 mm.

If desired a semi-permeable membrane may be provided beneath the supporting substrate.

The semi-permeable membrane may be a synthetic geo-textile membrane, although any other suitable kind of membrane may be provided which permits the passage of water therethrough and which may substantially prevent the passage of contaminant particles into the foundation layer and ground beneath. Thus contaminants will dwell in the permeable supporting substrate and this will give time for bacteria and the like to cleanse the contaminants. The foundation layer may include a filter layer of particulate material with interstitial cavities between the particles. The particle sizes may vary such that all of the particles are able to pass through a 300 mm sieve but none of the particles are able to pass through a 6mm sieve. The foundation layer may have a thickness of at least 200 mm and preferably of about 295 mm, but may have a greater thickness as required.

The foundation layer may be laid on a natural or laid sub-grade.

The drainage conduit may extend to a man-made or natural drain, or may be a simple soak away, but in each case, preferably the drainage conduit extends into the foundation layer and has passages for water from the foundation layer through walls of the conduit.

Embodiments of the invention will now be described with reference to the accompanying drawing which is a schematic section through a water management system in accordance with the present invention.

Referring to the drawing a water management system 10 for a surfaced area includes a permeable surface course 11, and an understructure including a permeable supporting substrate 12 which includes an upper binder course 13 and a lower base layer 14, a semi-permeable membrane 16 beneath the supporting substrate 12, and a foundation layer 20 which is laid on a natural or man-made sub-grade 22. One or more drainage conduits 25 extend from the foundation layer 20 beyond a boundary of the surfaced area over which water is managed by the system 10 of the present invention.

The design and construction of each of the layers is critical to proper performance of water management for the surfaced area and thus the makeup of each of the layers will now be described.

The surface course 11 is made of a porous asphalt to provide a wearing surface suitable for the location of the surfaced area. For example, where the surfaced area will in use be subject to only light wear, for example in a lightly used pedestrianised area, the porous asphalt of the surface course 11 may be made to include a suitable penetration grade bitumen, such as 100/150 bitumen.

However, where the surfaced area is likely to be subjected to heavier wear, a more robust surface course 11 may be provided. For example where the surfaced area is for a car park where the surface course 11 will be subjected to vehicular traffic, the surface course 11 may include penetration grade bitumen modified with fibres and/or polymer modified bitumen.

Furthermore, the top surface lla of the surface course 11 may be textured as desired, for example to provide improved skid resistance/grip for pedestrian andlor vehicular traffic on the surfaced area.

In the example shown in the drawing, the porous asphalt includes aggregate which preferably is of about 6 mm maximum particle size, so that such aggregate is able to pass through a 6 mm sieve although aggregate which is able to pass through a 10 mm or even 14 mm sieve may be provided as required. The thickness of the surface course 11 may be in the range 10 mm to 50 mm although preferably is about 25 mm thick.

The porous asphalt of the surface course 11 permits storm or spillage water on the surfaced area to pass through the surface course 11 to the permeable substrate 12 beneath.

The permeable substrate 12 includes an upper binder course 13 which includes permeable asphalt, aggregate of the permeable asphalt being of a size able to pass through a size 20 mm sieve, but may be passable through a 28 mm sieve if desired. Thus the aggregate is in general coarser than the aggregate used for the surface course 11.

Because the substrate 12 is not subjected to direct wear, the permeable asphalt may include penetration grade bitumen, e.g. 100/150 bitumen, although the binder course 13 at least of the substrate 12 may if desired in particularly heavy wear conditions, include penetration grade bitumen modified with fibres and/or polymer modified bitumen.

The lower course 14 of the substrate 12is a base layer and again may be made of permeable asphalt, but with aggregate which is all able to pass through a sieve of size 40 mm. The base layer 14 may include a penetration grade bitumen, such as 160/220 bitumen.

The binder course 13 may have a thickness of between about 30mm and 80mrn, and typically of about 60 mm, whilst the base layer 14 may have a thickness of between about 30 mm and 100 mm and typically of about 70 mm.

The semi-permeable membrane 16 may be made of any suitable material with passages for water, but the passages are of a sufficiently small size that the semi-permeable membrane 16 retains particulate contaminants which may pass from the top surface 1 la of the system 10, through the surface course 11, and through the supporting substrate 12. One suitable material for the semi-

permeable membrane 16 is a woven geo-textile material, made of a synthetic material with passages for water which are not readily perceivable to the naked eye. The foundation layer 20 beneath the semi- permeable membrane 16 is provided by particulate material which may be natural rock, such as limestone, and/or a recycled material such as an industrial by-product such as slag materials, or brick grog for examples only.

The particle sizes of the foundation layer 20 may vary such that all of the particles are able to pass through a 300 mm sieve but none of the particles are able to pass through a 6 mm sieve. The foundation layer 20 may have a thickness of at least 200 mm and preferably of about 295 mm, but may have a greater thickness as required.

In each case, the particles of the foundation layer 20 provide a filter for water passing through the foundation layer 20, the particles providing between them, interstitial cavities in which water may dwell, whilst bacteria for example, may naturally cleanse the water.

Slowly the water may drain through the filter foundation layer 20 to the sub-grade 22. However to provide for the escape of water from the system 10, within the foundation layer 20 there are provided drainage conduits 25 (only one is shown in the drawings) which in this example are of the kind having through walls thereof, passages (smaller than the minimum particle size of 6mm of the material of the foundation layer 22) or being porous to permit water to drain through the walls and into the interiors of the conduits 25.

The conduits 25 extend downwardly to and outwardly beyond a boundary of the surfaced area over which water is to be managed by the system 10 of the invention, and in one embodiment, the conduits 25 connect with man-

made drains or a natural water course, or the drainage conduits 25 may simply permit the drained water to soak away into the ground, beyond the surfaced area. However if desired, the conduits 25 may include a drainage control valve to enable the rate of water drainage from the foundation layer 20 to be controlled, or the rate of drainage may be restricted by reducing the cross sectional dimension of the interior flow passages of the conduits 25. In each case preferably the rate of drainage is controlled so that water tends to dwell sufficiently long in the filtering foundation layer 20 for the water naturally to be cleansed, before the water is released to the sub-grade 22 beneath or passes from the system 10 via the drainage conduits 25.

The asphalt for the system 10 of the present invention, or at least for one of the layers of the system 10, may be laid from a hot or cold asphalt mix as desired. In another example, the semi-permeable membrane 16 need not be provided in which case the substrate will rest on the foundation layer, but by careful design and construction of the various layers, water may be retained in the system and released in a controlled manner into the sub grade 22 and into the drainage conduits 25.

It will be appreciated that the actual thickness of porous asphalt permeable surface course 11 and construction of the various layers, may be adjusted to suit specific site traffic requirements. For example, in the particular embodiment described, the system 10 is intended for medium to heavily trafficked sites, e.g. carrying a million standard axle loadings, such sites including for examples only, urban routes, retail parks, light-industrial estates, feeder routes onto housing estates etc..

In another example, the porous surface course 11 may be thicker or thinner than indicated.

It is envisaged that a system 10 for only light pedestrian traffic use, may not require the understructure to include a supporting substrate 12. Rather the surface course 11 may be laid directly onto the foundation layer 20, in which case the surface course 11 might have a thickness of between 40 mm and 80 mm. If desired, the permeable surface course 11 may include a plurality of permeable layers rather than the single layer construction described with reference to the drawing.

In another embodiment (not shown), the permeable surface course 11, instead of being provided by porous asphalt, may be provided by a porous concrete. Porous concrete is known which is made as a mix of cement, water, and no fines concrete, by which we mean that substantially all the aggregate includes only particles having a minimum particle size of 5 mm. Desirably the aggregate is substantially all of a similar size, for example having a maximum particle size of 20 mm.

However, the porous concrete for the surface course 11 in a system 10 in accordance with the invention, may include some fine aggregate, which it has been found results in a porous concrete being produced which has a higher resistance to turning stresses and traffic wear than traditional no-fines porous concrete. A example specification of a porous concrete mix which may include

some fine aggregate, by which we mean aggregate having a particle size of 3 mm or less, is as follows: Microsilica slurry (Emsac SOOS) 72 Kgm.

Portland cement 289 Kgm3 Limestone, with nominal 10 mm particle size 1016 Kgm3 Limestone, with nominal 20 mm particle size 455 Kgm3 Limestone dust, of particle size less than 3 mm 145 Kgm3 Added water 74 Kgm3 This resulted in a porous concrete having the following physical properties, namely, a compressive strength (after 28 days) of 43 N. a plastic density of 2045 Kgm3, air voids at 17.5% of the volume, and good resistance to scuffing in a 2 hour vehicle tyre scuffing test.

More generally, the porous concrete surface course 1 1 of the system may include less than 8% by weight fine aggregate.

The permeable surface course 11 of porous concrete may have a slab thickness of between 100 mm and 300 mm, and if desired, a system 10 with such a porous concrete slab surface course 11, may have a single layer permeable supporting substrate 12 beneath, e.g. according to the base layer 14 construction described above for the embodiments with a porous asphalt surface layer. If desired, the permeable surface course of porous concrete may include an overlay of porous asphalt.

In the embodiment described with reference to the drawing in which the permeable surface course 11 is provided by porous asphalt, it will be appreciated that the asphalt is laid in a hot state, such the asphalt may be made to flow to provide the configuration of surface course 11 shown, by rolling or the like, the asphalt setting as it cools to provide the surface course 11.

In the case of porous concrete, this may be laid in a Plowable state, and preferably is allowed to set without compaction, or at least without the degree of compaction typically employed when laying non-porous concrete, to provide the surface course 11.

In each case the permeable surface course 11 is provided by a gettable material which is laid on-site in a flowable state, and sets on-site to provide the surface course 11.

The features disclosed in the foregoing description, or the following

claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A water management system for managing storm water over a surfaced area, the system including a permeable surface course of a gettable material which is laid on-site in a flowable state, a permeable understructure beneath the surface course, the permeable understructure including a porous foundation layer, there being a drainage conduit from the foundation layer to beyond the boundary of the surfaced area, wherein the permeable surface course is provided by porous concrete which is provided by a mix including cement, water and only course aggregate having a minimum particle size of 5 mm.

2. A system according to claim 1 wherein the coarse aggregate of the porous concrete has a maximum particle size of 40 mm.

3. A system according to claim l wherein the porous concrete is provided by a mix including cement, water, and predominantly coarse aggregate.

4. A system according to claim 3 wherein the concrete mix as laid, includes less than 8% by weight of fine aggregate, having a particle size of 3 mm or less.

5. A system according to any one of claims 1 to 4 wherein the permeable surface course has a thickness of between l DO mm and 300 mm.

6. A system according to any one of claim 1 to 5 wherein the permeable surface course of porous concrete includes an overlay of porous asphalt.

7. A system according to any one of the preceding claims where a top surface of the surface course is textured and/or coloured.

8. A system according to any one of the preceding claims wherein the permeable understructure includes a supporting substrate between the surface course and the foundation layer.

9. A system according to claim 8 wherein the permeable supporting substrate includes permeable asphalt.

lO. A system according to claim 9 wherein the permeable supporting substrate includes at least two courses, an upper binder course and a lower base layer, aggregate of the asphalt of the base layer being coarser than aggregate of the asphalt of the binder course.

11. A system according to claim 10 wherein the binder course includes aggregate all the particles of which are able to pass through 28 mm sieve.

12. A system according to claim 11 wherein the binder course includes aggregate all the particles of which are able to pass through 20 mm sieve.

13. A system according to claim 10 or claim 11 or claim 12 wherein the permeable asphalt of the binder course of the supporting substrate includes penetration grade bitumen.

14. A system according to any one of claims 10 to 13 wherein the binder course has a thickness of between 30 mm and 80 mm.

15. A system according to claim 14 wherein the upper course has a thickness of about 60 mm.

16. A system according to claim 8 or claim 9 wherein the permeable supporting substrate is provided by a base layer alone.

17. A system according to any one of claims 10 to 16 wherein the base layer of the permeable supporting substrate includes aggregate all the particles of which are able to pass through a 40 mm sieve.

18. A system according to any one of claims 10 to 17 wherein the permeable asphalt of the base layer includes a penetration grade bitumen.

19. A system according to any one of claim 10 to 18 wherein the base layer has a thickness of between 30 mm and 80 mm.

20. A system according to claim 19 wherein the base layer has a thickness of about 70 mm.

21. A system according to any one of claims 8 to 20 wherein a semi-

permeable membrane is provided beneath the supporting substrate.

22. A system according to claim 21 wherein the semi-permeable membrane is a synthetic geo-textile membrane which permits the passage of water therethrough whilst substantially preventing the passage of contaminant particles into the foundation layer and ground beneath.

23. A system according to any one of the preceding claims wherein the foundation layer includes a filter layer of particulate with interstitial cavities between the particles.

24. A system according to claim 23 wherein the particle sizes of the foundation layer vary such that all of the particles are able to pass through a 300mm sieve but none of the particles are able to pass through a 6mm sieve.

25. A system according to any one of the preceding claims wherein the foundation layer has a thickness of at least 200 mm.

26. A system according to claim 25 wherein the foundation layer has a thickness of about 295 mm.

27. A system according to any one of the preceding claims wherein the foundation layer is laid on a natural or laid sub-grade.

28. A system according to any one of the preceding claims wherein the drainage conduit extends to a natural or man made drain.

29. A system according to any one of claims 1 to 27 wherein the drainage conduit extends to a soak away.

30. A system according to any one of the preceding claims wherein the drainage conduit extends into the foundation layer and has passages for water from the foundation layer through walls of the conduit.

31. A water management system for a surfaced area substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.

32. Any novel feature or novel combination of features shown described herein and/or as shown in the accompanying drawings.