GB2529588A

GB2529588A - Sustainable drainage device

Info

Publication number: GB2529588A
Application number: GB1520521.4A
Authority: GB
Inventors: Brian D Arcy; Neil Campbell
Original assignee: C & D Associates LLP
Current assignee: C & D Associates LLP
Priority date: 2013-09-23
Filing date: 2014-09-23
Publication date: 2016-02-24
Anticipated expiration: 2034-09-23
Also published as: GB2529588B; GB201520521D0

Abstract

A sustainable drainage device (106 figure 1) has a box unit 700 that provides a self-contained sustainable drainage system (SUDS), with flow control, attenuation and water treatment functions. The device can take the form of a rain barrel, a rain garden or of a driveway unit. The device comprises internal partitions 702, 704 which form chambers 706, 708, 710 with at least one partition having a plurality of orifices for regulating flow between chambers. At least one of the chambers may comprise a biological layer 720 to provide a biological degradation of pollutants. The biological layer may comprise plant material planted in soil. A lower portion of the at least one chamber may comprise a filtration material 718 such as gravel.

Description

Sustainable Drainage Device The present disclosure relates to a sustainable drainage device, and in particular to a sustainable drainage device for attenuating pluvial run-off flows from individual piots of land.

When a plot of landis developed, a portion of the plot's area is generally covered by various impermeable surfaces. For example, a domestic house plot will have a house and possibly one or more other structures such as a garage, driveway, patio, garden path, other outbuildings, and so on.

In its green-field state, a plot of land will absorb precipitation over its entire area. Once developed however, the various impermeable surfaces tend to direct pluvial flow into concentrated points from where the flow is discharged into the public drainage network, to a watercourse, or into a soakaway. The cumulative impact of the flow of the pluvial runoff flows from many individual properties can be very considerable, especially during storms when the high flow rates caused by heavy rainfall can exceed the designed flow rates of the drainage system, leading to overflows, surcharging and flooding.

New housing developments need to employ sustainable (urban) drainage systems [SUDS) in order to address these concerns and also to address issues of pollution control. Although most important in large towns and cities, SUDS technology for water management applies equally in the urban and rural contexts, even if the problems can be more acute in the urban context. For this reason the use of the word "urban" is frequently omitted. However in the present disclosure the term 1SUDS" will be used as a generic term that can apply in either urban or non-urban contexts, unless explicitly stated otherwise. The term SUDS is embedded in law and in government guidance in Scotland.

Known SUDS best practices include various measures for attenuating pluvial run-off flows, such as rain-water harvesting, forming permeable surfaces where possible, and incorporating features such as filter strips, filter and infiltration trenches, swales, detention basins, underground storage, wetlands, and ponds both within and/or at the downstream end of a development's drainage network.

Rainwater barrels, also known as water butts, may be used at an individual property to store run-off water so that it can be used for other purposes such as watering plants, washing cars and so on. If empty these vessels may also attenuate pluvial run-off flows to some degree by storing a certain volume of water. Larger vessels, typically provided underground within a property for example beneath a lawn or patio, are sometimes used for retention of pluvial run-off from storms, but their purpose is not for regulating rainfall runoff discharge flows and their design generally makes no such provision.

Flow control devices, combined with separate attenuation storage, for managing rainfall runoff from a development are usually applied at the downstream end of a drainage network, or not at all. Flow is not attenuated at a house plot or equiva'ent small scale.

It would be desirable to achieve flow control and attenuation on a plot by plot basis, in order to minimise liabilities for the public sector, and ensure adequate provision is made by developers at the time of construction of new potentially problematic developments in a catchment.

According to the disclosure there is provided a sustainable drainage device comprising a container that provides both flow control and flow attenuation.

Optionally the container further provides flow treatment.

Flow control, attenuation and treatment together form a sustainable drainage system [SUDS).

So the container provides "SUDS in a box".

The container may comprise a box unit.

Optionally the sustainable drainage device provides passive flow treatment.

Optionally the container is sized for a domestic house plot or plot of similar scale.

Optionally, the container comprises: an inlet for receiving pluvial runoff from a plot; an outlet for connection to a discharge pipe; and a partition member which comprises a plurality of

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orifices arranged in a pattern for regulating the rate of flow between the inlet and the outlet.

Optionally, the device comprises a first internal partition member and a second internal partition member which define an inlet chamber, an outlet chamber and a centre chamber; and said first and second partition members each comprise a plurality of orifices for regulating the rate of flow between the chambers.

Optionally, the centre chamber is further sub-divided into sub-units.

Optionally, the inlet chamber is filled either partially or entirely with filtration media.

Optionally, the filtration media comprise components that can be removed for cleaning or maintenance.

Optionally, an inner surface of a chamber comprising filtration media is lined with a permeable liner.

Optionally, the inlet chamber is provided with a filter element at the point where the inlet is provided.

Optionally, the container is provided with a first partition member comprising a plurality of orifices and a second partition member, wherein the partition members divide the container into portions comprising a centre chamber, an inlet chamber and an outlet chamber, and wherein water can flow through the orifices of the first partition member between the centre chamber and each of the inlet and outlet chambers, but is prevented from flowing directly between the inlet chamber and outlet chamber.

Optionally, the first partition member spans a transverse plane of the container and defines at one side a storage chamber; and the second partition member is provided at the other side of the first partition member and substantially spans a longitudinal plane of the container to define an inlet chamber at one side and an outlet chamber at the other.

Optionally, the first and second partition members are integrally formed together as a one-piece construction.

Optionally, the first partition member comprises one or more orifices at a first portion that is aligned with the inlet chamber and one or more orifices at a second portion that is aligned with the outlet chamber.

Optionally, the device comprises a manifold member in fluid communication with the inlet or with a fluid conduit which is received by the inleL Optionally, the manifold member comprises a plurality of fluid outlets at different positions along the side of the container.

Optionally, the manifold member comprises a pipe with perforations providing the fluid outlets.

Optionally, the orifices comprise openings in the partition member at different heights.

Optionally, the openings provide progressively greater discharge areas at greater heights.

Optionally, the orifices comprise circular apertures.

Optionally, the partition member is planar.

Optionally the partition member is formed integrally with the container.

Optionally, the partition member is a removable or changeable feature of the container.

Optionally the sustainable drainage device comprises a storage volume which stores fluid such that it is isobted from the fluid outlet.

Optionally, the container is provided with a removable lid.

Optionally, the container is clad with timber, plastic or any other suitable material, to form a garden bench or table.

Optionally the container is filled or part-filled with media forming a filtration and attenuation unit or rain garden.

Optionally, an upper portion of any one or more the centre chamber, outlet chamber or inlet chamber comprises a biological layer that provides biological degradation of pollutants.

Optionally, the biological layer comprises plant material planted in soil.

Optionally, a lower portion of any one or more the centre chamber, outlet chamber or inlet chamber comprises filtration media.

Optionally, an intermediate layer is provided between said upper and lower portions which comprises a second filtration media.

Optionally, the second filtration media comprises gravel or equivalent Optionally, the container is clad in brick or other material as a raised-bed garden feature.

Optionally, the inlet is for connection with a roof run-off downpipe.

Optionally the inlet is for connection with a sub-surface drain, and/or the device receives pluvial runoff in sheet flow as a surface-level inflow.

Optionally the outlet is for connection with a sewer or other drain, either directly or via another underground drain for onward connection to said sewer or other drain.

Optionally the outlet is for connection with a watercourse, either directly or via another underground drain for onward connection to said watercourse.

Optionally the outlet is for connection with a soakaway either directly or via another underground drain for onward connection to said soakaway.

The disclosure will now be described, byway of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of an example domestic house plot; Figure 2 illustrates a sustainable drainage device according to a first embodiment of the

disclosure;

Figure 3 illustrates a second embodiment of a sustainable drainage device according to the disclosure, being of a rainwater barrel form factor and having a "three chamber" design; Figure 4 illustrates a third embodiment of a sustainable drainage device according to the disclosure, being of a rainwater barrel form factor and having a "T-shaped partition member" design; Figure S illustrates a fourth embodiment of a sustainable drainage device according to the disclosure, being of a rainwater barrel form factor having a "three chamber" design and a tall narrow shape; Figure 6 illustrates a sustainable drainage device according to a fifth embodiment of the

disclosure, which comprises a rain garden;

Figure 7 illustrates a sixth embodiment ofa sustainable drainage device being of a rain garden form factor and having a "three chamber" design; Figure 8 illustrates a seventh embodiment of a sustainable drainage device being of a rain garden form factor and having a "T-shaped partition member" design; Figure 9 illustrates an eighth embodiment of a sustainable drainage device according to the disclosure, being of a rain garden form factor and showing a variation of the embodiment of figure 7; Figure 10 illustrates a sustainable drainage device according to a ninth embodiment of the

disclosure, which is for use in a driveway; and

Figure 11 illustrates a tenth embodiment of a sustainable drainage device according to the disclosure, being an alternative driveway sustainable drainage device.

The disclosure provides a sustainable drainage device that functions as a combined rainwater attenuation vessel and flow control device, in a single unit which has the potential to incorporate treatment media too. The unit is to be used at a houseplot or site of equivalent scale. The sustainable drainage device of the disclosure may provide a sustainable drainage system in a single container, or "SUDS in a box". A SUDS in a box device incorporates all three of flow control, attenuation, and water treatment Water treatment is any process that reduces the concentration of pollutants in the water. A number of mechanisms may provide water treatment, and in a SUDS these mechanisms are typically passive. For example, the use of filters or mesh screens will block the passage of large foreign objects in water. Filtration media may be also used to filter out pollutants such as suspended solids. Water can also be treated by passing it through soil or plant material to provide biological degradation of chemical pollutants. Water treatment can also be provided through sedimentation, so that pollutants sink to a sediment layer which is not passed through the device.

As used herein, "filtration media" may mean any media that provides a filtering function. For biodegradation and attachment of microflora, it is preferred that the material presents a high surface area to fluid flowing through the filtration media. Examples of filtration media include cellular units formed from plastic cellular units, gravel, and stone. it will be realised that this list is not exhaustive and many other materials may be used.

The sustainable drainage device of the disclosure may also in preferred embodiments provide features with an amenity value, including having an attractive appearance, being conducive to relaxation, good for wildlife, and so on.

The present disclosure provides attenuation effects that last for several hours, much longer than can be achieved with the use of a simple water storage volume by itself The present disclosure is concerned with the attenuation of pluvial run-off flows from a house plot, or a developed plot of similar scale. A typical house plot is shown in the schematic plan view of Figure 1, as a non-limiting example for the purposes of understanding the context of

the disclosure.

A house comprises a pitched roof 100, whose pluvial run-off is collected via guttering by rainwater pipes. Rodding eyes 102, 104 may also be provided. The roof run-off is channelled through a downpipe that is connected to a first sustainable drainage device 106, which is provided with a rainwater downpipe inlet 108. A drain outlet 110 of the sustainable drainage device 106 feeds into a surface water drain 112 and on to a filter drain 114 which is formed in a driveway 116 and which feeds into a driveway sustainable drainage device 118. An outlet 120 from the driveway sustainable drainage device 118 is connected to a surface water sewer 128 via surface water drain 122, disconnecting manhole 124 and surface water drain 126.

The plot may also be provided with a third sustainable drainage device 130 which comprises a rainwater downpipe inlet 132 and drain outlet 134 connected to surface water drain 136. As the third sustainable drainage device 130 is provided at the front of the plot, it maybe formed with a rain garden or clad with material to form a bench, as will be discussed below. The plot may also contain other outlets (not shown) for connection to a foul water sewer for the discharge of foul water such as toilet water and sink water that maybe contaminated with detergents and other chemicals. As well as the roof 100 and the driveway 116, the plot may comprise other impermeable surfaces such as (for example) a patio, paths, or roofs of other outbuildings such as garages, garden sheds, play houses.

Surface water run-off from a plot can be categorised as either being from roofs or from ground-level surfaces. Roof run-off is generally collected by guttering and down pipes.

Ground-level runoff is generally sheet flow that enters the buried form of the device either at ground-level, or via a filter drain or pipe connected to the device.

A sustainable drainage device according to the disclosure will have an inlet and an outlet, and a partition member which comprises a plurality of orifices arranged in a pattern for regulating the rate of flow between the inlet and the outlet. The container may be of any type that defines a volume for the storage of water either permanently or temporarily on an upstream side of the partition member, and so may comprise a covered or uncovered box-type container, or a portion or component part of a drainage or sewage system such as a manhole in which case the partition member could be provided as part of the manhole.

Figures 2-11 illustrate different example embodiments of sustainable drainage devices that comprise containers having a box-type form. Of these types, three main form factors are illustrated. The first form factor is a rainwater barrel [water butt), of which some example embodiments are shown in figures 2 to S. The second form factor is a rain garden, of which some example embodiments are shown in figures 6 to 9. The third form factor is a driveway unit, of which some example embodiments are shown in figures 10 and 11.

Figure 2 shows a first embodiment of a sustainable drainage device according to the disclosure, comprising a box type container and having a rainwater barrel form factor. This device is intended to be provided above ground, and can function as a water storage device (rainwater barrel) as well as a flow control device.

The top part of figure 2 shows a plan view of sustainable drainage device 201, which may for example be provided as sustainable drainage device 106 in Figure 1. The remaining parts of the figure show cross-sectional views A-A, B-B and C-C as indicated. A box structure 200 is provided with an internal partition member 202 which regulates the flow between an inlet 204 and an outlet 206. The inlet 204 is for connection with a rainwater downpipe and the outlet 206 is a drain outlet for connection with a surface water drain 208. Rodding eye 210 is also shown.

A lower portion of the partition member 202 does not comprise any orifices, and so this lower portion forms a boundary wall for a water storage volume, the remainder of the volume being bounded by an inlet portion of the device. The view A-A shows a volume 212 of water stored in this way. A garden water tap 214 can be provided for a user to access the stored volume 212. As can be seen in view A-A, a removable lid 216 may also be provided, and the box structure maybe mounted on support members 218 which may comprise blocks of brick, stone or other suitable material.

View B-B shows a rainwater downpipe 220 with swan neck inlet connected to the container inlet 204, and view C-C shows a pattern of orifices 224 provided in the partition member 202.

The partition member 202 is also provided with an overflow cut-out 226.

Figure 3 shows a second embodiment of a sustainable drainage device according to the disclosure, comprising a box type container and having a rainwater barrel form factor.

The top part of figure 3 shows a plan view of sustainable drainage device 301, which may for example be provided as sustainable drainage device 106 in Figure 1. The remaining parts of the figure show cross-sectional views A-A, B-B and C-C as indicated. A box structure 300 is provided with a first internal partition member 302 and a second internal partition member 304 which define three chambers within the box structure 300, namely an inlet chamber 306, an outlet chamber 308 and a centre chamber 310. Fluid enters the box structure 300 through an inlet 312 into the inlet chamber 306 and exits the box structure 300 through an outlet 314.

The inlet 312 is for connection with a rainwater downpipe and the outlet 314 is a drain outlet for connection with a surface water drain 208. Rodding eye 210 is also shown.

The inlet chamber 306 is optionally filled either partially or entirely with filtration media 316 that provides water quality treatment effect. The filtration media 316 may comprise filter media such as filled plastic mesh boxes, and may be removable for inspection, cleaning and removal of debris.

Although not illustrated in this embodiment filtration media may be provided in the outlet chamber 308 and/or the centre chamber 310 to provide a water quality treatment effect.

Flow between the inlet 312 and outlet 314 is attenuated, controlled and treated by a combination of the filtration media 316 in the inlet portion 306, a plurality of orifices in the first partition member 302 and a plurality of orifices in the second partition member 304.

The centre chamber acts as a temporary attenuation storage volume during a storm event.

A lower portion of each partition member 302, 304 is free of any orifices, and so these lower portions form a boundary wall for a water storage volume, the remainder of the volume being bounded by wall of the centre chamber 310. The viewA-A shows a volume 318 of water stored in this way. A garden water tap 320 can be provided for a user to access the stored volume 318. The box structure 300 may be mounted on support members 322 which may comprise blocks of brick1 stone or other suitable material.

The outlet 314 receives an outlet pipe 324 which may form or be coupled with a drain outlet for connection with a surface water drain 208. The box structure 300 is also provided with a removable lid 326.

The inlet chamber 306 is provided with a filter element 328 at the point where the in'et 312 is provided, in this case at an upper portion of the inlet portion 306. The filter element 328 prevents debris from entering the box 300 and may be removed for cleaning A liner 330 may be provided at the sides of the inlet chamber 306 which provides further filtering. It may be formed of a permeable geotextile material and may be removable for cleaning.

View B-B shows the second partition member 304 which forms the interface between the inlet chamber 306 and the centre chamber 310. This view also shows a rainwater downpipe 342 with swan neck inlet connected to the inlet chamber 306.

Flow from the inlet chamber 306 to the centre chamber is constrained to pass through a plurality of orifices 332 which are arranged in a predetermined pattern. In this case the pattern comprises a set of two orifices 332 at successive heights which are aligned in two vertical lines. However the disclosure is not limited to this pattern and the orifices in the pattern may be arranged with different numbers at different heights and/or with one or more different sizes.

An overflow aperture 334 is also provided so that fluid can flow from the inkt chamber 306 to the centre chamber 310 even if the rate of ingress through the inlet is large enough to exceed the flow rate allowed by the combined area of the orifices 332. An overflow warning outlet 336 such as a pipe may also be provided to provide a visual indication to a user that this overflow condition has occurred.

View C-C shows the first partition member 302 which forms the interface between the centre chamber 310 and the outlet chamber 308. Flow from the centre chamber 310 to the outlet chamber 308 is constrained to pass through a plurality of orifices 338 which are arranged in a predetermined pattern. In this case the pattern comprises a set of two orifices 338 at successive heights which are aligned in two vertical lines. However the disclosure is not limited to this pattern and the orifices in the pattern may be arranged with different numbers at different heights and/or with one or more different sizes.

An overflow aperture 340 is also provided so that fluid can flow from the centre chamber 310 to the outlet chamber 308 even if the rate of fluid flow into the centre chamber 310 is large enough to exceed the flow rate allowed by the combined area of the orifices 338. The overflow warning outlet 336 such as a pipe may also be provided to provide a visual indication to a user that this overflow condition has occurred.

The box structure 300 is a single container that provides multiple functions) namely? water quality treatment provided by the filtration media in the inlet chamber and/or outlet chamber; flow control provided by the orifices in the first internal partition member 302; attenuation provided by the water storage of the centre chamber 310; and flow control provided by the orifices in the second internal partition member 304.

The "three chamber" design illustrated in figure 3 may apply generally to a sustainable drainage device of any form factor, including without limitation the rainwater barrel type shown here, or to a rain garden or driveway form factor as described elsewhere.

Figure 4 shows a third embodiment of a sustainable drainage device 401 according to the disclosure, comprising a box type container 400 and having a rainwater barrel form factor.

The top part of figure 4 shows a plan view of sustainable drainage device 401, which may for example be provided as sustainable drainage device 106 in Figure 1. The remaining parts of the figure show cross-sectional views A-A? B-B and C-C as indicated.

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In this embodiment, the box structure 400 is provided with a transverse partition member 402 that spans its transverse plane and defines at one side a storage chamber 410. A longitudinal partition member 404 is provided at the other side of the transverse partition member 402 and substantially spans a longitudinal plane of the box structure 401 to define an inlet chamber 406 at one side and an outlet chamber 408 at the other. The partition members 402, 404 may be integrally formed together as a one-piece construction; or they maybe manufactured separately and affixed together during assembly of the box structure 400.

The transverse partition member 402 comprises one or more orifices at a first portion that is aligned with the inlet chamber 406 and one or more orifices at a second portion that is aligned with the outlet chamber 408. Fluid enters the box structure 400 through an inlet 412 into the inlet chamber 406. It then flows through the orifices in the first portion of the transverse partition member 402 to enter the storage chamber 410. At this point the inlet chamber 406 will have a larger volume of water stored in it as compared to the outlet chamber 408 due to the continuing inflow of fluid via the inlet 412 and so as the storage chamber 410 fills, fluid will then enter the outlet chamber 408 and exit via the outlet 414.

The inlet 412 is for connection with a rainwater downpipe and the outlet 414 is a drain outlet for connection with a surface water drain 208. Rodding eye 210 is also shown.

In this embodiment, both the inlet chamber 406 and outlet chamber 408 are filled either partially or entirely with filtration media 416 that provides a water quality treatment effect.

The filtration media 416 may comprise filter media such as filled plastic mesh boxes, and may be removable for inspection, cleaning and removal of debris. It is possible for filtration media to be provided in none, one, any two or all of the inlet chamber 406, outlet chamber 408 and centre chamber 410.

A lower portion of the transverse partition member 402 is free of any orifices, and so this lower portion forms a boundary wall for a water storage volume, the remainder of the volume being bounded by wall of the storage chamber 410 and inlet chamber 406. The view A-A shows a volume 418 of water stored in this way. A garden water tap 420 can be provided for a user to access the stored volume 418. The box structure 400 may be mounted on support members 422 which may comprise blocks of brick, stone or other suitable material.

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The outlet 414 receives an outlet pipe 424 which may form or be coupled with a drain outlet for connection with a surface water drain 208. The box structure 400 is also provided with a removable lid 426.

The inlet chamber 406 is provided with a filter element 428 at the point where the inlet 412 is provided, in this case at an upper portion of the inlet portion 406. The removable filter element 428 prevents debris from entering the box 400 and may be removed for cleaning. A liner 430 may be provided at the sides of the inlet chamber 406 which provides further filtering. It may be formed of a permeable geotextile material and may be removable for cleaning.

View B-B shows the face of the transverse partition member 402 and the edge of the longitudinal partition member 404. A plurality of orifices 432 are formed in a first portion of the transverse partition member 402 aligned with the inlet chamber 406 and a plurality of orifices 434 are formed in a second portion of the transverse partition member 402 aligned with the outlet chamber 408. In this embodiment, a similar number of orifices are arranged in a similar pattern on both the first and second portions of the transverse partition member 402 but it will be appreciated that the number and/or pattern of the orifices could be different from that which is illustrated and may also be different for the different portions in order to provide a desired flow control effect.

Overflow apertures 436, 438 are provided at the inlet chamber 406 and outlet chamber 408 respectively so that fluid can flow between the inlet/outlet chambers and through the centre chamber 410 even if the rate of fluid flow exceeds a flow rate allowed by the combined area of either of the orifices 432, 434. An overflow warning outlet 444 such as a pipe may also be provided to provide a visual indication to a user that this overflow condition has occurred.

This view also shows a rainwater downpipe 442 with swan neck inlet connected to the inlet chamber 406.

The box structure 400 is a single container that provides multiple functions, namely, water quality treatment provided by the filtration media in the inlet chamber and/or outlet chamber; flow control provided by the orifices in the first and second portions of the b transverse partition member 402; and attenuation provided by the water storage of the centre chamber 410.

The "T-shaped partition member" design illustrated in figure 4 also provides three chambers (inlet, storage and outlet] may apply to sustainable drainage devices of various form factors, including without limitation the rainwater barrel type shown here, or to rain garden or driveway unit form factors as described elsewhere.

The adjacent inlet and outlets of the "T-shaped partition member" design means that a unit according to this design can be retrofitted more easily. It is also easier to maintain, as a single access point such as a manhole cover or similar can be provided for accessing both inlet and outlet chambers for cleaning and maintenance.

Figure 5 shows a fourth embodiment of a sustainable drainage device 501 according to the disclosure, comprising a box type container and having a rainwater barrel form factor.

In this embodiment, the shape of the box structure 500 is relatively tall and narrow compared to the relatively short and wide box structure 300 of the embodiment of figure 3. Asides from that, this embodiment has similarities to that illustrated in figure 3 so common reference numerals are used to illustrate common features.

Figure 6 shows a fifth embodiment of a sustainable drainage device according to the disclosure, comprising a box type container and having a rain garden form factor. This device is intended to be provided wholly or partially below ground. The top part of figure 6 shows a plan view of sustainable drainage device 601 which may for example be provided as a sustainable drainage device 130 in figure 1. The remaining parts of the figure show cross-sectional views A-A and B-B as indicated. A box structure 600 is provided with an internal partition member 602 which regulates the flow between an inlet 604 and an outlet 606. The inlet 604 is for connection with a rainwater downpipe and the outlet 606 is a drain outlet for connection with a surface water drain 608. Rodding eye 610 is also shown.

As seen in view A-A, the box structure 600 contains various elements, comprising a substrate infill layer 612 which may comprise modular plastic voided media; an intermediate infill layer 614 that may comprise a gravel infill, and an upper layer 616 which may comprise topsoil. A geotextile membrane 618 is interposed between the upper layer 616 and the intermediate infill layer 614. It will be appreciated that the box structure 600 maybe filled with different types of material and comprise different numbers of layers [less layers or more layers than the embodiment illustrated). However the common principle is that the contents will provide a permeable structure for the drainage of rainfall.

The rain garden style sustainable drainage device 601 may be partially formed below ground lev& 619, and may be provided with a protective brick surround 620. The box structure 600 may be provided adjacent to a house wall structure 622.

View B-B shows the partition member 602 provided with a pattern of orifices 624 which provide flow control. in this embodiment, the orifices are provided at a bottom portion of the partition member 602, so that there is no separate water storage volume. The drainage attenuation aspect of the device according to this embodiment is provided by the water retention of the various media contained in the box structure; and the partition member regulates the flow that egresses via the outlet 606. The partition member 602 is also provided with an overflow cut-out 626.

Figure 7 shows a sixth embodiment of a sustainable drainage device 701 according to the disclosure, comprising a box type container 700 and having a rain garden form factor. This device is intended to be provided wholly or partially b&ow ground. The top part of figure 7 shows a plan view of sustainable drainage device 701 which may for example be provided as a sustainable drainage device 130 in figure 1. The remaining parts of the figure show cross-sectional views A-A and B-B as indicated.

A box structure 700 is provided with a first internal partition member 702 and a second interna' partition member 704 which define three chambers within the box structure 700, namely an inlet chamber 706, an outlet chamber 708 and a centre chamber 710. Fluid enters the box structure 700 through an inlet 712 into the inlet chamber 706 and exits the box structure 700 through an outlet 714. The inlet 712 is for connection with a fluid conduit such as a rainwater downpipe 760 and the outlet 714 is a drain outlet for connection with a drain 136. Rodding eye 102 is also shown.

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in this embodiment, both the inlet chamber 706 and the centre chamber 710 are filled partially or entirely with filtration media 716, 718 that provides a water quality treatment effect. The filtration media 716, 718 may comprise filter media such as filled plastic mesh boxes, and may be removable for inspection, cleaning and removal of debris. Filtration media may also be provided in the outlet chamber 708, and generally could be provided in any one or more of the chambers 706, 708, 710. Different filtration media may be provided for different chambers of the box structure.

The first internal partition member 702 comprises a plurality of orifices 332 as shown in view B-B and the second internal partition member 704 comprises a plurality of orifices 338 as shown in view C-C. These orifices 332, 338 control the flow of fluid in a similar way to the corresponding orifices in the "three chamber" design of figure 3.

Irrigation of plant material is ensured by the provision of a manifold member 750 which is in fluid communication with the inlet 712 or with a fluid conduit which is received by the inlet.

The manifold member 750 comprises a plurality of fluid outlets at different positions along the side of the box structure 700. The fluid outlets are positioned so that fluid flows directly into the centre chamber 710. The manifold member may comprise a pipe with perforations providing the fluid outlets, and in a preferred embodiment may be affixed to a rain water pipe via a shoe connector.

In this embodiment the manifold member 750 is placed on an upper surface of the centre chamber 310 but it may be placed at any chosen height within the centre chamber, with appropriate connectors being provided from the inlet or fluid conduit received by the inlet.

The inlet size of the shoe connector defines the amount of fluid that is diverted from the inlet or fluid conduit and can be chosen according to requirements. The manifold member may also provide fluid outlets at a plurality of different heights. This may be achieved by providing a planar manifold member with perforations at various points in the plane) or by having a grid or other arrangement or pipes with perforations.

A control mechanism may also be provided to selectively connect or disconnect the manifold member 750 [for example by closing or opening a shutter), and/or to selectively open or close one or more of the fluid conduits, in order to change the permitted fluid flow rate.

As seen in view B-B, a lower portion of the box structure may be provided with filtration media 718. An upper portion maybe filled with a biological layer 720. This biological layer can comprises any material that provides a biological degradation of pollutants. It may comprise plant matter planted in soil, the plant matter comprising for example flowers, herbs, grass or shrubs. Soil may also in itself provide a biological degradation function) even without plant matter being provided. The biological layer 720 may be be lined with a fine mesh geogrid fabric 722 in order to form a plant bed. As an alternative to soil, a different material may be chosen to fill the biologica' layer 720 depending on aesthetic or practica' requirements, such as gravel, stones or other material.

The biological layer 720 may be provided in an upper portion of any one or more of the centre chamber 710, outlet chamber 708 or inlet chamber 706. Similarly, the filtration media may be provided in a lower portion of any one or more of the centre chamber 710, outlet chamber 708 or inlet chamber 706 The rain garden style sustainable drainage device 701 may be partially formed below ground leve.l 719, and may be provided with a protective brick surround 724. The box structure 700 may be provided adjacent to a house wall structure 726. Overflow apertures 728, 730 are provided on each of the partition members 702, 704 which function as described elsewhere in

the disclosure.

As seen in view A-A, the inlet chamber 706 is provided with a filter element 732 at the point where the inlet 712 is provided, in this case atan upper portion of the inlet portion 706. The filter element 732 prevents debris from entering the box 700 and may be removed for cleaning.

The manifold member design illustrated in figure 7 may apply generally to any sustainable drainage device that has a rain garden form factor, that is, any which includes a biological layer.

Figure 8 shows a seventh embodiment of a sustainable drainage device 801 according to the disclosure, comprising a box type container and having a rain garden form factor. The top part of figure 8 shows a plan view of sustainable drainage device 801, which may for example be provided as sustainable drainage device 130 in Figure 1. The remaining parts of the figure show cross-sectional views A-A, B-B and C-C as indicated.

This embodiment comprises a "T-shaped partition member" design similar to that illustrated in figure 4. Here, the box structure 800 is provided with a transverse partition member 802 that spans its transverse plane and defines at one side a storage chamber 810. A longitudinal partition member 804 is provided at the other side of the transverse partition member 802 and substantially spans a longitudinal plane of the box structure 801 to define an inlet chamber 806 at one side and an outlet chamber 808 at the other.

View B-B shows the face of the transverse partition member 802. A plurality of orifices 832 are formed in a first portion of the transverse partition member 802 aligned with the inlet chamber 806 and a plurality of orifices 834 are formed in a second portion of the transverse partition member 802 aligned with the outlet chamber 808.

Overflow apertures 836, 838 are provided at the inlet chamber 806 and outlet chamber 808 respectively so that fluid can flow between the inlet/outlet chambers and the centre chamber 810 even if the rate of fluid flow exceeds a flow rate allowed by the combined area of the orifices 832, 834.

The partition members, orifices and infill elements attenuate and control flow as described above with respect to figure 4, so detailed description of this will not be repeated. However in this embodiment irrigation of an upper portion of the rain garden is enhanced by the addition of the manifold member 750. The sustainable drainage device 801 is provided with other features similar to those described with reference to figure 7, so like reference numerals have been used to illustrate like features.

Figure 9 shows an eighth embodiment of a sustainable drainage device according to the disclosure, comprising a box type container and having a rain garden form factor.

This embodiment corresponds to the "three chamber" design of figure 7 exceptthatan additional intermediate layer is provided within the central chamber 910 as compared with the central chamber 710 of figure 7. Here, the central chamber 910 comprises a first lower layer 970 of filtration media such as plastic cellular units, a second intermediate layer 972 of another filtration media, and an upper biological layer 974. Baffle plates with overflow apertures 928, 930 provide for excess flow between the centra' chamber 910 and in'et/outlet chambers 706, 708 as described above.

The second intermediate layer 972 may in a preferred embodiment comprise gravel of equivalent. A geogrid fabric liner 976 may be provided to separate the intermediate layer from the filtration media. The intermediate layer provides additional space (as compared with the embodiment of figure 7] for roots of plants to grow into without damaging the underlying structure of the container. The gravel or equivalent of the intermediate layer can be replaced easily for removal of roots if the rain garden is to be re-planted.

The partition members, orifices and infill elements attenuate and control flow as described above with respect to figure 7,so detailed description of this will not be repeated. However in this embodiment the control of fluid flow is augmented by the addition of the intermediate layer 972. The sustainable drainage device 801 is provided with other features similar to those described with reference to figure 7, so like reference numerals have been used to illustrate like features.

Figure 10 shows a ninth embodiment of a sustainable drainage device according to the disclosure comprising a box type container being configured as a driveway sustainable drainage device, and which may for example be provided as a drainage and attenuation device 118 in Figure 1. The top part of figure 10 shows a plan view of sustainable drainage device 1001. The remaining parts of the figure show cross-sectional views A-A, B-B and C-C as indicated. A box structure 1000 is provided with an internal partition member 1002 which regulates the flow egress through an outlet 1006 which is a drain outlet for connection with a surface water drain 1008.

Here, the device 118 is arranged to receive pluvial runoff in sheet flow as a surface-level inflow through an upper surface of the device, and/or as sub-surface flow through an end and/or side surface of the device. As shown in view A-A, the device is adjacent to and level with a gravel topped filter drain with granular filter material. Box structure 1000 contains infill media 1010 which here comprises a modular plastic voided infill medium, topped with an upper layer 1012 which here comprises gravel. A permeable geotextile membrane 1014 is interposed between the gravel 1012 and the infill layer 1010. An impermeable liner 1016 is provided that surrounds the downstream end, the base and the two sides of the box structure 1000 and continues upstream to encapsulate the base) both sides and the upstream end of the adjacent gravel topped filter drain. However an upstream end of the box is lined with a permeable geotextile membrane 1018, which may be an extension of the upper membrane 1014 or a separate element.

As seen in view B-B, an upstream end of the box structure 1000 is provided with an end panel 1020 which comprises orifices 1022. The end panel 1020 is clad with a permeable geotextile membrane so the orifices 1022 permit the ingress of sub-surface water flow into the box structure 1000. The base and side panels are clad with the continuous impermeable liner 1016 so that subsurface water flow within the adjacent filter drain is contained and does enter the box structure 1000 through the permeable geotextile membrane 1018 and the end panel orifices 1022. The gravel layer 1012 forms a ground level surface between driveway paving slabs 1024.

As seen in view C-C, the partition member 1002 is provided with orifices 1026 which provide flow control. in this embodiment, the orifices 1026 are provided at a bottom portion of the partition member 1002, so that there is no separate water storage volume (although this may be provided in a driveway device according to an alternative embodiment). The drainage attenuation aspect of the device according to this embodiment is provided by the water retention of the various media contained in the box structure 1000; and the partition member 1002 regulates the flow that egresses via the outlet 1006. The partition member 1002 is also provided with an overflow cut-out 1028. Drainage attenuation may also be provided by additional upstream storage components.

A driveway may also be provided with multiple box structures 1000, which may be combined in a modular fashion.

In a driveway, pluvial run off will be expected to run from an upstream direction to a downstream direction under the influence of gravity and governed by the geography of the plot. A driveway defines a longitudinal channel and so when the longitudinal axis of the driveway is in line with the prevailing runoff direction, a permealile end panel is provided and the other surfaces of the box structure are made impermeable. However if the box structure was placed in a different orientation with respect to the prevailing runoff direction, different panels of the structure could be made permeable or impermeable to fit with the prevailing runoff direction.

Figure 11 shows a tenth embodiment of a sustainable drainage device 1101 according to the disclosure, comprising a box type container 1100 and being configured as a driveway sustainable drainage device, and which may for example be provided as a drainage and attenuation device 118 in Figure 1. The top part of figure 11 shows a plan view of sustainable drainage device 1101. The remaining parts of the figure show cross-sectional views A-A, B-B and C-C as indicated.

This embodiment incorporates the "three chamber" design first seen in figure 4. The box structure 1100 is provided with a first internal partition member 1102 and a second internal partition member 1104 which define three chambers within the box structure 1100, namely an inlet chamber 1106, an outlet chamber 1108 and a centre chamber 1110. Fluid enters the box structure 1100 through an inlet 1112 into the inlet chamber 1106 and exits the box structure 1100 through an outlet 1114. The in'et 1112 may receive a fluid conduit such as a pipe 1120. In a preferred embodiment a perforated pipe 1118 is provided.

In the embodiment of figure 11, both the inlet chamber 1106 and the centre chamber 1110 are filled partially or entirely with filtration media 1116, 1118 that provides an attenuation effect. The filtration media 1116, 1118 may comprise filter media such as filled plastic mesh boxes. Filtration media may also be provided in the outlet chamber 708, and generally could be provided in any one or more of the chambers 706, 708, 710. Different filtration media may be provided for different chambers of the box structure. An impermeable liner 1116 is provided at bottom and side surfaces of the box structure 1100.

The first internal partition member 1102 comprises a plurality of orifices 1132 as shown in view B-B and the second internal partition member 1104 comprises a plurality of orifices 1138 as shown in view C-C. These orifices 1132, 1138 control the flow of fluid in a similar way to the corresponding orifices in the "three chamber" design of figure 3.

Overflow apertures 1128, 1130 are provided on each of the partition members 1102, 1104 which function as described elsewhere in the disclosure. An overflow pipe 1122 feeds fluid back out of the box structure 1100 at an upstream side in the event of an overflow condition.

In this embodimentthe box structure comprises a first layer with filtration media 1116, 1118 such as plastic cellular units and a second layer with filtration media 1140 such as gravel or stones. A liner 1142 of fine mesh geogrid fabric or equivalent may be provided between the infill and filtration media layers. In this embodiment, the layers are provided across both the inlet chamber 1106 and centre chamber 1110. The layer of filtration media comprises first filtration media in the in'et chamber 1106 and second filtration media in the centre chamber 1110. It is to be appreciated that the layers of filtration media and filtration material may be provided generally across any one or more of the chambers, or alternatively the chambers could all be empty. Mso it will be appreciated that additional layers could be added as required.

The box structure 1100 sits beneath a driveway 1160, and may comprise an upper gravel surface 1162 which sits between paving slabs 1164 of a driveway. Alternatively, the box structure 1100 may sit beneath a grass lawn and receive run-off from a driveway or other impermeable surface such as a patio or path.

The partition members of the disclosure [including the embodiments illustrated above and other embodiments) are provided with a plurality of orifices, which for example may comprise a plurality of small orifices. The orifices may be of any size necessary to limit the pass-forward flow to a specification required for a particular size of house plot, but as an example only may be 4mm in diameter.

The embodiments mentioned above show generally circular orifices, but it will be appreciated that the partition member's orifices can be of any shape and of varying sizes, subject to the requirement to limit flow to a pre-determined attenuation performance.

A plurailty of orifices are provided at different discrete heights of the partition member.

Additionally it is possible to provide multiple and/or larger area orifices for one or more of each of the different heights.

An additional opening, at the top of the partition member, is different in size and function from the pattern of orifices noted above. it serves as a high leve.l overflow, and may be provided for all embodiments.

Having orifices that provide openings at different heights (in discrete steps) enables the attenuation of the fluid flow that is discharged from the device's outlet during a storm event to have a pattern that more closely mimics a green field (pre-development) state. it allows achievement of green-field runoff rate if correctly sized and specified.

Note that the term "orifices" does not impute any restriction on how they are formed -they may not have to be cut but could be punched, drilled, formed during a moulding process, or formed in any other way.

The partition members may be formed integrally with the rest of the container. The provision of planar partition members, whether formed integrally or not, provides structural strength ti the unit The partition member that defines the outlet portion of the container (or outlet chamber] can be provided at a relatively short distance from the outlet portion of the container, as the outlet portion is only needed for the outflow from the vessel, and not for storage of water.

In various embodiments, the sustainable drainage device may be provided with an integral water storage volume for the permanent storage of water (an example embodiment of this is shown in figure 2). To enable this, a lower portion of the partition member does not comprise any orifices, and so this lower portion forms a boundary wall for a water storage volume, the remainder of the volume being bounded by an inlet portion of the device. In this embodiment when water flows through the inlet, the storage volume fills first, and after that point the inlet portion will start to fill beyond the level of the storage volume and will permit flow into the outlet portion as described above.

The box volume may be sized so as to provide a storage volume sufficient to attenuate a range of storm events from very small to very large, in relation to a specified plot area (for example from a roof or car parking bays) or drainage from a driveway and roof area]. Each version or model of the device can therefore be sized according to a specified source area, expressed as a range of areas in m2.

An integral outlet connection may be provided on a bottom surface of the outlet portion, for coupling with a pipe or similar.

The box of the embodiments shown in the figures is relatively short and wide. However? different form factors may be adopted. The box may be relatively tall and narrow compared to the embodiments illustrated. It may have an inlet, outlet and partition member which function in a similar fashion to those illustrated.

The drainage attenuation device of the disclosure attenuates rainfail run-off from a house plot or similar scale area, to discharge run-off from the plot at or close to green field (pre-development] rates, on a plot by plot basis. Different sized versions of the device may be produced to accommodate the flow from differing plot areas according to the various sizes of 23 property to be served by the device. For example, a first device size could cater for a terraced house, a second larger device size for a semi-detached house and a still larger size for a larger detached property. it is also possible to provide multiple devices, of one or more sizes, to accommodate different or arger plot areas.

Optionally, two driveway units in series could be provided for attenuation of pluvial runoff delivered from conventional drainage without the use of other units at each roof downpipe.

The disclosure provides for the encapsulation of the diverse features of flow control, water quality and amenity value, which are the basic characteristics of SUDS technology into a single integrated box unit that can be applied at a scale of a single house or business unit, or in car parking.

In selected embodiments, the drainage attenuation device functions both as a water storage tank and as a flow rate controller. These functions, taken together, serve to attenuate pluvial run-off flow. Surface water run-off enters at the inlet and a small, restricted outflow is permitted by the orifices in the partition member, throughout the rainfall storm event Nonetheless, the rate of inflow peaks at a value in excess of the permitted discharge rate, causing the water level in the vessel to rise to gradually fill the storage volume. As inflow increases, the outflow also increases as more orifices come into play, until for exceptionally large storm events the high level overflow may come into operation. But the restricted flow permitted by the pattern of orifices in the partition member delays the peak discharge) and the storage volume attenuates the inflow sufficiently to greatly reduce the average rate of discharge.

In these embodiments, the inlet portion can be provided with a further outlet, with discharge being controlled with a valve, such as a tap. Then the stored water can be accessed for use by the home owner.

The device of the disclosure can be used to collect roof run-off, in which case the fluid inlet will be connected to a rainwater downpipe or similar. The device may also be used to collect ground-level run-off, in which case the fluid inlet will be connected to rainwater collection points or pipes that collect rainwater from ground-level features. It is also possible in an alternative embodiment to provide a fluid inlet connection for connection to both roof and ground-level run-off In that scenario, two [or more) fluid inlets could be provided, or the relevant collection points could be combined into a single pipe for connection to a single fluid inlet.

The outlet can be coupled with a discharge pipe for connection with a sewer system, or alternatively to a surface water drain rather than directly to a sewer system. Where a houseplot or other area is sub-divided, for example into each half of a roof, and a driveway, then each surface maybe drained to a device as disclosed here, and the final connection being to a driveway version of the device for connection to a sewer for example. Alternatively, only one sub-area (e.g. roof) may so be drained, with other sub-divisions being connected to alternative intermediate components. Within a plot, one or more sustainable drainage devices according to any embodiment of this disclosure could be used in conjunction with other SUDS devices such as detention basins or underground reservoirs.

As mentioned above, it is also possible to provide multiple sustainable drainage devices according to the disclosure in a single plot. Figure 1 shows an example layout that comprises three devices, comprising a "standard" device as shown in figure 2, a rain garden device as shown in figure 3 and a driveway device as shown in figure 4. However, the plot could be provided with more or less of each of these types of devices and devices of alternative embodiments as desired.

Access (for example for maintenance) to the inside of the device and the partition member, may be provided by a suitable lid. More than one lid may be provided, for example, one to access the inlet portion and one to access the outlet portion and the partition member. The fluid inlet may be an integral moulded portion, similar to the fluid outlet, for the connection of a pipe. The lids may be designed such that they can be opened and closed after the connection ofa pipe.

When fitted as the final feature on a house plot the device will give a controlled discharge reaching a maximum rate that can be used by flood risk managers to assess the acceptability of development in a constrained or otherwise at risk of flooding catchment. The device will also provide water utilities and local authorities with a novel, innovative, and relatively simple and inexpensive, retrofit option to address pluvial flooding issues in existing developments, for a variety of situations.

The device has no moving parts and no pipes except the connections for the inlet and outlet pipes. This makes it relatively straightforward to manufacture. in addition, because the flow control is provided by a partition member which can be planar, the manufacturing process is further simplified and the overall device has a robust form factor.

This device puts the flow attenuation volume required for a single property into a single box.

The box can be an above ground feature that, when protected by wood slats for example can also serve as a bench seat or table, or with the lid removed and a geotextile permeable membrane and filter media installed and the top layer planted, it can be a rain garden. Equally it could be filled with stone or other media and buried in a driveway as a final flow control feature. It is sustainable drainage technology in a box.

The partition member with orifices thus eliminates the need for an alternative flow control mechanism such as a ballcock valve or a vortex flow control on the unit. Use of the novel partition member allows a robust vessel to be constructed, at reduced cost, facilitating therefore the application of the idea at minimum cost for resolving sewer and urban stream flooding problems.

In addition, wrong connections of foul drainage from toilets, sinks and showers into surface water sewers is a chronic and serious pollution problem that is widespread in towns and cities where a separate sewer system is provided. The drainage attenuation device of this disclosure provides a way for householders to become immediately aware of wrongly connected drainage within their property, since it would result in a vessel full of sewage (once it had blocked the partition member cut-outs) which would smell and therefore be noticed.

Consequently the problem would be immediately obvious and be resolved by the householder, and not at public expense.

Furthermore, retrofit measures at a houseplot for reducing flood risk in urban areas need to provide benefits for the householder, as well as for the population living on the catchment of the sewer that has flooding problems. Cladding the device's container with an attractive timber framework would provide householders with a garden seat feature, whilst at the same time providing the water utility or local authority with a unit that is part of a wider at source set of measures to combat the flooding problem. Alternatively the box cover could be a place for plant pots or other garden features.

Also, for new build situations the box can provide developers with a modular rain garden option to both attenuate roof runoff flow, and also provide an attractive garden feature for the householders. This provides a drainage option that is consistent with place making concepts of multiple benefits.

For new build situations the box can provide developers with a modular driveway or car park area flow and pollutant attenuation feature for the householders; a stand-alone house plot SUDS feature.

Optionally, an embodiment of the device may be used as a flow control in an industrial process where fluids require to be passed forward in a controlled rate within a process.

Various improvements and modifications can be made to the above without departing from

the scope of the disclosure.

The box structure may be divided into more than three different chambers. For example, the centre chamber is further sub-divided into sub-units. The three chamber" design has two partition members but if the box structure may be divided into more than three different chambers there may be a plurality of partition members with orifices.

The disclosure is not limited to a device of any specific size, but as an illustration the devices of each form factor may have length width and depth dimensions of between 0.5 and 2 meters, with box type structures having generally rectangular forms, that is with a length greater than their width or vice versa.

The horizontal layers shown in the figure are for illustration only and it will be appreciated that different numbers of layers may be provided which may be filled with or comprise different materials or mixtures of materials to provide attenuation and other effects.

Claims

CLAIMS1. A sustainable drainage device comprising a container that provides both flow control and flow attenuation; and wherein the container comprises a first internal partition member and a second internal partition member which define an inlet chamber, an outlet chamber and a centre chamber; and said first and second partition members each comprise a plurality of orifices for regulating the rate of flow between the chambers.
2. The sustainable drainage device of claim 1, being provided in a driveway.
3. The sustainable drainage device of claim 1 or claim 2, wherein the container is sized for a domestic house plot or plot of similar scale.
4. The sustainable drainage device of any preceding claim, wherein multiple containers are provided in a driveway and are combined in a modular fashion.
5. The sustainable drainage device of any preceding claim, wherein the inlet chamber is filled either partially or entirely with filtration media.
6. The sustainable drainage device of claim 5, wherein the filtration media comprise components that can be removed for cleaning or maintenance.
7. The sustainable drainage device of claim S or claim 6, wherein an inner surface of a chamber comprising filtration media is lined with a permeable liner.
8. The sustainable drainage device of any preceding claim, wherein the inlet chamber is provided with a filter element at the point where the inlet is provided.
9. The sustainable drainage device of any preceding claim, wherein the orifices comprise openings in the partition member at different heights.
10. The sustainable drainage device of claim 9, wherein the openings provide progressively greater discharge areas at greater heights.
11. The sustainable drainage device of any preceding claim, wherein the orifices comprise circular apertures.
12. The sustainable drainage device of any preceding claim, wherein the partition members are planar.
13. The sustainable drainage device of any preceding claim, wherein one or more of the partition members are formed integrally with the container.
14. The sustainable drainage device of any preceding claim, wherein one or more of the partition members is a removable or changeable feature of the container.
15. The sustainable drainage device of any preceding claim, wherein the device comprises a manifold member in fluid communication with the inlet or with a fluid conduit which is received by the inleL
16. The sustainable drainage device of claim 15, wherein the manifold member comprises a plurality of fluid outlets at different positions along the side of the container.
17. The sustainable drainage device of claim 15 or claim 16, wherein the manifold member comprises a pipe with perforations providing the fluid outlets.
18. The sustainable drainage device of claim 1, wherein the container is clad with timber, plastic or any other suitable material, to form a garden bench or table.
19. The sustainable drainage device of claim 18, wherein the container is filled or part-filled with media forming a filtration and attenuation unit or rain garden.
20. The sustainable drainage device of claim 18 or claim 19, wherein an upper portion of any one or more the centre chamber, outlet chamber or inlet chamber comprises a biological layer that provides biological degradation of pollutants.
21. The sustainable drainage device of claim 20, wherein the biological layer comprises plant material planted in soil.
22. The sustainable drainage device of any preceding claim, wherein a lower portion of any one or more the centre chamber, outlet chamber or inlet chamber comprises filtration media.
23. The sustainable drainage device of claim 22, wherein an intermediate layer is provided between said upper and lower portions which comprises a second filtration media.
24. The sustainable drainage device of any claim 23, wherein the second filtration media comprises gravel or equivalent.
25. The sustainable drainage device of claim 1, wherein the container is clad in brick or other material as a raised-bed garden feature.
26. The sustainable drainage device of any preceding claim, wherein the inlet is for connection with a roof run-off downpipe.
27. The sustainable drainage device of any of claims ito 25, wherein the inlet is for connection with a sub-surface drain, and/or the device receives pluvial runoff in sheet flow as a surface-level inflow.
28. The sustainable drainage device of any preceding claim, wherein the outlet is for connection with a sewer or other drain, either directly or via another underground drain for onward connection to said sewer or other drain.
29. The sustainable drainage device of any of claims ito 27, wherein the outlet is for connection with a watercourse, either directly or via another underground drain for onward connection to said watercourse.
30. The sustainable drainage device of any of claims ito 27, wherein the outlet is for connection with a soakaway, either directly or via another underground drain for onward connection to said soakaway.
31. The sustainable drainage device of any preceding claim, wherein the centre chamber is further sub-divided into sub-units.
32. The sustainable drainage device of any preceding claim, wherein the sustainable drainage device comprises a storage volume which stores fluid such that it is isolated from the fluid outlet.
33. The sustainable drainage device of any preceding claim, wherein the container is provided with a removable lid.