GB2489455A - A drainage system for a tree pit - Google Patents

Abstract

The present invention relates to a drainage system for a tree pit, preferably an urban tree pit. The system comprises a trough 10 for receiving falling water, rainwater or surface run-off, wherein the trough has a sump (10 figure 7) having at least one trap (12 figure 8). The trap comprises a water inlet for receiving water from the trough and a water outlet for discharging water from the trough. The drainage system may be made from high-density polyethylene (HDPE) A later embodiment relates to a tree pit drainage system kit comprising a trough having a sump section with at least one trap.

Description

A Drainage System The present invention relates to a drainage system, and particularly to a drainage system for a tree pit. More particularly, the present invention relates to a drainage system for an urban tree pit.

The benefits of urban tree planting have been well reported. The benefits include traffic calming, storm water management, improved air quality, community cohesion and carbon reduction. Urban frees are also thought to have a positive impact on the incidence of skin cancer and asthma amongst city-dwellers. Urban trees can also provide a number of psychological benefits.

Incorporation of a drainage system is an essential part of urban tree pit design. A water logged tree pit will generate anaerobic conditions, which can result in tree death. In an urban setting, where space is limited, there are particular challenges in developing an effective free pit drainage system.

Traditional drainage systems for surface water run-off convey rainwater, as rapidly as possible, from where it has fallen to either a soak-away or a watercourse. As a consequence of increased densities of new building developments and increased levels of urbanisation, this traditional method of surface water drainage is becoming less practical and less effective. The method also fails to reduce the risk of flooding, environmental damage and urban diffuse pollution, since mn-off water usually carries contaminants including oils, heavy metals, pesticides, fertilisers, chemicals and other organic matter.

Increasingly, authorities and organisations require a sustainable approach to drainage.

Certain authorities require the incorporation of a sustainable drainage system (SUDS) proposal into planning applications and design submissions. Regulations for new buildings have also been modified to infroduce a SUDS protocol, establishing it as part of best practice.

It is an aim of the present invention to provide a SUDS tree pit system that effectively reduces the flow rate of surface water mn-off in urban areas.

In its broadest aspect, the present invention provides a drainage system for a tree pit, the system comprising at least one trough, wherein the trough comprises at least one trap.

In a preferred embodiment, an outlet of at least one trap is connectable to an aeration manifold, preferably a perforated pipe, for distributing water within the tree pit.

Ideally, the system further comprises a discharge pipe for transferring water from the aeration manifold to the subsoil or to a flow control chamber.

According to the present invention there is provided a drainage system for a tree pit, the system comprising a trough for receiving falling water, rainwater or surface run-off wherein the trough comprises a sump having at least one trap, the trap comprising a water inlet for receiving water from the trough and a water outlet for discharging water from the trough.

In a preferred embodiment, the system further comprises a drainage channel, engageable with the trough, the drainage channel being suitable for receiving falling water, rainwater or surface mn-off Suitably, the drainage channel comprises apertures dimensioned to retain silt and organic matter, such as leaves, and to allow passage of water, in use of the system.

In one embodiment, the drainage system further comprises a root director.

Preferably, the drainage system comprises four troughs, one trough being positionable at each side of the root director.

Preferably, the system comprises a conduit pipe engageable with the drainage channel and the trough, for feeding water from the drainage channel to the trough, in use of the system.

I

Advantageously, the conduit pipe comprises a filter unit. Ideally, the filter unit has a composite structure for preventing small-and medium-sized particles passing through the filter, in use of the system.

S Advantageously, the trough further comprises a plant growing-medium.

More advantageously, the trough comprises reeds that filter pollutants or contaminants. Preferably, the trough comprises Phraginites auralis reeds. Suitably, an area around the reeds comprises gravel or resin.

Preferably, the system further includes a synthetic drainage material comprising a high-density polyethylene (HDPE) resin, which, in use, acts as a particulate filter.

In a preferred embodiment, the trough comprises three layers: a top layer comprising plant growing-medium, a middle layer comprising a synthetic drainage material and a lower layer comprising at least one trap.

Optionally, the sump comprises stone or gravel, for maintaining a required sump level, in use of the system.

Ideally, the sump comprises three traps.

Preferably, at least one trap comprises an inspection pipe, for inspecting, flushing or clearing the sump, in use.

Preferably, the drainage system further comprises an aeration manifold to provide, in use, local aeration and irrigation for tree roots located within the tree pit.

Advantageously, the aeration manifold comprises at least one perforated pipe.

In one embodiment, the system comprises a subsoil outlet for discharging, in use, water from the trough to subsoil outside the tree pit.

Conveniently, the subsoil outlet comprises a discharge pipe connectable to the aeration manifold.

In one embodiment, the drainage system comprises a flow control chamber.

Preferably, the flow control chamber receives water from the trough, in use of the drainage system. More preferably, the flow control chamber receives water from the aeration manifold, in use.

Suitably, the drainage system comprises a structural polymer matrix, ideally StrataCell TM Preferably, the structural polymer matrix comprises fill material. Ideally, the fill material comprises soil.

Advantageously, the soil is a type capable of withstanding short-term water logged conditions without change in its physical structure or chemical properties. Suitably, the soil is of a sandy loam type.

Preferably, the flow control chamber comprises an unfilled structural polymer matrix.

Alternatively, the flow control chamber comprises bricks. In a preferred embodiment, the flow control chamber is locatable outside the tree pit.

In a second aspect, the present invention provides a tree pit drainage system kit, the kit comprising a trough having a sump section comprising at least one trap.

Advantageously, the kit further comprises a drainage channel for receiving falling water, rainwater or surface mn-off, in use of the kit.

In a preferred embodiment, the kit further comprises at least one perforated pipe connectable to an outlet of the trough.

Conveniently the kit comprises a root director.

Suitably, the kit comprises four troughs, each trough being engageable with the root director.

Ideally, the kit further comprises a flow control chamber. Preferably, the flow control chamber comprises a structural polymer matrix.

Preferably, the kit further comprises a conduit pipe having a filter unit, the conduit pipe being engageable with the trough and with the drainage channel.

Advantageously, the kit further comprises plant growing-medium, and reeds that are capable of filtering pollutants or contaminants.

In one embodiment, the kit further comprises a synthetic drainage material comprising high-density polyethylene (HDPE) resin.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of troughs and a root director in accordance with the present invention; Figure 2 is a perspective view of the embodiment of Figure 1 also including an embodiment of an aeration manifold; Figure 3 is a close-up perspective view of the trough of the embodiment of Figure 1, illustrating an embodiment of a trap; Figure 4 is a perspective view of an embodiment of a drainage channel for use with the present invention; Figure 5 is a perspective view of the embodiment of Figure 2 including the drainage channel of the embodiment of Figure 4, an embodiment of a structural polymer matrix and an embodiment of a synthetic drainage material; Figure 6 is a perspective view of the embodiment of Figure 5 including reeds; Figure 7 is a cut-away perspective view of the embodiment of Figure 6, illustrating water flow though the drainage channels, in use of the system; Figure 8 is a cross-sectional view of the embodiment of Figure 6, illustrating water flow through the troughs, in use of the system; Figure 9 is a partial cross-sectional view of the embodiment of Figure 6, illustrating water flow through the aeration manifold to tree roots; Figure 10 is a partial cross-sectional view of the embodiment of Figure 6, illustrating water flow away from the tree pit; and Figure 11 is a partial cross-sectional view of the embodiment of Figure 6, illustrating water flow away from the tree pit to a flow control chamber.

Figure 1 illustrates a root director 20 and four troughs 10. Root director 20 has a truncated pyramidal shape. A central aperture of root director 20 is suitable for receiving a tree root ball. Each trough 10 has one sloping longitudinal face, which abuts a face of root director 20 and one vertical longitudinal face opposite the sloping face. The vertical face comprises a notch 25 at a top edge. Troughs 10 also comprise a plurality of outlets 21 located at a bottom edge of a vertical face.

Figure 2 illustrates an aeration manifold 11 comprising a perforated pipe 23 and a plurality of linking pipes 22. Linking pipes 22 engage outlets 21 of troughs 10.

Figure 3 illustrates an internal section of trough 10. Trough 10 has a trap 12 protruding from an internal face of its base. Trap 12 is a hollow truncated conical element engaged with outlet 21 of trough 10.

Figure 4 illustrates a drainage channel 13, which comprises a longitudinal channel and an aperture element 14. Aperture element 14 is a longitudinal top plate that covers the longitudinal channel. It comprises a plurality of transverse apertures. One longitudinal face of channel 13 comprises a radially-projecting conduit pipe 15. An end of conduit pipe 15 adjacent channel 13 is open to channel 13. An end of conduit pipe 15 remote channel 13 is open to trough 10. In a preferred embodiment, the end of conduit pipe 15 remote channel 13 comprises a composite filter unit 32.

Figure 5 illustrates an assembled embodiment of a drainage system in accordance with the present invention. The system comprises channel 13 encircling four troughs 10, each trough abutting a face of root director 20. A plurality of conduit pipes 15 open into troughs 10 at an end of the conduit pipe 15 remote channel 13. Each conduit pipe sits in a notch 25 in a wall of trough 10 (see Figure 1). Also encircling four troughs 10 is an aeration manifold 11 (see Figure 2). A layer of synthetic drainage material 16 (GeonetTM, for example) is positioned underneath aeration manifold 11. Undemeath layer 16 is a structural polymer matrix (StrataCellTM, for

example) 17.

S Figure 6 illustrates the assembled embodiment of Figure 5 including reeds 30 (Phraginites auralis reeds, for example) and resin 31 (ArboresinTM, for example).

Figure 6 also illustrates an inspection pipe 18. Inspection pipe 18 engages one of traps 12 of trough 10.

The multi-component trough apparatus described above is installed on site in a tree pit to control water flow through the tree pit, thereby providing tree root irrigation and preventing the tree pit from becoming water logged. During assembly of the above apparatus, an additional structural polymer matrix 40 (e.g. StrataCellTM) (see Figure 11) is arranged adjacent the trough assembly. The extent of matrix 40 required will depend on the nature of the site. Lengths of pipe 33 (see Figure 10) are also laid within matrix 40 for connection to the trough assembly. Matrix 40 is filled with a sandy loam during installation. Once matrices 40 and 17 have been installed and filled, a layer of synthetic drainage material (e.g. GeonetTM) is laid on a top surface of matrices 40, 17.

Once the apparatus has been installed, a tree is planted in root director 20 and secured using conventional straps and anchors.

In use of the drainage system of the present invention, falling water, rainwater or surface run-off in the vicinity of the tree pit in which the system is installed enters the system through transverse apertures in aperture element 14 of drainage channel 13 (see Figure 7). Drainage channels 13 are recessed into the road or other surface adjacent the tree. Channels 13 act as a trap for silt and debris such as leaves. Water is discharged from drainage channels 13 via conduit pipes 15 into troughs 10. A filter unit 32 is fitted to an outlet end of conduit pipe 15. Filter unit 32 is a composite filter, which prevents passage of small-and medium-sized particles through the filter unit.

Trough 10 comprises a fill material in the form of plant growing-medium for growing Phraginites auralis reeds. These reeds collect and process oil and fuel components contained in the water received in trough 10 from drainage channels 13, breaking the components down. The area around the reeds is finished with a layer of resin, such as ArboresinTM.

S Water received by the trough passes downwardly through the fill material in the trough. The fill material plant growing-medium) therefore acts as a filter, retaining small particles. At the base of the fill material is a layer of synthetic drainage material 16, GeonetTM, which acts as a further particulate filter. Positioned below layer 16 is a sump section of trough 10. The sump section comprises three traps 12. One trap 12 in each trough 10 is engaged with an inspection pipe 18 having a removable inspection cover. To inspect or maintain trough 10, the inspection cover is removed, which allows trough 10 to be flushed with water or suction to be applied in order to remove an obstruction.

As illustrated in Figure 8, water that has been filtered through the fill material in trough 10 is received in the sump section of trough 10. Water collects in the sump until the level rises above the top of traps 12, at which point water is discharged from trough 10. To reduce the water volume required in the sump section to maintain an appropriate sump level, the sump can be partially filled with stone.

Water is discharged from the sump section of trough 10 through outlet 21. It then enters aeration manifold 11 via linking pipes 22 and perforated pipe 23 (see Figure 9).

Aeration manifold 11 is located within structural polymer matrix 17 (e.g. StrataCellTM) and provides local aeration and also irrigation for tree roots that have established in matrix 17. Water in aeration manifold 11 is released in the vicinity of the tree roots through the perforations in perforated pipe 23. In the event that the drainage system comprises too much water to be absorbed by outflow from perforated pipe 23, excess water is removed from the tree pit via a discharge pipe 33, as illustrated in Figure 10. Discharge pipe 33 passes through StrataCellTM 17 and then exits the matrix. In one embodiment, a filter unit is provided at an outflow of discharge pipe 33 to remove particulate matter from the water prior to release of the water from the tree pit. Outflow from discharge pipes 33 is either released into the subsoil outside the tree pit, or is directed into and contained within a flow control chamber 35 (see Figure 11).

Flow control chamber 35 is formed from a structural polymer matrix such as StrataCellTM (with no fill material). Ideally, the matrix is fully wrapped in a geotextile. Altematively, chamber 35 is formed from bricks. Chamber 35 is used to S store excess water or to provide a centralised water source for distribution as required, depending on the nature of the installation site.

The apparatus described above acts to prevent flooding by controlling water flow in urban planted areas. The system collects, distributes and contains rainwater and surface run-off The system also filters out debris, pollutants and contaminants before releasing or storing water from the drainage system or using the water for tree irrigation. It provides for penetration of water (that could potentially generate flooding or water logging) into a tree's deep root zone.