NO344574B1

NO344574B1 - A conveyance, detention and infiltration system, and method of installing same

Info

Publication number: NO344574B1
Application number: NO20180618A
Authority: NO
Inventors: Aage Gjesdal; Per Møller Pedersen
Original assignee: Skjæveland Cementstoeperi As
Priority date: 2018-04-30
Filing date: 2018-04-30
Publication date: 2020-02-03
Also published as: NO20180618A1; WO2019212358A1

Description

A CONVEYANCE, DETENTION AND INFILTRATION SYSTEM, AND METHOD OF INSTALLING SAME

The present invention is related to a runoff conveyance, detention, and infiltration system for a liquid drained from a surface, and a method of installing same.

The present invention may typically be used as a stormwater handling system. The description below will therefore be directed towards a stormwater handling system, although the invention may also be used for other purposes such as biological degradation of chemicals drained from a surface. One example of such a biological degradation is de-icing liquids used in airports.

In the past, there has been an aim to bring substantially all of a stormwater runoff to a recipient such as a river, a lake or to the sea. The aim was previously met by providing a stormwater piping system dimensioned for torrential rain. However, World Meteorological Organization already reports a more than 10% increase in precipitation, and predictions are even worse for the upcoming decades.

Due to the facts that a majority of stormwater piping systems are old and not dimensioned for the increased precipitation, and a run-off coefficient in for example urban or industrial areas tending to increase due to an increase in surface areas having substantial impermeable surfaces, flooding tends to increase. To remedy such an increase in flooding due to torrential rain, there is a tendency from some local authorities in demanding a surface to be substantially self-draining, i.e. that at least a majority of the water from a torrential rain shall be infiltrated into the ground wherever possible, and at least detained.

Publication US 2016/0369491 discloses a stormwater runoff conveyance, detention, and infiltration system, wherein the system provides a means of integrating detention and infiltration within stormwater channels. The system comprises basins along and directly beneath a channel bed for stormwater runoff detention and infiltration, while providing a means of safe hydraulic communication between the storm channel and the detention/infiltration basins below. The system essentially creates a two-level stormwater channel with the upper level for conveyance and the lower level for detention and infiltration.

There are further known systems diverting the stormwater runoff to an off-channel detention storage facility for infiltration into the ground.

Detention of stormwater runoff from substantially impermeable surface, followed by either infiltration into the ground and/or treatment for quality improvement is becoming increasingly important as stormwater runoff in some areas is considered a valuable water resource and environmental regulations limit the pollutant loads that storm drains can discharge into natural water bodies such as a river, a lake, or the sea.

In the infiltration process pollutant substances flowing with the water may degrade in biological processes. Such processes will, together with filtration, result in a purification of the water.

However, prior art solutions provide limited infiltration areas which results in locally very high stress on the filtration substance, such as for example sand or gravel, and therefore also the biological processes. Significant amounts of water are brought in contact with only a small area/volume of the filtration substance and the appurtenant activity related to chemical and biological processes is very concentrated. As apparent from US 2016/0369491 an infiltration area is limited substantially along and directly beneath the stormwater pipe.

Møller-Pedersen (2017) discloses a stormwater runoff conveyance, detention, and infiltration system for receiving a liquid drained from a surface, as disclosed in the preamble of claim 1 ("Lett og grunn separering av vei- og takvann, fagseminar «Separering av eldre avløpsledninger i tettbebyggelse», Storm Aqua AS, 6. November 2017").

Publication JP 2000064405 A discloses an infiltration pipe for infiltrating rain water. The infiltration pipe comprises a culvert with a weir formed therein and infiltration hole provided in a sidewall.

Publication JP H0813597 A discloses a culvert for underground draining of water. A top portion of the culvert is provided with slits, and the sides are provided with apertures.

Publication JP S59188573 U discloses an infiltration pipe having apertures along its wall.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

According to a first aspect of the invention, there is provided a stormwater runoff conveyance, detention, and infiltration system for receiving a liquid drained from a surface, the system comprising:

a main pipe having a first end portion and a second end portion;

at least one fluid channel for communicating the liquid into the main pipe;

at least two mutually spaced apart apertures in a side portion of the main pipe; and at least one infiltration pipe in fluid communication with the main pipe via the apertures. At least the second end portion of the main pipe is provided with flow retaining means for preventing free-flow of the liquid out of the main pipe. Further, the apertures for the infiltration pipes are arranged at the same level independent of any slope of the main pipe.

The liquid typically comprises rain water but may also or alternatively comprise other liquids such as flushing water, chemicals and particulate substances which is communicated into the main pipe. One example of a chemical that may flow into the system is a biological degradable de-icing agent commonly used for de-icing of airplanes in an airport. Another example is various types of chemicals that may be spilled onto a surface of an industrial plant. Hereinafter, the liquid will also be denoted "water" although it may comprise other liquids and particulate substances.

The infiltration pipe is configured with a plurality of openings through a wall of the pipe at least along portions thereof for allowing communication of fluid out of the pipe and into an infiltration substance, such as for example sand or gravel.

The feature of providing at least the second end portion of the main pipe with flow retaining means for preventing free-flow of water out of the main pipe, has at least two important effects. Firstly, the flow retaining means may prevent at least some of the water from flowing out of the second end portion of the main pipe. In an embodiment where the system is limited to only one length of pipe (and not two or more pipe lengths arranged in series as will be discussed below), the first end portion of the pipe is preferably sealed off by a suitable sealing means known per se. The water surface within the main pipe may thus raise and the main pipe provides a detention chamber. Secondly, the raise of the water surface occurring as a result of the end seal and end restriction in the main pipe, will result in a hydrostatic pressure urging the water out of the at least two apertures and into the at least one infiltration pipe in fluid communication with the apertures.

The raise of the water surface will be substantially level, i.e. horizontal, along the length of the main pipe. Since the apertures for providing fluid communication between the main pipe and the infiltration pipe is also in level, the hydrostatic pressure at the apertures will be equal. This has the effect that the water from within the main pipe will start flowing into the infiltration pipe at the same time and be subject to the same hydrostatic pressure. Therefore, the water will be equally distributed into the infiltration pipe(s) through the apertures along the main pipe.

Preferably, the infiltration pipe or pipes forming part of the system according to the present invention is along its length arranged substantially in level with the apertures in the main pipe. This has the effect that the flow of water into the filtration substance on the outside of the infiltration pipe will be substantially equal along the length thereof.

The system may comprise an upstream main pipe and at least one downstream main pipe interconnected in series by means of a basin. Such a basin comprises an inlet for receiving the second end portion of the upstream main pipe and an outlet for receiving the first end portion of the downstream main pipe. In one embodiment, the inlet may be arranged at a lower elevation than the outlet of the basin. This has the effect of inter alia allowing slope of two or more main pipes arranged in series, without "loosing height" within the system because the main pipes may be arranged in a sawtooth pattern wherein the first end portions may be arranged substantially at the same level, i.e. the same grade elevation, within the system.

Preferably, but not necessarily, an internal lowermost portion of the downstream main pipe is lower than the internal uppermost portion of an upstream main pipe such that any flow from an upstream main pipe may flow via said basin and into the downstream main pipe.

In another embodiment, typically applied in a sloping ground, the inlet may be arranged at a higher elevation than the outlet, as will be explained below.

The flow retaining means for retaining at least a portion of water within the main pipe by preventing free flow of water out of the second end portion of the main pipe, may be provided with a weir for allowing flow of water into the basin connecting the upstream main pipe with the downstream main pipe. Obviously, the elevation of the weir has a direct influence on the level of the water surface within the upstream pipe.

Thus, the first end portion of the upstream main pipe may be blocked and the flow retaining means of the second end portion of the upstream main pipe may be provided with a weir.

The main pipe may be sealed or blocked in a downstream end portion of the system. Such a seal will prevent water from flowing directly out of the main pipe of the system without flowing through the infiltration pipes.

Thus, a main pipe or a system comprising a series of main pipes may be blocked or sealed at extreme end portions. However, the second end portion of a system may be provided with an outlet configured to allow direct flow of water out of the main pipe when the water level exceeds a predetermined level. In one embodiment, the predetermined level may be adjustable, for example by means of a valve.

Preferably, in a position of use, a lowermost portion of the apertures for providing fluid communication with the main pipe and the at least one infiltration pipe, is arranged at a higher elevation than a bottom portion of the main pipe. One of the effects of this is that a "catch pit" is provided which reduces inflow of particulate substances that are likely to flow with the water from the surface and into the system. Another effect of such a configuration of the apertures is that the catch pit will normally remain saturated. Experience shows that a saturated or wet deposit tends to be more easily removable than deposits allowed to dry.

Especially during torrential rain, particles such as for example sand, leaves and waste, may flow into the infiltration pipe and settle therein, and possibly block at least some of the perforations provided in a lower cross-sectional portion of the infiltration pipe. Due to gravity, a risk of settlement of particles in the infiltration pipe is higher in a portion being close to the aperture in the main pipe, than in a portion being further away from the aperture. Thus, settlement in the infiltration pipe may violate the evenly distributed infiltration or "spreading" area that is sought provided by the present invention.

To remedy the above challenge, it may from time to time be necessary to flush the infiltration pipe by means of for example a pipe flushing apparatus known per se. Such a flushing apparatus typically comprises a flushing and propelling head connected to a leading end of a hose connected to a high-pressure unit for supply of water. To facilitate insertion of a portion of the flushing apparatus into the infiltration pipe, the fluid channel that typically may connect the surface to the main pipe may be provided with an access pipe in fluid communication with the infiltration pipe. Thus, the flushing apparatus may easily be inserted through the access pipe from surface, for example from a top portion of the fluid channel.

Biological degrading processes utilizes oxygen. To facilitate the degrading process of a fluid infiltrated into the ground adjacent the infiltration pipe, it may in particular circumstances be advantageous to supply air into the infiltration pipe. In one embodiment the infiltration pipe is further provided with a perforated fluid supply pipe for supplying a fluid along at least a portion of the infiltration pipe. Such a fluid may be pressurized air urged into the perforated fluid supply pipe. The fluid supply pipe may alternatively or additionally be used for inserting any chemicals into the infiltration pipe. Such a chemical may for example be a cleaning agent that assists in the breaking down of unwanted substances, a liquid that prepares the water for further treatment or a biological substance that stimulates a biochemical process.

A main pipe may typically be made by interconnecting pipe sections made from concrete. In order to arrange the apertures at the same level independent of any slope of the main pipe, the apertures are provided in situ. To facilitate the making of the apertures with respect to health and safety, and time spent, the main pipe may be provided with a portion consisting of an easily drillable material. Thus, the apertures may be provided in a portion of the main pipe consisting of a material differing from the material in the rest of the main pipe.

In a second aspect of the invention there is provided a method for installing a system according to the first aspect of the invention, in a ground, wherein the method comprises the steps of:

- preparing a trench for the system;

- installing at least a section of a main pipe in the trench;

- providing at least two apertures for at least one infiltration pipe along predetermined portions of the main pipe, wherein the apertures are arranged at the same level independent of any slope of the main pipe; and

-connecting the infiltration pipe to the apertures in the main pipe.

Along its length, a centre portion of the infiltration pipe may be arranged substantially in level with a centre portion of the aperture in the main pipe.

The step of installing at least a section of the main pipe, may comprise installing a flow retaining means at the second end portion of the main pipe.

The method may comprise arranging the infiltration pipe in a loop, the end portions of which are connected to the main pipe via the apertures.

Preferably, the apertures are provided in an installed section of the main pipe prior to connecting a subsequent section to the installed section. Thus, easy access to an internal portion of the main pipe is provided.

In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:

Fig. 1 shows a top view of an open stormwater runoff conveyance, detention, and infiltration system according to an embodiment of the present invention;

Fig. 2 shows in a larger scale a perspective view of a system according to the invention comprising two main pipes arranged in series;

Fig. 3 shows in a larger scale a partial cut through a portion of a system according to the invention;

Fig. 4 shown in a larger scale a cut through portion of the system;

Fig. 5 shows in a larger scale a cross section of a main pipe suitable for use in the system according to the invention;

Fig. 6a shows in a smaller scale a top view of a system according to the invention, wherein the system comprises three main pipes arranged in series, two of which are provided with infiltration pipes; and

Fig. 6b shows a cut through A-A in fig. 6a indicating a sloping ground having various soils.

In the figures, same or corresponding elements are indicated by same reference numerals.

Position indications such as for example, upper, lower, inner, outer, left, right, upstream and downstream refers to a position of use of the system, and as shown in the figures.

A person skilled in the art will understand that the figures are principle drawings, and that relative proportions between individual elements may be distorted.

For clarity, some of the element shown may in some of the figures be without reference numerals.

In the figures 1 to 6b, reference numeral 1 denotes a system according to the present invention. The system 1 comprises a main pipe 3, here shown as a stormwater pipe 3. In the embodiments shown, the stormwater pipe 3 is made from a plurality of pipe sections 3', typically made from concrete, interconnected in series as will be appreciated by a person skilled in the art. The stormwater pipe 3 has a first end portion 5 and a second end portion 7.

The system 1 is further provided with a fluid channel 10 for communicating surface water into the stormwater pipe 3. In the embodiment shown, the fluid channel 10 is shown in the form of a plurality of manholes 10 which extend substantially vertically upwards from a top portion of the stormwater pipe 3 to a surface (not shown) of a ground from which water flows into the manholes 10. In the embodiment shown for example in fig. 4, the manhole 10 is provided with a gully grid 12 to prevent objects exceeding a predetermined size from entering into the manhole 10 and thus the stormwater pipe 3. It should be noted that the fluid channel 10 may alternatively or additionally be a conduit for conveying water, such as surface water, into the stormwater pipe 3.

The stormwater pipe 3 is provided with at least two mutually spaced apart apertures 14 arranged in a side portion of the stormwater pipe 3. In the embodiment shown in fig. 1 the stormwater pipe 3 is provided with twenty apertures 14; ten along each side portion of the stormwater pipe 3. However, the number and mutual arrangement of the apertures 14 will be adapted to local conditions based on each of or a combination of for example soil conditions, surface area to be drained, if all or only some of the water received by the system 1 shall be infiltrated into the ground, etc.

Each of the apertures 14 in the stormwater pipe 3 is in fluid communication with an infiltration pipe 20. In fig. 1, a total number of ten infiltration pipes 20 are shown arranged in loops so that one infiltration pipe 20 connects two succeeding apertures 14 along the stormwater pipe 3. However, the infiltration pipes 20 may be arranged in any desired pattern, for example so that one infiltration pipe 20 connects the far left aperture 14 with the far right aperture 14, another infiltration pipe 20 connects the second from the far right aperture 14 with the second from the far left aperture 14, etc. Preferably, none of the infiltration pipes 20 crosses each other.

Although the infiltration pipes 20 in fig. 1 are arranged symmetrically across a longitudinal axis of the stormwater pipe 3, it should be clear that the infiltration pipe 20 may be arranged in a non-symmetrical pattern across the longitudinal axis of the stormwater pipe 3, or even extending from only one side of the stormwater pipe 3.

The purpose of the infiltration pipe 20 is to receive water from within the stormwater pipe 3 and spread or distribute the water by means of infiltration in an adjacent ground or in an underlying bed/layer. The infiltration pipe 20 is provided with a plurality of openings or perforations arranged in a lower portion of the wall along its length. In one embodiment, the infiltration pipe 20 is a drainage pipe known perse installed with its openings in a lower portion in the position of use. In an alternative embodiment, the infiltration pipe 20 may be a pipe with wall openings tailormade for example in situ to local conditions. In such an embodiment a mutual spacing between the openings along the infiltration pipe 20 may vary.

The inventors have surprisingly found that the reliability and effect over time of such an infiltration spreading is improved if the infiltration pipes 20 are substantially equally utilized, i.e. receives a substantially equal flow of water from the stormwater pipe 3.

A stormwater pipe 3 will typically be arranged sloping from a higher elevated first end portion 5 to a lower elevated second end portion 7 as shown in fig. 3. The slope will normally be less than 1% for example 4 %o (4 mm/m). However, the stormwater pipe 3 may in some situations be arranged without a slope, i.e. level or horizontal, or with a slope being more than 1%.

A system 1 comprising sloping stormwater pipes 3 arranged in series, is shown in fig.

3. An upstream stormwater pipe 3 (shown to the right) is sloping towards a basin 30 interconnecting the upstream stormwater pipe 3 with a downstream stormwater pipe 3 (shown between the two basins 30 shown). A second end portion 7 of the upstream stormwater pipe 3 is provided with a flow retaining means in the form of a barrier 22 arranged in the right basin 30. The purpose of the barrier 22 is to prevent free-flow of water out of the stormwater pipe 3. Therefore, the upstream stormwater pipe 3 is nearly filled with water indicated by water surface WL at its second end portion 7. The downstream stormwater pipe 3 is only partly filled with water, also indicated by water surface WL. Such a difference in degree of filling may typically occur if the upstream stormwater pipe 3 receives surface water from a larger area than the downstream stormwater pipe 3, and/or if the water is supplied to the surface being drained by the upstream portion of the system 1.

In order to avoid flooding of the upstream portion of the system 1, some water from the upstream stormwater pipe 3 may be conveyed into the downstream stormwater pipe 3 by the barrier shown in more detail in fig. 4.

In the embodiment shown in fig. 4, a gap is defined by a top horizontal surface of the barrier 22 providing a weir, and an internal curved top portion of the stormwater pipe 3. In an alternative embodiment (not shown) the barrier 22 covers all of the crosssectional area of the stormwater pipe 3 to provide a water tight seal.

When the stormwater pipe 3 receives water for example through the fluid channel or manhole 10, a water surface within the pipe 3 may raise above the apertures 14 through the wall of the pipe 3. Thus, the water at the apertures 14 will flow into the infiltration pipes 20.

Having identical apertures 14 providing fluid communication with the infiltration pipes 20 along the length of the stormwater pipe 3, a hydraulic resistance will be substantially equal. A flow of water from the stormwater pipe 3 into the infiltration pipe 20 will depend on a hydraulic pressure at the apertures 14. To achieve a substantial equal flow rate of water into the infiltration pipes 20, the apertures 14 for the infiltration pipes 20 are therefore arranged in level independently of any slope of the stormwater pipe 3.

In the embodiment shown, it should be understood that a cross sectional centre portion of the infiltration pipes 20 are arranged substantially level with a centre portion of the apertures 14. This has the advantage of providing a substantially equal hydrostatic pressure along the entire length of the infiltration pipe 20, and thus an as even infiltration regime as possible.

In practice, it may be difficult to arrange the infiltration pipes 20 in exact same level. Therefore, the term "substantially level" should be understood as variance in level within a diameter of the infiltration pipe 20, so that the difference in level along the length of the infiltration pipe 20 is less than two times an internal diameter of the infiltration pipe 20or this reason, it is also desirable to avoid crossing of infiltration pipes 20.

For reasons mentioned above, it is an advantage if a bottom portion of the stormwater pipe 3 holds water. In order not to continuously drain the bottom portion of the stormwater pipe 3, the lowermost portion of the apertures 14 are elevated with respeet to the bottom portion of the stormwater pipe 3. In one embodiment wherein the stormwater pipe 3 is of the type described below, the bottom portion of the aperture 14 are arranged minimum about 12 % of the internal height of the stormwater pipe 3, above the bottom portion of the stormwater pipe 3. As an example: in a stormwater pipe 3 having an internal diameter of 800 mm, a bottom portion of a lowermost aperture 14 will be at least 100 mm above the bottom portion of the stormwater pipe 3.

A portion of the wall of the stormwater pipe 3 may be constituted by a material being different from the material, typical concrete, constituting the rest of the stormwater pipe 3. The purpose of such a material is to provide an easily drillable material while at the same time produce less dust during the drilling operation. In one embodiment a plastic material such as extruded polystyrene (XPS) is integrated in and forming part of the wall of the stormwater pipe 3. In fig. 4 such an integrated material is shown as an oblong insert material having reference numeral 15. The oblong form is preferred to allow for arranging the aperture 14 independently of the slope of the stormwater pipe 3.

As shown in fig. 5, the stormwater pipe 3 may have a non-uniform cross sectional radius. A bore of the stormwater pipe 3 is provided with a "V-shaped" lower portion wherein the internal radius Rb in a bottom portion is less than an internal radius Rt in a mid- and top portion of the bore. Such a type of stormwater pipe 3 wherein the bottom portion of the pipe has a curvature that is less than a curvature in a mid- and top portion of the pipe is particularly effective with regards to "self-cleaning". The pipe shown in cross-section in fig. 5 is a type of stormwater pipe manufactured by the applicant and sold under the trade name "Qmax". In addition to having a self-cleaning effect, such a pipe also provides good detention capability in addition to high strength, i.e. load bearing capacity. A Qmax stormwater pipe with an internal diameter (top to bottom) of 800 mm, has a water detention capacity of 3.5 m<3>/ 10 meter of pipe. However, it should be noted that even if a stormwater pipe 3 of the type shown in fig. 5 is preferred, any type of stormwater pipe may be used as part of the system 1 according to the invention.

From the above, it will be clear that the system 1 according to the embodiment discussed above has a considerable water detention capacity. The capacity is provided by the stormwater pipe 3 itself and the volume provided by the infiltration pipes 20.

Turning back to fig. 4, the barrier 22 is provided with a valve device, here shown as a gate valve 24. An opening 25 of the valve 24 corresponds with the lower internal portion of the stormwater pipe 3 so that settlements from within the stormwater pipe 3 can be flushed out through the opening 25 and into a basin 30 during a flushing operation. The valve 24 is normally closed but is opened during a flushing operation for removing settlements. The valve 24 may also be operated if a regulation of the water level within the stormwater pipe 3 is desired.

In the embodiment shown in fig. 4, the basin 30 is also used as an interconnecting means for interconnecting in series an upstream stormwater pipe 3 (to the right in the figure) and a downstream stormwater pipe 3 (to the left in the figure). The basin 30 has an inlet 32 for receiving the second end portion 7 of the upstream stormwater pipe 3 and an outlet 34 for receiving the first end portion 5 of the downstream stormwater pipe 3. In fig. 4, the inlet 32 is arranged at a lower elevation than the outlet 34 of the basin 30. Such a configuration allows for arranging the series of stormwater pipes 3 in a sawtooth pattern, which again allows for arranging each of the stormwater pipes 3 with a slope over long distances in otherwise substantially flat (non-sloping) areas.

In an alternative embodiment, the inlet 32 is arranged at a higher elevation than the outlet 34 of the basin 30. Such an embodiment is particularly relevant in a system 1 arranged in a sloping ground as shown in principle in fig. 6b which is a cut through A-A of fig. 6a.

In figures 6a and 6b the system 1 is arranged in a soil having variable infiltration capabilities. The system 1 comprises an upstream stormwater pipe 3, an intermediate conveyance stormwater pipe 4, hereinafter denoted "intermediate pipe" 4, and a downstream stormwater pipe 3.

As illustrated in fig. 6b, the intermediate pipe 4 is arranged in a ground consisting substantially of impermeable clay C, while the upstream stormwater pipe 3 and the downstream stormwater pipe 3 is arranged in a ground substantially comprising of permeable soil, such as sand with organic material G. Thus, water flowing into the intermediate pipe 4 via fluid channels 10 (not shown in fig. 6b), and/or from the upstream stormwater pipe 3, will not be infiltrated in the ground at the intermediate pipe 4. Instead it will be led to the downstream stormwater pipe 3 and infiltrated into the ground G therefrom.

In fig. 6b, water infiltered by means of the infiltration pipes 20 are indicated by small, vertical arrows. A groundwater flow is indicated by the large arrow.

The intermediate pipe 4 differs from the upstream stormwater pipe 3 and the downstream stormwater pipe 3 in that it is neither provided with apertures 14 (and infiltration pipes 20 connected thereto), nor with a barrier 22 (se fig. 4) at a downstream end portion. It should therefore be understood that the intermediate pipe 4 shown in principle in figures 6a and 6b is a prior art stormwater pipe for runoff conveyance and detention without infiltration. In one embodiment, the intermediate pipe 4 may be provided with fluid channels (not shown) for communicating a surface water from above the intermediate pipe 4 and into the intermediate pipe 4. Said fluid channels may for example be the manholes 10 shown in for example figures 3 and 4.

Similarly, the fluid channel 10 for communicating surface water into the stormwater pipes 3, may be the manholes 10 shown in for example figures 3 and 4. However, the lowermost stormwater pipe 3 (the one to the right in fig. 6b) may additionally or alternatively receive water from the intermediate pipe 4, via the basin 30.

Turning again back to fig. 4, the fluid channel or manhole 10 is in the embodiment shown provided with an access pipe 21, here shown as branch tubes, being in fluid communication with the infiltration pipe 20. When or if there is a need for flushing the infiltration pipe 20, a pipe flushing apparatus known perse is inserted into the access pipe 21 and further into the infiltration pipe 20. Having a loop configuration of the infiltration pipe 20, for example as shown in figures 1 and 2, a flushing apparatus inserted via one access pipe 21, may be propelled within the infiltration pipe 20 until it arrives at an access pipe 21 in a neighbouring fluid channel 10. In this way an operator will have a confirmation that flushing has been performed along the entire length of the infiltration pipe 20. Thus, at least for flushing reasons, it is preferred to arrange the infiltration pipes 20 in loops for example as shown in figures 1, 2 and 6a, or as discussed above. However, the system 1 may alternatively or additionally comprise infiltration pipes 20 each extending from one aperture 14 only, or a network of interconnected infiltration pipes 20 connected to a plurality of apertures 14.

The access pipe 21 may also be used for inserting a perforated fluid supply pipe 21' (indicated by broken line) for supplying a fluid along at least a portion of the infiltration pipe 20.

From the disclosure herein, it should be understood that the present invention may provide a stormwater runoff conveyance, detention, and infiltration system 1 for a liquid drained from a surface that will at least reduce an amount of liquid allowed to flow into a natural water body, such as a river, a lake, or the sea. Due to its capability of even infiltration of water into the ground, the system will prevent locally very high stress on the filtration substance. A degrading of biological substances, such as biodegradable chemicals, is therefore optimised.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

C l a i m s

1. A stormwater runoff conveyance, detention, and infiltration system (1) for receiving a liquid drained from a surface, the system (1) comprising:

a main pipe (3) having a first end portion (5) and a second end portion (7); at least one fluid channel (10, 4) for communicating the liquid into the main pipe (3);

at least two mutually spaced apart apertures (14) in a side portion of the main pipe; and

at least one infiltration pipe (20) in fluid communication with the main pipe (3) via the apertures (14), c h a r a c t e r i z e d i n that at least the second end portion (7) of the main pipe (3) is provided with flow retaining means (22) for preventing free-flow of the liquid out of the main pipe (3); and that the apertures (14) for the infiltration pipe (20) are arranged at the same level independent of any slope of the main pipe (3).

2. The system (1) according to claim 1, comprising an upstream main pipe and at least one downstream main pipe interconnected in series by means of a basin (30), the basin (30) having an inlet (32) for receiving the second end portion (7) of the upstream main pipe and an outlet (34) for receiving the first end portion (5) of the downstream main pipe.

3. The system (1) according to claim 2, wherein the inlet (32) is arranged at a lower elevation than the outlet (34) of the basin (30).

4. The system (1) according to claim 2 or 3, wherein the first end portion (5) of the upstream main pipe is blocked and the flow retaining means (22) of the second end portion (7) of the upstream main pipe is provided with a weir.

5. The system (1) according to any of the preceding claims, wherein the main pipe (3) is blocked in a downstream end portion (7) of the system (1).

6. The system (1) according to any of the preceding claims, wherein the fluid channel (10) is provided with an access pipe (21) in fluid communication with the infiltration pipe (20).

7. The system (1) according to claim 1, wherein infiltration pipe (20) is further provided with a perforated fluid supply pipe (21') for supplying a fluid along at least a portion of the infiltration pipe (20).

8. The system according to any of the preceding claims, wherein the apertures (14) are provided in a portion (15) of the main pipe (3) consisting of a material differing from the material in the rest of the main pipe.

9. A method for installing a system (1) according to any of claims 1-8, in a ground, wherein the method comprises the steps of:

- preparing a trench for the system (1);

- installing at least a section (3') of a main pipe (3) in the trench;

- providing at least two apertures (14) for at least one infiltration pipe (20) along predetermined portions of the main pipe (3), wherein the apertures (14) are arranged at the same level independent of any slope of the main pipe (3); and

-connecting the infiltration pipe (20) to the apertures (14) in the main pipe (3).

10. The method according to claim 9, wherein a centre portion of the infiltration pipe (20) along its length is arranged substantially in level with a centre portion of the aperture (14) in the main pipe (3).

11. The method according to claim 9, wherein the step of installing at least a section of the main pipe (3) comprises installing a flow retaining means (22) at the second end portion (7) of the main pipe (3).

12. The method according to claim 9 or 10, wherein the method comprises arranging the infiltration pipe (20) in a loop, the end portions of which are connected to the main pipe (3) via the apertures (14).

13. The method according to any of the claims 9-12, wherein the apertures (14) are provided in an installed section (3<1>) of the main pipe (3) prior to connecting a subsequent section (3') to the installed section (3')·