Heavenly Resource

Everything to do with stormwater and water management

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Sometimes different authorities use the same public space but their interfere with each others function. The photo above shows new telecommunication pits have been cut in to an existing functioning spoon drain.

Now the spoon drain flow has been interrupted and I would expect that water may pond around the pits causing a localised issue.

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An older style of design of roadway drainage involved continuing the road channel past the intersection with a connecting road.

A more modern approach is to provide underground drainage to drain past the intersection. That way the surfaces of the two roads can be blended in smoother.

In the photo above the blue stoner pitchers can be seen still intact forming the old drain. It is unusual to see this type of intersection in Melbourne outer suburbs. But some of the inner Melbourne suburbs may still have this system still.

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Sometimes open drains do not discharge to a drainage system. They may be terminated in a landscape area. The photo above shows a footpath spoon drain that drains to a newly created landscaped area.

There is nothing necessarily wrong except that it puddles for a while after it rains. This is the entry to a kids playground and creates a nuisance to the users to the park.

In my experience many parks are developed without necessarily thinking about stormwater drainage. This is unfortunate as i believe drainage is a necessary consideration to landscaped architecture.

It is important to reduce the amount of impervious area that discharges to natural water bodies. It is good that in the above example that stormwater is disconnected from draining into the underground system. But it can be done better so that it does not create a nuisance.

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Open drains have enough problems on their own to maintain the design intent. But people like to put all sort of things in them to destroy the capacity.

In the photo above it would appear that the property owner is having a problem with the vehicle crossing to their property. The road surfaces are back falling, so there was a spoon drain introduced to capture some of the road reserve runoff.

The sad thing I have found in my experience is such systems are not maintained well and even if the maintenance crews come they may not notice something like that. Only once when there is a drainage complaint, drainage engineers investigating may notice something like this.

Similarly with the photo above, and object has been placed over part of a spoon drain reducing it’s capacity dramatically.

It is not only a tripping hazard but its function appears not to be authorised by the road authority. Again sadly something like this may not be picked up on a safety or a road asset audits. It will be an asset that exists in the roadway but who owns it and who will be responsible for any flooding and safety issue?

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Spoon drains are small open drains that can drain smaller areas.

If spoon drains are not maintained properly they will cause flooding or direct water not captured to another area where it is not desirable.

Very often the spoon drains have small grating pits in the end the meant to capture the water they catch. Very often the pit is very small and gets blocked easily.

The photos above is show a spoon drain that is blocked. It is meant to capture water from the footpath and deliver it to the Side Entry Pit at Kerb and Channel of the roadway.

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There is a need to design a road so as a good slope is achieved on the road channel. If the longitudinal grade of the roadway is too flat (usually 0.5%)  the channel also will be flat and the same grade.

Having flat channels will cause the water to pond or move very slowly. That will cause issues for the vehicles using the road way. More pits will need to be introduced to capture the water so that the road will not flood.

In the photograph above there is evidence that the Kerb and channel would have flat grades. The water marks and ponding is an indicator that you might have a flat channel.

As it is not practical to redo the road again, additional drainage will be needed.

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It is important when concrete open drains , like kerb and channels, are constructed that are defect or crack free. The life of such assets should be at least 25 years or more. If they start their life with defects their useful life is greatly reduced and then the community will have to find more money to replace them early.

Good quality assurance and contract management practices will ensure that the works are constructed in good order and condition.

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Kerb and Channels at the side of the road way should be maintained adequately to avoid unnecessary injury to persons.

The grassed area behind the Kerb if it is not maintained properly it can sink and present a tripping hazard. For a safe public area the responsible authorities should ensure tripping hazards such as these are eliminated.

Also the public can help as well. It usual for residents in Melbourne, Australia to maintain this grassed area in residential areas. This area is usually referred as a nature strip. They can either fill in behind the kerb themselves, or contact their local Council to do so. It would be a shame if the residents themselves  trip over it, after observing this issue outside their properties.

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The channels at the side of the roads are there to take the rainwater away to the nearest pit. Unfortunately if the slope is too flat the channel does not drain properly and puddles remain after the rain stops.

Large trees in the proximity of the channel make the channel move. The tree roots are large and interfere with the base of the channel , changing the design slope. This is unfortunate as this situation becomes a maintenance problem as silt and debris accumulate and the larger ponding during a rainfall event will make it difficult and dangerous for the traffic.

The photo above is interesting. We can see a newer section of Kerb and Channel has been constructed , assumingly to correct the slope of the channel. But the tree problem is still evident as the channel still hold water and collects debris.

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The above photo above shows an example of a poorly connected property drain to the Municipal drainage system.

There are twin plastic pipes fully exposed and section of the kerb cut out. These pipes will deteriorated over time and there is a good chance they will be crushed.

Municipal drainage inspectors inspect connection to the drainage system. It is unlikely that this situation has been passed as it would not form part of a suitable connection method.

The above photo shows what appears a poorly maintained kerb connection to the Municipal system.

It may have been constructed properly but now the lid of the connection is broken and the connection may not be functioning.

This type of situation is unfortunate. This situation now represents a hazard in a public area and the risk of somebody tripping and injuring them selves could be significant. In my experience is that some drainage authorities in Melbourne, Australia,  still consider this a private asset in a public reserve. In other words what they mean a person injured or suffering a loss because of this connection may sue the owners to recover compensation. Let us hope this does not happen !!

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A good Kerb connection to the street’s kerb and channel is essential to a good property drainage. property owners should check often if the connection is still working. Right after a rainfall event would be good. Even if you do not see the water running out into the channel, they are usually water marks that would indicate that the pipe is running.

Sometimes a pipe could be crushed in the nature strip or a service authority could go through the pipe with their construction equipment. So if you notice something unusual in a rainfall event it would be good to check your kerb connection. If it is not raining at the time of checking, a hose with rainwater tank water or potable water can be used to check if the connection is true and functioning.

Kerb connections under hard standing pavements have more protection from crushing but they are harder to reinstate. Concrete pavements would need to be saw cut to get to the pipe. If the drainage authorities allow it you can construct saw joints like in the photo above to make it easier to reinstate the pipe in the future.

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Sometimes you do not want to drain a public footpath to a telecommunication pit!

Correct positioning of the pit and appropriate sloping of the path is to be achieved in order to obtain a more satisfactory situation.

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Footpaths and walking tracks should be sloped in such a way that they drain freely to adjoining surfaces if appropriate. They also could be made to discharge to an underground system.

In the photo above a walking track is not draining well. In fact it has created a puddle that forces the bicycle and pedestrian traffic onto the grassed areas.

The usual cause in such instances is that if the path is flexible like a bitumen track it can deform and create low points that cannot be drained.

Sometimes like in the photo above the path would have drained well if it wasn’t for the fact that the grassed area is preventing this from happening. A raised grassed area is often the problem of drainage. Grassed areas accumulate silt and other material in the area in which they grow. This often raises the area above any hard standing area.

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Culverts are stormwater drains that allow water to pass through a structure or a road way without having a big impact with the traffic of the roadway or structure. In the photo above shows a small and simple culvert that allows water to flow underneath a bitumen walking track.

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Selecting the right pipe alignment is very important in a stormwater drainage projects.

Sometimes it may be desirable to cross over an existing drainage line. A consideration should always be given to connect drainage lines.

Important consideration is also avoiding obstacles like power poles. Ensure that an adequate offset is maintained for the depth of the pipe from the pole. The Power Authority should be consulted and asked to endorse the works so that any construction problems cab be resolved smoothly.

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Sometimes it is not appropriate to open cut a trench. It could be that you are crossing a major roadway and the works will cause traffic problems. Sometimes the land above the proposed pipe is not accessible. Other times you want to lay a pipe without disturbing a structure or building above.

What ever the reason you cannot open cut there are some solutions. A pipe can be bored (tunneled), Rammed or jacked. Special equipment are used to perform this. This type of pipe construction is very expensive and slow. Depending on the machinery and method you use, a large area at the start and the finish is required. This is so that the pipe ramming or jacking can be performed. Similar requirements are required for boring machines.

So it is very important consideration not to open cut as you project costs could escalate. Sometimes this requirement can be imposed by road authorities as they are protecting their asset.

It is important to use a method that is accurate for your purposed. If there is a tight envelope that you can do your work, accuracy is important. There could be services that you want to avoid or you need to confine your works within an easement. Such situations require accuracy. So the method you use is important. If the boring technique you use is not accurate, the alignment may change and further costs may be added to your project.

Apart from boring and tunneling conditions imposed by a road authority, the designer maybe required to meet certain hydraulic parameters in the design. Once such condition may be that the pipe must not flow under pressure or head for the design storm. Another requirement may be that the design storm for the section crossing is increased to a more severe storm to minimise any flooding issues with the roadway.

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Sometimes there is a need to make a drop in the invert level alignment at the pit. This could be for many reasons. Sometimes there is a need to deepen a pipe to avoid clashes with other assets. Sometimes there is a need to dissipate energy in the pipe. By introducing a deliberate drop in the pit you are forcing the inlet pipe to direct the flow to the pit wall thus reducing the velocity head in the system.