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Failed percolation test, not allowed to connect to sewer - options


RichyC
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I'm not sure where to put this one so hopefully I've got the right forum.ive  Been looking online but can't find an answer. Can anyone offer advise:

 

We had a perc test done which failed and so we're hoping to connect to a combined sewer but the utility company have declined that suggestion telling us we need to connect to a surface water sewer located uphill, 2 roads over and behind 5 other properties. The reason for not allowing the combined sewer access is because we have increased surface water flow from 2x newbuilds on the site. Our structural engineer has been in negotiation with the utility company with a suggestion that we put an attenuation tank with a hydrobrake to reduce flow but its been met with strong resistance.

 

With this in mind I'm not sure what our other options are at this point. Does anyone have any suggestions of any specialist companies we can talk to about this? 

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Not knowing all the circumstances and having been involved is some attenuation works the only thing I can come up with is suggestions:

One job we produced a "dry" attenuation pond which a bit like the tank reduces the flow.

Another we made a massive store under an entire tennis court.

Another we delayed the runoff from roofs with sedum. 

It really depends on the volumes involved. 

What are the ground conditions? 

So do I understand correctly that you are in the middle of putting 2 new properties on a site.

Up hill is always worse than downhill as you rely on pumps so I would ask what is down hill. assuming your not at the bottom of the hill...

My brother-in-law is involved in roads and services designs including housing estates, motorways and so on, and he may know someone. What part of the world are you in?

 

Edited by Marvin
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Another option to discuss would be the option of a rainwater harvesting system - directing the runoff to a large tank that can be used for flushing WCs, washing machines and the like - you're recycling the water instead of disposing of it.

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1 hour ago, Mike said:

Another option to discuss would be the option of a rainwater harvesting system - directing the runoff to a large tank that can be used for flushing WCs, washing machines and the like - you're recycling the water instead of disposing of it.

 

Hi Mike. Don't think most people would want bird poo water for anything but flushing the loo. Certainly not for showering and clothes washing uses about 150 litres a week depending on family. and then there's the cost of filtering if you want to improve the bacterial content....  As my brother says, its not if but how much. 

 

Yes recycling is good but when you do the maths of using 70 litres a day grey water for toilets and, say 100m2 of roof catching say 25mm of rain in one day, this gives you 2500 litres which is over 70 days of water. I could go on about getting lots of rain some weeks and none other weeks but basically it will only really save the additional use of mains water and not really change the rainwater volume when raining heavily because you would need it empty every time it rained.

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15 hours ago, Marvin said:

Don't think most people would want bird poo water for anything but flushing the loo.

The commercial systems are rather more sophisticated than that. Though you wouldn't want to make your tea with it.

 

15 hours ago, Marvin said:

I could go on about getting lots of rain some weeks and none other weeks but basically it will only really save the additional use of mains water and not really change the rainwater volume when raining heavily because you would need it empty every time it rained.

That's why it would need to be a topic for discussion. It may or may not be acceptable by itself or alongside other solutions.

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1 hour ago, Mike said:

The commercial systems are rather more sophisticated than that. Though you wouldn't want to make your tea with it.

 

+1 however the volume of the grey water compared with the volume of rain water off the property are 2 completely different volumes and then you need to ask yourself if the cost value makes sense, and whilst I am pro grey water use I don't think running off the odd m3 when it's tipping down is going to make any significant difference to the flow down the drain. Example: Say 100m2 roof 25mm rain = 25m3..

 

We also use ours for the garden watering....

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Without knowing all the details this is tricky to resolve.

 

However I assume that the authorities  want to restrict  more storm water into the drains, which is normal and understandable.

They will normally allow about 5 litres/ second, but perhaps less, hence the suggestion of storage and a hydrobrake. Then do you still have to pump it up to the uphill drains? Perhaps not.

 

Do you have space for a pond?

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19 hours ago, RichyC said:

'.... Does anyone have any suggestions ...

 

We had a similarly bad perc test.

How flat is your site? If there is a bit of slope and some space maybe you can use some of the suggestions on the SUDS site as @Jilly suggests? We have made a water garden which overflows to a small filter bed, an  attentuation pond and a proper pond which simply overflows down the slope. BCO didn't bat an eyelid.

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If you are short of space then try all means to get a sewer connection, using storage, flow controller and whatever pumps it needs.

 

Bottom line though is that rain currently falls on this site. If you can make it no worse then you don't need to connect to a sewer.

1. soak way, however bad will probably have some sort of flow. If you can make this into a long french drain, it will have a bigger surface area and might find some fissure where trees are or used to be.

2. A pond or lagoon or swale. as well as having some soakage into the ground you will have evaporation, especially if the site is exposed.

3. Some more storage if possible. In its simplest form this is a barrel with the tap set to dribble out over a couple of days.

4. More storage in open texture stone or crates under the parking area and anywhere else.

 

If all that combines to contain all the water on site then everybody will be happy. BUT proving it could be tricky. I suggest giving it a go and proposing it. 

 

If it ever fails and floods onto neighbours or rods you could be in some trouble though.

 

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4 hours ago, Dave Jones said:

A pumped chamber (if no fall) fed by an attenuation tank (cheap crates) would be pretty cheap.

 

We have done something similar in the past.  We used an old well as a chamber that we fed the roof and some other surface water to, then pumped it up to a drainage ditch at the top of the drive.

 

I very wet weather the ditch does fill with water, but it is because other properties did not maintain a culvert when they added their access drives.

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Our GI showed we had clay to at least 5m, and there was no possibility of soak away.  Also no surface drains in the vicinity.  Local water board, allowed me less than 2l per second attenuation.   Our SE charged me to design a storage and hydrobrake, which was complicated and expensive and also hydro brakes apparently are more for developments of more than one house. 

 

We ended up speaking to rainwater harvesting.co.uk, and had a attenuated system with rainwater harvesting for toilets and attenuation to suit the waterboard. Not cheap either. 

 

 

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On 05/12/2021 at 18:27, RichyC said:

I'm not sure where to put this one so hopefully I've got the right forum.ive  Been looking online but can't find an answer. Can anyone offer advise:

 

We had a perc test done which failed and so we're hoping to connect to a combined sewer but the utility company have declined that suggestion telling us we need to connect to a surface water sewer located uphill, 2 roads over and behind 5 other properties. The reason for not allowing the combined sewer access is because we have increased surface water flow from 2x newbuilds on the site. Our structural engineer has been in negotiation with the utility company with a suggestion that we put an attenuation tank with a hydrobrake to reduce flow but its been met with strong resistance.

 

With this in mind I'm not sure what our other options are at this point. Does anyone have any suggestions of any specialist companies we can talk to about this? 

 

 

In our case there was a partly "piped ditch" along/under our side of the road. We proposed connecting to that. The EA said they "wouldn't want us to make flooding worse". So we proposed a rainwater recycling tank with overflow to the ditch. Planners approved it without going back to the EA.

 

My builder also said that in the past he had turned the trench for the foul drains into one large soakaway that conveniently runs off site. He said the main sewer was also beded in gravel so the whole village became a soakaway. 

 

A soakaway mound might also be an option if there is enough space and the ground isn't totally impermeable.

 

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