Suds for dummies

[Danny68]

As  part of our planning permission we have to submit a Suds assessment  and drainage plan / design , reading an old post from Jilly I believe its an exact  copy and paste job from the planning officer of whats required. My issue is  my plot is for all  intense and purposes a slope,  from the roadway the existing bungalow is approximately  1 metre lower dropping another 13 metres over the next 100m until it reaches woodland and has a final sharp drop of 5 metres . Houses either side ( the plot is 22.5m wide ) broadly follow the same route.  I'm not sure what my question is because the water is only going in one direction what ever I do . How would you hubbers deal with the issue . I have a couple of quotes from suds specialist but thought I would ask on here first .Thank you.

P.s I've tried and I don't understand  qbar etc.. 

[ToughButterCup]

There's loads of online guidance about SUDS schemes. Choose one and adapt it to your plot.

 

Our BCO  could not have cared less about what we did. Didn't ask, didn't look. 

[Danny68]

With me its more a case of  not knowing how to convey the information  . I'm more than happy to run drains to the garden  to run down hill via soakaway crates although personally I can not see of any ecological or practical benefit ( heavy flint and clay soil ) doing that over letting them  run surface over the garden . I'll try and find some case study submissions to planning to work out a template .

[Jenki]

5 hours ago, Danny68 said:

With me its more a case of  not knowing how to convey the information  . I'm more than happy to run drains to the garden  to run down hill via soakaway crates although personally I can not see of any ecological or practical benefit ( heavy flint and clay soil ) doing that over letting them  run surface over the garden . I'll try and find some case study submissions to planning to work out a template .

The benefit of soakaways is to slow down large deposits of rainfall to help reduce flooding down stream so to speak. just letting it run can have massive consequences in lower lying areas.  

 

[Pocster]

SUDs can be bollocks also .

The BCO wanted the soakaway to be 10metres from any boundary or building ( including our build ! ) . That made it impossible. So they took my cash for this but ‘agreed ‘ I hadn’t meet the SUDs obligation. So that aspect would never be signed off - yet I carry on anyway 🤣 

Reality is if I sold a solicitor would pick on this and you just take out insurance to cover this ‘ situation ‘ .

So it depends how hard you kick your BCO - I kick mine with a metal boot .

Edited June 15, 2022 by pocster

[Roger440]

1 hour ago, Jenki said:

The benefit of soakaways is to slow down large deposits of rainfall to help reduce flooding down stream so to speak. just letting it run can have massive consequences in lower lying areas.  

 

 

This ^^^^

 

Except if on clay, its an attenuation chamber you need.

[joe90]

I also am on clay and BCO said “where are going to put your soakaway” I replied “you mean pond, we are on clay and it will not soakaway”, I explained that any rain falling on the plot would eventually run to the ditch along the bottom of the plot , so  I piped it there. I would get your BCO out and see what he suggests. ( no two BCO,s read the regs the same, I was lucky).

[Danny68]

3 hours ago, Jenki said:

The benefit of soakaways is to slow down large deposits of rainfall to help reduce flooding down stream so to speak. just letting it run can have massive consequences in lower lying areas.  

 

That's the point I have nothing but woods at the bottom of my garden , the geography of my land and the woods means I could have rain for 40 days and its just going to run away east for 150m then north for god knows how far.  

[SBMS]

2 hours ago, Roger440 said:

 

This ^^^^

 

Except if on clay, its an attenuation chamber you need.

We had to have this. Attenuation via stone system with a hydro brake to slow discharge into the ditch. On clay. 

[Roger440]

49 minutes ago, Danny68 said:

That's the point I have nothing but woods at the bottom of my garden , the geography of my land and the woods means I could have rain for 40 days and its just going to run away east for 150m then north for god knows how far.  

 

The principle is, water doesnt leave your property any faster AFTER you have built than it did before.

 

Even rain landing on a sloping field will take time to get to the river, what doesnt soak into the ground. If its a field the top surface will be absorbent to some degree.

 

If you just pipe it from your roof to the river, it will get there much quicker and contribute more to a flood condition than if your house wasnt there.

 

I'll admit to it being a subject closer to me than most as i have a river in my garden, which has paid me a visit. What really frustrates me is that often, compliance is simply not there. Even when it is, ridiculous ideas like permable paving, which EVERYONE involved knows wont stay working without reguatly being dug up, get implemented. Box ticked, job done. But its not really. Just a handy get out.

 

Meanwhile, the risk of flooding just keeps going up. Because people keep allowing run off into streets rivers etc.

 

Rant over.

 

You need an attenuation system. If you get away with less in your situation, you have simply worked round the requirements and contributed to the problem.

 

Edited June 15, 2022 by Roger440

[saveasteading]

51 minutes ago, Roger440 said:

water doesn't leave your property any faster AFTER you have built than it did before.

Exactly, and you can design on this principle without having to get technical with rainfall and soakaway rates.

It is a bit of an enthusiasm come bugbear of mine.

You have land so this is relatively straightforward.

 

Do you want to achieve SUDS because it is a requirement, or because it is s good thing?

 

If the former then you do, or get someone to do, sums for you, then put in crates and hydrobrakes and so on a considerable expense, knowing that nobody will check the construction or flow off site.

 

If the latter then it is often easier and cheaper, but don't tell the planners or bco.

 

I have designed and built a 500m2 roof area plus parking with zero water to sewers where there was a perfectly good drain in the road.  The area floods badly yet the planners allow 5litres/second per acre off site, and I wanted to prove that this was unnecessary.  This results in much reduced rates as a bonus.

 

The world didn't change but I was pleased with it.

You do need land.

 

The hierarchy is published, with green roof at the top, but that costs a lot.

Then comes rainwater harvester, which I do recommend.  Again capital cost but payback can be about 8 years.

But the unscientific and cheap 'secret' is to put all the drains through porous pipes to soakaways, and have one or more lagoons or swales for whatever gets through.

 

As Roger 440 says, the rain falls on the rest of the land as it always did, and so you are only dealing with your roof. Plus any hard paving but that is easy to resolve.

 

If you can spread the rain in several directions to various soakaways and ponds it helps lot. 

 

1. Barrels on each rwp. 

2. various perforated drains in different directions. Take them through tree/bush areas where the plants will drink the water (not in winter) and the roots have broken the soil and encourage infiltration. Then don't call them perforated drains but 'infiltration trenches'.

3. soakaways and ponds at the ends. Infiltration trenches if flat will hold large amounts of water and have a very big surface area.

4. willow trees at the ponds.

 

The final ponds will work best if big and shallow as there is a large soakage area, and a large surface area for water to evaporate from heat and wind.

 

The final statement of your proposal is 'zero rainwater leaves the site'.

 

As you are retaining all the water, it doesn't need complex analysis, just local rainfall figures.

 

 

[Danny68]

Thank you safeasteading for the comprehensive reply there's definitely bits to take away and incorporatein to the scheme , I think I'll use my haphazard approach to the planning to get through it . I take offence that Roger quoted 

"You need an attenuation system. If you get away with less in your situation, you have simply worked round the requirements and contributed to the problem" I don't think an attenuation system is necessary because of the site layout 

The footprint of the building I'm knocking down is comparable to the one being built . On top of that I will be removing in excess 180% of hard standing across the plot footprint and approximately 65% of cubic mass  and the existing rwp will no longer  run into the main sewer.

 

 

[Roger440]

8 hours ago, Danny68 said:

Thank you safeasteading for the comprehensive reply there's definitely bits to take away and incorporatein to the scheme , I think I'll use my haphazard approach to the planning to get through it . I take offence that Roger quoted 

"You need an attenuation system. If you get away with less in your situation, you have simply worked round the requirements and contributed to the problem" I don't think an attenuation system is necessary because of the site layout 

The footprint of the building I'm knocking down is comparable to the one being built . On top of that I will be removing in excess 180% of hard standing across the plot footprint and approximately 65% of cubic mass  and the existing rwp will no longer  run into the main sewer.

 

 

 

You are easily offended!

 

However, you did fail to mention some of those key details!

[saveasteading]

I should clarify that I think as a contractor as well as designer, so the savings (shared client and ourselves) are significant in designing out the commercial products. If only a designer then it is prudent to  be more conservative, as there is a small fee available compared to the risk of going unpaid or being sued if it does not work as hoped.

Plus it is an interesting challenge.

Plus I really don't think any new development should be allowed to add to flood risk at all. Upstream developments (by the big developers usually) cause flooding and damage downstream, which is entirely unfair.