Question ref soak pit

Tim Robbins

Hi,

in the quote we got from the builder it included a cost for the soak pit /drainage. I understand this is need in new extensions correct?

Is there a test e.g. percolation or something you need to get done first or are you better off just building it?

If you need the test should it be done before the building starts or during.

Many thanks

DOCARCH

Is the soakaway proposed/conditioned as part of your planning permission?

The soakaway needs to be constructed in accordance with BRE 365 and needs to be min. 5 metres from any structure and min. 3 metres from any boundary.

A soil infiltration test needs to be carried out. The results of same will determine the final size of the soakaway. Normally engineer looks at results and then specifies the final size of the soakaway. At least that's the way it works for me!

As to when this is done depends on your planning permission. Have a look at/read the conditions. Some local authorities now require the soil infiltration test/final soakaway design/sizing to be carried out prior to commencement (and detail confirmed to them). Other local authorities do not, so normally contractor (while on site) can do soil infiltration test (to engineers instruction) and final size of the soakaway confirmed (on site).

Tim Robbins

https://www.boards.ie/discussion/comment/119487706#Comment_119487706

Thanks. How much does a soak infiltration test cost? And who typically does it? This is for a house extension, two story and 60 square metres.

DOCARCH

As mentioned, I would often specify the builder carries out the test (in accordance with BRE 365 and generally to engineers instruction) and builder reports results back to the engineer (for final design/sizing of soakaway).

If you google, there are companies out there who will carry out the test.

standardg60

Some light reading for you OP, soakaways are a lot more complex than digging a hole in the ground. If you don't have the right conditions you'll end up with a swamp for a back garden every Winter. Needless to say through experience i'm not a fan of them.

https://www.engineersireland.ie/Covid-19-information-base/soakaway-design-and-construction-an-overview

Tim Robbins

https://www.boards.ie/discussion/comment/119512100#Comment_119512100

What suggestion do you have as an alternative @standardg60 ?

standardg60

What does your planning dictate?

muffler

https://www.boards.ie/discussion/comment/119523592#Comment_119523592

Better still what does his engineer say?

Tim Robbins

Spoke to engineer today who thinks soak pit is unnecessary

muffler

https://www.boards.ie/discussion/comment/119527774#Comment_119527774

Im confused. Why all the questions if you have an engineer on board who is familiar with the property and planning conditions (if applicable). Are you seriously expecting more definitive answers from strangers on an online discussion forum who havent a clue as to what your soil conditions are like?

DOCARCH

Going back to my question in post #2...

Is the soakaway proposed/conditioned as part of your planning permission?

standardg60

https://www.boards.ie/discussion/comment/119528107#Comment_119528107

The expression 'pulling teeth' springs to mind

Tim Robbins

https://www.boards.ie/discussion/comment/119530594#Comment_119530594

The person who did our planning permission was not a qualified architect or engineer and also has a friend who does the tests for you in your garden. No-one I know who got an extension did this. It seems like over engineering.

Tim Robbins

https://www.boards.ie/discussion/comment/119527814#Comment_119527814

I like to do a bit of research so I can ask questions. There are few spoofers out there and everything is extremely expensive so no harm doing some research,

standardg60

https://www.boards.ie/discussion/comment/119534374#Comment_119534374

Jeez OP you've been asked a couple of times now whether a soakaway is a stipulation of your PP, why is it so hard to answer that?

If you've access to a storm drain it shouldn't be, that's where you start, never mind what your builder says

DOCARCH

No idea of your location, but in most of the Dublin LAs, for planning, if you do not propose a surface water soak away, or other means to deal with surface water drainage within the site, it will either be requested that you show them/propose to them how you will deal it, either by means of a request for additional information or submission for approval prior to commencement.

@Tim Robbins if you have not proposed a surface water soak away as part of your planning application, read through your planning permission conditions and see if it says anything with regard to a surface water soak away and/or surface water drainage.

standardg60

Maybe I'm wrong Docarch but I thought the new regs were to do with the fact older parts of Dublin don't have storm drains and all the surface water originally ran into the sewer system?

DOCARCH

https://www.boards.ie/discussion/comment/119537296#Comment_119537296

Applies to newer parts of Dublin too, where there are storm drains/separate surface water drainage systems. They are overloaded with surface water so policy is with any new development to attenuate as much as possible within sites.

standardg60

Very good thanks, thought the issue was only to do with the sewage treatment plants being overloaded

DOCARCH

https://www.boards.ie/discussion/comment/119537551#Comment_119537551

And that too!

The storm drains/separate surface water drainage systems in the past discharge to rivers/watercourses so increased run off from new developments just means more water and potentially more flooding somewhere down the line.

Tim Robbins

https://www.boards.ie/discussion/comment/119534495#Comment_119534495

My apologies.

A soak pit was proposed as part of our planning permission.

The grant conditions included this:

"The applicant is requested to submit a surface water drainage proposal, following the principles of Sustainable Drainage Systems (SuDS) and in compliance with the principles outlined in the GDSDS (Greater Dublin Strategic Drainage Study) Regional Drainage Policies Volume 2 New Development, Aug 2005."

The structural engineer is saying he doesn't think a soak pit is needed and another approach e.g. water harvesting is better as we can use the water to water the trees in our garden.

Another condition states this:

"A separate charge will be levied by Irish Water in relation to the provision of water and/or wastewater treatment infrastructure and connections to same. Further details are available on the Irish Water website www.water.ie, Tel. (01) 6021000."

The suds test can be 1K, building can 2.5K and it doesn't seem like a good use of money so hence I am trying understand more, options etc. Part of me thinks it was a mistake to suggest a soak pit in the planning application.

Tim Robbins

@DOCARCH @standardg60 thanks for your earlier contributions. Much appreciated. Wondering if you have any other wise words?

DOCARCH

Sounds like your planning condition leaves the requirement for a soakaway open. Really up to you engineer now to come up with a proposal that will satisfy the SuDS/comply with the principles outlined in the GDSDS which may or may not include a soakaway.

Tim Robbins

https://www.boards.ie/discussion/comment/119606047#Comment_119606047

And apols for silly question but he looked at it and thought soakway was over engineering.

But no mathematical calculations per se. Do mathematical calculations have to provided to the council and at what point?

muffler

https://www.boards.ie/discussion/comment/119606283#Comment_119606283

Why aren't you asking your engineer these questions? As previously advised you need to talk to your engineer or architect as your query is site specific and no one here can help you comply with planning and building regulations. There is no one size fits all in this context.

From all your previous questions it looks like you haven't engaged anyone and are trying to do a DIY job. Let me give you one bit of advice ...you will regret this.

DOCARCH

https://www.boards.ie/discussion/comment/119606283#Comment_119606283

A soakaway is not over engineering. Really quite simple/straightforward technology if you have the garden/site to accommodate it. If you or your engineer do not want a soakaway, you or your engineer are going to have to come up with and propose alternative means of attenuating surface water run off (like starting to look at green roofs, water butts, water storage, etc.). If you have engaged an engineer, they really should be advising how to comply.

Tim Robbins

https://www.boards.ie/discussion/comment/119606368#Comment_119606368

We have an engineer engaged. As I said the person who did our drawing was a planning consultant and not an architect. So we got conflicting opinions.

My own view is the planning application never should have mentioned a soak pit and it should have been left to the planning authority to specify what they wanted and for the engineer to design it as such. Instead the planning consultant has specified something that we got a few conditions regarding and the engineer thinks we shouldn't need this. Now you might say, why didn't you discuss this with the planning consultant well I didn't realise it was going to cost up to 4K between tests and build? I also didn't think the council would see it and then start asking us for more things.

Boards.is is to get advice and give advice. My experience would be to engage the engineer earlier than we did and don't specify soak pit in your drawing. Now we have been chasing up with the council for over a month trying to figure out more info on what they need but got nowhere. Similarly, I'm grateful for any advice here. Has anyone else been in a similar situation?

I don't want to go the expense of a soak pit if it is not necessary especially at today's prices.