# Passing a Percolation Test



## GregnGra

We're in the process of planning a self-build and have an eye on a good site. However it has previously had planning refused due to failing a percolation test. As I understand it this means the site is unfit to support a conventional septic tank. What influence would installing a bio treatment system instead have on a future application ie would it make the results of a percolation test irrelevant? If not what would my options be?


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## Ravima

Whatever happend, do not try to fake the results. you will end up with years of hassle and problems. If the site will not drain, then let it go. I speak from experience!


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## GregnGra

What I'm trying to find out is basically what options there are in order to make the site fit to pass the test. What different drainage options are there etc. I'm under a small bit of pressure to make a decision on the site and having walked around it and checked it out at various times (inc after heavy rain) it did'nt seem at all marshy or boggy.


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## Sue Ellen

Hi Greg,

I have moved your thread to the H&G forum as it will probably get more replies there.

There are some previous threads  with references to percolation tests.


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## sydthebeat

GregnGra said:


> What I'm trying to find out is basically what options there are in order to make the site fit to pass the test. What different drainage options are there etc. I'm under a small bit of pressure to make a decision on the site and having walked around it and checked it out at various times (inc after heavy rain) it did'nt seem at all marshy or boggy.


 
not all 'sites' are suitable for housing.
if there is a high water table, or very bad, as in no, percolation, then councils generally refuse any application because of the inability of the site to safely dispose of the effluent, notwithstanding the use of any effluent treatment system.

generally you can get a good idea of the ground conditions by looking at the flora and topography of a site.. ie is there lots of reeds, is it at the bottom of a hill etc..
you will only get a real picture of the ground conditions  once youve opened up a few trial holes.


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## Tulach

Do you what the T value result on the perculation test done previously was? If not you can find out by looking at the previous application in the council office.

If the T Value was a little high you can do things like a raised perculation area with polishing filtration system however these can be expensive and aren't always suitable, as syd says some sites just aren't suitable for waste water systems and some would require far too much expense.

Find out the results and let us know what they are and we'll be able to giev you a better idea but as syd says looking at the site and digging trial holes is the only real way to know.

If an expensive system would allow you to get planning keep that in mind when agreeing a price with the land owner, the site value should not be the same as if the ground was suited to less expensive waste water systems.


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## Tulach

Just one other thing some people think that for a site to fail it has to be very wet, teh oppoiste is true also if the T value was very low it means the water drained too fast and there isn't much wou can do about that, but you wouldn't know that unless you got a test done or saw results of a previous test.


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## daddycool

In all the excitement of a site hunt, I know you can just want a solution but be VERY careful here - again I talk from experience. Your failed percolation test is a RED FLAG and might cause you to buy a garden as opposed to a site if planning never comes through - also if a CoCo had already failed a site on this basis - environment are going to be slow to reverse unless it is really proven 

Your issues are drainage, not a 'how will I pass the test' - regardless of the system you put in (std tank, bio-tank, etc.) it still needs to percolate or drainaway on output and it needs to filter down.  If your failed test is because of a T value >50 (slow or non-draining) then you have an issue.  A raised bed percolation (imported soil or sand polishing filter) will solve this for the initial percolation, but still if the soil below the raised bed still has no drainage, then you are in trouble with ponding - depending on where you are (?) you can divert to a watercourse (Wexford) or not (other CoCos).  

Your 1st port of call is to ask for the failed test report and see what the prob. was - too fast or too slow (too fast drainage also a prob on sand or rocky soils giving immediate access of effluent to water-table).  2nd thing is to dig trial holes prior to purchase - don't buy without doing this - go down 3 m if you can - look at the soil profile and get a test done (reseach how to do it yourself or get a qualified EPA surveyor to do it).  If it passes then buy away - if not BEWARE.  No percolation = no planning - its that simple (or else poo in a bucket - with all the hassle we had with ours getting planning there were days I thought that's what I might end up with!)

If you want to buy, you could make it subject to contract in passing the test (same as subject to contract for surveyor on a 2nd hand property) - definetely give yourself an out - if the site has already failed a perc. test then it is not worth anything for development right now so the vendor should be happy to oblige all this if interested in selling - bottom line advice - walk away unless the test results are positive.  PM me if you want more info.


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## GregnGra

Thanks for the advice folks. The site we're looking at is in Meath. I've been around the site a few time and made a point to do so after rain to see what state it was in. The ground does'nt appear at all boggy. I've seen the previous test holes-they are all at one end of the site, three in total. They're about six feet deep and have a small (3-4 inches) amount of water at the bottom. Anybody have an initial opinion on this? I'll try to find out the last results tomorrow.


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## Tulach

Sounds like drainage is too fast with T value of less than 5 imo


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## daddycool

hmm - disagree - if test holes have water in them then they might be slow draining - do a test yourself - ram a piece of 2X2 in there vertically - pre-mark it in inches - fill it with a few gallons of water and watch the drainage (the actual test is done with pre-soaked holes) - T value is the water level drop over time - I can't remember the formula for T value calc. - have it somewhere - you'll find it on the net anyway - but best to get the report - look at the profile of the test holes - any clay or mottling indicating water holding? If its loose sandy/gravel then OK as long as not fast draining - ultimately if it failed the test it failed the test though ...


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## Tulach

daddycool said:


> hmm - disagree - if test holes have water in them then they might be slow draining - do a test yourself - ram a piece of 2X2 in there vertically - pre-mark it in inches - fill it with a few gallons of water and watch the drainage (the actual test is done with pre-soaked holes) - T value is the water level drop over time - I can't remember the formula for T value calc. - have it somewhere - you'll find it on the net anyway - but best to get the report - look at the profile of the test holes - any clay or mottling indicating water holding? If its loose sandy/gravel then OK as long as not fast draining - ultimately if it failed the test it failed the test though ...


 
LOL he said 3-4 inches of water, my trial holes have 3 to 4 foot in them and had a T value of 28.

Best idea is get old results then you will know for sure what the story is.


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## GregnGra

Checked out the previous test result at the planning office today. The T value was 70. Is this a hugely worrying result-I've been told if had been over 90 to walk away so does anyone think this value means the site is a non starter?


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## Tulach

70?? Thats not too bad but seems unusual if the trial holes only currently have 3 to 4 inches of water in them. Obviously the top soild isn't good for drainage. Be interesting to see a P value.

What size is the site, does it slope or is it flat?

A raised percolation area is an option with a mechanical system.


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## GregnGra

The site is 0.5 acre, pretty much level.


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## Tulach

I take it there is a connection to mains water available and you won't be needing a well?


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## GregnGra

Yes mains water is readily available


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## daddycool

any surface water on site perimeter? stream, ditch, dyke with flowing water?


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## SashaF

Hi,

Apologies for butting in on this thread GregnGra but there seems to be a few people here who seem to know what they're talking about when it comes to percolation tests.

We have a site in Cavan on a sloping hill (not too steep) in a wooded area and overlooking a lake. We have carried out the necessary percolation tests, the large hole filled with water as we stood there!! Problem!! We have since involved an engineer who is proposing to pump the waste up the (slight) hill to better land about 50m away in a field. He is carrying out further percolation tests on this land as we speak. Has anyone ever come across such a scenario?? Are we mad to undertake such a venture?? Will it cost a fortune? I'm not an engineer but pumping waste up to the nearby field sounds like we could have a lifetime of problems???

Any advice would be greatly appreciated. Again apologies for butting in here.


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## daddycool

a load of crap ... literally.. that's what all this is about 

Ultimately you need to percolate somewhere - if your perc. holes filled with water as you watched, then there is prob. a high water table / acquifier or underground springs / streams feeding in.  Diverting these is do-able if it is a small undergraound spring / stream but difficult to know until you open up the ground and may turn out expensive running a land drain around the entire thing as well.  I have a geo-phys. guy involved in my build now for reasons I won't bore you with but he has surveyed the ground and soil to a depth (radar) and can produce 2D profiles of the make-up, water content etc. Invaluable to answer the 'why' aspect of water leakage - if you see a huge watercourse or table under there then you know you are snookered in that location - survey costs ballpark 1.5k and is great for looking at rock, clay etc. so also good for your foundations so get it done for both
.  
Choosing another location sounds fine if you have the space and the soil conditions will be better there - pumping uphill sounds fine (no direct experience) as long as the pump is up to the job and is well maintained / replaced over the years - the consequences of it not working are obvious!  

Ultimately if you can percolate somewhere up-gradient of you, away from neighbouring wells and your own (maybe you are on mains - if not make sure your well is upgradient again from perc. area in my opinion - not absolutely necessary if far enough away but who wants to take that chance!) then it's a fine solution - best of luck with the new tests


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## SashaF

Thanks a million for that Daddycool. I've been getting a liitle bit of conflicting advice in this topic (some of which I believe to be self-serving!!) so its great to get an independent view.

Good luck with your testing too.


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## Shepahoy

Quick question...

Do you did Trial hole yourself or get in an expert?


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## Mr Tayto

> Do you did Trial hole yourself or get in an expert


 
Hi 
I asume you mean dig - no matter who you get you will have to have the trial hole already dug, and have two 44 gallon drums of clean water there for the test, and if the initial T test fails you will have to dig a small 300x300x400deep test hole for the P test

Hope this helps


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## Shepahoy

My Engineer said he will come out and do the test if I get the hole dug, I guess my question is; Can I go and do this with a spade or should I get in a digger etc...

This may seem a silly question, but would save me a few euro if I could dig the hole?


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## sydthebeat

generally there are 5 holes required (depends on you county BTW).

The water table trail hole is 2 m deep by (usually 1.5 m sq)
the 2 T test holes are 300sq x 400 deep, but have to be dug generally 800mm below GL.

If you can do this with a spade then fair dues!!!!!

the 2 P test holes are 300 x 300 x 400 deep, easily done by hand


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## Shepahoy

Yeah 2M is too much to do by hand.
Thanks...


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## Greywolf001

Hi guys ,I just been refused planning application from 3 reasons 
1- because of extra traffic on local road ( but I already renting house next to where I am living in rental house), also I living in lane way and my land is the only one empty part from other 2 houses (I living in one)
2- local house need ( I grow organic products for my family and restaurant   and i need to be there most of the time ) .
3 - public health issue for septic tank ( but It already past the test with percolating value of 30) 
My architect said it is hard to win appeal basis on septic tank. 
Can anyone advice me from your experiences please ,thank you


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