Diversion of water main and foul sewer?

Vim Fuego

Looking to build an extension to a house and today is the day when I was expecting the planning decision to be made.

It came back as a request for further information because our extension would be over a 3 inch water main and too close to a 225mm diameter foul sewer line.

We can't alter our plans to leave the necessary 3m either side of both lines, so I think we are going to have to divert both, requiring the necessary permission to do so from Irish Water and/or a local authority.

Does anyone know how I would go about getting this permission? I can't seem to find anything regarding a diversion on water.ie or on the county council website either. Any idea how long it takes?

Secondly - is this a big job with a large cost associated? I know I will have to have Irish Water involved and probably an engineer as well, so I'm a little worried that it will be make a big dent in the building budget.

Any advice or experience shared would be hugely appreciated.

Calahonda52

What is the setting, urban or rural?

What is the invert level of the sewer under the proposed extension

Even if it were possible to divert the 225mm sewer, which may not be the case, have you enough room on your property to divert and still meet the 6m wide way leave?

Vim Fuego

Calahonda52 wrote: »

What is the setting, urban or rural?

What is the invert level of the sewer under the proposed extension

Even if it were possible to divert the 225mm sewer, which may not be the case, have you enough room on your property to divert and still meet the 6m wide way leave?

Thanks for the reply. It’s an urban setting.

I don’t know the invert level just yet. I would have enough room to divert though. It’s a tiny house on a big plot.

It’s odd as there are quite a few extensions along the same road that are built right over both lines. Perhaps enforcement wasn’t in place in the past.

Calahonda52

What exactly did the RFFI say?

It may be possible to build over them, you would need a specially designed foundation

Vim Fuego

This is the request for further info:

Irish Water’s records relating to the subject site show a 3 inch water main and 225mm diameter foul sewer to the rear of the existing house on the applicants lands. The proposed development will be located over the watermain and over/ close proximity to the foul sewer. The applicant should note that Irish Water policy requires a minimum wayleave of 6.0m (3.0 m either side) for public sewers/watermains. Building over or near a public asset would seriously impede Irish Water's ability to access and maintain the water main/foul sewer and would therefore be prejudicial to Public Health. Failure to comply with Irish Water's requirements will result in a recommendation of refusal. The applicant is requested to submit an alternative proposal that maintains the wayleave as detailed above. The alternative arrangement should be detailed on a drainage drawing, with the wayleave dimensioned. Should it be deemed possible to divert the sewer the applicant will be required to execute a Diversion Agreement with Irish Water.

Calahonda52

okay so the sewer seems to be the real problem.
It may not be possible to divert it as it may upset the fall too much

Vim Fuego

Fingers crossed I guess. It’s a worry as this was going to be the “forever home” after the proposed works. I need to speak to the architect and engineer and see what we can do. I’ve learned a lot of property lessons the hard way over the past few years. I’ll add foul sewer considerations into that.

The tiny existing house is practically derelict and it sits on a great sized plot. Would be a shame to not be able to make something of it.

Vim Fuego

Been doing some overlays with paint, I think I am in trouble on this one:

rayjdav

As per Calahonda above. I would agree to getting your inverts first and then approach I.W. Their diversion agreements are very onerous re detail and legal speak but in fairness I have found that they have become very open to discussion if a sensible working alternative can be agreed. The fact it is a 225mm you can lay it up to 1:200 as per their CoP so that should give you some scope.
Is the middle line above the FS drain or watermains. The diversion of the watermains is an easier job, but they will insist on the more expensive HDPE pipe and works. $$$$$$.
Get your architect to produce a drawing showing sizes and gradients of proposal and note that all works will comply with I.W. details. All info on their webpage

Vim Fuego

The existing house (tiny) is in purple. Proposed extension is in yellow. The site is outlined in red and the sewers + wayleave are the green lines.

Vim Fuego

rayjdav wrote: »

As per Calahonda above. I would agree to getting your inverts first and then approach I.W. Their diversion agreements are very onerous re detail and legal speak but in fairness I have found that they have become very open to discussion if a sensible working alternative can be agreed. The fact it is a 225mm you can lay it up to 1:200 as per their CoP so that should give you some scope.
Is the middle line above the FS drain or watermains. The diversion of the watermains is an easier job, but they will insist on the more expensive HDPE pipe and works. $$$$$$.
Get your architect to produce a drawing showing sizes and gradients of proposal and note that all works will comply with I.W. details. All info on their webpage

Thanks for this detail. The middle line is the foul sewer. The water main runs right behind the existing structure but that is less of a concern as there are many examples on the same street where it has been diverted. Good to hear that IW would be open to discussion if we can offer an alternative. It's down to whether we can afford it at that stage.

Calahonda52

I think, if the diversion is all going to be on your land, then the extension will need to reflect that.

I also wonder why the planning application was submitted without this being though about

Vim Fuego

Calahonda52 wrote: »

I think, if the diversion is all going to be on your land, then the extension will need to reflect that.

I also wonder why the planning application was submitted without this being though about

Have had similar thoughts and will discuss with the architect tomorrow. Seems like a waste of time having not been considered until now.

kieran.

Firstly I would identify the location of the pipe on the site by digging a trial pit on the incoming and out going side of the site. It would not be unusal for the maps showing the way-leave to be wrong. Once you have this information you will be in a much better position as you will know the exact location of the pipe and you will also be able to survey the inverts of the pipe so you will know the gradient of the existing pipe and will be able to work out if it is possible to extend the sewer line and still have the gradients work.

Calahonda52

kieran. wrote: »

Firstly I would identify the location of the pipe on the site by digging a trial pit on the incoming and out going side of the site. It would not be unusal for the maps showing the way-leave to be wrong. Once you have this information you will be in a much better position as you will know the exact location of the pipe and you will also be able to survey the inverts of the pipe so you will know the gradient of the existing pipe and will be able to work out if it is possible to extend the sewer line and still have the gradients work.

I agree with the sentiment here but trial pit is not quite the correct terminology in this case

"A trial pit (or test pit) is an excavation of ground in order to study or sample the composition and structure of the subsurface, usually dug during a site investigation, a soil survey or a geological survey. Trial pits are dug before the construction."

Op: you need to dig a hole down to the sewer pipe and make sure its not damaged in the process, so no driving down crow bars to break up the soil.
It would be easier if you could find two manholes

kieran.

Calahonda52 wrote: »

I agree with the sentiment here but trial pit is not quite the correct terminology in this case

"A trial pit (or test pit) is an excavation of ground in order to study or sample the composition and structure of the subsurface, usually dug during a site investigation, a soil survey or a geological survey. Trial pits are dug before the construction."

Op: you need to dig a hole down to the sewer pipe and make sure its not damaged in the process, so no driving down crow bars to break up the soil.
It would be easier if you could find two manholes

My bad correct terminology is 'slit trench' :D

Czhornet

You could suggest to your architect/Irish Water a manhole to be built on both sides of the extension, this will allow access to the sewer if there was a problem. A concrete surround is a must when building over the pipe, but it is possible to build over it.

Vim Fuego

In this case, I know that one of the neighbours have a manhole in their back garden, but it relates to a separate sewer line which intersects the line which runs across my garden. They must have added it when their house is extended so that suggests to me that it is a possibility.
It looks like we are going to establish exactly where the line runs first of all. The map we've seen may not be 100% accurate. We've also contacted an engineer to look at potential options also. The architect isn't hugely concerned it seems, so I won't start worrying about unknown scenarios just yet.

Thanks to everyone for their replies - very helpful for me to understand more about an area I am clueless about!

Hellohello3

Hi,

Sorry to jump on an old post but I've just found myself in the same position and I'm trying to work out how expensive the diversion or solution is. Did you manage to do it? Approximately how much did it cost if you did?

Vim Fuego

https://www.boards.ie/discussion/comment/123099840#Comment_123099840

I did manage to do it in the end. It delayed me a year or more and added at least €20k in work (excluding legal, engineering and other fees) back in 2019/20 money.

I hope things have improved since then but I never want to have to do it again.