Build over agreement

Londongirl007

Hi 
I'm looking for advice/experience from anyone in a similar situation to my own.  Can I firstly say that I would appreciate comments but please no "shoulda, coulda, woulda" comments, as this would not help me at all and I really need advice on a constructive way forward.  Basically, I bought a property that I am extending which I knew already  had an extension built in 1989, before the Thames Water adopted the sewers.  Plans were submitted and passed.  We demolished the existing extension and proposed to build a new one in its place.  When we started the work, we found a manhole had been built over and covered up.  I left it pretty much to my builder so he dug new foundations and found the sewer pipe would cross over the new wall.  The building inspector came out a passed the foundations up to DPC level, so I thought all was OK.  He saw there was a sewer pipe there and knew we would fill the trench, so it was filled with a lintel over the sewer pipe...all passed.  Then I discovered that TW adopted the sewers and I discovered I would need to move the manhole as it would be in the proposed new extension.  The problem is, I have gone so far with the build and do not have a build over agreement in place.  The sewer is not on the sewer maps so I now don't know if TW are even aware of the sewer and I don't know what to do about progressing with the build.  I have not touched the manhole or done an over site as yet.  I went onto TW website and answered all the relevant questions to assess eligibility for a self certified build over and, as I understand it, the answers I gave are inline with a self cert, but it came back with an answer that I need to apply for full build over...which is a bit late now and it will have to be retrospective as I have already built above foundations and up to first floor. 
Has anyone been through something similar and can advise what experience they have had and what you did about this? What TW are likely to say or do? Do they give retrospective build overs?  I know I probably should not just ignore the problem and carry on and move the manhole etc but the Building inspector has already passed the foundations and lintel with DPC.. Any helpful advice would be very much appreciated.
Thanks in advance.

Jeepers_Creepers

When we had PP for our new extension, our local WB got in touch with us automatically as there is a shared sewer running under our proposal - it must be something the planning dept do as a matter of course. The WB sent out a plan showing the location of the pipe, and their guide on what we had to do (eg CCTV report to prove condition of pipe, etc).

From what you say, it would seem as tho' your WB doesn't know about this pipe of yours... 

Ok, what's the worst case scenario?! They insist you build a new manhole outwith your extension? Could this be done - is there room? If so, I have to say that, in your position, I'd be tempted to just continue on that basis... Ie - if you let them know, almost certainly they'll insist on this new manhole. Whereas if you build over it - take photos to show it already had been - the chances are it'll never be an issue, just like it hasn't been up until now. Ie - you'll 'get away with it'. Of course, if the pipe becomes blocked, then you may well need to add this other manhole, but that's no worse than having to do it now and holding the work back. 

The good news is that the BCO has approved how the founds have been built over the actual pipe - that's an important point. (Did the BCO know of the presence of the manhole? If not, keep schtummmmm).

Do you know where the next manhole is? In a neighb's garden? Ie, in the highly unlikely event that it does block, could it still be accessed without a new m-h on your property?

Londongirl007

Hi Jeeprs
Thanks for the response.  Yes, the building inspector has seen the manhole because it's slap bang in the middle of where my kitchen will be.  He has told me that TW will not allow manholes to be kept in side the extension in case it blocks and they cant get access.  My problem is that I have done a lot of the work without obtaining a build over agreement as (I know this sounds ignorant) but I honestly didn't think I needed it because the BI signed off the foundations and, at that time, I did not know there was a manhole where my new kitchen would be.  It's a bit of a mess now as I will need to everything retrospectively and wondered how TW are with regards to that.

DevilDamo

As TW have still only ‘quite’ recently adopted the majority of private sewers, they are very amenable to such situations, so explain it to them and see what they suggest in going forward.

You can apply for a BOA retrospectively and depending on the type and size of sewer, they may request for it to be CCTV’d. Again and depending on the type and size, it ‘may’ require some kind of legal agreement but this is only in exceptional circumstances where the extension is over a larger 225mm dia. sewer for example.

You (and the BCO) are correct in stating that TW would not accept an internal manhole for access. Is there space to provide another manhole on the line of the existing sewer (which would have to be to an adoptable standard) or one which is offset from the line of the existing sewer (which would not have to be to an adoptable standard)?

Jeepers_Creepers

What's your actual concern, Londongirl? That TW won't give you a build-over consent or that you may need to build a new manhole? If the former, the chances are that they will allow it, providing you can demonstrate that the current pipe is in good condition (CCTV report). If the latter, is this something you could do - is there room outside the extension for this?

If they say 'No prob - build over but follow these guidelines', then great but you'll almost certainly need to fit a sealed cover on the existing manhole to prevent any possibility of pollution under your floor should the pipe block in future. But if they insist that a new manhole is required outside the extension footprint and if there isn't room for this, then they might well ask you to redivert the whole pipe outside the extension footprint instead.

Having said all that worrying stuff, it could well be ok even if the pipe is found to be in poor condition - TW themselves are surely responsible for it?! But who knows how long they'd take to replace/repair it.

As you can see, I don't have an answer for you, only lots of options/scenarios. When you say "The sewer is not on the sewer maps so I now don't know if TW are even aware of the sewer...", how certain are you of this? 

It's not for me to suggest what to do - that has to be your call - but I would feel it pretty unfair to find that someone else had built over a pipe with an extension with no issues, and now you are in the dilemma of what to do in exactly the same situation! And your build is being delayed whilst you figure out how to sort this out?

I think I'd personally be tempted to have a CCTV survey carried out, and if the pipe is in good condition to not worry about it. Seal over that manhole cover and plead ignorance in the infinitesimal chance that anything should go wrong with it later on; you have evidence that it's been covered for many years, and you have evidence that you took all precautions to build over the pipe using the correct foundation methods. If the actual pipe is in good condition, then the chances of anything going wrong is tiny. If the pipe is in poor order, then it needs replacing before you go any further. 

It might turn out well if you contact TW, or it might possible turn into a bit of a 'mare.