Drainage issues with proposed plot

[lakelandfolk]

Hi,

We are currently in negotiations to purchase a very nice plot but I am struggling to confirm that connection to the public drainage system is 1. viable and 2. even possible.

 

   SURFACE WATER.  The plot has full planning permission and includes an approved scheme to take the surface water across a public highway and discharge it into a drain ditch approx 6 metres from the plot boundary. I have only eye balled the route but feel sure there is no where near sufficient fall for it to work by gravity, the pipe has to be 6oo mm below the road and I estimate the ditch to be about 400 mm deep. By the way,the planners had earlier refused an on site soak away system due to poor ground conditions.

 

FOUL WATER. The nearest public sewer connection is 75 metres down the road but only 1.02 metres deep, the road looks flat and level to me, so again, gravity would not work.

 

My thoughts so far are,    

                                                                                                                                                                                                                                                                                                        Plan 1.    Install an airobic treatment unit and pump both surface water and cleaned foul water across the road and discharged into the ditch. I assume we would need to install a 600 litre holding tank with pump after the treatment unit.  Would we also need a permit from the Environment Agency for this set up?

 

 Plan 2.    Install a holding tank with pump and pump the raw sewage via  a 63 mm pipe to the sewer 75 m down the road and pump the surface water across the road into the ditch

 

  There are surface water kerb side drain gullies the full length of the road and one is situated adjacent to the plot entrance.

 

Plan 3.      Holding tank with pump and 63 mm connection to public sewer 75 m down the road as plan 2 and surface water connected to the road surface water drains.                                                       I am trying to get Highways to meet me on site to investigate that idea, but I fear they might refuse.

 

This issue has the potential to be a deal buster, all of the above ideas would come at a hefty cost or even worse there might be no solution possible to the problem.   We could finish up buying ourselves a very expensive allotment if we are not careful at this stage.

 

My head is spinning and not helped by having to deal with, Environment Agency, United Utilities, Lancashire Highways, West Lancs Borough Council. So far I have been unable to make contact with a suitable professional or contractor with the experience and expertise to guide me through this conundrum.

 

Any help, advice, experiences would be much appreciated, (I need a good nights sleep)

 

 

[ProDave]

Can you post a plot layout with adjacent bits of land and what they are used for? Even something hand drawn would give an idea.

 

Does the vendor of the plot own any other land, particularly any adjoining land, if so what is the present use of that adjoining land.

 

It is building control you need to be speaking to. See if you can arrange an on site meeting with them to discuss options.

 

you say an on site drainage system was refused due to ground conditions. Has a proper percolation test been done, if so post it's findings.

 

I am surprised planning have refused a particular drainage scheme, it's usually the other way around that planning will pass something and you later find building control refuse it. This happened to me and for an anxious few weeks had no drainage solution (= no house) until a solution was found that building control agreed to. that's why it's building control you need to be talking to now.  If building control agree to it, then when you submit your final plans you just describe the drainage scheme and make it clear building control have greed to it.

 

All the schemed you have described would work, but that does not mean they would be allowed.  I did one scheme where they pumped raw sewage up to a public drain at a higher level, and trust me, it's bad news if the pump ever fails, and a very unpleasant job to replace it.

 

If you want to proceed without risk at the moment, make an offer to buy subject to obtaining full planning permission for the house you want AND building control approval to build it.

 

 

[Crofter]

Good idea from Dave there.

My preference would be to pursue the first solution as I would imagine it could be easier to get permission to lay pipes containing treated effluent, rather then raw sewage, especially across someone else's land.

 

If drainage was refused based on site conditions, there are specific ways around things like high water tables, although proximity of boreholes or water courses is harder to do anything about.

[Temp]

Has the current owner had a percolation test done to check drainage is as bad as suspected?

[lakelandfolk]

Hi Dave,

 

I had to install a 600 litre sewage pumping unit myself when I built our existing house 19 years ago. We live in a dip so required an 8 m lift over 80 m into the public sewer and it has worked perfectly since day one, so not concerned on that issue.

 

Strangely  percolation test has not been done and that would be difficult at the moment as the plot has been allowed to be so overgrown that it is impossible to set foot into it. The land along the rear boundary is a market garden and we have already spoken to the owner who has said he would sell us an 5 metre strip to add to the rear boundary. I'm sure he would allow us to conduct a percolation test on his land which should be the same as the plot which was also a garden. The extra strip of land is unlikely to get permission to build on but perhaps we could use it to install a soak away system.  Who is meant to do the percolation test? is that building control?    I have seen a letter early on in the vendors planning application process from the Principal Engineer at West Lancs BC including the following  "the surface water is shown discharging to a soak away to the northern corner of the plot. From my knowledge of the ground conditions in the immediate area, it may be unsuitable to use ground infiltration methods, unless percolation tests prove otherwise"

 

As you suggest I will try to set up a meeting with BC on Monday and take details of possible options, as I see them, and also pursue the percolation test.

 

We would prefer to make our final offer to buy with prior knowledge of the financial implications of the drainage situation 

 

By the way we will be making a new detailed application as the one approved is far too big, ours will be 3 bed 160m2 and what I would call " shoe box shape"

[Temp]

 

11 minutes ago, lakelandfolk said:

 Who is meant to do the percolation test? is that building control?

 

No usually you have to do it or hire someone to do it. The BRE have a guide that explains how to design a soakaway and that includes some info on how to do the test..

 

http://forterra.co.uk/plugins/downloads/files/BRE365.pdf

 

If you hire someone you get a report you can wave at the planners (to get a planning condition removed) and Building Control to keep them happy.

 

You need a digger to make a few holes and it's common to get both a percolation test and a soil condition report done at the same time to save money. The latter may be needed for the foundation design as it includes info on load bearing capabilities, clay shrinkage etc. However if the soil in the are is well know/understood  then you might get away without.

 

May also need a water bowser to fill the hole for the percolation/infiltration test.

Edited October 8, 2016 by Temp

[Temp]

I think it's also possible to have an above ground soakaway/soakaway mound. The idea being to put the water into a large bank of earth that distributes the water over it's footprint (which is much larger than a normal soakaway). Got a feeling someone on this forum has done one? or was it someone on The Green Building Forum? 

 

http://www.moir-environmental.co.uk/pdf/Mound Soakaways.pdf

Edited October 8, 2016 by Temp

[PeterW]

I would go for plan 1 and see if they will let you discharge both the rainwater and treated effluent to the ditch over the road. 

 

Not sure how "legal" it is, but I would try and use a single tank for the treated effluent and rainwater and pump the whole lot as one - it would dilute the discharge and also mean you had one pump to manage. 

 

The downside would be that you would need a holding tank that could take a full rainwater surge which could be close to 2500 litres plus another 4-500 litres of effluent and twin pumps to make sure you had redundant systems. 

 

 

[Temp]

I agree. Plan 1 first and anything else as a fall back.

[ProDave]

7 minutes ago, Temp said:

I think it's also possible to have an above ground soakaway/soakaway mound. The idea being to put the water into a large bank of earth that distributes the water over it's footprint (which is much larger than a normal soakaway). Got a feeling someone on this forum has done one? or was it someone on The Green Building Forum?

 

http://www.moir-environmental.co.uk/pdf/Mound Soakaways.pdf

I was going to use a filter mound, which is a pile of expensive graded sand (would have been about £1000 worth of sand) but between planning and building warrant, building regs changed and whereas it used to only be 5 metres, now (in Scotland) a filter mound must be 10 metres away from a road (and 5 mertres away from a building and plot boundary) and that left me insufficient room.

 

A filter mound is intended for ground that does drain, but the water table is too high for a conventional underground soakaway. You do the percolation test in the same way de determine the percolation rate (and size of the mound) except you dig your 300mm deep test hole at ground level, so perfectly doable with just a shovel, no need for a digger.

 

There are other proprietary systems like the puraflow which discharges into a tank full of peat and then down into the ground, but BC rejected that one for my site without saying why.
 

[lakelandfolk]

Thanks everyone,  I will make sketches of the various ideas, arrange site meetings with BC and County Highways and Let you know how I get on.

[Crofter]

My council's website mentioned a list of BC approved contractors who would carry out perc tests, but when I phoned to ask for this list they sounded very confused and then said they no longer had such a thing, and 'normally your builder does it for you'. So I just did it myself, it's really rather easy, just a bit tedious.

My drainage system is now complete and signed off so there do not appear to be any problems.

It could well vary between different LA areas though.