Lead Local Flood Authority and Drains

[Dee J]

Hi just landed here - thanks. Lets leap straight into the drains!

Looking at purchasing a plot with detailed pp. It's a garden plot, on a slope, down from the existing road. Currently the plot contains some kind of sewage treatment for the existing house up the hill. There are three chief areas of concern I need to deal with. Replacement drains system for the existing house (owned by the plot seller), drains for the new-build, and surface water drainage. Solutions for these haven't been included on the plans, but the LLFA have linked a strongly worded consultee comment to the planning consent :-

 

Quote

"I am not comfortable with this proposal but the FRA provides sufficient information for the LLFA to remove its objection, however the following should be noted:

1. The site is within the Critical Drainage Area. Land, the highway and property at a lower level than the proposed site has suffered flooding as a result of surface water runoff. The gradient of the land in the area of the site has contributed to the runoff problems suffered.
2. Due to the problems outlined the LLFA wishes to apply a stricter drainage standard than that proposed in the FRA. Currently a system designed to the 1 in 30 year standard. The LLFA requires that the proposed drainage system must be capable to contain and manage flows up to the 1 in 100 year peak rainfall event plus an allowance of 40% for the effects of climate change. Flow from this system must be restricted to no greater than 1.5 l/sec. revised calculations will be required.
3. Consideration must be given to ground stability and site investigations must be undertaken to ensure that the ground conditions are suitable for the proposed drainage system.

If you are minded to grant this application please apply the following condition to the consent:

Condition: No development approved by this permission shall be commenced until details of a scheme for the provision of surface water management and foul water treatment has been submitted to and approved in writing by the Local Planning Authority. The details shall include:-

A description of the foul and surface water drainage systems operation
Details of the final drainage schemes including calculations and layout
Confirmation from South West Water Ltd that the foul network has sufficient capacity to cater for this development
A Construction Environmental Management Plan
A Construction Quality Control Plan
A plan indicating the provisions for exceedance pathways, overland flow routes and proposed detention features
A timetable of construction including a plan indicating the phasing of development including the implementation of the drainage systems
Confirmation of who will maintain the drainage systems and a plan for the future maintenance and management, including responsibilities for the drainage systems and overland flow routes

Thereafter, the approved scheme shall be implemented in accordance with the details and timetable so agreed and the scheme shall be managed and maintained in accordance with the approved details. Details of the maintenance schedule shall be kept up to date and be made available to the Local Planning Authority within 28 days of the receipt of a written request.

Reason: To prevent the increased risk of flooding and minimise the risk of pollution of surface water by ensuring the provision of a satisfactory means of surface water control and disposal."

 

They are not keen on the development are they?

So who is the professional I should employ to deal with this challenge does 'Civil engineering groundworks and water management' cover it or is there a specific professional body that covers the skill set.

Hope you can help.

Dee

[ProDave]

There is a lot to digest there, and I have to go out just now so can't give a full repply.

 

Tread carefully here. If you make an offer to buy the plot, make it conditional on finding a solution to the drainage issue AND satisfying both building control and planning that the solution is okay.  Drainage solutions can take up a LOT of space on a plot, make sure it will all fit and still leave room for the house.

 

Remember is is possible to get PP for a house that is impossible to actually build.

[AliMcLeod]

4 hours ago, ProDave said:

Remember is is possible to get PP for a house that is impossible to actually build.

 

+1

 

I bought a plot with full PP for a house that had 5 foot 2 headroom in front of an en-suite toilet and where you could not walk around the bed in one of the double bedrooms if you put a double bed in it. We had to go back to full planning.

 

It also happened to show the high pressure 90cm oil and gas pipeline that ran through the border of the plot in the wrong location.

 

I'd too would recommend going for a purchase with conditions.

Edited July 28, 2017 by AliMcLeod

[Jeremy Harris]

I agree with the above, and would add that during the one year delay we incurred between making an offer on our plot and actually completing the purchase I had to do a lot of work to satisfy the drainage requirements.  We were lucky, in that the nearby stream could be used for the discharge from a sewage treatment plant, but we were prohibited from allowing any rainwater run-off from entering the stream (our site is higher than the stream and the lane).  This meant a fair bit of work, including a flood risk assessment that was initially estimated to cost between £4,000 and £6,000.  Luckily I found a loophole; there is no requirement for anyone doing a flood risk assessment to demonstrate any qualifications etc in the subject, so I was able to get hold of a lot of public domain information and write one myself (it probably took a month or so to do, though).

 

The planning permission for the proposed house on our plot could not have been built, as the drawings were seriously in error and the site plan boundary errors were massive, showing that a part of the approved house would be on the neighbours land.  Had we not spotted this, and had the boundaries corrected prior to purchase, we could have been left with a bit of land with worthless planning permission.

 

Finally, it is very likely that South West Water will not allow a combined sewer connection.  They will almost certainly demand that any connection to their system be foul water only, with no rain water run-off component.  This means looking very carefully at the ground permeability and making sure, beyond any doubt, that you can make a soak away solution work, one that will handle the higher than normal flow rate that has been mandated in the planning condition.  If the soil is impermeable, such as clay, there may well be no way to meet the soak away requirement at all, making the planning permission impossible to comply with.

[ProDave]

Is this a condition that can be appealed if you can't meet the extra 40% allowance but could meet the basic 1 in 100 year flood risk?

 

In any event you, or the vendor is going to have to dig a few test pits to establish the soil type and measure the percolation rate before you can proceed.

[Dee J]

Thanks to all who have replied.

I had the feeling that this might be one of the more challenging aspects of the permission.

The foul drain aspect would probably resolve into two single or one shared pumping stations sending waste back up to the public sewer.

More challenging is the requirement about surface water. The plot is on a hillside above a large area of pasture land well above the flood plain - so actual 'flooding' is unlikely - the actual issue is the runoff from the driveway and building and the reduced land area for absorption.

When it comes to building construction too there are likely to be issues removing the existing cesspit / septic tank which is located exactly where a buried portion of the building is located.

Much to contemplate.

Dee

[Jeremy Harris]

A quick, and relatively cheap, percolation test would seem to be a good place to start.  Once you have an idea as to the permeability of the underlying soil you'll be better able to focus on how to deal with the run-off problem. 

 

We fitted a rain water run-off surge storage "tank", 20 Aquacell creates wrapped in terram and buried under the drive.  This porous "tank" holds just under 4000 litres of storm water run-off, and allows it to drain away slowly over a longer period, so avoiding any surface water from running off our land and across the lane into the stream.  The water ends up in the stream, I'm sure, but because it just seeps away under the lane it's not visible and so complies with the rules.

[CC45]

I think I'd be looking for another plot or making the vendor sort out these issues first.  Too much risk for me.

[Ferdinand]

@Dee J

Welcome and thanks fr the full information.

 

I'll do a detailed comment, and I'll be blunt about potential problems - feel free to disagree and put my comments aside, but think carefully.

 

I think there are several questions here:

 

1 - The conditions applied seem to me to be rather standardised and not different from those applied to larger developments. There is no evidence that this Rolls Royce solution needs to be implemented for your single house, just assumptions. Picking up your text and putting it in Google reveals identical conditions for housing estates and Dr's surgeries. It is the sort of thing that may be required when Persimmon want to build 100 houses, but is OTT for here.

 

A Planning Condition has to meet 6 tests (look them up - some info on this thread), including being necessary and reasonable. Since one Planning Decision should not form the precedent for another (that is the principle, but usually they can find some wriggle room to create precedent), there should be scope to argue for adjusting that Condition to reflect your individual application. In reality the original applicant should have nailed these down before it got to a decision first time around.

 

TBH the "40% for climate change" looks like something created during a workshop or pulled out of thin air and applied to yours because that is the default. They need to prove that that is reasonable, and that means a scientific basis; it is possible that such justification exists somewhere.

 

The best way to modify this is to engage with the Flood Authority and get them to change their requirement in your case, and you would need a suitable Ologist for that. Second best is to win an Appeal on that point, but by then you will have sunk more money and time into the project.

 

The normal way I say to find an ologist is to use your Planning Consultant or talk to the most experienced and qualified person (prob. a MRICS) at the local *independent* estate agent. You should get a brief verbal assessment for free and you will be into £500 for a proper memo report on your options, with recommendations. To have the thing renegotiated by your Planning Consultant and Drainage Ologist will be anything from £1-2k upwards - it all depends on how the Authority react.
 

If you end up having to do those elements then they could potentially be in a single report, or very brief, or straight out of your Drainage Ologist's last job. That needs to be negotiated.

 

2 - Relationship with vendor and purchase price/time.

 

Do not be rushed. Time is your friend here ... their Planning Application will soon run out and that puts the leverage more and more onto your side.

 

If there is a desperate competition for the plot from naive idiots then let the naive idiots buy it. There is no reason to jump into a potential snake pit just to get ahead of a person with a death wish.

 

The vendor chickens are going to come home to roost here, because they have left an elephant-sized risk in their plot for sale. You either need that risk mitigated or the money to manage it off the price. To build such a scheme as demanded could be £10k for the design, £10k+ for the ground testing and God Knows how much to build it. If you accept the Flood Authority claims then you could be into 25k or 100k.

 

Require them to come up with a solution and adjust the price to match, and/or retain a sum sufficient for you to manage the worst risk and pay them the difference once you have your Completion Certificate. That sum could be 20k or 100k.

 

In any case I suspect a large garden pond at the bottom will need to be part of your landscape design .

 

3 - It may be that the vendor will refuse to engage with the problem here, in which case walk away. If they do engage you need an enforcible agreement in place (Property Specialist Solicitor - £1-2k or +) while it gets fixed (which will take at least 2-3 months and could be a year), and all that taken into account in the price etc.

 

4 - Wildcard

 

The easiest way to buy this plot may be when the PP expires and they have to take it to auction.

 

5 - On the other hand this could be a situation where you buy it reduced and are able to renegotiate the risks or simply get that condition removed on appeal, in which case you could get an extra £100k of added value for perhaps 10k. OTOH you may do that and lose.

 

You need to decide where you can afford to be on the Risk/Reward spectrum, and how much you are willing to spend understanding this plot. My feel says talk to some professionals, and perhaps pay the £400-500 for a formal short evaluation, then decide on that basis.

 

Do not spend money that you cannot afford to lose on a risky proposition.

 

F

Edited July 29, 2017 by Ferdinand

[Dee J]

Thank you Ferdinand for a most detailed examination of the situation with this plot. Definitely a case of a careful and considered approach required.

Dee