Grian Posted December 7, 2018 Share Posted December 7, 2018 (edited) Hello oh wise ones. Please help me if you can - I have a site, a positive response to a pre-app, and a house design (2 bed single-storey with attic trusses for future proofing) and now I'm looking at my wastewater system before doing anything else. My only option appears to be a mounded system. This is the advice of the consultant who I have used in the hope I will avoid finding myself in a pickle at a later stage... and his solution has been arrived at after discussion with SEPA. It sounds as though this was the only acceptable option. So I'm trying to understand the costs - everyone warns the groundworks can run away with budget and budget is limited. The reason I need the mounded system is that there is bedrock at about 600mm, a purply pink kind of material. The only way is up! Also, to make it more awkward I'm hemmed in by drains to two sides - which ironically I dug by hand to deal with soggy spots / test pit filling (finding a couple of springs in the process - I am a human divining rod). There is a public road with a drain to the third side, and immediately behind there is a tall steep bank. Discharging to low water from a biodisk type system is out - it's a huge tidal drop. I don't think the soil is any deeper on the other side of the public road, though I should dig a hole there, just for completeness as its the only place I haven't dug one. And the boundary of the ROA is immediately to the south, so even if it is deeper over there... which I doubt, its pretty consistent. ...I can redirect the land drains a little, but the rock is a more difficult obstacle. So a mounded system it probably is... I'm struggling to find any information on the potential costs of a mounded system and pump. Never mind the pecking of rock to make way for a low profile septic tank... this seems impossible to estimate in advance. Oh, and I'd be draining grey water to one of my drains, so I'm guessing that complicates the system a little bit and so adds further cost. Also it is on the isle of Mull so more costly for most things. Any information, advice or encouragement welcome. I feel daunted! Apologies for writing an essay on my first post! I can add annotated photos showing where various obstacles are if of any interest... Edited December 7, 2018 by Grian Link to comment Share on other sites More sharing options...
ToughButterCup Posted December 7, 2018 Share Posted December 7, 2018 Right - first off, congratulations on your approach: sorting out the softy and smelly stuff first is quite rare I am told - and I know from experience that it is commonly dealt with last locally. A photo would help - your description is detailed, but the problem needs a good coat of looking at, I think. Link to comment Share on other sites More sharing options...
the_r_sole Posted December 7, 2018 Share Posted December 7, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
ProDave Posted December 7, 2018 Share Posted December 7, 2018 Hi and welcome I researched filter mounds as I very nearly used one myself. They are not that scary. No 1 thing is to do a percolation test. But you don't dig a deep hole as normal, you dig a 300mm cube hole at the surface, fill it with water and time how long that takes to drain away. I can fill you in more on the details as this progresses. This will give you your percolation rate Vp. From this, and the No of bedrooms in the house you can then calculate the area of ground that needs to be covered by a filter mound. This filter mound is just a pile of graded sand of a known percolation rate. Because it is graded it is more expensive than building sand, I got a quote and it would have been about £1000 for the graded filter sand. Add a bit for a ferry ride unless there is a quarry on the island that can supply it. You build a mound of sand, about 1 metre high, on top goes your normal perforated drainage field then the whole lot gets covered in soil, so you have a garden with a bump in it. All you need to know about filter mounds is contained in this little book https://www.brebookshop.com/details.jsp?id=148788 It is only about 25 pages and I objected to paying £2 per page, so I borrowed it from our local library, they got it on an inter library loan for me at a cost of just over £1 for the postage. Once you have worked out how big the filter mound needs to be, you have to work out where you can fit it, given the building regs limits how close it can go to a building and a boundary. It was lack of space in the end that made SEPA give in and give me a permit to discharge to a burn instead. Another tip: Avoid treatment plants that have moving mechanical parts. Trust me, you do not want to be servicing them when they go wrong. Instead choose one that works on an air blower principle like Biopure, Vortex, Conder, Graff and probably many others. 2 Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 Thanks for speedy and encouraging replies! Quite simply I can't afford a nasty surprise once underway. Funnily I was worried about groundwater, and believed I was over rotten rock since this was at the bottom of my other test pits. Seems to be a seam of rock running along the land at this level... Oh a book. Fabulous. And that mound sounds quite do-able. I feel less daunted already!! Hokay here are images 3 and 4 of 6000000... Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 (edited) There is a fair bit of space to the north of the drain, but I'm trying to keep the access road as short as possible to minimise cost, and there is the only one point at this end of the plot providing the required visibility splay. Also to show how much water is in the drain, I don't know the flow rate required for the grey water discharge but it has run like this since dug in early autumn. eta, please ignore proposed house label, that is now proposed parking!! Edited December 7, 2018 by Grian error Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 Bedrock. I am on an awkward seam it appears. Any geologists who might comment on what it is and whether it is nice and easy to peck out and won't take a digger 5 minutes... ? Having hand dug most of the other holes it was quite amusing to have a huge powerful digger come and make the smallest hole around! Ok, no more photos I promise. Its just so exciting to speak to people who can help! Link to comment Share on other sites More sharing options...
ProDave Posted December 7, 2018 Share Posted December 7, 2018 I would move that land drain you have dug ASAP right up to your plot boundary, and fill in the ditch you have already opened. The problem you have is a filter mound needs to be 10 metres from a watercourse, and if SEPA decide that is a watercourse that excludes a large chunk of your land from being usable as a soakaway. There wasn't a watercourse there before you dug it so make it so again. I would be inclined to dig a land drain right around the whole perimiter of your site, fill it with rock, making it a French Drain, and cover with geotextile and a thin layer of soil. Make it run into the roadside drain, as inconspicuously as you can. 1 Link to comment Share on other sites More sharing options...
joe90 Posted December 7, 2018 Share Posted December 7, 2018 Not sure if it’s applicable to you but I installed a vortex and drained it via a 10m rumble drain (trench dug and filled with 50mm stone with perforated pipe In it from plant) and drained it into a ditch that is dry about 2 months a year. The ditch immediately drained into a roadside drain fir about 30 meters then to a small stream (shows as a feint blue line on OS maps). When I applied for the permit I could not name the watercourse and they deemed it drained to the Tamar (which is miles away!). Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 (edited) 13 minutes ago, ProDave said: I would move that land drain you have dug ASAP right up to your plot boundary, and fill in the ditch you have already opened. The problem you have is a filter mound needs to be 10 metres from a watercourse, and if SEPA decide that is a watercourse that excludes a large chunk of your land from being usable as a soakaway. There wasn't a watercourse there before you dug it so make it so again. I would be inclined to dig a land drain right around the whole perimiter of your site, fill it with rock, making it a French Drain, and cover with geotextile and a thin layer of soil. Make it run into the roadside drain, as inconspicuously as you can. Unfortunately I think they may have been furnished with all this info in the discussions with the consultant... at least that means the solution takes that into account. I expect they'd intend me to divert it if I went ahead. I do aim to divert the one I dug to the north as far as possible but there is a pokey-out bit from the bank just beyond the 3rd photo that means it really can only go that far then has to head down slope to the roadside ditch, but it should be feasible to move it at least 10m from the area I marked as a potential soakaway spot... I had to drain the area as nearby holes kept filling with water. Now I have moved the house thats not a problem - I was trying to avoid the ugly electric pole you see. The other drain that I dug to the south can also be diverted but it probably hasn't any relevance. The roadside ones are outside my jurisdiction, unfortunately! As is that electric pole, the bane of my life... I haven't signed an agreement over way leave yet but SSSE pretty much advised that was where it would be agreement or none! Thanks Joe, thats something to consider. Edited December 7, 2018 by Grian more info! Link to comment Share on other sites More sharing options...
ProDave Posted December 7, 2018 Share Posted December 7, 2018 I am not sure SEPA will allow discharge to a dry "watercourse" It is a lot harder to get a discharge permit from SEPA than it is the EA in England and dilution rate is one of the things they look at. If there is no flow, there is nothing to dilute it. Link to comment Share on other sites More sharing options...
joe90 Posted December 7, 2018 Share Posted December 7, 2018 Did @Grian not say that the drain (ditch) he dug is flowing and he found a couple of springs? I have heard that Scottish permits are more difficult than down here. If he could discharge to that ditch he could have a pumped outlet to raise the output to that required. Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 (edited) 3 minutes ago, joe90 said: Did @Grian not say that the drain (ditch) he dug is flowing and he found a couple of springs? I have heard that Scottish permits are more difficult than down here. If he could discharge to that ditch he could have a pumped outlet to raise the output to that required. She did. The flow from the springs is in the south ditch/drain and is a little more than that of the drain pictured, but not a great deal. It does sound as though the mound is a manageable option. I need to investigate how much for sand, and how much sand... so perc test next I think... Edited December 7, 2018 by Grian more info 1 Link to comment Share on other sites More sharing options...
newhome Posted December 7, 2018 Share Posted December 7, 2018 1 hour ago, Grian said: As is that electric pole, the bane of my life... I haven't signed an agreement over way leave yet but SSSE pretty much advised that was where it would be agreement or none! For a different day / post but several people on here have challenged such things and have been successful. Do you have a quote for the electricity connection yet? Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 11 minutes ago, newhome said: For a different day / post but several people on here have challenged such things and have been successful. Do you have a quote for the electricity connection yet? I do thanks, an informal quote for 5k to bring it from a transformer about 65m away. Link to comment Share on other sites More sharing options...
newhome Posted December 7, 2018 Share Posted December 7, 2018 10 minutes ago, Grian said: I do thanks, an informal quote for 5k to bring it from a transformer about 65m away. Ah well that's not as expensive as many have been quoted (ie some have had quotes 5 times that). As to whether that's the right ballpark for that distance someone else may be better placed to comment on. Link to comment Share on other sites More sharing options...
PeterW Posted December 7, 2018 Share Posted December 7, 2018 19 minutes ago, Grian said: I do thanks, an informal quote for 5k to bring it from a transformer about 65m away. Thats cheap ..!! Does that include trenching the cable ..? Link to comment Share on other sites More sharing options...
Grian Posted December 7, 2018 Author Share Posted December 7, 2018 2 hours ago, PeterW said: Thats cheap ..!! Does that include trenching the cable ..? No, that isn't included. Just connecting and the cable. Link to comment Share on other sites More sharing options...
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