. Full drainage design suite (50% Discount) including 7 spreadsheets; Soakaways built in Clay Soils need to be carefully designed in order to operate effectively due to the low infiltration rate of most clay soils. A traditional soakaway will have a ratio at the higher end of scale where it drains a road or several houses. Alternatives for Heavy Clay Soil. Clay soil is sticky and forms thick lumps when it gets wet; Clay soil can become rock-hard in dry conditions; Clay soil does not absorb water quickly leading to stagnation; Clay soil is significantly harder to cultivate as compared to other soil types; Clay soil warms quite slowly during spring but can retain more heat during winter. Make sure your pipe slopes towards the soakaway. Once wetted by winter rains, clay soils often cannot be worked or walked on until mid-spring. g. It’s most commonly used as an alternative to perlite for its. The waste water from the biodigester is us. One of the drains at the front of the house leads to a soakaway which was quite old and flooded when the rain came. The liquid is passed through a soakaway system and is discharged into a drainage field. 4 x190l (1000x50x40mm each) crates wrapped in geo fabric (french drain pipe into here) back filled around and on top with 10-20mm gravel. In Australia, a soakwell is a large underground plastic or concrete tank that connects to your roof drainage system. W. This is measured below the pipe invert so you' generally dig 1. 24 30 1. In addition, gravel helps to provide stability, reducing issues such as erosion. Soakaway Nightmare, Clay Soil. 7 Mar 2015. 0 m), and soakaway sediment were used for this study. See more of Cesspit on Facebook. * Dig a much bigger soakaway. Jan 20, 2015. Garden or driveway soakaways are usually much smaller than. Area (A) = V x P x 0. A Soakaway must be at least 5 metres from any habitable building, by local authority regulations. We have a blog post on how to perform a percolation test here. A soakaway can be left open, filled with small stone or river rock, or filled with rock and then covered with a layer of sod or soil. When installed correctly, French drains can redirect water to a designated location, such as a soakaway. A deep bore soakaway is a special type of rainwater soakaway consisting of a conventional chamber and a narrow bore perforated liner extending to the infiltration medium. If you're going for traditional. This closes the pores and fissures at the excavation interface leading to. Safe-T-Sorb (STS) from Tractor Supply. 25 for septic tanks. The pipe end entering the soakaway must be at a depth of 25mm minimum and the end of the pipe cut at 45°The current study aimed first to examine the mobility characteristics of Cu, Zn, and Pb through soil and soakaway sediment using an integrated analytical approach for column leaching with. The permeability of the soil is akin to the size of outlet in the system I proposed above. Water drains very slowly through clay soil. Use a loose, organic-rich soil when building berms to enhance drainage. Step 2 – Prepare the crates. Rebekah PooleOk well. This can vary slightly depending on the soil conditions around the soakaway. some sandy soils), or soaks away too slowly (e. Coarse Sand. How to Build a Soakaway in Clay Soil? A soakaway is basically a deep hole filled with rubble. . When a soakaway has blocked and flooded we can attend your property and provide a report. 0 views, 0 likes, 0 loves, 0 comments, 0 shares, Facebook Watch Videos from Soakaway Worms: septic tank soakaway clay soilDig a hole into the soil approximately 60cm (2 feet) deep; Fill the hole with water and leave it for four hours; If the water is still there after four hours, then it’s a good sign that you need drainage. The soil was available in powder form with particles smaller than 75 µm. If a soakaway is impossible to achieve, you may be able to discharge the water into a local watercourse if you live next to one. 8m deep. clay lumps and friable particles. Replies 20 Views 40K. A soakaway is part of the Sustainable Drainage Design. This can be an expensive and arduous effort but is generally fool proof and really the only option if you are trying to grow on pure clay. 2m x 1. The rate of this silting depends on several factor but principally the following. Cut pool noodles: A cut pool noodle can also be used as an alternative to hydroton. It is worth mentioning that certain soil types like heavy clay will be unlikely to allow sufficient water drainage for a soakaway, while sand, chalk and limestone based soils are likely to be suitable. Fill with water to depth of 300mm. The resulting calculation will give you. Country. grading. This is done to guarantee that the ground (soil) is suitable for a soak away, as well as that the soak away is correctly built for the situation at hand. The size of the soak away will need to be worked out in advance. We can also deal with your insurance company directly on your behalf at no extra cost to you. If you have noticed that water tends to puddle on the ground rather than soak in, it is likely your soil is clay. This video shows a soakaway drilled in clay in a garden in High Lane we had also dug Land drains in a flooded garden. 1. 60 Minute Storm Duration Clay Sub-Soil Area To Be Drained (m 2) Size of Soakaway Below Invert (m3) 10 0. Where digging is required, it is traditional in wet regions to dig clay into narrow ridges to. Clover fixes atmospheric nitrogen into soil fertilizer to give grasses more nutrients and help them resist diseases. The pre-fabricated soakaway system offers an alternative to gravel when installing a French drain garden drainage system. I've found that garden compost is best, but conditioners such as seaweed, farmyard manure, or bagged manure products like Scott's. 3. Backfill the hole so the crates are secured. Infiltration Test. Done properly, there will be no visible signs that any work was carried out. pour liquids such as oil on the surface. Leach Field Design for Clay Soil. As sodium salts are leached through the soil, some sodium remains bound to clay particles—displacing other cations. Digging in a 1m3 soakaway using a soakaway crate near the centre back of the garden (at least 5m away from the house and 2. #2. Digging with a sturdy spade is the best way, but using a rotavator works OK too. If you are hoping to create a soakaway to alleviate waterlogging in a garden, you may well be disappointed by what follows. All septic tanks require emptying ONCE A YEAR. Dig a large hole in the ground, line the sides with heavy-duty landscaping fabric, to keep the earth from over time clogging up the gravel. Don't spill your soil. soakaway. Three types of samples viz. Use berms – mounds of soil – to hold back the water or divert it elsewhere. Thread starter Temmy; Start date 20 Aug 2021; Temmy. Is your septic tank and soakaway in clay soil? Are you installaing a septic tank and soakaway into clay soil? Would you like free help and advice about installing septic tanks and soakaways in clay soil? Then watch this video. It takes approximately 5. 0m deep. septic tank soakaway clay soil - septic tank soakaway. Land drainage is principally used to alleviate waterlogging in fields and gardens, but it can also dessiccate certain ground types in prolonged dry spells, so think carefully before installing. Soakaway crates take run-off water and allow it to slowly percolate. how quickly the water will soak into the soil around the soakaway. Will a soakaway work in clay. Water-loving plants like swamp milkweed ( Asclepias incarnata; pictured) or cardinal flower ( Lobelia cardinalis) both beautify and improve poorly draining areas. Surface Water Drainage Options in Clay Soil Are soakaways suitable in clay soils? ©2023 by GeoSon. It was fitted with a condensate soakaway as no drainpipe/drain nearby. Essentially, the poorer the drainage, the bigger and deeper the hole needs to be. A traditional soakaway will have a ratio at the higher end of scale where it drains a road or several houses. Soakaways may often fail in the first 5 years of their life in such bad porosity soils. Required storage volume in the soakaway, SSoil organic carbon dynamics: Impact of land use changes and management practices: A review. 0m can become difficult and more expensive to build. #1 I'm looking at re laying my driveway, which is currently constructed of non porous materials and which runs into local drainage. An online system. The Soakaway Design Guide (July 2000) 2. In a word, peat is springy. Clear gutters and outside drains. Installing a soakaway involves careful planning and adherence to local regulations. 2. Pre-settled effluent from a collection and storage/treatment or (semi-) centralized treatment technology is discharged to the underground chamber from which it infiltrates into the surrounding soil. This means that if you build a soakaway or put crates into the ground it will just sit there or drain away very slowly. 174. Watch the capillary action of soil type and how long or fast it takes for a French Drain to work. This closes the pores and fissures at the excavation interface leading to. One is to run your rainwater into a water. We don't have a surface water sewer, only foul. It consists of a hole dug into the ground and filled with rubble or coarse stone with a drainage pipe or French drain running into it. However, the consolidation of the soils is time dependent, delaying construction projects making it a non-feasible alternative. Typically developments situated on soils with a high clay content tend not to be. If the sediments entering the soakaway are the same size or larger than the pores in the infiltration medium then the sediments do not significantly affect the infiltration rate through the soakaway. How to deal with surface water on clay or high water table site. Let Geoinvestigate’s experts quote for your next SuDS soakaway, soakage, percolation, permeability or soil infiltration test. Without proper garden drainage solutions, timber decking can be prone to rot, the likelihood of mold is increased, and the shape and finish of the structure can become distorted. bark as final layer. Installing French drains and a soakaway in clay soil can be an effective way to manage waterlogging, but there are certain considerations you should keep in mind. If the water table is too high, then a soakaway simply won’t work there. 5 litres to fill a volume of this size. Whereas if the soil is very sandy with a high infiltration rate, you can install a small soakaway. Procedure. It doesn’t get compacted, which can suffocate new seedlings or cause root veggies to become stunted because they can’t push through dense clay soil types. Rotavate that in and replace the top soil. You should recieve some clips or ties with the crates. The second option is to raise the soil level using free-draining topsoil. A lot of sites say that adding sand to clay soils means the clay aggregates around the sand and sets like concrete. In clay soil, the effectiveness of a soakaway can vary. It promotes the rapid growth of roots and plants in general. Paving reduces or stops rainfall getting into the ground. You can claim a ( small) reduction in your water bill. Sort By: Default Product Name Price Low-High Price High-Low Best Selling Latest Per Page: 24 48 96 ALLThe Good and the Bad of Clay Soil Of all the different soil types (sand, clay, silt), clay soil is made up of the smallest and densest particles. Firstly you need to contact your local building control officer and take advice about the soakaway and ensure. In this video I show you how to construct a soak away and connect a biofil biodegradable waste biodigester for it. The hole should be at least 4 feet. Clay soil, constantly wet from a soakaway will become a quagmire and make the feild close to unusable for much of the year. Friday 4th March 2022. If the garden is already waterloggedAbove-ground mound soakaway systems, or mound systems, were developed by WTE Ltd. Yes, adding gravel to clay soil can be beneficial in several ways. A minimum soil infiltration rate of 0. If you can't connect into the flood water system and the garden soil is mostly clay, another option to disperse water is to install a pump and sump system. In clay soil, the effectiveness of a. I'd have thought once you removed all the top soil and roots etc down to the sub soil and get 100+ mm of well compacted hardcore, it doesn't matter how soft the underneath is. In many cases, sites with a high water table or a heavy clay content will also not be suitable. Save time and money with one of the UKs leading soakaway and site investigation experts. How deep should a soakaway be? The Perforated pipe should be laid at a minimum depth of 200mm and a maximum depth of 700mm. DON’T install a soakaway if you live in a polluted area prone to smog. Materials that compost quickly include well-rotted manure, leaf mold, and green plants. Vegetation – Dense vegetation on a rural surface can intercept and store a significant amount of rainfall, thereby reducing the catchment runoff. The purpose is to slow and control the flow of water to prevent flooding. Ello, I've been trying to sort out the rainwater drainage at the back of our house. The organic matter needs to be mixed into the top 6 to 12 inches of soil. However, it’s a lot more subtle in terms of its appearance in the landscape. Cheaper but less effective methods include soakaway areas, soil aeration and changing the soil composition. What are the alternatives to a soakaway? The regulations allow for two alternative approaches. Installing a soakaway is fairly straightforward and requires little. Next, a long channel drain is placed in the trench. some clay soils) may not be suitable. 20 for sewage treatment units. Tin Soldier; 13 Feb 2017;. A soak pit, also known as a soakaway or leach pit, is a covered, porous-walled chamber that allows water to slowly soak into the ground. We are on clay soil but there is no combined or rainwater drainage in the road. Follow these 6 simple steps to install soakaway crates – both quickly and correctly: Step 1 – Create space. They are also referred to as dry wells, soak wells or soak pits in other countries, but in the UK are known as soakaways. Be sure the soil is a bit airy, too. Add water into bucket around sealed clay bag; no need to submerge top of bag. Clay soils can be difficult for roots to penetrate, and can be very hard for gardeners to cultivate. Clay and rocky soils aren’t their cup of tea (ha). Soakaway Crates in Clay. Clay and clay-based soils have poor porosity: it is impossible to disperse the septic system effluent satisfactorily in such non-porous grounds. septic tank soakaway clay soil - septic tank soakaway clay soilyour septic tank and soakaway in clay soil?Are you installaing. Depth in ground. Soakaway not installed correctly. Excess sodium (salt coming from detergents such as washing. 2m deep it's still surrounded by clay and after yesterday's heavy rainfall this is what it now looks like:soakaway to be considered. 4: Till in Amendments the Right Way. This option is super popular for crafty hydroponic gardeners on a budget. The condensate pipework may terminate above or below ground level. Answered By: Cameron Gray Date:. 5m away from the garden wall). Some soils, such as heavy clay soils, will not work with this kind of drainage. Put bag of clay in bucket. 216m3 Volume Sump pump information on my Sumps and Pumps. They put plastic based fences all the way round and laid turf. Alternately, gardeners can build berms in the landscape to lift plants out of poor-draining clay. 20 for sewage treatment systems. When designing a leach field for clay soils, it’s important to take several factors into consideration, including the soil’s texture, structure, and drainage capabilities. The clay soil used in this study was composed of mainly kaolinite as determined from the chemical analysis. A soakaway may well be pointless in heavy clay and therefore your only other option would be to run the water off the surface and round a corner to a bed or lawn etc, depending on the surface area being drained this may not be suitable but for a small drive it would probably be ok. Many recently developed neighborhoods, especially in Eastern Nebraska,have had their topsoil removed and. Normal soakaway drainfields will not be able to soak wastewater away into clay or clay-based soils because of their porous nature. Steps: To build a basic stand-alone soakaway, dig a pit in your soft turf no less than 1m2 and 1. W. A soakaway is essentially a point feature; it does not have a channel. 2 options. Water-loving plants like swamp milkweed ( Asclepias incarnata; pictured) or cardinal flower ( Lobelia cardinalis) both beautify and improve poorly draining areas. The first thing to consider when choosing a suitable site for a soakaway is the water table. Staffordshire. Pre fabricated soakaway and trench baskets. Study criteria. Dig the organic matter into the top 10 inches of the clay soil, working backwards trying not to compact the dug soil. A simple infiltration test will so on give you the damming news; the water simply won’t shift. Soakaway Issues. We've rounded up the top driveway drainage solutions for you to recreate in your landscaping scheme. org If you are just interested in getting the water away from your clay soil and elsewhere, you can have it drain away from your property. The location of the soakaway is determined based on soil conditions, distance from water sources, and the size of the property. Turkey grit is ground granite. 8m deep. A trial pit is excavated with an excavator to represent the soakaway and we use the time taken for the water level to fall from 75% to 25% is used to calculate the Soil Infiltration Rate (m/sec) enabling soakaway design to be undertaken. In doing so, it will add to its ease of cultivation. Digging a trench is one of the most effective ways to prevent waterlogging. 2. Sit the butt on that. 1. #1. I explored solutions like leechfield,soakaway,cement ring well but all fails in clay ground. 23 4. 87 40 2. There's a slightly smaller soakaway out the back which we have joined into for the rear, all rear rainfall also goes via a 1250l water butt. This, as well as some other planning around your soakaway construction, will make the job much easier for you – preventing a mistake that could be time-consuming to remedy. If so, consider installing a drainage system, as long as you have somewhere for the water to go (a ditch, drain or soakaway, for example) Often there’s no easy way to shed excess water. Soakaways and alternatives. Garden walls, paths and houses may develop severe cracks; There are many additional benefits of not paving over front gardens or keeping the paving to a minimum:The soakaway should then be filled with 10mm limestone chippings; Soakaway Installation. J. started a discharge from a septic tank or small sewage treatment plant. then soil. However, an increasingly popular soakaway solution is soakaway crates. How a French Drain Works - in Clay Soil. Even if a connection to a down pipe is. Where the new driveway is small, if the existing garden is not water logged it should be acceptable to allow the water to soak into the ground. and copyrighted in 1996, to compensate for clay and impervious soils and high water table ground that cannot utilise a. Usually comes as a kit and The hole can be anywhere from 600mm to 1 metre deep and about 200mm in diameter. What are your options if you have a septic tank in clay soil? Unless you have another area within your property's boundary which does not have clay soil, then a soakaway system or drainage field is unlikely to work. (3–6 oz per square yard). Quote 2 involves lifting sections of a driveway and path, installing the soakaway to a deeper level to bypass the clay soil and finishing off by re-laying the sections of the driveway. I think with the soakaway as specified you will end up having to land drain the field anyway and there will always be a soft spot over and around the soakaway hole. 28 Mar 2008. Soil that consists of over 50 percent clay particles is referred to as “heavy clay. So the two are totally different and adding sand to clay doesn’t mean it will set like. The down pipe (cast iron) appears to be blocked and the water is filling back up the down pipe and gushing out at the lowest joint which is about 4ft from the floor and subsequently soaking the walls of. Log In. How do I install a soakaway in my garden? Follow these 6 simple steps to install soakaway crates – both quickly and correctly: Step 1 – Create space. During my internet forays I've come across the option of using rainwater crates instead of simply digging a hole, lining it and filling it with stones to form a soakaway. To construct a basic stand alone soak away or one to use as a dispersal point for a French drain system where the water will gradually seep away into the surrounding soil. 3m deep and 1m x 1m. LeadFarmer said: Soakaways in clay soil just become ponds. Dig. If compacting is inevitable, the next best thing is to amend the soil with compost, gypsum, wood chunks, and mulch. Once the soakaway crates are in place, back and side fill is required to ensure the structure remains stable and in position. If the soakaway has been constructed in non-permeable soils such as sandy clay, silt clay and clay then the effluent from the septic tank cannot filter away through the soakaway then flooding of the septic tank will occur causing it to overflow, causing a health hazard. mix concrete on the driveway. When designing a leach field for clay soils, it’s important to take several factors into consideration, including the soil’s texture, structure, and drainage capabilities. soils that are prone to swelling and shrinking) can cause structural damage to underground septic systems, which may require costly repairs. See full list on gardendoctor. allow the garden. The effects of applying fly ash for soil stabilization are the reduction in the plasticity and soil swell potential and increasing the soil strength and CBR values. The soils treated are Organic silt, Varved silts and clays, soft clay, Dredged material The design considerations which should be made are bearing capacity, Slope stability, Degree of consolidation. #5. Vermiculite aerates soil well if used together. As you can see from the pictures, it looks like clay and certainly acts like clay. ) A soakaway won’t work because the soil is clay-based or the water table is so high that water won’t drain away. After (just recently) reading to manufactures instructions concerning the soakaway its states it need needs to be. Soils are often considered sodic when the amount of sodium impacts soil structure. e. The first thing to consider when choosing a suitable site for a soakaway is the water table. Fill around the sides and top of crate soakaways with a good, compact layer of sand or gravel, before backfilling with soil. Heavy soil, rich in clay, tends to drain poorly, so your waterlogging problem may affect the whole garden. Clay and rocky soils aren’t their cup of tea (ha). Plus, a cut pool noodle can help to improve drainage in hydroponic systems. Chapter 3 1994 8. 5m away from any boundary. White clover spreads horizontally and grows 4-8 inches tall. Allow winter frosts to work on clay and break it down. ) Organic materials like compost are recommended for amending clay soils. Soakaway: A soakaway is an underground structure designed to disperse water into the surrounding soil. We have taken down a large wall and the earth behind it thus trying to have it at one level. Excavate a hole 300mm square and 300mm below the proposed outlet from the septic tank or sewage treatment plant. #1. put soil, sand or similar material on the driveway that will block the surface and stop water soaking in. Be sure not to overdo it with peat moss as it is important to add sand or perlite when using peat moss for it. The excavation can proceed in a similar manner to any deep drainage excavation. Plan patios, paths and decks. Due to its nature, vermiculite prevents mould. Gently remove the lavender plant from the pot and backfill the hole with the garden soil mixture. When it comes to the hardcore infill, it should totally surround the pipe and rise to around 100mm above it. 4). It should be noted that soakaways rarely work on heavy clay soils. Use coconut fiber (fibers extracted from the outer part of coconut) to custom make an orchid mix. Bore a hole 150mm in diameter with an auger, to a depth of one metre. Simple to install, with minimum maintenance required. in you case you could run a pipe across the front of the building and join at 1 corner with a Y. French drains help to. The ideal garden drainage solution depends on. dustmaker said: building regulations state that a new soak a way has to be at least 5. Pre-settled effluent from a collection and storage/treatment or (semi-) centralized treatment technology is discharged to the underground chamber from which it infiltrates into the surrounding soil. 262 months. The most commonly used in the industry is: Soakaway Volume = Area x (Rainfall Rate/3000) For a standard 60m2 roof or driveway in the UK the calculation would be: 60m2 x (50mm/3000) = 1m3 volume This means you would require 5 of our CORE Water Crates to create a 1m3 soakaway. So yes soakaways can work perfectly well in clay. Soil sodicity. The Infiltration Rate of Soils also tends to decrease over time. ianmcd said: yes it should be a min of 500mm away and yes you can buy the soak away container but there is no regulation that I am aware of that says you have to use such a container, the lime chips just neautralise the acid in the condensate discharge. Septic tanks must always be subjected to a percolation test before they may be. Soakaway not suitable for clay ground and will make matters worse. So yes soakaways can work perfectly well in clay. And it could be right if we consider that concrete has sand in it. Soil that is mixed with peat is much less dense. Chamomile can be stepped on reasonably once established — at least after 12 weeks — but will show signs of wear if trodden. In our first spring season, we noticed the garden was very waterlogged and pestered the builder who eventually installed a soakaway in the garden approx 1 metre from the back of the house. 4. e. This is most common if the membrane is broken, the crates are the wrong size or capacity, or the pipes have. Till or loosen your clay soil to a depth of six to 12 inches, then spread a four-inch layer of perlite across the top. orOThe most common size of soakaway for residential use is 1 Cubic Metre (1m³), as this is what most Local Authorities seem to specify. 8 meters deep to work. you are now not allowed to run storm water in to fowel drains. Add a gradient. 3. BS6297:1983 requires that septic tank soakaway trenches should only be constructed where there is at least 1 metre of soil between the soakaway and the water table at all times. All soakaway systems need to be at least 5 metres away from your property; if the areas surrounding your property don't span more than 5 metres you can't install one, and you must consider alternatives. Soils with a clay/silt content greater than 40% are. Soakaway won't work - what alternatives do I have? Temmy; 15 Sep 2021; Roofing and Guttering;. Are soakaways suitable in clay soils? Over the years we have seen multiple examples where soakaway systems have been proposed within development schemes situated on clay without consulting a Flood Risk Consultant, and the Local Authority have rightfully raised a holding objection, pending further investigation. it may mean deeper than standard foundations particularly if you have clay soil. Fill the hole with water and come back and check it the next morning. Furthermore, expanding clay soils with a COLE value greater than 0. Save time and money with the soakaway experts. This creates aeration in the soil, allowing fluids to travel throughout and not settle all in one place. Sometimes, your septic tank overflowing can cause the wrong stuff to go into your soakaway system, which in turn causes a blockage. At 1. How deep should a soakaway be in clay soil? 1. Underlying soils – This has a limited impact on man-made surfaces such as pavements, but has a very large effect on natural or agricultural surfaces. And there you have it, a fully installed soak away to take care of your garden drainage issues. Log In. Seal bag of clay with twist tie or rubber band. Log In. The guttering had been disconnected. 7 Sep 2013. Whether you’re using crates or stones for your soakaway pit, be careful not to spill soil inside your geotextile lining as it won’t work effectively. 35 80 4. Soakaways can typically be constructed at any depth between 1. Your soak-away trench will need to slope away from the garden and be at least 2 feet wide and 2 feet deep. orAlternatives to Soakaway - Clay issue. The size of the soakaway should be a minimum of 1m x 1m x 1m below the bottom of the incoming pipe. I started to dig a soakaway pit, only to find four different colours of clay. Accessories include cover, additional panels, bottom, surface drain and filter fabric. Soil sodicity. Although soakaways are an effective sewage treatment component, they can experience problems. Rainwater harvesting systems will usually have an overflow to a soakaway or drain. Has anyone. Conclusion. Allow the top of the soil in the pot to protrude 1 inch above the soil line. Has anyone used the. 9 Oct 2019. 4) Dig up the entire garden and mix the soil. This excess water will eventually soak into the ground well. How to Build a Soakaway in Clay Soil? A soakaway is basically a deep hole filled with rubble. Area (A) = V X P X 0. In a clay soil it’s going to take a long time for any soakaway or finger drains to empty so you need to size them accordingly. DON'T install a soakaway in heavy clay soil, the water cannot drain through. To avoid water collecting in the soak away leaking into and damaging the foundations, The soakaway should be situated at least 5m away from any building. Excavate the area, making a hole that is the right size for the crates and the top, side and base fillers of gravel and sand. To work, it must extend below the clay and be at least 1. A rainwater soakaway is a drainage trench that is dug from surrounding soil in order to manage surface water through a septic tank or and alternative drainage route. (Using a tiller too often will actually impair soil drainage by breaking up soil aggregates. Soakaway crates can be used to create a large storage volume or deep bore soakaways can be installed to. 75 high. While we recommend your groundworker conducts a soil percolation test and creates a set of calculations, there is an alternative method that will give you a rough idea of the soakaway size you’ll need: If your soil type is not too heavy/clay, you can assume that one crate (1000mm L x 500mm W x 400mm H) will be sufficient for ten sq metres of. dustmaker said: building regulations state that a new soak a way has to be at least 5. changed your discharge from surface water to ground. this has lead to storm and in some cases sewer drains being overwhelmed. To perform a perc test, pick a spot along the path of your planned drainage system where you hope to locate a drywell anyway .