today we're going to spend a few minutes looking at how we might head off a major ecological disaster from flooding flash flooding from solid surfaces like this path there must be millions of made of non-porous material concrete slabs etc etc so the board of the introduced legislation to prevent people from concrete in their entire front garden though you can still have a car part in the front garden if you like but using porous permeable materials and jeremy swallow from marshall has one system that can solve the problem how did you do it it's all called sustainable urban drainage systems yes and our system is called priorities a brand name yes really what this does it's managing rainfall or water where it lands at source and then goes between the gaps in the paving it's a specially designed a lot less however we look at just to save the block and then we'll go on to the site this is it okay as you can see it's it's 60 minutes it's so it's a good depth it's got strength and rigidity but around the edge there's a painted nib design yeah so this creates voids between each block and so the water can go through into the subject and it's quite that also would help to lock it together yeah that does leave still so if you turn the car you're not going to be lifting us or you'll be spewing out slightly but the water most importantly goes down the sides and into some place it seems to me that the sub-base is actually the crucial bit oh i'm the block as well you've got to get the water down there no but can you do this anywhere you can't do everywhere plays a I'm not good and heavy soils are not good and then we'd look in but I think we ought to instead of time we should go and look at the job yeah it's easy well there's no better place to demonstrate this than our drive we're garbage a me but run me through the process okay what we've done already it's obviously we've excavated the site yeah we've put the hauntings on because we don't want the Box moving like the typical kind of driveway and Serratia sure then we're putting the first layer of the specially calibrated aggregates down into the hole yeah what sort of depth that we're talking about overall overall we're looking at 310 millimeters and that constitutes around 250 260 of the 20 mil a gregoria and then we put a 50 mil about six millimeter on there as well that's sort of in all money that's just or what a Foote just knit just over a foot and what's unique about that is that over the last 25 years that kind of sub s will hold that volume of water and let it percolate away into the soil and it's an essential part because it's the DI F M it to do it for me so not a DIY so what's the story of this hall yeah okay what we've done and what everybody should do before putting a sustainable urban drainage system is do a soil permeability test yeah so what we've got here is a 400 by 400 by 400 hole what we'd recommend is to take two or three holes depending the size of the area of your drive here we've got 30 square meters so we did three yeah because the strata of the soil as you go down changes and what does this tell you so we fill it with water and then we measure it over 18 hours now the top quarter we don't really count in the test what's the important is that from 3/4 to 1/4 down over 18 hours we're looking for the water to disappear into the ground and that would be the tipping point if it can't do that then now if that doesn't work obviously we look at you'd have to look at of the system and of course if it doesn't work you have just three O's the film well that's not bad if you're gonna do the work anyway so what's the job we're doing no but what we're doing to finish it off we're putting the six mill washed aggregate again there's a top layer and we're gonna brush that into the block and that will disappear through the block as well and that stabilizes as well how much they're gonna cook right the big questions you know what we're looking at here probably for a priori installation you're looking at maybe a hundred and temp to 120 pounds per square meter there's a ballpark figure that's a ballpark figure but what is eliminated is if you went for traditional drive you'd be looking at drainage in there as well and so that would be an additional cost so in the end it's probably about very similar to having your driver installed traditional method with MRT type 1 if you're thinking about a new driveway or if you're already planning to do something think of the environment think of a system like this which solves a big problem yes enough you well as they say the proof of the pudding is in the eating of it and these guys said that this Sufis would actually consume water from our dumper truck hence the sandbags we're about to drop three tonnes of water onto this just in case it doesn't work we don't want the girl inside but it's super well yes affray why do you go by okay oh wow thick well I'm absolutely speechless that is amazing it really is good boy has em miss Gordon well if you'd like any more information about this sub system or anything else in the program then it's all in the weekly fact sheet and the easiest way to access that is online