 Well, hello everybody and welcome to another one of Hydrotera's webinar series. Today we've got a presentation by Neil Thompson from Sinversa about managing landfill airspace optimisation. For those of you who don't know what that is, that's about getting more out of your landfill. So working out ways to compress the waste and that sort of thing. So we get more out of the existing landfill infrastructure that we have. So a little bit, there's a picture of our speaker and you, Neil's geo environmental engineer working with Sinversa. And I had the pleasure of working with Neil many years ago at Golder Associates. We were both working on landfill works and that sort of things. A little bit more about our speaker. So Neil was educated at a university in Scotland or in Edinburgh known as the Harriet Watt University, which was named after Watt who invented the steam engine apparently. So Neil Thompson is a principal geo environmental engineer and is currently Sinversa's workgroup leader for the ground engineering and geotechnics teams with over 40 years ground engineering experience from the United Kingdom, Southeast Asia and Australia. Neil has broad and significant experience in delivering ground engineering components of waste management, infrastructure, land development and energy projects. Neil was formerly the engineering manager in Victoria for Cleanaway and responsible for the delivery and obtaining regulatory approvals of landfill cells, which involve significant groundwater controls, earthworks and geosynthetic lining systems. During this time, Neil performed the monthly airspace consumption assessment and fully understands what is required in constructing landfill infrastructure. In addition, Neil has directed and managed the completion of a large number of projects, including construction of landfill facilities, geotechnical and environmental site assessments, soil and groundwater for a diverse range of clients. So I think you'll all agree and it's great to see so many people here that Neil has a lot of knowledge to pass on to us about landfill and how to optimize their airspace. Before we get started, just a couple of administrative matters. We love your questions and certainly it's a big part of what we do in these webinars. So if you can use the Q&A button that's there and type your questions in, I will read out those questions at the end of the webinar. Thank you also for all those early bird questions. We've got about 10 of those I think that have come in by today. So we'll deal with those questions first and then move on to the ones that are raised during the webinar. Why does Hydrotera do these webinars? We like to share knowledge and I think a lot of people in the industry like to share knowledge and many things to Neil for sharing his knowledge today. We also think it's important to facilitate education. I think we're filling a bit of a hole in the current educational platforms that we have. And we like to talk to industry leaders and understand where the market or where technology is going in the market. So what are we going to talk about today? Well, I'm going to talk briefly about why landfills are important. Some people think landfills are a dirty word. I'm going to talk about the extent of our landfill network and the amount of waste that goes into them now. Then Neil is going to talk about waste placement optimization and why we need to do it. Then he's going to talk about waste placement optimization, how we do it. And then we'll move to part three, which is the Q&A. So let's get into it before we get into it. If you want to know more about landfill management, we've had quite a lot of different webinars over the last sort of three years or so, which really do form a pretty comprehensive educational suite. And we've got one on landfill capping, which was by Dr. Brent Davie, another one on landfill leachate collection by Tyson from McKenzie Environmental. We had one by Nick Simmons, which was all about landfill monitoring best practice. We had one by our own Yic, all about automated monitoring and control of leachate pumping. And then we had another one on ground gas monitoring. And of course we've got today's. So all of those are available as recordings, as is this one going to be, and you'll find them on our website. Okay, so landfill, an important part of waste management infrastructure. Sometimes I think we've forgotten why we have landfills. There's a lot of them. And in Victoria alone, we've got 92 operating landfills at present. And around the country, we've got over a thousand. And a huge amount of our waste still goes into landfills. I can sort of remember back 15 years ago, we had something called a zero waste strategy. Something along the lines and we were going to be turning off waste going to landfill. Well, it's proved quite a challenge to do that. And consequently, they're still a very important part of our infrastructure. Certainly management of these landfills has improved immensely over that last sort of 20 years or so. And Neil will have seen those changes. But I'm interested to get Neil's thoughts later on on this on the whether or not we're quite ready to switch landfills off. Because certainly no sign of the amount of waste going into them reducing. So I think landfills are important. I think they're very useful. And we probably should be viewing them more in that way rather than something dirty. That further ado, I'd like to pass over to Neil. And thanks very much for Neil for joining us today. Thank you, Richard, and afternoon, everyone. Thank you for taking the time to join this webinar. Well, really I was going to look at what we prepare here at Sunversa as fill plans and 3D models and why we do that and then how we do that. But landfill operators when they construct a cell, they spend several million dollars in creating the cell and getting it licensed through the EPA so that it can accept waste. So it's a considerable investment. And so really it's an asset and that's it is the airspace that they have. So not only is the floor in the base of liner system constructed, but there's the agreed top of waste contours. So how high they're going to fill this landfill cell with waste. And really need to optimize that space and get most get as much tonnage of waste in there that you possibly can before you need to move on to the next landfill cell. But there are consequences if we don't keep within the boundaries that are agreed with EPA and councils and that can be overfilled. You actually go outside the boundary, be it the vertical boundary or the horizontal boundaries of that cell. And that can happen through poor site controls, poor planning, maybe the next cell is not ready or licensed to receive waste and there's nowhere else for the waste to go but higher if you can get approval from the EPA to do that. And now it comes from these inefficiencies. Well, if they've got overfill, you've got to then spend money taking that overfilled waste and placing it into a licensed area. So you're double handling, you're spending a lot of money on fuel, diesel for the excavators, the trucks and the compaction equipment. There's the time as well to haul and replace the waste and then you're out of your regulatory compliance so you tend to have the heat from the EPA on your back as well. So all these things led to discuss with one of our primary clients how we could provide 3D models that would allow the operators to keep within the boundaries of the licensed facility. So how can we protect this valuable asset? The operational airspace has to be fully utilised and I'll go through the difference between total airspace and operational airspace in a minute. We've got to keep waste within the approved cell boundaries and again as I say, horizontal and vertical boundaries. We have to maximise the compaction during waste placement. So again, we have waste coming across the way bridge so we can record the mass. And we've got to try and get that mass into a smaller volume as we possibly can so that we can get even more mass into the remaining airspace. So the purpose to get the trucks to the actual tipping point, we really need to include haul roads and there's a whole science and engineering background into the placement of haul roads which minimises the airspace that you lose from the total airspace that leaves you with the operational airspace. So haul roads and the placement of haul roads to allow safe access in egress and tipping is critical for these cells. And to do that we also adopt what's called a haul road management plan and again that's an approved document that's listed on the website and guidelines as to how to prepare a haul road management plan. The haul road management plan just an approved person can prepare it that's outside of the operator, but it doesn't have to be an auditor that signs off on that. It didn't use to be, although it might be changing. So what are fill plans fill plans are a mixture of three dimensional and two dimensional models. What we have on the top right hand side there is a two dimensional pictorial representation of a fill plan which shows areas where the fill should be placed sequentially. So in the stages, which allows the breadth of waste placement within the cell, and then the cells have subsequent lifts to get to the top of waste contours. If you look at the longitudinal section at the bottom of the page that's taken from AutoCAD. You can see a rather horizontal surface at the top we'll come back to that in a minute. But you can see the maybe hopefully you can see a blue line at the bottom which shows the top of the leachate collection system which is the top surface of the as constructed landfill cell which is ready then to accept waste. And then to be quite badly colorblind so to me that's a yellowy green but to somewhere else it might be a completely different color but the three horizontal lines there show two waste lifts as it comes from the floor up vertically. These are the lifts. So each lift has a fill plan and you can see at the top there we make reference to lift six, which is from a different site. The lift between the two surfaces provides the totally a space within the cell for that lift. And then you optimize where you put the whole road you can see the whole road going through the center of the site in the top right. And that was located purely because of the large size of the site and other aspects of the facility which is to the south and to the west as shown there. This is brought in from the, we don't have this all word right at the northern boundary for instance because you've got the slopes the barter slopes the perimeter barter slopes of the waste which tends to be typically one in five and occasionally one in three vertical to horizontal. Once you know to have a waste contours on the base you can work out the maximum height of the landfill and therefore you split that into the number of lifts to achieve the waste placement. However, at the upper surface there's a minimum area that's considered safe for the use of all the plant supervisory people. And the way the customer trucks bring in waste and have to have a minimum area which allows safe placement and safe access and egress from the tipping points. Where do you get that guidance on the minimum area? So that varies from site to site and from client to client but really it's to do with the throughput the number of trucks that are coming in per day and how frequently you don't want the trucks parking up because they've got a job to do as well. So the turnaround time from the way bridge in to the way bridge out is highly critical so the safe working area is dependent upon the number of trucks that come in every day. A smaller landfill, rural landfill, might only have 10 to 100 trucks a day, a busy municipal landfill in the metropolitan area can have 800 trucks plus a day. And at the time some landfills are open 24-7 and therefore the lighting etc that's required to allow safe operations as well is highly critical in these fill plans or where they can be placed. And I think if you look right in the centre there to the left of where it says cell 4C lift 6, what is to me a red line, it looks like a V heading to the northeast, that's the temporary litter fences which move around to try and minimise litter travelling off site. It's okay when you're in the bottom of the landfill because you've got the perimeter around you but as the landfill waste comes up vertically and all the lifters are getting complete you're on far greater risk of wind taking litter over a greater distance. So without place based on the weather forecast for the day, is it how they do that? Yes, and also the size of the tipping pad and the open area etc but it's also a function of how many trucks are expecting in across the way bridge that day. Okay. Because we don't stop putting our bins out every day if it's raining. Good point Neil. Shall we move on? Yes please. So what are the inputs to fill plans? Well we need the top of lift, a surface level to the metres of HD, the lift height and therefore the airspace volume that can be consumed in that lift and that's assuming a waste density of x tonnes per cubic metre. The reason that we need tonnes is because the mass is measured for the way bridge and then we look at how much space that gets taken up in a month or two months, whatever the frequency of reporting is and then you know the number of tonnes coming across the way bridge and the volume that's being consumed that gives you a tonnage. That tends to vary between 0.85 and up to 1.2 tonnes per cubic metre so I was very surprised when I first heard that measurement because it's very light water so waste is floating on water, the leap shape if you will. The client then provides an estimate of the daily tonnages across the way bridge. That's very commercial and sensitive information. Some people like to do the calcs themselves and some clients like some versa or the consultant to do the calcs. Based on the open area and the amount of waste coming in we can estimate how much daily cover soils are required. That's required at the end of the day or the end of the shift so that you minimise wind blown waste. You stop odours migrating away from the site and reduces the risk of pests or vermin or getting to the waste overnight. I've talked briefly about the haul road locations which are pretty key and also the tipping pad locations so there's the open space area which is regulated by the licence that you get from EPA to say the minimum open area for waste but the tipping area is larger than that. So we can accommodate the trucks and the plant etc are needed to deposit the waste and also to compact it. The grade of the haul roads that's a critical aspect and when we're designing these because we want the trucks to have safe and fluent access in egress so that tends to be designed based on the type of trucks that would be delivering the waste to inform the site. So we put a small grade on the surface of each lift to allow any stormwater to shed within the area and not to shed to the side because the stormwater that balls on the open waste would be classified as leach it. The filling sequence per lift as you can see there the stages, the litter fencing, but based on that you can actually estimate how many days it will take to complete that lift and before the next lift is ready. As you come up vertically you need new haul roads to get waste to the next lift so all of this needs to be planned in advance. So using that planning now like you've got the data coming in from the way breach, what's the sort of timeliness on the forecasting of running out or is it just eyeballed? You do lift by lift and the waste operators are highly adept at this because they're always putting pressure on the engineering team to get the next cell ready and licensed. So there's a balance there but we've seen progress through the use of these fill plans on sites. Yeah. Right, next slide. Just a quick chat on the haul road management plans. This outlines the construction of the management of the haul roads that I've alluded to earlier. The alignments per waste lift, the materials that are required to form the haul roads because remember this is within a licensed area and to place other materials that's not coming across the way bridge into this asset. That's taken up base base so we want to recover as much of the haul roads as we can, otherwise it can be subject to the EPA levy because it's a material that's been left in the consuming volume within the cell. So if you look at ways of how we can reuse material that's not often successful because occasionally the material punches into the waste and therefore you can't reuse it if it's actually contaminated so to speak with waste. So what I've been doing with clients is tying the haul road management plans to each financial year and then they can, that helps them with the reporting. There's a document through the EPA there, 332.8, which is a guideline on how to calculate the waste, the waste levy and allowable rebates etc. And then there's an appendix, which is a good guideline for the management of haul roads and the haul road materials. So the material you use for your haul roads has to make your license condition for waste that can be accepted to the site, is that right? Yes, but generally speaking it can be bricks, broken bricks, concrete, you know, regraded concrete or non-descript crush rock etc. There tends to be two or three layers to form the road to make it an all weather road, bearing in mind that this is unsealed and it does require maintenance from time to time, primarily around the weather seasons. But the last thing you can have is big pot holes in the haul roads because they can lead to punctures in the customer trucks or delays in the customer trucks deposit and waste and go in and collect and mow them. And used to be in the old days you could use the leachate on these haul roads for dust suppression, is that still the case? I think they don't particularly like the re-spraying leachate, we don't know what's in the leachate now with PFAS etc. So some operators may, if they know what the quality of the leachate can reuse it as dust suppression. But if you have the potential for PFAS and leachate and the wind taking air droplets away, then that can be a hundreds shall we say. So I think it's on a case-by-case, site-by-site basis. Do you think there's a landfill out there which doesn't have PFAS in its leachate? That's a subject for another webinar Richard, I'd say. Alright, next slide now. So back in office and the safety and the weather-free offices, we put together 3D models which are for the two-dimensional representation earlier. The 3D model is usually prepared through the AutoCAD and we use a sub-programme called Civil 3D of how others using 12D, but we've been using Civil 3D for quite a few years now. So we've got quite a good team of 2D and 3D modellers run by Zahe here at Syngerser. But if we know the volumes, etc., we can, or the lift sizes, etc., then we can prepare these models that suit the site conditions. A lot of the clients now have their own drones and can fly a drone to get an up-to-the-minute topographical surface, which shows the top of the waste. We know the lift height they're going to achieve, and therefore we know the volume that is still there to be filled with waste. So the model's based on the total airspace. So as I said before, the pre-settlement top of waste contours that has built cell records, so the top of leachate collection system tends to be the upper surface of the basal liner. Client provided either topographical or drone surveys. Drone surveys are becoming more the norm now because of the trucks and the size of the plant and the equipment and actually the limited visibility for the drivers and operators of the plant. Drones are far safer than having the old fashioned topographical survey at 10 metre centres. So we've taken into account the proposed future capping. It might be a conventional capping designed through the EPA Victoria's Beppum, the best practice environmental management, or it could be a phytocup, which might be marginally thinner. All intents and purposes, it tends to be a conventional geosynthetic line and soil cap that goes on the cells that we've been working with more recently. And being AutoCAD we save these files as DWG or DXF formats, which suits some of the programmes that we'll come to next. So how frequently do you do this? Well, it depends how quickly the lift will get consumed. If a lift is going to last three months, then maybe a month out or so, we'll start looking at the aerial survey. If the lift was to get consumed more quickly, then more frequent aerial surveys are required. And you can think of them as you get, as the cell becomes fully consumed, the plane area, the planar area, the two dimensional area at the top, gets smaller and therefore the consumption speeds up per lift. So do you find there's much variance from what's coming in the way bridge versus the actual filling rate? Like you get a lot of variance in the density? I think the, yeah, if you've got, there's been a surge in trucks coming in really quickly, then that does have an impact to, or can't have an impact to the density, because the compactor can't do as many passes. Backwards and forwards on the waste before the next lot of waste is being deposited. Makes sense. All right, next slide. So we, one of our clients adopts the Trimble system. Trimble is well known for their survey equipment, etc., and surveying. So the waste placement and the compaction plant has GPS system installed. We can, we can convert our civil 3D models, the DXF and the DWG models to these SVD, SVL and TTM files, which are then uploaded through a Trimble business center, dedicated, it's a portal dedicated for the client and for the site specific. And then the client contracts waste compaction through VisionLink or through another program called Propella. The graphic at the bottom left there is from Trimble's website, which shows that from the computer, the signals get bounced off a satellite, as you can see in the top right hand image, again from Trimble website. And then that can be beamed down into the sievers on the on the construction plant, be it a dozer or a compactor. And then they have the model, they know how to the boundaries with which they've got to keep the waste in to allow them to still meet their license conditions and to minimize the chance of overfill. You're actually monitoring on the dozer. The dozer is actually can measure the lift plan, each lift plan can get the input into the dozer so that the operator knows the vertical height and the horizontal boundaries in which she can place or compact the waste for that day. And how many sites are actually using this sort of technology now? So we've been working on three sites with this, and I'm sure there are more. It's far more efficient. It's the risk of overfill. Overfill costs a lot of money. It doesn't sound much if you've got to move 100 cubic meters of waste. Just the fuel consumption, labour rates, and the compactor, the compactor and the dozers, they've got set hourly frequencies that they need maintenance etc. So you're just burning through that time between maintenance periods more quickly. Okay. Interesting. Next slide. Yeah, this, these are the two I've just got from the serving guys today. And the top left is the 3D model from Civil 3D, which you can see the boundary batter slopes. You can see the waste as it projects from the front of the drawing to the back. And a keen eye, you can see the the whole road as it goes from the bottom left in that drawing almost eastwards up a step gradient that suits the trucks. You see it more clearly or even clearer on the image to the right and that's from the proprietary software propeller where we take a near map image of the site. And then we superimpose the model, the model on top of the near map image to give a projection of what this lift will look like in the future once it's that lift is being fully consumed by the by waste. Oh, this is a, this is a quick reminder of what waste looks like on a landfill. We've got a dozer there with two GPS trimble components on it, which is taking the signal from the satellite and beaming it into the cab that you can see the bottom right there where the operator is trained as to how and where to place waste separately needs to compact the waste and if he's staying within the boundary constraints set by the model. I don't have many of your, many of the audiences have been inside any plant like like that but if you if you get the chance, grab it with both hands because it's amazing it's a skill people are using these machines are very skillful. Their visibility lines are very marginal. What you can actually see from the cab seat. It's really scary so you put a far greater importance on your safety when you when you know what these people can see and more importantly what they can't see when you're actually on a landfill site as a little digression there. It's very good one. And then 3D models allows incremental airspace assessments we compare as place waste with respect to the design fill plan for that lift. We eliminate to within reason at waste placement drift so that's overfill or underfill underfill can be a problem for clients as well because if if you haven't got the batter slope right and then you don't realize that until two further lifts have been completed it's really hard to go to a parameter of a landfill and then put waste back in and so you don't want to lose that asset either so overfill or underfill is particularly a thing that the operators are keen to minimize. And by getting more information obviously we can make adjustments to the design fill plan based on waste intake or seasonal differences, etc. So the outcomes from a client's perspective this is my opinion but the risk of overfill is significantly reduced. We have reduced labour plan and fuel costs and impact on time. A far better understanding of airspace consumption rates and leading to increased compaction rates which then you can build into the longevity of subsequent cells. We have a better understanding of the volume of cover soils that are required then that's a, that is a minefield to be honest you think you're just putting 300 mill or 100, no 300 millimetres of cover soils on every day unless you use an alternative system. But it's a colossal volume of material goes in there and it consumes airspace so getting that right is critical and it's something that we're all working on. As I say we had the planning for future cells, the budget and the timing of when the next cell needs to be open and licensed to receive waste. And the operators can have a more accurate prediction of whole of life model when will that whole landfill facility be fully consumed by waste. And this is the undertake these on a year and year annual, year and year annual, there's a superfluous word in there, planning events. And we try to bear estimation of what materials will be left in there from hall roads and minimizing any EPA levy. Apology to any regulators that might be listening today. We hope that that leads to a happy and less stress client engaged staff and operations team. And potentially lose the risk of an inquisitive regulator who may on an audit notice that if we have overfill a certain area for instance so minimize these things and we want to work in harmony with not only themselves where they can maximize profit but also the local communities where these landfills are cited. So just on that API levy side of things. So, what does that discussion look like with with the regulator about that. I'll be honest here and I haven't been involved in that myself but I know that the operators are when they have to do their, their statements annual statements and that's why we try and link the whole ground management plans to the financial years are therefore it's it makes it easier for their volumes etc that may still be in the landfill and consuming airspace that they may or might have to pay levy on the goal is to is to reuse the the whole wood materials as much as it's practical. But there's usually a little bit of loss into the landfill or can be so they pay a living because it's using up a space. I believe so. But I'm open to discussing that with anyone who what a knowledge that I have. Okay, so that was fantastic. And thanks for putting together a few takeaways I've added a couple of my own into this. I'm really good to hear these practical approaches to improving how we operate in this area. So the key takeaways by managing waste placement, we can optimize the amount of waste that can be placed in our existing landfill infrastructure. And with the restrictions that we have at the moment on getting new landfill landfills up. They can be more and more valuable. By embracing digital technology, significant efficiencies and cost savings can be made to landfill operations. I think we saw that particularly with that tremble network. Can reduce overfill and therefore reduce rework. We can optimize the location of all roads and better utilize the operational air space. We can better predict when the next cell is required to be licensed and ready to accept waste. We can predict the volumes of materials required for operations, particularly cover soils, all road construction and tipping bed pad materials. We can predict when material will be required. And we can produce better cost modeling for client for whole of life models. So without further ado, all there was a couple of other things that Neil, would you like to talk to this given your. This is a free plug Richard and I are on the organizing committee for this Australian landfill and transfer stations conference in Melbourne. Towards the end of June, which we're looking forward to. And on day one of the conference, there'll be two workshops, one on landfill gas but the seconds on optimizing airspace. It's been run by John Jones who's the Cleanaways, New South Wales landfill manager, and that promises to be really interesting. And so I'd advise people who are interested to, to get along or at least seek out the conference on Walmer's website and see if you can come along because it should be a really good three days. And it's being held in Melbourne. So if you have any free plugs, if you want to sign up for the next webinar, there'll be a link on this presentation or in the chat of this Zoom presentation. All right, we've got a fair few Q&A questions building up. So if you're ready Neil, we're going to charge into them. Yes, no problem. Good to hear you ready. Question, can you break down between regular waste streams and emergency waste streams, e.g. fire floods impact on landfill? Yes and no, regular waste streams as is your day to day that's coming in through the the way bridge and the operators work really hard to get to sell that one still space to clients etc. But the emergency waste, we can never predict these fire floods. Again, there's a balance about helping the community, the prime importance is to help the community through periods of difficulty with whether the landfill is licensed to take such materials, if you think of fire, houses etc. Some may have asbestos in the fiber sheeting which you can't take to all landfills. And then in floods, then the waste tends to be very saturated, which makes it very difficult to compact and also increases the potential for leachate within the landfill. But everyone has to come together and these emergency waste we've seen decker, formerly dealt, leading in that in certain areas. So it's really, really difficult. You've got to help the community when you can. Importantly, more recently what we've seen is the health industry when the amount of waste from the health industry through COVID, particularly the two years of lockdown, the disposable PPE, etc. That tended to go to some of the larger landfills before their new facilities are up and running that can actually deal with that outside of the landfill stream. And that ended up being termed deep burial. And what happens there is that truckloads of this waste would come in and there'd be an excavator to dig into an area that had been set aside for deep burial. And they could then bury the waste at that depth and backfill it with more recent waste and conventional waste in the landfill. And that happens for quite a little bit. If you can think of how much we threw out in the bins after doing our tests, etc., and the face masks, but from the health industry, the hospitals and the aged care facilities, there was a colossal volume of waste that had to be managed. The colossal volume of waste, not just from that, but these fires and floods is, is that affecting, I guess, policy with respect to opening up additional landfills that maybe they wouldn't have done? You definitely see the need for those, but you can't really overly predict where the next serious incident's going to occur. And so what facilities are local to you? I think it's a question that's not going to be answered during this conversation, but it's a very interesting one. And then we'll come to later the alternative waste treatment facilities are up and running as yet, particularly here in Victoria. And so landfills are here to stay and serve a purpose. Very good. Next question, which would be the most optimal method or tool to survey the depth and extent of an unlined landfill? Well, from the question, an unlined landfill would tend to be quite an old landfill, so it's been in place for a long period of time. There's a lot to be said for a desktop study. You can, there are people that hold or places that hold aerial photographs or any aerial photographs that you can have off the site would be really worthwhile. If it's unlined, then it's better. You don't want to be doing any intrusive investigation and punching through the basal liner. Talking to people, if there are still people around that actually worked or knew of the landfill, people that had actually surveyed the landfill in the past. We know one surveyor who's famous all over Victoria. He just has so much knowledge of landfills from years and years and years ago. In terms of intrusive investigation, what I've seen being undertaken not that long ago successfully was to actually use a piling rig to actually drill through the waste. You just don't know what you're going to find in the waste. Old car bodies, big lumps of metal, lots of timber, etc. And your conventional geotechnical drilling methods are probably not good enough to get through some of the waste. By stopping on, say, concrete or some obstruction, you may not be able to prove the depth of the unlined landfill or the waste within the unlined landfill. We've seen the use of piling rigs, which is costly, but we've seen that use successfully in the past. That's our competitor consultancy. What about geophysics? I think geophysics, I'm not sure if it'll go to the depth. You think, you know, waste might be 20 meters plus deep. I'm not sure if geophysics would go that depth, nor would it get through maybe steel plate or something like that where the signal would reflect or reflect. So I'm not too sure if geophysics would get the depth that you really need. There's no harm in chatting to a geophysics person, but that can be costly too, but not as costly as a piling rig. So seismic might be a good application there. Next question. What has been your experience with Verdeck and posi shell as daily cover? Well, it's a very short answer to this one. I don't have any experience with those, but I've seen the spray on cover being used successfully on one landfill. I've also seen a system called a tarpomatic, like a geotextile cloth that's spread and rolled out over the waste overnight and then rolled up again in the morning. So these are all these all form part of a system of cover systems called alternative daily cover systems ADCs. And they tend to only be used in trial format before the regulator EPA and Victoria in this instance, signs off that you can use them for a longer period of time. And the trial does is usually quite substantial. And therefore, it does give you some background because the consumption of and looking for daily cover soils, the old daily cover soils, that's consuming landfill and airspace and probably be a better use for that material elsewhere. I've never been involved for ADCs personally, but I've never been involved with a project that actually looked to assess them. I've heard of long term trials with EPA. I don't think I've heard of one get fully signed off by EPA. The trial continues. Oh, it seems fairly common sense. I think it's just the old tried and tested soil cover system is effective to minimize older Aeolian litter or vermin, vermin getting in overnight and then breeding generating more vermin. Yeah. Okay. Question number four, any experience with the use of landfill lids for daily cover? I wasn't quite sure what was meant by landfill lids, but I've only, as I said before, been you seen topographic used on the spray on cover use, and that's been quite successful. You only need it for overnight and then you can take the spray on system is very thin so it's not consuming much in the way of airspace and the topographic you can roll up again in the morning, but I'm not sure. I'll show my ignorance here in public. I'm not sure what is meant by landfill lids. I'm happy to take a question from the author of that through the email address later but I'm sorry I can't answer that here and now. Anyone else out there can clarify, just put it in the Q&A that would be great. Next question. Compact size is bigger better. Yes, but it tends to consume more diesel. Let's look at the caterpillar website today and they had three compactors there. The smaller of the three tends not to be as effective with with compaction and getting compaction to depth so therefore you need to place your waste in thinner layers to get the compaction which is not efficient. The middle compactor shown there was the Goldilocks compactor that was the one that tended to be used more frequently on sites and it's got bigger wheels and bigger power so you get a greater depth of compaction per pass. So a pass being every time the compactor rolls or drives forward and back over the waste. Okay, so bigger is better. Next question. Have drones been used to monitor fugitive methane from legacy landfills. Again, a woolly answer from me on this one. I would guess so I've seen methane monitors that can attach to drones for in the waste space but I've only seen them the sales. I've seen them before at conferences, etc. But I would, from that, I would imagine that has been undertaken in the past. Yeah, it definitely has. And we've been involved with some suppliers that provide vehicle mounted monitors. You know, your landfill cap and it'll give you a GPS reading and your methane concentration so this is for your sort of fugitive methane on the cap servers that you'd otherwise be doing on foot. And Grazier out of sorry Grazier I can't remember your company has airborne drones that have sensors attached to them. That is a service. So it does happen. There's the, I'm going to turn the question on you Richard and ask you a question on that. If they're mounted to vehicles is there a minimum or a maximum speed that the vehicle can go with to keep the, the reading suitable or appropriate or acceptable. And what about any fugitive emissions from exhaust and diesel vehicles. Would that pick up as methane. I think the vehicle mounted one, which was actually one that was out of a company out of New Zealand air quality limited it was an electrical sort of golf buggy vehicle so issues with the emissions. In terms of the maximum speed was probably more a safety thing now but I'm actually not sure what the maximum speed is. But if you've got airborne to be affecting the errors. I'm really not sure. I guess there's a certain period of time for it to actually compute that reading. It certainly gives you a better resolution than what you get walking around with you need that better resolution depends a bit on your aim right if you're meeting a regulatory compliance requirement or whether you're really looking to find out if there are any leaks at all for your caps probably to. Okay, good thanks. You're not meant to ask me questions now. Next question number seven can HDP landfill line is disintegrate or break down when exposed to weather. If so what can be done to avoid that. Yeah, answers yes to that but typically the the liners tend to have a protection layer of geotextile over the top of them, which. minimize any impact from UV to light, etc. But also in designs, the, the, the protection geotextile would have to be covered by a protective soil layer within a given time, so that that given time then wouldn't allow the HDP being exposed for a long enough that it would disintegrate. How long is that typically They put me on the spot here. It tends to be in months rather than years. Okay. If you've got a long slope parameter slope say It can be quite a long time before that can be covered because of the speed with which the waste is placed and therefore comes the airspace getting consumed, but our designs tend to cover that. I mean, I was in the industry designs cover that. So do you put temporary cover across the memory. Yeah, but geotextile protection layer as well. Okay. If you could ask a question about the geotextile protection layer being exposed to UV and then that's the reason why soil is to be placed within a set period. And do they then get to harvest that later or it's just sacrificial. That's sacrificial. That's, that's, that's buddy that's included in the cost of construction of a cell. Okay. So I have a question. How can you probably sort of cover this but how does one calculate the solid waste volume of airspace in the cell. We get the as built drawings of the leachate collection system which is the surface layer of the basal liner system. There's also the top of waste contours pre settlement that are embedded within the license for that cell so you know the upper surface being the top of waste pre settlement you know the basal surface and so you can calculate the solid waste volume between the two surface layers and you can you can apply that to the volume of each lift so it's really just the volume between two surface layers, but the upper surface layer being the top of waste pre settlement and the lower surface layer being the as built leachate collection system with your leachate collection system and you put your drainage layer down on top of your membrane and then over the top of that you put some kind of a protection for your geotextile. How much, how much do you typically put on top of that to protect it before you start running vehicles over that layer. We used to talk when I was at the former life at Cleanaway, it would be a couple of meters of a looser layer that wouldn't be compacted you wouldn't put the compactor on until you had two meters across the floor and that gave that protection that anything that was compacted wouldn't get into the into the leachate collection system and the reason that there's a geotextile on top of the aggregate to collect the leachate that's to try and minimize any waste getting into the leachate aggregate system and then reducing the waste between the bits of gravel that form the leachate collection system. That's a lot isn't it. Yeah, that's why it's so expensive to put these, the sales cost millions of dollars to build. So that looser material is that that's not waste that's some other. It tends to be waste but if you if you your sales team knows what waste stream is coming in so you wouldn't be putting concrete bricks and and wood timber, et cetera anything hard that could punch through the the the lining system but you would put a lighter waste that would come in a bit soil for instance could be a good one. But you wouldn't want clay because then you'd get perched leachate. So it's a balance of it getting the right material that tends to be used to call it a fluff layer. And that probably leads to some of the longer term settlements because it's not fully compacted and therefore can compact with 20 odd meters of waste above it that that massive waste will close up that lower layer as well. Do you think that's a significant problem perching of lighter. I think it happens but you can't get around it it just depends what goes into your landfill what are the materials going in. Yeah, if you think about water, water will find a way. If you've ever done any drainage in the back garden et cetera water finds its own way it doesn't go where you want it to go so I'm sure leachate will do the same within the landfill. That's a good answer now. Okay. Next question. Does the speaker have any experience with his optimization of landfill space in dealing with differential sediment slash subsidence challenges for final services that might be planned for high quality playing fields. For many landfills end up rehabilitated for passive open space uses. There is an increasing need to utilize these valuable areas for more sensitive uses, such as high quality playing fields where even minor differential sediment would represent an acceptable risk. Can landfill space optimization dovetail with future land use. There's someone there and I know exactly what the authors talk about. When the kids were playing footy junior footy I would help out and I could be the goal on but I remember at one ground that will remain nameless at Montmorency. The other goal at the far end. I could only see from his waist up because they'd bounded the center of the oval. There's so much material so that the stormwater could shed to the perimeter really quickly you could only see the waste up on the other goal. Anyway, I'm digressing. When a landfill is completely all the airspace being fully consumed and the capping has been constructed over the top. There's usually a period of anything up to 30 years where they have to have ongoing monitoring. Initially there'll be the potential to extract landfill gas so you need that infrastructure across the cap. And also they have to maintain a leachate level at 300 millimeters or so. So within the leachate collection system and no leachate within the waste mass. That tends to mean that there's infrastructure in the landfill so it could be wells where they extract leachate which means there's a pump down the well and the pump needs maintenance every three months or so. And the extraction of gas that might last for 20 years plus. So in the longer term. Yes, they could be converted into playing fields but in the shallow term there's a lot of infrastructure required to maintain and manage what's already in the landfill. What we're seeing elsewhere is not into high quality playing fields but public open spaces and down in the sand belt down Clayton way. They're doing a really good job with the capping of a landfill, a whole gear to make a victory road. They've got a lovely dog park area, they've got lots of walking tracks and outdoor gym for the people that are running around these walking tracks etc. So they are turning the landfill cap back into a public open space and an immunity for the public. But to have it used directly as a playing field the day that the capping has been signed off. And that may be a bit too early I think because you've got to manage the landfill gas and the leachate. In effect you've got a cap on top of a basal liner and you've got a lot of pressure cooker in there and there's still a lot of chemical reactions going on. The weight and the mass of that of that material if you think we've said that the densities can be about 0.85 to 1.2 tons per cubic meter so not much difference from water. That material will continue to settle through self weight over a period of time which could be 10 20 years as well so you would still have that same problem. I suppose they could build that into the capping system but to have no differential settlement or no settlement I think would be unwise for anyone to say that that would happen in the near term. It's also a cost to the landfill operator so if it was council rates would have to go up to accommodate that or the landfill fees would have to go up by a private operator. And if they were taking municipal waste and the rates would go up again so there's a cost implication for further engineering caps. I think that 30 years is based on anything technical or is it more. I mean it seems like a very arbitrary number. It is an arbitrary number but I think I think there's 20 years or so the return on landfill gas extraction diminishes. It will vary from site to site. There's a site I know from the past which was a solid inert site and it was still generating landfill gas years and years and years after it closed. Yeah, it just needs some organic material mulch, garden waste etc to have been included in a few loads and you've got something that's going to be breaking down over years within the landfill. We better keep moving. We're about five minutes over. Are you happy to keep going for another 10 minutes or so? Yeah, yeah. That's not too bad. Thanks very much for that. Next question. Are you concerned about landfills running out of airspace before energy from waste facilities are ready? Personally, not in the near term. We've got some energy from waste facilities in the planning stage here in Victoria and generally speaking from the very beginning through to operational might take about 10 years or so. We still, in the southeast, the sand belt, those landfills are all cool now, but there are some larger waste transfer stations constructed to allow trucks to take waste that are deposited a transfer station to a landfill. So I can see landfills being here for a long time yet and some of the larger ones, the mega landfills over in the western side of Melbourne and in the north, they've got years and years of airspace still. It will tailor off as the energy from waste facilities get up and running. But in the near term, talking 10 years or so, then I can see landfills being here to stay. I'd be retired by then now. Within 10 years, I'd say thank you. All right, under the Q&A. Here's the ones I haven't been able to prep. That's right, you're in all sorts now. Anonymous attendee. Love the sources and links in the presentation. Will the presentation be shared so we can click on some of these links? So all the presentations go on to the Hydrotera website. If you click on the About Us tab, I think it is. You'll find a webinars section there. And in there are all the recordings. So typically we get the recording up just about midday on Monday. So if you go looking for it, then it'll be there for you. Next question. Are there any landfills with plant that operate driverless? Not intentionally, I'm aware of. That's not coming. I think you might see alternative fuels to diesel be in the plant before the remote. But you never know. We said that about the mining industry not that long ago. And look at the mining industry now. Maybe the lawnmowers in your backyard now. Next question. Warren Pumph. Hello, Warren. Does your modelling expressly account for site-specific secondary compression of the compacted waste? Do the overfilling contours take account of the inevitable subsidence of waste over a period of years, say three to five years after placement of final capping? If so, the overfill contours can be predetermined to allow for a future beneficial use of the rehabilitated landfill. That's an interesting question. But it's a bit of a gamble if it doesn't settle within that time. I have seen that actually happen in one landfill where there was a little bit of overfill, shall we say, and it didn't result in longer-term overfill. There's a famous landfill in New South Wales, which was so deep that the volume or the mass of the waste coming in in one year period imposed enough settlement to be airspace neutral. So they had the same airspace at the end of the year as they had at the beginning. And so therefore it was like a magic pudding, no matter what you put in. The settlement took out enough airspace for you to have it open for a subsequent year. Okay. Thanks for that question, Warren. Next question from Nadia Chardery. Any measure to identify groundwater interception into the clay-lined cells, which is finally ending in the leachate dam? So the intersection of groundwater with the clay cells that we then interact with leachate? Yes, I think the older landfills in the sand belt, groundwater tables are officially lowered by 12 to 20 meters to allow the sands to be quarried or mined and sold off. And therefore that turned into landfill. And to maintain the landfill, there was a long-term dewatering system in place. And so that when the landfill was full, they could switch the pumps off and then groundwater would then recover to the regional levels. But the new landfills tend to be designed where the lowest point of the cell, which tends to be the base of the sump, that needs to be a two-metre buffer zone between the base of the sump and the regional or the local groundwater table. And so that interaction shouldn't occur. Certainly some older landfills that I can think of that you're doing. No, the landfills also might not have had wall liners. And therefore when groundwater rebounds to its regional level, then that will definitely intermix with any leachate that happens to be in the landfill cell, or still remaining there. One way to do this would be a water balance where you could calculate infiltration. I think even just on the water monitoring, the longer-term water monitoring, you can see any movement in certain metrics or parameters that would indicate and then finding out who is the guilty culprit of the impact to ground water could be difficult if you're in an area of formal industry, for instance. Yeah, I think this is more about it coming the other way, groundwater ingress into the cells. We're going to move on. Next question. Also from Nadia, sneaking in an extra one. Is landfill settlement considered in determining the finer waste level? The overfilling will provide further airspace before the cells are rehabilitated. I think it's all in the terminology that the design of the landfill is to the top-of-waste pre-settlement contour. So it's to a level that's before settlement occurs, and so therefore longer-term surface will be below the top-of-waste pre-settlement contours you would imagine. So maybe going back to Warren's question too, so maybe there's opportunity to actually, we wouldn't call it overfill in this instance, but there is the opportunity if you could realistically predict what the longer-term settlement was going to be, but that's a function of the material going into the landfill. And so the heterogeneity of that material makes it a lot more difficult to predict than it would do for longer-term settlements of soils, for instance. Next one's from Ross McFarland, I think he's facing up to that tricky earlier question. Thanks Neil, I appreciate your sharing of your acquired wisdom. Thanks for that Ross. William Dillon, it's like the last question of the day, I think. What is the thickest or deepest waste mess you have come across? I think going back to that site in New South Wales, I'm sure that's about, and I'll get shot down here, I'm sure that was 90 metres of waste. Medingly brown coal had a really thick... Ah, I have never walked on that site, I'm not saying that there are no deeper ones out there, but that was definitely beyond 60, and I'm sure it was 90 metres deep. Okay, there's two things in the chat. There's a link to the webinar next week, and I think that's all. So Neil, thanks very much for participating today. No problem. It's been great to hear your knowledge there, and thanks also to all the attendees. It's been great to have so many people here to listen to Neil. I look forward to seeing you at our next webinar. Thanks Richard, thanks everyone for joining, and thanks for your questions. Alright, thanks for that. Bye all.