 But well, good morning all thanks for joining us for our latest in now webinar series from Hydrotera. I'll give four people one more minute to come on board and then we'll get into proceedings. A few people now who have logged in so let's get underway. So what are we talking about today? Today we're talking about continuous ground gas monitoring and how to reduce the uncertainty of measurements and risk assessments associated with that continuous monitoring, but also just with ground gas measurement in general. This is something that's close to my heart, having dealt a lot with ground gas over the years and felt the need to reach out to the experts in ground gas solutions who are based in the UK because they have a few more years on us in terms of the evolution of ground gas and how it's used. It's not to say we don't have a lot of knowledge here, but I think it's always worth having a look at how others are doing these things. So we've struck up a bit of a relationship with ground gas solutions. So who are we presenting today? Well, I'm the managing director of Hydrotera, Michelle's in the background keeping us on track with this and John Naylor is joining us from the UK and thanks very much John for staying up late tonight to provide this presentation. So John has extensive experience in ground gas and the analysis of that data, but also in the manufacturer of instrumentation associated with continuous ground gas monitoring. Before we get too far into the detail, just if you would like to raise a question and please do throughout these presentations, it's great to get feedback and that's a big part of why we run these things. There's a Q&A button that you push and you can type your questions into that. At the end of the presentation, we will run through those questions and if we can't answer them, we will get back to you with an answer after the session. I'm sure we'll be able to answer most of them. Why does Hydrotera run this webinar series? Well, we like to encourage the adoption of new monitoring technologies. That's what we specialize in. We like to assist in training in these technologies and these webinars are all about training, but we also like to get more clarity of the challenges that industry are facing so we can look for the technologies to help with those challenges. What's going on today? We'll start with what we've just done, a presentation and how you can raise questions. Then we move to John, who will be talking from ground gas solutions about reduced uncertainty through continuous ground gas monitoring. Then I will talk about the continuous ground gas monitoring options that Hydrotera has for you in Australia. Then we will shift to the Q&A session. Who are ground gas solutions? They're a leading company out of the UK who specialize pretty much solely in ground gas monitoring. It would be hard in Australia to run a business just focused on ground gas monitoring. The UK market is bigger and that reason it's been able to produce some very specialized expertise. They provide consultancy around ground gas monitoring. They provide continuous ground gas monitoring services. They also provide services actually monitoring the receptors where you might have ground gas exposure. They do a lot with landfills. They have a lot of expertise assisting with risk assessments. They have developed some of their own continuous ground gas monitoring technologies. Our relationship with ground gas solutions is we've formed an agreement to collaborate with them really to support the consultancy industry sector with further knowledge that they have to bring to the table around data analytics around the continuous monitoring as well as to partner on their technology which is called Sentinel which is another continuous gas monitoring system. I'm going to hand over to John Naylor now to introduce himself and run through that presentation. Over to you John. Great, well thank you Richard and I'll just share my screen now. Good morning everybody. I hope you can hear me all nice and clear from the other side of the world as I say. So today I'm going to talk to you about continuous monitoring and ground gas in general and how we actually improve our data so we can get better risk assessments from it. Just a little bit of background about for myself. So I've probably been in the business now at least as a consultant for a good 20 years. Within that period of time, I've been a regulator. I've been a construction quality assurance engineer on landfills. I've been a consultant on the cold face. I was supervising monitoring, well construction, borehole, kind of trial fitting. I've been a lot of monitoring in the early days. I've still been a lot of monitoring these days. And then I got more and more into the consultancy side, risk assessment side as well as developing new kits and new ways and new analysis techniques to try and aid our understanding of ground gas and how we can manage those risks. So in that sort of 30 to 40 minutes, I'm going to go through why we worried and what influences we have with respect to ground gas monitoring data and why it's important to think about those influences when we're actually doing assessments. And by doing that, we build our confidence in the data. I'm going to go through a series of different tools and techniques which you can consider that might help you improve your confidence as well as developing conceptual site models and sites. I'm then going to talk about boundary monitoring, which can be quite useful for those that are looking at more sites where they're worried about liabilities of existing assets or there's potentially new waste disposal facilities going in and you want to understand what the background concentrations are in the ground so you can use those results to then forward plan monitoring and compliance. And then finally look at the sort of next generation of continued monitoring. So what are these ground gas hazards? Well, I'm just going to bring a three case that brought it to the front. And it started, in fact, it started in the UK many, many decades ago, a lot associated with the coal mining industry. But on the surface, what came to sort of development and certainly with the residential setting, the case that really kickstarted serious investigation and management of ground gas was an incident in Moscow back in 1986 where you just see the photograph there. That was a residential bungalow that got reduced to a pile of rubble. Now, thankfully, nobody was killed within that incident. But it did, at the time, create a public enquiry as to why that happened and the findings of that inquiry came out of migration of landfill gas to the property. And through the public inquiry, it brought out what is the source pathway for the conceptual model that we used and the conceptual model that we used so much these days within contaminated land risk assessment. And it also brought out the drive mechanisms for ground gas within those assessments. And in Moscow, the key driver was at pressure changes as well. We were definitely touching that presentation. One nearer to home for you guys would be the Karambor incident over in Melbourne where we had this 10 years on there, a decade on. And here, a similar thing in many regards. We had a landfill or waste depository that was migrating or lost control of gas that was migrating. I think it was several hundred metres through igneous rocks and fractures within igneous rocks in there. And of course, where we've got the infrastructure to these sites and as cities expand, this land is easily accessible, because it becomes more valuable. And of course, it gets built upon because the highways are already in landfills. And unfortunately, in the Karambor case, the gas was migrating and a lot of work had to be done there to make sure that that was managed and made safe. But we still haven't learned all our lessons over and by either. We had a more recent one in 2013. This time, Gorbridge in Scotland. Here, this wasn't actually land for the gas. This one was associated with shallow historical coal mining and workings. And here, you see those houses in the photograph, they're boarded up. They were actually affected by CO2 to carbon dioxide coming out of the ground. And then, again, evidence from various reports into the Gorbridge has identified a number of factors that could have existed in those ground gas pathways and soft pathway receptor being linkage being made. Unfortunately, in that case, several people were admitted to A&E for carbon dioxide. Thankfully, nobody again died in this. But as a direct result of those incidents, the local authority involved decided to basically vacate 64 houses and demolish them. So the actual, you know, the outcomes of not getting it right are actually quite significant. But do bear in mind as well, that these cases are still quite rare. So they're not an everyday occurrence, thankfully. But we do need to manage things better. So we hope we don't get any more of these as we go forwards. So what actually influences our ground gas monitoring data? So if we take a quick look at a standard way of monitoring, and here we've got our monitoring well at Bohol with our monitoring well in there, you can see the various sections there. So we have a standpipe in here, which at some point will have a response zone and a slotted pipe bit. A tap at the top with some kind of foam and some kind of cover. But my message to you guys is that these monitoring wells, these Boholes, treat them as unique scientific instruments. Each one has its own unique characteristics that really you can need to look at and understand in detail when you're doing risk assessments. As far as ground gas is concerned, what are the main factors? Well, geology obviously has a major part, permeability is within. Are you actually in a location where the gas has been generated or you're actually somewhere away from there where gas may be accumulating from that source and it's just being stored within the permeability starter underneath. What's ground water doing? Where does that sit in relation to your response zone and the geology and permeability of different soils? We'll see through later slides how big an influence ground water can have. Weather conditions are sort of the last go. I mentioned earlier, key role as well and don't forget also as gases do move through the ground as they migrate, we do see gas modification. So that could be logical effects, chemical effects, physical effects as the gas moves through the soil. The data that we get out there really comes from the response zone and shouldn't really come from anywhere else. If it's a well-installed well. So again, think about the data in terms of where that response zone sits. Okay. And then quite important is make sure that we have a good seal at the top because we do see a lot of installation wells in the UK where we see an atmospheric area. Which the one actually does reduce your confidence in the dataset. It's being all representative of worst case of ground gas conditions. Don't forget as well as we're drilling these monitoring locations that a lot of information is obtained from soil sampling and descriptions in the UK. We use a British standard there to do that. But while we're doing that, why not get some extra information? Take some gas readings while you're actually advancing. Maybe you've got your most saucy on gassy pathways within that well. And that could be used then to maybe more appropriate to select your response on the screening arising within that. And again, remember that seal is really important just to hammer that home. This is one of probably the worst examples that we've come across in the UK. But somebody was actually monitoring as well for 12 months before we got called in to figure out why they weren't finding any gas in the landfill. That's where the evidence has been done. And unfortunately, in this case, there was no supervision of the driller. So they did what they did to get somebody to see what's going on and make sure that that data is captured there. It's very valuable stuff. So once we've got our results, what do we do? How do we get confidence in our monitoring data? So first of all, what do we mean by confidence? Well, I suppose another word is uncertainty. And there's an IPPC document that talks all about uncertainty and it's quite useful and can be applied to various areas of science, including our sector 2 and ground gases. So here, what we want to try and move from a period where we might have low confidence, so we've got low agreement with our conceptual model, whatever it is that develops and very little evidence to go off. So the other end of the spectrum where we have high agreement with our conceptual model and we're of course, evidence that matches that as well. This obviously increases confidence goes up. So we look at that from the case of spatial data, putting in boreholes on a plan. Let's take this example, a housing estate. Should we just put a handful of monitoring locations at this size? Our actual confidence within the data that we obtain from there might be relatively low although the data from individual wells could be great. That's where confidence in the overall setting could be relatively low. So if we increase the density of monitoring locations the higher that confidence would be as we go along. It's not until we actually get quite a decent coverage where we get much better confidence on that robust evidence we need in some cases for our conceptual models and risk management tools. But we can also have when we're doing ground gas monitoring high variability in the spatial locations of ground gas. I used this example here where we're doing surface emission survey and then we modeled the relative flux from the various points across the surface and you can see just through this information here that the colored areas, particularly the red areas are higher concentrations of methane coming out of the ground. And you can see that it's not everywhere. So where you put your monitoring wells might have a big influence on what kind of data you receive from that monitoring. So again, be aware that it's highly variability in spatial as well. To add to that, not only we've got the spatial differences we have the sort of temporal differences too. Every time we go out and do monitoring people do periodic monitoring you will find differences in each of those models. So here we've just got some records here and if we just look at carbon dioxide results we can see quite variable results across that one side there. We do several of these to build up a better picture. If we did periodic monitoring in a different way here's an example where we have to do basically we sample over several minutes and every so often so every 30 to 60 seconds we actually record the values at that time. You can even see changes in that data too. I've selected this well because it's fairly stable with put gases so methane CO2 oxygen pretty much stabilised quickly you'll notice there that the methane is actually really high. So anybody that sees that kind of methane will start to get ideas as to what's going on here and another clue is actually if we look in the gas flow when we initially start to do the monitoring of the gas flow we actually do have a positive flow of over 9 litres an hour there but we can see as the minutes pass that that actually drops down to actually no flow at all. Some of you will be looking at that thinking I know what that is we'll probably find a few examples of what the presentation is further just to elaborate the point of temporal differences in monitoring I'm going to show some differences between period monitoring and continuous monitoring so here I'm just going to consider these things and I'm going to send a site operative out to take three weekly samples at a borehole, doesn't matter which borehole we're just going to be and that operative comes back and tells me that there's no methane I then send another operative out a couple of days after the first operative with the same instrument and they come back with this picture so at this time they've actually found the methane but every subsequent visit gets diminished off and the interpretation there might be well it might be just a sub-pocket of methane and every time we go deleting that and carrying on we'll find it's gone even further and maybe nothing to worry about but let's send somebody else just a couple of days later same instrument same location and they get this picture monitoring here we've got an increase concentration of methane what does that mean all of these data points are all valid they've all been taken in line in lines with the set procedures with calibrated instrumentation so which data set's right and in reality at this particular location through continuous monitoring you can see that they are all all right but the gas concentrations are so variable and it's really hard to pick a picture as to what's going on so why do we see these things well a lot of the time it's down to environmental correlations and we monitor the ground gases the gases of interest along with some environmental key environment parameters to tease out these relationships and see what's actually driving ground gas movement or behaviour so what are they what are they so what are these well there's several of them but the principle ones are pressure temperature the lesser extent and actually groundwater is quite a key factor too okay now by monitoring these variables along with the ground gases we can try to show correlations gas concentrations changes or indeed actually eliminate those correlations and so on another way that we can use environmental correlations is to try and work out how long a period of monitoring would be useful to satisfy what we call in the UK in current guidance is worst case conditions so in a lot of guidance worst case conditions is taken as falling that was very pressure so how often does that happen and how often are you likely to capture that with your monitoring well what we can do is we can take some pressure data and here we've got some data from Manchester for two years from the MetaFest station and we can actually statistically break this data down so within that data there I could tell you there's over a hundred and thirty one hundred and thirty four is greater than eight millibars within there so we can take some data and plot it as a scatter plot with pressure fall duration versus the actual size of it okay we've got some statistics up there so there's that one hundred and thirty eight we can see actually the 75th percentile of this data at a pressure fall of 90 millibars is experienced okay but also what's important about pressure falls is the rate at which they happen too millibars an hour so we've put a line in there for the eight millibars we're going to ignore everything below that now we've got some older guidance that gives us some indications of what they considered significant so British coal they decided that four millibars fall over three hours was very significant and indeed it is we can draw that line on that scatter plot as well and then we might consider a 75th percentile as being significant for our needs purposes and we put another line there and then we might also consider that longer rates of fall at one millibar are all significant and then we can start to shade that area as what we can call our worst case so pressure is low and you could do this down in Victoria wherever we are we could take that data and work out what would be considered worst case from a pressure flow scenario and indeed if we map the LOSCO on there you can see when that happened we were driving that worst case as well but what we essentially say from this sort of quick analysis is that we tend to see a 19 millibars fall in three weeks so pretty much in at least the UK or Manchester if we did a four-week period of continuous monitoring we're quite likely to find within that data a significant pressure therefore our data meet conditions so let me introduce you to time series data so this is kind of the output that we collect from our continuous monitoring equipment so on the current graph we've got atmospheric pressure and borehole static pressure on the top graph we've got the bulk gases in the middle methane CO2 oxygen and then the lower graph we've got so again we're trying to colourate the different gases of what with the environmental behaviour of pressure and water level and as you can see every time we get a deep pressure fall in these instances we get a response in this case, in this location in methane so trying to replicate that with periodic monitoring and get the same picture so get some confidence is going to be really bad but with continuous monitoring within that four-week period of period here we're collecting maybe 600 data points it's a lot more information for which you can then look at and understand what's going on let's take another example here so if you look at the photograph we have probably some bolts in the background actually that's in docks we're doing some monitoring in some docksilts for new developments going on there and we're in a tidally influenced location so a conceptual model would expect to see tidal influence with ground gas data so how do we collect that evidence? Well we could go out and do periodic monitoring let's overlay the continuous data with water level and you can just see without a shadow of a doubt the evidence is there continuous monitoring without any further analysis but that is what's driving these movements it's a really powerful stuff there's lots of other analysis tools now I've just got a few on the screen here there's lots more science but I just thought I'd demonstrate some of these to you I quite like the top left graph because this is the archetypal let's go out and monitor when atmospheric pressure is falling but the take home point here is actually as atmospheric pressure falls we can do our spot monitoring at any point along the blue line the atmospheric pressure line and apparently match with our worst case conditions so if we better look what happens with the red line of ethane that goes up and up and up and up until we get to the trough of the fall before we actually get our trough so when you're doing your spot monitoring always try to get out there basically when the weather is up that's when we're going to see the worst gas conditions usually when the pressure and the ice rain fall and so forth so look at time series graphs or actually take a time series graph and break that up if we suspect that there's some kind of patented data within there that doesn't correlate maybe with atmospheric pressure it might be associated with the time of day and indeed in the top middle graph there we can see we've lost our time there but this is the middle of the night up here we can actually see through the day the gas concentrations drop and then over the night they build back up again and drop again through the day so depending on where that monitoring has been conducted that might tell you a lot of information as to why that's happening and actually then further there's other methods as well so in the bottom left we have purge and recovery tests where we basically empty the well of existing gases with the inert gas we monitor the recovery of those gases to see how well quickly those come back in that's a useful test in certain circumstances but it's not great everywhere so the location of that has to be considered we can do concentration duration curves which is the lower one in the middle there where we're actually taking time series data we're just expressing that as a percentage of which a concentration is exceeded and we can split up into different gases so what does this tell us? well it can give us some indication of where we might be for instance with the migration so in this example in the screen we're about 50-50 so we're riding and smacking the migration location well if it was more towards a source we'd see more of the percentage so it would extend to the right and it would further away it would be more to the left and it's actually looking at these old gases in groundwater as well but by using headspace so let's have a little look at that one so what we've done here is we've actually modeled using the diffusive fixed law of ground gas coming on methane in this case coming out of a solution from groundwater and then what we've done is we've actually in the purging we could protest on how we've monitored the methane coming back into the headspace correlation between our model parameter versus our reality is stunning really and again fantastic evidence of high confidence the methane that's appearing in the problem is actually dissolving of course there are other ways of testing this and showing this but this is again another line of evidence again this is at standard pressure temperatures if you've got a deeper source pressurized sources careful about models we'll throw them out what we're saying just to give you an indication methane you can maybe 25 milligrams per litre saturation at normal temperatures of pressure so we only need about just over half milligrams to give us 5% more volume in a headspace very much so you can see with not much gas in the water we can get quite high percentages 99.5% up in the headspace which remember the spot monitoring before some other key parameters that we use with continuous monitoring as well as periodic monitoring as well as the measurement pressure and each really important percentage now in the UK practice has been doing is between monitoring to keep the gas wells closed so the taps closed so trapping in whatever the gases are well so there's different ways of measuring pressure so this is the way the gas plan principally does it and this uses a static pressure assessment essentially it takes a pressure within the standpoint okay so absolute pressure sensors and they're not interlinked and what you tend to see so here's our atmospheric pressure price there and I've put what's actually in the monitoring well underneath there you will see that they follow each other but you'll notice that the actual borehole pressure lags behind slightly so it lags the difference between the atmospheric pressure okay and you'll also notice the greatest difference is the atmospheric pressure as well so we get that generally usually typically because of permeability contrast between the air and the soils underneath and where our response is but effectively the difference between those two is known as differential pressure on the lower graph there and what you will find when you do the periodic monitoring of the flow instruments is that when atmospheric pressure is below that of the atmospheric borehole pressure as we've got here you'll get a positive flow rate okay and when we go and do the burst so atmospheric pressure is above that of the monitoring well we'll get a negative flow rate so dynamic bit there and when both are equal we don't see any flow so a lot of you that are out there doing periodic monitoring hopefully this gives you some ideas as to what might be going on with your results and particularly you'll see this where you open up a tap do you flow monitoring it might be quite high initially and then over a period of minutes it drops down to nothing all essentially you're doing is just equalizing the pressure between the monitoring events so it's basically equal with the atmosphere and that's what we saw in that first monitoring there are monitoring results earlier in the slide so a really useful way of thinking about monitoring okay the term that's applied to this kind of process is parametric okay now obviously if you were in a landfill or a generative generative source you wouldn't tend to see this you would just see the borehole pressure is always above that of atmospheric pressure and very little influence within there the other way is dynamic pressure measurement so this is what you're doing when you're doing spot monitoring you're taking low measurements okay and that started to appear in continuous monitoring instruments including like a sensor so here's some data from the sensor so at the top graph we've got static results so you can see there that the atmospheric pressure borehole pressure is very similar for us like differences in the laboratory where the middle graph is our time series data for methane CO2 oxygen and then the lower graph is actually our flow rate so by dynamic pressure what we basically do is we're opening up well within the instrument that will allow either gas to escape from the borehole through the monitoring instrument to air or air to actually come into the instrument and go back into the monitoring one that's your positive and negative flow rates okay so obviously we're doing that in a continuous mode or at least here with an hour limit that well is being opened over an hour or whatever you set it to so again when we think about our periodic monitoring and continuous monitoring we've got to be mindful that flow rate is most likely to be lower than we would see in a traditional periodic monitoring so because that has been open to more frequent and the monitoring was getting time to move okay so two important points there as well another way we can look at things is to use ternary so here we've got we basically use the sort of methane the bulk gases methane CO2 and oxygen as the end members but against the ratio of nitrogen and if we take well all three of these pots show landfill gas migration at the monitoring point of patients as you can see here we've got the 60-40% ratio of methane to CO2 quite neat new landfill gas and then over here we've got more of that at this location and then in between we have the migration effect of gas coming through as well it's quite strong there as well what we do also see here as well again a bit more CO2 scatter with these wells which could also and does also indicate that we see an oxidation going on within this pathway too so lots more information to get from your continued data okay so let's have a look at what compositions what that might do to get composition to grow so if you just take the example that we've got with the diagram from the top right there we have our source of gas it might migrate through some permeable layer and let's say we've got methane and CO2 involved in that so as that gas moves out from the generative source it might migrate just through the power of that generation or it might do it through power of that generation plus the effect of pressure changes above okay so we can get different things happening here as well so we can get known as methane enrichment happening so let's say we had a landfill gas 60-40 split if that gas then progresses to migrate through a wet ground that's under saturated CO2 what you will see that CO2 will get absorbed into the ground water and effectively when you do your monitoring further away you'll get higher methane and lower CO2 that you'll be expecting but remember we do measure percentages and not volume mass so essentially we have the same methane maybe a little bit less but because we've stripped the mass of the CO2 out it looks like we've got more okay and the reverse we actually start with the same methane but we end up with less okay now again what's going on the soils here but essentially this mechanism for this to be within the ground and microbes start to use the methane food source and combine with the oxygen to give us more CO2 and water in the process as well so again what looks what should be landfill gas when you're actually doing volume measurements looks very different but reality is still landfill gas so bear those in mind as well other areas we can use continuous monitoring including receptor monitoring I think Richard mentioned this in his introduction this is quite a very useful tool when looking at sources pathways and receptor and conceptual model pictures if we have a receptor in place and we're worried about whether any hazardous gases are getting to there you know at the end of the day that receptor is there it's always best to test this is kind of my view okay let's see if that gas is actually getting there we can do models we can show that it may or may not be there but in reality the only way to show is to test so again here we've brought in continuous monitoring gear in this case we're doing simple monitoring on the left we're doing internal monitoring on the third picture and then either side of that we also have that with sweep with PPP and PPP instruments that's in favor of something well and another way we can do a receptor monitoring it's called transect monitoring as well as we can actually take some contemporaneous data from the source from the landfill we can then take some data from the pathway so we're looking at it towards a receptor so we can actually see there is a little bit of a thing for them to be there and then at the receptor in the sub-blow here we're not seeing anything and then if we allow our atmospheric pressure you can actually see the driver it's quite strong when you get this sustained and steep fall in pressure it's the only time we have it so again collecting great evidence to supplement the development of our conceptual side and however we are going to change the issues again that's what it's all about is the development of the conceptual side the risk management practices we've had a few tools for those purposes whatever sort of tiers of risk assessment should do I know at GGS we will use the multiple lines of evidence approach to our risk assessments as well so basically we want to take our chart that we started off with beginning from 9 so move that sort of from the left of the table across as far as we can to the right while keeping good value of costs for our clients too so let's have a quick look at boundary monitoring as well so this might be where you've got a new landfill site you want to work out baseline conditions and therefore some sort of strategy going forward to measuring for compliance it might be an existing site that the client's got that they're worried about liability as it's from migration of hazardous gases so here we take this site here you can probably see the cricket pitch in the top left but essentially what we're looking at is a landfill that's then got lots of houses built around it because that's what happens a lot in the UK and we established first of all CSN so we've got our CSN best studies that's built up a good picture you might already have a lot of logs for the site you know you can build up some quite complex 3D models of your software the next stage is to install a suitable and also fit the purpose now whether that includes a series of shallow wells cluster wells, deeper wells you decide based on that CSN okay and then we go and do some initial monitoring so it might be initially that you think that you can get enough information from periodic monitoring to build that picture it might be that as a result of that you actually feel that we need some continuous models to help understand what the sort of background is as well ahead of development so you know that if you do change the region on site you're not making it worse for those receptors further out and once we've got that information so that's CSN and update what we're doing and decide boundary extents in this case we've split this up into several boundaries A through G based on the conceptual side principally in this case through what the research and sensitivities on the boundaries and it might be then that we have to decide what the monitoring thresholds are for each of those boundaries let's take an example here we've got some CO2 data continuous data but we're going to look at CO2 could be let's say a new landfill that we want to see what's going on before we tip any waste well actually just in a natural background conditions here we're getting CO2 you know 9, 10% more so now we do that monitoring we then clean and filter that data and actually determine if that's got a normal distribution or not and then standardize it okay we then do some statistics on that data and in this case we tend to just use T-max but you might choose to use a different value in there which is a percentile value up to you decide what you want to do for your circumstances and then you decide what your actual background values are your maximum background in this case we'll probably just take T-max and then we consider that as we go forward against the CSN and then pick response levels and you could have several different response levels you know from an initial sort of first tier it's gone above the background to you know second or third or more management actions get more urgent okay and then we go and do the monitoring so from that we might decide that of those boundaries we're not too concerned about several of them and we'll just do those with periodic monitoring we might decide over a B that it doesn't need to go very infrequently but we have to decide CSN in this case that we do need continuous monitoring of two of those boundaries because we feel that risk to do that focus in the data so how do we express that data well a simple way and it's quite good to get across to clients who are non-specialists just use a brag rating okay so in red might be it's gone way above a maybe secondary trigger on a response level that we do feel that that pollutant could exist in significant and we need to do something about it there and that might indicate that actually we are seeing some exceedances above our baseline and we need to look into that further but not as urgent just more monitoring and that's going on in CSN and green might be that actually everything is still as we thought it so we continue with our strategy of monitoring and then once we finalize that we maybe get to the position should get to the position where we're quite happy that the data is provided confidence that nothing's of concern maybe wants to cease monitoring so what's coming next well next generation continuous monitoring it's happening it's occurring if you want to read more about it we've co-offered the Clare technical bulletin 18 it's freely downloadable from the link on your screen and that goes through a lot of the behavior that's being activated as well so you can download that free and then the technology that we use at GDS here is the gas sensor so some of you may have heard of this but if you haven't that's what one looks like we built it and we built it for the use by for specialists by specialists it's fairly light it's very smart if we need telemetry it's got it in the UK we do a lot of shots and deployments it's not necessary required that often but it's there it's discreet and we can lock it down as you can see with our security head works there in the top black and white and we've got a range of different interchangeable sensors we can use with this so we've got the expected series there that we would see but we've also got several others as well we can change them as we need them to we've got the ability to do continuous dynamic static flow measurements in one instrument and a fairly decent battery on that too so we can tend to see four to six weeks of life when hourly monitoring out of that instrument and of course we can extend that with solar charging fully enough in the UK not that great but I suppose it could be quite good hopefully a nice introduction to continuous monitoring of those techniques you can apply thank you for listening and keep safe this button I'll probably pass back to Richard are you ready okay thanks John there's no one a bit of a freeze on my screen I'm not quite sure why that has here we go so look I think that was fantastic John to be honest in terms of understanding the additional analysis that we can do on that data and really need to design monitoring programs to be most effective both from a cost perspective and from an analysis of the actual risks in terms of this last part of the presentation is just to make you aware of what Hydrotera has to provide that continuous data and I suppose based on John's presentation be aware that we also have the resources to collect those other parameters as environmental parameters that John mentioned that secondary influences such as tidal level and groundwater level we can certainly rent to or provide you with limited solutions for those as well what do we have in our continuous ground gas monitoring fleet at the moment we have about 18 I think it is gas clams which provides you with continuous data logging we do have a telemetry module that can be attached to that but there are battery change aspects to be aware of so it depends on how long you want to deploy that for we have a large number of ambi-sense units which do provide limited data we have recently completed trials with a plexus unit which allows us to have many nodes around a landfill and it has sort of radio telemetry back to a central repository which means the total cost of where you've got many locations let's say more than five for example becomes a very cost effective way to collect from multiple locations it also has the ability to be customised for other VOCs for example and John mentioned the gas sentinel well they're developing up their latest version of that which is due for release in 12 months and at that stage that will become available through Hydroterra for use in Australia so I'll probably skip over this so we've got some time for questions and at this stage I will have a look at what we have in the question side of things I can find the question box alright we have four questions at the moment first question is hi John in your opinion is there any value in undertaking leak testing of landfill gas bores okay thank you Richard is there I would imagine that the answer to that would be yes and there's also maybe not so much yes the reason I say that is that we can actually see or we can continue to use continuous data and in fact spot monitoring data as well you'll be able to tell if you've got atmospheric ingress just by looking at the results so if you take just use a simple ratio calculator you take the sort of ratio of nitrogen in air sorry nitrogen in air to oxygen in ratios 4 to 1 okay so if you take your ground gas readings and then once you calculate your balance that remains within the borehole monitoring results so let's say that was 20% that was left as a balance and let's assume that you had 5% oxygen left from your downhole reading the divided by 20 by 5 and that comes out of the borehole and that to me would indicate you've got a leak well so that's potentially another way of looking at it or determining whether they're any good but you've also got to consider as well the stratigraphy around your monitoring well and where there is an actual pathway so actually would you expect to see air getting down there if it's all sandy soils and the response so that's only a couple of metres there you may well just have air in the ground anyway so again another straight forward answer but it's again looking at the data working out you have to take some air in the press and then thinking about site specifics to see when there is a leak or it's not a well-sealed and again you can't do a leak test as well I hope that helps Thanks for that John next question what are the differences between the flow rate measurement between a gas flux and the GA5000 I often find the flow rates recorded with a gas flux are much higher than with a GA5000 even after numerous spot monitoring events is this simply due to the ability to capture more data over a longer period of time that's a really good question we've seen a lot so good luck with that one John Okay well funnily enough I do know what we're talking about we've seen it we've seen it too with the streets I don't have any experience with gas flux so I can't answer it on its behalf but I do know that with different instruments they do tend to use different technologies for measuring flow so it depends what technology it is using and it might have specific requirements for doing that for instance we have an instrument over here that you have to tell it what the gas concentrations are first to get an accurate flow because of the different densities of the gas whereas with the GA5000 I think it's an orifice plate which just uses a pressure differential across the orifice to give it a flow so they will vary with ours and it also depends particularly what gases they've been calibrated against so most of them if not all of them they tend to be done with air and if your gas isn't recording not air and very different in terms of density or buoyancy of temperature then that can change the results to this way so you can also do this there's also a temperature flow potentially that may be the best solution again so the answer is complicated and complex but it's a whole number of factors but the key one behind that is the monitoring the sense of it is that right that answers the question thanks John it's a little bit hard to hear you sometimes I'm not sure if you're learning back from the microphone every now and again just letting you know the next question how big a diameter monument do you need for the gas sentinels is that like the head works the monument correct fairly small so we tend to use something with an 8 inch head works what's that 200mm something like that diameter and we probably need about 300mm in height so yeah fairly small really but a bigger one all the better we get much better handles get your hands down the sides we can get it 8 inch head works or monument okay the next one you should know pretty easily does the gas sentinel measure bore flow rate does indeed excellent answer are there any applications for this technology in monitoring beneath parks and forests it's an interesting question what the sort of risk driver is for those I know in certainly the UK in parks it's very common because most of them are landfills or closed landfills I don't know what it might be down in Victoria I suppose there is often incidences where vegetation dies because the root zone is saturated with the gases there's no oxygen that's wrong that wouldn't be another I suppose not all gas comes from landfills but if you start to see vegetation die back and so forth typically you're quite right Richard that's to do with generally oxygen starvation of the root zone if it's not actually contaminated soils themselves would be used there we've got one last question that comes out came in at 10.30 should the standing water level in the landfill gas monitoring boards be measured during every monitoring event if water is present in what circumstances is this a significant issue the answer to that one is yes you should as standard we record water level dips every time we're out there we also do the base dips as well so we can understand if that monitoring was silty good or not also quite useful if you accidentally write down the wrong number as you know when you're doing 50 of these things and then you need to double check with the logs that you have got the right so yes I would monitor it as well what are the circumstances this can be significant several ways really if you've got water in your well that goes above your response zone then you've essentially got a sealed system in there so you're not no longer monitoring sort of gases that are passing through the sort of unsaturated zone and the bedo zone all you're going to measure there headspace and effectively what gases are coming out of the groundwater so that's interesting to look at another one with water so we've got a heavy period of rainfall and water level rises in the ground and as that rises up and let's say it does go above the pressure in the monitoring well that goes above the response zone it certainly will you end up with a wider substantial pressure building up in that headspace and if you did your monitoring then at that time you would get really really high flow but you would see that you know if you've left that open it wouldn't take too long maybe a minute for that to even shorter for that to die down to another and we call that this thing so yes this was a few the areas there to watch out for with water Thanks very much John just to finish up great questions by the way thanks for all of those a couple of things that we've noticed over the years is soil moisture certainly plays its part in affecting these continuous readings as well so I guess just to sum up on what I've heard from John is that there are several factors that affect these measurements some are spatial some are temporal some relate to how these things are installed and it's also important to keep in mind the receptors in terms of confirming the risks that the models are telling us may exist probably the big take home for me was the the rigor of analysis with statistics to look at correlations between environmental conditions and our ground gas that is very important what hydroterra is doing with data stream which is our data hosting platform is developing these analytical approaches to allow you to plot those things against each other in real time which I think will help support the consultants making the management decisions on what to do about these things John many thanks for today and many thanks to all the attendees it's been a great turnout for this session obviously something that's of interest to a lot of people and that's it from hydroterra for the day thanks very much if you want to get in touch with John just flick us an email to hydroterra we can facilitate introductions if if you're after continuous ground gas data give us a call and we can assist you with that as well alright many thanks for your time thank you