Well, thanks everyone for joining us today for another one of Hydrotera's webinars. Got a fantastic number of registrants today. It's close to a record, if not a record. So clearly this topic is of interest. Today's topic, acid sulfate soil management, exploring recent changes to the guidelines. So on behalf of Hydrotera, I'd really like to thank Sue Ellen Deere and Christy Williams, who both are land resource officers with the Queensland Department of Resources. They've been busy compiling new guidance in this area. Before we get started, I'd like to begin by acknowledging that we conduct our work across this great land. And for that privilege, I would like to thank the traditional owners. Hydrotera respectfully acknowledges the Boonawarung people of the Kulin nation, where we are located today. We pay our respects to their elders, past, present and emerging. So I'm Richard Campbell, Managing Director of Hydrotera, and it's always a pleasure to host these webinars. There's a picture of Sue Ellen, which is the Senior Land Resource Officer with the Queensland Department of Resources and Christy Williams, Land Resource Officer also with the Queensland Department of Resources. So we're lucky today. We've got two presenters, and they're going to spend a lot of time going through their new guidance documentation. A little bit about Sue Ellen. I'm just going to have to shrink the format here. No, do I do that? There it is. Sue Ellen is a Senior Land Resource Officer with the Department of Resources since 1992. She has worked in Central, Southern and more recently Northern Queensland in Soils, Land Resource Survey and Acid Sulfate Soil. Sue Ellen is based in Nambour and still does the old Acid Sulfate Soil Assessment for major infrastructure projects, presents workshops for local government with Christy and is writing lots of guidelines at the moment for Soils Land Resource Survey, Land Suitability Assessment and Acid Sulfate Soil. Christy is a land resource officer with the Department of Resources, starting work in Brisbane in 1999. She was part of Quazit, the department's Acid Sulfate Soils Group for seven years and was heavily involved in all things Acid Sulfate Soil, running workshops, writing guidelines and doing site assessments. Christy has been based in the Toowoomba office since 2006 and while she's still involved in Acid Sulfate Soil Work, these days she works more on normal soils, salinity, soil conservation and land resource assessment. We love your questions and expecting lots and lots of questions today given the number of people here. To do that, you use your Q&A button which is at the top of your screen and we will read out those questions. We also have a number of early bird questions that have come in so really appreciate those as well. We do the early bird questions first. Why does Hydrotera do these webinars? We like to share knowledge, we like to facilitate education and we like to work with industry leaders. So many thanks from our presenters today for showing us some leadership in the area of Acid Sulfate Soil. Before we move to them just a quick advertisement if you like to mention we've got a groundwater sampling workshop coming up. If you're interested in getting groundwater sampling training please get in touch with Hydrotera. Alright so without further ado I will hand over to our presenters. Okay well I'll start today so thanks and welcome everybody. So Christy and I are really happy to be here today to talk to you about the wonderful world of Acid Sulfate Soils. It's so great to see so many interested people logging in. It's a bit sort of strange doing this as a webinar I have to say. Hopefully you'll get some of my jokes and hopefully at least Christy and Richard might laugh so I'll know. So it really demonstrates that after all these years there's real this is this a new generation of scientists and engineers along with us older folk who are still interested in this topic. I mean especially since I think this is a second Acid Sulfate Soil themed webinar that Hydrotera has run in the last six months or so. This many people on board yet pretty exciting. So it's clear that there's a real demand or first for this knowledge on Acid Sulfate Soils. So we're going to do a bit of a tag team approach today. We couldn't really decide on who should do what so we decided we'll just jump in and out so it might be a little hopefully won't be too clunky. Hopefully we'll get some fairly smooth transitions between us. So over to you Christy. Thanks to Ellen. Yes it's lovely to see so many people online and yeah I'll laugh at your jokes even if nobody else says that's all right. Given that the numbers of people that are online I'm assuming that there's quite a wide range of knowledge and experience that you all have with Acid Sulfate Soils. There's probably some of you online who deal with this stuff like every day there's an Acid Sulfate Soil investigation report or a management plan or lab results that come across your desk every day. Some of you maybe only a couple of times a month and then there may be somewhere it's only a couple of times a year so we're not going to spend a lot of time today talking about what these soils are or how to identify them or where you find them how many boreholes you should dig what lab results or anything like that. We are doing a deep dive straight into the management side of it. So if you're not super familiar with this topic then it may be a little bit full on but there is lots of other information out there that you can go to if you want some more stuff. As Sue Ellen said Mark Stuckey gave a great talk for HydroTerror at the end of last year. Our Queensland Government website has loads of stuff on Acid Sulfate Soils on there. I know that Southern Cross uni do professional short courses on this topic there is stuff out there. Sometimes the problem is that there's so much information you actually don't know where to go. You can also always contact Sue Ellen or myself we're happy to talk after the webinar if there's further information that you'd like. So I'm going to go really really quickly like a couple of slides and just describe what are Acid Sulfate Soils and why we care enough about them to manage them. When we do our training workshops usually we spend a couple of hours introducing this topic so I'm going to give you a three minute special. So if I can go to the first slide please Richard. So what are they? First up they're soils and sediments that contain iron sulfides okay that's what makes them special compared to everything else. The main form of that iron sulfide that's present in them is something called Pyrite and that's FES2 and that's some Pyrite crystals under a microscope that you can see there that Lee Sullivan took. So those Pyrite crystals are extremely small with a really large surface area which means they're highly reactive. You can see they're kind of like little raspberry shapes they're called framboids they're big surface areas. You may have heard of Pyrite before when you talk about fuels gold in a mining sort of situation where you can actually pick the chunks of Pyrite up and play with them. This is the same stuff chemically but it's such a big difference in terms of their surface area so these things react really quickly and so when they're exposed to oxygen these soils are disturbed and that can occur by physically excavating the soil or it can occur by lowering the water table so both things can disturb these soils. The Pyrite breaks down really rapidly undergoes a whole pile of chemical reactions called oxidation and we generate sulfuric acid which comes from that little S part and we generate lots of soluble iron. So if we go on to the next slide we talk a lot about potential actual acid sulfate soils and actual acid sulfate soils. So potential acid sulfate soils are before they've been exposed to oxygen so the iron sulfides in them are unoxidized. They are sitting there quite happy they have a neutral pH they have the potential to oxidize if they're disturbed but so if you were to go out right now and stand like underneath a mangrove what you're standing on is potential acid sulfate soils and everything's all fine and dandy if you leave it alone. Next little bit please Richard if you once they start being exposed to oxygen they start that oxidation process they become actual acid sulfate soils where they are actually acid the pH has dropped down to less than four and they often contain some of the byproducts of that oxidation which is this little yellow mineral called jaricyte and jaricyte's a really good indicator of our actual acid sulfate soils it likes to hang out when the pH is about 3.7 so there's not a lot of things that do that in the natural environment. Now okay so that's what happens when you know what's the difference between them you can't have a talk about acid sulfate soils without chemistry okay there's loads of chemistry involved and I'm going to do one equation today and if you're not feeling like doing chemistry at lunchtime just read the words underneath it but chemically it's what's happening what's the overall oxidation reaction is that you have pyrite plus oxygen plus water and you produce iron and sulfuric acid and that iron and sulfuric acid are not the only things that acid reacts in the soil affects it mobilizes aluminium and other metals and things that are free too so you get like a bit of a toxic brew that can come out so if our soils are the disturbance is poorly planned or managed we can get lots of problems water quality environmental damage infrastructure human health concerns there's a whole swag of things that can go on so that is my three-minute special about what these soils are and why we worry about them and I'm going to hand over to you Sue along for the next bit okay well um so we're here to talk about this beautiful oil you can't see it I can't see it there is it so I won't hold that one up again okay oh hang on it'll work on mine I'll hold it up there see there's a document there you go okay perfect okay so there's so many different guidelines out there on acid sulfate soils and then of course there's so many different pieces of legislation and policy as well to to navigate and um we've got sampling guidelines we've got lab methods guidelines we've got dredging guidelines groundwater guidelines mbo guidelines in Queensland as well we've got the monitoring and sampling manual for the environmental protection policy that Desi put out and if you can press the slide Richard and then when it comes to management of course there's really only one guideline so although in the past many of the different jurisdictions have strategically grabbed certain sections out of them to put in to use for their own regulatory or policy environments so hopefully now that we've got an updated version the links to all of those different pieces of legislation and policy and guidelines maybe hopefully they might be a little bit more clear than they were in the past and hopefully now we've got some greater consistency across the country but bearing in mind you've got to bear in mind that there's always going to be specific state or local government requirements that may override some of the more general advice that we have in the asset source management guidelines so excellent switched already good okay okay so we've wrote the guidelines effectively to offer procedural advice about how to avoid environmental harm and to effectively try and demonstrate best practice this provides more certainty to industry and regulatory decision makers so we all sort of know where we stand the guidelines are really both focused around nine management principles they used to have eight but we've you know we decided that a ninth was necessary because we sum about with our knowledge increases our um things that we need to be covering off on these guidelines as well which is why we've we've grown management principles we also have a good section on asset source or risk assessments which are another fairly substantial part of the guidelines and they outline management strategies such as preferred management strategies high risk management strategies and unacceptable management strategies so excellent and one more thank you so all of those management strategies carry environmental risks so even those preferred management strategies they're not necessarily suitable for every site so each site is completely unique you've got different soils different site characteristics different ground water hydrology some areas in the middle of an urban infill environment some are a big you know green green sites as well so that's why risk assessment is so important to really look at the big picture so that the management on the site actually matches the risk okay so we thought we just dabble into a little bit of the process because it's been a long process so we we sort of feel that we need to share the history with you guys so so basically um back in 2002 Christy and I were involved in writing the original version of the soil management guidelines at the time all we had was the also sampling guidelines that um the that actually went into a bit of management a bit of legislation a bit of lab stuff a bit of everything but but predominantly sampling as well so um Colin Birney wrote that back in 1996 um and the other major document that was used was the New South Wales uh manual the nine I think it was released in 1998 so in 2014 we updated the guideline because our knowledge and expertise had grown along with industry's knowledge and expertise so we needed to update the guideline then of course in 2014 the national guidance was was released so sorry sorry correct that's what I that's what I said in my head okay so it didn't take us long to realize to notice some of the differences between the Queensland guidelines and the national guidelines so um we quickly updated our website to try and um stave off you know some inconsistencies but we soon realized that we needed to do more um then so we did that in 2019 in 2020 during COVID lockdown we started rewriting the guidelines and in 2021 we formed a new industry reference group and we started consultation with that group so and I'm pretty sure some of those people in our reference group are hopefully listening today uh thanks for um putting up with us the rest of you for sharing your expertise and an interesting fun fact for you is that four members of our original industry reference group have been there for all three versions of the guidelines so yay to those four people who've generously evolved with us and with the Queensland guidelines so they're assets of it's all life is just like just like Christy and I and Gus as well is our other author are the remaining current Queensland government employee okay so anyway I digress so um we compiled the feedback into a gigantic spreadsheet and we did notice that naturally when you consult with that many people there are a variety of opinions out there and so we identified a series of issues that we needed to resolve before we could publish so we were fortunately able to get together at the national assets of it's all con conference in Adelaide last year where we just um got up and invited everyone to come along join our reference group not everyone came but um we did have a uh a big bunch of academics and industry reps and regulators who all sat in and um shared some um we developed we developed some fairly pragmatic solutions to some of our problems so it's a really good thing having these roundtable discussions with industry regulators and academics and um yeah we got we got some good outcome so then we released some further we came back and made another gigantic spreadsheet um compiled it sent it out to the reference group again and then on world soil day last year um can move over next one please Richard then um on world soil day last year we were able to release the guidelines which we're very excited about so um but I think we actually realized it was actually in our library catalogue of the Friday beforehand so I was on holidays by that stage on rec leave by world soil day so Christy had to got the pleasure of hitting the press button send it to all our local governments and industry people and the massive big um Christy's got a great big database of all of these people interested in assets of its own so we got it out to them on world soil day okay next one please Richard so um throughout all of our meetings and and feedback sessions there was really an overwhelming consensus that what we needed was consistency with the national guidelines we wanted um there was a need for greater certainty and clear direction to quote one of our experts industry is seeking more than an ill-defined on occasion statement or or another one the statement may well prove to be an open door to inappropriate management so with that sort of feedback we knew that we were talking to the right people so effectively um we after all this consultation we made some amendments to the purpose um any of you who know the 2014 guide will know that the purpose went for many many pages I think it's now one small paragraph we got rid of one chapter as well although we added lots of extra stuff as well at the end we added the extra management principle we modified risk assessments we looked at the neutralization section the verification testing section the non-sulfuric acid sulfate soils self-neutralizing soils and then we added some stuff about we looked at had a closer look at small disturbances the filling section and closure reporting we added heaps of new stuff like heaps more as tips because we love those conceptual site um models checklists unconfined groundwater dewatering sections stuff on dredging remediation case studies water quality parameters and then my personal favorite is a poem at the end on the sulphurization process okay so um obviously we can't go through everything today so we're just going to sort of try and discuss just the major themes of the guidelines and then the major changes along the way okay so one more please Richard so we're going to start off looking at risk assessments so version 3.8 of the guidelines version 4.0 of the guidelines and version 5 have all reiterated that a risk assessment should always be done before you disturb any acid sulfate soils so we're going to keep reinforcing that a bit today it might sort of if we tell it tell you that um if we repeatedly remind you hopefully that'll sink sink in um the management guidelines highlight this right at the beginning of the guidelines you have to do a risk assessment before you disturb acid sulfate soils okay so a risk assessment involves NASA investigation soils analyzed in a lab and that's not with the field tests and groundwater investigation they all had to be done in accordance with the national guidelines okay so what is a NASA investigation well it's not changed since Colin Birney came up with the concept back in 1996 so it's a desktop assessment followed by site inspection with some soil sampling laboratory analysis and then reporting it results so too easy okay and the risk assessment can also benefit from the use of conceptual diagrams so we're very fortunate that um PSK and Silvana in Brisbane generously did some workshops for us and then we stole some of her conceptual site models so thanks to thanks to PSK okay so they're basically planning and decision-making tools that you can use and they're just really good because they have an illustrative representation of of the things that can go up on on a site right one of the other changes to the guidelines is or additions is that we've included the definition of a suitably skilled and experienced person in acid sulfate soil science so um the science of acid sulfate soils is really complex and especially when you've got interactions between many different disciplines so engineering civil engineering soil science geochemistry groundwater hydrologists so and the risks to the environment to the built infrastructure and human health are fairly significant if things go wrong so it is a really specialist field so we thought it warranted a fairly detailed description of what constitutes a suitably skilled and experienced person in acid sulfate soil science we also introduced the concept of independent third-party review nothing new out there in the world of contaminated land but new to the world of acid sulfate soils so it's uh can be a component of a closure report and now i'm going to hand over to Christy okay cool thank you uh next slide please Richard so what we do yes on this slide it's it's are you saying that it's mandatory for them to be a certified practicing soil scientist to be competent no we're not saying it's mandatory we're saying it's recommended that that you're either a certified practicing soil scientists or a registered soil practitioner or you're some sort of an accredited environmental scientist or engineer with 10 years experience you can be any of those things and that's um considered um meeting the definition yep okay thank you all right so management strategies um yeah we've done all this stuff talking about what we've done to get to the guidelines we still haven't told you what the management strategies are so the number one management strategies is always avoidance it really should be considered for every site it's the cheapest and easiest option like all of the management strategies and like what Sue Ellen just said it um really depends on having a thorough site investigation you can't avoid something if you don't know where it is and so that avoidance can be as simple as you know if you're doing a two-story basement car park and you suddenly decided we've encountered acid sulfate soils at several meters below ground you might be able to change your site layout and everything so it's only a one-story basement car park things like that to try to avoid this disturbance it is always the preferred strategy it's the number one management principle in the guidelines but we also know that disturbance is not always avoidance is not always possible so if you are going to disturb it the preferred management strategies for dealing with acid sulfate soils are minimization of disturbance neutralization hydraulic separation and strategic reburial and we'll talk a little bit about each of these through the document so that no not yet Richard go back so the management guidelines for each of these preferred management strategies they outline the environmental risks for them because as we've said even these preferred ones can things can still go wrong so there are still environmental risks associated with them the guidelines talk about the management considerations and the performance criteria that you have to meet we've made a few tweaks in the guidelines to minimization of disturbance hydraulic separation strategic reburial but the one we've most played around with is the neutralization chapter and it is by far the longest section of the guidelines because it is the most common management strategy that people use now I'll go to the next one just the title before I just go into neutralization and some of the changes there I just wanted to talk really quickly about net acidity and so if you're familiar with acid sulfate soils you'll know what net acidity is it's basically you've done your site investigation you've got a sample you've sent it to the lab you've got lab results and they'll report back your net acidity which is basically saying how much acid this soil could produce if you were to dig it up and just leave it alone and the net acidity now we've changed the the the formula for it but the net acidity once you have those values you compare it to your action criteria and the action criteria are like a trigger to say when you need to manage them your net acidity is higher than the action criteria you need to manage those soils and the action criteria differ depending on your soil texture and how much soil you're going to disturb if you're disturbing more than a thousand tons of acid sulfate soils or soil then the net the action criteria are 0.03 percent s or 18 moles of hydrogen per tonne so if your net acidity exceeds that number of 0.03 percent s then you've got to manage those soils just the thing with the action criteria is that if your net acidity is less than the action criteria it's still an acid sulfate soil but you just don't it's not treating the need for management so I forgot to the next little point here so the now our net acidity calculations align with the national guidelines so net acidity is potential sulfidic acidity plus actual acidity plus retained acidity so if you remember that talk right at the start where I said we have our potential acid sulfate soils sitting there below the ground they're all full of pyrite that pyrite part is our potential um sulfidic acidity if the soils have started to oxidize and they're already producing acid you'll also get measurable actual acidity which is our exchangeable part and retained acidity and the retained acidity is that stuff that's locked up in jarocyte and shwerpmanite and other minerals like that so you have all these acid components of your soil which contribute to the net acidity now in some soils you do get alkalinity in them or acid neutralizing capacity and obviously acidity and alkalinity that kind of counteract each other so if you go to the next point the major change is that that you can only use a soils inherent acid neutralizing capacity or ANC if it's been corroborated by other data that demonstrates the soil material doesn't experience acidification during complete oxidation and this is exactly what the national guidelines have said so that's a way of saying how do you corroborate that how do you approve that well it's basically a range of kinetic testing that you have to do so slab incubation tests or chip tray tests and things like this when this first sort of came out as a concept there was a bit of pushback from industry because the thing with those kinetic tests is that they take time you're talking about a minimum of two months sometimes longer to get the results from that and so everyone was like oh do we what are we going to do about this sort of thing and we've worked through industry and I'm going to spend this slide and next one sort of talking about the resolution that we've came to and why it's important to go with this national approach so I guess the other thing I really want to point out is this this consideration of acid neutralizing capacity it's only something to deal with if you're talking about a self-neutralizing soil it's not actually super super common I've been in this field for about two decades which is a really long time and I've come across assessing a lot of acid sulfate soil management plans and investigation reports and I reckon I can count on both hands the number of times that we've had something with self-neutralizing self-neutralizing soil in a measurable ANC that we have to consider so it's out there but it's not super super common so if I go to the next slide Richard which is about our self-neutralizing soils they can be partially or completely self-neutralizing and it's due to an abundance of naturally occurring calcium carbonate which is usually in the form of shells so they have an alcohol pH greater than seven and a half often that's greater than eight and a half we've done mapping in Queensland and I know other jurisdictions have done mapping too in Queensland we've identified small areas of this self-neutralizing soils usually in harbour and estuarine sediments and things like that in the last couple of years there's been a lot of research mainly coming out of some of the universities looking at this self-neutralizing or the ANC component and what they've actually found is that shells need to be less than half a millimetre so that's pretty small and they're the ones that are going to actually have some ANC some self-neutralizing there so I'm just looking at that less than son on the slide shows that that should be the other way shells greater than half a millimetre other ones that are going to not be any good so the shells have to be teeny tiny and that's what the lab results have shown and the reason for that is twofold the biggest shell fragments once that acidity gets in with the calcium carbonate in the shell you can get iron and gypsum and other insoluble compounds which are coat the shells and then so they're no longer effective also samples which are then sent you collect and send them to a lab after they've dried the sample they'll grind them so break all those shells up and so you're getting an overestimation of what the acid neutralizing capacity could be and with there've been examples over in Western Australia for instance where they've done their site investigation perfectly they've shown that they had these ANC results so they substantially reduce liming rates and then they've gone on and implemented that on site and they've ended up with a whole pile of acidic drainage and things because the ANC was an overestimation of what was actually available in real-world conditions the reason why they've done this change of saying yep let's just stick with the ANC that's probably been corroborated by other data is that it's due to the uncertainty of whether the neutralizing material in the soil is quick enough to counteract the acidity so it's about those reaction kinetics you remember something that's finally ground in the lab is that real can that translate to real-world conditions when you do your field testing as part of an acid sulfate soil investigation you do your little field tests with pH F and pH Fox these self-neutralizing soils will both have a pH F and Fox above seven and a half so if you're starting to see that in your field condition in your field testing that's when you're like okay maybe I need to start thinking that self-neutralizing soils or some sort of ANC is apparent and you can start that process of doing those longer-term incubation tests kinetic testing and you've still got time throughout the development assessment process so that's why a bit of the background on to the change of that so if we'll go on to the next slide we'll actually talk about neutralization as I said it's one of the most common management techniques for acid sulfate soils it involves incorporating alkaline material into the soil and there's got to be enough there to neutralize all your actual and retained acidity that's there right now plus all the potential acidity that could be generated in the future if those iron sulfides oxidize so because we need something that hangs around you really need some sort of sparingly soluble insoluble neutralizing agents and that's why fine ag lime or calcium carbonate is the most common one so during this talk if you hear us talking about liming we're talking about fine ag lime so it has like a purity of about 95 or probably 98 percent a really high effective neutralizing value it's a good stuff so it's really easy to say I'm going to lime treat these soils that'll be fine and while it is a relatively simple process you know we've got the equipment to do it you know how to do it there's a huge pile of considerations to do neutralization and sometimes people I think don't quite think enough about it and that's why we've written so much more I guess into this chapter so texture obviously pays a big deal I'll talk about that in a second impacts on wildlife if you're doing your site is next to a naturally you know acidic environment you don't want to chuck heaps of lime and alkaline product around and potentially change the chemistry in your surrounding environment choice of neutralizing agent there are different things out there other than ag lime that can be used obviously calculation of liming rates isn't this straightforward like you can get a sample one sample get one net acidity result work out one liming rate but then how do you do that across an entire site where you might have variable numbers net acidity here net acidity there like what how do you do your overall liming rates you've got to think about meeting verification testing you actually need space to do it and what else is there and you've got to be able to track your soils and things like that so there's a lot of things to think about when you just say I will just do neutralization so we're going to the next slide thanks Richard bit about texture so sands they dry quicker so they're easier to work they generally have lower levels of iron sulfides and they have but they have a low buffering capacity and they can start oxidizing really quickly like within hours of being exposed so you can generate quite large volumes of contaminated leachate quickly the next slide which is about our marine clays at the opposite end of the spectrum these things can be really difficult to work treat and dry they are wet they're like the consistency of toothpaste in some cases and so it's pretty tricky to it takes time for them to dry out enough that you can actually work in it because neutralization relies on the fact that the ag lime has to be incorporated into the soil like it's got to actually mix and that's because ag lime is so sparingly soluble it's got to be you've got to actually place it where you want it to go it's not going to freely move that easily that readily so clays especially can take a really long time to dry out especially in wet season in say tropical north Queensland um so they can be fun to deal with at times as well so the next slide um is about our treatment pads so we did a really simple fides I don't know diagram back in 2002 we've improved our artistic skills slightly since then and we've updated this to just show all the components that's necessary and I guess the big thing about a treatment pad is that it has to be hydrologically isolated we want to keep everything in this area and that's why bonding is so important the leachate collection drains having a compacted and pervious base to stop anything moving downwards it must have a guard layer of agricultural lime so that's placed on the ground on top of that compacted base before you put your assets off at soils on there to that required treatment and then you're mixing in with the lime and another thing when you're working out liming rates is that we always incorporate a safety factor and the minimum one is about 1.5 and that's just to account for ineffective mixing um any coatings and things like that on there so we add a little bit extra um on top of the net acidity results and that's been recommended since way back when so that that part hasn't changed so if you go to the next slide these are actual treatment pads oh yes just before we do so impervious base um are there actual parameters on impervious yeah we we we haven't gone down to specifying like hydraulic you know conductivity and things like that but there are there are some extra there's a whole paragraph in there and the guidelines about it so i'll read it out to you but we can have a look at it later you can either bring in clean fill and that becomes your you know impervious base or depending on the site characteristics you can compact this all in situ so that's a different change doing the in in situ compaction so but we haven't sort of said it must have you know hydraulic conductivity the permeability of this or whatever like that we haven't gone into that specifications so these are just some examples of treatment pads in real life they range from I don't know the size of a house to something gigantic just depending on that space that is available and you can see can I can you see my mouse moving there no no that's right see the picture in the top left like they've actually gone to the effort up there of putting you know that hdp hdp liner around their bonding so people can do extra things as well so that's just an extra thing that they've gone through if you see the treatment pad in the middle bottom how it's kind of a weird shape well this is some of the site issues that happen that's on the Cabocha River where they were really confined with sensitive environment and that was the only place for the treatment pad but it was also where a cultural heritage issue was so they had to basically build the treatment pad around it so there's you know variations to these things if you go to the next slide Richard this is another example from PSK environmental so thanks again to Silvana just to show that when you say yep lime treatment there's a lot of things to consider you need earthwork strategies you're saying I'm digging up soil over here it's going to this treatment cell it's getting this rate of lime and then once we pass verification it's going to be moved somewhere else so there's the earthwork strategy you've got to have space to store your ag lime space for any stockpiling of soils you need all the collection drains and things and see that photo up on the top right with all the iron leaching that's why the drains and the bundling so important is because these soils will be oxidizing on those treatment pads because it's not an instant reaction of ag lime and acid and everything's fixed instantly there will be some byproducts and that's why it's so important that the treatment pads are contained for go to the next slide this is about performance criteria for neutralization so how do you actually prove you've done it and it's worked the first thing is the same that hasn't changed but we have introduced this thing about record keeping demonstrating what safety factor and you know has been applied and that's as simple as receipts of lime purchases taking photos and how you actually did your lime calculations the other performance criteria haven't changed we've basically got to say once the soil has been limed pH has to be above six and a half and your titratable actual acidity which is a lab result has to be zero and you've got to make sure that enough of the neutralizing agent stays there the next slide just really quickly is talking about the verification testing so this is our post treatment confirmation that enough is there so once the lime has been added to the soil and it's gone through that mixing you take samples and the guidelines specify the sampling rate for verification testing depends on the volume of soil and your original um net acidity results you send those samples off to the lab and they'll get all your lab results all done and you get your verification net acidity which is basically adding up all those components of it and that's got to be less than zero there is some allowance in the guidelines for individual samples to exceed it so it can be slightly above zero but it depends on the texture but there's like a sliding sort of scale this sample and the surrounding ones around it you can't all fail basically because if you do fail verification testing you've got to re-treat the soil and so that is another complication into it all I might hand over to you now Sue Ellen I think you want to do the next part yep yep okay so um some of the other preferred management strategies that the guidelines talk about strategies to minimize groundwater disturbance so there's actually lots there's lots of there's quite a bit of information in the guidelines about how to minimize disturbance but we'll just look at minimizing groundwater at the moment um so in this diagram thanks again Silvana um you can see we've got a fairly simplistic landscape we've got an actual acid sulfate soil and a potential acid sulfate soil then you go in and you dig a big dry hole dewatered as well um and you can see that when you start dewatering you'll get the cone of depression and that's where you'll get some um oxidation of acid sulfate soil so you'll get some you know some metals and and acid and sulfate and things like that generated so one of the um means of trying to minimize the amount with that would form the extent of the cone of depression is to put things like sheet piling in or diaphragm slurry walls something that our engineering friends told us about um so that effectively could minimize the extent and the duration of any dewatering um doing things like the guidelines frequently talk about doing excavations in a series of small cells so you're only dewatering small areas rather than a one great big dry hole at the same time um you need to do verification monitoring of whether that hydraulic control is effective uh yes well that would be in the groundwater management plan that would be associated with it as well yeah um yeah i think we'll move on to oh well just before we move on you don't have to go back but um i think for more information on we we sort of borrowed things from the national guidelines and and WA guidelines about groundwater disturbance but for realistically for groundwater you really need to be looking at the national guidelines are going to a way more detail we've just got snippets in our guidelines so talk to an engineer as well not necessarily a podologist okay next slide please okay so some of the other preferred management strategies that the guidelines talk about is one called strategic reburial it's basically the excavation of potential acid sulfate soils and then you place it in the bottom of uh avoid preferably in not preferably definitely in reducing or anaerobic conditions so basically in those conditions the sulfide oxidation and then acid generation is effectively permanently precluded so it's still used a lot um we've updated some of the diagrams in the new version of the guidelines we've got an artist in our team as well so we we snabbed her to help us get our graphics a little bit better um thanks Helen and um i think we sort of think you know climate change might bring some challenges to the long-term sustainability of this particular management strategy because for it to work the um the past has to be in reducing conditions in perpetuity so there are some challenges for that particular management strategy as well the guidelines also not back back Richard okay the other management strategy that we talk about is hydraulic separation which is effectively the partitioning of sediment using accelerated differential settling um in this section of the guidelines i think we just changed some of the verification testing rates to make it more consistent with other parts of guidelines um we used to call this this form of management hydrous loosing or just loosing for short it's not really used a lot these days as far as we can gather but it was instrumental in the creation of the kawana waters um it was the olympic rowing um rowing course in the in the olympics um and it was also used a lot at kawana i mean it's twin waters in the sunshine coast and a lot of the gold coast sandy canals back in back in the day but yeah as i said we're not not entirely sure but we don't think it's it's a widespread or common thing these days okay next slide please so we'll just talk a little bit about some of the non-sulfitic acidic soils so many soils can be naturally acidic and that acidity is not from the oxidation of sulphides so we've got coffee rocks and peats um and those really heavily leached iron and aluminium rich tropical soil so the the slide up the top right hand corner that's classic um soils around any of you know sunshine coast around like karoi bar and like araba they're just highly leached they will if you dig a hole in them you will get these right you know throw a lot of acid and aluminium sorry into the water um so you will get these crystal clear lakes but eventually um they will stabilise just um after a while so they're a bit different to an acid-sulfate soil where you're going to get a long-term acidity situation um the problem is that the lab methods TAA doesn't really distinguish between the acidity sources and it's not always easy to predict the history of the proton so another problem is that these soil some of these soils can contain really really small pyrite with no ANC we haven't really looked into those too much in Queensland in our mapping projects but we we know that they've found them in WA and we suspect they might be in um like gari and some of our coastal islands as well so marine marine peats um particularly can be particularly nasty um difficulty with these soils is that talking to one of our guys i can find off Queensland who's done a lot of work in these soils and he said they effectively look the same as normal peats but apart from the smell so you will get the you know the rotten egg gas when you dig it up but he said they look the same the difference is these soils can have sometimes four or eight percent um sulfur in them so they're pretty nasty when they go off they'll acidify entire um creeks and for a long time so it's not just a one-off burst of acidity into the environment um in terms of acidic soils um the guidelines talk about looking for signs or evidence of sulfide oxidation so this could be things like garroside, rotten egg gas, smell, mottles, shrimp and like things like that sometimes there can be underlying um synthetic materials underneath these soils as well um when so it's really complicated because when the source of un of acidity is unclear you know now the management's not always straightforward which is why you need to really go in and do a risk assessment to categorize that risk in some situations just to complicate the whole situation you've got um multiple sources of acidity and you've got highly organic um acidic ecosystems and then underlying that you've got the sulfidic soils so we've got a classic example of that behind Coulomb where we've got pleistocene coffee rock and we get the um sulfidic soils underneath the pleistocene coffee rock and these are I think 10 or 15 meters deep um so the only reason we really found them is because we you know dug up very very deep hole so it's sort of it's basically with these soils it's about minimizing the risk but you've also aligning that risk with the values of the natural environment because we don't want to change the composition of an acidic ecosystem but we also don't want you know the nasty consequences of an acid sulfate soil being um impacting the environment as well next slide please Richard just before we do so not familiar with the term coffee rock it's coffee coffee rock oh that's a great picture there um so it's basically sort of ingerated sands um we get they're quite common in um around around the Sunshine Coast and all up and down the coast okay yeah and they're generally a pleistocene um so the guidelines also talk about um high risk management strategies so we've introduced one new one to the mix this time we we've done a section on basements and in other in-ground infrastructure where that are below the water table and that's really um to accommodate basements and elevated shafts and tunnels and car parks and things like that which um we have a lot it's it's quite topical in the middle of the Brisbane CBD at the moment because there's a lot of building going on and you've got some barely nasty marine clays down there with you know six percent salt go down there and then all of these structures down there so they definitely um can't be ignored okay next one okay the guidelines also talk about some unacceptable management strategies so in this one we've added uh we've always had a section from day one or back when they were generally unacceptable management strategies but from in 2014 onwards we became bold and said they're unacceptable management strategies so we've always had sea water neutralization so now we've added in groundwater neutralization and that's again sort of after some of the stuff that sort of come across our desks over the last few years about some proposals in urban infill environments we've included another unacceptable management strategy which has a brief discussion on unconfined groundwater dewatering and then we've also included a definition there as well for you okay why are you worried about hastened oxidation oh it's I don't even think it we've ever even seen it it was it was it was a concept that we came up with or that was was talked about back in 2002 um it's basically it was like sort of chucking a whole pile of stuff kind of on a treatment pad but not a treatment pad and just working it and letting it do its thing and like speeding it all up but not really dealing with the managing the acidity part of it the neutralizing part of it wasn't it it was a very good concept it was something that someone came across our desk very early in the original days and we're like no that's not a good idea that's what we've added in there yes that's right it's funny we just we just believe that everyone knows what these terms are these days sorry because we made them up in 2002 what are the consequences to someone like just looking at that last statement about groundwater what are the consequences if their plan doesn't work and they do achieve drawdown is there a stick that you wield on them or well we don't well I wouldn't we don't have sticks to wield the department of environment would certainly be interested I would imagine okay okay uh so yeah for the first time the guidelines talked about trenching which is one of the so we've given some management strategies for trenching so it's interesting Christy and I look back at some of the old presentations that we were doing back in 2002 and we were talking about trenching in presentations but for some reason they never managed it we never managed to make it documented into the guidelines so we've yeah our drawings back then were very very rough but you know we've I don't think we put any drawings in this time for these ones so basically with trenching as as with every ass disturbance and ass investigation is required the guidelines talk about if you can avoid the disturbance of acid sulphates also this could be by keeping your trenches a bit shallower than than those deeper trenches obviously not always possible again it talks about those things to minimize dewatering like excavate in a series of small cells neutralization on a treatment pad and verification testing will be required in some of those lower risk situations there are other management strategies as well so like some sprinkling with neutralization neutralizing agent a guard layer things like that getting them getting this all back in very very quickly so next one please Richard and next one as well yes excellent so you can see this is what we call is probably a relatively low risk trench so you've got some lime sprinkling on the stockpile there was lime underneath that as a guard layer and then when that stockpiles incorporated back in you'll get some you know some good mixing I'm assuming that there's some acid resistant pipes in there as well and other good ways also to throw in some lime along the bed and banks of the trenches as well returning it within time frames like within 20 24 to 48 hours is what we've said in these low risk things and that's when you don't have to take it all off to a treatment pad yeah and then once of course the risk increases once the water table is intercepted as well okay so we'll just sorry what did I say no you're right I say yeah when the water table comes in then everything changes yeah okay so this is what we would call not a low risk trench so this was in a highly sensitive environment ticked all the boxes it's like a great big water treat with a water treatment pipe through the middle of a national park so there were all sorts of approvals that were required by Department of Environment for the environmental licensing and this is Gold Coast City Council did this one and by all counts they did a really really thorough job they minimized they did what they can to minimize you know it was a very confined area they didn't clear a lot they minimized the disturbance of the ground water by using sheet piling they excavated in a series of relatively small cells there was a lot of automatic monitoring and dosing and no doubt I don't know where the discharge waters went but we would have had to comply with some fairly strict requirements from EPA sorry DEZ Department of Environment and Science sorry for those not in Queensland in this instance they they didn't have room to put a treatment pad inside so they trucked they trucked all the marine mugs offsite and built a treatment pad over there on the left that you can see they also opted not to backfill with treated acid sulfate soils so they they backfilled with clean material as well okay next slide please now I'm going to pass back to Chris yeah well so the reuse of treated acid sulfate soils like after you've added lime to them has been in the guideline since day dot but we've just sort of tightened up a few things or made people aware of some of the geotechnical issues basically that they're really not useful for structural field because of that squishiness factor yes and that's a technical term isn't it and also just pointing out that if you're looking at reusing these soils for landscaping purposes they will often require further amendment because they're low in organic matter they'll be high in salts their structure is no good of alkaline pH and they won't have much fertility to talk about so it's certainly a very valid use we've seen it around the place where they've done lime treatment they'll spread it out elsewhere because if you've passed all your verification testing then there is no limits on what you can do with it but it's from the structural point of view that you've got to consider about it so that's just a little bit about the reuse one next slide so now don't show the words yet Richard I got to talk fast so one of the things that we're talking about that has come across our desk of it is this treatment of small volumes of disturbances less than a hundred cubic meters in Queensland we have a state planning policy which triggers when you've got to think about acid sulfate soils and a hundred cubic meters is the mark but we're aware of other jurisdictions I know down in New South Wales they have a trigger of 50 cubic meters and that's really small like this is only sort of minor works usually residential things maybe I don't know putting in a fence or something like this that you're going to generate these small volumes and it doesn't seem practical or economic to say you've got to do a full acid sulfate soil investigation and lab analysis and everything like this for these small volumes of disturbances but if you're in some sort of known acid sulfate soil environment less than five meters elevation and everything like that there is still a possibility that there may be some issues by disturbing even small amounts of soil and you've still to comply with your general environmental duty so we can show the words now Richard so we pulled together all the data from our Queensland government acid sulfate soil database we looked at a subset of about 8 000 samples and we came up with sort of general liming rates depending on soil texture to say if you're doing these small scale disturbances these are all liming rates that you can use and it's based on the 95th percentile so that's implying that one in five is that right yeah one in five will it might not be enough but for the other ones it should be all good and it is only for disturbances less than 100 cubic meter cubic meters and you can't split your volume into smaller cells to try to meet this thing because that's another thing that we have seen before in the past so it's just something that we tightened up and included in there and that is I think it's section in section seven of the guidelines in the neutralization chapter so the next part is that we included Richard is some remediation case studies so we looked at East Trinity which is a big site up in North Queensland where acid sulfate soils were disturbed way back in the 70s and the Queensland government's been remediating it we looked at a case study for the lower lakes in South Australia during the millennium drought like around the Murray Darling basin and the issues associated with that and then there's the remediation of a aquaculture facility in North Queensland has been included in there so that's just got some really cool information about some things that people have done on these sites. Next slide we've included some new stuff about an ASTIP which is just a one pager about dredging operations because the dredging guidelines have come out for acid sulfate soils there's also national dredging guidelines that were already in existence and then there's some sampling guidelines and there wasn't quite consistency about how many sampling locations are required how deep to sample and how many samples to collect and analyze so we chatted with the authors of the dredging guidelines and we came up with this consensus so that just helps to make it clear provide that clarity for people and I think Sue Ellen you might do the next one because it's your favorite part isn't it? So at the Adelaide Acid Soil Conference Christy and I had the pleasure of spending some time with Del Fanning he's a professor from Maryland University I think he's 92 years old so after hearing Del's keynote address where he sang this poem we asked him if we could include it in the guidelines and fortunately he said yes but I'm not going to sing it for you I think it's mandatory if you wish to hum along your hand to the tune of Ebtide as Del did but you can all just you know spend a couple of seconds humming it in your head which we won't do so Del also helped us write a new ass tip on Friends of Fragmites and he even sent us some Friends of Fragmites t-shirts which are jarrosite yellow color they're just lovely and we're supposed to be wearing those whenever we do acid suffix or training road chops but unfortunately Christy and I forgot so next time we guarantee guarantee we'll be wearing them okay you want to move on past the poem or yes thank you okay so there's a few other things that are in the guidelines that we're not going to talk about today but I'll just sort of highlight that they're there so we did some updates to closure reporting which we found out after talking to our industry reference group because we um the closure reporting is used quite quite a lot so we were quite excited about that we also found out that handover testing that was also featured in the 2014 guidelines as far as we can tell was never ever used so we've relegated it back to version four it never made it into version five we do we do talk about it though so if anyone wants to do it they can just go and look at the technique in version four there's quite a bit more on water quality monitoring limnological assessments we had a big section in that because one thing that I didn't mention earlier but strategic there was a whole heap of marine slimes that were generated from a hydraulic separation at the Sunshine Coast they're buried deeply at the bottom of a canal which is like 20 meters of water on them so um they did some limnological assessments back in the day to make sure those sediments wouldn't be disturbed by any winds and and lake turnovers and things like that so as far as we know that's the only time the limnological assessments have been used for acid sulfate soils um so it's still relevant but we put it in the appendix make that chapter a bit smaller we've got some sections on management of surface and groundwater our drain maintenance as well we've got some really cool checklists for ass investigations and em plans that we borrowed from the soil science Australia RSP for acid sulfate soil what are they RSP ass I think that's what it's called so that Christy and Silvana and the team over there wrote so we've we've thrown them in here in here as well they're really good we've got heaps of new ass tips and then lots of other useful information but before you change slide Richard so there is a very real possibility that we will actually release version 5.1 very soon and we've we've noticed a couple of really minor typos like we don't know how they got through but you know we misspelled meter and so we've got to fix that um we also want to have another look at the trenching section we don't think we've got it quite right um it's nearly there um so we just want to make sure that the advice that we're providing on trenching is clear and unambiguous um we're also going to have a another look at our Sally database for that small that table that Christy showed before with the small disturbances because we think we've put peats into the wrong category they you know with four to eight percent sulfur sometimes we put them down there with with sands which generally have much lower levels of um sulfur sulfide so we're just going to have a look in our database and and see if we can see what we need if we need to tweak that particular table um so when we release the next version we'll do our best to spread the word we've got a massive email um database of contacts and acid sulfate soils and we've got all our new friends here today um we'll um publicize it on our website and the department does lots of stuff in social media as well so we think that probably will happen very soon assuming that doesn't take long to get get it out of the department okay so I just wanted to say um before we finished up that this is Christy and I you know friends of Fragmite's t-shirts that Del Fanny sent us um the reason that Christy and I were able to pull off these guidelines by worlds all day was because we spent a lot of time locked in my office for like for you know for more than a few days um Christy bought lots of chocolate um we didn't throw it at each other but we had to have a lot of fun and we had some pretty good video conference calls with our other author Angus here who is not wearing a shirt the friends of Fragmite shirt which is why we had to hold one up for the photo um Angus is a an amazing soil chemist um and he's also good with grammar and and dad jokes but that's all we'd probably need to say yeah but we've got a heap of questions so don't you go anywhere all right so straight into the early bird questions okay are you going to read it or do I just start answering them all right I'm just told them easy boots can biochar help to deacidify soils I read that uh is anyone in Queensland doing this theoretically biochar should but it I mean biochar it's not my field of expertise that's for sure so that's my disclaimer at the start but um it depends I think on the temperature and the combustion that it's burnt at and everything like that as to terms of how much alkalinity is in the substance I know that the crew at Griffith University in Queensland so Professor Chengrong Chen and they're the guys that have been doing lots of research into biochar so I'm going to say talk to those people and they'll be able to answer you much better good why does the guideline refer to the Queensland sampling guide and the link to the national sampling guideline well when we started writing version five we had the intention of also rewriting the sampling guidelines as well um and it's not my intention to write version six of these guidelines so we thought well to be efficient we'll just refer to the Queensland sampling guidelines we'll link to the national guidelines so if we ever do decide to update the sampling guidelines we won't have to rewrite these guidelines so it's purely at the moment in Queensland the national guidelines are effectively the same thing for the Queensland guidelines I mean I can't say that it's high on our priorities to write them so unless Christie's really really keen I'd say that we possibly may never rewrite them but I cannot say never but we also on the Queensland government website we have it really spelt out the differences between the guidelines and how they link in everything like that on the acid sulfate soil part so that probably helps answer that part as well yeah yeah okay number three worked examples case studies would be great to follow up presentations I think you've shown some case studies there so that's all right yeah there's lots of case studies in the literature as well particularly conference literature if people want to look up those yeah I think there's been nine international acid sulfate soil conferences in the last sort of 30 years so they've all got proceedings about them and there's a lot of really cool case studies in those okay number four the new south Wales EPA will not consider material as Venom EMM due to the AA what are your thoughts on this for the EPA we don't really think we know enough enough about even what Venom and Venom and are for us to add I don't think it's appropriate at all for us to comment I don't think all right put that in the too hard basket yeah number five I'm interested in hearing a little more about non-sulfitic acidic soils and better ways to justify these are non-acid sulfate soil well we sort of talk about that in the in the presentation so yeah I think just you know look for evidence of acid sulfate soils like jarosite um Schwertmanite rotten egg gas there's dark stealing colors yeah it's um section 7.6 of the guidelines there's a little pile of dot points to say these are things that if the acidity could be from sulfide oxidation this is what you would see so that might help yeah okay question six what are your thoughts on how the industry is doing when it comes to acid sulfate soil management on contaminated land projects well I'll tackle that one so last night in Brisbane Christy and I spoke at ELGA the Australian Land and Groundwater Association Network and there were lots of contaminated land experts in the room they seem to know what they're doing they were keen to engage with us but it's really it's something our team doesn't get involved in at all so I don't think we can really comment on that at all yeah I guess the one thing I might add is that usually if you have acid sulfate soils and contaminated land on the one side the contaminated land tends to trump your acid sulfate soils management in a lot of cases that that that'll be the priority that they focus on that so and I guess that's the thing is that we have our blinkers on at the moment looking at acid sulfate soil management but as Sue Allen said right at the start it's a really complex thing there's multiple disciplines that all interact with each other and you can't just go in looking with blinkers you've got to consider the whole lot so I think they're doing okay there's a hole yeah I mean it's their job to know both isn't it really yeah definition of acid sulfate soils versus venom containing sulfitic wars yeah that's the venom thing again I I'm sorry but I'm not familiar with the New South Wales legislation about it neither I will need some of the send us some guidance number eight any guidelines or topic regarding construction over acid sulfate soil therefore designing bridging layer X and replace excavate and replace geogrids reinforcement that's an interesting one hmm well I think we sort of we did touch on this a little bit in terms of you know just gotta be careful with acid sulfate soils because you know they can be unsuitable as structural fill for load bearing materials particularly if you neutralize them they continue to react for a long time after treatment they can swell and stuff like that so yeah I'd be getting input from a geotech engineer in all honesty what about in terms of you had that note about capping itself's not a suitable method and that was in in our um so in our first version of the guidelines 2002 we had Steve Dobos who's a um probably got the biggest brain on the planet that I've ever come across you know physicist we only just met I like that Richard that's good and um Steve had done a lot of work in my rehab as a geologist and yeah it was he he who believed strongly that it should be that it you know it was capping is very difficult it's very hard to maintain those impermeable barriers in the long term and um yeah so that's that's why from day one and we had a lot of back then with you know our um hastened oxidation it was another thing that was thrown that was bandied around a lot in those days before we had any management guidelines particularly in the 90s late 90s that you know um because some of the ass consultants had come in from the mining sector back then okay number nine time sensitive options to manage acid sulfate soil versus cost effective alternatives how do they compare in terms of risk and efficacy hmm well these take these soils do take a long time to react and oxidize especially clays and the consequences are pretty high so I don't really know what time sensitive options exist out there um um I sort of think that the risks the risks are likely pretty high but you know don't really know what time sensitive management options there are do you have any ideas Christy no I mean it's an oxidation I know I was gonna say like when we were talking about our trenching examples when it's like a low risk environment and you're above the water table and things like this and you're able to return the soil within a 24 hour period that does negate the need for doing full scale treatment but that's like it's a really site specific you know case by case basis so I'm not yeah I'm not really sure what else to add on that one is it um is it like contaminated land that you can't take it off side to treat or no you can I can only talk about the Queensland experience but you can definitely take uh sort of say raw acid sulfate soils and take them off site to other treatment facilities and things like that yeah you can transport it around the place yeah and they need to be specially licensed for that or just coming it's part of the management plan you'd specify an area and say that's where we're going to do it exactly it's all need to be specified in the management plan yep okay next question practical management of acid sulfate soil well that's the whole talk I think we missed the time before we did sorry number 10 please discuss the differences and similarities between acid rock and or soil with sulfidic ores and acid sulfate soil potential acid sulfate soil I think Christy sort of did touch on this earlier like it's it's effectively the same it's the same chemical it's a pyrite yeah ramboidal so they're small have a large surface here and then they're just highly reactive so there's yeah there's plenty of literature on acid mine drainage um and I think we actually link people to it on page one of the guidelines so I'd go and have a look at those links doesn't it come down a bit to the you know that's the scale of the pyrite mineralisation itself so when you're dealing with mining you've got a pretty massive yes infractures and that sort of thing so yeah absolutely approaching to assist yeah I think the sim the similarity is that the chemistry is the same so that you know of course you remember the chemical equation I put up but it's still the same thing pyrite and oxygen and water you're going to get acid anion being produced that part is the same but the scale of the reactions and how quickly it takes and all that sort of things the kinetics of those reactions are very different in the soils compared to your acid mine drainage sort of situation yeah I suppose the question might be leaning towards given this is now sort of a an official guidance document how does that interface with guidance for you know dealing with acid mine drainage no we wouldn't see that it would be a guidance that you would use for acid mine drainage no they're very different yeah yeah all right question number 12 are there any publicly available case studies demonstrating the effective implementation of the acid sulfates or management framework I think you've answered that one um did you want to add anything to that or are you happy with what you said okay question 13 can you discuss the investigation and monitoring of groundwater when it is unavoidable to dewater trenches and potential acid sulfates well I'd say go and have a look at the western australia guidelines and the national groundwater guidelines because you'd need to do an investigation and then management and then the west the WA guidelines got all sorts of stuff about excellent treatment there's things like minimizing dewatering automatic dosing you can talk to hydroterror about the groundwater monitoring there you go okay nice little things for putting that question in um number 14 what is the longest time period that acid sulfate soil geochemistry has been monitored following disturbance well the main one that comes to my mind would be the east trinity remediation project that the Queensland government's been doing since pretty much since about the year 2000 so it's up trinity inlet which is opposite can cbd it's a 750 hectare tidal wetland site that was bonded and drained in 1970 for sugarcane the sugarcane didn't last very long um and I think they were at its peak they were getting about 3000 tons of acid discharge into trinity inlet every year um some of the there's a really good case study that Michelle Martins from from desi in Queensland wrote for our guidelines so I'd go and have a look at that it's really interesting one of the interesting things that they did discover was that um their jarrosite ultimately dissolved and then the iron reducing bacteria produced by carbonate so I don't think they ever anticipated that there would be such rapid dissolution and weathering of the jarrosite ensuerpment at the site so um nowadays like there there was a lot of organic matter at the site um particularly after they they opened up the floodgates um it was all hydrologically worked out so that there'd be twice daily inundation up to about 0.5 of a meter ahd and um so there's a lot of because the tide was was back in the acidified all the melaleuca then ultimately um perish released a lot of organic matter into the system so I think the organic matter and the seawater were the things that and then hydrated lime as well the things that sort of set that remediation off and yeah it's a really good case study have a have a read in the guideline sorry I just got kicked out because of the internet diet at work but I'm back again welcome back um question 15 last of the early bird questions I think how do you decide which of the three s-pocus suites complete ta or tpa are selected for analysis don't mean to do that one um so back in earlier versions of the guidelines there were different way different lab methods that you could use to analyze acid sulfate soils and there was the spocus sweet the chromium reducible sulfur sweet all sorts of diff things like that we're really seeing a push in the last couple of years that we tend to just use the people just use the chromium reducible sulfur sweet and so chromium reducible sulfur measures your potential acidity titrateable actual acidity test measures the actual acidity part and then you have your net acid soluble sulfur measures your retained acidity and you have acid neutralizing capacity by back titration is your ANC they're the four main tests that we tend to see these days spocus is still used in Queensland it's still an option but it's not really used anywhere else around the place anymore so if you were to submit a sample to the lab to say I want spocus analysis done they'll actually do all those trials that you're talking about there themselves it's there's like a decision tree built into it depending on the pH of the soil so you don't actually choose which ones you get to do um but as I said these days it tends to be more the chromium reducible sulfur analysis they're the ones that are more common they're probably a slightly quicker turnaround and they're a cheaper lab method um so that's why spocus isn't that common these days okay um we'll now move to the are you having to keep going a bit longer guys we've actually got 24 questions in the PLA unless people really want to leave and have a life otherwise there's 158 people listening to you so can this be recorded yes is the answer and it is and you can find it on our website by about Monday or Tuesday of next week so you will get a recording can you please repeat which university is doing the short course for the acid sulfate soil management which was mentioned at the start of the webinar yeah that's southern cross university based out at lismo excellent now there's a question here from alana and gaspari are there plans to update the guidelines to incorporate off-site acid sulfate soil treatment reuse for example stockpiled not at this stage have you had enough soup um for taking stuff off-site um i mean the management principles and your management strategies this are the same whether the stuff's treated on site or elsewhere you've still got to do as per the guidelines and meet that performance criteria and things like that so it's not a different set of rules if it's you know treated here or treated over there and there is a there is an ass tip on the reuse of acid of treated acid sulfate soils yeah i think there was actually in memory i think there was plans years and maybe five ten years ago to do such a guideline um back when we had the around the time some of the national guidelines were being written but we definitely weren't involved in that and and as far as i know it's never it's never happened but might be i think the western australian um acid sulfate soils teams were the ones who were sort of running with that so maybe talk to them if you're um doing a contaminated land project and you excavate soil and you decide to dispose off site the best disposal criteria address that do they um is there overlap there or not or is it sort of not really considered as part of disposal in that sort of scenario i don't know if i ask it perfectly but for these contaminated land practitioners if they're assessing stockpiles for off-site disposal they're off-site disposal criteria then they're into me not really sure but i from speaking to some of the contaminated land people last night they were like two of the consultants were saying that they you know they do it all in the one report like the deals with acid sulfate soils and contaminated lands and other consultants said they do them as two separate things so right yeah but i really don't know we didn't know we have nothing to do with contaminated land it's it's handled by different department okay samoon laboshan if i got that right is guidance available for management and mitigation responsibilities associated with historical acid sulfate soil disturbance each site developed in the 1980s but still operation well it's i'd say the um probably the best reference out there is um niche to allow from new south wales sort of which department wrote some remediation guidelines i don't know if they were in the 90s or early 2000s then um as far as we know other than the remediation case studies that we've published they're probably the only two bits of literature out there on us remediation and i think mitch's stuff was more like broad acre remediation um i don't know if this question is talking about like an existing site that's still being developed or something that's that's a different that's just complicated basically um yeah and there's nothing specific about it no okay next one we've already answered uh yes these are being recorded question from todo bryan following neutralization the guidelines recommend the use of average concentrations if a sample is reported with net acidity greater than zero with an upper limit eg 62 mole for clay however the performance criteria states post neutralization the soil ph is to be greater than 6.5 and the titratable actual acidity is zero can you confirm whether the intention is for averages to be applied to ph and taa as well no you can't you can't average them i think that's my but that's that's a good we'll relook at that and just make sure that this um not ambiguous there but yeah we'll have a double check but it's not meant to average out your ph's and things yeah okay so the answer's no but we'll come back to you we'll check yeah yeah jason do focus and crs which method should be used in general can you please comment on the advantages of and the limitations of each method um yes we can you should talk to a laboratory person though they're far more knowledgeable than us but um generally if you have a highly organic soil um you should stick with the chromium reducible sulfur too that's it doesn't get the interference from the organic sulfur um spocus is kind of like a more complete picture you get a far you get much more analytes and you can sort of you know say what what's you can see a better picture of what's going on as i said earlier they most most at the time these days the chromium reducible sulfur is the preferred one because it's cheaper and a quicker turnaround but yeah i'd talk to your lab person or have a look in depth in the national lab guidelines but then there was also the 2004 Queensland lab guidelines they talk a lot about the differences between both of those methods right next question in the history of acid sulfate soil management neutralization seems to be the most common method and there seems to be a lean toward over neutralization to allow for incomplete mixing coating allowing for highest level of net acidity etc has there been any thought towards sustainability of agricultural lime supply in Queensland regions potential for over treatment in acidophilic environments well that's why there's always that push to do a risk assessment particularly in those acidophilic environments because no one wants to change the composition of those ecosystems but we have certainly not looked at liming supplies in Queensland no but it's it's a very valid point yeah it is absolutely we don't we don't want to line the world that is not what we're intending to do yeah absolutely don't want to line the world that's right you did have been in your discussion about the sort of shell size or the fragment size i can't remember what the size was that 0.5 of a millimeter and that it goes to the lab things get crunched up so it's an ovary it's it's an overestimate of the neutralizing capacity so is there any way the lab can screen out those larger chunks is that what you are yeah like the invisible shell should be removed um they can go through like your different size sieves and things like that like um but most of the lab methods are done on a two mil sieved sample so anything bigger than anything less than two mils will get will go through so it gets a bit tricky i was talking to some lab guys from ALS last night um and they were looking at trying to do different sieving fractions to do that so it's still an involving area but at the moment no i think it's easier to get the shells out of a sandy soil rather than a place or a marine place exactly i reckon um ben perry's got a question hi thank you for the great presentation there you go it is relatively easy to talk about verification laboratory testing for total titratable acidity in the australian context as far as i'm aware there are no laboratories in new zealom that do this test so all tests must be shipped to australia and now we have the fifteen hundred dollar plus gst sterilization fee on top wow everyone know of a lab doing testing in new zealom to speed up this process and reduce costs this potentially makes projects not feasible in the new zealom context yeah no uh no i i mean maybe talk to some of the labs here who are in the nadir accredited scheme and i'm assuming there'd be an equivalent thing in new zealom that they might be aware of but i don't know anyone off the top of my head no it's good to see some samples coming our way rather than going the other way which doxons we used to have to ship to new zealom at a construction site can dewatering alone effectively manage leachate from neutralization without the impervious soil layer i'm not quite sure what that means no i'm a bit confused i think what they're saying is if we're managing the site hydraulically do we really need an impervious layer so they're talking about treatment pads yes it's a bit of both i think um um out the the recommendation is that you do have that compacted base and you have that guard layer underneath because it's to prevent the vertical leachate so yes the vertical movement you know of any leachate and things like that so i would say yeah you've got to stick with it even if you dewatering say effectively capturing that any leachate that's coming through are you a hundred percent sure you're capturing it all i don't know you'd have to monitor it a fair bit yeah that's exactly right yeah i mean i guess that's the other point and thing about the guidelines is that they don't preclude other things happening i mean you can try other techniques you can do other things like that but it just will need a bit more justification pilot trials aren't talking to your regulators and getting their approvals and things like that ahead it's it just because it's something that's not in the guidelines doesn't mean you can never do it that's a good point maren asada body as a question section 7.2.2 of the guidelines allows for some samples to exceed verification testing target for large volumes what is the intention of large in the context of volume that's a good question large is usually over a thousand tons that's what we've kind of stuck with usually like that's what it relates back to the action criteria and things like that anything over a thousand tons you go back down to that 0.03 so i'd say large is a thousand but we'll check that's another one because we did try and sort of get away from all of those sort of vague terms yeah i will definitely have another look at that one okay barra harley what ph endpoint would you recommend for titratable actual acidity the national assets off its all guideline version i have june 2018 says to titrate to an endpoint of 6.5 ph however the lab titrates to an endpoint of 8.3 ph which increases that final to a value do you normally request a 6.5 ph endpoint i would say yes yeah i would go with the national problems yeah talk to um your lab bring up yeah talk to the lab bring up graham langcaster el and ask him he's the one that wrote them he could do that but i'm sure it's to an endpoint of 6.5 yeah okay the next question i think you haven't answered in the chat but alana gaspari are there any lab tests that can be done to determine the source of acidity from soils to distinguish between acid sulfate soil and naturally acidic soils not that i know of not that i know okay anonymous attending is there any guidance included on mg of non-destructive digging and vac truck residue waste treatment no no there's not i've only recently discovered that that's a thing i've got some putting stuff in my place i don't know what they did with my soil it's interesting this whole de-watering thing isn't that that's a big one um justan guru unfortunately i have to leave for a training session but about coffee rock i've heard hw highly vesicular basalt bordering on scoria called coffee rock oh okay that's interesting yeah it's one of those terms that might have been used in a few ways yeah adam fletcher is treated potential acid sulfate soil slash acid sulfate soil classified as wasting Queensland not as far as i know hon vu great talk thank you can you please elaborate um seawater and groundwater neutralization really what if you only got one more question after this well we'd really have to like there's a whole there's a whole section on it in the guideline i have to say go and read the guy can go and have a look at it and read it out no it's all right it sounds like they've addressed it in the guidelines hon yeah you'll need to read them yeah um david metcalf fantastic talk guys thanks so much for presenting this there you go one thing we often encounter in our new south wales lga records woollongong is soils with extremely low ph with very low acid reducibly sulfur if that's the right term given we are asked to investigate by council when we are within 500 meters of potential sulfate soil areas even mapped as low risk of potential acid sulfate soil by our council we often get hits of reducing ph and or low ph in kcl how do we separate these soils which are probably acidic from potential acid sulfate soil um you mentioned it's difficult from lab results alone and how do we differentiate or decide on treatment strategies including if they are actually required yes that's a very tropical tropical question for new south wales from what we gather i know how how can you spoke about that in the previous webinar you did too yeah and i guess what it's coming down to is that these things are getting picked up because of their location like proximity to know you know to acid sulfate soils areas but i mean you're talking about coastal environments and that's where you get a lot of acidic soils too it's where you get highly leached soils and things like that so you're you know iron and aluminium rich soils they'll be acidic as well so it is tricky um as we said we've got that section in the guidelines about these acidic non-sulfitic soils about some little points you can have a look at when it comes to management um we did write a couple of examples to say that perhaps um you know rather than full treatment on a neutralizing neutralization pad and all that sort of stuff it's like lime perimeters around the side or a bit of aglime dusting of stockpiles and things like that but it does come down to that site specific case by case assessment essentially um but we are conscious of not wanting to you know overtreat things if possible okay um we're confused because it's still saying there's 15 questions to go but i haven't got any more in front of me um i think that's oh there they are okay are you happy to keep going team cool get them all over and done with them i think you won't have to have seen lots of written ones Brian McRae why is neutralized acid sulfate soil unsuitable for landfill is this just based on waste avoidance or are there other reasons i think because our landfill sites you know few and far between so we don't want to put something in there unnecessarily okay david saying we've answered most of the question uh back in question five so that's good in any hearse figure why can't you dispose of untreated acid sulfate sort of landfill because you'll just get if it's untreated you're just going to open up a whole can of toxic brew and leachate that can then mix with all the other things that are in a landfill site so not a good idea there are i know there were and still are a couple of sites in Queensland which are licensed to take untreated acid sulfate soils so they are fully you know they're properly lying their groundwater monitored all sorts of things like that so there there are specialist sites which can take it but the last i checked i feel i feel like there was only one left in southeast Queensland that actually did that so there may be more in other areas but there's not many around it's a fair point though right because the landfill is designed to handle okay yes containment facility really yeah that's right um it like yeah it's you can do it it's finding the sites that will take it how many there are and where they can do it yeah okay um not a question just for your information they won't treat potential acid sulfate soil if asbestos has been identified because the mixing may expose and generate fibers so that's from parents interesting yeah um next one we've been asked about the uses of concrete washout material as a replacement for ag lime are there any concerns around the use of this as an alternative i'm assuming that's like crushed concrete is it washout material yeah um there's heaps of other products which have neutralizing potential like you're looking at something with your money in calcium carbonate essentially so there's lots of things out there industry byproducts cement kiln dust red mud all sorts of things which have been used in the past i guess the things to consider is the solubility the pH of those products what else is in there it's often they're not just pure calcium carbonate there's other bits and pieces there and the other thing to work out is that all the things in the guidelines for your liming rates and performance criteria and all that all based on ag lime so you're going to have to readjust them all and it might be necessary back to the pilot trials and talking to regulators and things like that but it's possible yes so Ellen do you want to add anything no sorry all right hopefully you're not getting that noise in the background Brett Thomas with respect to question seven as you have said virgin natural virgin material oh that is that is it venom that he's talking about ah okay is defined as a natural material that does not contain any sulphuric or sulphuric soils or any other sulphuric rock or waste soil with any form of or source of sulphides would classify as acid sulphate soil contaminated soil rock is covered by acid mine drainage management requirements chemistry is the same the reaction rates a and c sources trigger values and risk acceptance criteria based on disturbance will differ thanks for that Brett Thomas Cole and a hand Cole there's Cole a hand can make a general comment acid sulphate soil and mining oh okay okay thanks Cole Michael Melz has the maximum timeline for strategic reburial been updated excavation to reburial fine I don't think so and I think it's changed it's still what it was before yeah okay next question Inge Hursinger Tam and can Tam and acid sulphate soil should be dealt with concurrently management measures apply to both and you need to deal with it together you can't ignore the acid sulphates or just because it can turn and edit yep good call um nav jot car this we can see that question here we go with acid sulphate soil management for the trenches section said to do minor treatment before backfilling but do we have any options for the backfilling within 24 hours without treating in accordance with table five stockpile options untreated acid sulphate soil on prediquary and raised by a client it's a good point yeah um that's the issue that we are having a much closer look at um I think if you look at the stockpiling tables there's still requirements for dusting of the stockpiles and a guard layer as well so we yeah it is it is we agree it's a little bit ambiguous so that's that will be version 5.1 addressing that particular issue and the thing too with the stockpiling section that's if you're doing lime treatment and for some reason you you can't get the results back from the lab quick enough or whatever like that and you've got an excess of soil that you've got to move off a treatment pad um and before the next slot comes in that's what that stockpiling is for so it's not like just stockpiling for the heck of it so yeah that it was a bit there is a bit of a mixed message there yes okay in the herciga I would use as focus only in a marine setting where you anticipate lots of shells it gives you an interesting breakdown of calcium magnesium concentrations which helps to support the shell neutralization story if you don't see shells but get a lot of calcium and ANC then this can support your argument that tiny shells are present yep totally agree with that that's what this focus gives you uh more analytes to look at so you can get a bigger picture of what's going on Mayor Han Asada Badi thanks Kristi and Sue Ellen and Richard of course and more thanks there Mark Downey guidance neutralizing rates for small disturbances less than 100 cubic meters are they Queensland specific or could they be extrapolated elsewhere well they're based on Queensland data um like I I'm sure that other government agencies who've had an active assets office or mapping program probably also have a heap of data in their databases that they could analyze but um I don't really see any reason why you wouldn't couldn't use them elsewhere maybe maybe a little bit hesitant about WA because of those you know because of the sands sands over there um but other than that and there there's those sands over there are really poorly buffered so a bit yeah a bit risk a bit of course is that using them in WA but I think other than that yeah I mean we you get variable sulfide results all over the place we thought we had the record in Queensland of 16.6 s but I found out just recently that Tasmania has results above 20 s I was like what we lost our record well I think you've got close to the record of the number of participants in a webinar um I really want to thank you both for presenting today it's been fantastic and uh you know it's been great to have such a big audience to hear I guess it's a real lesson in persistence this uh this manual and you know thanks very much for putting such a guide and document together and sticking at it because there's a lot of good practical information there for everybody so many thanks to you both and um look if anyone has further questions shoot shoot email through and we'll um communicate I think can I add one last thing is that yeah we you know we've wrote spent a lot of time doing these guidelines but it's certainly been a very big collaborative effort and if you look at that industry reference group there's close to 50 people that have had input into it and you know gave a lot of their time to make this a practical document so yeah team effort man yeah yeah and then you know if you think about you know from 2000 there's probably you know 70 or 80 people who industry experts who've contributed so yeah I think that's just led to the success of the document why it is such a practical document because we've had such big input from industry yeah and academics well there you go thanks to everyone and thanks very much for joining us today thank you see you thank you all right bye


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