Thanks David, morning every one, I’m here to talk to you today about the unsexy side of landfill operations;
I think landfill gas management and leachate management take up an awful lot of our time
and rightly so, they are very important issues.
But cover management practices at landfills I think is an area which is often overlooked by operators
in terms of the effects that that can have in achieving a good performance of landfill sites.
So I’m going to talk about cover at landfills in a kind of a general sense.
I’m going to spend most of my time talking about daily cover
but I’m also going to spend a little bit of time talking about intermediate cover, temporary capping and final capping
which are all types of cover systems in place at landfills.
I’m not sure if you can see that very clearly, but typical landfill scene in Ireland,
we have the compactor on the right hand side there working on the current face of the landfill.
We have a variety of different cover practices in place; we have hessian in use,
we have some compost up the back there as well, in the foreground down to the left
we have some older waste deposits and that is effectively intermediate cover
and you can see that the level of cover attained there is a little bit on the patchy side.
So in terms of issues with cover management practices at Irish sites, there are still problems occurring today.
We have inadequate coverage of waste deposits, inadequate depth of material placed out on the waste,
materials used which aren’t really suitable for controlling odours
and I’ll talk a bit about odours in a while.
Flanked areas has been shown up as a major source of fugitive emissions at landfills
and cover practises in those areas I think is fair to say are generally, generally speaking, not very good.
The characterisation and the consistency of the materials is also an issue and I’ll talk a bit about that again.
Inappropriate materials used for prolonged periods of time.
So we find that materials which might be good for litter control are left exposed on waste bodies for months at a time
and you find that the material has given rise to flies or odours etcetera so they are not suitable in the long term
and damage to covering systems, either from vehicles or erosion.
These are typical problems that we see.
So just to illustrate some of those points, here’s a site now with some cover applied over quite a wide area.
This is effectively intermediate cover, a compost material, the material is spread quite thin
and you can see that it’s actually been washed off over a period of time.
So you are left with large expanses of litter and waste popping through the cover material.
This is an issue which is going to come more and more to the fore now in the coming years
with the new conditions in landfills for bio-waste diversion.
But some sites have been using stabilised organic fines or stabilised biowaste as landfill cover.
I think our experience would be that most of this material to date has not been properly stabilised
It is only partially stabilised and while it may look very attractive on the surface,
you dig underneath it you find mycelia fungal growth in the material,
it’s still actively degrading, it’s giving off heat, it’s giving off steam and, potentially, giving off odours as well.
So there’s a need to improve the quality of these types of materials.
And then you get this sort of scenario where you arrive on-site and you see something out on the waste
and you think “jeepers what the flip is that?” and there’s all kinds of everything in it
and you’re not really sure what is it, what purpose is it actually serving?
Should this waste actually be disposed of and covered over with something else?
I think there has been a tendency for some licensees maybe to overlook the quality
and the type of cover materials that they are using and they think,
"Ah I’ll just get this in for free, it’s fine it’ll do the job”.
But there needs to be closer attention paid to the materials that sites are actually using and how effective they are.
Now I mentioned odours. I’m sure all of us are aware that odours is probably the biggest issue
currently faced by landfill licences at the moment.
There’s a diagram there to show the number of complaints that we’ve been receiving over the last few years
and you can see the maroon colour on the bottom shows the number that are actually odour complaints for waste sites
so it’s a huge percentage of the number of complaints that we get in.
If you look behind those figures you know maybe 50%, in relation to landfills,
maybe up to 50% of those odour complaints are actually related to a fresh waste smell, not landfill gas.
That’s interesting because if you are covering the waste properly and if the cover was effective
we should see much, much less figures for fresh waste, it should really only be dealing with landfill gas fugitive emissions.
The studies by Odour Monitoring Ireland, in terms of surveying the fugitive emissions at landfills,
they have shown significant fugitive emissions from areas that have been covered
whether it be daily cover, intermediate cover or indeed final capping.
Now I’ve throw up the definition there of cover materials that are currently reflected in landfill licences
and basically the nub of it is: it’s inert material unless it’s otherwise agreed with the Agency
so if you are using something else it should get our agreement.
Now I’ll talk about daily cover. My interpretation of what daily cover is: it’s a temporary barrier,
it’s a temporary buffer system so it’s something that you’re going to have in place
to try and control the emissions from the site during the operational stage of the cell.
So it’s not designed to control everything but what it is there for is to try and minimise those effects
during the operational cycle of the cell.
And when you really boil it down the main function of daily cover is to control nuisances so that should be foremost in your mind.
“Am I controlling the nuisances at the site?” And if the answer is “no”,
you should really be looking at what cover materials you are using and what practices you are using?
So the daily cover should be getting on top of things like odours in particular,
but also litter, dust, flies, rodents and birds.
But daily cover also has some other benefits as an aside,
it can change the nature of the gas emissions coming off from deposited waste,
so you get a biofilter type operation there where you get VOC oxidation, that‘s a benefit.
It will improve, and should improve, fire control at a site and
gas management in terms of minimising oxygen ingress into the waste body.
It will play some role in terms of reducing leachate generation but I think that’s not to be overstated
and again it will minimise visual intrusion and help deal with trackability issues for vehicles etcetera.
So in terms of good practices, you know there are some good practices illustrated by this picture
we see a small tight working face, which makes it easier to cover at the end of the day.
They’re depositing the waste on yesterday’s waste which you can see has been well covered with hessian,
you can see that there’s a stockpile of cover material at close range, so it’s easy and quickly able to be spread out.
In the background you see some intermediate cover and
there’s no waste popping through the intermediate cover, the cover is in good condition.
It doesn’t get a clean bill of health of course because the flank areas,
in terms of covering those over now for the next day and a week on,
that’s going to be a bit tricky now because you’re now getting into
the realms of trying to drop cover materials over from the top.
Now there are some things which daily cover shouldn’t do;
it shouldn’t give rise to odours itself,
so if you are taking in something that’s inherently smelly it shouldn’t be used.
It shouldn’t give rise to nuisances,
if you find that the material is very dusty for example and you are getting dust complaints,
you really need to look at the cover material you are using.
It shouldn’t cause pollution. That’s really more an aspect of how you use the material
and where you store it in terms of, for example the quality of surface water runoff.
It shouldn’t breach your licence so it should be in accordance with conditions in terms of waste acceptance.
It shouldn’t degrade over time to give rise to secondary problems.
It shouldn’t impede the proper functioning of your gas and your leachate management systems and
traditionally the daily cover material should be free draining material
so you don’t want it to impede your collection of gas or leachate
and it shouldn’t be a feedstock for future landfill gas generation at the site.
So traditionally about 150mm of soil was used as daily cover in Ireland
and the quality that you are looking for is, really you want it to be free draining.
There are quite a variety of other alternative cover systems in use in Ireland at the moment.
I put a slide up there for some of the examples that currently are in use;
hessian is quite popular, stabilised biowaste, geosynthetic materials and woodchip for example.
You know from a landfill operator’s perspective, there’s a multitude of aspects that they need to consider,
and do consider, in terms of what cover materials are used, the cost,
the loss of revenue in terms of void space, what’s available locally?
Some sites would probably love to use soil but they can’t because they can’t get their hands on it.
How easy is it to use at your particular facility based on the design of the site and maybe it’s location?
So is it exposed to very high winds for example?
And I put up there distance and sensitivity of nearest receptors.
If you have sensitive receptors which are very close to you
odour is going to be a major major issue for you so you might want to use a cover material
which is particularly good at controlling odours rather than some of the other nuisance aspects.
How consistent, how good is the quality of the material you are getting in?
That’s something that should be considered and
what are the main issues faced by your particular site?
So if you have a big problem with birds, is the cover material that you are using,
is that effective in trying to deal with the bird situation for example?
And you need to take account of, it’s a site specific aspect, for a particular design of a site,
say for example if we had a site which had steep lined sides,
it might be very difficult to use particular cover techniques in those sorts of scenarios
so you need to take account of that and amend things accordingly.
Now as I said earlier this is an issue which is going to be coming more and more important going into the future;
this whole issue of stability and diversion of biowaste away from landfills.
And I put in red at the bottom there the wording of the new licensing condition which is going into landfill licences.
And basically it requires that the material, if you are using a stabilised biowaste or a compost-like output,
it should be properly stabilised and that means that it has a low respiration activity
of less than 10mg of oxygen per gram of dry matter.
It should also meet the Department of Agricultures’ animal by-products sanitisation requirements.
I think most people will be familiar with what’s involved there
and for those alternative systems, as I said earlier, they need to be agreed with the Agency.
Now I’ve talked about cover materials.
It’s also worth bearing in mind that how you put out those cover materials is also important.
The application techniques that you are using at a site,
they should make sure that you are able to deal with flank areas, that you are able to get those covered.
Ideally the cover methodologies that you use, they should be quick and easy to do.
You shouldn’t have an hour put aside at the end of the day to put out your cover,
it should be relatively quick and easy to do if you are doing it right.
And it should be able to cope with changes in environmental conditions -
if it’s going to be very windy or whatever, if you are using a roll out cover material from your compactor
you’re going to be in difficulty, you might need to have an alternative technique available to you.
Your application technique shouldn’t give rise to nuisance
so you don’t want to be throwing out a dusty material through the air to cover the waste
that is going to give rise to dust blow.
It shouldn’t compromise the stability of your waste like a sludge type material,
if you find that’s having issues with stability you know you need to stop using it.
Ideally your vehicles on-site, they shouldn’t be traversing over previously covered areas.
In terms of what is best practice? Only use suitable cover materials for each site
and ensure that the application practices again are suitable for your site.
Be aware of the limitations of the cover materials and the application techniques that you are using
so you can plan for a backup system, if you like.
You should avoid vehicles tracking over areas which have been covered over
so that you prevent the waste from coming back up.
Have a stockpile of material on-site and have a backup available on site.
I think it’s good practice to use a combination of methods so that you have one thing which complements the other
and you should store the materials appropriately.
So for example, if you have a material that could give rise to a high BOD load in surface water,
you need to make sure that that material is stored within the lined cell, not outside the cell.
And you should have some storage of inert cover material available on site
just in case there is a fire, you don’t want to be putting something biodegradable out on top of it.
And in terms of flank areas, I think pre-constructing clay berms is a very very good technique
and I’ll talk a bit about that now in a minute.
If you are using compost-like outputs,
make sure they are properly stabilised and they comply with animal by-product requirements
and if you are dealing with something like that that is of a variable nature and there could be issues over it
whether it be the level of some sort of contamination or level of stabilisation,
licensees should be looking closely at the quality of the material that is coming in
to make sure it still meets the specification that you expect it to.
And in terms of cover management practices,
I don’t think a lot of sites would actually have documented procedures
but it would be good practice to have procedures so that it is actually thought out in advance
and that you know what you normally do and what you do in an event of something unusual happening
and those could be included in the Landfill Environmental Management Programme
or maybe in your Odour Management Plan.
And a simple thing like minimise the size of your working face
so if you’ve got a smaller working face, it means you have less cover to put out,
it’s quicker, easier to do, so again good practice.
And just the last point there, you need to regularly assess the performance of your cover management practices
not just assume everything is okay because you are using clay or whatever.
You need to actually critically evaluate it.
Now I’m going to talk a little bit about haul roads.
Typically C&D material or broken stone or whatever is used as a haul road
and it goes right up into the heart of the waste body and
in some sites it can represent a significant surface area across the waste body.
These are potential, massive source areas of fugitive emissions from the waste body.
So you need to consider how effective that area is in terms of controlling odours and gas emissions from the site in general.
I think good practice going forward is that
if you ‘re going to have a significant haul road there for any length of time,
it should probably be underlaid by a gas barrier membrane
to try to minimise those fugitive gas emissions.
Now I mentioned flank areas as one of our typical problems.
A photograph here of I’d say a poorly covered flank area -
they’ve used hessian which was probably out for a couple of months.
You can see that the material is degrading, there’s no odour control there at all effectively.
There’s waste protruding, the lines of the hessian are not overlapping anymore, it’s a bit of a disaster.
So what is a good way to control your flank areas?
Well one of the better management practices is to use pre-constructed clay berms,
I’ve done a quick illustration there of say three lifts of waste, and before you actually move in,
you construct a clay berm to mark out the edge of where your lift is going to be.
And that means that your cover is already in place on day one, on the side slopes
and it also means that you have something firm you can actually compact up against
so it’s good for the compactor drivers as well.
And when you come to the next lift, you then construct another clay berm, just step it in a little bit in from the previous one,
so when you look on the outside edge, you’re looking at a clean face of clay.
There should be no waste protruding through it and there should be minimum escape of gas and leachate.
So this is a photo of how it might look. You can see it’s a very very clean environment.
In this example now those clay berms are benched, so they are stepped back from each other,
but you could also construct them nearly on top of each other so that you have a smooth side slope there.
This is an example of how things can go horribly wrong on side slopes -
where does the waste stop and the environment begin?
There’s poor delineation there of where the waste is, where the cover is and where it stops.
Like you can see the anchor trench for the liner just on the bottom foreground of the picture and
in terms of leachate management even alone it’s a bit of a nightmare
because if you get a leachate breakout is it skiting off past the liner?
How do you get it back into the waste body etcetera?
So when you want to construct your lifts going above the top of the lined cell,
it’s probably good practice to leave just a little bit of a gap at the side so that you know exactly where the waste finishes
and if you do get any leachate breakouts,
there is a pathway for it to get back down into the leachate collection layer at the bottom.
Now you do have to be careful about odour emissions from that side slope.
So something which you can do is that you can also augment that system,
probably once it gets up to a critical stage, by putting in an LLDPE layer or a gas barrier layer etcetera on that side slope
and that has the added benefit of keeping clean rainwater from getting into the waste at all.
So the clean rainwater is shed off to the side into a drainage system
and that has the benefits of improving leachate generation rates from that cell.
It’s important if you are using that type of a system that it’s properly anchored at the top
and again there’s good delineation between the contaminated water on the left hand side there,
that that’s kept within the cell whereas clean rainwater is separated by that little clay berm and that’s shed off to the right.
Now in terms of intermediate cover,
it’s important to remember that when you cover waste at the end of the day
at some point, daily cover has to end and intermediate cover needs to kick in.
And intermediate cover is really to deal with waste which is going to be left alone for a period of time
an extended period of time. And what is an extended period of time?
Well if your daily cover has been in place for seven days and your not going back into that area
that’s when you should have that area covered with intermediate cover.
Whereas traditionally, 150mm of soil was used as daily cover,
intermediate cover you’re basically just beefing that up a bit, so you are maybe doubling it to around to 300mm
In this scenario you want to have more control over gas emissions,
rainfall infiltration into the waste body, and it needs to be robust over a period of time.
So it is in effect a semi-impermeable barrier rather than the daily cover which is much more permeable.
Now temporary capping, this was a relatively new concept to me up until quite recently.
Some sites are incorporating this as another step between intermediate cover
and your final cover when you walk away from the cell.
The beauty of this is that it has better control over gas and leachate
without going to the full expense of a final cover
and you allow the waste body to go through that intense settlement period before you put your final cap in place.
So over and above your intermediate cover, the extra benefit you’re getting is
you are dramatically reducing the infiltration of rainwater;
you might have it seeded if you’re using a clay material so that improves water shed off,
improves the visual appearance of it and you obliviously need to keep an eye on it in terms of erosion.
So whereas soil might have been used in the past say a half metre to one metre
I think sites are more moving towards a rollout of a gas barrier membrane,
and just use that alone and that’ll achieve the same effect.
Finally final capping;
Final capping is a permanent barrier, so this is looking at the long term control of things like
gas emissions and leachate generation and leachate management within the cell.
So it needs to be good, okay, because it’s not like you’ll want to go back and top it up or repair it or whatever.
You should be constructing your final capping in accordance with your licence.
It needs to be properly designed, and
really what I’m talking about there is the attention to those small details of
where the capping comes down to meet other infrastructure like the side slope liner,
adjoining adjacent cells, the finishing details around manholes, wells, that kind of thing.
You can get so many problems if you don’t look at the detailed design of around those structures.
And it needs to be properly supervised,
I think we lose a lot of sleep worrying about the construction of the basal liner for a cell
and there’s very little attention paid to the final capping but it’s actually also very very important
and it needs to go through CQA testing as well as the basal liner.
The Odour Monitoring Ireland leakage surveys that are being done on Irish sites,
they’re identifying quite a number of anomalies where there’s significant gas emissions coming from final capped areas
which is bizarre, particularly around wellheads.
There should be no leaks around those wellheads.
And we’ve had other scenarios where final capping has been done on a cell
and the licensee is scratching their head going “You know we are still getting very high leachate levels.
Where’s the leachate coming from? Where’s the rainwater coming from?”
And they’ve had to go back in, dig up, do trial holes on a final capped area
and find that the layers weren’t overlapped properly or they weren’t sealed properly
and the rainwater is just percolating in through the final cap.
I think most people will be familiar with EPA’s landfill manuals in terms of information on capping and cover materials.
There’s also a recent report done by Odour Monitoring Ireland, done for the EPA,
looking at critical analysis of cover systems in Ireland so I think that will be available to you shortly.
The one good thing I suppose in particular about that report is that it looks through
all the various alternative cover materials in use in Ireland and gives you pros and cons of each one.
So it gives you more information to critically evaluate, “Right if we use that, it’s weak on fly control or something,
what are we going to do to make sure we deal with that aspect as well?
So in summary; present landfill cover practices -
they’re often inadequate at controlling all of the nuisances at a landfill site in Ireland.
And there needs to be greater focus on odour control;
odour is our biggest issue at the moment and cover needs to deal with that.
Covering of flank areas; that’s another major weakness at the moment.
I think licensees should have their own site specific cover management strategy in place
so that they’ve thought about what they are going to use, how they are going to use it,
what happens if it’s not working? What do they revert back to?
And those procedures should be documented and you regularly assess them.
It can be summed up in one motto I suppose, “Appropriate cover for appropriate use”.
So you use the right materials but you use them in the right way for what they are actually intended for.
If we get cover management practices right, who knows, maybe we’ll all be growing pumpkins on the side of a landfill one day.
Thanks very much.
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Caoimhin Nolan, Inspector, OEE, EPA
Cover at landfills