LTR - Ep 50 - Best Practices for Field Soil Sampling

In this 50th episode, I discuss some "Best Practices for Field Soil Sampling."

One of the most important considerations is to remember that Soil Contamination, is not always sitting on the surface as horizontal contamination.  The longer the contamination is in soil, the more gravity begins to work on it, causing migration or the traveling of the contamination vertically.

Another important consideration, is the size of the area of concern, whereby, the larger the area, the more samples need to be taken, to get a good coverage of the area, to have a better understanding of not only the defined are of concern, but to also, identify the "hotspots," where the concentrations are highest.  By doing this up front, it allows for more of the focus to be on the areas of concern, rather than either focusing on the entire area including lower levels as well as, not missing the higher areas, by them being diluted out by the lower level areas.

By doing a good job up front on the delineation; defining of the contaminated areas and identifying the hotspots, will put the focus where it should be, which will help in the economics of the project, saving both time and money.

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Transcript

SPEAKER_02 0:02

Thanks for tuning in to our podcast. We love having you here, and it's our mission to bring you all the latest and greatest tips, skills, and know-how to make you the best that you can be. We know that you have an idiot and we're going to show you how. Now, now let's get started.

SPEAKER_00 0:26

Hey there, let's talk remediation. This is your host, Charles Fader, and this is our 50th episode. Our 50th episode is brought to us by our ongoing sponsor, Hanby Environmental. Hanbe Environmental is a manufacturer of field test kits for water, soil, and solid surface analysis, uh, providing accurate results within 10% of a lab results, uh, economical results at$35 a test for soil and solid surface and$45 a test for water, and efficient uh four minutes for soil and solid surface and six minutes for water analysis for petroleum hydrocarbons. Hambi Environmental has recently uh released a new field test kit for chlorides, uh, and it the same test kit is used to analyze uh both soil and water samples for chloride levels. And so that's the latest uh release from Hambi Environmental. Hambi Environmental, thank you for your ongoing support of this podcast, Let's Talk Remediation, where we are trying to have a positive impact on the environmental remediation industry. And with that, let's get started with our 50th episode. Our 50th episode builds upon our last 49th episode. In our 49th episode, we were talking about the fundamentals of field uh analysis or field measurements. And here in our 50th episode, our topic is going to be best practices for soil sampling. And with that, uh, in when you're needing to do uh field sampling or uh field sampling for contaminated soil, um you know, some of the best practices out there in the industry are to do what's called delineation. And delineation means defining your boundaries, okay? The defining the area where the contamination is or the spill site or the area that needs to be remediated. So you need to delineate. And when you delineate or define that contamination area, it is both horizontal, which is surface contamination, and vertical. You people need to remember that uh the longer contamination sits, uh, the more likely it is that it has uh migrated not only on the surface verti, I mean horizontally right and left, but also it has begun to have gravity work on it and has begun to s uh sink beneath the surface. So important to always remember when delineating or defining the boundaries of the contaminated area that it's not just uh horizontal or surface contamination, it also begins to migrate and travel uh vertically. So depth is also important. So now when you're soil sampling, this could also be applicable to water sampling, but when you're soil sampling in particular, um one of the best practices is to use a grid. Think of the area uh as a grid. Uh and when when you're thinking of a grid, you're thinking about squares, right? Uh whether you're talking about a small area where you're talking about just like maybe one square, or a large area where you're starting to think about multiple squares attached to each other, right? And again, don't forget that this also uh needs to be thought of as a vertical uh as well. So, but just thinking um two-dimensional right now on the surface, surface contamination, you think about this grid area. Let's talk about a small contaminated area where you've got a single square grid. Um, you need to be thinking about how do we determine uh the contaminated area, right? And how much contamination is in this area. Well, the best way to do that is to think of your sampling technique as if you got a single square, probably a good coverage of that square is to uh either take one from each side, or the easier way to think about it is one in each corner versus a side, uh, and then uh one in the middle. So if you take the four corners, you take a sample in each of the four quarter corners, and you take a sample from the middle, those five samples give you a good coverage of that uh that one square area. Now, that's at the surface. Let's just not forget that the longer that contamination has been there, it has migrated and gravity has worked on it and pulled that contamination down. So then we need to start thinking about depth as well, other as just the surface area. So depth now, you need to be thinking about the type of soil in the area, whether it's sandy or whether it's clay, and that will, and the longer it's been there, the contaminated area uh would have had gravity work on it. Um so we need to be thinking about the different depth levels as well that we need to go down to in taking our samples, uh, not just at the surface, but also at depths of say, you know, three to four inches to six inches to a foot to you know a couple of feet. It all just depends, right? So you got to look at lots of different factors to determine, you know, the vertical area that needs to be um uh uh analyzed. So, and of course, the larger the area, uh the further you need to be thinking about um going out and doing more sampling. So the four corners in the middle of just a square area, if it's a large square area, now you need to be thinking about that as being like instead of one square, maybe thinking about it as nine squares, a three by three square there, where now you're taking not just you know five samples where it would be the four corners in the middle, but maybe the four corners in the middle of each of those nine squares that create that grid there. So in that case, you know, you're doing a lot more sampling uh to cover that area. Now, don't forget that the vertical comes into play. Now, as you start to remediate, however you're doing it, whether you're treating it or you're digging it, that type of thing, you want to know that those same areas need to be resampled, right? So uh your initial sampling, you want to have it like flagged off, right? And then you want to, as you're remediating, you want to re-sample and reanalyze in those same locations to monitor the progress of the remediation work being done. And again, this happens not just horizontal on the surface, but vertically as well, and you do that by using different tools to augers or trows to uh you know be able to s uh sample beneath this, I mean you can even use a you know a shovel if you will, if you need to, but beneath just the surface, right? And uh that's just a thought process to really have great coverage for um you know knowing where the contamination lies in an area. And rather than doing what's called a composite sample where you go and do grab samples from lots of different locations and pull them together, uh like 10 or 15 different uh uh small samples and pull them together in a bucket and mixing them up and then taking one sample from it, you know, that what you're doing when you do that, you're actually dil you if you have one hot out of let's say you took 15 samples and threw them all in a bucket and mix it all up and then you took it. You have one hot sample in there and you have no idea where it's at and it was diluted out eek by the other 14 samples uh to make it look like there's no there's no contamination. So you know when you do that composite type sample, uh I understand it's a large area that you're looking at, but you know, you may miss something that way. So it's better to initially get a good understanding by having the the most samples in those different locations. Now, as you get to remediating, now you can start to do those composite samples where um okay, well, we're not quite there yet, so you can do that, right? And then once you've monitored your remediation work down to where you think that you know uh you've got down to where you need to be, then you can re uh sample in all the locations again that you initially started at instead of doing the composite sampling again. Now, the reason for that is because think about that little bit larger area where you have the um nine uh square grid. And let's say that just one of those nine squares has a hot spot in it. Well, you know, now we've been able to really identify where that hotspot is if you've sampled properly. However, if you've gone and done composite samples from all those different nine uh squares in that grid, you may not even know that hot spot exists. Okay? And the problem with that is you can't address it at that point. Now, later, that hotspot still remains because you didn't know it existed and it migrates and travels and contaminates the rest of the area after the fact. Or that hotspot may be where somebody goes behind you like a regulatory agency and samples and finds that hotspot, and they're gonna now consider the entire thing as being contaminated because they got that one hotspot. Now, if you'll just do the sampling up front to really identify where that hotspot area is, you can now focus on that hotspot area and actually know because you did your great job sampling up front, that those other eight of nine uh squares in the in the nine square grid actually are clean. So you can now not worry about those and only focus on that one square, that one out of nine square in the grid in that particular area. So doing uh you know, a good job of field sampling up front will actually help you uh in a long run in a in a very big area because you've identified the area of concern with the highest contamination level, and you're not wasting your time treating the entire area or remediating the entire area because the assumption is uh that the entire area is still contaminated. You've been able to eliminate those other eight out of nine because you did the good sampling up front and you identified that one particular area that needs to be of concern to you rather than the entire area. So that's why uh I suggest that the best practice for fueled sampling is to do the uh up front, do the most sampling to get that good understanding. And then from there, after you've really identified the areas or spots of concern, um, then you can uh be a little bit more relaxed in in your uh number of samples taken because you've kind of already got an idea that those other areas are are not of concern, and then um at the end you can uh r re-sample all the the areas to to know that you've got it all and have that validation and documentation there. So that's just what I wanted to talk today about is the best practices for field sampling is to make sure you've got good coverage of the area. And the larger the area, the more sampling needs to be performed such that you can eliminate areas that are not of concern and you can identify the areas that are of concern. By doing that, you will focus where you need to focus and not miss that area by having it be diluted out by the other clean areas so that you miss that hot spot area. And you're not wasting your time on the entire area because you've actually identified the hotspot area or hot spots area of concern. So doing a little bit more sampling up front to get that good understanding of where you need to be focused will really do wonders for your your uh remediation project. So, with that, I thank you for tuning in. I just wanted to build upon that last episode of um uh the fundamentals of field uh measurements with this uh topic for today, which was the best practices for uh soil sampling. Uh thank you, Hambi Environmental, for your ongoing support of this podcast, Let's Talk Remediation, where we're trying to have a positive impact on the environmental remediation industry. Thank you for tuning into this podcast. Uh, and as I always say in the past, if you have a topic you'd like for us to cover on a future podcast, don't hesitate to drop me a line. Uh my email address is C Fader, that's C Frank A-T-O-R at let's talkremediation.com. Just shoot me an email, let me know what uh topic you'd like for us to cover or a specific question you'd like for us to address, and we'll get that on a future podcast. And with that, I'm your host, Charles Fader, and I'm out. Thank you.

SPEAKER_01 14:48

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