LTR - Ep 55 - Soil Remediation Sampling - Grab vs. Composite

In this 55th episode, I discuss Soil Remediation Sampling - Grab vs. Composite.

When Soil Remediation is being performed, Soil Sampling is needed to monitor and document the remediation and it's effectiveness.

In performing soil sampling, there are two types of samples; Grab and Composite.

Grab samples are samples taken a very specific location.

Composite samples are a collection of multiple grab samples mixed together.

My suggestion is always to perform grab samples to define the area that needs to be remediated.  And then, as remediation progresses, then re-grab sample at those sample locations, to be able to see the difference and effectiveness of the remediation work.

Composite sampling creates an opportunity for contamination levels to be overlooked by being averaged out with non-contaminated soil.  On the contrary, Grab sampling allows for the identification of any locations that need additional attention and eliminate those that do not.  The thought is Composite sampling is a more economical approach, but I'd suggest that if you have an economical means of analyzing Grab samples, like Hanby Field Test Kits, then Grab samples provide better information, as it's location specific.

Also, a combination of both types could be used, by using Grab to Start and End and using Composite in between, when a large area is being remediated and the entire area is being treated the same.

"Thank You" for tuning in and to Our Ongoing Sponsor Hanby Environmental for the continued support of our podcast having a positive impact on The Environmental Remediation Industry!

Send in any future podcast topics or questions to CFator@LetsTalkRemediation.com and follow us on FaceBook, Linkedin and X.

If you are not following this podcast and are in the Remediation Space, "You SHOULD Be!"

Also, if you are in The Remediation Industry and are interested in telling your story, we are looking for Experts to interview for future podcast episodes.

Transcript

SPEAKER_00 0:11

Skills and know how to make you the best that you can be.

SPEAKER_01 0:29

Hey there, let's talk remediation. This is your host, Charles Fader, and this is our 55th episode of Let's Talk Remediation. Our 55th episode is brought to us by our ongoing sponsor, Hambi Environmental. Hambi Environmental is a manufacturer of field test kits for analyzing soil, solid surface, and water for petroleum hydrocarbons, for PFAS and PFOS, and for chloride uh detection levels. So thank you, Hambi Environmental, 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. Our 55th episode is going to be about soil remediation sampling. And the specific part to soil remediation sampling that I wanted to go over today is the difference between the two types of samples of called a grab sample and a composite sample. So when doing soil remediation, obviously, you need to do sampling. Sampling helps you to know contamination levels. And so there are two types of samples. There's a grab sample and a composite sample. So a grab sample you you pull soil from a specific location, and it it gives you a precise uh opportunity to determine a concentration level for a type of contaminant in a specific location, an exact location. Now, a composite sample is a mixture of multiple grab samples from different locations. So comparing or the the two different types, a grab sample is a single uh sample from a specific location, and a composite sample again is a collection of multiple grab samples. And so, you know, if if you're going to need to identify uh hot spot locations or uh delineate, which means to define the boundaries of the contaminated area, then it would be best to do grab sampling. And then in the case of a very, very large area where you're trying to get a broad and general understanding rather than identification of spot hot spots or defining uh or delineating the boundaries or the um you know defining the contaminated area. If you need to have a uh a better understanding over a large area, then a composite sample would be you know uh an opportunity to do that where you're just grabbing um multiple samples and pulling them together and mixing them up and then just analyzing one sample from that. That gives you an idea of a broad and general area. Now, in the case of doing remediation in soil, it really if if you're going to use two both types of sampling, you really need to start by using grab samples. Grab samples are a specific con, you know, a location that identifies exactly at that location what that sample indicates. And of course, when you take a sample, it is basically giving you an understanding of not only that exact location, but everything in the broad and general area. So the smaller the area that you're that you are um uh going to remediate, you know, you could define the the cleanup area or the the soil to be remediated as being like the four corners and a middle sample. Okay. Now the further out the contamination has spread, making uh the the area that needs to have the soil remediation performed upon, the further out it is spread, the more data points you would want to add in between those four corners and throughout that middle instead of just one in the dead center, you know, you would want to step out from those. So, and then uh if you're going to um re do your remediation, whether you're digging and hauling, whether you're treating, however you're doing it, um you would want to go back to those same locations that you took those samples from, those grab samples, and after performing your remediation or excavating that contaminated soil, you would want to then go back to those same exact locations that you tested before and grab samples again and test again. So uh, you know, again, the the difference in the grab sample and the composite sample is the grab is a specific location versus a composite is a mixture of a bunch of grab samples. And so if you have a large area that you have uh excavated or treated, um then at that point in time, having done that already, then it might make sense to uh then do a composite sample, going back to all those locations, and uh if it was a larger area and and knowing that you did the same thing, you treated the entire area the same way, or you excavated, you know, three inches across the board everywhere, uh, then you might want to run a composite sample. Now, in in the case of, for example, our ongoing sponsor, Hambi Environmentals field test kits, it is a low cost per sample for soil analysis. You're getting a result in four minutes and at $35 a test, and it's very accurate within 10% of a lab result. So it's such a low cost per sample, it would be my recommendation to bypass doing a composite sample at all and always do grab samples because or do a combination of the two. But be you know if you're going to go to those different locations and do pre-treatment or pre-escavation samples to determine the hot spots and to and define the boundaries of the contaminated area, then you would want to go back to those same locations after you have either excavated or treated and to see what kind of effectiveness you've had on your treatment or uh your excavation and determine if there's anything left. And if you go back to all those same locations that you did the first time, you would know that okay, there's the difference between the two, right? And maybe, like let's just say, in the case of the simplest, smallest little area of four corners in the middle, but you know, um, say three of the four corners and the middle all came back as being fine, but that one uh corner still had a hot spot, maybe from elevation change, as there's a there's a slope there, so that's where the contamination migrated towards the most, and so it's the low point. So by doing those grab samples and before and after in the same locations, you were able to determine that that one location is the hotspot that you need to refocus on, either treat some more or or excavate some more. However, if you were to have done those as a composite sample, taking all five of those four corners in the middle, all five of those samples and mixing them together, they would blend, they would have blended out that hotspot and you wouldn't know that hot spot exists. So that's why I always recommend, you know, if you have uh the opportunity to forego doing composite samples and doing the grab samples, then that is the best case scenario because you can easily identify if there are any spots that need additional work, you know. Um so but anyway, that's the difference in a grab sample and a composite sample. Is a grab sample is going to r dial in uh it's not gonna be averaged out by the other samples. That's the possibility that what could happen with a composite sample is the other samples, you know, could average out the the hot spot that needs the additional work and you won't know that. That's why now if it's a huge area, then I mean obviously again stepping out. Um I understand the concept of doing a composite sample. However, if you've got a reliable economical um means of doing a grab sample analysis, such as the Hambi environmental field test kits, that is the best approach as opposed to doing a composite sample where things get blended out and averaged out, and you may not have that hot spot. So that's what I wanted to go over today in this 55th episode. I wanted to go over the two different types of soil sampling as it relates to remediation work. The grab sample is a specific location uh versus a composite, is a composite is a mixture or blend of multiple grab samples, and it creates the opportunity where things could get blended because uh and blended and averaged out, so you don't really see that hot spot versus specific grab samples give you the opportunity to identify a possible hotspot that may need some additional attention. So and again, the main difference between the two is a grab sample is at a very specific location versus a composite is a collection of multiple locations and blended together. Um, so that's what I wanted to go over today. So thank you for tuning in uh to our 55th episode. Thank you, Hambi Environmental, for your ongoing support of this podcast. Uh Let's Talk Remediation, where we're trying to have a positive impact on the environmental remediation. And as always, if you have a topic you would like for us to uh have on a future podcast episode or a specific question you'd like for us to address, please don't hesitate to reach out via email. My email is C Fader, that's C Frank A-T-O-R at Let's Talk Remediation.com. And with that, I'm your host, Charles Fader, and I am out This week's episode has come to an end.

SPEAKER_02 12:07

But the fun doesn't have to stop here. If you have any questions, suggestions, or feedback,