In this remediation webinar we are pleased to have with us as a special guest speaker Mr. Matthew J. Valentine, P.G., LRS, Vice President/Project Manager at Woodard & Curran. Mr. Valentine is also joined by Mr. Barry Poling, Central Regional Manager at REGENESIS. This presentation is a case study of a site in South Carolina contaminated with TCE, where PlumeStop® Liquid Activated Carbon was selected to remediate the 1,700 foot TCE plume. Mr. Valentine and Mr. Poling discuss the proces from the pilot study to the full scale implementation, covering why PlumeStop was selected, the conceptual site model, and the remediation results to date. Questions from the live audience during the webinar are also addressed.

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Did you have any problems getting regulatory approval with PlumeStop in, say, South Carolina?

We did not. They were very receptive to just about everything we did and in particular the UIC process went very smooth and they were extremely easy to work with and had no issues.

For the injection, did you use injection wells or injection points or direct push?

We use direct push. We use those. We did consider using injection points, permanent injection points, but in this environment it’s just as easy to go in with the DPT and it turned out to be very successful.

Is the source area being addressed and if so with why and how’s it going?

Yeah, I did touch on that originally back in 2010. We had done a fair bit of work in the source area which culminated in a pilot test using zero-valent iron we injected in the pilot and it showed positive results. So we implemented a full-scale injection using that product and it was marginally successful. It did shrink the plume a little bit. We found out that additional work needed done.

So in 2014, we contracted with Regenesis and used a combination of 3DMe, HRC and BDI in a little larger treatment area that extended under the building and that seemed to be quite successful. We’re in the process of performance monitoring to evaluate those results but we’re seeing to date is some contraction of the plume, particularly at the leading edge and along the sides of the treatments zone, which is what we’re expecting. So those wells in the source area will also be included in the January 2017 sampling event and we will be able to further evaluate the performance of that work.

Is the downgradient residential area concerned for vapor intrusion?

It’s not. And the reason being, our unit that we’re most concerned with…well, first of all, the plumes not there yet. It is a concern, I mean, it would be a concern had that had the plume continue to migrate. But what we have is our zone of concern is located from 25 to 45 feet below the ground surface and as I mentioned in when we were looking at that cross-section there is a zone of cleaner water in unit one that extends from 5 to 25 feet below the ground surface so that that keeps vapor intrusion from becoming an issue.

How long did the full-scale application take to implement?

It took a little over two months to complete I believe we probably could’ve knocked two weeks off of that time frame had we not had the access issues. We had particularly at barrier three. And then I’d say we had additional delays related to the injection problems that we encountered barrier one when we were having difficulty injecting the product at that tighter clay in that portion of the formation.

In the low-lying swampy area what types of special actions were needed to work in there?

Well, yeah we talked about that. I got to show some nice pictures of what we were dealing with. So initially when we were doing the pilot and we encountered what became a huge swamp. We tried many things we tried bringing in gravel with your textile, plywood many different things and what we ultimately found that that worked was just use of timber mats. So it did extend the amount of time, but once we were able to get the mats and procure them and move them around, it ended up being a…that’s what we used.

And for the full-scale, we, you know knowing what we learned from the pilot, we knew we had to put a road in and that’s what we ultimately did and then that that made it much simpler to get to the locations.

Was this swamp or a wetland? Were there any wetland issues regulatory issues you entered?

They weren’t. And it’s only a swampy area because it does dry out. You know most of the year, it’s just when you get large rain events, it drains. I mean, it lays there but it takes a little bit of time to drain but ultimately it does dry out.

So you mentioned that you had some trouble injecting at barrier one what sort of trouble and how do you work around that?

Well, that that goes on to the injection pressure that we had. They were significantly higher in barrier area one and we attributed that to just the fact that there were fewer sand stringers that were there to accept the product as we were injecting. It was interesting, you know, after the experience of barriers two and three, where we had no problems at all.

We weren’t it and we got up to barrier area one and just encountered this tighter formation and so with the use of higher injection pressures, we were able to inject the product that was required at each of the areas, that being the core, and then the outer portions and the flanks of the plume. On that western side, as we showed, we weren’t able to get all the points in, so what we ended up doing was injecting say double the volume and maybe half the points that were required. So we did get all the volume in it just wasn’t in each of the points that that we had originally planned on.

I noted that cis production was lower with PlumeStop than ERD, but it was still increasing as a last data point, what do we think is occurring here?

You know, as I mentioned, in most of our data were seeing peak cis and vinyl concentration that six months to a year, post-injection. So there’s that is there the potentially could go up a little bit from where it’s currently at 1 ppm. I think that could occur, but I were close to that number. I really feel like we’ve reached our peak levels and then we’re going to start seeing on down.

And is that breakthroughs a rebound? You know I wouldn’t call it rebound. There’s a mass transfer phenomenon with carbon in general that there’s a greater affinity to sort of TCE than their at cis. So one thing to remember, this is a barrier, it’s a pilot test and there this upgradient parent mass continuing to flux through.

And so as a flux through and there’s a equilibrium between absorption and degradation, you can see…We think that’s why we’re seeing the 1 ppm at cis. But if it’s a standard ERD approach, we would expect 20 ppm at cis or more. So there’s a lot on there or it’s being degraded rapidly.

Another question that’s for me, and I’ve seen this question in many forms, it’s vinyl chloride. Why haven’t you seen vinyl chloride? You’re correct that we haven’t seen monochloride at the site. We have seen ethane and a few the samples in certain areas. So that is there.

The geochemical parameters support reductive dechlorination. So we’re confident with the fact that the end product is being developed and geochemistry is correct. We’re seeing sulfate reduction all those sorts of things you want to see.

We’re confident that we’re seeing complete degradation so the question where is the vinyl chloride, there’s two possible scenarios there? One, it’s being degraded more rapidly than then it is being released into the water, so you’re not seeing it in the water. The other is that it’s just sort on the carbon so never actually releases from the carbon it goes completely through that degradation process without seeing them. And we’ve seen that on other sites as well most of the PlumeStop and ERD sites that I’ve reviewed, daughter product production is muted compared to ERD alone, yet the geochemistry looks very similar.

Were there any underground utility challenges at the site?

There were not. There is one sewer line that runs down through the area but it wasn’t in the area where we were doing our injections so we, after having it defined, and we had that the local utility come out and confirm its location. We really didn’t have any issues with that at all.

What about the pH in the groundwater? And I’ll take that Matt.

In that one of the earlier slides Matt showed, we did shows the pH did in one of the wells. We saw pH drop below 6. In our experience, biodegradation rates may slow significantly at a pH below 6. In this scenario we believe that the pH drop was temporary and likely due to an influx of organic acids released from the HRC in that localized area basically into the well. And we expect that to stabilize overtime. We believe this because it again if you look at the geochemistry we have solid evidence to support the biodegradation is occurring and that your ratios to TCE impact DCE in parent are there. So in this case, pH has not been a challenge thus far.

What’s next for the project?

That is a good question. We consider the remedial action that was done in both the source area and at least the downgrading area as being the final remedial action for the AOC-1 plume. Obviously, we’ll be evaluating the source area and if additional work needs done there, that will probably be the next thing that needs to be done. But on a site-wide basis, we are in the process of conducting a risk assessment for the entire site. And then depending on the results of that risk assessment, we may be conducting some form of limited corrective majors. We’re actually in the process of evaluating that right now and in the short term we will be conducting some additional groundwater monitoring, probably on a quarterly basis for at least another year or two to evaluate the success of the remedial action in AOC-1. But we feel the rest of the site of the other two AOC’s and all the other SWMUs have been adequately addressed and we expect them to move forward through the risk assessment and we’ll have to see what happens beyond that.

Video Transcript

Dane: Today’s presentation will focus on Accelerated Biodegradation of Chlorinated Contaminants Using In-Situ Liquid Activated Carbon. With that, I’d like to introduce our presenter for today. We are pleased to have with us Mr. Matthew Valentine, Vice President and Project Manager at Woodard & Curran. Mr. Valentine has over 26 years of professional experience in geology, hydrogeology, and geotechnical engineering projects. For the past 16 years, he has managed a wide variety of project ranging from environmental assessment and geotechnical investigations to feasibility and corrective measures studies.

He has conducted, supervised and managed subsurface explorations, remedial investigation, and site characterizations at numerous contaminated sites. We also have with us today Mr. Barry Poling, Central Regional Manager here at Regenesis. He has 15 years of experience in the environmental industry including extensive experience in Phase I and Phase II site assessment remediation, and industrial compliance. He provides senior leadership in the areas of remediation design, strategy, and business development. All right, that concludes our introduction. So now all hand things over to Matt to get it started.

Matt: Thanks, Dane, I appreciate the introduction. I appreciate everyone for attending the webinar. This is a case study of a site that our company’s been working on for over 20 years. We became involved in the site shortly after the RCRA Facility Assessment was completed in the early ‘90s.

The first thing I’d like to go over is just an outline of the presentation. And let you know that there’ll be a project summary that I’m going to review. And a little bit about the site background and description of the site or the pilot study and the results of that pilot study. And then, the remedial design that we went through with the help from Regenesis, the full-scale remedial action that we implemented, and some preliminary results that we found based on the initial performance monitoring that we’ve completed.