WEBVTT

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>> >> So now on to the water bearing zones at the site, so the main aquifer at

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the site is the Trinity aquifer. For this

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site we have designated three different aquifer zones. We have

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a lower stand, and lower Stan one, and lower stand to. And again, below that is

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our [ Indiscernible ] the water at the site depth is a 50 feet below ground. It

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migrated through the zone, and into the upper sand aquifer.

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>> As I said, there were numerous supply bells,

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the contamination Crandall

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into the lower San Juan and thus lower stand to two. Contamination is

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the most extensive in the lower sand one. So that is what were generally known

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as were talking about today, will be the remaining, focusing on

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of next year, so it's the middle aquifer unit.

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>> So, let's look at a plume map.

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This is our PCE and

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contamination from February to March 2016, and again in the lower San Juan.

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>> We did remove some of the pumps from several of these wells, and we

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digitally log them, and also

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put a downhole camera in video so we could see where the screen was, and then a

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lot of the residents in the area, actually knew how deep their wells were. We

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did realize that some of these wells were screened in the lower San Juan, and

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little bit of lower sand too, but predominantly they are pulling water from that

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aquifer unit.

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>> Sherry, this is Jean, before you go any further, we have a report

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on the background noise, think it's at happening when you

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are moving your mouse. So I just

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advocate that we not use your mouse for a little bit and see if that will

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handle it.

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>> So when we had

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application at the site, we plug the leaky supply wells, some of these wells

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that were contaminated, we went ahead and we over drilled them. And we plug

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them. And then, we also found open boreholes. This is a bedrock formation. So,

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when you drill a hole, a well, in this formation,

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so historically a borehole would be left where the

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pump would be left, and we found several of those and plug them as well. We

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then replace the private supply wells that were contaminated. They were new

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wells, that we were drill deeper into the

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lower sand too, and we put that in uncontaminated portions of the article 1st

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so that they would have clean drinking water the other thing we did, was the

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horizontal SB E system, and then we also been installing

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.

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So the focus of the rest of this talk

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is going to be on the permeable reactive barriers. So we installed these

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interfaces at the site, and so, when we look at this figure and we look at the

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yellow barriers, those of the first barriers that we installed. They were the

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phase one and phase two barriers. Those were in stand installed in the upper

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sand aquifers so the very first aquifer. We injected emulsified vegetable

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areas or EV oh. The next

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that was installed was the orange spirit, this was a phase three barrier we

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named the Stephenson

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Avenue barrier, it was named after the road. And this would be the main focus

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of our talk today this original barrier that we install. This barrier is a plume

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stop area. After that we installed the green barriers, most barriers were

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installed in the and lower San Juan and lower sand to. And those were installed

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with microscale CBI.

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>> These are plume stop barriers.

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>> Okay, I'm going to go over kind of the challenges with the installation of

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the barriers. And I'm going to speak in general, but for the most part, we will

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be a discussion regarding that first plume stop barrier that we installed on

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Stephenson.

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>> And so this is the best Evenson barrier, and the pictures you see are the

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Stephenson barrier injection, and

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the drilling, and just the final completion.

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>> So what I'm going to talk about, we will start with placement of the barrier

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and the injection wells. Then we will talk about well screen placement. We will

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talk about vertical profiling,

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in the aquifer. We will talk about the segmentation of fractures, and talk

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about injection issues, and we will talk about in temporary

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increasing contaminant levels that was a down gradient.

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>> So the first they will talk about is the placement of the bearers and the

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injection wells.

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>> So we are back to our same plume map from 2016. And in green there, it's

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showing you where we put in the first plume stop

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barrier in lower sand one. We did this to protect

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those private supply wells. We didn't want the plume to migrate, and affect

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the private supply wells downgraded, so this was a sentinel barrier almost. So

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the barrier length was 300 feet. It had

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24 injection wells, and had six

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performance assessment wells and these were placed upgraded and downgraded, so

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we had wells that we could watch and see what was going into our barrier, and

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then we had wells down gradient to show us how the bear barrier was performing.

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I'm goodies my pointer sorry, we also had GW 207, and she

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[ Indiscernible ]

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>> The treatment in a verbal is about 85 feet 205 feet from the San Juan. And

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we performed the sampling on this first

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barrier regularly, we did it for 30 days, 60 days, 90 days, 120 days,

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180 and 365 days after injection.

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>> So plume stop, what is plume stop, if you don't know,

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stop is an activated carbon to absorb and retired movement of contamination

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within a treatment area. Why do we select plume stop? We didn't want to Melba

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lies metals that would impact product

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private wells. With our emulsified oil barrier we had in the upper sand close

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to the source area would cause chlorination reducing conditions in this cause us

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to have Mac Minis, iron, coming to the solution.

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The other was the longevity, the design for our plume stop barrier was 15

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years. With our

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email various we were having to read inject after 18 months, then we were

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having issues maintaining the pH we were having to inject sodium bicarbonate at

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to get R.Ph. more to a neutral position.

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>> The other was lower analytical costs. With our

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DBO barriers we were having to monitor VOCs,

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total organic carbon, nitrate sulfate, we were also using a down pole meter to

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monitor to the

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oxidative conductors, and the pH.

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With our plume stop barrier we were only going to have to monitor for VOCs and

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we were going to use passive diffusion bags. So it was definitely a cost savings

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there.

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>> So this is our original design for the B barrier.

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How we did this design, we usually use the established radiance influence from

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our EV oh pilot test and the injections that we had done in the upper sand water

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bearing zone.

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>> Now we really sell the

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lithology in the upper sand was equal, so we thought that

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spacing would be appropriate, and our EV oh injection of spacing was 20 feet.

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Genesis really wanted us to do a pilot test, and we didn't know plume stop was

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originally introduced in this project. And we opted

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to reduce the well spacing of the barrier. It was actually cheaper to install

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two more wells than to do the pilot , so we installed the barrier

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and injection wells every 12 1/2 feet.

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>> And then the wells green placement

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how we

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drill in Odessa and at the site is with air rotary. We had tried previously to

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drill with sonic, but we have never had any success with it in this area. In

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fact we've only been

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able to get to about 70 feet. So with the air rotary drilling method, it was

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kind of difficult to place the screen. We were looking at cuttings, and we

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wanted to be exact or screen because we wanted to make sure our amendment ended

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up in the exact place we wanted it to be. So, we started using geophysical

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logging to aid in placement of the well screen. And we locked natural gamma,

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resistivity's, spontaneous potential, conductivity and caliper. And this is an

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example of one of the geophysical well logs from one of the injection wells. As

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you can see, I have pointed out there where the lower sand one is located, and

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so we were looking for that interfere with our geophysical law every fourth

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borehole. And then we would literally play Starscream specific link.

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It was 12 feet, we would cut our screen so it was 12 feet and then we would add

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and glue and screw are in caps on the end. And that way we had that specific

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interval flooring injection.

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Because his physical logging was sold

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helpful, after this barrier, subsequent barriers, we actually logged every

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other borehole.

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>> The next thing we did, with vertical programming we installed

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yet, at various depths intervals

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we let that sit in our well it about two weeks, and sampled it. So the results,

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are shown on this cross-section, and this is PCE. And, at the top you can see

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[ Indiscernible ] injection well 13, this is the well in the north end of the

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barrier, then you go all the way down

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to injection 36 which is the well on the South barrier. Then you had your depth

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below ground surface there.

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>> Then you have your PCE concentration and those are in micrograms per liter.

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And then, the pink is showing where the concentrations were

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above the MPL, and the darker pink is where the higher concentrations were.

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Kind of as expected, we got that concentration would be towards the middle and

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the bottom of the formation, in the area that we

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were locating treatment at the aquifer. But what was kind of surprising, we

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were very surprised, that we had concentrations that were below the

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NCL below are barrier alignment.

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>> We were really concerned, so we went ahead, and we resampled the middle

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interval of our passive

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diffusion bags, and the results concerned that yes, we had areas where the

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concentrations were below the FCL. So, we are to go back to that original plume

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and this is from 2016.

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>> I don't know if,

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when you saw this plume configuration you thought that this is really strange

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looking, and we thought that as well, and we could not decide a lot of times

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whether the contamination was coming over here, or over here, we want you, it

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was because we had these two private wells that were

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below the MCL, and it just wasn't making sense. We actually pull the pump in as

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well, and we had Jill physically locked it, and we put

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a camera in it to determine where the screen was, and it was screened

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identically to our upgrading monitoring plume that was in the lower sand one. So

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it was screened in the lower sand one, the pump with that, we went

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ahead to the baler and grabbed a tap sample, just a figure, just in case where

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we were sampling the tap and maybe it was tied into a well we didn't know about.

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That also was confirmed in the results.

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>> So now we look at our aerial expanse of our ace line PCE

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concentrations along the barrier. You can see we have clean zones that are

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noted in the baseline sample

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along the barrier alignment. Is indicating that we have preferential migration

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of the broom. We had

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differentials cementation creating a permeability contract. The interesting

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thing is

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is if we hadn't had wells every 12 feet, we would've never seen that. So it's

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really kind of cool to actually see this level of detail of our plume, and it

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was kind of eye-opening, in fact we installed initial

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barriers up gradient, the green bears, we had the same inner fingering, the

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same thing was going on, and in fact this area here is a more realistically

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connected portion so the contrast would be even more extreme.

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>> And the other thing is that we have other sites that are in a similar

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formation that we installed

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wells close apart like this, and it's amazing, just the detail that we were

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able to see the core of the plume coming through in such detail because of that.

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>> So, now you know, we have cementation

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issues, and how is that going to affect our injection. Well it did in fact

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start injection as you would think. So areas where we had high injection rates

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and low pressure, is areas that we had of course, cementation in our fractures.

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At another site, we were able to inject, pressure and before we know it, we were

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having plume stop 30 feet away immediately.

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>> And so, we had to lower our injection rate to be able to obtain a better

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coverage. So we had to make sure that we decreased the injection rate for that.

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For errors where we have well cemented we had low permeability and little to no

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flow.

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In our cemented barrier application, and it wasn't a concern there, we had some

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cementation, but the cementation didn't affect us to the extent there we didn't

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have flow. We would have lower flow, but we wouldn't have no flow.

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That green barrier application that was further upgraded, we literally had

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cementation so strong that we had no flow.

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>> So as injection progress, also, our pressure would rise, and we increased the

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injection race

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rate would increase. And

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on most injection rates of that type it does happen. We held our injections to

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five gallons per minute and are pressure to

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100 psi or less, we would have much more success with how quickly we can get

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the product into the well.

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>> This is kind of another example of the cementation of low flow. This is

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within the same straight, so if you look at our Stephenson

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Avenue Barry, you can see that our injection rates are 5 to 60 gallons per

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minute and the injection pressure was 4 to 77 pounds per square inch. We were

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able to inject the full volume in this the barrier. Then Wayne we installed the

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Stephenson Avenue extension barrier

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just next door, our injection rates were 1 to 10 gallons per minute of the

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pressure was 10 to 120 psi. We had several wells that did not accept the full

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dose. So just in the short difference we got such a distant. So you have to ask,

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what happens when we aren't able to get the fold

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goes in, we actually injected it into a Jason well that will take the volume so

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that we can meet our design specifications.

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>> Other issues that we had is that

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we had surfacing. This rarely occurred during the initial injection. And in

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this well, it's interesting, this

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is injection well 28, and it was a second well that we injected into on the

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Stephenson barrier. And we had surfacing, so we had to keep our pressures below

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hundred psi. That was kind of a learning moment. I will say that we did the

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second injections, we did have more frequent surfacing. The other thing we had

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was, we had plume stop go up in as one of our up gradient performance systems

233
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wells. It was a preferential pathway to that well as we injected and we could

234
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get

235
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it in that well in our concentrations were undetected and that will so it's not

236
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a

237
00:24:18.000 --> 00:24:21.000
performance assessment well, anymore.

238
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>> The other issue we had, we had a temporary increase of contaminant levels

239
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down gradient.

240
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>> I understand this is not true for every site. And I think read Genesis has

241
00:24:29.000 --> 00:24:33.000
made it that most sites do not occur at, but it did happen here. And if you look

242
00:24:33.000 --> 00:24:36.000
at the baseline results from 2017, and if you look at JW 207 which is the first

243
00:24:36.000 --> 00:24:42.000
private supply level where the concentrations were

244
00:24:42.000 --> 00:24:45.000
below the MCL, but in July 2018 the concentration had increased to 12.8

245
00:24:45.000 --> 00:24:48.000
micrograms per liter.

246
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>> So we had inject 34,000 gallons of plume stop

247
00:24:52.000 --> 00:24:56.000
and water mix, and it appears to have pushed the bloom towards as well. And I'm

248
00:24:56.000 --> 00:25:02.000
sure the stresses from the well, aided in that.

249
00:25:02.000 --> 00:25:08.000
>> We were sampling on a frequent interval which was really

250
00:25:08.000 --> 00:25:11.000
a good thing, because we were able to catch this relatively quickly. And we

251
00:25:11.000 --> 00:25:14.000
added a point of use filtration to this house.

252
00:25:14.000 --> 00:25:18.000
Then we did a partial second injection.

253
00:25:18.000 --> 00:25:24.000
>> So I wanted you to look at the park

254
00:25:24.000 --> 00:25:30.000
concentration trends for well GW 207. What you're seeing here is the

255
00:25:30.000 --> 00:25:34.000
yellow line as the MCL, and then the black lines that are coming in here, and

256
00:25:34.000 --> 00:25:40.000
here, are when we did injections. And these are baseline injections here,

257
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and that's a partial injection we did, and you can see the before the baseline

258
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we were before the MCL, and closer to the injection, we went up and down through

259
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the MCL, and then continued to that

260
00:25:54.000 --> 00:26:03.000
12 micrograms per liter that I showed you previously, then we started to greet

261
00:26:03.000 --> 00:26:05.000
decrease. We were concerned about this, so what we did, we ended up installing

262
00:26:05.000 --> 00:26:08.000
three additional wells up gradient of this area.

263
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>> I want to point out that we have a performance assessment well here. Soon

264
00:26:12.000 --> 00:26:21.000
after, we were able to track our concentrations to reduce

265
00:26:21.000 --> 00:26:24.000
to the low MCL's in the upper two intervals of our passive diffusion backs, but

266
00:26:24.000 --> 00:26:27.000
the lower interval never, ever, would decrease. So, we went back, and we looked

267
00:26:27.000 --> 00:26:38.000
at the

268
00:26:38.000 --> 00:26:41.000
geophysical laws for these wells, we notice that there seem to be a small sand

269
00:26:41.000 --> 00:26:44.000
interval that we actually did not scream. So we went back with these additional

270
00:26:44.000 --> 00:26:47.000
wells, three wells that we did up gradient, and we screened those in that deeper

271
00:26:47.000 --> 00:26:50.000
interval, in that Santa did catch that sand and to address this interval as

272
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well, this passive diffusion back.

273
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>> And then, after that our concentrations decrease and by September 2019, we

274
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were below the MCL for PCE.

275
00:27:01.000 --> 00:27:08.000
>> Well, we were very excited. We had in W 58, and now lowering all the

276
00:27:08.000 --> 00:27:11.000
MCL's, private supply well is back in business and below the MCL's, but now we

277
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had this issue on this other upper barrier.

278
00:27:19.000 --> 00:27:26.000
>> So this is the concentration trend map for MW 59, and you can see

279
00:27:26.000 --> 00:27:30.000
at three different intervals the concentration of PCE, the initial injections,

280
00:27:30.000 --> 00:27:33.000
the concentrations all drop below the MCL's and then we had a spike in the

281
00:27:33.000 --> 00:27:37.000
interval again.

282
00:27:37.000 --> 00:27:41.000
>> So we were perplexed. We were like, why are we having this? And some thoughts

283
00:27:41.000 --> 00:27:47.000
were that it was possibly caused from back diffusion from primary

284
00:27:47.000 --> 00:27:58.000
ferocity, or this was also the area where we have that surfacing occur.

285
00:27:58.000 --> 00:28:02.000
>> So here is in W 59, and here is the well where we had the surfacing occur,

286
00:28:02.000 --> 00:28:05.000
and we weren't able to get the fold goes in there, but we kind of put it in at

287
00:28:05.000 --> 00:28:13.000
the high enough gallons per minute, so maybe we had an area where we didn't have

288
00:28:13.000 --> 00:28:16.000
injection. So we installed another injection well up gradient to replace it.

289
00:28:16.000 --> 00:28:21.000
And we were going to go ahead and reinject in this barrier. We did that because

290
00:28:21.000 --> 00:28:27.000
number one, we were at the same time installing two other barriers

291
00:28:27.000 --> 00:28:31.000
. And so we were already out there. It wasn't to take much effort to reinject in

292
00:28:31.000 --> 00:28:34.000
these wells. And the other thing is we wanted to be protective of the product

293
00:28:34.000 --> 00:28:38.000
supply

294
00:28:38.000 --> 00:28:41.000
down gradient. So at this time of the design of these barriers here, we

295
00:28:41.000 --> 00:28:46.000
actually got some additional information to help us determine better well

296
00:28:46.000 --> 00:28:51.000
spacing. And what we did was, we put in in viral flux

297
00:28:51.000 --> 00:28:55.000
passive flux meters, these passive flux meters they measured time average

298
00:28:55.000 --> 00:29:01.000
cumulative contaminant Max on

299
00:29:01.000 --> 00:29:05.000
fluxes and groundwater fluxes. We did this on several wells in the other two

300
00:29:05.000 --> 00:29:10.000
barriers we installed, and we did it up gradient of the existing Stephenson

301
00:29:10.000 --> 00:29:16.000
barrier. >> And so, this is the

302
00:29:16.000 --> 00:29:21.000
passive flux meter and they are composed of granular activated carbon and a

303
00:29:21.000 --> 00:29:24.000
tracer. And they are sat inside her well. They have to fill the hole

304
00:29:24.000 --> 00:29:28.000
portion of the screen, they are actually really tight in the well because they

305
00:29:28.000 --> 00:29:32.000
want the water to flow through there.

306
00:29:32.000 --> 00:29:36.000
They sit in the well for about two weeks, and then you pulled them back out,

307
00:29:36.000 --> 00:29:43.000
and you can sample intervals with in each of the passive flux

308
00:29:43.000 --> 00:29:50.000
meters. We did three intervals, so we broken into three samples, and then in

309
00:29:50.000 --> 00:29:58.000
viral flux calculates the velocity and the PC mass flux.

310
00:29:58.000 --> 00:30:02.000
And what's interesting is this well up gradient of our Stephenson barrier was

311
00:30:02.000 --> 00:30:07.000
moving two times faster than anticipated.

312
00:30:07.000 --> 00:30:12.000
So using this information in the information we gain for all the

313
00:30:12.000 --> 00:30:17.000
other

314
00:30:17.000 --> 00:30:20.000
activities, we decreased from 12 1/2 feet to 11 feet.

315
00:30:20.000 --> 00:30:28.000
>> So, in June 2020,

316
00:30:28.000 --> 00:30:31.000
we reinjected in the Stephenson Avenue barrier, we reinject the 47 gallons of

317
00:30:31.000 --> 00:30:38.000
plume stop water mix. So we were really

318
00:30:38.000 --> 00:30:40.000
only going to inject in wells that were above MCL's are baseline in the

319
00:30:40.000 --> 00:30:45.000
sampling

320
00:30:45.000 --> 00:30:50.000
. Unfortunately, we had some issues with injections. Are injection rates were

321
00:30:50.000 --> 00:30:53.000
relatively low. They were 3.48 gallons per minute, we had to keep the pressure

322
00:30:53.000 --> 00:31:03.000
relatively

323
00:31:03.000 --> 00:31:06.000
not to exceed 50 psi because we started seeing servicing as you see in that

324
00:31:06.000 --> 00:31:10.000
picture there. The surfacing was more extensive during the reapplication, and

325
00:31:10.000 --> 00:31:14.000
several wells could not take any volume. We totally lost well capacity. We were

326
00:31:14.000 --> 00:31:17.000
able to inject in most wells. And what we ended up doing, is injecting in some

327
00:31:17.000 --> 00:31:20.000
of the wells that we had below the MCL that we had not prided injected in, and

328
00:31:20.000 --> 00:31:27.000
so that way the

329
00:31:27.000 --> 00:31:30.000
body was provided. What is the end result? The end result ended up being good.

330
00:31:30.000 --> 00:31:40.000
>> From October

331
00:31:40.000 --> 00:31:43.000
to December 2019, you can see that's where we had our high concentrations, and

332
00:31:43.000 --> 00:31:46.000
then here is our July through September 2020 concentrations, and we have

333
00:31:46.000 --> 00:31:49.000
successfully stopped the PCE contamination from going through the barrier. So,

334
00:31:49.000 --> 00:31:54.000
the results were good.

335
00:31:54.000 --> 00:31:59.000
>> Real quickly, I think I'll just go through some of the trend graphs for the

336
00:31:59.000 --> 00:32:03.000
Stephenson barrier. This is your well that is up gradient,

337
00:32:03.000 --> 00:32:08.000
in the barrier, what's coming into the barrier.

338
00:32:08.000 --> 00:32:13.000
>> And then these are the wells

339
00:32:13.000 --> 00:32:18.000
that we use the performance assessment down gradient of the barrier, and this

340
00:32:18.000 --> 00:32:23.000
is when we inject it, this is the second injection, and you can see the

341
00:32:23.000 --> 00:32:26.000
concentrations moving down relatively quickly, we had a little bit of a spike,

342
00:32:26.000 --> 00:32:29.000
in that well that we talked about, now we are below the MCL.

343
00:32:29.000 --> 00:32:33.000
>> In addition,

344
00:32:33.000 --> 00:32:39.000
we do some modeling

345
00:32:39.000 --> 00:32:48.000
of the barrier. And they use a plume stop plume force model. This is an example

346
00:32:48.000 --> 00:32:51.000
of the model. This is what what was done for MW 59, for the 91 foot interval

347
00:32:51.000 --> 00:32:59.000
, I think that's the upper interval on this well. And, this is showing, the

348
00:32:59.000 --> 00:33:02.000
model is showing how concentrations are going to decrease. As the water goes

349
00:33:02.000 --> 00:33:06.000
through the barrier.

350
00:33:06.000 --> 00:33:13.000
So the model is competitive and dynamic and it

351
00:33:13.000 --> 00:33:17.000
predicts back diffusion and contaminant breakthrough, and he considers the

352
00:33:17.000 --> 00:33:21.000
following design parameters. Groundwater velocity, contaminant mass flux,

353
00:33:21.000 --> 00:33:30.000
degradation rates, daughter products,

354
00:33:30.000 --> 00:33:32.000
and degradation factors. Here now is the model with our data applied. So you

355
00:33:32.000 --> 00:33:40.000
can see the model actually predicted pretty well what are concentration trends

356
00:33:40.000 --> 00:33:45.000
were going to be. And you need to note that it takes time

357
00:33:45.000 --> 00:33:52.000
and

358
00:33:52.000 --> 00:33:55.000
observations because number one, our wells are 29 feet away from the barrier

359
00:33:55.000 --> 00:34:00.000
that's because they

360
00:34:00.000 --> 00:34:04.000
are further way, if we had wells closer we could see the concentration trend

361
00:34:04.000 --> 00:34:06.000
drop more dramatically. As concentration trends will be reduced due to gradual

362
00:34:06.000 --> 00:34:12.000
distance, and

363
00:34:12.000 --> 00:34:16.000
TCE and DCE influences observed before PCE influence due to retardation

364
00:34:16.000 --> 00:34:21.000
factors. >> Hears the same model, and we've now take it out, we've taken it down

365
00:34:21.000 --> 00:34:28.000
through the whole distance. This is

366
00:34:28.000 --> 00:34:32.000
220 20, and the model is predictive and allows you to anticipate data trends,

367
00:34:32.000 --> 00:34:37.000
it's qualitative and semi-qualitative.

368
00:34:37.000 --> 00:34:45.000
Performance should be allowed to

369
00:34:45.000 --> 00:34:50.000
use data noise, and data noise should be validated through multiple events.

370
00:34:50.000 --> 00:34:54.000
>> I would say, we'd have concentrations we not addicted and that we do give

371
00:34:54.000 --> 00:34:57.000
a liberal rise and I get a little excited, but the next time in the assembly

372
00:34:57.000 --> 00:35:02.000
would be down.

373
00:35:02.000 --> 00:35:08.000
>> So this is the model for 59 where we had [ Indiscernible ] and this is

374
00:35:08.000 --> 00:35:11.000
the whole where we did the initial injections of the application, and we just

375
00:35:11.000 --> 00:35:15.000
want to say that you know, this model

376
00:35:15.000 --> 00:35:18.000
was very beneficial, and the information that was used, we use this model, we

377
00:35:18.000 --> 00:35:22.000
also use the

378
00:35:22.000 --> 00:35:28.000
passive flux meters and geophysical logs

379
00:35:28.000 --> 00:35:34.000
to review and optimize and reapply the design. And once we did our

380
00:35:34.000 --> 00:35:37.000
reapplication of performance data and it was in compliance with MCL's and data

381
00:35:37.000 --> 00:35:42.000
is representative of all performance wells.

382
00:35:42.000 --> 00:35:53.000
>> And then kind of lessons learned. Well, I think what we were able to see

383
00:35:53.000 --> 00:35:56.000
by installing all the wells really close together, you could really see the

384
00:35:56.000 --> 00:36:00.000
plume details. And it was not just at the site, but other sites that we were

385
00:36:00.000 --> 00:36:05.000
doing the same thing at. You know, high-resolution site characterization direct

386
00:36:05.000 --> 00:36:17.000
push tools cannot negotiate submitted sands, this level of characteristics

387
00:36:17.000 --> 00:36:20.000
is costly to complete during remedial investigation. The pilot testing, I think

388
00:36:20.000 --> 00:36:23.000
it would be important to do the pilot testing. I think it would also be

389
00:36:23.000 --> 00:36:26.000
important if you know you had differential segmentation at a site where you have

390
00:36:26.000 --> 00:36:29.000
fractures for the site, or differential permeability, it would be really useful

391
00:36:29.000 --> 00:36:33.000
to be able to do the pilot at two areas if you do that. Used two different areas

392
00:36:33.000 --> 00:36:36.000
to see two different sites so you can better design your well space.

393
00:36:36.000 --> 00:36:44.000
>> I think the geophysical logging was essential.

394
00:36:44.000 --> 00:36:47.000
It was very useful to refine our screen intervals, and it focused treatment,

395
00:36:47.000 --> 00:36:53.000
and it reduced costs.

396
00:36:53.000 --> 00:36:57.000
>> Overpressure during injection does not work. It slows injection, you get

397
00:36:57.000 --> 00:37:07.000
back pressure, and you get surfacing. You kind of have to optimize what worse

398
00:37:07.000 --> 00:37:11.000
best for your site for the injection, you got to do that in the first couple

399
00:37:11.000 --> 00:37:14.000
days of the injection. And then as you do more at a site, you can refine it as

400
00:37:14.000 --> 00:37:17.000
we did to come up with a specific plan. And I will say, when we did the

401
00:37:17.000 --> 00:37:20.000
subsequent injections with the knowledge that we had from the initial

402
00:37:20.000 --> 00:37:22.000
injections, it really made the subsequent injections much easier.

403
00:37:22.000 --> 00:37:29.000
>> Plume displacement

404
00:37:29.000 --> 00:37:32.000
following injection results in temporary concentrations increases in our

405
00:37:32.000 --> 00:37:38.000
receptor wells. This happened at the site, and I think we needed to be prepared

406
00:37:38.000 --> 00:37:41.000
for that. Thankfully we were. We were monitoring a quote close enough you can

407
00:37:41.000 --> 00:37:49.000
see that we were able to treat

408
00:37:49.000 --> 00:37:51.000
-- Put a filtration system on that private supply well.

409
00:37:51.000 --> 00:37:57.000
>> Again, lessons learned from this

410
00:37:57.000 --> 00:38:00.000
first permeable reactive barrier were used for subsequent injections for

411
00:38:00.000 --> 00:38:05.000
additional barriers at the site and other sites with similar mythologies. And

412
00:38:05.000 --> 00:38:09.000
now we are happy to take questions. And we kind of have a panel

413
00:38:09.000 --> 00:38:15.000
that can help us with questions. And I will let them introduce themselves, but

414
00:38:15.000 --> 00:38:20.000
we have Jay Snyder from EA engineering, and we have Carlos Ortiz from

415
00:38:20.000 --> 00:38:27.000
read Genesis, and I let them both tell you a little bit about themselves.

416
00:38:27.000 --> 00:38:33.000
>> Good afternoon my name is Jay Snyder on a geological engineer with EA

417
00:38:33.000 --> 00:38:37.000
engineer, and I have been the senior had or geologists on this

418
00:38:37.000 --> 00:38:42.000
project for about a decade now. I've worked through the remedial investigation.

419
00:38:42.000 --> 00:38:45.000
Through the feasibility study, and these remedial actions,

420
00:38:45.000 --> 00:38:48.000
thank you.

421
00:38:48.000 --> 00:38:53.000
>> Hello, everyone

422
00:38:53.000 --> 00:38:57.000
I'm the district technical manager for read Genesis for the south-central

423
00:38:57.000 --> 00:39:03.000
district, and I am one of many on our team that collaborated with

424
00:39:03.000 --> 00:39:05.000
Jay and Terry at the site.

425
00:39:05.000 --> 00:39:10.000
>> All right, thank you.

426
00:39:10.000 --> 00:39:17.000
So, if it's okay with everybody, I think we will

427
00:39:17.000 --> 00:39:21.000
launch into our brief Q and a. And we do have a number of questions on the

428
00:39:21.000 --> 00:39:24.000
presentation. I'm going to start first with a little bit more background about

429
00:39:24.000 --> 00:39:27.000
the site. We've had a number of audience members that ask, Terry, where did the

430
00:39:27.000 --> 00:39:30.000
plume, or the contamination originate from questioner

431
00:39:30.000 --> 00:39:35.000
>>?

432
00:39:35.000 --> 00:39:39.000
>> It originated, let me see if I can go back, so it's original release was in

433
00:39:39.000 --> 00:39:42.000
this area here. It was a local chemical plant.

434
00:39:42.000 --> 00:39:45.000
>> Okay.

435
00:39:45.000 --> 00:39:51.000
>> I'd like to add to

436
00:39:51.000 --> 00:39:58.000
, Terry, I think of interest is they lost PCE and

437
00:39:58.000 --> 00:40:01.000
there was also a release contemporaneous of a fairly significant

438
00:40:01.000 --> 00:40:08.000
volume of naphthalene

439
00:40:08.000 --> 00:40:11.000
. So when we look at the groundwater's all you plumes in the source Etters

440
00:40:11.000 --> 00:40:20.000
there's PCE and

441
00:40:20.000 --> 00:40:23.000
VCE and not much TCE so I think a significant amount of decolonization took

442
00:40:23.000 --> 00:40:31.000
place.

443
00:40:31.000 --> 00:40:35.000
>> Okay. And actually, there were a number of attendees who wanted to know if

444
00:40:35.000 --> 00:40:42.000
you were measuring or monitoring for DC

445
00:40:42.000 --> 00:40:45.000
vinyl chloride at the site.

446
00:40:45.000 --> 00:40:48.000
>> Yeah, we've never had vinyl chloride at the site. And we did a little bit in

447
00:40:48.000 --> 00:40:50.000
our barriers down gradient, but that was it.

448
00:40:50.000 --> 00:40:54.000
>> All right, excellent.

449
00:40:54.000 --> 00:41:00.000
>> Several people had asked how bench or pilot testing specifically before you

450
00:41:00.000 --> 00:41:05.000
applied or used the plume stop at the site, so could you talk a little bit

451
00:41:05.000 --> 00:41:08.000
again, just revisit that concept of bench testing before injection,

452
00:41:08.000 --> 00:41:14.000
please questioner

453
00:41:14.000 --> 00:41:20.000
>> Bench testing we couldn't do because of the pilot for the rock, pilot

454
00:41:20.000 --> 00:41:24.000
testing we could've done but we opted not to do it at the site, but we did do

455
00:41:24.000 --> 00:41:27.000
it at another site. In the pilot testing, Carlos can kind of go into that, but

456
00:41:27.000 --> 00:41:35.000
we had to install multiple wells at various intervals and

457
00:41:35.000 --> 00:41:40.000
an injection well, and then they would come out and inject and we would

458
00:41:40.000 --> 00:41:44.000
monitor water level measurements and see when plume stopped arrived in the

459
00:41:44.000 --> 00:41:50.000
specific observation well and the time it took.

460
00:41:50.000 --> 00:41:53.000
>> I just -- Sorry, go ahead Terry

461
00:41:53.000 --> 00:41:56.000
.

462
00:41:56.000 --> 00:41:59.000
>> No, you go ahead.

463
00:41:59.000 --> 00:42:06.000
>> Yeah, I would just quickly add the specific contaminant

464
00:42:06.000 --> 00:42:10.000
of concern the isotherm's and the absorption are well established as to how

465
00:42:10.000 --> 00:42:14.000
well plume stop would work at the site. So in terms of the pilot study, we

466
00:42:14.000 --> 00:42:20.000
often, internally we call that a refined

467
00:42:20.000 --> 00:42:24.000
focus testing and we really focus on the delivery of distribution of the ROIs

468
00:42:24.000 --> 00:42:28.000
of the volatile, and it's really fine-tuning those aspects of the application.

469
00:42:28.000 --> 00:42:36.000
>> And we also did that in the build

470
00:42:36.000 --> 00:42:39.000
at the very beginning of the injections. So like the first two days we would

471
00:42:39.000 --> 00:42:42.000
sit there and try different different rates of injection. We observed how long

472
00:42:42.000 --> 00:42:48.000
it takes to

473
00:42:48.000 --> 00:42:51.000
come in contact with an observation well, so when we install the barrier,

474
00:42:51.000 --> 00:42:54.000
there's always an observation well close by so that we can actually inject near

475
00:42:54.000 --> 00:42:59.000
that well and verify that yes, this is the

476
00:42:59.000 --> 00:43:04.000
correct gradient of influence. And yes, this is the injection rate we need.

477
00:43:04.000 --> 00:43:07.000
>> Okay. Okay. And I do have just a couple of questions along those lines. They

478
00:43:07.000 --> 00:43:17.000
wondered,

479
00:43:17.000 --> 00:43:19.000
one of the attendees wonder did you see the injection pressure increasing

480
00:43:19.000 --> 00:43:22.000
during that injection., And they were wondering if it was possible to conduct

481
00:43:22.000 --> 00:43:25.000
multiple injections in the same injection well if you needed?

482
00:43:25.000 --> 00:43:33.000
>> So, yes. When we inject towards the end of the volume

483
00:43:33.000 --> 00:43:36.000
, the total volume that was prescribed for that well, are injection rates would

484
00:43:36.000 --> 00:43:39.000
slow and are pressure would increase.

485
00:43:39.000 --> 00:43:46.000
>> And we did a second deck location

486
00:43:46.000 --> 00:43:49.000
application and we were able to reinjected most of the wealth. Some of the

487
00:43:49.000 --> 00:43:53.000
wells we could not reinjected in.

488
00:43:53.000 --> 00:43:56.000
>> Okay, to confirm, the plume stop destroys PCE? And if not, they were

489
00:43:56.000 --> 00:43:59.000
wondering if there was a concern that the PCE would come back and be an issue

490
00:43:59.000 --> 00:44:02.000
for groundwater in the future questioner

491
00:44:02.000 --> 00:44:10.000
>> Yeah, why did you handle that was?

492
00:44:10.000 --> 00:44:15.000
>> Plume stop itself does not have a destructive component. For this particular

493
00:44:15.000 --> 00:44:18.000
site, and I will let the EA comment on that, there was national continuation

494
00:44:18.000 --> 00:44:24.000
that was basically observed. I think

495
00:44:24.000 --> 00:44:31.000
Jay alluded to that earlier, about that, so I think we had a good understanding

496
00:44:31.000 --> 00:44:39.000
of what the K rates, or the half-lives of the constituents were

497
00:44:39.000 --> 00:44:42.000
at the site. So we used that to our advantage. Not every site is like that. So,

498
00:44:42.000 --> 00:44:45.000
that's one of the aspects or parameters that we really tracked closely with the

499
00:44:45.000 --> 00:44:53.000
modeling that's done for these designs.

500
00:44:53.000 --> 00:45:09.000
>> Okay. I have a couple of other questions, and one of the attendees

501
00:45:09.000 --> 00:45:12.000
I take it back in my seat two of them asking about models or simulations. So,

502
00:45:12.000 --> 00:45:15.000
specifically they wondered what you might've done in the way of a model or

503
00:45:15.000 --> 00:45:18.000
simulation to confirm that the PRP would work, and what I think they are getting

504
00:45:18.000 --> 00:45:20.000
at is to understand some surface hydrogeology, so what kind of modeling did you

505
00:45:20.000 --> 00:45:23.000
do to understand subsurface, if any?

506
00:45:23.000 --> 00:45:26.000
>> You want to take that Carlos questioner

507
00:45:26.000 --> 00:45:29.000
>> Well, I'll be happy to answer that, but I think the question is more about

508
00:45:29.000 --> 00:45:33.000
any type of

509
00:45:33.000 --> 00:45:39.000
3-D modeling on the hydrogeology side of the EA design. I mean this model that

510
00:45:39.000 --> 00:45:49.000
we use is really a tool for evaluating

511
00:45:49.000 --> 00:45:51.000
the contaminants as we talked about, the contaminant mass flux or not, but it's

512
00:45:51.000 --> 00:45:54.000
not necessarily addressing distribution of the contaminant mass with the aquifer

513
00:45:54.000 --> 00:46:00.000
on a 3-D level.

514
00:46:00.000 --> 00:46:05.000
>> Right, and with respect to that, I mean, if you go back and look at some of

515
00:46:05.000 --> 00:46:11.000
the original plume maps, between the supply wells, and are monitoring wells, you

516
00:46:11.000 --> 00:46:15.000
know, we had really good control on the balance

517
00:46:15.000 --> 00:46:21.000
of the plume in general. And

518
00:46:21.000 --> 00:46:27.000
what's interesting about this Cretaceous aquifers in Texas is that they argue

519
00:46:27.000 --> 00:46:31.000
no, they are to pick only completed with fully penetrating wells. And they are

520
00:46:31.000 --> 00:46:38.000
not that thick of aquifers

521
00:46:38.000 --> 00:46:41.000
, so the supply wells actually make pretty representative monitoring wells,

522
00:46:41.000 --> 00:46:47.000
which is often not the case with

523
00:46:47.000 --> 00:47:04.000
pluming, but in the case of these aquifers in Texas, we use them

524
00:47:04.000 --> 00:47:07.000
routinely as monitoring wells, because they are quite representative. Okay,

525
00:47:07.000 --> 00:47:10.000
excellent. I think we have time for just a few more questions before we begin

526
00:47:10.000 --> 00:47:13.000
wrapping things up. So we did have a design question. I take that back, I've got

527
00:47:13.000 --> 00:47:16.000
to. Someone wanted to know why you selected the 300 foot length for your

528
00:47:16.000 --> 00:47:19.000
barrier?

529
00:47:19.000 --> 00:47:28.000
>> So, the 300 foot length for the barrier was because that

530
00:47:28.000 --> 00:47:33.000
if I go back and look at the figure up right now, the 300 foot length of the

531
00:47:33.000 --> 00:47:37.000
barrier covered protecting the wells that were above the MCL or

532
00:47:37.000 --> 00:47:43.000
that could be above the MCL. We had

533
00:47:43.000 --> 00:47:48.000
no contamination here by the MCL's or by these wells here, so this length here

534
00:47:48.000 --> 00:47:54.000
just to be protective of this area, that's where the focus of the contamination

535
00:47:54.000 --> 00:47:57.000
was going through . We later added this additional barrier. We wanted to be

536
00:47:57.000 --> 00:48:02.000
further

537
00:48:02.000 --> 00:48:04.000
protective, but at first, we just did the 300 feet. We also wanted to see how

538
00:48:04.000 --> 00:48:10.000
effective the barrier was.

539
00:48:10.000 --> 00:48:14.000
This was 2017 when plume stop was first kind of coming out.

540
00:48:14.000 --> 00:48:19.000
>> Okay, and that you had a great

541
00:48:19.000 --> 00:48:21.000
figure earlier in the presentation, Terry, that showed the barrier was like

542
00:48:21.000 --> 00:48:25.000
this arced

543
00:48:25.000 --> 00:48:28.000
, hyphenated line, and one of the attendees noted that it looks like you are

544
00:48:28.000 --> 00:48:39.000
installing the P and

545
00:48:39.000 --> 00:48:42.000
PRB under the buildings and foundations, and maybe if you could talk a little

546
00:48:42.000 --> 00:48:45.000
bit about how to get it under the buildings if that was the case effectively,

547
00:48:45.000 --> 00:48:48.000
under their foundations questioner

548
00:48:48.000 --> 00:48:50.000
>> So are you talking about this drawing, this figure?

549
00:48:50.000 --> 00:48:55.000
>> I believe -- I'm still waiting to get back to the one that they are

550
00:48:55.000 --> 00:49:00.000
referencing. >> This was for horizontal SVE wells

551
00:49:00.000 --> 00:49:04.000
, so those were beneath the chemical plant.

552
00:49:04.000 --> 00:49:06.000
>> Okay, those are horizontal wells, but nothing with the --

553
00:49:06.000 --> 00:49:09.000
[ Indiscernible - overlapping Speakers ]

554
00:49:09.000 --> 00:49:13.000
>> Nothing with the PRB.

555
00:49:13.000 --> 00:49:16.000
>> No. Those were just vertical. Okay. All right. And then, let's try to sneak

556
00:49:16.000 --> 00:49:23.000
in one more question here.

557
00:49:23.000 --> 00:49:27.000
I think you hit on this earlier, but just to confirm, the 12 foot interval for

558
00:49:27.000 --> 00:49:35.000
those injection wells, it was selected, but those

559
00:49:35.000 --> 00:49:39.000
injection rates were bearing dramatically along the barrier. I just wanted to

560
00:49:39.000 --> 00:49:42.000
know what kind of groundwater testing you may have done before your injection?

561
00:49:42.000 --> 00:49:44.000
Specifically do you know if that injection rate is appropriate for the influence

562
00:49:44.000 --> 00:49:50.000
and the list areas that have lower injection rates?

563
00:49:50.000 --> 00:50:00.000
>> We did the performance testing at the beginning with

564
00:50:00.000 --> 00:50:02.000
the observation model on that first barrier. Subsequent barriers that we

565
00:50:02.000 --> 00:50:06.000
installed had more observation wells along the barrier alignment so that we can

566
00:50:06.000 --> 00:50:09.000
test different portions of it.

567
00:50:09.000 --> 00:50:12.000
>> Okay.

568
00:50:12.000 --> 00:50:16.000
>> Just real quick, so I'll add, Terry, I think she mentioned yeah, earlier on

569
00:50:16.000 --> 00:50:23.000
the application the original design was based

570
00:50:23.000 --> 00:50:30.000
on emulsified vegetable oil well spacing. In between that

571
00:50:30.000 --> 00:50:33.000
we had a preliminary design and our final design we had done a pilot test

572
00:50:33.000 --> 00:50:37.000
application at a different site using

573
00:50:37.000 --> 00:50:42.000
them stop, but we were in valuing the gradients of influence as a result of

574
00:50:42.000 --> 00:50:54.000
that we came back to this design, and reassessed the

575
00:50:54.000 --> 00:50:57.000
ROIs, and we reduced the spacing and we use that information to reduce the

576
00:50:57.000 --> 00:51:00.000
spacing to 12 1/2 feet. And then post application, with additional information,

577
00:51:00.000 --> 00:51:02.000
we then, you know, closed this pacing slightly to help with the application

578
00:51:02.000 --> 00:51:05.000
volumes we had done.

579
00:51:05.000 --> 00:51:10.000
>> And one other thing I'd like to add, write to that question is, because of

580
00:51:10.000 --> 00:51:15.000
the differential cementation, we experienced you know, different injection,

581
00:51:15.000 --> 00:51:18.000
different injection rates. In almost fortuitously, where we had difficultly

582
00:51:18.000 --> 00:51:27.000
injecting was lower

583
00:51:27.000 --> 00:51:30.000
permeability due to the cementation. So those are not the high mass flux zones

584
00:51:30.000 --> 00:51:34.000
anyhow. Where we were able to inject in these unit, Cretaceous aquifers and

585
00:51:34.000 --> 00:51:38.000
Texas, we've done several of them. Where you are able to inject is where your

586
00:51:38.000 --> 00:51:44.000
mass flux is going anyhow. One of the concerns we have assigned

587
00:51:44.000 --> 00:51:50.000
about some of the cemented zones is will we see a back diffusion issue out of

588
00:51:50.000 --> 00:51:53.000
some of the zones in that they are not the high mass flux zones? But we could

589
00:51:53.000 --> 00:51:58.000
diffuse flux, you know, contaminants into them what would lead out over time.

590
00:51:58.000 --> 00:52:04.000
So, it's just the hand we're dealt, it's also what makes bench

591
00:52:04.000 --> 00:52:08.000
scale testing difficult, because you know, what material you are going to test,

592
00:52:08.000 --> 00:52:11.000
and can you get core, and can you even have a representative sample for the

593
00:52:11.000 --> 00:52:18.000
bench test is complicated?

594
00:52:18.000 --> 00:52:21.000
We dural these air rotary and what we get back is sand. They are not strongly

595
00:52:21.000 --> 00:52:25.000
cemented, but they are cemented and they do have a fracture point.

596
00:52:25.000 --> 00:52:32.000
>> All right. Well, we are nearing our scheduled in time, so I think I'm going

597
00:52:32.000 --> 00:52:37.000
to draw a close to our formal Q&A. Terry, and Jay, and Carlos, I want to thank

598
00:52:37.000 --> 00:52:40.000
each of you for taking time to share that presentation with us. And, I'm going

599
00:52:40.000 --> 00:52:47.000
to walk through just a few final reminders

600
00:52:47.000 --> 00:52:50.000
before we close things out today. So, I'm going to go ahead and turn on some

601
00:52:50.000 --> 00:52:53.000
final instructions here on the screen. And go ahead and walk through these

602
00:52:53.000 --> 00:52:59.000
closeout messages.

603
00:52:59.000 --> 00:53:03.000
>> For the first thing I will do again, thank our presenters who took time to

604
00:53:03.000 --> 00:53:12.000
share their technical story today, and I want to thank the

605
00:53:12.000 --> 00:53:15.000
over 150 people who joined us for today's live session, if you are connecting

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00:53:15.000 --> 00:53:19.000
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607
00:53:19.000 --> 00:53:22.000
in just a moment. But I will remind everybody that this is part of a ongoing

608
00:53:22.000 --> 00:53:25.000
webinar session. So we have session number one main delivery and we will carry

609
00:53:25.000 --> 00:53:29.000
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610
00:53:29.000 --> 00:53:34.000
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00:53:40.000 --> 00:53:44.000
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613
00:53:44.000 --> 00:53:48.000
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614
00:53:48.000 --> 00:53:50.000
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