Rocky Flats Site, Colorado, Tour – East Trenches Plume Treatment System (ETPTS)

We're at the East Trenches Plume Treatment System, or ETPTS. This is one of the four original, now three remaining, groundwater treatment systems. We collapsed from four to three because the ETPTS now treats the groundwater that is collected for this particular system as well as for what used to be the Moundsite Plume Treatment System, or MSPTS. Now the groundwater collected from the Moundsite Plume is piped over to be treated by this treatment system because it's just a short way up the valley and it's the same family of chlorinated solvent contaminants that needs to be treated and it's amenable to the same treatment methods. The original treatment methods at the Mound and the East Trenches systems was granular zero-valent iron, or ZVI, and the groundwater contaminated with these chlorinated solvents would be collected and passed through the ZVI and in the contact between the iron and the chlorinated solvents there were chemical reactions that rendered the chlorinated, they dechlorinated the solvents and rendered them innocuous byproducts that were then discharged. The problem was that at closure we had done some increased remedial work that tied into these treatment systems adding flow and the treatment systems were no longer able to keep up with the higher flow rates at least at the Mound Site Plume Treatment System and secondly our closure agreement, the RFLMA, Rocky Flats Legacy Agreement, has very strict requirements for the treated water from these systems, the effluent, and the original design systems were not able to maintain that level of treatment. So we tested several different optional approaches. Air stripping is the one we landed on and air stripping is a very old technology but it had become more amenable to a compact size that is appropriate for our treatment systems because we get so little groundwater to treat and is also, they had been collapsed to the point where the energy needed to run them was reduced. Again, Rocky Flats is completely off the grid. We have no line power so if we need that energy we need an electrical component to supply it and that is located farther up the valley. That connex or cargo container has lithium iron phosphate batteries inside and it has a large number of solar panels mounted to it to charge those batteries. So the air stripper runs off the battery power, the solar panels charge the batteries, so it's a wonderfully efficient system. I mentioned not very much water. Right now, this is July, things are drying out. This treatment system's 24-hour average now is about 1.4 to 1.5 gallons per minute. We treat it and it treats in batch so what happens is it collects the groundwater for overnight until the next morning and assuming it has sufficient electrical power, which it always does, and enough water to treat, then it'll go on ahead and process that batch and once it's finished processing that batch it just stops treating. It continues accumulating groundwater until the next day or if the water is accumulating fast enough it'll run a second batch. That hasn't happened but it is a possibility. In a day, right now, we're running about 2,400 to 2,500 gallons per day so that shows you there's not very much groundwater being collected or treated by this and to put it in perspective, the 1.4, 1.5 gallons per minute, you have five of those and you might have a garden hose on full blast, five or six, seven of those, so we're not talking a lot of water. But the levels of contaminants, the chlorinated solvents, are such that they are well above our standard at Rocky Flats in the rifflema and so we need to treat this water and discharge treated groundwater that meets those standards so that the South Walnut Creek surface water is not adversely impacted by those contaminants. The way we do that again is through air stripping and the process of air stripping basically is enhancing the contact of air with water so that these volatile organic compounds, VOCs, the chlorinated solvents, will move into the air, the air fraction, and be stripped out of the water. It's like when you fill up your car with gas, if you have a gas-powered car, you can smell gasoline right away. That's because it is a volatile organic compound, a VOC. It very readily evaporates, moves into the gas phase, and that's why you can smell it. The same kind of principle applies to these chlorinated solvents. They are dissolved in the groundwater, but when so much air is forced through the groundwater, as in this air stripper, it does what the name implies. It strips those organics, the VOCs, the volatile organics, out of the liquid phase into the gas phase and it exits out the pipe that you can see on the side of that little building. The conceptual site model, as I have described, is such that the groundwater that's in the Rocky Flats alluvium, up gradient, uphill of us, is flowing down into the South Walnut Creek drainage. However, we have a buried pipeline, a perforated pipeline that collects this contaminated groundwater before it reaches the surface water. And that is how we collect the groundwater and route it to this air stripper for treatment. The Moundsite Plume Treatment System is no more, but the collection infrastructure remains, and it's now called the Moundsite Plume Collection System, MSPCS, and what that does, it's farther up the valley, it collects the groundwater through a similar design, a perforated drain that collects it and routes it, in this case, to a vault from which it is pumped through a pipe to come down here and eventually be treated at this treatment facility. So if we come over here, we can look at the air stripper a little more closely in some of the infrastructure that supports it. This is called a stacked tray air stripper because there's a sequence of trays inside that glass fronted box, and each of those trays is perforated, it has little holes, it's not like a screen mesh, it's like a metal tray, but with a tight network of holes of a very specific diameter, a size, so that enough air comes through to meet the design, and so the air is forced up through the trays, the air going against the flow of water acts to strip those organics out of the liquid, the dissolved liquid phase. And here we have two of our original treatment cells, the components inside the railings with the yellow and silver patch covers, those used to be treatment cells filled with ZVI or zero valent iron. They are now no longer filled with that because we no longer use that as a treatment mechanism, but the one on the far side is used to accumulate the untreated water from the collection point, and then as I mentioned, every day that water will be pumped through the air stripper and it'll be discharged to this second tank, and from this tank it is then discharged to the subsurface, and that's the way the ETPTS works. One notable thing about this, the original design of the ETPTS really never met the RIFLEMA requirements for treatment. Even when we replaced the ZVI and it was brand new and fresh, it wouldn't meet the standards under the RIFLEMA, and this was problematic first because we were required to meet the standards, second because every time we replaced the media, it was three semi-loads of ZVI that we would bring down from Detroit, Michigan, and in the meantime we had to get the ZVI out of these two cells, and by the time we were able to make that exchange, the granular iron was no longer granular, it was cemented together into a solid block of rust, and so you had to chip it out of these tanks in order to remove it and replace it with the fresh granular material, and that wasn't very easy because the tanks are made out of plastic, but you couldn't crack or chip the plastic because they needed to remain, you know, watertight so that they would contain the water, so what that required was a small mini-excavator with a hammer attachment to break up the ZVI, the solid solidified ZVI very carefully, but break it up and then remove it, and these things are eight to ten feet deep, and at some point the mini-ex could no longer just bucket it out, instead the excavator had to de-energize, turn it off, we'd have to lower a ladder into each cell, have guys go down in and hand load the bucket and then climb back out, and then they could turn the mini-ex back on to remove the waste. All a safety hazard, a big expense, a big time demand, and needless to say a big carbon footprint since we're bringing the ZVI from Detroit to here, and we were doing it every three to four years for this particular system, so and then that spent ZVI would be sampled and it would be dispositioned as the data would dictate as far as how it would be disposed of, so that was not a very a very efficient effective way to meet our requirements, so going to this ETPTS both made it simpler and safer and much more effective. Now we consistently meet all of our required standards for the treated water, as I said the ZVI was removed from the Moundsite plume treatment system also, so we no longer have to replace that ZVI, and so all in all we have both collapsed two into one treatment system and made the treatment much more effective and much less environmentally impactful in terms of how we go about the treatment and the change, and much safer. This is a very safe system, it's been essentially glitch free since we put it in, we do have to do maintenance on it, but it's minimal compared to the old days. One thing I wanted to mention while we're here is something in the background. Gray culvert is part of the pre-closure operational bee pond bypass pipeline, and we had five impoundments on South Walnut Creek, now there's only one, the terminal pond B5, but this bypass allowed ponds to be circumvented and water to be routed around them and farther down or routed into a particular pond or all ponds, however they deemed necessary. And regarding the term volatile organic compounds and gas phase, this does not mean that these compounds are flammable, it's just that they volatilize, they evaporate easily from the liquid phase to a vapor slash gas, gaseous phase like oxygen, air, that kind of a thing, not a flammable connotation at all. The reason that there are VOCs or chlorinated solvents in the groundwater is because chlorinated solvents were a very effective means of machining the, well used in the machinery process. Again, Rocky Flats was essentially an extremely high-tech machine shop and metallurgical facility, and to machine these parts to such high tolerances required a lot of equipment that needed to be cooled and lubricated and kept clean, and these chlorinated solvents served as good cleansers as well as coolants for say lathing and that kind of drill press and that kind of thing. So they used a lot of compounds such as carbon tetrachloride and trichloroethene and tetrachloroethene, things that are used in machine shops and dry cleaning facilities and other uses such as that. The chlorinated solvents here are here because some of those solvents were disposed in earthen trenches, and this was a standard practice back in the 50s, 60s, 70s where they would dig a trench and pour the spent solvents into the trench and close it up, because back then it's not special to Rocky Flats, it was nationwide, worldwide. The expectation was that this material would be cleaned up by Mother Nature, it would go away, and there would be no harm. We now know differently, we now know that it impacts the groundwater and the groundwater is then potentially going to impact at Rocky Flats the surface water quality and then become a threat to the ecological resources. So we've learned a lot since then and that's why number one there are chlorinated solvents present at Rocky Flats and number two why we want to treat them and why they're in this bloom.