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From what I hear this story is not over. The last I heard DEP had another driller in taking samples. I wanted to post today because I actually met with one of our sludge producers this week for the first time at their facility, and I have a better understanding of where it comes from, how it is solidified, and why certain materials have to be used. This will be kind of a long and boring post, but for anyone wondering what sludge actually is I will try and explain it. Wastewater treatment sludge is easy to visualize, it's just whatever settles to the bottom of a treatment pond, and it makes up about 40% of our sludge intake. The rest is classified as "industrial sludge", so in my mind it was coming from the back end of a plant as the sludge I see. I asked our hauler if he would give me a tour of the facility, because we have to work with each other on haul times so I'm not bombarded with more than I can handle in a short period of time. Sometimes this puts our hauler in a bind, so I wanted to see what he was up against. I was surprised to learn that his facility isn't producing the sludge, he is taking liquid waste from all kinds of industry, solidifying it, then sending it to the landfill. When I say liquid waste, I mean almost any liquid you can think of. Oil, ammonia, shampoo, milk, all different kinds of liquid chemicals. He said almost every manufacturing process produces liquid waste on some level. His facility receives these liquids and what can be recycled, like oil, is recycled. All other liquids are hauled in tankers, or in 50-100 gallon totes. These liquids are dumped into a "solidification pit", a concrete lined pit about 15ftx15ftx10ft deep. The next step is to add a binding agent, and this is where the dangers of sludge in a landfill begin. Sawdust is commonly used, and I love it, but the problem with using sawdust is it doesn't totally bind the liquid. If only sawdust was used, the trucks would leak from the facility all the way to the landfill, about 45 miles away, so other binding agents have to be added. One option is a cottony looking material that soaks up the liquids, and that works for me because the liquid is squeezed back out in the landfill by the weight of the equipment and the weight of the trash stacked on top of it. Picture it like a saturated sponge. The problem there is you still risk trucks leaking en route, so another agent they use is binding polymers, basically powders that lock the liquids. This is the stuff that makes sludge so hard to handle, so dangerous if it isn't mixed properly. The very thing that makes it safe to haul is what makes it dangerous in a landfill. It's not like a sponge, it doesn't release the water. It never dries and stabilizes, and if too much is placed in one area it makes an impervious layer that will trap other liquids either above or under that layer, creating those invisible underground ponds that I've described before. This is why I want the story of Greentree to come out. If it is proven that sludge was responsible for that collapse, the waste industry needs to take a long look at what it is, and what it is doing to us. Liquid waste will always be generated, and it has to go somewhere. Modern landfills are the best option we have at this time, but the workers in those landfills have to be protected. When "wet waste" studies are done, they are done by engineers, and those results are shared with upper management. The field operators are not brought in to the discussion. Things that look good on paper don't necessarily translate to good practice in the field. One of my engineers came to me after one of those studies, excited to tell me they had proven that the "moisture retention capabilities" of the polymers were very high. To the people watching the bottom line, what that means is less leachate generation, less liquid at the bottom of the landfill that has to be hauled off and treated. An engineer doesn't think about what this waste that never dries does to the surfaces we work on every day, and how those initial savings in leachate generation turn into expense exponentially for years and years after the waste is dumped. You have to dig up bad areas and repair them, you have slides that if not repaired turn into exactly what happened at Greentree. You have odor issues because of gas migration, and lawsuits have been settled for millions of dollars with neighboring communities. The biggest issue of all is the instability it causes, and the dangerous conditions employees have to work in if it is not handled properly. There needs to be a national discussion about how this liquid waste can be safely disposed of. You can't dump free liquids in a landfill, so it will always have to be solidified in some fashion. I want the industry, regardless of the company you work for, to take a look at this issue and make common sense decisions that include input from the people that actually have to handle this material. It can't be fixed by a spreadsheet. If the Greentree collapse doesn't get everyone's attention, then nothing will. If it is swept under the rug and disappears quietly, it will happen again