Got tho thinking about landfills. I have read more than once that each day the pile of trash is covered with a foot of soil to keep the trash from blowing around etc. Where does all that dirt come from? And do they really cover the whole pile very day?
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Typically, the dirt came from the pit they are filling, or the one next to it, that they will fill next.
>> Where does all that dirt come from?
Out of the hole they dig to put the trash in.
>> And do they really cover the whole pile very day?
Yes, but keep in mind that one day's trash isn't spread out over the entire dump surface. They concentrate in whatever area results in their target layer depth, so enough dirt to cover one day's trash is not all that much, relative to the size of the whole landfill.
My Sister is a biologist responsible for a landfill serving about 400 000 people. When you dump, they backfill your load so fast the seagulls don't have time to land. There is a Cat almost nudging your bumper. While the surface looks good ( no doubt they will be building on it in 50 years), the real problems are leachate - the liquid goo that seeps into the water table, and trying to separate out hazardous waste before it gets buried.
I'm not so sure they'll be routinely building on old landfills in 50 yrs, but they'll definitely be strip mining them for all the stuff that we threw away. Don't think of them as "landfills" think of them as temporary storage piles for our future building materials.
around here, part of the required design is for a layer of some kind of imperviuous sort of clay on the bottom shaped like a dish to prevent leaching out. ExpensiveSo we send our trash off to the incinerator where they use gas jets and make electricity out of it.I don't know what happens to the crud that doesn't burn.
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here what will magnetically sort out gets recycled and the rest goes to land fill...Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
around here you are responsible for that landfill 100 years after it close. you better have some offspring to run the company.
Worked on several solid-waste landfills. You excavate the area, walk-in about 2 feet of clay, excavate a series of drainage swales, lay in pipe, cover with gravel, and put a 30mil impervious liner, with more gravel over that. The swales can connect to a pump, or a below-grade system to a field to remove the water. Stacks are installed to vent methane as it builds up over the years. Generally, the waste is walked-down after every lift, and only covered after the pit has been filled to it's design limit, unless local code requires intermediate cover.
Stinky work. Walked on an old pit one time, and the ground gave way, and I went into nothing but decomposed horse and cattle carcases...
FastEddie,
It really depends a lot on who's running the landfill. Most are going to be future methane generator sites where the methane from decomposing stuff fires generators which provide electricity.. To do that they need to spread a membraine over the materials to capture it and use it later. they need to cushion the buried tuff so it won't poke holes in the membraine, hence the dirt.. Dirt does other stuff as well,...
Once methane production ceases, they peel back the membraine and remove metals and other recycles, after that the land is recaimed and will at some future point be sold as housing or other land use..
My firm has worked with Frenchy's old company on quite a few landfill projects. Like he said, a large generator (or a number of generators) are parked on top of the landfill, and they run off the methane. A fair amount of electricity can be generated this way, we did some projects that put out 4 megawatts or more. In some cases, where generators aren't in the budget, a flare is set up to burn off the methane.
A number of leachate wells are installed to pump the water from underneath the landfill. Depending on the situation, the water may go through a treatment plant where chemicals are added, or it may just go through some settling ponds to remove contaminants. Working on these projects I got a lot of practice calculating voltage drops - when you have to run power for thousands of feet to all those wells from the main electrical service, the wire can get pretty big. :-)
Your landfills sound a bit more sophisticated than ours (well maybe not the animal carcasses). The leachate that escapes the site is caught by a perimeter drains and pumped into the regional sewer system. Problem is, our sewage flows straight into the Strait of Juan de Fuca without even primary treatment.
Locally, you run across small industrial landfills all the time. The area hasn't been settled for that long, but the logging and mining industry did whatever they wanted and the trees grew over everything fast.
Used to work for a company that conducted environmental consultation during gas station remodeling/tank upgrades. Any contaminated soil that was removed was sent to an incinerator where all the petroleum was cooked out of it, then some went to an asphault plant to be mixed in and the rest was used to cover a land fill. A guy who was the field representative for the petroleum company (has been there for over 20 years) said he remembers trucking the soil to Maine many years ago, before strict environmental regulations, and farmers would spread the soil in fields really thin and mix it with animal waste.