Thursday, July 30, 2009

Landfill Pioneer

I've been thinking of doing percolation tests here at the landfill for a long time now. We've been thinking of installing a drainfield in the active cell and running condensate or leachate into it to help with gas production. In order to properly design a drainfield, you need to know the percolation rate of the soil where the drainfield is going to be installed. I couldn't find anywhere where someone had done a perc test in garbage, so I think I'm the first one to ever do least that's what I'm telling myself. First I had to dig the holes.

Esther and I started digging the holes, but only got 16 of the 36 inches deep after 1 1/2 hours of digging with a shovel, post hole digger, and breaker bar. That's when I decided to use the backhoe. It made the holes bigger than I wanted, but was a lot faster and easier, especially since I did three holes. Garbage sucks to dig through!
We then had to keep water in the holes for a couple of hours to saturate the soil. This proved to be difficult. I used our water truck to fill the holes with water, since that would be the most efficient, especially for the size of the hole. I started spraying, hoping that the hole would fill up quickly but that's not what happened. Even with the good compaction we are getting, there is still a large amount of pore space in garbage that water just moves right through it. After five minutes of filling with the fire hose from the water truck, the hole only filled in six inches. I decided I wasn't going to be able to fill the holes as much as I wanted. I filled the hole to about 10 inches and moved on to the next hole. I filled the next hole, again only to about ten inches, and checked on the first hole. The water was already gone. I looked at the second hole that I had just barely filled to ten inches and the water in that one was already gone. I had a feeling it was going to be quite difficult to keep the water level up for four hours.

The next day I went back out to run the actual perc test. Now in a perc test, after the soil (or in this case, the garbage) has been saturated you fill the hole with water and measure the time it takes for the water to drop i.e. minutes per inch. So I filled the hole with water and before I could fill the next hole, the water level, as it had before, dropped completely. I concluded that garbage has a really low (or in other words, a really fast) perc rate.

I decided to switch gears and try running a perc test in the native soil. I dug two holes in the native soil and started saturating them.

I'm pretty sure these tests are going to be much different. I saturated the holes but didn't have time to run the tests the next day, (I'll have to start over) but came back four days later to see that one of the holes still had water in it. I think this soil is a little less permeable than the garbage.

No comments:

Post a Comment