Shallow drive well stuck at 13 feet

Long story, but hopefully it'll make some sense. I'm trying to install a shallow well in the backyard. I'm told that the water table in the area should be approximately 15-20 feet. This is located in Oregon.

First, a description of the soil. The top foot or so of the soil is hard clay. In the summer it's rock hard. In the winter (or with a liberal application of the garden hose), it's a gooey sticky mess. Below this clay later we get into a layer of fine gravel. It looks a lot like 3/4-minus or 1/2-minus that you might buy from the local quarry. This fine gravel is generally moist. You can dig it out, and it'll be wet. A little water might slowly seep into the hole, but it doesn't amount to much.

I started by driving the well approximately 5 feet. I measured the water level and there was a foot or two of dirty water in the pipe.

I drove it another couple of feet and checked it again, and still had about the same amount of water in the pipe. I tried flushing the garden hose into the pipe and found that the pipe is holding water (it's not draining out). So I figured I must be in some impermiable layer.

I keep working at it, and end up getting to about 13 feet down and it's getting progressively harder to drive the pipe. About 30 minutes of pounding for maybe an inch of travel. I'm using one of those steel post drivers from the hardware store (a round tube with a couple handles on it).

I figure maybe I'm just not getting enough weight to drive it, so I go to the local rental store and pick up a tripod mounted driver operated by a rope and pulley. It's very heavy, enough that it takes two of us to lift the driver onto the pipe. It easily weighs four times as much as my original driver, and has a longer sleeve so I can get more velocity on it. Even with this behemoth of a post driver, I'm out there getting about an inch of travel in 1hr+ of time. It gets so bad that it's no longer moving at all.

I figure I hit a rock, so I grab another sand point, pick another spot and start over. Unsurprisingly, pretty much the same thing happens. I drive it about to the point when it's no longer moving again, the time limit is up on the rental driver, so I give up and take it back to the rental store.

I get to thinking about the clay that was one the surface that was very hard when dry but soft and gooey when wet. So I rig up a fitting to attach the garden hose to the well, and let it sit there and force water into the pipe for about half an hour. I remove the fitting, look into the pipe, and it's still holding water (not draining out), so I figure it probably didn't do anything. I throw the drive cap on, whack on it for a little while with the small post driver, and observe that it clearly goes down another 3" or so into the ground. It's late, and I'm tired, so I call it a day and vow to resume the project during the week.

So, the questions...

1) Am I right that I hit some kind of clay layer? I haven't read anything about needing to soak down the well while driving. I really just tried it on a whim thinking that *maybe* it would do some good. Is it a valid strategy?

2) What is this "moist gravel layer" that I encountered a foot under the surface? I can't believe it's the water table, because there's just not enough water there. Is it possible for surface water to be getting trapped above an impermeable layer of clay?

3) Any suggestions on how to drive this point deeper? or am I just wasting my time?

Thanks

I have similar soil here in the midwest, and my layer of clay a few feet down is about fifteen feet thick. My guess is that pressurizing your pipe with water so you might be able to continue driving it a few inches at a time might work, but drilling would be much easier.

leejosepho said:

I have similar soil here in the midwest, and my layer of clay a few feet down is about fifteen feet thick. My guess is that pressurizing your pipe with water so you might be able to continue driving it a few inches at a time might work, but drilling would be much easier.

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I gave it 4 hours of soaking, and then hit it with the driver some more and this time it wouldn't budge. Not even half an inch. So I'm guessing it has in fact hit rock or otherwise something so darned hard that it's not going to go through it, regardless of my efforts.

What's the best way to pull the sand point back out? The point itself is only about 10 feet below ground level, but whatever it's wedged into has so thoroughly got it stuck that it's impossible to even turn the pipe short of adding a 5ft extension to my pipe wrench (something which I assume will eventually break a coupling, etc). I'd like to at least pull it and take a look at things and try to figure out what is up, for my own piece of mind if nothing else.

Finally, I measured the water level in the pipe (forcing water into the well with the garden hose has freed up enough of a channel that the pipe can now freely drain). It's holding steady at about 2ft below the surface. The layer of muck that the sandpoint is stuck in must be somewhere between 6-10 feet below the surface. That doesn't give me much of a usable window to work with, but is it possible that I simply went too deep and pulling the point up a couple of feet would be a viable well?

Thank,
Scott

smbaker said:

What's the best way to pull the sand point back out?

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I have never pulled one, but I have heard people sometimes use chain hoists or jacks. The problem there, however, would be to come up with the right kind of rigging.

smbaker said:

... is it possible that I simply went too deep and pulling the point up a couple of feet would be a viable well?

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From things I have read here on this board, I would doubt you would have a viable well. But, you could put a pitcher pump on the pipe and try it a bit to see what happens.