Plan to help a friend plug a dug well (approx. 4 ft dia) that is in his basement. It's about 20' deep with about 14' of water in it. He figured he'd pump it down and leave some in the well. Dump in the required 12" layer of bentonite chips at the bottom, add 10' of fill sand, another required layer of chips, etc. per the recommended method. Question: How much does he need to pump out? The bentonite will sink and expand later, but he doesn't want the sand to be "waterlogged" and end up being quicksand. His first thought is to pump down to 1-2 ft (if he can) or can he leave more water in?
Sounds like somewhere near my old stomping grounds.
Even though Bentonite does a good job of plugging holes, I would think the sand that he leaves is going to end up being saturated with water sooner or later. Nothing plugs a hole that well. You could just put in the Bentonite; let it do it's expanding thing, then add the next layer of sand. No need to take out the water unless he just wants to see what's going on. Remember the Bentonite won't work unless it's in water.
bob,
Job's done. Everything went pretty well (pun intended). We pumped down and left a couple of feet of water (for the bentonite to work). It was crystal clear coming out of the pump. Dumped (in a scattering motion) the 1st layer of bentonite chips with enough material to get 1 foot of coverage at the bottom. Measured with a tape and thickness was pretty consistent considering we were dumping it from bags some 20 ft above. Measured the water level after dump and it came up 1 foot as another indication of adequate depth of chips. Put in 9 ft sand and when we were ready for the 2nd level of bentonite we pumped out some more water to leave just about 1 foot above the sand. Another foot of bentonite chips left just a few "dry" chips showing. Final fill of sand and we're letting it settle some before capping it. We figured the sand would get waterlogged but our concern was that we would have to deal with all the water displaced by the fill eventually and it was better to deal with clean water than gritty, muddy water. Only problem we had was that we didn't have a proper intake hose on the trash pump and at the lower depths, the plastic hose we were using collapsed due to the suction. It just slowed us down a little. Good excuse to go out and buy a proper suction hose with quick disconnect fittings.
Jim,
Yeah, water is something we kind of take for granted up here in the Midwest. Although, as I've said in other posts, you can have a house in some locations on the shores of Lake Huron (Great Lake) with 20% of the world's fresh water literally lapping at your doorstep and not be able to get water from a drilled well. I looked at some cottages for sale up in the "Thumb" area of Michigan where they had to truck in water. Wierd stuff. Since you brought it up, how deep do you have to drill for water in your area of AZ? I know that water has always been a contentious issue for landowners in the West and that "water rights" mean an awful lot.
I live in area of fractual rock. Wells can vary in depth greatly and be only a 100 ft apart. My wells are about 280 and 300. But a neighbor 1 mile away has four 400ft holes that make about 2 gallons a min. Yet the place right across the road from him has a 200ft well that makes 25 gal a min. It is not unusal to go 600ft. Water rights a vary poor subject. Virtually all ground water belongs to the state. They only let you pump it out of your well out of kindess. If you pump more than 35 gal a min you have to buy it. They are even trying to require water meters on private wells.
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