Well from Hell

Our new well is driving us fits. In Minnesota, we are down about 250 ft. just above sandstone, PVC casing, Constant Pressure Pump system, flows max about 25 GPM. Water is absolutely great, except for very strange issue. When we start up flow, if greater than 5 GPM, will run clear for a few minutes, then get silt and turbid for a few minutes, then start running clear, and will run clear indefinitely. As soon as we stop for 5-10 minutes, same thing over. How is silt getting into well when it runs clear. At low flow, silt seem steady, doesn't want to clear.
Well was developed and also driller came back and blew out second time. Water static level is about 75 ft. and pump, 1.25 Hp is at about 140 ft. PVC slit screen about 20 ft.
We hate to abandon this and start over, because water in this area in sandstone has lots of iron at deeper levels.
We don't have a clue why after several weeks, situation is not getting better and about to give up.
Was error made in casing, screen, grouting, etc. or is just well not wanting to develop. Or some strange plume issue.
We are thinking of trying large sediment tank filter backwash system.

You need a water test for iron. It sounds as if you're getting a slug of oxidized iron (rust).

So what does the this "silt" look like? What color? Is there any grit? Where do you see, since you say you have to run over 5 gpm?

Current Theory, Actually the only one

After much poking around and talking with other water folks, the following seems to make the only sense, Any thoughts are appreciated.
Since there is an aquifer at about 100 ft. and the one that we are tapped into is at about 200 ft., there is a leakage down the casing that is providing silt to the surface of the PVC screen. When we first start the well, this silt is drawn in and creates troubles for several minutes, then the water starts to run clear. However when the well is stopped, the silt leakage starts again and when well pump is started again, same thing all over. It appears that about one cup of silt is introduced.
There are many situations that can cause the casing to not have been properly sealed, we will probably never know. The driller has good reputation, and says he did a complete fill and used the benenite? for the top 75 ft.
This leak seems to be the most likely way that silt would enter, get pumped and then not show up until well is idled for some time.
We have now pumped about 50,000 gallons to try to get well to develop, but not much change.
Next step is new well, only issue is if well driller will go to this depth again. This is where the really good water is located. Do you think he really knows but doesn't want to own up to slip up?

In our area, sometimes this happens as well. Sand or silt is like sand at the beach. When it is wet, it stays packed tight. When it is dry, it sluffs off like blow sand. So when you first start using water it pulls the well down from 75' to maybe 100'. This top layer of sand is now dry and sluffs off into the water, falls to the bottom, and gets pumped out. Only the outside or top layer sluffs off each time. When the water is turned off, the water level rises to 75', and this sand is wet again. So the next time you draw water, it starts all over again.

Instead of pumping steady all day long, try running the pump until it clears, shut off the pump, what 10 minutes, and do it again. I have even put pumps on timers so it runs 10 minutes, and if off ten minutes. This will eventually wash the loose sand away at the top of the water level.

Another trick we use if the silt or sand is heavy enough to settle to the bottom is this. We use a 4" motor shroud over the pump and motor. Usually a motor shroud is cut off flush with the bottom of the motor. However, we make it about 5' longer than the pump and let it stick down 5' lower than the motor. At 25 GPM or less, the velocity in this 4" pipe is not fast enough for the sand to follow the water. The sand just settles out the bottom of the 4" pipe, while clean water is slowly traveling up to the pump. The well is still making sand, it just is not entering the pump. The draw back to this is that eventually this sand will fill up the well all the way to the pump. At a cup a time it may take many years to fill from 250' to 140' where the pump is. Then you need the pump pulled and the well cleaned out.

Regarding Cycling well

Valveman, many thanks for your ideas. We have been running outside faucet on 20 on/20 off with sprinkler timer on hose. We have been running about 12 cycles a day for over 2 weeks, i.e. maybe 25,000 gallons at 12 GPM.
There is no change. I am assuming that the silt, about 40 micron, is coming in somewhere past the screen. I guess we believe the PVC casing is intact. We have a very long PVC screen, about 25 ft. or more, and I am afraid that somewhere near the top or bottom, the screen has not developed in that area, and the diff pressure after the well shuts down, and static conditions are realized, allows some leakage into the casing.
This silt will settle out to a degree, will cover the bottom of a plastic cup in about 30 minutes to one hour.Actually, each fresh cycle may produce several cups of silt, seems to taper off during the day, but a fresh start of silting each morning. This has to not be good for the new pump.
There is no evidence that situation is improving and well driller is about to throw in the towel and try again.
Any additional last minute thoughts are appreciated.
PS, a call to me at 952.474.6918 is certianly OK. You seem to have experience in this mess.

valveman said:

In our area, sometimes this happens as well. Sand or silt is like sand at the beach. When it is wet, it stays packed tight. When it is dry, it sluffs off like blow sand. So when you first start using water it pulls the well down from 75' to maybe 100'. This top layer of sand is now dry and sluffs off into the water, falls to the bottom, and gets pumped out. Only the outside or top layer sluffs off each time. When the water is turned off, the water level rises to 75', and this sand is wet again. So the next time you draw water, it starts all over again.
.

Click to expand...

In actuality it is just the opposite.
The sand in a well is never "dry", when it is , we will use the term "drained of water", the sand will stay in place, but when it is saturated with water, that is when it can sluff down.

Think of it like digging a hole at the beach. As the hole fills with water, the sand with the water starts to sluff down. The sand that is not full of water stays in place.

Travis

Waterwelldude said:

In actuality it is just the opposite.
The sand in a well is never "dry", when it is , we will use the term "drained of water", the sand will stay in place, but when it is saturated with water, that is when it can sluff down.

Think of it like digging a hole at the beach. As the hole fills with water, the sand with the water starts to sluff down. The sand that is not full of water stays in place.

Travis

Click to expand...

I'll go for that. Either way it is when the water level goes up and down that the sand starts sluffing off. So you have to keep raising and lowering the water level until it cleans up.

I think the long shroud would help but, if the casing is large enough, Lakos makes a sand seperator that will fit over the pump.

Inches Microns**
0.056 1400
0.028 700
0.0098 250
0.0059 150
0.0030 74
0.0017 44
0.0015 37
0.0005 12
0.0002 6
0.0001 2


A K-packer seal and a 2.5", #10 or 0.10" screen with some 2.5" liner pipe should stop the silt problem.
Doing it this way will slow down the flow some.
The driller "should" know how to install it.

I have run across new wells that had a cracked screen, and the screen looked good when it was installed.

Valveguy is right, If sand is coming into the well,and it has not stopped by now, it's not going to stop.


Travis

howens said:

We have been running outside faucet on 20 on/20 off with sprinkler timer on hose. We have been running about 12 cycles a day for over 2 weeks, i.e. maybe 25,000 gallons at 12 GPM.
There is no change.

I am assuming that the silt, about 40 micron, is coming in somewhere past the screen. I guess we believe the PVC casing is intact. We have a very long PVC screen, about 25 ft. or more, and I am afraid that somewhere near the top or bottom, the screen has not developed in that area, and the diff pressure after the well shuts down, and static conditions are realized, allows some leakage into the casing.

This silt will settle out to a degree, will cover the bottom of a plastic cup in about 30 minutes to one hour. Actually, each fresh cycle may produce several cups of silt, seems to taper off during the day, but a fresh start of silting each morning. This has to not be good for the new pump.
There is no evidence that situation is improving and well driller is about to throw in the towel and try again.
Any additional last minute thoughts are appreciated.

Click to expand...

I've always heard that the naked eye can not see particulates less than 50-45 microns in size.

IMO, although I've never seen sand in well water, "sand" is not going to take 30-60 minutes to settle in a glass or cup of water.

Is the stuff actually gritty or is it soft and disappears if you rub it between a thumb and forefinger?

Oxidized iron would disappear like dust. I suggested a while back in the thread that this could be caused by oxidized iron, I'm still believing it may be that instead of "sand". And you say there is more of this stuff the longer you allow the well to sit; which is how ferrous iron oxidizes over time.

Pumping the well off should be done open discharge out at the well by lifting the drop pipe up out of the casing a few feet and turning the pump on for hours; without running the pump dry. Running it out through an outside faucet and a hose for a bit of time each day is IMO, just wasting time and effort.

The reality is the well is a loosing proposition. Any screens, filters or whatever will plug up in short order. Anything you do now is only a temporary stop gap measure. Drill a new well.

If he/they can't develop it to clear water and it has sand in it, I have a very good sand filter for a few hundred dollars.

If the same and it is not sand, and it is due to oxidized iron, he can 'filter' the iron for less than say $700 to $1000.

BTW, that is 2 TRILLION dollars, update as of 8 21/09

Woops, yes TRILLION a mere pittance.

Over the years I have found that sediment wells, even with filtration eventually reach the point where the sediment will fill in around and over the pump itself. Then there is the wear on the impellers and volutes from sediment abrasion that shortens pump life. If it's dissolved iron then it can be treated.

For sediment build up which normally takes many years, you raise the pump 5-10' or, air lift or bail the sediment out of the well.

All this is much less expensive than drilling a new well now when the reseeded yard has hardly had a chance to sprout (if the yard has been planted yet) or, later when the landscaping is all matured.

And really, a new well never comes with a guaranty of water quality so, he could drill another and have the same problem and MUCH less money for treatment equipment etc..

For sediment build up which normally takes many years, you raise the pump 5-10' or, air lift or bail the sediment out of the well.

All this is much less expensive than drilling a new well now when the reseeded yard has hardly had a chance to sprout (if the yard has been planted yet) or, later when the landscaping is all matured.

And really, a new well never comes with a guaranty of water quality so, he could drill another and have the same problem and MUCH less money for treatment equipment etc..

Check out your updated date, it should be as of 8 21/09

Today's Drama

Again, many thanks for those that have posted thoughts.
The silt I believe is about 40 micron, according to a sheet that I saw, this is about like Portland cement powder.
The well guys came today, put a 10 ft. Johnson screen, very fine down in the casing and air pumped for 3-4 hours. Water was looking pretty good, some loss of flow, maybe about 20 vs 25+ before. Also bottom 5 ft. now has pea rock in to help seal off lowest level of screen.
They buttoned it up started running on well pump and flow dropped to about 4-5 gallons, water was fair, but flow was not good. They left small well truck in yard and will return tomorrow, maybe with big rig.
I think a new well is coming. PS, No money has yet changed hands and they know it won't until I get good and adequate flows.
I am still worried they will either want to stop at first aquifer, which is bad water, go on through the second one which is where the good water is, and go into the sandstone, which is almost always high Di solved Iron Content
We had had lots of Di solve Iron in the past and I have pretty good idea of that. Have a big 4 tank air system with back flushing currently in basement to deal with iron from old well.Don't think this is what is coming out, and well guys agree.
However, they are also starting to refer to this project as "project from hell"

I hope they drill you a new well and that it performs better. I have run into the same silt problem around here many times. There are screens and filters that help but in my experience the fix was only temporary. When the silt is that fine, it plugs the filters, wears the pump parts and still makes it's way through the system, plugging up faucets, flush valves and settling in water heaters. You will be screwing with it every few months or years forever.

well from hell, final chapter

Last week, the driller decided to throw in the towel and drill a new well. We went down 260, hit sandstone, went down another 80 ft. and now have a good well. We have some soluble iron in water, about 2.5ppm, typical Minnesota sandstone water, will need to get my iron filter system going again, however softener seems to be handling it.
Well flows about 30GPM at 80PSI with VVPump, so that is good.
The Sand Blocker Filter, about 12 ft. of it, did not do any good, just got clogged with the silt. Last effort on earlier well was to fill bottom 10 ft. of screen section with pea rock and bigger to hold down rock, but all that did was reduce flow.
I don't think we will ever know what caused the silting, but I am suspicious that we had a leak down the casing and with water coming from upper and lower aquifer, caused the problem.
Many thanks to all for your help and support.
Howell Owens, Minnesota.
PS, I am only paying for the one well, but will more depth and steel casing, that was a good adder.

Glad it worked out for you in the end.