New Well - New Problems

[ronfellows]

I just had a professional well driller install a new well for an existing 12 zone irrigation system in North Texas. Each zone has the typical 5-6 rotors and/or sprinklers. I believe each zone currently uses about 15-20 gpm at 60psi.

Here's my problem.
The new well is 70 ft deep and has a new Goulds 1.5 HP submersible pump at 60ft. The static water level is at 45 ft. When the well is turned on I get about 30 gpm for one minute and then the water output drops to the refresh rate of about 2 gpm. With a gate valve, I can limit volume to the required 15 gpm and enjoy the sprinklers for about 2.5 minutes .

I should mention that about 10 homes in our development have recently had the same driller put in new wells. Eight homes have wells that are producing 80 gpm, two of us at 2 gpm, and one dry well. All of the wells are 110 to 175 ft deep except the two of us that are getting 2 gpm that are at 70 ft. All of the wells are within an area of two city blocks.

The driller has suggested that he drill a new 5” test well next to the old well and go down to 170 ft to see if we can find more water. If more water is there, he will drill it out to an 8” well, install the casing and pump and all should be OK.

My question is this:
I think the odds are good for drilling down to 170ft to improve the refresh rate and hopefully will improve the volume to usable levels.

If the worse case happens and we find no additional water and maintain just the 2 gpm refresh rate, won’t the new well now have 100 ft of additional water storage in the well (compared to the first well)? If the pump is then moved down to 160ft, my hope is that I should be able to pump out 15 gpm for about 15 + minutes before the well is pumped out. With the 20 gal pressure tank and a CSV valve installed, hopefully I will be able to extend this even further.

The current well has the micro screening pipe at the bottom 20 ft. Would it improve our chances if we add additional 20ft sections of the screen pipe to provide a wider vertical surface area for water to enter the well?

I am sure you are wondering why the first well is only 70 ft when every other well is over 100 ft. My well was drilled first! They thought it was producing 35 gpm when the blew out the well and so they stopped drilling. By the time the well casing and pump was installed (a week later), it was producing only 2 gpm .

The new test well should be drilled on Thursday. If we don’t find additional water, should I have the driller drill out the test well to 8” anyway, install the 40-60 ft of screen pipe, casing and pump?

Any ideas and suggestions would be appreciated.

[speedbump]

Your driller should have the answers to all these questions. Since he has the experience, he should be able to answer the questions.

I don't see how he was able to get 30 gpm out of a 2 gpm well, unless it was for only a minute or so. If that's the case, he should have pumped it for a much longer time.

You can only add screen if there is vein for the screen. If the vein in 20 feet thick, only 20 feet of screen will produce water.

bob...

[ronfellows]

Bob - you are right on. Actually they didn't "pump" out the well to see what it would produce. They just blew out the well with compressed air at about 40 ft and estimated that it would produce 30 gpm based on the water that came out. This was apparently a shortcut when they were sure the wells would all have lots of water.

How do they know where the vein(s) are located?

[speedbump]

They should be looking at the material coming up while drilling.

bob...

[Gary Slusser]

In a small area like your development, with other wells down 100' deeper, your well is probably like not having your straw down in the milkshake as deep as the neighbors' straws; IOWs y'all are using a communal water source. If it was me, I'd want to know how deep the dry well is and how far it is from me.

[ronfellows]

There are three wells close to my well. The first is next door (about 100 ft away) and also down 70 ft. It also gets the 2 gpm. The second is about 120 yards away and produces over 85 gpm. It is an outstanding well used for landscape irrigation in the common areas (about 6 acres). The dry well is also about 120 yards away from my well and was down to 180 ft. The dry well is about 140 yards from the 85 gpm well. (Think of an equilateral triangle). We live on a peninsula that is surrounded by water from a 23,000 acre lake.

The acquifer is normally down from 50-90 ft. We have heavy clay soil, but I assume that we also have some ground water seepage from the lake at probably 20-25 ft. The lake is about 75 yards from my well.