<p>I'm having a water well drilled on my property. The drilling crew has been working since Wednesday. They are using an airlift rig with a 6in bore. They are at 300ft and only have 4gpm. I would really like to determine what formation this well is in before I make a decision Monday on whether they should continue drilling. I really need to get ~15gpm from this well, but 30+ would be ideal. </p>

<p>The well is in the fall line hills area of Alabama. Specifically, it is here: 32.9672430, -86.8522270. That roughly corresponds to <a href="https://i.sstatic.net/Sp0ID.jpg" rel="nofollow noreferrer">this location on the physiographic map of Alabama.</a> The bore went through a few feet of topsoil, then about 30ft of brown/white/yellow clay then 60ft of grey/black clay. At 90ft he hit consolidated rock, a grey/black shale that produces <a href="https://i.imgur.com/w3m9IZ3.jpg" rel="nofollow noreferrer">rock fragments</a> and a <a href="https://i.sstatic.net/wak4W.jpg" rel="nofollow noreferrer">clay-like substance when pulverized.</a> The well is cased to 100ft. At 260ft we hit water and the well was producing 4gpm. At 300ft the rate remained unchanged. The well driller has told me that the material alternates between hard and soft layers and that he has hit a few pockets of limestone. The shale fragments are scratched by steel, copper, and aluminum. There is no distinct odor from the shale. There are sparse fragments of quartz. I haven't seen any pyrite. The shale does not burn, even under a propane torch. The location has an outcropping of what I believe is <a href="https://i.sstatic.net/cV03S.jpg" rel="nofollow noreferrer">sandstone with a good bit of quartz.</a></p>

<p>Since the bedding is shale, I think this well is in the Valley and Ridge formations. I think it is in the Coosa River valley formation, although the land drains into the Cahaba. The well driller has told me that the rock is Chattanooga Shale, but I'm not sure that is correct because it doesn't have any smell, doesn't seem to contain any pyrite, doesn't combust, and would have to be 200ft thick. From what I understand the Chattanooga Shale formation isn't that thick.</p>

<p>If this well is in Chattanooga Shale I may be out of luck because it's an aquiclude. That is unless I could drill through it and get into another formation within 450ft or so.</p>

CC BY-SA 4.0
2020-06-07T18:02:15.473Z
References:
This is the Alabama State Water Resource Survey. Details on the  Valley and Ridge sections start on page 377. https://www.gsa.state.al.us/img/Groundwater/docs/assessment/00_B186_StatewideAssessment_Print_Document.pdf

This is a groundwater survey for sub area 7 which includes well production for each local formation. https://pubs.usgs.gov/of/1996/ofr96-470/pdf/ofr96-470.pdf

Here is some limited data for other wells in the area. Well number E-2 is less than 1/4 mile from my well. https://www.gsa.state.al.us/img/Groundwater/docs/wellrecords/Chilton/Chilton_E.pdf
Phillip Brantley
CC BY-SA 4.0
2020-06-08T01:15:18.893Z
Thank you for the good description but it is hard to say without a good knowledge of the area. One option for areas with poorly producing wells is to use a longer screen, if allowed by regulations (usually you can't interconnect different formations). The longer screen will increase the production and a deeper well will provide more water storage, to even out the supply and allow the well to recover between high use periods. That is more expensive, though. You could also over-ream with a larger casing so that there is greater screen area for water to enter the well. That, too, can be expensive
haresfur
<geology><structural-geology><hydrogeology><regional-geology><geologic-layers>
What local formation am I drilling?
Phillip Brantley
# What local formation am I drilling?

(Asked by: username_0 on 2020-06-07)

I'm having a water well drilled on my property. The drilling crew has been working since Wednesday. They are using an airlift rig with a 6in bore. They are at 300ft and only have 4gpm. I would really like to determine what formation this well is in before I make a decision Monday on whether they should continue drilling. I really need to get ~15gpm from this well, but 30+ would be ideal.

The well is in the fall line hills area of Alabama. Specifically, it is here: 32.9672430, -86.8522270. That roughly corresponds to [this location on the physiographic map of Alabama.](https://i.sstatic.net/Sp0ID.jpg) The bore went through a few feet of topsoil, then about 30ft of brown/white/yellow clay then 60ft of grey/black clay. At 90ft he hit consolidated rock, a grey/black shale that produces [rock fragments](https://i.imgur.com/w3m9IZ3.jpg) and a [clay-like substance when pulverized.](https://i.sstatic.net/wak4W.jpg) The well is cased to 100ft. At 260ft we hit water and the well was producing 4gpm. At 300ft the rate remained unchanged. The well driller has told me that the material alternates between hard and soft layers and that he has hit a few pockets of limestone. The shale fragments are scratched by steel, copper, and aluminum. There is no distinct odor from the shale. There are sparse fragments of quartz. I haven't seen any pyrite. The shale does not burn, even under a propane torch. The location has an outcropping of what I believe is [sandstone with a good bit of quartz.](https://i.sstatic.net/cV03S.jpg)

Since the bedding is shale, I think this well is in the Valley and Ridge formations. I think it is in the Coosa River valley formation, although the land drains into the Cahaba. The well driller has told me that the rock is Chattanooga Shale, but I'm not sure that is correct because it doesn't have any smell, doesn't seem to contain any pyrite, doesn't combust, and would have to be 200ft thick. From what I understand the Chattanooga Shale formation isn't that thick.

If this well is in Chattanooga Shale I may be out of luck because it's an aquiclude. That is unless I could drill through it and get into another formation within 450ft or so.

**Tags:** geology, structural-geology, hydrogeology, regional-geology, geologic-layers

> **Comments:**
> **username_0**: References: This is the Alabama State Water Resource Survey. Details on the  Valley and Ridge sections start on page 377. https://www.gsa.state.al.us/img/Groundwater/docs/assessment/00_B186_StatewideAssessment_Print_Document.pdf  This is a groundwater survey for sub area 7 which includes well production for each local formation. https://pubs.usgs.gov/of/1996/ofr96-470/pdf/ofr96-470.pdf  Here is some limited data for other wells in the area. Well number E-2 is less than 1/4 mile from my well. https://www.gsa.state.al.us/img/Groundwater/docs/wellrecords/Chilton/Chilton_E.pdf  
> **username_1**: Thank you for the good description but it is hard to say without a good knowledge of the area. One option for areas with poorly producing wells is to use a longer screen, if allowed by regulations (usually you can't interconnect different formations). The longer screen will increase the production and a deeper well will provide more water storage, to even out the supply and allow the well to recover between high use periods. That is more expensive, though. You could also over-ream with a larger casing so that there is greater screen area for water to enter the well. That, too, can be expensive  

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## 0 answers

