Manhole/Inspection Chamber Filling with groundwater! Please Help

mikey1123

mikey1123

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Hello Everyone.

We have recently had a 400ft Deep Bore Well Drilled on our land.
The well contractor made us excavate 2 feet below the well head (Challenging as we are right ontop of the bedrock/granite) and then returned to install the pump and told us to build a chamber around the well head as soon as possible.

The groundwater raising from the ground submerges the well head and as such contaminates it.

The well contractors dont want to know and say we are responsible for all groundwork. As such i have tried over 5 mnths to get a civil contractor but no one will help as we live very rural.

This forced me to try and protect the wellhead from groundwater as it had already been contaminated.

I installed an inspection chamber and naively assumed a layer of concrete surrounding the head inside the chamber would prevent groundwater rising. Sadly it did not.

I am at my wits end i dont know what to do.
I currently have a sump beside the well head with a pump that switches on by a small float.
as i have ensured this is below the well head level it is preventing contamination
. But i cant keep this in place for ever. I have ordered liquid rubber and the primer and hope that dozens of coats of this on the concrete base, inside and outside the chamber may help.

Hopefully someone on this forum may be able to tell me what to do. Sincere thanks to anyone who has taken the time

MIke
 

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Why is the borehole casing not extending above ground?
 
I have no idea, it was the well contractors that told us to dig two feet and put down a layer of concrete. Then when they installed the pump and capped it they had removed the top couple of feet. I didnt question it at the time as thought i was in good hands the price I paid. Were in rural ireland where customer service is none existent. Nothing had been explained. We thought they'd leave us with a finished and plumbed system.
 
Hopefully you can get it resolved, I'm sure someone here might have some info.
 
There is lower ground near by. I contemplated running a pipe from the bottom of the chamber to lower ground to act as a drain but as we are on granite bedrock with 0 substrate, this puts the cost of rockbreaking to accomodate such a channel at that deptj at approx €10,000. Not an option, Sadly. I presume thats what you may have been about to suggest. If not please forgive me, im grateful for any and all advice.
 
We are on a mountain side, directly on bedrock. Land rises behind us and falls infront of us.
 
Then I'd be thinking of putting an extension on that pipe coming out of the ground.
 
The pipe coming out of the ground is from the temporary dirty water pump i am currently using to prevent the water table rising to the point it once again submerges the black chamber where the well head is located. Im hoping there may be some way i can waterproof the chamber instead of having to permanently depend on the temporary dirty water pump in the sump. Thank you for your time and advice.
 
I mean the large black convoluted pipe. Isn't that the borehole liner?
 
Hi John,

The large black inspection chamber has the well head inside at the bottom, please see attached pic. The pipe coming from this chamber contains piping and electricity going to nearby garage. The problem is that when all of the area around the chamber is backfilled with stone and earth it creates groundwater pressure which floods the chamber by water rising through the concrete base. I have asked the well company if they can raise the head. It'd be a welding job. No reply. Forgive me if that isnt what you meant.

The well head in the attached pic is becoming submerged allowing water to enter the 400 foot well and contaminate it with groundwater.
 

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freddiemercurystwin said:
Sorry being a bit thick here but can somebody explain this in simple terms?
Click to expand...
hi freddie,

Under all of our feet there is groundwater in the earth (Think digging a hole at the beach in sand which fills with water)
Sometimes its far below us. Sometimes its right underneath our feet.
I just had a 400 foot hole drilled in the bedrock in my garden. This fills with water from fractures in the bedrock hundreds of feet below.
The "Groundwater" the water which appears when you dig a hole or which is on the surface, think a puddle, is getting into this 400 foot hole which is full of pure clean water. It is contaminating it making it unfit for consumption. This water is forcing its way into the sides and up through the concrete of the black cylinder in my pic which contains the 400 foot hole.
 
Thankyou very much for your time and reply. Unfortunately i have to try and make what i have work. My only problem is groundwater penetrating the black inspection chamber. How do civil engineers prevent their manholes filling with groundwater i wonder?
 
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