Groundwater Well Removal

[DMcGrath]

We have three groundwater monitoring wells that need to be abandoned and removed from the ground to a depth of at least 26' below ground surface. They must be removed due to a future landfill on top. The wells have multiple steel casings, each with the annular space filled with grout. From the inside out, you have 4" steel, grout, 12" steel, grout, 18" steel, grout (25" bore).

The overall well depth is 180' or so. Short of pile driving it further into the ground, what are our options for cutting the casings at 26' deep and pulling it out? Open excavating to get to that level will be challenging, expensive, and dangerous. I'm thinking a shape charge explosive to cut the pipes, but that's just from the "wouldn't it be cool" aspect.

Thanks

 

[civilperson]

No need for shaped charges, regular dynamite sticks will suffice. Grout the well full to a level ten feet below the final finish elevation. Bundle together and lower explosives into well to top of grout. Attach pulling implement to top portion, plug the upper section with sand bags/grout and blast. Pull out the upper fraction from the top.

 

[BigHarvey]

There are tools that can be fitted on the drill string of a small drilling rig ( for cutting steel grouting tubes ) but I doubt they can cut more then 5 to 10 mm of steel.

Otherwise AIR LIQUIDE ( compressed gases supplier ) has cutting torches that can be lowered in a hole to cut a steel pipe.

 

[bimr]

You might contact an experienced well driller.
Here is a method called overdrilling with a hollow stem auger:


Well Decommissioning
Measure the well’s depth before it is sealed. Do this to ensure that no obstructions might interfere with effective sealing. Record static water levels.
To properly seal a well:
• Remove (pull or overdrill) or drill through the well casing with hollow stem augers);
• Cut off casing 2 ft. below grade and grout in place.
Note that removal is the preferred method for well abandonment.
Use bentonite, neat cement, or a bentonite/cement mixture as the primary sealing material. Use a single, continuous operation to place such material upward from the bottom of the well to within 2 ft. of the surface. Backfill the remaining 2 ft. of annular space with materials that match the existing surface conditions (i.e., soil, asphalt, concrete).

https://www.com.state.oh.us/sfm/bustr/PDFs/TGM8-2-01.pdf

 

[bpattengale]

I'd check with the state department of health and the state PCA. Here in Minnesota the Department of Health regulates well abandonments and they have the approval say on the well abandonment.