Plugging water wells that are abandoned or deteriorated is a requirement of State Law.
There are three different courses of action that can be implemented to eliminate the hazards of an abandoned well.
1) Return the well to an operable state by making sure the casing, pump, and pump column are in good condition.
2) Cap the well to prevent surface water or contaminants from entering it. The cap must be able to support 400 pounds and prevent easy removal by hand. For more information, see the Texas AgriLife Extension Service publication L-5490, Capping of Water Wells for Future Use (online, at https://agrilifebookstore.org, or by phone, at 888-900-2577).
3) Plug the well from the bottom to the top with bentonite chips, bentonite grout, or cement. Large-diameter wells can also be filled with clay-based soils, compacted clay, or caliche. Details on what you should do prior to plugging your well, as well as on the well plugging operation itself, are best done by a Licensed Water Well Driller with the TDLR.
Slurry calculations for a 5" I.D. of well casing (method we use)(If you have other designs of plugging a well we will consider them):
In a 5" cased well the plugging formula is for 1 sack of Portland Cement with less than 7 gallons water per 94 lb.sack will fill about 10.4' linear feet of casing when properly mixed and pressure pumped inside of well casing and up any voids in annulus side of well via tremie method.
A=(3.14)(radius squared)(depth of well) = cubic feet of cylinder (well casing)
1) After you square the radius in inches then convert the inches to decimal feet using the ratio of inches per foot.
2) Then multiply by depth to get area in cubic feet, then multiply by 3.14.
Then convert the derived cubic feet to gallons of slurry needed with formula below.
Another source is Halliburton Red Book tables if available
Formula: 1 cubic foot is = 7.408 gallons of liquid
After cementing cut casing off 4' below surface of ground level elevation
Velocity of rock to water level:
This works great when you don't have a electric tape spool.