Post holes in heavy clay and limestone

Tom_H · Jul 29, 2005

I have 1'-4' heavy clay atop 4' to 16' of a water impermeable silica cemented hardpan called durapan. It is like (relatively) soft concrete. Someone else mentioned this No. CA stuff.

Big backhoes can handle it. Medium size struggle, Small ones can only scrape at it.

In this stuff, PHDs need carbide fishtail augers with downpressure. A friend with a Bobcat skid steer, front auger, downpressure, and carbide tip IS able to drill into it pretty quickly.

If I were in your situation, I'd look in yellow pages and call every listing under "drilling" that lists post hole drilling. Some go by the hole, some by the hour. The bigger the rig, the rate at which the price climbs gets steeper and steeper.

I only think this method holds a tiny degree of possibility for any efficiency, but just out of curiosity, you might price getting a backhoe to rough out the holes, then use your own tractor FEL, reversible rear blade, or box blade with an extra rear facing blade to refill them and your own standard run-of-the-mill PHD to re-bore. Timewise, it would be inefficient. On the other hand, if the cost of a backhoe roughing out the holes were a lot less than augers, would the $ saved be worth your time to re-bore? Probably not, but maybe worth thinking over??? Just a thought.

wroughtn_harv · Jul 29, 2005

Call Wylie Drilling in Farmersville. While they won't be interested in your job they have subs on hand that will be.

You can also call Bobby Robinson in Lavon. His son has a single axle pier drilling rig and he does fence post holes in rock all the time.

The rigs are Texomas and they get through our limestone quickly. They are limited by terrain and access. But if they can drive down a line you will be pleasantly surprised at how quickly they can drill a hole for you.

My clay augers are Pengo carbide tipped and the flights are hardfaced. I can go through asphalt real easy and into soft limestone with no problem. But if you're into hard limestone and I believe that's what you got up there, it takes more than just a sharp bit and a thousand pounds of down pressure to make it.

I've had the single axle Texomas go through concrete and into the blue shale with relatively ease with a good bit for me.

Call Bobby, he's in the book. If the kid is anything like the old man you'll get your money's worth and more.

GabeTX · Jul 29, 2005

Thanks for the referals, I'll definitely check them out!

Driving even a large truck along the fence line should be no problem; you've given me some hope that this won't be too financially painful...

GabeTX · Feb 27, 2006

And 7 short months later...

I called Bobby Robinson, who referred me to his son, who referred me to Mike Gruing (IIRC), who referred me to Alex Schroeder.

Who came out today and did an excellent job! Alex had an (enormous) pier drilling rig and bits that had no problem chewing through the limestone, although he did mention he went through quite a bit of carbide. Even though he'll have to come out here again for a couple hours to knock out several holes he couldn't get to because of mud (we're in the middle of a drought and we get our first substantial rainfall two days before I have someone coming out to work on my place!), it'll still end up substantially cheaper then renting the Bel-Tec.

And speaking of enormous rigs and mud (not sure what the proper term for the truck is, but it was as big as a cab-over-engine semi, although set up for the drilling rig and not a trailer) ...

He did get stuck pretty deep, but my little Jubilee somehow managed to pull him out, although it took a couple tries. I think it liked taking a break from moving posts around on the cary-all. /forums/images/graemlins/smile.gif