Small Auger Holes and playa backfilling?

fluttertunnel · Post by **fluttertunnel** » Wed Aug 05, 2009 4:45 pm

Hello,

I am planning a large-scale installation. I was wondering if anyone had experience with using a one or two person gas powered earth auger. I need to drill a bunch of 2" diameter, 30" deep holes to install steel rods that form arches. For images visit the site below.

When drilling holes, does the playa have a tendency to act like sand, back filling in quickly, or does it hold form while drilling like dry clay? We will need about one minute before raising an arch and sinking it into a set of holes. Additionally, we will use removable steel sleeves in each hole to ease the process of sliding an arch into the hole.

Suggestions?

www.fluttertunnel.com

Thanks,
Bland

sputnik · Post by **sputnik** » Wed Aug 05, 2009 5:01 pm

No experience with that tool on the playa, but I can say that once you get down a few inches or so it's basically clay, and it'll be damp.

Although these holes are rather small, you still should keep the dirt someplace where it won't dry out and blow away, then backfill the holes when you remove your piece. Basic process is to put some dirt into the hole, add some water, compact with something, repeat until the hole is filled.

gyre · Post by **gyre** » Wed Aug 05, 2009 5:18 pm

An ice drill will probably work.
I got a swedish one for the hard clay here.

oneeyeddick · Post by **oneeyeddick** » Wed Aug 05, 2009 6:01 pm

I use a 1 1/2" inch masonry drill bit every year.

It's dry ar far down as my bit goes , and it requires very little pressure from above.

I use a big drill, and a two person jobby is overkill, in my opinion.

As to whether or not it'll be wet closer to the surface this yer or not, we'll both hafta wait and see.

....what Sputnik said above is required to backfill the hole when you are done with it.

fluttertunnel · Post by **fluttertunnel** » Wed Aug 05, 2009 6:34 pm

cool beans! I'll be backfilling each hole after an arch is set in place to anchor the rods in the playa. A bit of playa will be left over from displacement and I'll keep this safe for replacing it. wahoo

Igneouss · Post by **Igneouss** » Thu Aug 06, 2009 7:34 am

Earth scientist here...
Holes should stay open for a while if drilled. Not like trying to drill in beach sand for example...
Ground water varies from 5 to 10 feet below the surface. THe soil is alkalai and silt/clay. Moisture does move up toward the surface due to capillary action so you might find damp soil at 30" or shallower.

Backfilling: You'll need a steel rod with a flat end. Fill the hole a few inches with loose soil. Add just enough water to make it damp (not muddy or sticky). Tamp with rod until it feels hard (the soil

.
Continue this process until the hole is filled.

It actually takes some effort to backfill holes in soils like this. Mother nature has settled all the microscopic soil grains into a very dense and tight position. Digging it up and putting it back loose will result in obvious settlement by some later date. Work in small layers and tamp it thoroughly and it will be good.

Cheers,
Igneouss

Bob · Post by **Bob** » Thu Aug 06, 2009 9:18 am

As a manager w/DPW, I had hundreds of holes drilled on the playa for 4x4 shade structure posts, mostly using a Bobcat with a 6 or 8 inch auger attachment. The top 6 to 12 inches is often pretty loose, but it's mostly the crumbly drill cuttings falling off the auger that will drop into the hole. Just try to drill straight and have a friend shovel the cuttings off to the side.

I don't recommend wetting the backfill soil, you'll make a mess with mud sticking to your tamper. Water doesn't mix in readily, it just tends to puddle.

I'd also recommend renting the equipment ahead of time for half a day to see how it's going to work.

Ugly Dougly · Post by **Ugly Dougly** » Thu Aug 06, 2009 9:50 am

Yeah, it's no place for a failed experiment.