Cleaning out and reusing some old concrete fence post foundations?

[Bill Guenthner]

We are repairing some old fencing along the driveway, and the old fence of 8"x8" posts turns out to be anchored into 16"x 48" foundations of concrete surrounding some now insect eaten 8x8".

Could the remains of the 8x8s be augered out with a six inch auger? I just need them mostly out, not perfectly clean.

Thoughts from the auger experts here?

Any better ideas?

All the best,

Peter

There are creosote soaked pine posts and untreated cedar posts around here that have been in the ground for 100 years with no concrete. There are cedar post fence lines in the local impoundments that are flooded People way over use concrete when setting posts. A good post set deep isn’t going anywhere.

 

[plowhog]

Could the remains of the 8x8s be augered out with a six inch auger? I just need them mostly out, not perfectly clean.

If you set another post in a hole that is "mostly" cleaned out, what happens when the remainder of the 8x8 completes its rotting process? A void between new concrete and old?

I'm not familiar with what sort of auger people are referring to here. A post hole digging attachment on a tractor would seem woefully inadequate since it usually digs in dirt instead of going through wood.

This seems more of a vertical boring application. Because in at least some instances you are likely to be boring through solid wood.

Sorry I can't be of more help, but drilling in nearby virgin dirt with an auger seems much less complicated. Even though I appreciate wanting the strong desire to reuse what is already there.

 

[newbury]

I would attempt to drill them out first. But I would use a drill with a clutch so if it bound up it would stop (be prepared to us up a few drill bits, and think largest bit available). Then either an appropriate accelerant to burn out the remaining wood or some strong acid wash.
I had a similar problem with 2x4's stuck and rotted in rectangular tubing, I drilled and burned.

 

[plowhog]

untreated cedar posts around here that have been in the ground for 100 years with no concrete.

I think this can vary a lot by area. Last week I put a 20" diameter cedar tree on my sawmill. Already had in mind what boards to make and how to use them.

That plan fell apart when I found the tree center full of wood boring insects. This was a seemingly healthy cedar tree felled by the utility company. In my experience this is quite unusual for cedar but it does happen.

 

[ponytug]

@newbury Yes, I agree that a clutch is essential, as is a reverse.

@plowhog Yes, I was thinking of two different kinds of augers; small ones for a hand drill to drill for lag bolts to pull out the remaining post, and regular soil augers.

FWIW: @plowhog Eastern cedar and western cedar are different species. Generally, the western cedar is more insect resistant, though as you say, there are exceptions. Funnily enough, it is the eastern cedar that tends to be made into chests and closets because most people think it smells better.

I think part of the rot/insect may be more of an issue locally is that in frost free areas, termites and wood boring insects never really have to slow down much.

Probably 5-10% of the pressure treated "ground contact" rated 8x8" that I installed eight or ten years ago are in trouble, some after four years. My neighbors have similar experiences. By observation, 0.4% ACQ alone clearly doesn't cut it locally.

There is also that trees 100 years ago grew and were harvested differently than today. I think that another part is that older preservative treatments were, and are, much more toxic to bugs and humans alike. (Creosote, arsenic, chromium, and even pentachlor). But there is also something of a luck of the draw. I was talking to a utility pole inspector a few years ago as he was renewing the copper paste around the base of the pole, and asked how long a pole usually lasts. He said 30-50 years around here, but some fail much sooner, and he had personally inspected one from 1905.

Still looking...

All the best,

Peter

 

[SpringHollow]

I would be tempted to vibrate in new pipe and go from there. I would think 8' pipes 5 - 5 1/2' in the ground would suffice, no concrete needed. 10' pipes if you are really concerned.

Ken

 

[dirttoys]

After reading all, probably driving pipe would be the best. I know it is cali, but, can't you spray/soak the posts with bifen a couple of times a year? Won't save the compromised stuff, should prevent the eating of the ones that are good?

Best,

ed

 

[ponytug]

@SpringHollow Yes, pipes were "Plan A" until I saw the local prices for 5" and 6" pipe. Even not so local prices. PreCovid, I could buy pipe from our local recycler, but they closed the retail sales for the duration. I am working on that one still, but I'm not very hopeful. With my post driver, I can probably get them a fair ways into the soil, but haven't tried the post driver on pipe in this soil yet.

@dirttoys Yes, well being California, the short answer is no. The longer answer is if I became a state licensed applicator, then yes, it might be possible. Given the location and watersheds, I am not certain it would be possible even then.

I am leaning toward kicking the can down the road until July/August when the posts might be totally dry, and seeing how many I can pull out out. If I can get 85+% out by just lifting, it would probably be worth it to fiddle with the remainder. If not, I will probable cut them off at ground level and auger new holes for concrete bollards.

In the mean time, I am going to try pulling a few that have sheared off just to see how bad it could be. With the drought, it is already too dry here for outdoor fires.

All the best,

Peter