My 16 year old son is working on an Eagle Scout project which will require the manual digging of 12 post holes.
The soil is mostly black clay with little or no stones. It will be softened beforehand by soaking with water for the week before the project is to start. The holes will need to be 18 inches deep and 6 to 8 inches in diameter.
My question is how long per hole will it take team of three young men (14 to 16 years old) who will be alternating at digging with a manual post hold digger, clearing with a shovel and digging bar, and resting?
Any Dopers out there with practical experience that can help with estimating the time this will take?
12 post holes and 3 people = 4 holes per person. With a post digger it should take like 20 minutes per hole for their age, so with breaks and chatter a couple of hours should be plenty, maybe even an hour and a half.
That’s my estimate anyway. Is there a reason why you need an approximate duration?
We just want to validate our time estimate which was longer that these replies which is good - it won’t take as long as we thought it might.
As for why we want to make sure this digging portion can be be completed in one morning. My last experience in post hole digging was in much more rocky soil and many many years ago so I didn’t completely trust my experience.
A soaking a little each day for several days will make the job go much faster.
You want the soil damp not muddy.
Here in So Cal the difference between digging in dry and damp soil is night and day. If you live in a rain Forrest YMMV.
Back when I was collecting geochem the post hole digger was our primary ‘acquisition instrument’. I’ve dug many thousands of holes from Florida to Alaska and still the answer is going to be “it depends.”
One, are these fairly athletic, coordinated kids? Their size, weight and accuracy will correlate directly with whether this is a quick job or an arduous task. Two, is the black soil sticky or more of a loam?
Frankly, if they’re pretty handy and the soil isn’t too sticky then 18" is child’s play. The hole will be 6 - 8" just in the normal course of digging. If they can grab about 1" of medium with each jab then they could finish each hole in 3 or 4 minutes. If they struggle or the dirt is very sticky then it’ll take longer by orders of magnitude but I’d still be surprised if it took more that 10 or 12 minutes per.
Proper technique will help. They want to hold the PHDs (post hole diggers) completely vertical in front of them with arms slightly bent and thrust it straight down. Spread the upper handles to pinch off the dirt, lift and deposit it a couple of feet away so it won’t slip back in the hole. Do this a couple of times then move 90 degrees around the hole and repeat it. This keeps both the hole bottom and sides cleaner.
Tip: Make a mark 18" up from the bottom on the PHD with a Sharpie, etc. When that mark becomes flush with the ground surface, that hole is done. Good luck.
Also, the PHD itself is a big factor. The lightweight cheapies from Home Depot will do nothing but piss you off. Get a heavy, solid metal pair and your life will be much easier. Also, like most hand tools, they work best when sharp.
bump - thanks for the experienced response and while this is being done in the DFW area the soil is literally called “Houston Black Clay”.
lieu - thanks for the in-depth response and advice - this soil will be somewhat sticky so I’ll mention that to my son we need to plan for that. The plan is to have multiple post hole diggers and digging bars.
As this is an Eagle Scout project, see if your local hardware rental center will loan you a couple of diggers, if you’ve not already acquired them. They may even loan you a power operated one (he may have to ‘delegate’ an adult volunteer to run that part.)
if the clay is sticky have some buckets of water to periodically rinse the clay off the tools in. having clay clinging to the tool impedes it functioning well.
Without knowing your exact location you’re probably in the Texas Blackland Prairie. I’d imagine it’s the Eagle Ford Shale that’s outcropping (yes, that Eagle Ford) and it’s locally heavy in vertisol clays. Water it good several days before you dig, then give the surface a couple of days to firm up so you’re not digging in muck.
I understand wanting to do it by hand for an eagle scout project, but is that required? You can rent a gas powered auger relatively cheaply from Home Depot.
It really depends. When I built my fence 30+ years ago on one side of the yard I could do 3 to 4 post holes a day. On the other side 3 to 4 days per post hole. Our back yard was an orchard before the houses were built. And it is all clay. So I would say until they start digging no one knows.
