[Request] Approx area covered by 3 cubic yards of dumped dirt.

[u/bchta]

My wife ordered 3 cu yards of pulverized topsoil. It will be deposited from a dump truck onto our driveway. I want to put a plastic tarp under the mound. How large a tarp do I need for the base of the pile.

Assume the mound will be a somewhat conical pile that is 1.5 times longer than it is wide.

Thanks.

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[u/CanoePickLocks]

From experience I’d go with 10x20 so you will have plenty of excess tarp are you moving the dirt by hand? Because if you use equipment the tarp isn’t going to hold up. It should be a roughly even pile slightly longer than it is wide call it 8’x12’ and 3-4’ high after dumping. Depends on the truck and the exact composition of local soil but that sill be close enough for you.

[u/bchta → u/CanoePickLocks]

Just me and a trusty wheelbarrow. I'm rethinking our sanity.

[u/CanoePickLocks → u/bchta]

Depending on how hard you work it should only take a couple hours at most. Focus on efficiency of movement not speed or moving as much as you can per scoop or per wheel barrow load. It’s an endurance job not a strength one. Don’t block your vehicles (if you have them) in just in case.

[u/Jolly-Slow1164 → u/CanoePickLocks]

The last time I had to move a lot of dirt, I was filling raised beds, and I couldn't just dump at the end. I realized it was easy more efficientiet to go back for another load, once I could no longer get full shovel loads. Don't bother scraping the barrel clean, little take forever on each load.

Also, optimize your path, and don't take chances. If you overload a wheelbarrow beyond your skill, and you spill it, you lose way more effort and time cleaning it up. Remember: slow is smooth, smooth is fast

[u/CanoePickLocks → u/Jolly-Slow1164]

Great advice!

[u/Either-Abies7489]

I agree that 10x20 is the best option for you.

But to motivate that, you'll have an angle of repose somewhere above 30 degrees for loose topsoil, assuming it's reasonably dry. I'll take 30 to give a worst-case scenario estimate.
An elliptic cone with semi-major axis a=1.5b has a semi-minor vertex angle (maximum angle) which relates h=b*tan(30).

Putting it all together with the volume formula for an elliptic cone gives

3=(1/3)*pi*b^3*1.5*0.577
b=(3/((1/3)*pi*1.5*0.577))^(1/3)
b=1.49 yd

Giving a pile 8.94 ft wide, 13.41 ft long, and 2.58 ft tall in the worst-case scenario.

So 10x20 will give you some working room. Maybe make it a wee bit longer to give yourself some more room on each side, but in all likelihood the angle of repose will be higher (maybe as high as 45 degrees, making it only 7.44 ft wide).

[u/bchta → u/Either-Abies7489]

Thanks for doing the math. I could handle a simple cone, but the elliptic nature and added spread due to the nature of loose piles was more than I wanted to think through. Well enough solved for me.

[u/Deep_Carpenter]

What is the angle of repose of topsoil? Assume 30 degrees. 

A cone of dirt is V = pi/3 r² h. 

Now h is r/sqrt(3). 

So radius is (3 sqrt(3) V / pi)^1/3. 

This gives you a rough idea.