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Volume Survey Uncertainty  

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Dave Karoly
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Did you account for the dirt that left the site on the worker's boots?

That's what my first boss would ask then apply an arbitrary 20% shrinkage factor to the fill.

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Are you measuring dirt or enriched Uranium? Dirt purveyors in Florida sell it by the truckload which is supposed to weigh a certain amount per load. The trucks are weighed prior to leaving the supply source and if they are too light they just spray water on it until it reaches the desired poundage. They know every trick in the book on how to screw contractors needing mass quantities of fill.  

With dirt quantities if you are within 20% yer good. 😎 

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Now another guy is doing it, but I used to have to do an inventory of the different rock and sand stockpiles at 3 asphalt plants monthly. Would measure, use the factors they came up with to convert to tons, then give the numbers to the bean counters.  Usually there was something they didnt agree with, so I just started asking them what they wanted the numbrrs to be.   Some piles were uncompacted, some were driven on, some were just a bunch of dumped loads next to each other. At one time we were going to do a check where they were going to unload a sand barge onto trucks, run them across the scales, the put it all in a separate pile and measure to see how it compared. After I measured it, turned out they had lost count of which trucks dumped in the pile. 

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I kept shooting the man-sand  at the hotmix plant and was being told there was supposed to be quite a bit more than I shot. One day I got a shovel and started digging. I gave up and got the guy with a backhoe to come dig a hole. They had been driving on 3 foot of man-sand. I had no idea where the bottom was, I was just doing like the original poster and using the toe of slope for the bottom. I have tried since then to get them to let me shoot the bottom before the first pile is delivered but it never happens.

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I'm not sure what you need to do with this uncertainly calculations, but as other's have said volume for piles is dependent on many factors.

I would not use that calculation outside the office. It is basically meaningless with respect to the actual volume of material in a pile where compaction, voids, water, ect…...all play a bigger role.

The best you can do is have some independent checks.

Stating that you are within X.X% of reality is not particularly useful and could be one of those gotcha statements.

Well I say I'm within 2% and the load counts find that you are off 16%, which is real?

It's the old fight over volume of dirt, I'm sure almost everyone here has experienced it in some fashion.

I would argue that photo surveys are the way to do these, then you have checks outside the area of the pile, you can give out elevations for locations that are undisturbed even after the pile has been removed and let someone else check your elevations at that position.


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