Volume Comparison for New Clearwell

[Anonymous]

I have a fairly level existing site where a proposed new circular clearwell is going to be built. The contractor will need to excavate roughly 20 feet down to bottom slab elevation and slope excavation slopes at a 1.5:1. 

My question is, What would be the best way to determine how much soil will be leftover after exvation, construction, and finished grade is established?

My goal is to be able to create a comparison volume surface between excavation and finsihed grades, but I need to account for the volume of the clearwell. I have attached an image of the preliminary site.

[tcorey]

The contractor will excavate using 1.5:1 slopes, but the well will be built with vertical slopes and then you will backfill from the 1.5:1 slopes to the vertical slopes? Am I understanding you correctly? And you want to know the volume of that backfill?

[Anonymous]

Yes that is correct. Finished grade around the clearwell is the same elevation grading out to exisitng ground. I have an excavated surface and finished grade surface now but when I compare them it wdoesnt take into account the volume of the clearwell underground.

[wfberry]

 Are you asking how to calculate the volume of a cylinder?

Bill

[Anonymous · Accepted solution]

Couldnt you just create a volume surface between the excavated surface and the finished surface, then apply a "hide" surface boundary (the extent of the clearwell) to the volume surface? 

[neilyj666]

And do a check as suggested by Bill to see if it is correct?

[Anonymous]

Thanks Luke that was the trick. What would be the best way to "check" it to make sure?

[neilyj666]

Refer to my reply

[Anonymous]

I understand how to calculate the volume of cylinder. See the image attached.

I am trying to find the best way to use a comparison surface to find the amount of fill it will require to complete the grading. 

[neilyj666]

Are you trying to find the volume of the red area?

[Anonymous]

Yes that is correct. I have a surface for the excavation and for the proposed grading.

[neilyj666]

Add the clearwell boundary circle as a hide boundary (non destructive) to both the excavation and proposed surfaces and then do a volume surface or just a simple comparison.

Use MAPCLEAN to convert the circle to a polyline and use a small mid ordinate when adding to surfaces

[neilyj666]

Although may be better practice to paste the excavation and proposed surfaces to new surfaces and then add the hide boundaries to these copied surfaces. Any changes to the excavation or proposed surfaces will then be dynamically updated as will the volumes

[Anonymous]

Yeah thats exactly what I did, and the number is reasonable, I'm just not sure the best way to check that value (or a good way to view that comparison surface).