# Thread: Need volume of site detention pond

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## Need volume of site detention pond

I have a toposurface shaped with a depression area for storm water dentention. I need to know the volume of water that the depression will hold before the water spills over the edges. Is there any way to calculate this?

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## Re: Need volume of site detention pond

Not automatically, I would just do an average based on the area * the average depth.

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## Re: Need volume of site detention pond

Well I tried to do a pad to give me the volume below it, but for some reason my pads are not reporting the correct volume.

To test it, I made a pad 5 feet by 5 feet, and the average depth of the fill below the pad is around 1.5 feet. 1.5x5x5 should be 37.5 cubic feet, but Revit is only reporting around 6.5 cubic feet for that area of fill below the pad. The surface area of the pad top itself is 25 square feet, so why would the volume only show up as 6.5 cu ft.?

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## Re: Need volume of site detention pond

Nevermind, I had something set wrong before.

So a pad works for determining the volume of water in a certain area of your topography. I needed to find the volume up to a particular elevation, and my pad is 1 foot thick, so I set the pad elevation as 1 foot higher than the contour line and traced that contour line as my pad outline.

Then I just selected the earth fill below the pad and it reports the volume.

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## Re: Need volume of site detention pond

Wow, I'm surprised that works unless the walls of the pond are vertical.

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## Re: Need volume of site detention pond

The bottom of the pad was set to the upper-most contour line around the pond. Any higher and the water will be spilling over the berm. So the filled area of earth below the pad is equal to the volume of water the pond can hold.

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## Re: Need volume of site detention pond

I used a mass pyramid - worked for me.

Regards

DB

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## Re: Need volume of site detention pond

Use the orignal topo as the existing, create your duplicate, delete the points inside the boundary of the pond edge, set points around the perimeter of the pond that are just below the corresponding contour around the pond and finish the sketch. The net fill should be your volume.
If there are only the perimeter points for the pond then the interior of the pond should be level.

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## Re: Need volume of site detention pond

Originally Posted by Dimitri Harvalias
Use the orignal topo as the existing, create your duplicate, delete the points inside the boundary of the pond edge, set points around the perimeter of the pond that are just below the corresponding contour around the pond and finish the sketch. The net fill should be your volume.
If there are only the perimeter points for the pond then the interior of the pond should be level.
I dunno, the topo was already graded from the existing, so it's actually the New topo that has the detention pond.

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## Re: Need volume of site detention pond

You could try copying it out to another project and using the new topo as the existing

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