Calculate the volume within a TIN domain

1. Use the TIN Domain tool (3D Analyst Tools > From TIN) to generate the border of the TIN.

2. Use the Create TIN tool (3D Analyst Tools > TIN Management) to generate the surface from the border (i.e., the top/bottom TIN).

3. Use the Surface Difference tool (3D Analyst Tools > Terrain and TIN Surface) to calculate the volume between the two TINs. The volume is displayed in the attribute table of the output feature class.

Note:
If the border of the TIN has the same elevation, the volume can be directly calculated using the Surface Volume tool (3D Analyst Tools > Functional Surface).