Mesh or surface to solid

Hi everybody!

Please help me with this: I just cannot find the way how to convert this two meshes into a single solid. Can someone please explain how to do this. This is actually a bauxite deposit that I'm modelling. The mesh is from Power Inroads SS3 and it was created by triangulating elements (data) from a borehole.

Microstation V8i SS3

Regards!

Branimir

Deposit_Model.dgn