Creating boundary for surface

Hi there,

I'm using AutoCAD Civil 3D 2010 to create a surface of a stockpile to compute its volume compared to a surface I created of existing topography. I create a surface then add contours by selecting all the contours in the stockpile area. This creates a tin surface of not just the stockpile but of whatever contours are both in and outside of it. To correct this I've tried making a 3dpoly as a boundary and making each point snap to a contour which provides a more reasonable perimeter base. With large stockpiles drawing this 3dpoly from point to point all the way around takes time to do and if I stop it midway I can't join the next segment together like polylines can. Is there a better way to do all this?

In fact, if the boundary is not connected, i.e. I use 2 or more 3dpoly's to create the boundary, then an error message occurs saying too many points are picked for the boundary.

You don't have to use a 3d poly. The PL does not have to drape along the surface so you can use a simple 2dpoly.