Delete Triangles from Survey Generated Terrain

The delete triangle or edit terrain model tools do not seem to work on Terrain Models generated by the Survey data import.  Typically survey data has interpolated triangulation that required editing.  The terrain model edge methods only get part of the needed clean up.  We would typically go into a survey DTM and clean up all the extra triangles around the edge the sliver method seems be doing nothing to eliminate any of the extra triangles. How do we delete the extraneous triangles from a survey generated Terrain model?

In the past we would go around and clean up the extra edge triangles that were generated and the use the perimeter display to generate and exterior boundary.