----------------------------Original message----------------------------
My experience with ArcTIN is 2-D vector features can be used to define
breaklines (force the creation of triangle edges), with the z assigned
through linear interpolation.   Altlhough this may not be a "true"
representation of the z along such features, It does force the TIN  to
account for these features in its representation of the surface.    You can
probably create a coverage in ArcINFO, with the z's as an attribute of the
linear features by ungenerating the tin(which creates to generate files,
 mass points and breaklines).
 
 
ed d'sousa