3D polygons and Breaklines

[JeremiahTamagna-Darr1]

I am working with Terrain data and relatively new to the process.  We have Elevation data in First Return, Last Return, and BE ASCII files.  I would like to create a terrain dataset but have been having problems with breaklines.  I have roads/buildings/streambanks, but those have been stored as 2D features.  Does anyone have recommendations on how to use those best as functional breaklines, and how to capture elevation values on the features if they need Z values to operate as breaklines.

[JeffreySwain]

You could use another DEM and then utilize the interpolate shape tool to make the lines 3d.  The caveat is that now you are using another DEM that may or may not match up to the time frame of your lidar data.  This may cause some interesting effects where the breaklines and the lidar meet, but there is no way to not derive the elevation of the lines from either the new terrain, which will not create much effect or use the other data, which might have a large effect.