The contours are AEC Proxy Objects so you'll need to explode them first. Then import center to center. After that you can acquire the coordinate system of the dwg file via Tools > Shared Coordinates > Acquire Coordinates > Select the dwg.
Now, don't model the house in the site project file since the contours are nearly a mile high. Build the house in a separate file and then link the house into the site, move it up to the desired elevation in a section view and position it on the site as needed. Then publish the coordinates to the building file.
See how far this gets you
You can refer to this
article.