I assume Canon 70D came after Lr4 was no longer being fitted with new camera support (i.e. when Lr5 was released).
(feel free to double-check that assumption - if wrong, then forget the rest of this post..).
* upgrade to Lr5, or
* convert to DNG (using free Adobe Converter).
Because Lr 4 has no idea what a 70D is - all CR2s are not the same.