normal around here (Georgia). The biggest worm I've ever come across falls around your 8" range (and that one freaked me out). That thing is crazy..I guess everything is bigger in Texas! :-)
You might want to call a college or something and have it identified, maybe you made a discovery and they'll name it after you. :-)
I looked around on the web and came across these sightings of big worms in the US:
"United States: The Oregon Worm grows two to three feet long, and it gives off the smell of lilies when handled. It burrows five feet deep and is rarely seen. In fact, there have been no official sightings since the 1980s.
The Giant Palouse was found in Washington State. It grows up to two feet long - about the length of a baseball bat. It hasn't been spotted since 1978. Population growth and development may be to blame."