Hi. I studied Biology as an undergraduate and I was admitted into Stanford's Structural Engineering and Geomechanics program as a master's student starting in the fall of 2010.
Undergraduate GPA: 2.62
Post-bac coursework in civil engineering GPA: 3.84
GRE Q:720 V:530 W:4
Plus a lot of work experience in structural drafting, and an engineering internship.
The point is that its not just your numbers that matter. Its your application as a whole and whether or not the selection committee feels that you're a good fit for the school. So do your research on the different programs out there.
Cheers.