During Feb. of the winter semester, you can obtain a request form from the Academic advisor and you fill it out and handed in to her to change your program. It's best if you change it as early as possible for the Biotech & Chemical Engineering double major because they have at least seven courses per semester and in 3rd year, you are required to take full time classes in the summer. The later you switch, the more behind you will get.
Good luck! ^_^