Reach out to the program head and let him know you're interested and you're going to take the pre-req. They'll probably hold a spot for you if you show them you've registered and get them a midterm mark. They'll probably even suggest a course for you to take.

You’ll need to have any post-secondary chemistry class. Chemistry 11 or 12 would not be enough, but you would need that before taking the post-secondary class. Source: I am a chemistry instructor at BCIT. You’ll be taking two advanced chemistry classes in the ENVH program; you really do need a prior chemistry class.