It could work, but it might take too much time. I know some of the freed Ophiuchus are contaminated, but not who among the blanks -- it can be subtle. We'll probably have to assume Anchor is, and hope that we can move quickly enough that it doesn't affect him too badly.
More importantly, how portable is your garden? Can we move it elsewhere? I can lay wards against wildlife if need be, and if we have to leave the dorms...