Overgrown Bamboo
Another method is to dig a trench around the bamboo and leave it open. You can inspect the trench regularly and cut any underground rhizomes trying to cross over. Other people have used this method but filled the trench with gravel or mulch. Then each fall a shovel is thrust down into the trench, going all around the grove, pruning any rhizomes that are crossing the ditch. I am aware of several people using this method quite effectively.
The other day I thought of building wooden beds to plant the bory bamboo in. After a little research, I found a good article on how to build raised beds. The author, Kelly Wood is actually from here in Portland, Oregon.