brushy burm

[trophytkr]

I got a problem that I could use some help on. I was contacted by a home owner that has a burm on a lake. Years ago he planted a purple ground cover flower on the side of the burm. This burm is at least a 45% angle. Since he planted it it has been taken over by a thorny, woody plant that has berries in the fall. I think either buck brush or some sort of wild berry. I need to find a product that can kill this brush. Is there a product that will kill the brush and not kill the flower? I can't think of anything. I told him I would look around but am thinking that I need to use something that will kill everything on the hill side. Also how would you guys price a job like this? The burm is probable about 200 feet long at better than a 45% angle and probably 100 feet to the bottom.:(
Thanks for the imput....Rick...