Simply to make sure I grasp your problem, do you have plants on the edges of your lagoons? If so, the technique to remove them depends on the kind of macrophyte. If you have Typha (cattail) the process will not be the same as if you have Phragmites ( Common reed)? Reeds reproduce mostly by rhizome buds, or rhizome fragments so the process will be very different than for other plants. Also, we will need to know the type of lining of your lagoons.
We had 6 lagoons although one is used for sludge and only two are really used for equalization of flows from the town. Being new to this, I'm wondering how critical it is to remove shrubs and hedges from the berms. We have clay liners installed 1964 and 1965. A budget study on one of the lagoons proved good liner integrity. So is it imperative to remove woody shrubs on the berms? Do their roots cause damage? Thanks!