Looking at bringing in a trackhoe to eliminate cattails while the pond is down three feet.
That sounds like a lot of work. Can you hit them with one of the cattail herbicides while you have that 3' safety gap? I think some of the good ones are glyphosate (RoundUp) based, which is considered "non-persistent" in the soil.
You might be able to hit them hard, without herbicide getting directly into the lake.
OTOH, those types of herbicides work best when the plant is actively growing. I don't know if your cattails will hit their spring growth spurt before you get your spring rains.
Maybe experiment on a little patch?
They are currently not growing. I believe the best way to remove them to completely remove the plant. Results are mixed on getting to the root if using herbicides IIRC from reading here.
