Very carefully as the leaves are saw edged.

I have known people set fire to the crown to burn it out. After cutting down the foliage first to about 2ft tall then its a case of a mattock/pick axe etc to try and cut it up and remove it.

Thanks Seaburngirl , I know that it’s a big job . I thought of burning , but the frogs and other little critters are amongst the roots . Perhaps when they are out of there a reluctant use of herbicide ?

Eileen, I was going to suggest that people sometimes take to setting the Pampas grass alight as it seems that this can take place in the wild. There was an occasion at a previous house when a neighbour decided to do just that in a small front garden and it ended up with a visit from the local fire brigade to extinguish the fire.

When I took out a couple, first I cut everything down to about a foot tall using the chainsaw. Then starting at the outer edge I dug pieces out using a fork and a hoe. Tough work, and if you leave a piece behind it will regrow.

As said watch the leaves. The barbs are backward facing so you can put your hand in ok, but rip it apart when pulling your hand out. Been there done that, hurts!
Don't remember the roots being that extensive or deep when we took our huge one out, but it was 2o years ago now.

Get a hedge trimmer and cut it down as close to to the ground as possible and keep it cut down to that level all year so as to starve the plant roots. Fire is not a good idea unless you check your local regulations with regards to that. Since it is so close to your pond weed killer such as glycophosphate is not to be considered at all. As above wear the proper protection.

I completely removed one 3yrs back, it attacked me every time I needed to work near it, I've done it before as I also had one near our pond, both were huge, the first I cut down first creating a lot of mess to clear away but discovered that it was easier to remove if I left the centre growth intact, it gave me some to tug on, I dug down and made a trench all the way round, then I worked my way underneath the roots with a fork, that I had to jump on quite a few times I admit as I garden on clay, the pampas came out without leaving any roots just a huge hole to refill, you need long sleeves , gloves, brute force and determination and an empty waste bin ...If I can do it at my age and being a small person anybody can....Welcome back Driad...