Posted: 25/07/2015 at 10:26
It will be hard work and you will need to wear protective clothing as pampas grass has extremely sharp edges. It is also tricky to dispose of as it doesn't rot down quickly in a compost heap and will wrap itself around the internals of a shredder.
I had one with a metre diameter base right next to a fence. I cut it down to the ground using a chainsaw and then treated any regrowth with a glyphosate based weedkiller. It was dead in about a year. The 'stump' was then dug out using a sharp spade, pick-axe, mattock, pruning saw and copious quantities of painkiller for my back. It doesn't need any of the type of weedkiller which will poison your soil to stop regrowth - that's not a big problem with pampas grass.
If you are fit you should be able to do it yourself in the same way, if not, consider paying a professional to get rid of it for you including removing the roots using a stump grinder. If you can afford to do that, get several quotations. The same firms which remove hedges will be able to do it.