question is in caps below:

realizing that waterproofing can be tricky i wasn't going to trust
myself to diagnos the troubles in my basement. didn't want to remodel
and find out during rainy season i was wrong. so i called in a company
here in the San Francisco Bay area to consult. This company only does
waterproofing. They recommended xypex concentrate for my problem. (I'm
on a hill with part of the basement below grade. I have some seepage
and moisture in the rainy months. the runoff is good around the house,
but apparently hydrostatic pressure is forcing water up through the
holes left from forms. yes, they didn't fill these and they go right
down into earth)

$800 in consulting fees later, i'm now in the prep stage. xypex
requires a porous surface free of non-concrete materials. apparently it
seeps into the porous exposed concrete and forms crystals.
unfortunately i discovered that parts of the 18" foundation wall were
covered with plaster.

ITS SEEMS I NEED TO FIGURE OUT HOW TO REMOVE THE PLASTER FROM THE ROUGH
CEMENT. IT HAS PLENTY OF LITTLE CAVITIES. ITS ABOUT 60 SQ FT. ANY
IDEAS?

i've thought about sandblasters (until i started reading about the
dangers) and grinding wheels with wire brush attachments.

much thanks