You have received some advice on what might work. I'd suggest you get some professional help by talking to a local geotechnical engineer. Give them the details and let them figure out what is the best way to approach it. You could spend a fair amount of money trying an inappropriate technique...
I'm doing a presentation on soil nailing at a local Geotechnical seminar soon (March 2) - wondering if anyone has any experience with using soil nailing in an area where there is groundwater seepage, and if so, what measures were taken to control groundwater?
