We drilled a few holes using either a coring or an auger bit that was powered by a two-stroke Backpack drill. This setup allowed us to sample both small cores and cuttings from various depths which Lisa then collected in labelled zip lock bags for post analysis.
We soon found that a rotary-only drill would not get us as deep as we originally planned because of the underlying hard rock, possibly such as the one in the image below. The maximum depth we reached was 36 inches in one of the four holes (others were between 5 and 14 inches deep). We decided to return tomorrow with a Hilti drill which would allow us to use rotary with percussion to acquire cuttings from a greater depth (down to 1.5m).