Disclaimer: This is more construction than engineering question.

I need to drill caissons with approx. 5m total depth.
On site the conditions were found as per the picture, the caissons land right in the middle of a steep rock slope.

Is there any drilling equipment or technique that would be able to achieve drilling through this surface?
The BG25 drill rig with sectional liners was the intended equipment to drill however I believe it will kick off-center and be unable to drill vertically on the sloped rock profile. The only alternative I can think is to hoe-ram down to make a horizontal surface and then start drilling.

note that a flat rock shelf is approx. 3m depth.

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