Very fast-draining soil near a well - northern Portugal

I live in northern Portugal where the ground is mostly granite and water drains incredibly fast. In the area I’m considering putting the mulch basin my perk test result is 1cm in 30 seconds.

The location is 20-30 meters from a well and 2-3 meters uphill (on a terrace) from it.

I’m wondering if there is any risk of contamination to the well considering these parameters? Should I not even attempt? Or is there something I can do to mitigate any risk?

Of course I don’t want to take any change to contaminate the water.

Welcome to the forum.

I would suggest that the well would be 50 to 75 feet from grey water.

That also depends on laws where you live.

Anne Miller wrote:Welcome to the forum.

I would suggest that the well would be 50 to 75 feet from grey water.

That also depends on laws where you live.

Thanks! Is the 50-75 feet a general rule? Or it applies to the fast draining soil scenario?

from https://www.housing.qld.gov.au/__data
RECOMMENDED SET BACK DISTANCES FOR GTEY WATER  1 march 2026 revision
Recent feedback from stakeholders indicated that the setback distances contained in Table 2.2 of the QPW
Code were insufficient and would make the containment of greywater within premises more difficult to achieve.
To address this concern amendments to the QPW Code provide for increased minimum setback distances from buildings, boundaries, swimming pools etc.
Set back distance from bores intended for human consumption 30.0