From Alpha Centauri Wiki
A Thermal Borehole penetrates to Planet’s mantle and provides significant minerals and energy. Borehole squares provide +6 minerals and +6 energy, but eliminate all nutrient production in the square.
- Boreholes cannot be built adjacent to other boreholes, nor on sloping squares.
- Rivers are cut off by boreholes, but still count towards the energy of the square
- Boreholes are unaffected by fungus
- Boreholes override the minerals offered by the terrain (mineral bonuses still work).
- Boreholes have a significant negative ecological impact.
- Boreholes can still provide nutrients when the square has a nutrient bonus.