Skills for Underground Construction

[Varyon]

I could see a Digging (HT/E) skill being used, in addition to what's already been noted, in the following functions:

Per-based to notice areas where you shouldn't dig unless you want a collapse to occur (this would also serve as a complementary skill for noticing - or creating - relevant traps).

IQ-based to shore up what you've been digging, stabilizing it against collapse. This is fairly basic, only able to support a fairly short, shallow tunnel - more complex tunnels call for an appropriate flavor of Engineering.

HT-based for its primary use, reducing the rate of fatiguing. By default, digging burns FP at a rate of n per hour, where n is set by the type of ground involved - 1 for loose soil, 2 for ordinary soil, 3 for hard soil, and 4 for rock/stone. The higher resolution option that would be called for to make a Digging skill relevant here would be to change these to rolling against HT every so often to avoid losing 1 FP* - every 30 minutes for loose soil, every 15 minutes for ordinary soil, every 10 minutes for hard soil, and every 7.5 minutes for rock/stone. Digging skill could replace HT for this.

Finally, I'd probably adopt the Trained ST concept from Technical Grappling, using the Fast progression for Digging, to represent trained diggers being able to dig more rapidly - they functionally have higher ST for digging purposes.


As a potential further option, it seems like it should be possible to push yourself to dig faster. The default rules parallel those for Hiking, so pushing yourself paralleling the rules for Running seems appropriate. Jogging means going about twice as fast as Hiking, while Sprinting means going twice as fast as Jogging. Jogging burns through FP at 30x (!!!) the rate of Hiking**, while Sprinting burns through FP at 4x the rate of Jogging. So, you can dig at twice normal speed by instead rolling every minute, 30 seconds, 20 seconds, and 15 seconds, for loose soil, ordinary soil, hard soil, and rock/stone, respectively. You can dig at 4x normal speed by rolling every 15 seconds, 7.5 seconds, 5 seconds, or 2.5 seconds, respectively. Going faster than this would call for Extra Effort.


*This assumes the default rates are appropriate for a character with effective HT of 10 (such that the character will, on average, fail at half the rolls - so losing 1 FP every hour, every 30 minutes, every 20 minutes, and every 15 minutes, respectively).
**Hiking costs a flat 1 FP per hour with no rolling involved, so if you did roll for it you'd be rolling every 30 minutes.