Nick Bazebahl and the Mining Tunnels — Debra Chapoton

NICK BAZEBAHL AND THE MINING TUNNELS is book 4 in the TUNNELS series.
Sliding into the Old West from their space adventure is quite a shock, but Nick and Samantha adapt quickly. Gold, dynamite, stagecoach villains and an Indian princess are just a few of the surprises in store for these kids in book 4 of the TUNNELS series.
Sliding down tunnels to get in and out of danger and excitement has kept Nick and Sam moving through mission after mission before. But this time the tunnels aren't appearing on schedule and they have no supplies with them to help.