Gophers in the crawlspace

I have a project I'm working on out in west Sonoma County where water was getting trapped under the crawlspace causing mold growth on the subfloor and framing, and resulting in elevated mold spore levels inside the house. The home was built in the 1930's and, at that time, it was constructed on a raised foundation with at least two feet of clearance under the house. Today, the clearance under the house is about 6 inches because gophers and moles have been tunneling and piling up dirt for over 70 years. The level of the ground inside the crawlspace is about 18" higher than outside the foundation. The owner has had two laborers digging out the crawlspace for 4 days and is about half way done. I have never seen anything like this before.