I purchased your excellent book Welcome to Pump Track Nation v2 (hardcover) because my son and I are building a pump track in our backyard. I was wondering if I could ask you a question. I’ve gotten a dirt sample from a friend who’s got an excavator and can deliver it to me. I did your ball jar dirt test, and while I clearly see the clay (62.5%) it’s above another layer (37.5%), which is undifferentiated. I can’t figure out, by looking at your photo in the book, whether that bottom layer sand or silt. Or could it be both? If you could check out this photo and let me know what you think, I would be super grateful! (I wish I lived in Boulder so I could take one of your lessons – I may head out that way next summer anyways, so I might be able to squeeze one in). Also, I live in VT, is 62.5% clay too much for an environment where it can rain a fair amount?
It’s hard to tell what that other material is. The good news is, that much clay will overwhelm everything else and make the surface very clay-ey.
You can make a great track out of this (it’ll pack to any shape you want), but you won’t be able to ride it when it’s wet.
I hope this helps,