Creating project in one drive filled up space on another drive

I created a project, on my D: Drive, using the new Art, Fashion, Automotive Galleries and Showcases free content on the Marketplace. As soon as it loaded, I got a memory warning on my C: Drive. By chance I happened to have checked my C: Drive space right before I opened this project, and I lost over 30GB. I checked my Epic Vault Cache settings, and it is pointed at my D: Drive already. What could account for this massive loss of memory space? Shaders or something? I am trying to have everything pointing on my D: Drive since my C: Drive has limited space.