Two rail lines between the Roseville yard and Newcastle

From: "Tom Cluster" tcluster@pacbell.net

I'm a new resident of Lincoln, in Placer County, California. I've been interested in the two rail lines between the Roseville yard and Newcastle. One goes through Clark Tunnel and the other follows what appears to be a more direct route, along old US 40 through Loomis and Penryn. Were these built by competing companies? I'm curious why there would be two lines. I notice that both are in use these days.

—Tom Cluster, Lincoln, CA