I wanted to know why an Amtrak bus was the only option on a leg back to Denver from Glenwood Springs in July. Here is their email response:

The Union Pacific Railroad will be carrying out extensive track work this summer and fall east of Glenwood Springs.

Trains 5 and 6, the California Zephyr, originating at Chicago and Emeryville on these dates: June 30 – July 8; July 5 – 23; July 31-August 8; August 15 – 23; August 31- September 8 and September 15 – 23 will detour between Denver and Salt Lake City through Wyoming one day later.

Buses will operate only between Denver, Glenwood Springs and Grand Junction, connecting from train 5 (bus 3505) at Denver, and to train 6 (bus 3506) at Denver.  No alternate transportation will be provided to or from Winter Park, Granby, Green River, Helper, or Provo, and there is no connection to or from the train at Salt Lake City.

We hope that this information is helpful.

You would think a change in service of this magnitude would warrant a note on the Amtrak website.