The town's website says the site developer wanted to relocate the balloon track, but it was not feasible. So the loop track stays.
"Following the adoption of the 2009 Railyard Master Plan the developer continued to refine site and building layouts, permitting, project costs and terms with Union Pacific Railroad. However, it became clear during this time that relocation of the
balloon track—a major existing site constraint—would not be feasible and was no longer the preferred option."
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www.townoftruckee.com]