In its final performance report for the year, the company said it loaded 856 coal trains in the region in December versus 1085 trains in December 2011.
Whole year, UP had 10,415 loadings in the SPRB compared to 12,254 in the prior year.
In its other main service area, the Colorado/Utah region, results were anything but sour. UP confirmed 218 trains in December, up slightly year-on-year from 213 in 2011.
Additionally, the 2666 loadings it had for all of 2011 rose to 2704 for 2012.
The shipper had a promising summer before starting its downhill slide in the SPRB. In July the rail shipper reported its best monthly SPRB volume since the start of 2012 with 952 loadings, a 16% jump from 820 loaded in July of last year.
The news got better in August, when the company had a year-to-date high of 974 trains.
However, it was the beginning of the year-on-year downward trend as the total trailed the 1130 trains it reported in August 2011. Results continued to disappoint through the remainder of the year.
UP serves 10 mines in the SPRB, five operations in Colorado and five mines in Utah.
Its total operation area encompasses 23 states in the western two-thirds of the US.
Burlington Northern Santa Fe and UP are the two largest shippers for the western coalfields.