Wednesday, August 31, 2011

The Powder River Basin

The Powder River Basin, primarily in northeast Wyoming but also extending into southeast Montana, is the largest single source of freight rail tonnage in the United States. The region's low-sulfur coal has grown very popular as electric utilities try to clean up the exhaust from their power plants. The fuel gets shipped all across the country, though it appears to be most heavily used in the Midwest.

While I'm often amazed by the level of freight rail traffic that goes past my apartment every day, this makes me wonder how many trains must be running those rails out west at the same time. However, while the thickness of lines on the map above make it look like there must be ten times as many trains there compared to what goes through my neighborhood, the reality is that the line only carries about 3x as many trains. Still, BNSF and Union Pacific have put together their impressive Joint Line with four main tracks (plus sidings!) through the heart of cowboy country to haul a lot of long and heavy trains:

BNSF 9884 Converse Jct BNSF 6336 Powder River
Photos copyright Shawn Christie.

The tonnage that goes through my neighborhood is about the same as the northernmost line on the map, the old Great Northern mainline from the Twin Cities to the Pacific Northwest. That works out to 50–60 trains per day, often composed of well cars with double-stack containers, although there are still many regular mixed freight trains on the line too.

In the Powder River Basin, BNSF claims slightly more than 50 loadings per day, while Union Pacific claims more than 30. This presumably adds up to 160 trains per day if a "loading" means an inbound empty train plus a full outbound one. The trains are averaging a length of 132 cars, which each carry more than 100 tons of coal. If this amount of coal had to be moved by truck instead of by rail, it'd amount to between 81,000 and 86,000 semi truck loads per day (imagine the parkway portion of Interstate 35E southwest of downtown Saint Paul, but with every vehicle a truck).

Of course, even with that many trains, the four-track mainline probably wouldn't need to be as wide if the trains could run at regular speeds—BNSF's double-tracked Southern Transcon sees about 100 trains per day and supposedly has capacity for 150 (though I think there are still a few choke points which prevent that from happening). In the PRB, however, trains are often forced to crawl their way out of the basin at low speed, necessitating the extra rails.

Incidentally, while it is heavy, Powder River coal is known for blowing away as it gets transported. BNSF itself has said that between 500 and 2000 pounds of coal dust can disappear from each rail car in transit from the mine to the ultimate destination. Some other studies have even said the loss can amount to 3% (>6000 lbs.) per car! The railroad itself doesn't like the coal dust, since it can foul the trackbed and cause it to shift, so there have been some attempts to get shippers to cover the loads with tarps or sealants. They don't entirely fix the problem, but do reduce it significantly.

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