I haven't done that much research on this but there are several factors why the line didn't operate in the winter. Often mines/mill shut down simply because they froze up. There is a lot of water used in the milling process and none of the mill structures were insulated. Even the Sunnyside Mill in Silverton is largely uninsulated, and they relied on a very large coal fired boiler to keep the place barley tolerable in the winter. Right now, the main water line to the Sunnyside Mill has been frozen solid since after Thanksgiving, and that's a 10 inch line coming out of Arrastra Gulch--it is also the water supply for my office. As mines/mills shut down, the employees took off for Silverton or elsewhere to wait out the winter. And as importantly, though the snowshed protected several hundred of feet possibly at the worst avalanche, there were several miles of unprotected track. I've spent 40 winters here and the snow storms can pound one into total submission, even with great big yellow Tonka toys available for snow removal. Day after day, and sometimes week after week of the worst crappy weather imaginable and the need to get someplace diminishes rapidly. Even the big mills lower down like the Silver Lake would freeze up, and then everyone went home or to the saloons, or whore houses, or all three for the duration.
Fritz