Load limits and old bridges
November 12, 2010
When I began driving, Pitkin County posted its bridge load-limits in tons. I drove a very heavy Buick, but paid little attention to the signs until my father told me about his 1930 journey from Denver to Aspen. At first his story intrigued me just because of the chosen route. There was no Vail Pass in those days. There was no Eisenhower Tunnel, either. My interest increased further when he told me about his bridge crossings.
The Midnight Mine constructed a mill in 1930. The company had spent a dozen years tunneling and exploring along the Castle Creek fault line between Queens Gulch and the Little Annie Basin. The mine workings eventually connected, at a lower level, to an ore vein that had been a major producer decades before. Sufficient silver was found there to warrant building a modern mill.
The new multi-story mill housed crushing machines that reduced rock to powder. It held flotation vats that separated minerals from waste. Miners and mules pulled tons of ore through the two-mile tunnel, exiting into Queens Gulch. They unloaded onto a conveyor belt that carried the ore to the top of the building. Gravity guided the material through various processing stages as it passed to the bottom of the mill.
Most of the mill’s machinery was assembled at the site. The accumulated parts weighed tons, but no single part weighed more than what several men could carry – except for the rod mill. The cylindrical-shaped rod mill, about the size of a septic tank, was manufactured in Denver from very thick cast iron. Packed with iron rods, it weighed tons.
The Midnight operators decided to haul it to Aspen from Denver on their four-wheel-drive Coleman truck, rather than have it shipped by rail. That way, once it arrived in Aspen, they would not have to find a way to transfer the heavy load from the rail car to a truck. My father had relished driving that Coleman from Chicago to Aspen after it was purchased; now he was assigned the less-enjoyable task of fetching the rod mill.
The Coleman truck was designed to haul heavy loads and to climb steep grades with its four-wheel-drive and low gear ratios. Tough as a truck could be, it was made from thick steel, packing more mass than most other vehicles of the time. The combined weight of the truck plus the rod mill could easily collapse Colorado’s bridges, many of which were built in the horse-and-buggy days. Father approached every bridge with suspicion. He paused to complete a visual inspection beneath every structure. When bridges appeared to be clearly insufficient, he backtracked to find an alternate route. But there were only so many roads to choose from when traveling from Denver to Aspen.
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Fortunately, the journey occurred in late fall, when stream levels were their lowest. Instead of crossing on a questionable bridge, he sometimes chose to ford the stream slowly, hoping he would not get stuck. Some bridges presented only one way forward: crossing the dubious bridge.
A mental debate ensued: Would it be better to roar quickly across the bridge or creep across it carefully? Father took the youthful approach: “just drive like hell.” Father was too focused on speeding across to notice, but his accomplice, Benny Smith, who would be stationed at each bridge’s edge, reported significant roadbed bowing during several crossings.
Spilling a pile of cast iron into a stream would have been embarrassing, but destroying a bridge would have been a costly catastrophe. The bridges held.
The last leg of the journey reached from Castle Creek up Queens Gulch to the mine. The company constructed a new road for the mill. The old road that traveled up the bottom of the gulch was too steep for trucks with loads. The new road incorporated switchbacks, especially near the mill building. One of the switchbacks turned with a radius that was too tight for the Coleman truck. The driver had to start the turn on a steep grade, then back up a few feet, turn a little more, and repeat that maneuver several times before continuing up the road. That nerve-racking turn with the rod mill was accomplished with the aid of several foot soldiers who jammed blocks of wood behind the wheels to prevent the truck from going out of control during the downhill backing. Denver to the Midnight – three days.
Even now, I seldom drive past those bridge load-limit signs without hesitating, at least mentally, before crossing.