A powerful man-made jet of water blasted the mountainside…

…washing soil and loose rock downslope to fill in the trestle.

By 1911, the Milwaukee Road filled twenty-two temporary wooden trestles between St. Regis, Montana and Avery, Idaho. On this side of the Bitterroot Mountains, two water flumes provided water for "sluicing" these bridges.

Others were filled by dumping material from train cars. You will have to look carefully to see where the sluicing removed the topsoil on the hillsides because the remarkably resilient forest has largely healed the old scars.

With a mighty jet of water, a powerful water cannon called a “Giant” or “monitor” loosened earth and rock from the mountainside above the trestle. Water from a nearby stream ran down a flume into storage tanks several hundred feet above the Giant. Gravity forced the water down a 12-inch diameter pipe and out a 4-inch nozzle. The cannon had no trouble washing great quantities of material from the mountainside.