Hanging Flume In need of water for its Dolores Canyon gold claims, the Montrose Placer Mining Company built a thirteen-mile canal and flume to deliver water from the San Migual River. The last five miles of the flume clung to the canyon itself, running along the cliff face just above the "H" in the photo. The flume was constructed between 1888 and 1891. It was four-foot deep, five-foot wide and carried 23,640,000 gallons in a 24 hour period.