Salmon Creek Dam: What a Gold Mine Left Behind

In 1913, a gold mining company in Juneau, Alaska needed year-round power, and the canyon it chose for a dam was narrowest exactly where the water pressure would be highest. The answer was the Salmon Creek Dam, the world's first constant-angle arch dam: six feet thick at the crest, built with about a third less concrete than a conventional arch, and still working more than a century later. In this episode I go to the dam to look at why its geometry worked, why the rock at either end mattered even more, and how a structure built for a mine that closed in 1921 became part of the water and power supply of Alaska's capital. CHAPTERS 0:00 A Dam Built for Gold 0:54 Gold in Juneau 1:47 Bartlett Thane's Power Problem 2:56 Why Hydropower 3:53 How an Arch Dam Works [demo start] The Constant-Angle Arch 7:54 Jorgensen and the Engineers Behind It 8:54 Building It in 1913 12:36 After the Mine Closed 14:06 An Island Grid 15:39 Who Watches the Dam 16:10 Water, Salmon, and a Landmark 16:49 Still Working Since 1914 SOURCES American Society of Civil Engineers, National Historic Civil Engineering Landmark: Salmon Creek Dam (landmark page and site plaque, dedicated 2022) "Constant-Angle Arch Dam of Concrete: The First True Example of the Type," Engineering News Interpretive signage at Salmon Creek Dam Alaska Mining Hall of Fame, Bartlett Lee Thane