Nils F. Ambursen
Early life and education
|This section needs references.
Working for the B.F. Sturtevant Company in Hyde Park, Boston, Massachusetts, in 1903, Ambursen developed an innovative concrete slab and buttress dam for an industrial client in Theresa, New York. Ambursen promptly filed a patent on his own behalf and organized the Ambursen Hydraulic Construction Company, based in Boston.
Ambursen's concrete-slab-and-buttress design used far less material than a traditional gravity dam making it both a significant engineering advance and cost effective for clients. The record-breaking 41-meter-tall (135-foot) La Prele Dam in remote eastern Wyoming used 43 percent less concrete than an equivalent concrete gravity dam. The structure allowed an interior hollow under the spillway; the 1907 Bloede's Dam on the Patapsco River in Maryland housed its hydroelectric power plant inside that hollow and therefore "under water".
From 1903 through 1917, the company used the technique to construct more than one hundred dams in North America, most in New England. The company sued to preserve its patents fairly aggressively but with mixed success. In some cases, the Ambursen dam became a more generic "Ambursen type", for instance at the 1911 Lock and Dam No. 1 on the Upper Mississippi River between Minneapolis and Saint Paul, Minnesota. Civil engineer George Freeman received his own November 1912 patent on a modified version of the concrete buttress dam used there.
In 1917 Ambursen left his company, which has continued to bear his name for over a hundred years.
Ambursen's designs include:
(all dams listed located in the United States)
- Warrior Ridge Dam (1906) – Huntingdon County, Pennsylvania; "the focus of widespread attention in the engineering press"
- Ellsworth Dam (1907) – Ellsworth, Maine
- Bloede's Dam (1907) – Ilchester, Maryland
- Ashley Dam (1907-1908; undermined 1909) – Pittsfield, Massachusetts
- La Prele Dam (1908–1909; refurbished in 1977) – near Douglas, Wyoming
- Rapidan Dam (1910)– Blue Earth River, Rapidan Township, Minnesota
- Mill River Dam (1911) – Estacada, Oregon; on the National Register of Historic Places
- Powersite Dam (1911–1913)– Forsyth, Missouri
- Overholser Dam (1917–1918) – Oklahoma City, Oklahoma; on the National Register of Historic Places
- Remmel Dam (1924) – impounding Lake Catherine, Jones Mill, Arkansas; on the National Register of Historic Places
- . National Park Service.
- Jackson, Donald Conrad. Building the Ultimate Dam: John S. Eastwood and the Control of Water in the West. p. 295.
- . Library of Congress.
- . Library of Congress.
- Jackson, Donald C. Great American Bridges and Dams. p. 88.
- Engineering News-Record. Volume 62. April 1, 1909. p. 345.
- Blue Earth County, Minnesota. Blue Earth County Historical Society. p. 86].