You are here

Hoopes Reservoir Dam (Old Mill Stream Dam)

-A A +A
Old Mill Stream Dam
1929–1932, E. G. Manahan for Fuller and McClintock, engineers, with W. Compton Wills. Visible from Barley Mill Rd., northwest of Rolling Mill Rd.
  • Hoopes Reservoir Dam (old Mill Stream Dam) (Hagley Museum and Library)

Drought-prone Wilmington needed a storage reservoir, so scenic Mill Stream Valley was dammed, destroying a colonial mill (1732 datestone) that T. Coleman du Pont had restored and enlarged (c. 1908). Local soils proved inadequate for an earthen dam, so 105,000 cubic yards of concrete were used instead. Poured in 1930 by contractors from Long Island, the structure was 135 feet high, 90 feet thick at the base, and 900 feet long. A hopper-bottom railroad car delivered cement from Hercules Cement Company. The material was pumped 2,000 feet from the railroad siding to a concrete mixer, from which conveyor belts carried it up the hillside to the dam. The structure is V-shaped to take best advantage of underlying rock layers. The reservoir was not needed until 1941, but water consumption has increased enormously since then, making it critical today.

Writing Credits

W. Barksdale Maynard


What's Nearby


W. Barksdale Maynard, "Hoopes Reservoir Dam (Old Mill Stream Dam)", [Wilmington, Delaware], SAH Archipedia, eds. Gabrielle Esperdy and Karen Kingsley, Charlottesville: UVaP, 2012—,

Print Source

Cover: Buildings of Delaware

Buildings of Delaware, W. Barksdale Maynard. Charlottesville: University of Virginia Press, 2008, 78-79.

If SAH Archipedia has been useful to you, please consider supporting it.

SAH Archipedia tells the story of the United States through its buildings, landscapes, and cities. This freely available resource empowers the public with authoritative knowledge that deepens their understanding and appreciation of the built environment. But the Society of Architectural Historians, which created SAH Archipedia with University of Virginia Press, needs your support to maintain the high-caliber research, writing, photography, cartography, editing, design, and programming that make SAH Archipedia a trusted online resource available to all who value the history of place, heritage tourism, and learning.