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North Fork Dam improvement project, North Carolina, USA

North Fork Dam is located near the City of Asheville in Black Mountain, NC, on the North Fork of the Swannanoa river.

Built in 1952 for water supply purposes, it is owned, operated and maintained by the City of Asheville.

Project features include the main dam, saddle dam, gated spillway and new auxiliary spillway equipped with semi-labyrinth shaped reinforced concrete Fusegates.

The dam is classified as high hazard, since the current discharge capacity of the spillway is inadequate and the dam would be overtopped for floods more than 60% of the PMP.

In order to pass the PMF below the Maximum Water Level, a 200 ft wide auxiliary spillway with a broad crested weir will be constructed between the main and saddle dams. The new spillway will include a bridge overpassing the weir, which will be supported by three 6 ft wide piers dividing the spillway sill in four 50 ft wide bays, and extending downstream of the sill. The piers will also contain hollow sections to accommodate the inlet wells and interconnecting pipes of Fusegates. There will be 2 Fusegates at each of the 4 bays with a height of 16 ft and width of 25 ft.

The Fusegate solution allowed for minimizing the dimensions of the new spillway while offering a reliable and low maintenance spillway control system.