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Tibble Fork Reservoir is a reservoir located in American Fork Canyon in Utah, United States in the Uinta-Wasatch-Cache National Forest. It is fed by the American Fork River, Deer Creek, and Tibble Creek, and drains into the north fork of the American Fork River.

History
The reservoir was created in 1966 with the completion of an earthen dam, constructed by the North Utah County Water Conservancy District with the assistance of the Natural Resources Conservation Service, as part of the latter's Watershed Program.

In 2004, an NRCS assessment concluded that the now nearly 50-year-old dam did not meet current safety regulations and engineering standards. A 7.3 million-dollar rehabilitation of the dam took place between 2016 and 2017, with a public reopening ceremony for the reservoir held in June 2017. In addition to strengthening the dam and increasing its lifespan, the rehabilitation raised it by 15 feet, increasing the storage capacity of the reservoir from 70 acre feet to 400.

Sediment Discharge
As the reservoir was being drained for the rehabilitation, an unexpectedly large discharge of sediment from the dam occurred on August 20, 2016. This discharge resulted in a mass fish kill along two miles of the north fork of the American Fork River below the dam, with fish being smothered by dark muck that reached above the high-water mark. Elevated metal concentrations had been found in the sediment, but not the water, of the reservoir, originating in former mines upstream of the reservoir.

The discharge prompted the nearby city of Cedar Hills to take soil and water samples, with the results revealing no unsafe levels of metals. In the years following the discharge, some recovery of fish populations in the affected section of river was observed. In 2017, the North Utah County Water Conservancy District was fined $145,000 by the state Division of Water Quality for the discharge incident and its aftermath.