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Halligan Water Supply Project

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 Halligan and NISP

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Once permitted, construction of the raised dam will take approximately two years.

The construction will expand the existing reservoir from its current capacity of approximately 6,400 acre-feet to an enlarged capacity of just over 14,500 acre-feet, providing Fort Collins Utilities with 8,100 acre-feet of additional water storage. Achieving this capacity will require raising the current 70-foot dam about 25 feet, creating roughly 130 acres of new inundation at the reservoir.

The existing Halligan Dam is a concrete arch dam. The preliminary plan for enlargement is to raise the existing dam by reinforcing the downstream face with additional concrete, raising the total height with additional concrete, and installing a new multi-level outlet tower. The surface concrete on the dam is weathered and will need to be removed to expose more competent concrete underneath.

The reservoir will be maintained at a low elevation during the construction period. Fort Collins Utilities will use best practices to minimize disturbances during construction and is currently drafting a Conceptual Mitigation Plan that will describe general mitigation approaches that will be used to offset temporary construction impacts.

The current dam undergoes routine inspections and is structurally sound, but it is more than 100 years old and will need to repairs in the coming years regardless of if the Halligan Water Supply Project is approved. If the project is not approved, the burden of repairing the dam will fall to the North Poudre Irrigation Company (NPIC) and subsequently its shareholders.