Northern Water announced Thursday that naturally occurring uranium has been found in rocks quarried at its Chimney Hollow Reservoir construction site, and that the contaminant will leach into the water as the reservoir begins to fill.

The news comes just months before Northern had hoped to begin filling the new storage pool west of Carter Lake in Larimer County.

“The uranium at Chimney Hollow is naturally occurring in the granitic rock formations that were quarried to supply material for the dam. As the reservoir fills, these rocks will be in direct contact with water, leading to the leaching of uranium into the water. This issue will initially require close monitoring and management when filling Chimney Hollow Reservoir,” the agency said in a statement.

The finding was unexpected, said

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