Chimney Hollow Reservoir Project Final Asphalt Placement July 2025

After 1,000 days, 3.3 million work hours and 512 lifts encompassing 200 miles of asphalt paving, a huge milestone was reached on Friday, July 18, as crews placed the final lift of asphalt, which is a full layer across the width of the dam. The first lift was placed on Oct. 15, 2022. Crews will wrap up the remaining work on the main dam over the next couple weeks, which includes completing the remaining rockfill, placing a thin road base layer across the top and finalizing the equipment installation in the dam. Other construction components are also nearing completion.

Engineers and scientists at Northern Water continue to explore potential options related to the discovery of mineralized uranium traced back to the on-site quarry that supplied material for the main dam embankment.

The first water is expected to be stored in the reservoir this fall, with a small initial volume sufficient to proceed with dam commissioning requirements and coupled with water quality monitoring to collect additional information about the leaching process. This data will further inform assessments, management and mitigation options under consideration. No water will be delivered from the dam until assessments are complete.

Northern Water has published a list of frequently asked questions and answers regarding the presence of mineralized uranium.