History of Flower Creek Dam
The Flower Creek Dam was completed in 1946 for the Pacific Power and Light Company. The City of Libby purchased the dam in 1986. This dam impounds the Upper Flower Creek Reservoir, which continues to serve as a source of high-quality drinking water for the community.
The dam has been inspected approximately every five years since 1980 to comply with the dam safety operating permit issued by the Montana Division of Natural Resources and Conservation (MT-DNRC).
Recent inspections of the dam have revealed structural deficiencies and the potential for loss of human life and loss of the municipal water source in the event of dam failure. The dam is classified as high-hazard by the MT-DNRC.
The dam has historically leaked reservoir water through the construction joints, resulting in a buildup of calcium carbonate on the downstream face. This buildup is likely due to the seepage and dissolution of cements paste. Analysis of the concrete indicates a significant loss of strength within the dam structure.
Following an inspection in 2009 and a subsequent material analysis in 2010, the City of Libby began reviewing options to maintain a safe and reliable water supply for the community. The selection of the Flower Creek Dam Replacement Project is the culmination of extensive studies and cost comparisons, as described in the 2012 Preliminary Engineering Report, available at the City of Libby offices. Many other sources of drinking water were considered, including groundwater and alternate surface waters. The dam-replacement alternative was vetted by the community during various public meetings beginning in April 2011.
The City of Libby will replace the Flower Creek Dam and will maintain approximately the same capacity for water storage in the Upper Flower Creek Reservoir. This project will ensure a continued supply of high-quality drinking water for the community.
The proposed Flower Creek Dam will be located approximately 85 feet downstream of the existing structure. The existing dam will remain in place during construction of the new dam, and will be dismantled upon completion of the dam-replacement project.
The proposed dam will be a gravity dam and will have outlet facilities that will allow for greater control of storage levels and in-stream flows. The total estimated project cost is $8,431,000. The estimated construction period for the dam is Summer 2013 to Fall 2014.
The City of Libby has submitted funding applications to the following programs:
- Treasure State Endowment Program (Grant)
- Department of Natural Resources and Conservation – Renewable Resource Grant
- Montana Department of Commerce – Community Development Block Grant (to be submitted March 2013)
- United States Department of Agriculture – Rural Development (Grant/Loan)
The City may be eligible for up to a 45% grant for the RD portion of the funding with the remaining 55% funding through a low interest loan. This funding is anticipated to be available in late 2013.