Flower Creek Dam assessment up for public review

An environmental assessment evaluating the City of Libby’s plan to replace Flower Creek dam has been released for public review.

The city has applied for funding with the U.S. Department of Agricultural rural utilities service, water and wastewater program, and as part of that application is required to prepare an assessment of the project to evaluate potential environmental effects.

The city plans to replace the 68-year old dam, which holds the city’s drinking water, with a new gravity-type dam 85 feet farther downstream. The estimated cost to construct a new dam is more than $8 million and is expected to take two years to complete.

Construction of the dam was originally set to begin in 2013. However, it was delayed after the U.S. Fish and Wildlife Service rescinded a 2012 comment on the project and asked for a biological assessment of the grizzly bear, Canada lynx and bull trout populations to be completed.

The biological assessment was completed last year and a biological opinion issued in March details possible impacts to bull trout because of the dam project. Both are included in the environmental assessment document.

Bull trout are protected under the Endangered Species Act. The fish are also listed as a Montana state species of concern. The biological opinion includes the U.S. Fish and Wildlife Services  recommendation that the city conduct a feasibility study to determine if a bull trout fish passage should be installed around the lower diversion dam downstream from the current and future dams.

The public comment period runs through May 12. Following that will be a response period based upon the comments submitted.

Mayor Doug Roll said the city is relieved to have finally made it to this point in the process.

“We’re in the comment period so it will be nice to get this done,” he said. “Hopefully it will go well so we can actually begin the funding process.”

Dan Johnson, area specialist with the USDA Rural Development, said any comments would have to be addressed, and if no comments are submitted, then the agency will issue a finding of no significant impact.

A 15-day comment period follows that and then the environmental assessment will be completed. The final processing of the application will be finished at that point, but Johnson was unable to provide a specific timeframe for when the city would be given funding.

“There will be an offer of funding after that point,” Johnson said. “It’s likely it may go to August, but I’m hopeful that we can provide funding before then.”

Roll said the project could go out to bid this summer if the funding process goes smoothly. The city’s engineering firm, Morrison-Maierle, Inc. has already been in contact with contractors that specialize in constructing dams to make them aware of the project so they can be ready to bid when the time comes, he noted.

The replacement of the dam is critical. Morrison-Maierle, the Kalispell-based engineering firm, in 2010 completed a core sample of the arch dam and found that the concrete strength was less than 1,000 pounds per square inch. Typical concrete cores demonstrate strength of 3,000 to 4,000 psi. A report issued in 2011 said the dam would need to be replaced within five years.

Included in the environmental report are mitigation measures expected to address impacts associated with construction, including the access road, dam construction and tear down of the existing dam.

The city plans to construct a new gravity-type dam 85 feet downstream on almost the same footprint of the existing dam.

 Mitigation of temporary dust, siltation and erosion problems during construction will be necessary. Water trucks, road reconstruction, and seeding of disturbed areas will be necessary.  

Morrison-Maierle Inc.’s assessment, which was initially drafted in January 2013, recommended replacement of the dam. The report notes that “given the evidence of initial poor construction practices, significant variability in the condition of the concrete and extremely poor concrete condition, combined with the significant risk to public safety and property” that the dam be replaced.

 The entire environmental assessment document for the project is available at Libby City Hall. Comments should be submitted to the Rural Development office at 3550 Mullan Road, Suite 106, Missoula, MT 59808.