History of Lower Flower Creek Diversion
The Lower Flower Creek Diversion diverts water into the raw water transmission main. This main was reconstructed in the mid-1950s to mid-1960s and in 1980. This main conveys water by gravity to the Libby Water Treatment Plant. The components at the Lower Flower Creek Diversion include the diversion structure, intake structure, holding tank and two spillways.
The Lower Flower Creek Diversion was rehabilitated in 1995 with the following improvements:
- Grouted the principal spillway to eliminate leakage.
- Extended the diversion structure across the full width of the stream channel.
- Reconstructed the auxiliary spillway.
- Constructed a catwalk over the principal spillway.
- Dredged sediments collected in reservoir.
- Capped the concrete core wall.
A site visit in February 2012 confirmed that an eroded depression remains just upstream of the principal spillway. In 2011, City crews placed dye in the depression and found that the water was following a path underneath the diversion structure and surfacing in the streambed below the structure. Fine soil materials have likely been washed from the soil formation, and the voids are allowing water to pass under the spillway structure. City crews have had marginal success sealing the conduit with bentonite clay.
The City of Libby will rehabilitate the Lower Flower Creek Diversion and maintain this reservoir as a diversion facility to the raw water main. This project will ensure a reliable source of raw water for the Libby Water Treatment Facility.
This proposed project includes drilling and excavating into the voids and pressure-grouting a Portland cement grout to seal the voids. The total estimated project cost is $125,000. The estimated construction start date for the diversion rehabilitation is April 2013.
The City of Libby has submitted a funding application to the United States Department of Agriculture – Rural Development. The City may be eligible for up to 45% grant funding for this project with the remaining 55% funding through a low interest loan. This funding is anticipated to be available in late 2012.