Flower Creek Dam replacement going according to plan

At the Flower Creek dam site, the construction of the new dam may not be in full swing, but the stage is set and work is underway.

On Wednesday, an excavation team was making a road down to the dam where about 20 feet of earth has been removed from the spillway side of the dam and then hauled to the upper staging area. The staging area was created by Libby city employees and held a couple of field offices, an excavator and several lengths of pipe.

Deconstruction of the dam is in its nascent stages. “We started taking out some of the catwalk yesterday,” said C.R. Leisinger of Morrison-Maierle, the engineering firm on the job. “They’re planning on digging down to the creek then putting bypass piping in to divert the creek around the work area. Then they’ll start excavating on the other side,” he said.

Leisinger noted that so far the digging has gone well with few large rocks impeding progress.

City Administrator Jim Hammons said the city plans on salvaging all usable materials as the dam is deconstructed, which is part of the dam contract. He pointed to the metal stairs that once led to the catwalk as one such item the city will repurpose.

Installing the bypass pipe will be done in two stages and will become part of the dam structure as it gets built. That phase of the operation will get started next week.

The water level at the dam is at creek level now, after slowly drawing down the water at a rate of about 18 inches a day. Corky Pape, supervisor for street and water distribution, said city workers were constantly running between the two dams during the draw-down to make sure everything went as planned.

At the diversion dam at a lower section of the creek, city workers had recently finished digging up the transmission pipe that runs to Libby’s Water Treatment Plant. Crews started digging up the pipe on Thursday and finished on Tuesday.

Pape said the pipe was deeper than they had anticipated, which made digging up the pipe a bit stressful. The pipe is the main line providing water to the city. The pipe will get an extension and a manhole cover to make future access easier.

The line had to be dug up so Morrison-Maierle could tap the line to inject sodium permanganate solution into the system if a rush of organic material is dislodged during deconstruction of the dam. There has been no cause to use the solution as yet.

A temporary heated shed at the diversion dam has a backup generator and several creek-booms to be used if spills of any kind happen during the project.

Hammons said the project is coming along well so far. “It’s going good, they’re moving dirt and a lot of it, which is the biggest thing they can be doing right now. So when weather improves things can get going.”

Johnson Wilson Constructors is the company overseeing the Flower Creek Dam project. Their bid was about $7.4 million and a finish date for the project is slated for November 2015.