City mulls Flower Creek Dam options

The City of Libby has taken the first

step towards finding a solution for Flower Creek Dam.

Thursday the City Council directed its

engineer Morrison-Maierle to begin a cost analysis of the survey

work that would be needed if the dam is replaced.

“If we lose that dam we would not have

any water storage,” mayor Doug Roll said. “The public safety is

paramount.”

The Council met with Morrison-Maierle

representatives during a special meeting to look at the available

options for the dam.

Engineers presented a number of

alternatives including rehabilitating the dam, replacing the dam

and finding a new water source for the city.

Rehabilitating the dam calls for

anchoring a new concrete veneer to the downstream face of the dam.

However, that fix is only expected to last about 25 years and then

the city would have to replace the dam. Morrison-Maierle is

discouraging this alternative because it would likely cost about

$1.9 million for the rehab and another $4 to $5 million to replace

the dam.

When it comes to replacing the dam on

Flower Creek, the city has two options. It could build a thin arch

structure for roughly $4.4 million or construct a roller-compacted

concrete dam, similar to Libby Dam, for about $5.6 million. Both

types of dams will last about 75 to 100 years before needing

maintenance.

Which type of dam is best would

ultimately be determined after studying the canyon walls. The

ultimate location of the dam would also have to be decided.

“Ideally we would find a site down

stream and demo the old dam,” said Ryan Jones with

Morrison-Maierle.

Replacing the dam would mean the city

will have to remove the current dam and perform environmental

restoration of the area. Further survey of the site is needed to

determine that cost.

Morrison-Maierle also looked at the

possibility of using other areas for water sources. Several options

were quickly ruled out. The water aquifer in the city is

contaminated. Pulling water from another creek, such as Parmenter

or Big Cherry, would require storage to meet the water needs of the

city essentially forcing the construction of a dam. Enough storage

tanks to serve the city would cost about $15 million.

The most viable alternative water

source is the Kootenai River. That option would use a water intake

and pump station at the river and piping water to the city’s water

treatment plant.

However, this option is cost

prohibitive with an estimated cost of $7.5 million. This option

comes with a number of expenses including the cost to modify the

water treatment plant to treat the river water, the cost to build

water lines to the treatment plant and the cost of electricity to

run the pump, which is estimated at a minimum of $200,000 per

year.

Inspections and core sample testing of

the dam have revealed that the dam is in need of replacement. Much

of the dam has considerable cracking and permeability along the

construction joints. The Montana Department of Natural Resources

and Conservation will not likely renew the city’s operating permit

in 2015 if a solution is not found. Flower Creek Dam is the city’s

sole water source.

The City Council Thursday seemed to

favor replacing the dam.

Councilmember Robin Benson said she

didn’t want to spend money on a dam that is leaking.

“I think the city needs to take care of

it now,” she said.

Mayor Doug Roll reiterated his feeling

that the city needs to protect its citizens from harm.

“The unknown risks are too great on

this,” he said. “We’re not going to sit here and say it might fall

down and it might not.”

Water needs

Flower Creek Dam is the city’s sole

source for drinking water.

The dam stores about 220-acre feet of

water. The city only needs of minimum of 50-acre feet to serve its

customers.

“There’s more than adequate storage,”

Jones said. “It far exceeds what the city needs for the next 20

years.”

Based on population figures, Lincoln

County is expected to grow at a rate of about .50 percent per year

over the 20 years. The water system usage should grow at a similar

rate.

Flower Creek should provide an adequate

source of water for the city through 2030.

Safety concerns

A number of issues have been raised

with the safety of Flower Creek Dam until a solution can be found.

One estimate is that if the dam does collapse water would move

through the canyon at a depth of up to 13 feet. It would most

likely flood the city center in up to 5 feet of water.

Local emergency response agencies have

been meeting to better prepare for the possibility that the dam

could collapse since the first test results were released.

Jones said one alternative is to lower

the water level of the reservoir to below 50 acre-feet safety

threshold. This would allow the city time to continue to operate

the dam. This would likely result in water use restrictions.

“It’s not a long term solution,” but it

would give the city some time to find a solution, Jones said.

The city is also working to install an

early warning system on the dam, which would alert officials if the

dam fails.

Funding

The city has petitioned the Governor’s

office for funding and has asked Montana’s Congressional delegation

for assistance.

A request has been made to the Governor

for $100,000 to install the early warning system on the dam.

Funding assistance could come from

Flathead Electric Co-op. FEC has been looking for green power

sources to invest in. The city could install a hydroelectric power

generation system at the new dam and sell the electricity to

FEC.

Jones recommended the city continue to

seek out funding sources even before work begins on the

project.

“You know you’re going to have to

secure funding over the next four years,” he said. “I can’t imagine

a scenario where you’re going to find 100 percent funding for your

project.”

Timeline

The city does not have a lot of time to

decide on a solution. Implementation of the project will require

coordination between the city, engineering and financial

consultants, the DNRC and other funding agencies.

Morrison-Maierle recommends the city

begin field investigation of the dam site this May. Design work

would begin in October and would likely continue through October

2012.

This puts the city on track for bidding

the project in January 2013 with construction completed in October

2013.