Traverse City Record-Eagle

Archive: Tuesday

October 16, 2012

Engineer 'regrets' dam breach

TRAVERSE CITY — A lead engineer on the Brown Bridge Dam removal expressed regret Monday for a breach that caused flooding to Boardman River properties.

The company she works for is committed to repairing damage that resulted from a pond swiftly emptying into the river earlier this month, she said. To date, Grand Traverse County's Office of Emergency Management has received 53 property damage claims related to the flood.

"We regret what's occurred," said Sandra Sroonian, a senior principal engineer with AMEC, the engineering firm working on the dam removal. "We want to get (flooded homeowners) back in their homes so they can continue their lives.

"It's unfortunate this occurred — the ultimate goal is to make things right no matter what the cause."

On Oct. 6, AMEC and a local company, Molon Excavating, initiated the slow drawdown of the Brown Bridge Pond through a device called a "dewatering structure." Built adjacent to the dam, the structure was supposed to slowly drain the pond over a period of weeks.

Instead, the entire pond rushed into the river in a few hours, raising the water level five feet and swamping at least 53 properties.

Sroonian declined to speculate on the cause of the incident. She did confirm AMEC originally planned to draw down the pond primarily using the existing dam structure. However, AMEC and the Boardman River Dams Implementation Team subsequently agreed to rely on an alternate dewatering structure design proposed by Molon that saved the project more than $100,000, she said.

"Their option was less expensive," Sroonian said.

It is unclear if the project's failure was due to a design flaw, an engineering error or construction mishap. She said it's too early to assign blame.

"A lot of individuals and entities wants to know (a cause), including AMEC," Sroonian said. "If I was to tell you something, it would be speculation. We don't have enough information yet."

Sroonian also said officials are trying to determine if an old water channel constructed in the 1920s could have played a role in the failure. A Record-Eagle news article from March 30, 1922, reported on the construction of a "new channel" that diverted water underneath the power house at the Brown Bridge Dam.

"The plans do show a diversion channel "¦ it does show that," Sroonian said. "I don't have any information on how that diversion channel was built. It's something we are looking at."

The Brown Bridge Dam is one of three scheduled for removal on the Boardman River.

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