30 July 2012

Boardman River Dams Ready to Fall

 Story first reported from Traverse City Record Eagle

TRAVERSE CITY — Finally, after seven years, local Boardman River dam removal project leaders have a $2.9 million price tag and construction contract for dismantling the first of three Boardman River dams.

The Boardman River Implementation Team this week approved the general contractor/project management contract with AMEC Engineering & Infrastructure to remove the Brown Bridge Dam powerhouse, restore the river to its historic channel and reseed exposed bottomlands and construction areas.

The bulk of the contract, about $2.5 million, will go to Molon Excavating of Traverse City and its subcontractors for deconstruction, dredging, sediment management, restoration and re-seeding over an estimated 20 weeks. If work is not finished by Dec. 19, the project will be completed in the spring. 

Deconstruction cannot begin until the Michigan Department of Environmental Quality issues a permit, expected possibly early next week, Sroonian said. It will take about a week after the permit is approved to start.

Molon first will build a temporary "de-watering" structure to slowly drain the remaining 22 vertical feet of water in Brown Bridge Pond. The city's permit request seeks a flow rate of 1-foot-per-day to manage sediment, a major focus of the project. 

Sediment will be captured in traps as the water recedes. The MDEQ will set the rate of flow. 

The dam blocked the natural flow of river sediment for 90 years and created a sand delta at the north end of the former pond. 

About 250,000 cubic yards of spoils, a quantity that would fill 25,000 dump trucks with 10-yard beds, will be dredged during stream restoration in the upper impoundment. All of the spoils will remain on site in upland areas, according to information included in the city's permit request. Another 3,100 cubic feet of material will be dredged in late summer to install a temporary water-control structure upstream from the dam. 

The powerhouse foundation, buried under five feet of soil, will remain as will part of the earthen embankment, which will be graded and sloped. The river will be 55 feet wide in that section, Sroonian, AMEC’s senior principal engineer said.

The contract is the culmination of years of planning, feasibility studies, and engineering designs that started in 2005, after Traverse City Light & Power announced it would shut down the three hydroelectric dams. The announcement led to a study and a recommendation from the U.S. Army Corp of Engineers that the three dams be removed and Union Street Dam be reconstructed.

Brown Bridge, built in 1921, is the first of three dams scheduled to be taken out over the next three years. It is owned by Traverse City. Boardman and Sabin dams are owned by Grand Traverse County. The Army Corps is handling their removal. 

AMEC selected Molon from a field of 14 companies. Once completed, the dam removal project will restore 18 miles of cold-water river flowing into Lake Michigan and reconnect 160 miles of river and tributaries to Lake Michigan.

It is the state's largest-ever river restoration project and is believed by project leaders to one of the most comprehensive dam removal and restoration projects undertaken in the United States.

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