[M II A II R II K]

Southwest light-rail construction work tunnels through tight quarters in Minneapolis

http://www.startribune.com/construct...nel/566978052/

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- Construction is often a noisy business, but building a light-rail tunnel in a dense urban area — and near freight-train operations — can be downright challenging. Add to the mix: Some neighbors who are, at best, wary of the $2 billion Southwest light-rail project that will pass through several of Minneapolis' most-desirable neighborhoods. --- The 14.5-mile light-rail line — the most-expensive public works project in state history — will connect downtown Minneapolis to Eden Prairie. The Kenilworth tunnel will run northeast of West Lake Street, pass underneath Cedar Lake Parkway and return above ground just south of the channel connecting Lake of the Isles and Cedar Lake. Light-rail trains will then travel over the channel on a new bridge.

- The construction method being used to build the tunnel involves Japanese equipment pressing (as opposed to pounding or vibrating) vertical steel sheet piles into the ground to create an interlocking wall that will serve as the framework for the concrete tunnel. "This is a pretty specialized piece of equipment," said construction director Brian Runzel at the job site on Monday. As he spoke, an auger loosened a small pile of steaming molasses-colored earth, making way for the 63-foot steel sheet pile to be lowered into the ground. The process was relatively quiet, except for the whir of a crane needed to lift and position the sheet piles. But mistakes occurred early on, infuriating some neighbors. A booming vibrating pile driver was used Nov. 15, causing damage to some property and prompting alarm, according to residents.

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