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A week after tunnel-boring machine Bertha overheated during a restart attempt, contractors have not submitted a plan to resume drilling.

The state Department of Transportation (DOT) has stopped making public statements, while its engineers, a special expert panel, contractor Seattle Tunnel Partners (STP) and drill manufacturer Hitachi-Zosen troubleshoot the Highway 99 project.

Bertha has drilled only 36 days, or 1,023 feet, since the 9,270-foot bore from Sodo to South Lake Union began July 30.

Last month, DOT Secretary Lynn Peterson told state senators she’s had concerns for months about how Bertha was running, well before operators shut it down Dec. 6. Peterson asked STP in mid-January for a strategy to resume drilling and regain lost time.

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“Lynn has not received the plan yet from the contractors, but we know they’re working with the experts now to develop a plan,” her spokesman, Lars Erickson, said Thursday.

DOT staff are trying to produce an update by Monday. Meanwhile, state officials aren’t answering some basic questions, such as whether any moving parts are damaged. Hitachi-Zosen, which built the $80 million machine, declined an interview request Thursday, citing a nondisclosure pact with STP.

Thursday marked two months since the shutdown, when Bertha abruptly slowed its forward pace and failed to grab dirt. After a long inspection of the front end, the machine overheated while traveling 4 feet during tests Jan. 28 and 29.

The DOT hasn’t released a roster or work orders for its expert team, which is led by Colin Lawrence of Hatch Mott McDonald, a national engineering firm.

A week ago, state managers said temperatures spiked to 140 degrees near the rotary cutter, or about 1½ times the standard, during last week’s test runs. A similar heat spike happened in early December.

“It would be a heat-sensor reading that’s associated with the moving and the spinning of the cutterhead, so in the chamber essentially, there is heat in the chamber that’s above what it should be,” DOT program administrator Todd Trepanier said in an interview last Friday.

The front of the boring machine includes a sealed chamber where incoming soil and water mix before entering the conveyor system.

An 11-day inspection found steel, rock and plastic next to the cutter, but no huge boulders or objects blocking the path, along the waterfront at South Main Street.

The lack of obstacles raises new questions: Are the internal parts in good order, are modifications needed to the front end or would operational changes help, such as changes in speed, or to lubricants injected into the soil?

By now, the drill should have just passed beneath the Alaskan Way Viaduct, to reach the 1,850 foot mark by Feb 18, a contractor schedule says.

The four-lane, deep bore tunnel, funded by gas tax and tolls, is scheduled to open by the end of 2015.

It will replace the earthquake-vulnerable viaduct, giving the city of Seattle a chance to create a quieter, parklike central waterfront.

Mike Lindblom: 206-515-5631 or On Twitter @mikelindblom

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