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Bertha tunnels past the 4,000 foot mark under Seattle

Ever since she restarted, Bertha has been moving forward without many problems

Fingers crossed but the days of problems for Bertha the tunnel boring machine seem to be over. Yesterday, she crossed the 4,000-foot mark along her 9,270-foot journey.

Bertha’s cutterhead is roughly 165 feet below First Avenue as it approaches Union Street. STP crews will keep moving along the avenue until they hit Stewart Street, at which point they’ll continue mining north while First Avenue veers west. She’ll keep that course until she emerges close to Seattle Center.

Per WSDOT, crews are seeing “little to no movement” in the mixture of clay, sand and gravel beneath downtown that Bertha is moving through. Good news. The less the ground Seattle’s skyscrapers are built on moves, the better.

Bertha is also closing in on Zone 6 of her journey. WSDOT and STP has identified ten zones along her path and she will have finished Zone 5 in about a month. Zone 6 includes a trip past Pike Place Market, though it’s doubtful she’ll have time to stop and shop.

Aug. 22 project update: Bertha passes the 4,000-foot mark [WSDOT]

Tracking Bertha, the SR 99 tunneling machine [WSDOT]