Seattle Tunnel Partners and WSDOT are moving forward with the plans to excavate a 120 foot deep shaft to repair the Bertha Tunnel Boring Machine. Unfortunately, there are archaeological issues since the project team did not clear the area where the shaft will be excavated. A series of 4-inch boreholes 20 to 40 feet deep (I wonder what drilling method, sonic?) will be performed under the supervision of the archaeologists to look for culturally significant items. The top of Bertha sits approximately 60 feet below grade at this point, below the historical fill used to fill in the waterfront. [Source: More info at WSDOT. Image: Raiders of the Lost Ark (1981) – Illustrated Reference]
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12 Miles of Tunnels for D.C. Sewer
In Washington D.C., the D.C. Water and Sewer Authority (D.C. WASA) finalized a lont-term plan in 2002 aimed at reducing combined sewer outfalls into the Potomac River and its tributary, the Anacostia River. A major portion of this plan is a $2.2 Billion (US) deep tunnel program to handle excess stormwater flows and prevent the combined sewage from being discharged into the environment. Read on for a map and more info. (Photo of Anacostia River, by D.C. WASA)