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Summer 2014

Bertha's Rescue Shaft

The Blue Begins Drilling

Malcolm has been awarded the support of excavation contract to drill the rescue shaft for Bertha, the world's largest Tunnel Boring Machine (TBM). Bertha has stopped all forward progress after just 1,000-ft of mining the new SR99 transportation tunnel currently being built below downtown Seattle, Washington. The stalled TBM is currently 80-ft below the surface.

After vetting all possible repair/rescue methods, Seattle Tunnel Partners decided that accessing Bertha with a vertical shaft provides the best approach to gain access to the cutter-head and facilitate repairs. Due to the limited surface area above the tunnel alignment and physical constraints bound by existing infrastructure, the dimensions of the otherwise symmetrical shaft are heavily impacted requiring special considerations for design, layout, and water control processes. The final design for the rescue shaft requires the drilling a series of secant piles with a varying diameters ranging from 3-ft to 10-ft. The secant piles will overlap two 1,000-ft long walls constructed out of 5-ft dia. non-accessible shafts that Malcolm originally installed to support the initial TBM launch. The existing shafts, with depths ranging from 75 to 138-ft were installed to protect the existing sea-wall and control the below sea-level ground conditions. Jet grouting and dewatering wells will also be constructed to control water.

"Rescuing a one-of-a-kind TBM requires a one-of-a-kind access shaft." said Clint McFarlane, project superintendent, Malcolm. "We're happy to be working with STP and WSDOT to help get Bertha back on track and moving forward." Malcolm's crews and equipment have mobilized from their regional office in Kent, WA and will work around the clock to expedite completion of this time critical project.

The rescue operation is scheduled to be completed by March 2015 allowing Bertha to continue her journey.

For more information please contact Malcolm's Project Superintendent at [email protected].

High Rise Construction in San Francisco
Malcolm Successfully Sinks San Francisco's Deepest Shafts

Malcolm has successfully completed the installation of 44 deep foundation shafts for the new 181 Fremont Street, a new 800-ft, 55 Story building in San Francisco. The office high-rise will become the second tallest building in San Francisco. The building sits on landfill where the bay used to encroach and called for the implementation of shafts averaging 262-ft deep with each 5 to 6-ft in diameter to support the building's foundation. To date the shafts for 181 Fremont are the deepest on record for San Francisco.

The most challenging part of project so far involved the design and setup of the 140-ft by 140-ft job site. The required equipment for the project included a 180 ton crane, a BAUR BG46 drill rig, 7 Baker 21,000 gallon open tanks (each measuring 8.5-ft wide by 30-ft long), and the all the necessary tools and ancillary machines. To create additional storage, the Malcolm team erected scaffolding over the Baker tanks.

"Logistics were critical for this project." commented Eleazar Sotelo, Malcolm's Project Manager. "The 262-ft cages for the shafts were delivered in three 72-ft sections during the evening when traffic was at a minimum. The timing was critical to keep the project on schedule."

Malcolm is under contract with Level 10 Construction to provide drilling, shoring with CSM, excavation and internal bracing, and foundation services. Now that the shafts are finished the Malcolm team will move into excavation.

For More information contact Malcolm's Project Manager at [email protected].

SR 4 Update

Soil Mixing for Very Large Shafts in Dune Sands

State Route 4 Interchange Improvement Project near San Francisco is currently under construction and will improve traffic flow through Contra Costa County's major transportation corridor. Malcolm, under contract with RGW is currently helping the Contra Costa Transportation Authority (CCTA) in their freeway widening effort by installing a series of 8 and 13 foot diameter drilled shafts over 110 feet deep for the foundation of three new fly-over structures. A few of the foundation shafts are precariously close to active traffic requiring complex project coordination with the CCTA. Before shaft drilling could commence, Malcolm installed CMP casings to depth of 60 feet; an impressive sight for commuters. The location of all three bridge foundations involves working with very dry and loose overburden material and the implementation of a uniquely designed 15 feet in diameter support ring to stabilize the 13 foot diameter drilled foundation shafts. In addition, single point soil mixing to a depth of 40 feet was used to stabilize dune sand material and minimize the potential for catastrophic ground failure close to active traffic.

"The SR4 widening project is not a typical project and requires complex solutions in respect to safety and ground control," commented David Walker, Malcolm's Project Manager.

For more information about the project contact Malcolm's Project Manager at [email protected].